use crate::query::MAX_ROWS;
use crate::sql::starts_with_executable_sql_keyword;
use crate::types::{
    ColumnInfo, DatabaseInfo, ForeignKeyInfo, IndexInfo, LinkedServerInfo, QueryResult, TableInfo, TriggerInfo,
};
use futures::{FutureExt, TryStreamExt};
use rust_decimal::Decimal;
use std::future::Future;
use std::panic::AssertUnwindSafe;
use std::time::{Duration, Instant};
use tiberius::{AuthMethod, Client, ColumnData, Config, FromSql, QueryItem, QueryStream, SqlBrowser};
use tokio::net::TcpStream;
use tokio_util::compat::{Compat, TokioAsyncWriteCompatExt};

pub type SqlServerClient = Client<Compat<TcpStream>>;
const SIMPLE_QUERY_MODULE_KEYWORDS: &[&str] = &["FUNCTION", "PROC", "PROCEDURE", "TRIGGER", "VIEW"];

#[derive(Debug, PartialEq, Eq)]
struct SqlServerEndpoint<'a> {
    host: &'a str,
    instance_name: Option<&'a str>,
}

fn sqlserver_endpoint(host: &str) -> SqlServerEndpoint<'_> {
    if let Some((server, instance)) = host.split_once('\\') {
        if !server.trim().is_empty() && !instance.trim().is_empty() {
            return SqlServerEndpoint { host: server.trim(), instance_name: Some(instance.trim()) };
        }
    }

    SqlServerEndpoint { host: host.trim(), instance_name: None }
}

fn query_result_row_limit(max_rows: Option<usize>) -> usize {
    max_rows.unwrap_or(MAX_ROWS).max(1)
}

pub async fn connect(
    host: &str,
    port: u16,
    user: &str,
    pass: &str,
    database: Option<&str>,
    timeout: Duration,
) -> Result<SqlServerClient, String> {
    match try_connect(host, port, user, pass, database, true, timeout).await {
        Ok(client) => Ok(client),
        Err(_) => try_connect(host, port, user, pass, database, false, timeout).await,
    }
}

async fn try_connect(
    host: &str,
    port: u16,
    user: &str,
    pass: &str,
    database: Option<&str>,
    use_encryption: bool,
    timeout: Duration,
) -> Result<SqlServerClient, String> {
    let mut config = Config::new();
    let endpoint = sqlserver_endpoint(host);
    config.host(endpoint.host);
    if let Some(instance_name) = endpoint.instance_name {
        config.instance_name(instance_name);
    } else {
        config.port(port);
    }
    config.authentication(AuthMethod::sql_server(user, pass));
    if let Some(db) = database {
        config.database(db);
    }
    config.trust_cert();
    if !use_encryption {
        config.encryption(tiberius::EncryptionLevel::NotSupported);
    }

    let tcp = if endpoint.instance_name.is_some() {
        tokio::time::timeout(timeout, TcpStream::connect_named(&config))
            .await
            .map_err(|_| format!("SQL Server connection timed out ({}s)", timeout.as_secs()))?
            .map_err(|e| format!("SQL Server connection failed: {e}"))?
    } else {
        tokio::time::timeout(timeout, TcpStream::connect(config.get_addr()))
            .await
            .map_err(|_| format!("SQL Server connection timed out ({}s)", timeout.as_secs()))?
            .map_err(|e| format!("SQL Server connection failed: {e}"))?
    };
    tokio::time::timeout(timeout, Client::connect(config, tcp.compat_write()))
        .await
        .map_err(|_| format!("SQL Server handshake timed out ({}s)", timeout.as_secs()))?
        .map_err(|e| format!("SQL Server connection failed: {e}"))
}

fn row_to_json(row: &tiberius::Row) -> Vec<serde_json::Value> {
    row.cells().map(|(_, cell)| sqlserver_cell_to_json(cell)).collect()
}

fn columns_from_metadata(metadata: &tiberius::ResultMetadata) -> Vec<String> {
    metadata.columns().iter().map(|c| c.name().to_string()).collect()
}

/// Map a tiberius column to a user-facing type name for the result-grid header.
/// Uses the TDS column-type debug name lowercased; good enough for display, with
/// no risk of mismatching the enum variants across tiberius versions.
fn sqlserver_column_type_name(column: &tiberius::Column) -> String {
    format!("{:?}", column.column_type()).to_lowercase()
}

fn column_types_from_metadata(metadata: &tiberius::ResultMetadata) -> Vec<String> {
    metadata.columns().iter().map(sqlserver_column_type_name).collect()
}

async fn collect_first_result_limited(
    mut stream: QueryStream<'_>,
    start: Instant,
    max_rows: Option<usize>,
) -> Result<QueryResult, String> {
    let row_limit = query_result_row_limit(max_rows);
    let mut columns: Vec<String> = vec![];
    let mut column_types: Vec<String> = vec![];
    let mut rows: Vec<Vec<serde_json::Value>> = Vec::new();
    let mut truncated = false;

    while let Some(item) = stream.try_next().await.map_err(|e| e.to_string())? {
        match item {
            QueryItem::Metadata(metadata) if metadata.result_index() == 0 => {
                columns = columns_from_metadata(&metadata);
                column_types = column_types_from_metadata(&metadata);
            }
            QueryItem::Metadata(_) => {}
            QueryItem::Row(row) if row.result_index() == 0 => {
                if rows.len() < row_limit {
                    rows.push(row_to_json(&row));
                } else {
                    truncated = true;
                }
            }
            QueryItem::Row(_) => {}
        }
    }

    Ok(QueryResult {
        columns,
        column_types,
        column_sortables: vec![],
        rows,
        affected_rows: 0,
        execution_time_ms: start.elapsed().as_millis(),
        truncated,
        session_id: None,
        has_more: false,
    })
}

struct SqlServerResultSet {
    columns: Vec<String>,
    column_types: Vec<String>,
    rows: Vec<Vec<serde_json::Value>>,
    truncated: bool,
}

#[derive(Debug, Clone, PartialEq, Eq)]
struct SqlServerDescribedColumn {
    name: Option<String>,
    system_type_name: Option<String>,
    user_type_schema: Option<String>,
    user_type_name: Option<String>,
}

async fn sqlserver_driver_result<T, E, F>(future: F) -> Result<T, String>
where
    F: Future<Output = Result<T, E>>,
    E: ToString,
{
    match AssertUnwindSafe(future).catch_unwind().await {
        Ok(result) => result.map_err(|e| e.to_string()),
        Err(_) => {
            Err("SQL Server driver could not decode this result set. Unsupported columns may need to be cast to text."
                .to_string())
        }
    }
}

async fn describe_sqlserver_result_set(
    client: &mut SqlServerClient,
    sql: &str,
) -> Result<Vec<SqlServerDescribedColumn>, String> {
    let describe_sql = "\
        SELECT name, system_type_name, user_type_schema, user_type_name \
        FROM sys.dm_exec_describe_first_result_set(@P1, NULL, 0) \
        WHERE error_number IS NULL AND is_hidden = 0 \
        ORDER BY column_ordinal";
    let stream = sqlserver_driver_result(client.query(describe_sql, &[&sql])).await?;
    let rows = sqlserver_driver_result(stream.into_first_result()).await?;

    Ok(rows
        .iter()
        .map(|row| SqlServerDescribedColumn {
            name: row.try_get::<&str, _>(0).ok().flatten().map(str::to_string),
            system_type_name: row.try_get::<&str, _>(1).ok().flatten().map(str::to_string),
            user_type_schema: row.try_get::<&str, _>(2).ok().flatten().map(str::to_string),
            user_type_name: row.try_get::<&str, _>(3).ok().flatten().map(str::to_string),
        })
        .collect())
}

async fn spatial_safe_sqlserver_query(client: &mut SqlServerClient, sql: &str) -> Result<Option<String>, String> {
    if !is_single_sqlserver_select(sql) {
        return Ok(None);
    }
    let columns = describe_sqlserver_result_set(client, sql).await?;
    Ok(build_spatial_safe_sqlserver_query(sql, &columns))
}

fn build_spatial_safe_sqlserver_query(sql: &str, columns: &[SqlServerDescribedColumn]) -> Option<String> {
    if columns.is_empty() || !columns.iter().any(is_sqlserver_spatial_column) {
        return None;
    }
    let statement = normalized_sqlserver_select_statement(sql)?;
    let source_alias = quote_sqlserver_identifier("dbx_spatial_source");
    let source_columns = (0..columns.len()).map(sqlserver_source_column_name).collect::<Vec<_>>();
    let source_alias_list =
        source_columns.iter().map(|name| quote_sqlserver_identifier(name)).collect::<Vec<_>>().join(", ");
    let select_list = columns
        .iter()
        .enumerate()
        .map(|(index, column)| {
            let output_name = sqlserver_output_column_name(column, index);
            let quoted_output = quote_sqlserver_identifier(&output_name);
            let source_column = quote_sqlserver_identifier(&source_columns[index]);
            let value_ref = format!("{source_alias}.{source_column}");
            if is_sqlserver_spatial_column(column) {
                format!("{quoted_output} = CASE WHEN {value_ref} IS NULL THEN NULL ELSE {value_ref}.STAsText() END")
            } else {
                format!("{quoted_output} = {value_ref}")
            }
        })
        .collect::<Vec<_>>()
        .join(", ");

    Some(format!("SELECT {select_list} FROM ({statement}) AS {source_alias}({source_alias_list})"))
}

fn is_sqlserver_spatial_column(column: &SqlServerDescribedColumn) -> bool {
    [&column.system_type_name, &column.user_type_name].into_iter().flatten().any(|name| {
        let normalized = name.trim().trim_matches(['[', ']']).to_ascii_lowercase();
        normalized == "geometry"
            || normalized == "geography"
            || normalized.ends_with(".geometry")
            || normalized.ends_with(".geography")
    })
}

fn normalized_sqlserver_select_statement(sql: &str) -> Option<String> {
    let statement = trim_sqlserver_statement(sql);
    let trimmed = statement.trim_start();
    if trimmed.is_empty() || !trimmed.get(..6).is_some_and(|prefix| prefix.eq_ignore_ascii_case("SELECT")) {
        return None;
    }
    if has_top_level_select_into(trimmed) {
        return None;
    }

    // Strip trailing ORDER BY so the statement can be used as a derived table
    // subquery. SQL Server requires TOP / OFFSET / FOR XML alongside ORDER BY
    // in subqueries, none of which are version-safe across 2008–2022.
    let mut statement = trimmed.to_string();
    let tokens = top_level_sqlserver_tokens(&statement);
    for index in (0..tokens.len().saturating_sub(1)).rev() {
        if tokens[index].text == "ORDER" && tokens.get(index + 1).is_some_and(|token| token.text == "BY") {
            statement.truncate(tokens[index].start);
            statement = statement.trim_end().to_string();
            break;
        }
    }
    Some(statement)
}

fn trim_sqlserver_statement(sql: &str) -> String {
    let mut statement = sql.trim();
    while let Some(stripped) = statement.strip_suffix(';') {
        statement = stripped.trim_end();
    }
    statement.to_string()
}

fn is_single_sqlserver_select(sql: &str) -> bool {
    let statements = crate::sql::split_sql_statements(sql);
    if statements.len() != 1 {
        return false;
    }
    let statement = statements[0].trim_start();
    statement.get(..6).is_some_and(|prefix| prefix.eq_ignore_ascii_case("SELECT"))
}

fn sqlserver_source_column_name(index: usize) -> String {
    format!("dbx_col_{}", index + 1)
}

fn sqlserver_output_column_name(column: &SqlServerDescribedColumn, index: usize) -> String {
    column
        .name
        .as_deref()
        .map(str::trim)
        .filter(|name| !name.is_empty())
        .map(str::to_string)
        .unwrap_or_else(|| format!("column_{}", index + 1))
}

fn quote_sqlserver_identifier(identifier: &str) -> String {
    format!("[{}]", identifier.replace(']', "]]"))
}

#[derive(Debug, Clone, PartialEq, Eq)]
struct SqlServerToken {
    text: String,
    start: usize,
}

fn top_level_sqlserver_tokens(sql: &str) -> Vec<SqlServerToken> {
    let mut tokens = Vec::new();
    let mut i = 0;
    let mut depth = 0usize;

    while i < sql.len() {
        let ch = next_char(sql, i);
        let next = next_char_at(sql, i + ch.len_utf8());

        if ch == '-' && next == Some('-') {
            i += 2;
            while i < sql.len() && next_char(sql, i) != '\n' {
                i += next_char(sql, i).len_utf8();
            }
            continue;
        }
        if ch == '/' && next == Some('*') {
            i += 2;
            while i < sql.len() {
                let current = next_char(sql, i);
                let following = next_char_at(sql, i + current.len_utf8());
                if current == '*' && following == Some('/') {
                    i += 2;
                    break;
                }
                i += current.len_utf8();
            }
            continue;
        }
        if matches!(ch, '\'' | '"') {
            i = skip_sqlserver_quoted(sql, i, ch);
            continue;
        }
        if ch == '[' {
            i = skip_sqlserver_bracket_identifier(sql, i);
            continue;
        }
        if ch == '(' {
            depth += 1;
            i += ch.len_utf8();
            continue;
        }
        if ch == ')' {
            depth = depth.saturating_sub(1);
            i += ch.len_utf8();
            continue;
        }
        if depth == 0 && is_sqlserver_token_start(ch) {
            let start = i;
            i += ch.len_utf8();
            while i < sql.len() && is_sqlserver_token_part(next_char(sql, i)) {
                i += next_char(sql, i).len_utf8();
            }
            tokens.push(SqlServerToken { text: sql[start..i].to_ascii_uppercase(), start });
            continue;
        }
        i += ch.len_utf8();
    }

    tokens
}

fn has_top_level_select_into(sql: &str) -> bool {
    let tokens = top_level_sqlserver_tokens(sql);
    let Some(select_index) = tokens.iter().position(|token| token.text == "SELECT") else {
        return false;
    };
    let from_index = tokens
        .iter()
        .enumerate()
        .find(|(index, token)| *index > select_index && token.text == "FROM")
        .map(|(index, _)| index)
        .unwrap_or(tokens.len());
    tokens[select_index + 1..from_index].iter().any(|token| token.text == "INTO")
}

fn skip_sqlserver_quoted(sql: &str, pos: usize, quote: char) -> usize {
    let mut i = pos + quote.len_utf8();
    while i < sql.len() {
        let ch = next_char(sql, i);
        let next = next_char_at(sql, i + ch.len_utf8());
        if ch == quote {
            if next == Some(quote) {
                i += ch.len_utf8() + quote.len_utf8();
                continue;
            }
            return i + ch.len_utf8();
        }
        i += ch.len_utf8();
    }
    sql.len()
}

fn skip_sqlserver_bracket_identifier(sql: &str, pos: usize) -> usize {
    let mut i = pos + 1;
    while i < sql.len() {
        let ch = next_char(sql, i);
        let next = next_char_at(sql, i + ch.len_utf8());
        if ch == ']' {
            if next == Some(']') {
                i += 2;
                continue;
            }
            return i + 1;
        }
        i += ch.len_utf8();
    }
    sql.len()
}

fn is_sqlserver_token_start(ch: char) -> bool {
    ch.is_ascii_alphabetic() || ch == '_'
}

fn is_sqlserver_token_part(ch: char) -> bool {
    ch.is_ascii_alphanumeric() || matches!(ch, '_' | '$' | '#')
}

fn next_char(sql: &str, index: usize) -> char {
    sql[index..].chars().next().unwrap_or('\0')
}

fn next_char_at(sql: &str, index: usize) -> Option<char> {
    if index >= sql.len() {
        None
    } else {
        sql[index..].chars().next()
    }
}

fn push_sqlserver_result_set(results: &mut Vec<QueryResult>, result: Option<SqlServerResultSet>, start: Instant) {
    if let Some(result) = result {
        if result.rows.is_empty() && result.columns.is_empty() {
            return;
        }
        results.push(QueryResult {
            columns: result.columns,
            column_types: result.column_types,
            column_sortables: vec![],
            rows: result.rows,
            affected_rows: 0,
            execution_time_ms: start.elapsed().as_millis(),
            truncated: result.truncated,
            session_id: None,
            has_more: false,
        });
    }
}

async fn collect_result_sets_limited(
    mut stream: QueryStream<'_>,
    start: Instant,
    max_rows: Option<usize>,
) -> Result<Vec<QueryResult>, String> {
    let row_limit = query_result_row_limit(max_rows);
    let mut results = Vec::new();
    let mut current: Option<SqlServerResultSet> = None;

    while let Some(item) = stream.try_next().await.map_err(|e| e.to_string())? {
        match item {
            QueryItem::Metadata(metadata) => {
                push_sqlserver_result_set(&mut results, current.take(), start);
                current = Some(SqlServerResultSet {
                    columns: columns_from_metadata(&metadata),
                    column_types: column_types_from_metadata(&metadata),
                    rows: Vec::new(),
                    truncated: false,
                });
            }
            QueryItem::Row(row) => {
                let result = current.get_or_insert_with(|| SqlServerResultSet {
                    columns: row.columns().iter().map(|c| c.name().to_string()).collect(),
                    column_types: row.columns().iter().map(sqlserver_column_type_name).collect(),
                    rows: Vec::new(),
                    truncated: false,
                });
                if result.rows.len() < row_limit {
                    result.rows.push(row_to_json(&row));
                } else {
                    result.truncated = true;
                }
            }
        }
    }

    push_sqlserver_result_set(&mut results, current, start);
    Ok(results)
}

fn sqlserver_cell_to_json(cell: &ColumnData<'static>) -> serde_json::Value {
    if let Ok(Some(v)) = <&str as FromSql>::from_sql(cell) {
        return serde_json::Value::String(v.to_string());
    }
    if let Ok(Some(v)) = <chrono::NaiveDateTime as FromSql>::from_sql(cell) {
        return serde_json::Value::String(v.to_string());
    }
    if let Ok(Some(v)) = <chrono::NaiveDate as FromSql>::from_sql(cell) {
        return serde_json::Value::String(v.to_string());
    }
    if let Ok(Some(v)) = <chrono::NaiveTime as FromSql>::from_sql(cell) {
        return serde_json::Value::String(v.to_string());
    }
    if let Ok(Some(v)) = <chrono::DateTime<chrono::FixedOffset> as FromSql>::from_sql(cell) {
        return serde_json::Value::String(v.to_rfc3339());
    }
    if let Ok(Some(v)) = <Decimal as FromSql>::from_sql(cell) {
        return serde_json::Value::String(v.to_string());
    }
    if let Ok(Some(v)) = <u8 as FromSql>::from_sql(cell) {
        return serde_json::Value::Number(v.into());
    }
    if let Ok(Some(v)) = <i16 as FromSql>::from_sql(cell) {
        return serde_json::Value::Number(v.into());
    }
    if let Ok(Some(v)) = <i32 as FromSql>::from_sql(cell) {
        return serde_json::Value::Number(v.into());
    }
    if let Ok(Some(v)) = <i64 as FromSql>::from_sql(cell) {
        return super::safe_i64_to_json(v);
    }
    if let Ok(Some(v)) = <f32 as FromSql>::from_sql(cell) {
        return serde_json::Number::from_f64(v as f64)
            .map(serde_json::Value::Number)
            .unwrap_or(serde_json::Value::Null);
    }
    if let Ok(Some(v)) = <f64 as FromSql>::from_sql(cell) {
        return serde_json::Number::from_f64(v).map(serde_json::Value::Number).unwrap_or(serde_json::Value::Null);
    }
    if let Ok(Some(v)) = <bool as FromSql>::from_sql(cell) {
        return serde_json::Value::Bool(v);
    }
    if let Ok(Some(v)) = <uuid::Uuid as FromSql>::from_sql(cell) {
        return serde_json::Value::String(v.to_string());
    }
    if let Ok(Some(v)) = <Vec<u8> as tiberius::FromSqlOwned>::from_sql_owned(cell.clone()) {
        return super::binary_value_to_json(&v);
    }
    serde_json::Value::Null
}

pub async fn list_databases(client: &mut SqlServerClient) -> Result<Vec<DatabaseInfo>, String> {
    let stream = client
        .query(
            "SELECT name \
             FROM sys.databases \
             WHERE state = 0 \
             ORDER BY name",
            &[],
        )
        .await
        .map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows.iter().map(|row| DatabaseInfo { name: row.get::<&str, _>(0).unwrap_or("").to_string() }).collect())
}

pub async fn test_connection(client: &mut SqlServerClient) -> Result<(), String> {
    let stream = client.simple_query("SELECT 1").await.map_err(|e| e.to_string())?;
    let _ = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(())
}

pub async fn list_linked_servers(client: &mut SqlServerClient) -> Result<Vec<LinkedServerInfo>, String> {
    let stream = client
        .query(
            "SELECT name, product, provider, data_source \
             FROM sys.servers \
             WHERE is_linked = 1 \
             ORDER BY name",
            &[],
        )
        .await
        .map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows
        .iter()
        .map(|row| LinkedServerInfo {
            name: row.get::<&str, _>(0).unwrap_or("").to_string(),
            product: row.get::<&str, _>(1).filter(|value| !value.trim().is_empty()).map(str::to_string),
            provider: row.get::<&str, _>(2).filter(|value| !value.trim().is_empty()).map(str::to_string),
            data_source: row.get::<&str, _>(3).filter(|value| !value.trim().is_empty()).map(str::to_string),
        })
        .filter(|server| !server.name.trim().is_empty())
        .collect())
}

pub async fn list_linked_server_catalogs(
    client: &mut SqlServerClient,
    server: &str,
) -> Result<Vec<DatabaseInfo>, String> {
    let stream = client.query("EXEC sp_catalogs @server_name = @P1", &[&server]).await.map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows
        .iter()
        .filter_map(|row| row.get::<&str, _>(0).map(str::trim).filter(|name| !name.is_empty()))
        .map(|name| DatabaseInfo { name: name.to_string() })
        .collect())
}

pub async fn list_linked_server_schemas(
    client: &mut SqlServerClient,
    server: &str,
    catalog: &str,
) -> Result<Vec<String>, String> {
    let tables = linked_server_table_rows(client, server, catalog, None, None).await?;
    let mut schemas = Vec::new();
    for table in tables {
        if let Some(schema) = table.schema.filter(|value| !value.trim().is_empty()) {
            if !schemas.iter().any(|existing: &String| existing.eq_ignore_ascii_case(&schema)) {
                schemas.push(schema);
            }
        }
    }
    schemas.sort_by_key(|schema| (if schema.eq_ignore_ascii_case("dbo") { 0 } else { 1 }, schema.to_lowercase()));
    Ok(schemas)
}

pub async fn list_linked_server_tables(
    client: &mut SqlServerClient,
    server: &str,
    catalog: &str,
    schema: &str,
    filter: Option<&str>,
    limit: Option<usize>,
    offset: Option<usize>,
) -> Result<Vec<TableInfo>, String> {
    let filter = filter.map(str::trim).filter(|value| !value.is_empty()).map(str::to_lowercase);
    let limit = limit.unwrap_or(usize::MAX);
    let offset = offset.unwrap_or(0);
    let rows = linked_server_table_rows(client, server, catalog, Some(schema), None).await?;
    Ok(rows
        .into_iter()
        .filter(|row| filter.as_ref().is_none_or(|value| row.name.to_lowercase().contains(value)))
        .skip(offset)
        .take(limit)
        .map(|row| TableInfo {
            name: row.name,
            table_type: normalize_linked_server_table_type(row.table_type.as_deref()),
            comment: row.comment,
            parent_schema: None,
            parent_name: None,
        })
        .collect())
}

pub async fn get_linked_server_columns(
    client: &mut SqlServerClient,
    server: &str,
    catalog: &str,
    schema: &str,
    table: &str,
) -> Result<Vec<ColumnInfo>, String> {
    let stream = client
        .query(
            "EXEC sp_columns_ex \
             @table_server = @P1, \
             @table_name = @P2, \
             @table_schema = @P3, \
             @table_catalog = @P4",
            &[&server, &table, &schema, &catalog],
        )
        .await
        .map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows
        .iter()
        .filter_map(|row| {
            let name = row.get::<&str, _>(3)?.trim();
            if name.is_empty() {
                return None;
            }
            let base_type = row.get::<&str, _>(5).unwrap_or("").trim();
            let column_size = linked_i32(row, 6);
            let numeric_scale = linked_i32(row, 8);
            let nullable = linked_i32(row, 10).unwrap_or(1) != 0;
            let data_type = linked_server_column_type(base_type, column_size, numeric_scale);
            Some(ColumnInfo {
                name: name.to_string(),
                data_type,
                is_nullable: nullable,
                column_default: row.get::<&str, _>(12).filter(|value| !value.trim().is_empty()).map(str::to_string),
                is_primary_key: false,
                extra: None,
                comment: row.get::<&str, _>(11).filter(|value| !value.trim().is_empty()).map(str::to_string),
                numeric_precision: column_size,
                numeric_scale,
                character_maximum_length: linked_i32(row, 15),
            })
        })
        .collect())
}

struct LinkedServerTableRow {
    schema: Option<String>,
    name: String,
    table_type: Option<String>,
    comment: Option<String>,
}

async fn linked_server_table_rows(
    client: &mut SqlServerClient,
    server: &str,
    catalog: &str,
    schema: Option<&str>,
    table_name: Option<&str>,
) -> Result<Vec<LinkedServerTableRow>, String> {
    let sql = format!(
        "EXEC sp_tables_ex \
         @table_server = {}, \
         @table_name = {}, \
         @table_schema = {}, \
         @table_catalog = {}, \
         @table_type = '''TABLE'',''VIEW''', \
         @fUsePattern = 0",
        sqlserver_nstring_literal(server),
        sqlserver_optional_nstring_literal(table_name),
        sqlserver_optional_nstring_literal(schema),
        sqlserver_nstring_literal(catalog),
    );
    let stream = client.query(sql.as_str(), &[]).await.map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows
        .iter()
        .filter_map(|row| {
            let name = row.get::<&str, _>(2)?.trim();
            if name.is_empty() {
                return None;
            }
            Some(LinkedServerTableRow {
                schema: row.get::<&str, _>(1).filter(|value| !value.trim().is_empty()).map(str::to_string),
                name: name.to_string(),
                table_type: row.get::<&str, _>(3).filter(|value| !value.trim().is_empty()).map(str::to_string),
                comment: row.get::<&str, _>(4).filter(|value| !value.trim().is_empty()).map(str::to_string),
            })
        })
        .collect())
}

fn sqlserver_optional_nstring_literal(value: Option<&str>) -> String {
    value.filter(|value| !value.trim().is_empty()).map(sqlserver_nstring_literal).unwrap_or_else(|| "NULL".to_string())
}

fn sqlserver_nstring_literal(value: &str) -> String {
    format!("N'{}'", value.replace('\'', "''"))
}

fn normalize_linked_server_table_type(value: Option<&str>) -> String {
    let upper = value.unwrap_or("TABLE").to_ascii_uppercase();
    if upper.contains("VIEW") {
        "VIEW".to_string()
    } else {
        "BASE TABLE".to_string()
    }
}

fn linked_server_column_type(base_type: &str, size: Option<i32>, scale: Option<i32>) -> String {
    let lower = base_type.to_ascii_lowercase();
    if matches!(lower.as_str(), "varchar" | "nvarchar" | "char" | "nchar" | "binary" | "varbinary") {
        if let Some(size) = size {
            if size > 0 {
                return format!("{base_type}({size})");
            }
        }
    }
    if matches!(lower.as_str(), "decimal" | "numeric") {
        if let (Some(size), Some(scale)) = (size, scale) {
            return format!("{base_type}({size},{scale})");
        }
    }
    base_type.to_string()
}

fn linked_i32(row: &tiberius::Row, index: usize) -> Option<i32> {
    row.try_get::<i32, _>(index).ok().flatten().or_else(|| row.try_get::<i16, _>(index).ok().flatten().map(i32::from))
}

pub async fn list_schemas(client: &mut SqlServerClient) -> Result<Vec<String>, String> {
    let stream = client
        .query(
            "SELECT s.name \
         FROM sys.schemas s \
         WHERE s.name NOT IN ('guest','INFORMATION_SCHEMA','sys') \
           AND EXISTS ( \
             SELECT 1 FROM sys.objects o \
             WHERE o.schema_id = s.schema_id \
               AND o.type IN ('U','V') \
               AND o.is_ms_shipped = 0 \
           ) \
         ORDER BY CASE WHEN s.name = 'dbo' THEN 0 ELSE 1 END, s.name",
            &[],
        )
        .await
        .map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows.iter().map(|row| row.get::<&str, _>(0).unwrap_or("").to_string()).collect())
}

pub async fn list_tables(
    client: &mut SqlServerClient,
    schema: &str,
    filter: Option<&str>,
    limit: Option<usize>,
    offset: Option<usize>,
) -> Result<Vec<TableInfo>, String> {
    let filter_clause = filter
        .filter(|value| !value.trim().is_empty())
        .map(|value| format!(" AND o.name LIKE '%{}%' ESCAPE '\\' ", escape_like_literal(value.trim())))
        .unwrap_or_default();
    let schema_escaped = schema.replace('\'', "''");
    let base_columns = "o.name, CASE WHEN o.type = 'V' THEN 'VIEW' ELSE 'BASE TABLE' END, ep.value AS TABLE_COMMENT";
    let base_from = "FROM sys.objects o \
         JOIN sys.schemas s ON s.schema_id = o.schema_id \
         OUTER APPLY (SELECT CAST(ep.value AS NVARCHAR(MAX)) AS value FROM sys.extended_properties ep \
           WHERE ep.major_id = o.object_id AND ep.minor_id = 0 AND ep.name = N'MS_Description') ep";
    let base_where =
        format!("WHERE s.name = '{schema_escaped}' AND o.type IN ('U','V') AND o.is_ms_shipped = 0 {filter_clause}");
    let order_by = "ORDER BY o.name";

    // Use SELECT TOP for broad SQL Server version compatibility.
    // OFFSET / FETCH NEXT is only available in SQL Server 2012+.
    let sql = match (limit, offset) {
        (Some(limit), Some(offset)) if offset > 0 => {
            let end = offset + limit.min(1000);
            format!(
                "SELECT * FROM (\
                 SELECT {base_columns}, ROW_NUMBER() OVER ({order_by}) AS __dbx_rn \
                 {base_from} {base_where}\
                 ) AS __dbx_page WHERE __dbx_rn > {offset} AND __dbx_rn <= {end} ORDER BY __dbx_rn"
            )
        }
        (Some(limit), _) => {
            format!("SELECT TOP ({}) {base_columns} {base_from} {base_where} {order_by}", limit.min(1000))
        }
        _ => {
            format!("SELECT {base_columns} {base_from} {base_where} {order_by}")
        }
    };
    let stream = client.query(&*sql, &[]).await.map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows
        .iter()
        .map(|row| TableInfo {
            name: row.get::<&str, _>(0).unwrap_or("").to_string(),
            table_type: row.get::<&str, _>(1).unwrap_or("BASE TABLE").to_string(),
            comment: row.get::<&str, _>(2).filter(|s: &&str| !s.is_empty()).map(|s: &str| s.to_string()),
            parent_schema: None,
            parent_name: None,
        })
        .collect())
}

fn escape_like_literal(value: &str) -> String {
    value.replace('\\', "\\\\").replace('\'', "''").replace('%', "\\%").replace('_', "\\_").replace('[', "\\[")
}

pub async fn list_objects(client: &mut SqlServerClient, schema: &str) -> Result<Vec<crate::types::ObjectInfo>, String> {
    let sql = sqlserver_list_objects_sql(schema);
    let stream = client.query(&*sql, &[]).await.map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows
        .iter()
        .map(|row| crate::types::ObjectInfo {
            name: row.get::<&str, _>(0).unwrap_or("").to_string(),
            object_type: row.get::<&str, _>(1).unwrap_or("TABLE").to_string(),
            schema: Some(schema.to_string()),
            comment: row.get::<&str, _>(4).filter(|s: &&str| !s.is_empty()).map(|s: &str| s.to_string()),
            created_at: row.get::<chrono::NaiveDateTime, _>(2).map(|value| value.to_string()),
            updated_at: row.get::<chrono::NaiveDateTime, _>(3).map(|value| value.to_string()),
            parent_schema: None,
            parent_name: None,
        })
        .collect())
}

fn sqlserver_list_objects_sql(schema: &str) -> String {
    let s = schema.replace('\'', "''");
    format!(
        "SELECT o.name, \
         CASE o.type \
           WHEN 'U' THEN 'TABLE' \
           WHEN 'V' THEN 'VIEW' \
           WHEN 'P' THEN 'PROCEDURE' \
           WHEN 'FN' THEN 'FUNCTION' \
           WHEN 'IF' THEN 'FUNCTION' \
           WHEN 'TF' THEN 'FUNCTION' \
           WHEN 'FS' THEN 'FUNCTION' \
           WHEN 'FT' THEN 'FUNCTION' \
           ELSE o.type_desc \
         END AS object_type, \
         o.create_date, \
         o.modify_date, \
         ep.value AS object_comment \
         FROM sys.objects o \
         JOIN sys.schemas s ON s.schema_id = o.schema_id \
         OUTER APPLY (SELECT CAST(ep.value AS NVARCHAR(MAX)) AS value FROM sys.extended_properties ep WHERE ep.major_id = o.object_id AND ep.minor_id = 0 AND ep.name = N'MS_Description') ep \
         WHERE s.name = '{s}' \
           AND o.type IN ('U','V','P','FN','IF','TF','FS','FT') \
           AND o.is_ms_shipped = 0 \
         ORDER BY CASE o.type \
           WHEN 'U' THEN 0 \
           WHEN 'V' THEN 1 \
           WHEN 'P' THEN 2 \
           ELSE 3 \
         END, o.name"
    )
}

pub async fn get_columns(client: &mut SqlServerClient, schema: &str, table: &str) -> Result<Vec<ColumnInfo>, String> {
    let sql = sqlserver_columns_sql(schema, table);
    let stream = client.query(&*sql, &[]).await.map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows
        .iter()
        .map(|row| {
            let base = row.get::<&str, _>(1).unwrap_or("").to_string();
            let max_len = row
                .try_get::<i32, _>(7)
                .ok()
                .flatten()
                .or_else(|| row.try_get::<i16, _>(7).ok().flatten().map(|v| v as i32))
                .or_else(|| row.try_get::<u8, _>(7).ok().flatten().map(|v| v as i32));
            let dt_prec = row
                .try_get::<i32, _>(8)
                .ok()
                .flatten()
                .or_else(|| row.try_get::<i16, _>(8).ok().flatten().map(|v| v as i32))
                .or_else(|| row.try_get::<u8, _>(8).ok().flatten().map(|v| v as i32));
            let num_prec = row
                .try_get::<i32, _>(5)
                .ok()
                .flatten()
                .or_else(|| row.try_get::<i16, _>(5).ok().flatten().map(|v| v as i32))
                .or_else(|| row.try_get::<u8, _>(5).ok().flatten().map(|v| v as i32));
            let num_scale = row
                .try_get::<i32, _>(6)
                .ok()
                .flatten()
                .or_else(|| row.try_get::<i16, _>(6).ok().flatten().map(|v| v as i32))
                .or_else(|| row.try_get::<u8, _>(6).ok().flatten().map(|v| v as i32));
            let data_type = match base.to_lowercase().as_str() {
                "varchar" => match max_len {
                    Some(-1) => "varchar(max)".to_string(),
                    Some(n) => format!("varchar({n})"),
                    None => "varchar".to_string(),
                },
                "nvarchar" => match max_len {
                    Some(-1) => "nvarchar(max)".to_string(),
                    Some(n) => format!("nvarchar({n})"),
                    None => "nvarchar".to_string(),
                },
                "varbinary" => match max_len {
                    Some(-1) => "varbinary(max)".to_string(),
                    Some(n) if n > 0 => format!("varbinary({n})"),
                    _ => "varbinary".to_string(),
                },
                "char" | "nchar" | "binary" => match max_len {
                    Some(n) if n > 0 => format!("{base}({n})"),
                    _ => base,
                },
                "decimal" | "numeric" => match (num_prec, num_scale) {
                    (Some(p), Some(s)) => format!("{base}({p},{s})"),
                    _ => base,
                },
                "datetime2" | "datetimeoffset" | "time" => match dt_prec {
                    Some(p) => format!("{base}({p})"),
                    _ => base,
                },
                _ => base,
            };
            ColumnInfo {
                name: row.get::<&str, _>(0).unwrap_or("").to_string(),
                data_type,
                is_nullable: row.get::<&str, _>(2).unwrap_or("NO") == "YES",
                column_default: row.get::<&str, _>(3).map(|s| s.to_string()),
                is_primary_key: row.get::<i32, _>(4).unwrap_or(0) == 1,
                extra: row.get::<&str, _>(9).filter(|s: &&str| !s.is_empty()).map(|s: &str| s.to_string()),
                comment: row.get::<&str, _>(10).filter(|s: &&str| !s.is_empty()).map(|s: &str| s.to_string()),
                numeric_precision: num_prec,
                numeric_scale: num_scale,
                character_maximum_length: max_len,
            }
        })
        .collect())
}

fn sqlserver_columns_sql(schema: &str, table: &str) -> String {
    let s = schema.replace('\'', "''");
    let t = table.replace('\'', "''");
    format!(
        "SELECT c.COLUMN_NAME, c.DATA_TYPE, c.IS_NULLABLE, c.COLUMN_DEFAULT, \
         CASE WHEN kcu.COLUMN_NAME IS NOT NULL THEN 1 ELSE 0 END AS IS_PK, \
         c.NUMERIC_PRECISION, c.NUMERIC_SCALE, c.CHARACTER_MAXIMUM_LENGTH, c.DATETIME_PRECISION, \
         ident.extra AS COLUMN_EXTRA, \
         ep.value AS COLUMN_COMMENT \
         FROM INFORMATION_SCHEMA.COLUMNS c \
         LEFT JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE kcu \
           ON c.TABLE_SCHEMA = kcu.TABLE_SCHEMA AND c.TABLE_NAME = kcu.TABLE_NAME AND c.COLUMN_NAME = kcu.COLUMN_NAME \
           AND kcu.CONSTRAINT_NAME IN (SELECT CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE = 'PRIMARY KEY' AND TABLE_SCHEMA = '{s}' AND TABLE_NAME = '{t}') \
         OUTER APPLY (SELECT 'identity(' + CONVERT(VARCHAR(38), ic.seed_value) + ',' + CONVERT(VARCHAR(38), ic.increment_value) + ')' AS extra FROM sys.identity_columns ic WHERE ic.object_id = OBJECT_ID(QUOTENAME('{s}') + '.' + QUOTENAME('{t}')) AND ic.name = c.COLUMN_NAME) ident \
         OUTER APPLY (SELECT CAST(ep.value AS NVARCHAR(MAX)) AS value FROM sys.extended_properties ep WHERE ep.major_id = OBJECT_ID(QUOTENAME('{s}') + '.' + QUOTENAME('{t}')) AND ep.minor_id = COLUMNPROPERTY(OBJECT_ID(QUOTENAME('{s}') + '.' + QUOTENAME('{t}')), c.COLUMN_NAME, 'ColumnId') AND ep.name = N'MS_Description') ep \
         WHERE c.TABLE_SCHEMA = '{s}' AND c.TABLE_NAME = '{t}' \
         ORDER BY c.ORDINAL_POSITION"
    )
}

pub async fn list_indexes(client: &mut SqlServerClient, schema: &str, table: &str) -> Result<Vec<IndexInfo>, String> {
    let sql = sqlserver_indexes_sql(schema, table);
    let stream = client.query(&*sql, &[]).await.map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows
        .iter()
        .map(|row| {
            let cols_str = row.get::<&str, _>(1).unwrap_or("");
            let inc_str = row.get::<&str, _>(5).unwrap_or("");
            IndexInfo {
                name: row.get::<&str, _>(0).unwrap_or("").to_string(),
                columns: cols_str.split(',').filter(|s| !s.is_empty()).map(|s| s.to_string()).collect(),
                is_unique: row.get::<bool, _>(2).unwrap_or(false),
                is_primary: row.get::<bool, _>(3).unwrap_or(false),
                filter: row.get::<&str, _>(6).map(|s| s.to_string()),
                index_type: row.get::<&str, _>(4).map(|s| s.to_string()),
                included_columns: if inc_str.is_empty() {
                    None
                } else {
                    Some(inc_str.split(',').map(|s| s.to_string()).collect())
                },
                comment: row.get::<&str, _>(7).filter(|s: &&str| !s.is_empty()).map(|s: &str| s.to_string()),
            }
        })
        .collect())
}

fn sqlserver_indexes_sql(schema: &str, table: &str) -> String {
    format!(
        "SELECT i.name, \
         STUFF((SELECT ',' + c2.name \
                FROM sys.index_columns ic2 \
                JOIN sys.columns c2 ON ic2.object_id = c2.object_id AND ic2.column_id = c2.column_id \
                WHERE ic2.object_id = i.object_id AND ic2.index_id = i.index_id AND ic2.is_included_column = 0 \
                ORDER BY ic2.key_ordinal \
                FOR XML PATH(''), TYPE).value('.', 'nvarchar(max)'), 1, 1, '') AS columns, \
         i.is_unique, i.is_primary_key, i.type_desc, \
         STUFF((SELECT ',' + c3.name \
                FROM sys.index_columns ic3 \
                JOIN sys.columns c3 ON ic3.object_id = c3.object_id AND ic3.column_id = c3.column_id \
                WHERE ic3.object_id = i.object_id AND ic3.index_id = i.index_id AND ic3.is_included_column = 1 \
                ORDER BY ic3.index_column_id \
                FOR XML PATH(''), TYPE).value('.', 'nvarchar(max)'), 1, 1, '') AS included_cols, \
         i.filter_definition, \
         ep.value AS index_comment \
         FROM sys.indexes i \
         OUTER APPLY (SELECT CAST(ep.value AS NVARCHAR(MAX)) AS value FROM sys.extended_properties ep WHERE ep.major_id = i.object_id AND ep.minor_id = i.index_id AND ep.name = N'MS_Description' AND ep.class = 7) ep \
         WHERE i.object_id = OBJECT_ID('{s}.{t}') AND i.name IS NOT NULL \
         ORDER BY i.name",
        s = schema.replace('\'', "''"),
        t = table.replace('\'', "''")
    )
}

pub async fn list_foreign_keys(
    client: &mut SqlServerClient,
    schema: &str,
    table: &str,
) -> Result<Vec<ForeignKeyInfo>, String> {
    let sql = format!(
        "SELECT fk.name, c.name, SCHEMA_NAME(rt.schema_id), rt.name, rc.name \
         FROM sys.foreign_keys fk \
         JOIN sys.foreign_key_columns fkc ON fk.object_id = fkc.constraint_object_id \
         JOIN sys.columns c ON fkc.parent_object_id = c.object_id AND fkc.parent_column_id = c.column_id \
         JOIN sys.tables rt ON fkc.referenced_object_id = rt.object_id \
         JOIN sys.columns rc ON fkc.referenced_object_id = rc.object_id AND fkc.referenced_column_id = rc.column_id \
         WHERE fk.parent_object_id = OBJECT_ID('{s}.{t}') \
         ORDER BY fk.name, fkc.constraint_column_id",
        s = schema.replace('\'', "''"),
        t = table.replace('\'', "''")
    );
    let stream = client.query(&*sql, &[]).await.map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows
        .iter()
        .map(|row| ForeignKeyInfo {
            name: row.get::<&str, _>(0).unwrap_or("").to_string(),
            column: row.get::<&str, _>(1).unwrap_or("").to_string(),
            ref_schema: Some(row.get::<&str, _>(2).unwrap_or("").to_string()),
            ref_table: row.get::<&str, _>(3).unwrap_or("").to_string(),
            ref_column: row.get::<&str, _>(4).unwrap_or("").to_string(),
            on_update: None,
            on_delete: None,
        })
        .collect())
}

pub async fn get_table_comment(
    client: &mut SqlServerClient,
    schema: &str,
    table: &str,
) -> Result<Option<String>, String> {
    let sql = sqlserver_table_comment_sql(schema, table);
    let stream = client.query(&*sql, &[]).await.map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows.first().and_then(|row| row.get::<&str, _>(0)).filter(|s| !s.is_empty()).map(|s| s.to_string()))
}

fn sqlserver_table_comment_sql(schema: &str, table: &str) -> String {
    let s = schema.replace('\'', "''");
    let t = table.replace('\'', "''");
    format!(
        "SELECT CAST(ep.value AS NVARCHAR(MAX)) \
         FROM sys.extended_properties ep \
         WHERE ep.major_id = OBJECT_ID(QUOTENAME('{s}') + '.' + QUOTENAME('{t}')) \
           AND ep.minor_id = 0 \
           AND ep.name = N'MS_Description'"
    )
}

pub async fn list_triggers(
    client: &mut SqlServerClient,
    schema: &str,
    table: &str,
) -> Result<Vec<TriggerInfo>, String> {
    let sql = format!(
        "SELECT t.name, te.type_desc, CASE WHEN t.is_instead_of_trigger = 1 THEN 'INSTEAD OF' ELSE 'AFTER' END \
         FROM sys.triggers t \
         JOIN sys.trigger_events te ON t.object_id = te.object_id \
         WHERE t.parent_id = OBJECT_ID('{s}.{t}') \
         ORDER BY t.name",
        s = schema.replace('\'', "''"),
        t = table.replace('\'', "''")
    );
    let stream = client.query(&*sql, &[]).await.map_err(|e| e.to_string())?;
    let rows = stream.into_first_result().await.map_err(|e| e.to_string())?;
    Ok(rows
        .iter()
        .map(|row| TriggerInfo {
            name: row.get::<&str, _>(0).unwrap_or("").to_string(),
            event: row.get::<&str, _>(1).unwrap_or("").to_string(),
            timing: row.get::<&str, _>(2).unwrap_or("AFTER").to_string(),
            statement: None,
        })
        .collect())
}

pub async fn execute_query(client: &mut SqlServerClient, sql: &str) -> Result<QueryResult, String> {
    execute_query_with_max_rows(client, sql, None).await
}

pub async fn execute_query_with_max_rows(
    client: &mut SqlServerClient,
    sql: &str,
    max_rows: Option<usize>,
) -> Result<QueryResult, String> {
    let start = Instant::now();

    if starts_with_executable_sql_keyword(sql, &["SELECT", "EXEC", "WITH", "TABLE"]) {
        let query_sql = match spatial_safe_sqlserver_query(client, sql).await {
            Ok(Some(sql)) => sql,
            Ok(None) | Err(_) => sql.to_string(),
        };
        let stream = sqlserver_driver_result(client.query(query_sql.as_str(), &[])).await?;
        sqlserver_driver_result(collect_first_result_limited(stream, start, max_rows)).await
    } else if requires_simple_query_batch(sql) || is_transaction_control(sql) {
        let stream = sqlserver_driver_result(client.simple_query(sql)).await?;
        let _ = sqlserver_driver_result(collect_result_sets_limited(stream, start, max_rows)).await?;
        Ok(QueryResult {
            columns: vec![],
            column_types: Vec::new(),
            column_sortables: vec![],
            rows: vec![],
            affected_rows: 0,
            execution_time_ms: start.elapsed().as_millis(),
            truncated: false,
            session_id: None,
            has_more: false,
        })
    } else {
        let result = sqlserver_driver_result(client.execute(sql, &[])).await?;
        Ok(QueryResult {
            columns: vec![],
            column_types: Vec::new(),
            column_sortables: vec![],
            rows: vec![],
            affected_rows: result.rows_affected().iter().sum::<u64>(),
            execution_time_ms: start.elapsed().as_millis(),
            truncated: false,
            session_id: None,
            has_more: false,
        })
    }
}

pub async fn execute_batch(client: &mut SqlServerClient, sql: &str) -> Result<Vec<QueryResult>, String> {
    execute_batch_with_max_rows(client, sql, None).await
}

pub async fn execute_batch_with_max_rows(
    client: &mut SqlServerClient,
    sql: &str,
    max_rows: Option<usize>,
) -> Result<Vec<QueryResult>, String> {
    let start = Instant::now();
    if is_single_sqlserver_select(sql) {
        if let Ok(Some(query_sql)) = spatial_safe_sqlserver_query(client, sql).await {
            let stream = sqlserver_driver_result(client.query(query_sql.as_str(), &[])).await?;
            return sqlserver_driver_result(collect_first_result_limited(stream, start, max_rows))
                .await
                .map(|result| vec![result]);
        }
    }
    let stream = sqlserver_driver_result(client.simple_query(sql)).await?;
    let mut results = sqlserver_driver_result(collect_result_sets_limited(stream, start, max_rows)).await?;

    if results.is_empty() {
        results.push(QueryResult {
            columns: vec![],
            column_types: Vec::new(),
            column_sortables: vec![],
            rows: vec![],
            affected_rows: 0,
            execution_time_ms: start.elapsed().as_millis(),
            truncated: false,
            session_id: None,
            has_more: false,
        });
    }

    Ok(results)
}

fn is_transaction_control(sql: &str) -> bool {
    let tokens = first_sql_tokens(sql, 2);
    if tokens.is_empty() {
        return false;
    }
    let first = &tokens[0];
    if first.eq_ignore_ascii_case("COMMIT") || first.eq_ignore_ascii_case("ROLLBACK") {
        return true;
    }
    if first.eq_ignore_ascii_case("BEGIN") {
        return tokens.get(1).is_some_and(|t| t.eq_ignore_ascii_case("TRANSACTION") || t.eq_ignore_ascii_case("TRAN"));
    }
    false
}

fn requires_simple_query_batch(sql: &str) -> bool {
    let tokens = first_sql_tokens(sql, 4);
    if tokens.len() >= 4
        && tokens[0].eq_ignore_ascii_case("CREATE")
        && tokens[1].eq_ignore_ascii_case("OR")
        && tokens[2].eq_ignore_ascii_case("ALTER")
    {
        return SIMPLE_QUERY_MODULE_KEYWORDS.iter().any(|keyword| tokens[3].eq_ignore_ascii_case(keyword));
    }

    if tokens.len() >= 2 && (tokens[0].eq_ignore_ascii_case("CREATE") || tokens[0].eq_ignore_ascii_case("ALTER")) {
        return SIMPLE_QUERY_MODULE_KEYWORDS.iter().any(|keyword| tokens[1].eq_ignore_ascii_case(keyword));
    }

    false
}

fn first_sql_tokens(sql: &str, limit: usize) -> Vec<String> {
    let bytes = sql.as_bytes();
    let mut tokens = Vec::new();
    let mut i = 0;

    while i < bytes.len() && tokens.len() < limit {
        while i < bytes.len() && bytes[i].is_ascii_whitespace() {
            i += 1;
        }

        if i + 1 < bytes.len() && bytes[i] == b'-' && bytes[i + 1] == b'-' {
            i += 2;
            while i < bytes.len() && bytes[i] != b'\n' {
                i += 1;
            }
            continue;
        }

        if i + 1 < bytes.len() && bytes[i] == b'/' && bytes[i + 1] == b'*' {
            i += 2;
            while i + 1 < bytes.len() && !(bytes[i] == b'*' && bytes[i + 1] == b'/') {
                i += 1;
            }
            i = (i + 2).min(bytes.len());
            continue;
        }

        let start = i;
        while i < bytes.len() && (bytes[i].is_ascii_alphanumeric() || bytes[i] == b'_') {
            i += 1;
        }

        if i > start {
            tokens.push(sql[start..i].to_string());
        } else {
            i += 1;
        }
    }

    tokens
}

#[cfg(test)]
mod tests {
    use super::{
        build_spatial_safe_sqlserver_query, is_sqlserver_spatial_column, requires_simple_query_batch,
        sqlserver_cell_to_json, sqlserver_columns_sql, sqlserver_indexes_sql, sqlserver_list_objects_sql,
        sqlserver_table_comment_sql, SqlServerDescribedColumn, SqlServerResultSet,
    };
    use chrono::NaiveDate;
    use std::time::Instant;
    use tiberius::{ColumnData, IntoSql};

    #[test]
    fn sqlserver_endpoint_splits_named_instance_hosts() {
        assert_eq!(
            super::sqlserver_endpoint(r"192.168.1.10\SQL2022"),
            super::SqlServerEndpoint { host: "192.168.1.10", instance_name: Some("SQL2022") }
        );
        assert_eq!(
            super::sqlserver_endpoint(r" db.example.com\SQLEXPRESS "),
            super::SqlServerEndpoint { host: "db.example.com", instance_name: Some("SQLEXPRESS") }
        );
    }

    #[test]
    fn sqlserver_endpoint_keeps_regular_hosts() {
        assert_eq!(
            super::sqlserver_endpoint("db.example.com"),
            super::SqlServerEndpoint { host: "db.example.com", instance_name: None }
        );
        assert_eq!(
            super::sqlserver_endpoint(r"db.example.com\"),
            super::SqlServerEndpoint { host: r"db.example.com\", instance_name: None }
        );
    }

    #[test]
    fn sqlserver_connect_uses_named_instance_resolution() {
        let source = include_str!("sqlserver.rs");
        let try_connect = source.split("async fn try_connect").nth(1).unwrap();
        let try_connect = try_connect.split("fn row_to_json").next().unwrap();
        assert!(try_connect.contains("connect_named(&config)"));
    }

    #[test]
    fn sqlserver_module_definitions_require_simple_query_batch() {
        assert!(requires_simple_query_batch("CREATE FUNCTION dbo.fn_demo() RETURNS INT AS BEGIN RETURN 1; END;"));
        assert!(requires_simple_query_batch("ALTER PROCEDURE dbo.usp_demo AS SELECT 1;"));
        assert!(requires_simple_query_batch("CREATE OR ALTER VIEW dbo.vw_demo AS SELECT 1 AS id;"));
        assert!(requires_simple_query_batch(
            "-- comment\nALTER TRIGGER dbo.tr_demo ON dbo.t AFTER INSERT AS SELECT 1;"
        ));
    }

    #[test]
    fn sqlserver_regular_ddl_can_use_execute() {
        assert!(!requires_simple_query_batch("ALTER TABLE dbo.t ADD name NVARCHAR(20);"));
        assert!(!requires_simple_query_batch("CREATE TABLE dbo.t(id INT);"));
        assert!(!requires_simple_query_batch("UPDATE dbo.t SET id = 1;"));
    }

    #[test]
    fn sqlserver_user_query_paths_do_not_collect_full_results_before_limiting() {
        let source = include_str!("sqlserver.rs");
        let execute_query = source.split("pub async fn execute_query").nth(1).unwrap();
        let execute_query = execute_query.split("pub async fn execute_batch").next().unwrap();
        assert!(!execute_query.contains("into_first_result"));

        let execute_batch = source.split("pub async fn execute_batch").nth(1).unwrap();
        let execute_batch = execute_batch.split("#[cfg(test)]").next().unwrap();
        assert!(!execute_batch.contains("into_results"));
    }

    #[test]
    fn sqlserver_index_metadata_sql_avoids_string_agg_for_older_compatibility_levels() {
        let sql = sqlserver_indexes_sql("dbo", "DF_Rule");

        assert!(!sql.contains("STRING_AGG"));
        assert!(sql.contains("FOR XML PATH"));
        assert!(sql.contains("OBJECT_ID('dbo.DF_Rule')"));
    }

    #[test]
    fn sqlserver_indexes_sql_includes_index_comment_via_extended_properties() {
        let sql = sqlserver_indexes_sql("dbo", "orders");

        assert!(sql.contains("sys.extended_properties ep"));
        assert!(sql.contains("ep.minor_id = i.index_id"));
        assert!(sql.contains("MS_Description"));
    }

    #[test]
    fn sqlserver_table_comment_sql_queries_extended_properties() {
        let sql = sqlserver_table_comment_sql("dbo", "users");

        assert!(sql.contains("sys.extended_properties ep"));
        assert!(sql.contains("ep.minor_id = 0"));
        assert!(sql.contains("MS_Description"));
        assert!(sql.contains("QUOTENAME('dbo')"));
        assert!(sql.contains("QUOTENAME('users')"));
    }

    #[test]
    fn sqlserver_metadata_sql_escapes_literals() {
        let columns_sql = sqlserver_columns_sql("d'bo", "t'able");
        let indexes_sql = sqlserver_indexes_sql("d'bo", "t'able");

        assert!(columns_sql.contains("TABLE_SCHEMA = 'd''bo'"));
        assert!(columns_sql.contains("TABLE_NAME = 't''able'"));
        assert!(columns_sql.contains("sys.identity_columns"));
        assert!(indexes_sql.contains("OBJECT_ID('d''bo.t''able')"));
    }

    #[test]
    fn sqlserver_list_objects_sql_includes_timestamps() {
        let sql = sqlserver_list_objects_sql("dbo");

        assert!(sql.contains("create_date"));
        assert!(sql.contains("modify_date"));
    }

    #[test]
    fn sqlserver_tinyint_cells_are_json_numbers() {
        assert_eq!(sqlserver_cell_to_json(&ColumnData::U8(Some(7))), serde_json::json!(7));
    }

    #[test]
    fn sqlserver_datetime2_cells_are_json_strings() {
        let datetime = NaiveDate::from_ymd_opt(2026, 5, 13).unwrap().and_hms_milli_opt(9, 8, 7, 123).unwrap();
        let cell: ColumnData<'static> = datetime.into_sql();

        assert_eq!(sqlserver_cell_to_json(&cell), serde_json::json!("2026-05-13 09:08:07.123"));
    }

    #[test]
    fn sqlserver_detects_geometry_result_columns() {
        assert!(is_sqlserver_spatial_column(&SqlServerDescribedColumn {
            name: Some("polygon".to_string()),
            system_type_name: Some("geometry".to_string()),
            user_type_schema: Some("sys".to_string()),
            user_type_name: Some("geometry".to_string()),
        }));
        assert!(is_sqlserver_spatial_column(&SqlServerDescribedColumn {
            name: Some("shape".to_string()),
            system_type_name: Some("geography".to_string()),
            user_type_schema: Some("sys".to_string()),
            user_type_name: Some("geography".to_string()),
        }));
        assert!(!is_sqlserver_spatial_column(&SqlServerDescribedColumn {
            name: Some("name".to_string()),
            system_type_name: Some("varchar(30)".to_string()),
            user_type_schema: None,
            user_type_name: None,
        }));
    }

    #[test]
    fn sqlserver_wraps_geometry_columns_as_text() {
        let rewritten = build_spatial_safe_sqlserver_query(
            "SELECT * FROM dbo.tLandPolygon;",
            &[
                SqlServerDescribedColumn {
                    name: Some("landId".to_string()),
                    system_type_name: Some("varchar(30)".to_string()),
                    user_type_schema: None,
                    user_type_name: None,
                },
                SqlServerDescribedColumn {
                    name: Some("polygon".to_string()),
                    system_type_name: Some("geometry".to_string()),
                    user_type_schema: Some("sys".to_string()),
                    user_type_name: Some("geometry".to_string()),
                },
            ],
        )
        .unwrap();

        assert_eq!(
            rewritten,
            "SELECT [landId] = [dbx_spatial_source].[dbx_col_1], [polygon] = CASE WHEN [dbx_spatial_source].[dbx_col_2] IS NULL THEN NULL ELSE [dbx_spatial_source].[dbx_col_2].STAsText() END FROM (SELECT * FROM dbo.tLandPolygon) AS [dbx_spatial_source]([dbx_col_1], [dbx_col_2])"
        );
    }

    #[test]
    fn sqlserver_does_not_wrap_non_spatial_columns() {
        assert_eq!(
            build_spatial_safe_sqlserver_query(
                "SELECT landId FROM dbo.tLandPolygon",
                &[SqlServerDescribedColumn {
                    name: Some("landId".to_string()),
                    system_type_name: Some("varchar(30)".to_string()),
                    user_type_schema: None,
                    user_type_name: None,
                }]
            ),
            None
        );
    }

    #[test]
    fn sqlserver_preserves_order_by_when_wrapping_geometry_columns() {
        let rewritten = build_spatial_safe_sqlserver_query(
            "SELECT landId, polygon FROM dbo.tLandPolygon ORDER BY landId DESC",
            &[
                SqlServerDescribedColumn {
                    name: Some("landId".to_string()),
                    system_type_name: Some("varchar(30)".to_string()),
                    user_type_schema: None,
                    user_type_name: None,
                },
                SqlServerDescribedColumn {
                    name: Some("polygon".to_string()),
                    system_type_name: Some("geometry".to_string()),
                    user_type_schema: Some("sys".to_string()),
                    user_type_name: Some("geometry".to_string()),
                },
            ],
        )
        .unwrap();

        // ORDER BY is stripped from the inner query so it can be used as a
        // derived table subquery across all SQL Server versions (2008–2022).
        assert!(!rewritten.contains("ORDER BY"));
        assert!(rewritten.contains("FROM dbo.tLandPolygon"));
        assert!(rewritten.contains(".STAsText()"));
    }

    #[test]
    fn sqlserver_keeps_empty_result_sets_when_metadata_exists() {
        let mut results = Vec::new();
        super::push_sqlserver_result_set(
            &mut results,
            Some(SqlServerResultSet {
                columns: vec!["id".to_string(), "name".to_string()],
                column_types: vec![],
                rows: vec![],
                truncated: false,
            }),
            Instant::now(),
        );

        assert_eq!(results.len(), 1);
        assert_eq!(results[0].columns, vec!["id".to_string(), "name".to_string()]);
        assert!(results[0].rows.is_empty());
    }

    #[test]
    fn sqlserver_drops_truly_empty_result_sets_without_metadata() {
        let mut results = Vec::new();
        super::push_sqlserver_result_set(
            &mut results,
            Some(SqlServerResultSet { columns: vec![], column_types: vec![], rows: vec![], truncated: false }),
            Instant::now(),
        );

        assert!(results.is_empty());
    }
}