use serde::{Deserialize, Serialize};

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct SqlFileRequest {
    pub execution_id: String,
    pub connection_id: String,
    pub database: String,
    pub file_path: String,
    pub continue_on_error: bool,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct SqlFilePreview {
    pub file_name: String,
    pub file_path: String,
    pub size_bytes: u64,
    pub preview: String,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub enum SqlFileStatus {
    Started,
    Running,
    StatementDone,
    StatementFailed,
    Done,
    Error,
    Cancelled,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct SqlFileProgress {
    pub execution_id: String,
    pub status: SqlFileStatus,
    pub statement_index: usize,
    pub success_count: usize,
    pub failure_count: usize,
    pub affected_rows: u64,
    pub elapsed_ms: u128,
    pub statement_summary: String,
    pub error: Option<String>,
}

#[derive(Default)]
pub struct SqlStatementSplitter {
    buffer: String,
    in_single_quote: bool,
    in_double_quote: bool,
    in_backtick: bool,
    in_line_comment: bool,
    in_block_comment: bool,
    dollar_quote_tag: Option<String>,
    previous: Option<char>,
}

impl SqlStatementSplitter {
    pub fn push_chunk(&mut self, chunk: &str) -> Vec<String> {
        let mut statements = Vec::new();
        let chars = chunk.chars().collect::<Vec<_>>();
        let mut i = 0;

        while i < chars.len() {
            if let Some(tag) = &self.dollar_quote_tag {
                let tag_chars = tag.chars().collect::<Vec<_>>();
                if starts_with_chars(&chars, i, &tag_chars) {
                    for tag_ch in &tag_chars {
                        self.buffer.push(*tag_ch);
                        self.previous = Some(*tag_ch);
                    }
                    i += tag_chars.len();
                    self.dollar_quote_tag = None;
                    continue;
                }

                let ch = chars[i];
                self.buffer.push(ch);
                self.previous = Some(ch);
                i += 1;
                continue;
            }

            let ch = chars[i];
            let next = chars.get(i + 1).copied();

            if self.in_line_comment {
                self.buffer.push(ch);
                if ch == '\n' {
                    self.in_line_comment = false;
                }
                self.previous = Some(ch);
                i += 1;
                continue;
            }

            if self.in_block_comment {
                self.buffer.push(ch);
                if self.previous == Some('*') && ch == '/' {
                    self.in_block_comment = false;
                }
                self.previous = Some(ch);
                i += 1;
                continue;
            }

            if !self.in_single_quote && !self.in_double_quote && !self.in_backtick {
                if self.previous == Some('-') && ch == '-' {
                    self.in_line_comment = true;
                    self.buffer.push(ch);
                    self.previous = Some(ch);
                    i += 1;
                    continue;
                }
                if self.previous == Some('/') && ch == '*' {
                    self.in_block_comment = true;
                    self.buffer.push(ch);
                    self.previous = Some(ch);
                    i += 1;
                    continue;
                }
                if ch == '-' && next == Some('-') {
                    self.in_line_comment = true;
                    self.buffer.push(ch);
                    self.previous = Some(ch);
                    i += 1;
                    continue;
                }
                if ch == '/' && next == Some('*') {
                    self.in_block_comment = true;
                    self.buffer.push(ch);
                    self.previous = Some(ch);
                    i += 1;
                    continue;
                }
                if let Some(tag) = dollar_quote_tag_at(&chars, i) {
                    for tag_ch in tag.chars() {
                        self.buffer.push(tag_ch);
                        self.previous = Some(tag_ch);
                    }
                    i += tag.chars().count();
                    self.dollar_quote_tag = Some(tag);
                    continue;
                }
            }

            match ch {
                '\'' if !self.in_double_quote && !self.in_backtick && self.previous != Some('\\') => {
                    self.in_single_quote = !self.in_single_quote;
                    self.buffer.push(ch);
                }
                '"' if !self.in_single_quote && !self.in_backtick && self.previous != Some('\\') => {
                    self.in_double_quote = !self.in_double_quote;
                    self.buffer.push(ch);
                }
                '`' if !self.in_single_quote && !self.in_double_quote => {
                    self.in_backtick = !self.in_backtick;
                    self.buffer.push(ch);
                }
                ';' if !self.in_single_quote && !self.in_double_quote && !self.in_backtick => {
                    self.push_current_statement(&mut statements);
                }
                _ => self.buffer.push(ch),
            }

            self.previous = Some(ch);
            i += 1;
        }

        statements
    }

    pub fn finish(mut self) -> Vec<String> {
        let mut statements = Vec::new();
        self.push_current_statement(&mut statements);
        statements
    }

    fn push_current_statement(&mut self, statements: &mut Vec<String>) {
        let statement = self.buffer.trim();
        if has_executable_sql(statement) {
            statements.push(statement.to_string());
        }
        self.buffer.clear();
        self.previous = None;
    }
}

pub fn split_sql_statements(sql: &str) -> Vec<String> {
    let mut splitter = SqlStatementSplitter::default();
    let mut statements = splitter.push_chunk(sql);
    statements.extend(splitter.finish());
    statements
}

pub fn statement_summary(statement: &str) -> String {
    const MAX_LEN: usize = 120;

    let collapsed = statement.split_whitespace().collect::<Vec<_>>().join(" ");
    if collapsed.chars().count() <= MAX_LEN {
        return collapsed;
    }

    collapsed.chars().take(MAX_LEN).collect()
}

fn starts_with_chars(chars: &[char], start: usize, needle: &[char]) -> bool {
    start + needle.len() <= chars.len() && chars[start..start + needle.len()] == *needle
}

fn dollar_quote_tag_at(chars: &[char], start: usize) -> Option<String> {
    if chars.get(start) != Some(&'$') {
        return None;
    }

    match chars.get(start + 1) {
        Some('$') => return Some("$$".to_string()),
        Some(ch) if ch.is_ascii_alphabetic() || *ch == '_' => {}
        _ => return None,
    }

    let mut end = start + 2;
    while let Some(ch) = chars.get(end) {
        if *ch == '$' {
            return Some(chars[start..=end].iter().collect());
        }
        if !ch.is_ascii_alphanumeric() && *ch != '_' {
            return None;
        }
        end += 1;
    }

    None
}

fn has_executable_sql(statement: &str) -> bool {
    let chars = statement.chars().collect::<Vec<_>>();
    let mut in_line_comment = false;
    let mut in_block_comment = false;
    let mut previous = None;
    let mut i = 0;

    while i < chars.len() {
        let ch = chars[i];
        let next = chars.get(i + 1).copied();

        if in_line_comment {
            if ch == '\n' {
                in_line_comment = false;
            }
            previous = Some(ch);
            i += 1;
            continue;
        }

        if in_block_comment {
            if previous == Some('*') && ch == '/' {
                in_block_comment = false;
            }
            previous = Some(ch);
            i += 1;
            continue;
        }

        if ch == '-' && next == Some('-') {
            in_line_comment = true;
            previous = Some(ch);
            i += 1;
            continue;
        }

        if ch == '/' && next == Some('*') {
            if is_mysql_executable_comment_start(&chars, i) {
                return true;
            }
            in_block_comment = true;
            previous = Some(ch);
            i += 1;
            continue;
        }

        if !ch.is_whitespace() {
            return true;
        }

        previous = Some(ch);
        i += 1;
    }

    false
}

fn is_mysql_executable_comment_start(chars: &[char], start: usize) -> bool {
    chars.get(start) == Some(&'/')
        && chars.get(start + 1) == Some(&'*')
        && (chars.get(start + 2) == Some(&'!')
            || (chars.get(start + 2) == Some(&'M') && chars.get(start + 3) == Some(&'!')))
}

#[cfg(test)]
fn split_sql_script(sql: &str) -> Result<Vec<String>, String> {
    Ok(split_sql_statements(sql))
}

#[cfg(test)]
mod tests {
    use super::{split_sql_script, SqlStatementSplitter};

    #[test]
    fn splits_semicolon_delimited_statements() {
        assert_eq!(
            split_sql_script("CREATE TABLE a(id int); INSERT INTO a VALUES (1);").unwrap(),
            vec!["CREATE TABLE a(id int)", "INSERT INTO a VALUES (1)"]
        );
    }

    #[test]
    fn ignores_semicolons_inside_quotes_and_comments() {
        let sql = "\
            INSERT INTO logs VALUES ('a;b', \"c;d\", `weird;name`);\n\
            -- comment ; ignored\n\
            /* block ; ignored */\n\
            SELECT 1;";
        assert_eq!(
            split_sql_script(sql).unwrap(),
            vec![
                "INSERT INTO logs VALUES ('a;b', \"c;d\", `weird;name`)",
                "-- comment ; ignored\n/* block ; ignored */\nSELECT 1",
            ]
        );
    }

    #[test]
    fn emits_trailing_statement_without_semicolon() {
        assert_eq!(
            split_sql_script("CREATE TABLE a(id int);\nINSERT INTO a VALUES (1)").unwrap(),
            vec!["CREATE TABLE a(id int)", "INSERT INTO a VALUES (1)"]
        );
    }

    #[test]
    fn line_comment_openers_can_span_chunks() {
        let mut splitter = SqlStatementSplitter::default();

        assert_eq!(splitter.push_chunk("SELECT 1; -"), vec!["SELECT 1"]);
        assert_eq!(splitter.push_chunk("- comment ; ignored\nSELECT 2;"), vec!["-- comment ; ignored\nSELECT 2"]);
        assert_eq!(splitter.finish(), Vec::<String>::new());
    }

    #[test]
    fn block_comment_openers_can_span_chunks() {
        let mut splitter = SqlStatementSplitter::default();

        assert_eq!(splitter.push_chunk("SELECT 1; /"), vec!["SELECT 1"]);
        assert_eq!(splitter.push_chunk("* comment ; ignored */\nSELECT 2;"), vec!["/* comment ; ignored */\nSELECT 2"]);
        assert_eq!(splitter.finish(), Vec::<String>::new());
    }

    #[test]
    fn skips_comment_only_tail_after_statement() {
        assert_eq!(
            split_sql_script("CREATE TABLE a(id int); -- done\n/* no more sql */").unwrap(),
            vec!["CREATE TABLE a(id int)"]
        );
    }

    #[test]
    fn keeps_postgres_dollar_quoted_function_body_together() {
        let sql = "\
            CREATE FUNCTION bump_counter()\n\
            RETURNS trigger AS $$\n\
            BEGIN\n\
              PERFORM 1;\n\
              RETURN NEW;\n\
            END;\n\
            $$ LANGUAGE plpgsql;\n\
            SELECT 1;";

        assert_eq!(
            split_sql_script(sql).unwrap(),
            vec![
                "CREATE FUNCTION bump_counter()\nRETURNS trigger AS $$\nBEGIN\nPERFORM 1;\nRETURN NEW;\nEND;\n$$ LANGUAGE plpgsql",
                "SELECT 1",
            ]
        );
    }

    #[test]
    fn keeps_mysql_executable_comments_as_statements() {
        assert_eq!(
            split_sql_script("/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;\nSELECT 1;",).unwrap(),
            vec!["/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */", "SELECT 1",]
        );
    }
}