use std::io::ErrorKind;
use std::path::Path;
use std::process::Stdio;
use std::time::Duration;
use std::time::Instant;

#[cfg(windows)]
use codex_utils_pty::JobObject;
use tokio::io::AsyncWriteExt;
use tokio::process::Command;
use tokio::time::timeout;
use tracing::Span;

use super::CommandShell;
use super::ConfiguredHandler;
use super::dispatcher::hook_event_name_label;
use super::dispatcher::hook_execution_mode_label;
use super::dispatcher::hook_handler_type_label;
use super::dispatcher::hook_scope_label;
use super::dispatcher::hook_source_label;
use super::dispatcher::scope_for_event;
use crate::output_spill::HookOutputSpiller;
use codex_protocol::protocol::HookExecutionMode;
use codex_protocol::protocol::HookHandlerType;

/// Owns the shell and output spiller shared by a session's command hooks.
#[derive(Clone)]
pub(crate) struct CommandHookRuntime {
    shell: CommandShell,
    output_spiller: HookOutputSpiller,
}

impl CommandHookRuntime {
    pub(crate) fn new(shell: CommandShell) -> Self {
        Self {
            shell,
            output_spiller: HookOutputSpiller::new(),
        }
    }

    pub(crate) fn output_spiller(&self) -> &HookOutputSpiller {
        &self.output_spiller
    }
}

#[derive(Debug)]
pub(crate) struct CommandRunResult {
    pub started_at: i64,
    pub completed_at: i64,
    pub duration_ms: i64,
    pub exit_code: Option<i32>,
    pub stdout: String,
    pub stderr: String,
    pub error: Option<String>,
}

#[tracing::instrument(
    name = "codex.hooks.command",
    level = "trace",
    skip_all,
    fields(
        hook.event_name = hook_event_name_label(handler.event_name),
        hook.handler_type = hook_handler_type_label(HookHandlerType::Command),
        hook.execution_mode = hook_execution_mode_label(HookExecutionMode::Sync),
        hook.scope = hook_scope_label(scope_for_event(handler.event_name)),
        hook.source = hook_source_label(handler.source),
        hook.display_order = handler.display_order,
        hook.configured_order = configured_order,
        hook.timeout_sec = handler.timeout_sec,
        hook.command_outcome = tracing::field::Empty,
    )
)]
pub(crate) async fn run_command(
    runtime: &CommandHookRuntime,
    handler: &ConfiguredHandler,
    configured_order: usize,
    input_json: &str,
    cwd: &Path,
) -> CommandRunResult {
    let started_at = chrono::Utc::now().timestamp();
    let started = Instant::now();

    let mut command = build_command(&runtime.shell, handler);
    command
        .current_dir(cwd)
        .stdin(Stdio::piped())
        .stdout(Stdio::piped())
        .stderr(Stdio::piped())
        .kill_on_drop(true);

    #[cfg(unix)]
    command.process_group(0);

    #[cfg(windows)]
    let mut process_tree_job = JobObject::create().ok();
    #[cfg(windows)]
    let child = match process_tree_job.as_ref() {
        Some(job) => match job.spawn_contained(&mut command) {
            Ok(child) => Ok(child),
            Err(_) => {
                process_tree_job = None;
                command.creation_flags(0);
                command.spawn()
            }
        },
        None => command.spawn(),
    };
    #[cfg(not(windows))]
    let child = command.spawn();

    let mut child = match child {
        Ok(child) => child,
        Err(err) => {
            return finish_command_run(
                started_at,
                started,
                CommandRunCompletion {
                    exit_code: None,
                    stdout: String::new(),
                    stderr: String::new(),
                    error: Some(err.to_string()),
                    outcome: "spawn_error",
                },
            );
        }
    };

    let mut process_tree_guard = ProcessTreeGuard {
        process_id: child.id(),
        #[cfg(windows)]
        job: process_tree_job,
    };

    if let Some(mut stdin) = child.stdin.take()
        && let Err(err) = stdin.write_all(input_json.as_bytes()).await
        && err.kind() != ErrorKind::BrokenPipe
    {
        let _ = child.kill().await;
        return finish_command_run(
            started_at,
            started,
            CommandRunCompletion {
                exit_code: None,
                stdout: String::new(),
                stderr: String::new(),
                error: Some(format!("failed to write hook stdin: {err}")),
                outcome: "stdin_error",
            },
        );
    }

    let timeout_duration = Duration::from_secs(handler.timeout_sec);
    match timeout(timeout_duration, child.wait_with_output()).await {
        Ok(Ok(output)) => {
            // Successfully completed hooks may intentionally leave detached helpers running.
            #[cfg(windows)]
            if let Some(job) = process_tree_guard.job.as_ref() {
                let _ = job.preserve_descendants();
            }
            process_tree_guard.process_id = None;
            finish_command_run(
                started_at,
                started,
                CommandRunCompletion {
                    exit_code: output.status.code(),
                    stdout: String::from_utf8_lossy(&output.stdout).to_string(),
                    stderr: String::from_utf8_lossy(&output.stderr).to_string(),
                    error: None,
                    outcome: "completed",
                },
            )
        }
        Ok(Err(err)) => finish_command_run(
            started_at,
            started,
            CommandRunCompletion {
                exit_code: None,
                stdout: String::new(),
                stderr: String::new(),
                error: Some(err.to_string()),
                outcome: "wait_error",
            },
        ),
        Err(_) => finish_command_run(
            started_at,
            started,
            CommandRunCompletion {
                exit_code: None,
                stdout: String::new(),
                stderr: String::new(),
                error: Some(format!("hook timed out after {}s", handler.timeout_sec)),
                outcome: "timeout",
            },
        ),
    }
}

// Needed only until command hooks move to the exec server, which owns process-tree cleanup.
struct ProcessTreeGuard {
    process_id: Option<u32>,
    #[cfg(windows)]
    job: Option<JobObject>,
}

impl Drop for ProcessTreeGuard {
    fn drop(&mut self) {
        let Some(process_id) = self.process_id else {
            return;
        };

        #[cfg(unix)]
        {
            let _ = codex_utils_pty::process_group::kill_process_group(process_id);
        }

        #[cfg(windows)]
        {
            if let Some(job) = self.job.as_ref() {
                let _ = job.terminate();
            } else {
                let _ = std::process::Command::new("taskkill")
                    .args(["/PID", &process_id.to_string(), "/T", "/F"])
                    .stdin(Stdio::null())
                    .stdout(Stdio::null())
                    .stderr(Stdio::null())
                    .spawn();
            }
        }
    }
}

struct CommandRunCompletion {
    exit_code: Option<i32>,
    stdout: String,
    stderr: String,
    error: Option<String>,
    outcome: &'static str,
}

fn finish_command_run(
    started_at: i64,
    started: Instant,
    completion: CommandRunCompletion,
) -> CommandRunResult {
    Span::current().record("hook.command_outcome", completion.outcome);
    CommandRunResult {
        started_at,
        completed_at: chrono::Utc::now().timestamp(),
        duration_ms: started.elapsed().as_millis().try_into().unwrap_or(i64::MAX),
        exit_code: completion.exit_code,
        stdout: completion.stdout,
        stderr: completion.stderr,
        error: completion.error,
    }
}

fn build_command(shell: &CommandShell, handler: &ConfiguredHandler) -> Command {
    let mut command = if shell.program.is_empty() {
        default_shell_command()
    } else {
        Command::new(&shell.program)
    };
    if shell.program.is_empty() {
        #[cfg(windows)]
        command.raw_arg(format!(r#""{}""#, handler.command));

        #[cfg(not(windows))]
        command.arg(&handler.command);
    } else {
        command.args(&shell.args);

        #[cfg(windows)]
        if shell.args.iter().any(|arg| arg.eq_ignore_ascii_case("/c")) {
            command.raw_arg(format!(r#""{}""#, handler.command));
        } else {
            command.arg(&handler.command);
        }

        #[cfg(not(windows))]
        command.arg(&handler.command);
    }
    command.envs(&handler.env);
    command
}

fn default_shell_command() -> Command {
    #[cfg(windows)]
    {
        let comspec = std::env::var("COMSPEC").unwrap_or_else(|_| "cmd.exe".to_string());
        let mut command = Command::new(comspec);
        command.arg("/C");
        command
    }

    #[cfg(not(windows))]
    {
        let shell = std::env::var("SHELL").unwrap_or_else(|_| "/bin/sh".to_string());
        let mut command = Command::new(shell);
        command.arg("-lc");
        command
    }
}

#[cfg(test)]
#[path = "command_runner_tests.rs"]
mod tests;