//! Unified Exec: interactive process execution orchestrated with approvals + sandboxing.
//!
//! Responsibilities
//! - Manages interactive processes (create, reuse, buffer output with caps).
//! - Uses the shared ToolOrchestrator to handle approval, sandbox selection, and
//!   retry semantics in a single, descriptive flow.
//! - Spawns the PTY from a sandbox‑transformed `ExecEnv`; on sandbox denial,
//!   retries without sandbox when policy allows (no re‑prompt thanks to caching).
//! - Uses the shared `is_likely_sandbox_denied` heuristic to keep denial messages
//!   consistent with other exec paths.
//!
//! Flow at a glance (open process)
//! 1) Build a small request `{ command, cwd }`.
//! 2) Orchestrator: approval (bypass/cache/prompt) → select sandbox → run.
//! 3) Runtime: transform `CommandSpec` → `ExecEnv` → spawn PTY.
//! 4) If denial, orchestrator retries with `SandboxType::None`.
//! 5) Process handle is returned with streaming output + metadata.
//!
//! This keeps policy logic and user interaction centralized while the PTY/process
//! concerns remain isolated here. The implementation is split between:
//! - `process.rs`: PTY process lifecycle + output buffering.
//! - `process_manager.rs`: orchestration (approvals, sandboxing, reuse) and request handling.

use std::collections::HashMap;
use std::collections::HashSet;
use std::path::PathBuf;
use std::sync::Arc;
use std::time::Duration;

use rand::Rng;
use rand::rng;
use tokio::sync::Mutex;

use crate::codex::Session;
use crate::codex::TurnContext;
use crate::sandboxing::SandboxPermissions;

mod async_watcher;
mod errors;
mod head_tail_buffer;
mod process;
mod process_manager;

pub(crate) use errors::UnifiedExecError;
pub(crate) use process::UnifiedExecProcess;

pub(crate) const MIN_YIELD_TIME_MS: u64 = 250;
// Minimum yield time for an empty `write_stdin`.
pub(crate) const MIN_EMPTY_YIELD_TIME_MS: u64 = 5_000;
pub(crate) const MAX_YIELD_TIME_MS: u64 = 30_000;
pub(crate) const DEFAULT_MAX_OUTPUT_TOKENS: usize = 10_000;
pub(crate) const UNIFIED_EXEC_OUTPUT_MAX_BYTES: usize = 1024 * 1024; // 1 MiB
pub(crate) const UNIFIED_EXEC_OUTPUT_MAX_TOKENS: usize = UNIFIED_EXEC_OUTPUT_MAX_BYTES / 4;
pub(crate) const MAX_UNIFIED_EXEC_PROCESSES: usize = 64;

// Send a warning message to the models when it reaches this number of processes.
pub(crate) const WARNING_UNIFIED_EXEC_PROCESSES: usize = 60;

pub(crate) struct UnifiedExecContext {
    pub session: Arc<Session>,
    pub turn: Arc<TurnContext>,
    pub call_id: String,
}

impl UnifiedExecContext {
    pub fn new(session: Arc<Session>, turn: Arc<TurnContext>, call_id: String) -> Self {
        Self {
            session,
            turn,
            call_id,
        }
    }
}

#[derive(Debug)]
pub(crate) struct ExecCommandRequest {
    pub command: Vec<String>,
    pub process_id: String,
    pub yield_time_ms: u64,
    pub max_output_tokens: Option<usize>,
    pub workdir: Option<PathBuf>,
    pub tty: bool,
    pub sandbox_permissions: SandboxPermissions,
    pub justification: Option<String>,
}

#[derive(Debug)]
pub(crate) struct WriteStdinRequest<'a> {
    pub process_id: &'a str,
    pub input: &'a str,
    pub yield_time_ms: u64,
    pub max_output_tokens: Option<usize>,
}

#[derive(Debug, Clone, PartialEq)]
pub(crate) struct UnifiedExecResponse {
    pub event_call_id: String,
    pub chunk_id: String,
    pub wall_time: Duration,
    pub output: String,
    /// Raw bytes returned for this unified exec call before any truncation.
    pub raw_output: Vec<u8>,
    pub process_id: Option<String>,
    pub exit_code: Option<i32>,
    pub original_token_count: Option<usize>,
    pub session_command: Option<Vec<String>>,
}

#[derive(Default)]
pub(crate) struct ProcessStore {
    processes: HashMap<String, ProcessEntry>,
    reserved_process_ids: HashSet<String>,
}

impl ProcessStore {
    fn remove(&mut self, process_id: &str) -> Option<ProcessEntry> {
        self.reserved_process_ids.remove(process_id);
        self.processes.remove(process_id)
    }
}

pub(crate) struct UnifiedExecProcessManager {
    process_store: Mutex<ProcessStore>,
}

impl Default for UnifiedExecProcessManager {
    fn default() -> Self {
        Self {
            process_store: Mutex::new(ProcessStore::default()),
        }
    }
}

struct ProcessEntry {
    process: Arc<UnifiedExecProcess>,
    call_id: String,
    process_id: String,
    command: Vec<String>,
    tty: bool,
    last_used: tokio::time::Instant,
}

pub(crate) fn clamp_yield_time(yield_time_ms: u64) -> u64 {
    yield_time_ms.clamp(MIN_YIELD_TIME_MS, MAX_YIELD_TIME_MS)
}

pub(crate) fn resolve_max_tokens(max_tokens: Option<usize>) -> usize {
    max_tokens.unwrap_or(DEFAULT_MAX_OUTPUT_TOKENS)
}

pub(crate) fn generate_chunk_id() -> String {
    let mut rng = rng();
    (0..6)
        .map(|_| format!("{:x}", rng.random_range(0..16)))
        .collect()
}

#[cfg(test)]
#[cfg(unix)]
mod tests {
    use super::head_tail_buffer::HeadTailBuffer;
    use super::*;
    use crate::codex::Session;
    use crate::codex::TurnContext;
    use crate::codex::make_session_and_context;
    use crate::protocol::AskForApproval;
    use crate::protocol::SandboxPolicy;
    use crate::unified_exec::ExecCommandRequest;
    use crate::unified_exec::WriteStdinRequest;
    use core_test_support::skip_if_sandbox;
    use std::sync::Arc;
    use tokio::time::Duration;

    async fn test_session_and_turn() -> (Arc<Session>, Arc<TurnContext>) {
        let (session, mut turn) = make_session_and_context().await;
        turn.approval_policy = AskForApproval::Never;
        turn.sandbox_policy = SandboxPolicy::DangerFullAccess;
        (Arc::new(session), Arc::new(turn))
    }

    async fn exec_command(
        session: &Arc<Session>,
        turn: &Arc<TurnContext>,
        cmd: &str,
        yield_time_ms: u64,
    ) -> Result<UnifiedExecResponse, UnifiedExecError> {
        let context =
            UnifiedExecContext::new(Arc::clone(session), Arc::clone(turn), "call".to_string());
        let process_id = session
            .services
            .unified_exec_manager
            .allocate_process_id()
            .await;

        session
            .services
            .unified_exec_manager
            .exec_command(
                ExecCommandRequest {
                    command: vec!["bash".to_string(), "-lc".to_string(), cmd.to_string()],
                    process_id,
                    yield_time_ms,
                    max_output_tokens: None,
                    workdir: None,
                    tty: true,
                    sandbox_permissions: SandboxPermissions::UseDefault,
                    justification: None,
                },
                &context,
            )
            .await
    }

    async fn write_stdin(
        session: &Arc<Session>,
        process_id: &str,
        input: &str,
        yield_time_ms: u64,
    ) -> Result<UnifiedExecResponse, UnifiedExecError> {
        session
            .services
            .unified_exec_manager
            .write_stdin(WriteStdinRequest {
                process_id,
                input,
                yield_time_ms,
                max_output_tokens: None,
            })
            .await
    }

    #[test]
    fn push_chunk_preserves_prefix_and_suffix() {
        let mut buffer = HeadTailBuffer::default();
        buffer.push_chunk(vec![b'a'; UNIFIED_EXEC_OUTPUT_MAX_BYTES]);
        buffer.push_chunk(vec![b'b']);
        buffer.push_chunk(vec![b'c']);

        assert_eq!(buffer.retained_bytes(), UNIFIED_EXEC_OUTPUT_MAX_BYTES);
        let snapshot = buffer.snapshot_chunks();

        let first = snapshot.first().expect("expected at least one chunk");
        assert_eq!(first.first(), Some(&b'a'));
        assert!(snapshot.iter().any(|chunk| chunk.as_slice() == b"b"));
        assert_eq!(
            snapshot
                .last()
                .expect("expected at least one chunk")
                .as_slice(),
            b"c"
        );
    }

    #[test]
    fn head_tail_buffer_default_preserves_prefix_and_suffix() {
        let mut buffer = HeadTailBuffer::default();
        buffer.push_chunk(vec![b'a'; UNIFIED_EXEC_OUTPUT_MAX_BYTES]);
        buffer.push_chunk(b"bc".to_vec());

        let rendered = buffer.to_bytes();
        assert_eq!(rendered.first(), Some(&b'a'));
        assert!(rendered.ends_with(b"bc"));
    }

    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
    async fn unified_exec_persists_across_requests() -> anyhow::Result<()> {
        skip_if_sandbox!(Ok(()));

        let (session, turn) = test_session_and_turn().await;

        let open_shell = exec_command(&session, &turn, "bash -i", 2_500).await?;
        let process_id = open_shell
            .process_id
            .as_ref()
            .expect("expected process_id")
            .as_str();

        write_stdin(
            &session,
            process_id,
            "export CODEX_INTERACTIVE_SHELL_VAR=codex\n",
            2_500,
        )
        .await?;

        let out_2 = write_stdin(
            &session,
            process_id,
            "echo $CODEX_INTERACTIVE_SHELL_VAR\n",
            2_500,
        )
        .await?;
        assert!(
            out_2.output.contains("codex"),
            "expected environment variable output"
        );

        Ok(())
    }

    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
    async fn multi_unified_exec_sessions() -> anyhow::Result<()> {
        skip_if_sandbox!(Ok(()));

        let (session, turn) = test_session_and_turn().await;

        let shell_a = exec_command(&session, &turn, "bash -i", 2_500).await?;
        let session_a = shell_a
            .process_id
            .as_ref()
            .expect("expected process id")
            .clone();

        write_stdin(
            &session,
            session_a.as_str(),
            "export CODEX_INTERACTIVE_SHELL_VAR=codex\n",
            2_500,
        )
        .await?;

        let out_2 =
            exec_command(&session, &turn, "echo $CODEX_INTERACTIVE_SHELL_VAR", 2_500).await?;
        tokio::time::sleep(Duration::from_secs(2)).await;
        assert!(
            out_2.process_id.is_none(),
            "short command should not report a process id if it exits quickly"
        );
        assert!(
            !out_2.output.contains("codex"),
            "short command should run in a fresh shell"
        );

        let out_3 = write_stdin(
            &session,
            shell_a
                .process_id
                .as_ref()
                .expect("expected process id")
                .as_str(),
            "echo $CODEX_INTERACTIVE_SHELL_VAR\n",
            2_500,
        )
        .await?;
        assert!(
            out_3.output.contains("codex"),
            "session should preserve state"
        );

        Ok(())
    }

    #[tokio::test]
    async fn unified_exec_timeouts() -> anyhow::Result<()> {
        skip_if_sandbox!(Ok(()));

        const TEST_VAR_VALUE: &str = "unified_exec_var_123";

        let (session, turn) = test_session_and_turn().await;

        let open_shell = exec_command(&session, &turn, "bash -i", 2_500).await?;
        let process_id = open_shell
            .process_id
            .as_ref()
            .expect("expected process id")
            .as_str();

        write_stdin(
            &session,
            process_id,
            format!("export CODEX_INTERACTIVE_SHELL_VAR={TEST_VAR_VALUE}\n").as_str(),
            2_500,
        )
        .await?;

        let out_2 = write_stdin(
            &session,
            process_id,
            "sleep 5 && echo $CODEX_INTERACTIVE_SHELL_VAR\n",
            10,
        )
        .await?;
        assert!(
            !out_2.output.contains(TEST_VAR_VALUE),
            "timeout too short should yield incomplete output"
        );

        tokio::time::sleep(Duration::from_secs(7)).await;

        let out_3 = write_stdin(&session, process_id, "", 100).await?;

        assert!(
            out_3.output.contains(TEST_VAR_VALUE),
            "subsequent poll should retrieve output"
        );

        Ok(())
    }

    #[tokio::test]
    #[ignore] // Ignored while we have a better way to test this.
    async fn requests_with_large_timeout_are_capped() -> anyhow::Result<()> {
        let (session, turn) = test_session_and_turn().await;

        let result = exec_command(&session, &turn, "echo codex", 120_000).await?;

        assert!(result.process_id.is_some());
        assert!(result.output.contains("codex"));

        Ok(())
    }

    #[tokio::test]
    #[ignore] // Ignored while we have a better way to test this.
    async fn completed_commands_do_not_persist_sessions() -> anyhow::Result<()> {
        let (session, turn) = test_session_and_turn().await;
        let result = exec_command(&session, &turn, "echo codex", 2_500).await?;

        assert!(
            result.process_id.is_some(),
            "completed command should report a process id"
        );
        assert!(result.output.contains("codex"));

        assert!(
            session
                .services
                .unified_exec_manager
                .process_store
                .lock()
                .await
                .processes
                .is_empty()
        );

        Ok(())
    }

    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
    async fn reusing_completed_process_returns_unknown_process() -> anyhow::Result<()> {
        skip_if_sandbox!(Ok(()));

        let (session, turn) = test_session_and_turn().await;

        let open_shell = exec_command(&session, &turn, "bash -i", 2_500).await?;
        let process_id = open_shell
            .process_id
            .as_ref()
            .expect("expected process id")
            .as_str();

        write_stdin(&session, process_id, "exit\n", 2_500).await?;

        tokio::time::sleep(Duration::from_millis(200)).await;

        let err = write_stdin(&session, process_id, "", 100)
            .await
            .expect_err("expected unknown process error");

        match err {
            UnifiedExecError::UnknownProcessId { process_id: err_id } => {
                assert_eq!(err_id, process_id, "process id should match request");
            }
            other => panic!("expected UnknownProcessId, got {other:?}"),
        }

        assert!(
            session
                .services
                .unified_exec_manager
                .process_store
                .lock()
                .await
                .processes
                .is_empty()
        );

        Ok(())
    }
}