use crate::output::TaskOutputManager;
use crate::types::*;
use std::collections::HashMap;
use std::path::PathBuf;
use tokio::io::AsyncBufReadExt;
use tokio::process::Command;
use tokio::sync::RwLock;

#[derive(Debug, thiserror::Error)]
pub enum TaskError {
    #[error("Task '{0}' not found")]
    NotFound(String),
    #[error("Task '{0}' is already running")]
    AlreadyRunning(String),
    #[error("Task '{0}' is not running")]
    NotRunning(String),
    #[error("Failed to spawn process: {0}")]
    SpawnFailed(String),
    #[error("IO error: {0}")]
    Io(#[from] std::io::Error),
    #[error("Task name '{0}' already exists")]
    DuplicateName(String),
}

struct RunningTask {
    abort_handles: Vec<tokio::task::JoinHandle<()>>,
    child: tokio::process::Child,
    lifecycle: Option<Box<dyn dirigent_process::ProcessLifecycle>>,
}

/// The main task runner service.
/// All methods take &self — uses interior mutability for shared access.
pub struct TaskRunner {
    definitions: RwLock<HashMap<TaskId, TaskDefinition>>,
    statuses: RwLock<HashMap<TaskId, TaskStatus>>,
    started_at: RwLock<HashMap<TaskId, chrono::DateTime<chrono::Utc>>>,
    stopped_at: RwLock<HashMap<TaskId, chrono::DateTime<chrono::Utc>>>,
    running: RwLock<HashMap<TaskId, RunningTask>>,
    tasks_dir: PathBuf,
    default_working_dir: PathBuf,
    process_manager: Option<std::sync::Arc<dyn dirigent_process::ProcessGroupManager>>,
}

impl TaskRunner {
    pub fn new(
        tasks_dir: PathBuf,
        default_working_dir: PathBuf,
        process_manager: Option<std::sync::Arc<dyn dirigent_process::ProcessGroupManager>>,
    ) -> Self {
        Self {
            definitions: RwLock::new(HashMap::new()),
            statuses: RwLock::new(HashMap::new()),
            started_at: RwLock::new(HashMap::new()),
            stopped_at: RwLock::new(HashMap::new()),
            running: RwLock::new(HashMap::new()),
            tasks_dir,
            default_working_dir,
            process_manager,
        }
    }

    pub fn tasks_dir(&self) -> &PathBuf {
        &self.tasks_dir
    }

    /// Register a task definition (does not start it).
    /// Allows re-registration to update an existing task.
    pub async fn register(&self, def: TaskDefinition) -> Result<(), TaskError> {
        let name = def.name.clone();
        self.definitions.write().await.insert(name.clone(), def);
        self.statuses
            .write()
            .await
            .entry(name)
            .or_insert(TaskStatus::Stopped);
        Ok(())
    }

    /// Remove a task definition (stops it if running)
    pub async fn remove(&self, name: &str) -> Result<(), TaskError> {
        if self.is_running(name).await {
            self.stop(name).await?;
        }
        self.definitions.write().await.remove(name);
        self.statuses.write().await.remove(name);
        self.started_at.write().await.remove(name);
        self.stopped_at.write().await.remove(name);
        Ok(())
    }

    pub async fn is_running(&self, name: &str) -> bool {
        matches!(
            self.statuses.read().await.get(name),
            Some(TaskStatus::Running { .. })
        )
    }

    /// Start a task by name
    pub async fn start(&self, name: &str) -> Result<(), TaskError> {
        let def = {
            let defs = self.definitions.read().await;
            defs.get(name)
                .cloned()
                .ok_or_else(|| TaskError::NotFound(name.to_string()))?
        };

        if self.is_running(name).await {
            return Err(TaskError::AlreadyRunning(name.to_string()));
        }

        let output_mgr = TaskOutputManager::new(self.tasks_dir.join(&def.name));
        output_mgr.ensure_dir().await?;

        if def.rotate_previous {
            if let Err(e) = output_mgr.rotate().await {
                tracing::warn!("Failed to rotate output for task {}: {}", name, e);
            }
        }

        // Resolve working directory: explicit > default > current process dir
        let raw_cwd = def
            .working_directory
            .clone()
            .unwrap_or_else(|| self.default_working_dir.clone());

        // Canonicalize to an absolute path; fall back to current dir if invalid
        let cwd = match std::fs::canonicalize(&raw_cwd) {
            Ok(p) => p,
            Err(_) => {
                tracing::warn!(
                    "Task '{}': working directory '{}' invalid, falling back to current dir",
                    name,
                    raw_cwd.display()
                );
                std::env::current_dir().unwrap_or_else(|_| PathBuf::from("."))
            }
        };

        let lifecycle = self.process_manager.as_ref().map(|mgr| mgr.create_lifecycle());

        let mut cmd = Command::new(&def.command);
        cmd.args(&def.args)
            .current_dir(&cwd)
            .stdout(std::process::Stdio::piped())
            .stderr(std::process::Stdio::piped())
            .kill_on_drop(true);

        if let Some(ref lc) = lifecycle {
            lc.configure_async_command(&mut cmd);
        }

        for (key, value) in &def.env {
            cmd.env(key, value);
        }

        let mut child = match cmd.spawn() {
            Ok(child) => child,
            Err(e) => {
                let error_msg = format!("{} (cwd: {}): {}", def.command, cwd.display(), e);
                // Write error to stderr.log and combined.log so the user can see it in the output viewer
                let timestamp = chrono::Utc::now().format("%Y-%m-%dT%H:%M:%S%.3fZ");
                let log_line = format!("[{}] Failed to start: {}\n", timestamp, error_msg);
                if def.persist_to_disk {
                    let _ = tokio::fs::write(output_mgr.stderr_path(), log_line.as_bytes()).await;
                    let _ = tokio::fs::write(output_mgr.combined_path(), format!("[stderr] {}", log_line).as_bytes()).await;
                }
                // Set status to Failed so the UI shows it
                self.statuses.write().await.insert(name.to_string(), TaskStatus::Failed { error: error_msg.clone() });
                self.stopped_at.write().await.insert(name.to_string(), chrono::Utc::now());
                return Err(TaskError::SpawnFailed(error_msg));
            }
        };
        let pid = child.id().unwrap_or(0);
        tracing::info!("Task '{}' started with PID {} (cwd: {})", name, pid, cwd.display());

        if let Some(ref lc) = lifecycle {
            if let Some(child_pid) = child.id() {
                if let Err(e) = lc.register_child(child_pid) {
                    tracing::warn!(error = %e, "Failed to register task child with process lifecycle");
                }
            }
        }

        let stdout = child.stdout.take();
        let stderr = child.stderr.take();
        let persist = def.persist_to_disk;
        let mut abort_handles = Vec::new();

        // When not rotating, truncate old logs so we don't accumulate output across restarts
        let truncate = !def.rotate_previous;
        if truncate && persist {
            let _ = tokio::fs::write(output_mgr.stdout_path(), b"").await;
            let _ = tokio::fs::write(output_mgr.stderr_path(), b"").await;
            let _ = tokio::fs::write(output_mgr.combined_path(), b"").await;
        }

        // Stdout capture task
        if let Some(stdout) = stdout {
            let stdout_path = output_mgr.stdout_path();
            let combined_path = output_mgr.combined_path();
            let task_name = name.to_string();
            let h = tokio::spawn(async move {
                let reader = tokio::io::BufReader::new(stdout);
                let mut lines = reader.lines();
                let mut stdout_file = if persist {
                    tokio::fs::OpenOptions::new()
                        .create(true)
                        .append(true)
                        .open(&stdout_path)
                        .await
                        .ok()
                } else {
                    None
                };
                let mut combined_file = if persist {
                    tokio::fs::OpenOptions::new()
                        .create(true)
                        .append(true)
                        .open(&combined_path)
                        .await
                        .ok()
                } else {
                    None
                };

                while let Ok(Some(line)) = lines.next_line().await {
                    let ts = chrono::Utc::now().format("%Y-%m-%dT%H:%M:%S%.3fZ");
                    if let Some(ref mut f) = stdout_file {
                        let _ = tokio::io::AsyncWriteExt::write_all(
                            f,
                            format!("[{}] {}\n", ts, line).as_bytes(),
                        )
                        .await;
                    }
                    if let Some(ref mut f) = combined_file {
                        let _ = tokio::io::AsyncWriteExt::write_all(
                            f,
                            format!("[{}] [stdout] {}\n", ts, line).as_bytes(),
                        )
                        .await;
                    }
                }
                tracing::debug!("Stdout capture ended for task '{}'", task_name);
            });
            abort_handles.push(h);
        }

        // Stderr capture task
        if let Some(stderr) = stderr {
            let stderr_path = output_mgr.stderr_path();
            let combined_path = output_mgr.combined_path();
            let task_name = name.to_string();
            let h = tokio::spawn(async move {
                let reader = tokio::io::BufReader::new(stderr);
                let mut lines = reader.lines();
                let mut stderr_file = if persist {
                    tokio::fs::OpenOptions::new()
                        .create(true)
                        .append(true)
                        .open(&stderr_path)
                        .await
                        .ok()
                } else {
                    None
                };
                let mut combined_file = if persist {
                    tokio::fs::OpenOptions::new()
                        .create(true)
                        .append(true)
                        .open(&combined_path)
                        .await
                        .ok()
                } else {
                    None
                };

                while let Ok(Some(line)) = lines.next_line().await {
                    let ts = chrono::Utc::now().format("%Y-%m-%dT%H:%M:%S%.3fZ");
                    if let Some(ref mut f) = stderr_file {
                        let _ = tokio::io::AsyncWriteExt::write_all(
                            f,
                            format!("[{}] {}\n", ts, line).as_bytes(),
                        )
                        .await;
                    }
                    if let Some(ref mut f) = combined_file {
                        let _ = tokio::io::AsyncWriteExt::write_all(
                            f,
                            format!("[{}] [stderr] {}\n", ts, line).as_bytes(),
                        )
                        .await;
                    }
                }
                tracing::debug!("Stderr capture ended for task '{}'", task_name);
            });
            abort_handles.push(h);
        }

        self.statuses
            .write()
            .await
            .insert(name.to_string(), TaskStatus::Running { pid });
        self.started_at
            .write()
            .await
            .insert(name.to_string(), chrono::Utc::now());
        self.stopped_at.write().await.remove(name);

        self.running.write().await.insert(
            name.to_string(),
            RunningTask {
                abort_handles,
                child,
                lifecycle,
            },
        );

        Ok(())
    }

    /// Stop a running task
    pub async fn stop(&self, name: &str) -> Result<(), TaskError> {
        if !self.is_running(name).await {
            return Err(TaskError::NotRunning(name.to_string()));
        }

        let mut running = self.running.write().await;
        if let Some(mut task) = running.remove(name) {
            if let Some(ref lifecycle) = task.lifecycle {
                dirigent_process::graceful_shutdown_async(
                    lifecycle.as_ref(),
                    &mut task.child,
                    std::time::Duration::from_secs(3),
                )
                .await;
            } else {
                let _ = task.child.kill().await;
            }
            for h in task.abort_handles {
                h.abort();
            }
            tracing::info!("Task '{}' stopped", name);
        }

        self.statuses
            .write()
            .await
            .insert(name.to_string(), TaskStatus::Stopped);
        self.stopped_at
            .write()
            .await
            .insert(name.to_string(), chrono::Utc::now());
        Ok(())
    }

    /// Poll running tasks for completion (call periodically from a timer)
    pub async fn poll_completed(&self) {
        let mut running = self.running.write().await;
        let mut completed = Vec::new();

        for (name, task) in running.iter_mut() {
            match task.child.try_wait() {
                Ok(Some(status)) => {
                    let exit_code = status.code();
                    tracing::info!(
                        "Task '{}' finished with exit code: {:?}",
                        name,
                        exit_code
                    );
                    completed.push((name.clone(), exit_code));
                }
                Ok(None) => {}
                Err(e) => {
                    tracing::error!("Error checking task '{}': {}", name, e);
                    completed.push((name.clone(), None));
                }
            }
        }

        let mut statuses = self.statuses.write().await;
        let mut stopped_at = self.stopped_at.write().await;
        for (name, exit_code) in completed {
            running.remove(&name);
            statuses.insert(name.clone(), TaskStatus::Finished { exit_code });
            stopped_at.insert(name.clone(), chrono::Utc::now());
        }
    }

    /// List all tasks with their info
    pub async fn list_tasks(&self) -> Vec<TaskInfo> {
        let defs = self.definitions.read().await;
        let statuses = self.statuses.read().await;
        let started = self.started_at.read().await;
        let stopped = self.stopped_at.read().await;

        defs.values()
            .map(|def| TaskInfo {
                definition: def.clone(),
                status: statuses
                    .get(&def.name)
                    .cloned()
                    .unwrap_or(TaskStatus::Stopped),
                started_at: started.get(&def.name).cloned(),
                stopped_at: stopped.get(&def.name).cloned(),
            })
            .collect()
    }

    /// Get info for a specific task
    pub async fn get_task(&self, name: &str) -> Option<TaskInfo> {
        let defs = self.definitions.read().await;
        let def = defs.get(name)?;
        let statuses = self.statuses.read().await;
        let started = self.started_at.read().await;
        let stopped = self.stopped_at.read().await;
        Some(TaskInfo {
            definition: def.clone(),
            status: statuses
                .get(name)
                .cloned()
                .unwrap_or(TaskStatus::Stopped),
            started_at: started.get(name).cloned(),
            stopped_at: stopped.get(name).cloned(),
        })
    }

    /// Read output for a task
    pub async fn read_output(
        &self,
        name: &str,
        kind: OutputKind,
        tail_lines: Option<usize>,
    ) -> Result<String, TaskError> {
        {
            let defs = self.definitions.read().await;
            if !defs.contains_key(name) {
                return Err(TaskError::NotFound(name.to_string()));
            }
        }
        let mgr = TaskOutputManager::new(self.tasks_dir.join(name));
        mgr.read_output(kind, tail_lines).await.map_err(TaskError::Io)
    }

    /// Get all task definitions (for config persistence)
    pub async fn get_definitions(&self) -> Vec<TaskDefinition> {
        self.definitions.read().await.values().cloned().collect()
    }

    /// Update a task definition (stops if running, re-registers)
    pub async fn update(&self, def: TaskDefinition) -> Result<(), TaskError> {
        let name = def.name.clone();
        if self.is_running(&name).await {
            self.stop(&name).await?;
        }
        self.register(def).await
    }

    /// Stop all running tasks. Used during graceful shutdown.
    pub async fn stop_all(&self) {
        let names: Vec<String> = self.running.read().await.keys().cloned().collect();
        for name in names {
            if let Err(e) = self.stop(&name).await {
                tracing::warn!(task = %name, error = %e, "Failed to stop task during shutdown");
            }
        }
    }
}