use anyhow::{Context, Result};
use chrono::{DateTime, Utc};
use std::collections::HashMap;
use std::sync::Arc;
use tokio::sync::Mutex;
use tokio_cron_scheduler::{Job, JobScheduler};
use uuid::Uuid;

use super::nats_bridge::NatsBridge;

/// Cron-based wipe schedule management.
///
/// Manages wipe schedules backed by `tokio-cron-scheduler`. Each schedule
/// maps a cron expression + timezone to a wipe profile. When a schedule
/// fires, it creates a wipe_history record and dispatches execution to
/// the WipeEngine.
pub struct SchedulerService {
    db: sqlx::PgPool,
    nats: Arc<NatsBridge>,
    scheduler: JobScheduler,
    /// Maps schedule_id to job_id for removal
    job_handles: Arc<Mutex<HashMap<Uuid, Uuid>>>,
}

impl SchedulerService {
    pub async fn new(db: sqlx::PgPool, nats: Arc<NatsBridge>) -> Result<Self> {
        let scheduler = JobScheduler::new()
            .await
            .context("Failed to create JobScheduler")?;

        Ok(Self {
            db,
            nats,
            scheduler,
            job_handles: Arc::new(Mutex::new(HashMap::new())),
        })
    }

    /// Start the scheduler, loading all active schedules from the database.
    pub async fn start(&self) -> Result<()> {
        // Query all active wipe_schedules from DB
        let schedules: Vec<(Uuid,)> = sqlx::query_as(
            "SELECT id FROM wipe_schedules WHERE enabled = true",
        )
        .fetch_all(&self.db)
        .await
        .context("Failed to query active wipe schedules")?;

        tracing::info!("Loading {} active wipe schedules", schedules.len());

        // Register each schedule as a cron job
        for (schedule_id,) in schedules {
            if let Err(e) = self.register_wipe_schedule(schedule_id).await {
                tracing::error!("Failed to register schedule {}: {}", schedule_id, e);
                // Continue loading other schedules
            }
        }

        // Start the scheduler event loop
        self.scheduler
            .start()
            .await
            .context("Failed to start scheduler")?;

        tracing::info!("Scheduler started successfully");
        Ok(())
    }

    /// Register a wipe schedule as a cron job.
    pub async fn register_wipe_schedule(&self, schedule_id: Uuid) -> Result<()> {
        // Load WipeSchedule from DB
        let schedule: Option<(String, String, Uuid, Uuid)> = sqlx::query_as(
            "SELECT cron_expression, timezone, wipe_profile_id, license_id
             FROM wipe_schedules
             WHERE id = $1 AND enabled = true",
        )
        .bind(schedule_id)
        .fetch_optional(&self.db)
        .await
        .context("Failed to query wipe schedule")?;

        if schedule.is_none() {
            anyhow::bail!("Schedule not found or disabled: {}", schedule_id);
        }

        let (cron_expression, timezone, wipe_profile_id, license_id) = schedule.unwrap();

        // Clone references for closure
        let db = self.db.clone();
        let nats = self.nats.clone();
        let schedule_id_clone = schedule_id;

        // Create tokio-cron-scheduler job
        let job = Job::new_async(cron_expression.as_str(), move |_uuid, _l| {
            let db = db.clone();
            let nats = nats.clone();
            let wipe_profile_id = wipe_profile_id;
            let license_id = license_id;
            let schedule_id = schedule_id_clone;

            Box::pin(async move {
                tracing::info!(
                    "Scheduled wipe triggered: schedule {} (profile {})",
                    schedule_id,
                    wipe_profile_id
                );

                // Create wipe_history record
                let wipe_history_id = Uuid::new_v4();
                let result = sqlx::query(
                    "INSERT INTO wipe_history (id, license_id, wipe_profile_id, wipe_schedule_id, status, created_at)
                     VALUES ($1, $2, $3, $4, 'pending', NOW())",
                )
                .bind(wipe_history_id)
                .bind(license_id)
                .bind(wipe_profile_id)
                .bind(schedule_id)
                .execute(&db)
                .await;

                if let Err(e) = result {
                    tracing::error!("Failed to create wipe_history record: {}", e);
                    return;
                }

                // Publish wipe execution event to NATS
                let payload = serde_json::json!({
                    "wipe_history_id": wipe_history_id,
                    "license_id": license_id,
                    "wipe_profile_id": wipe_profile_id,
                    "schedule_id": schedule_id,
                    "triggered_by": "scheduler",
                    "timestamp": Utc::now().to_rfc3339(),
                });

                if let Err(e) = nats
                    .publish_jetstream(
                        &format!("corrosion.wipes.{}.execute", license_id),
                        payload.to_string().as_bytes(),
                    )
                    .await
                {
                    tracing::error!(
                        "Failed to publish wipe execution event for {}: {}",
                        wipe_history_id,
                        e
                    );
                }

                tracing::info!(
                    "Wipe execution dispatched: {} (schedule: {})",
                    wipe_history_id,
                    schedule_id
                );
            })
        })
        .context("Failed to create cron job")?;

        // Add job to scheduler
        let job_id = self
            .scheduler
            .add(job)
            .await
            .context("Failed to add job to scheduler")?;

        // Store job handle for later removal
        self.job_handles.lock().await.insert(schedule_id, job_id);

        tracing::info!(
            "Registered wipe schedule: {} (cron: {}, tz: {})",
            schedule_id,
            cron_expression,
            timezone
        );

        Ok(())
    }

    /// Remove a schedule from the running scheduler.
    pub async fn remove_schedule(&self, schedule_id: Uuid) -> Result<()> {
        // Look up job handle by schedule_id
        let job_id = {
            let mut handles = self.job_handles.lock().await;
            handles.remove(&schedule_id)
        };

        if let Some(job_id) = job_id {
            // Remove from tokio-cron-scheduler
            self.scheduler
                .remove(&job_id)
                .await
                .context("Failed to remove job from scheduler")?;

            tracing::info!("Removed wipe schedule: {}", schedule_id);
        } else {
            tracing::warn!("Schedule not found in scheduler: {}", schedule_id);
        }

        Ok(())
    }

    /// Calculate the next N scheduled run times for a given schedule.
    pub async fn get_next_runs(
        &self,
        schedule_id: Uuid,
        count: usize,
    ) -> Result<Vec<DateTime<Utc>>> {
        // Load cron_expression and timezone from DB
        let schedule: Option<(String, String)> = sqlx::query_as(
            "SELECT cron_expression, timezone FROM wipe_schedules WHERE id = $1",
        )
        .bind(schedule_id)
        .fetch_optional(&self.db)
        .await
        .context("Failed to query wipe schedule")?;

        if schedule.is_none() {
            anyhow::bail!("Schedule not found: {}", schedule_id);
        }

        let (cron_expression, _timezone) = schedule.unwrap();

        // Parse cron expression using cron library
        use cron::Schedule;
        use std::str::FromStr;

        let schedule = Schedule::from_str(&cron_expression)
            .with_context(|| format!("Invalid cron expression: {}", cron_expression))?;

        // Compute next N fire times
        let now = Utc::now();
        let next_times: Vec<DateTime<Utc>> = schedule
            .upcoming(Utc)
            .take(count)
            .collect();

        tracing::debug!(
            "Calculated {} next run times for schedule {}",
            next_times.len(),
            schedule_id
        );

        Ok(next_times)
    }

    /// Register hourly stats aggregation job (runs at :05 past every hour).
    pub async fn register_stats_aggregation(&self) -> Result<()> {
        let db = self.db.clone();

        let job = Job::new_async("0 5 * * * *", move |_uuid, _l| {
            let db = db.clone();

            Box::pin(async move {
                tracing::info!("Running hourly stats aggregation");

                // Get all active licenses
                let licenses: Vec<(Uuid,)> = match sqlx::query_as(
                    "SELECT id FROM licenses WHERE status = 'active'",
                )
                .fetch_all(&db)
                .await
                {
                    Ok(l) => l,
                    Err(e) => {
                        tracing::error!("Failed to query active licenses: {}", e);
                        return;
                    }
                };

                tracing::info!("Aggregating stats for {} licenses", licenses.len());

                for (license_id,) in licenses {
                    if let Err(e) = crate::db::stats::aggregate_hourly_stats(&db, license_id).await
                    {
                        tracing::error!(
                            "Failed to aggregate stats for license {}: {}",
                            license_id,
                            e
                        );
                    }
                }

                tracing::info!("Hourly stats aggregation complete");
            })
        })
        .context("Failed to create stats aggregation job")?;

        self.scheduler
            .add(job)
            .await
            .context("Failed to add stats aggregation job to scheduler")?;

        tracing::info!("Registered hourly stats aggregation job (cron: 0 5 * * * *)");
        Ok(())
    }

    /// Register daily stats cleanup job (runs at 03:00 UTC).
    pub async fn register_stats_cleanup(&self) -> Result<()> {
        let db = self.db.clone();

        let job = Job::new_async("0 0 3 * * *", move |_uuid, _l| {
            let db = db.clone();

            Box::pin(async move {
                tracing::info!("Running daily stats cleanup");

                // Delete raw stats older than 7 days
                match crate::db::stats::cleanup_old_stats(&db, 7).await {
                    Ok(deleted) => {
                        tracing::info!("Deleted {} old raw stats records", deleted);
                    }
                    Err(e) => {
                        tracing::error!("Failed to cleanup old raw stats: {}", e);
                    }
                }

                // Delete hourly stats older than 90 days
                match crate::db::stats::cleanup_old_hourly_stats(&db, 90).await {
                    Ok(deleted) => {
                        tracing::info!("Deleted {} old hourly stats records", deleted);
                    }
                    Err(e) => {
                        tracing::error!("Failed to cleanup old hourly stats: {}", e);
                    }
                }

                tracing::info!("Daily stats cleanup complete");
            })
        })
        .context("Failed to create stats cleanup job")?;

        self.scheduler
            .add(job)
            .await
            .context("Failed to add stats cleanup job to scheduler")?;

        tracing::info!("Registered daily stats cleanup job (cron: 0 0 3 * * *)");
        Ok(())
    }
}