/// Background job system for long-running embedding tasks.
/// POST /vectors/index returns a job_id immediately.
/// GET /vectors/jobs/{id} returns progress.
/// Embedding runs in background via tokio::spawn.

use serde::Serialize;
use std::collections::HashMap;
use std::sync::Arc;
use tokio::sync::RwLock;

#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "lowercase")]
pub enum JobStatus {
    Running,
    Completed,
    Failed,
}

#[derive(Debug, Clone, Serialize)]
pub struct Job {
    pub id: String,
    pub status: JobStatus,
    pub index_name: String,
    pub total_chunks: usize,
    /// How many chunks have been embedded so far.
    /// Also serialized as "processed" for backward-compat with monitoring scripts.
    pub embedded_chunks: usize,
    #[serde(rename = "processed")]
    pub processed_alias: usize,
    pub total: usize,
    pub progress_pct: f32,
    pub storage_key: Option<String>,
    pub error: Option<String>,
    pub started_at: String,
    pub completed_at: Option<String>,
    pub chunks_per_sec: f32,
}

/// Shared progress tracker that background tasks update.
#[derive(Clone)]
pub struct JobTracker {
    jobs: Arc<RwLock<HashMap<String, Job>>>,
}

impl JobTracker {
    pub fn new() -> Self {
        Self {
            jobs: Arc::new(RwLock::new(HashMap::new())),
        }
    }

    /// Register a new job. Returns the job ID.
    pub async fn create(&self, index_name: &str, total_chunks: usize) -> String {
        let id = format!("job-{}", chrono::Utc::now().timestamp_millis());
        let job = Job {
            id: id.clone(),
            status: JobStatus::Running,
            index_name: index_name.to_string(),
            total_chunks,
            embedded_chunks: 0,
            processed_alias: 0,
            total: total_chunks,
            progress_pct: 0.0,
            storage_key: None,
            error: None,
            started_at: chrono::Utc::now().to_rfc3339(),
            completed_at: None,
            chunks_per_sec: 0.0,
        };
        self.jobs.write().await.insert(id.clone(), job);
        id
    }

    /// Update progress.
    pub async fn update_progress(&self, id: &str, embedded: usize, rate: f32) {
        let mut jobs = self.jobs.write().await;
        if let Some(job) = jobs.get_mut(id) {
            job.embedded_chunks = embedded;
            job.processed_alias = embedded;  // keep alias in sync
            job.progress_pct = if job.total_chunks > 0 {
                (embedded as f32 / job.total_chunks as f32) * 100.0
            } else {
                0.0
            };
            job.chunks_per_sec = rate;
        }
    }

    /// Mark job as completed.
    pub async fn complete(&self, id: &str, storage_key: String) {
        let mut jobs = self.jobs.write().await;
        if let Some(job) = jobs.get_mut(id) {
            job.status = JobStatus::Completed;
            job.embedded_chunks = job.total_chunks;
            job.processed_alias = job.total_chunks;
            job.progress_pct = 100.0;
            job.storage_key = Some(storage_key);
            job.completed_at = Some(chrono::Utc::now().to_rfc3339());
        }
    }

    /// Mark job as failed.
    pub async fn fail(&self, id: &str, error: String) {
        let mut jobs = self.jobs.write().await;
        if let Some(job) = jobs.get_mut(id) {
            job.status = JobStatus::Failed;
            job.error = Some(error);
            job.completed_at = Some(chrono::Utc::now().to_rfc3339());
        }
    }

    /// Get job status.
    pub async fn get(&self, id: &str) -> Option<Job> {
        self.jobs.read().await.get(id).cloned()
    }

    /// List all jobs.
    pub async fn list(&self) -> Vec<Job> {
        self.jobs.read().await.values().cloned().collect()
    }
}