//! Query-Aware Metrics Tracking for M3.8 Optimization
//!
//! Tracks optimization progress and metrics per query_id, allowing clients
//! to monitor compression ratios, latency, and progress in real-time.
//!
//! # Example
//!
//! ```ignore
//! // Start tracking a query's optimization
//! let metrics = QueryMetrics::new("query-123", "myproject");
//!
//! // During optimization
//! metrics.record_record_optimized("log", 1000, 300);
//! metrics.record_record_optimized("text", 500, 250);
//!
//! // Query progress
//! let progress = metrics.progress();
//! println!("{:.1}% complete, {:.1}% compression", 
//!     progress.percent_complete, 
//!     progress.compression_ratio());
//!
//! // Get final metrics
//! let final_metrics = metrics.to_summary();
//! ```

use std::sync::{Arc, Mutex};
use std::collections::HashMap;
use serde::{Deserialize, Serialize};

/// Per-query optimization metrics and progress
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct QueryMetrics {
    /// Unique query identifier
    pub query_id: String,
    /// Project this query belongs to
    pub project: String,
    /// When optimization started
    pub started_at: String,
    /// Total records processed
    pub total_records: usize,
    /// Records completed (for progress tracking)
    pub records_completed: usize,
    /// Total bytes before optimization
    pub input_bytes_total: usize,
    /// Total bytes after optimization
    pub output_bytes_total: usize,
    /// Per-compressor breakdown
    pub per_compressor: HashMap<String, CompressorMetrics>,
    /// Per-content-type breakdown
    pub per_content_type: HashMap<String, ContentTypeMetrics>,
    /// Optimization status
    pub status: OptimizationStatus,
    /// Error message (if failed)
    pub error: Option<String>,
    /// Estimated time remaining (seconds)
    pub eta_secs: Option<u64>,
}

/// Optimization status enum
#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq)]
pub enum OptimizationStatus {
    /// Not yet started
    Pending,
    /// Currently optimizing
    InProgress,
    /// Successfully completed
    Completed,
    /// Failed with error
    Failed,
    /// Paused (resumable)
    Paused,
}

impl QueryMetrics {
    /// Create new query metrics tracker
    pub fn new(query_id: impl Into<String>, project: impl Into<String>) -> Self {
        Self {
            query_id: query_id.into(),
            project: project.into(),
            started_at: format!("{}", time::OffsetDateTime::now_utc()),
            total_records: 0,
            records_completed: 0,
            input_bytes_total: 0,
            output_bytes_total: 0,
            per_compressor: HashMap::new(),
            per_content_type: HashMap::new(),
            status: OptimizationStatus::Pending,
            error: None,
            eta_secs: None,
        }
    }

    /// Record a successfully optimized record
    pub fn record_record_optimized(
        &mut self,
        compressor: impl Into<String>,
        content_type: impl Into<String>,
        input_bytes: usize,
        output_bytes: usize,
    ) {
        let compressor_name = compressor.into();
        let content_type_name = content_type.into();

        self.input_bytes_total += input_bytes;
        self.output_bytes_total += output_bytes;
        self.records_completed += 1;

        // Update per-compressor stats
        self.per_compressor
            .entry(compressor_name.clone())
            .or_insert_with(|| CompressorMetrics {
                count: 0,
                input_bytes: 0,
                output_bytes: 0,
            })
            .record(input_bytes, output_bytes);

        // Update per-content-type stats
        self.per_content_type
            .entry(content_type_name)
            .or_insert_with(|| ContentTypeMetrics {
                count: 0,
                input_bytes: 0,
                output_bytes: 0,
            })
            .record(input_bytes, output_bytes);
    }

    /// Record a failed optimization (falls back to original)
    pub fn record_record_failed(&mut self, reason: impl Into<String>) {
        self.error = Some(reason.into());
    }

    /// Calculate compression ratio (%)
    pub fn compression_ratio(&self) -> f32 {
        if self.input_bytes_total == 0 {
            0.0
        } else {
            (self.output_bytes_total as f32 / self.input_bytes_total as f32) * 100.0
        }
    }

    /// Calculate progress percentage (0-100)
    pub fn percent_complete(&self) -> f32 {
        if self.total_records == 0 {
            0.0
        } else {
            (self.records_completed as f32 / self.total_records as f32) * 100.0
        }
    }

    /// Get progress snapshot
    pub fn progress(&self) -> ProgressSnapshot {
        ProgressSnapshot {
            query_id: self.query_id.clone(),
            project: self.project.clone(),
            status: self.status,
            percent_complete: self.percent_complete(),
            records_completed: self.records_completed,
            total_records: self.total_records,
            compression_ratio: self.compression_ratio(),
            input_bytes: self.input_bytes_total,
            output_bytes: self.output_bytes_total,
            eta_secs: self.eta_secs,
        }
    }

    /// Convert to summary (for storage/reporting)
    pub fn to_summary(&self) -> MetricsSummary {
        MetricsSummary {
            query_id: self.query_id.clone(),
            project: self.project.clone(),
            started_at: self.started_at.clone(),
            total_records: self.total_records,
            input_bytes_total: self.input_bytes_total,
            output_bytes_total: self.output_bytes_total,
            compression_ratio: self.compression_ratio(),
            per_compressor: self.per_compressor.clone(),
            per_content_type: self.per_content_type.clone(),
            status: self.status,
            error: self.error.clone(),
        }
    }
}

/// Progress snapshot for real-time monitoring
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ProgressSnapshot {
    pub query_id: String,
    pub project: String,
    pub status: OptimizationStatus,
    /// Percentage complete (0-100)
    pub percent_complete: f32,
    /// Records processed so far
    pub records_completed: usize,
    /// Total records to process
    pub total_records: usize,
    /// Current compression ratio (%)
    pub compression_ratio: f32,
    /// Bytes before optimization
    pub input_bytes: usize,
    /// Bytes after optimization
    pub output_bytes: usize,
    /// Estimated seconds remaining
    pub eta_secs: Option<u64>,
}

/// Summary of optimization metrics (for storage)
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MetricsSummary {
    pub query_id: String,
    pub project: String,
    pub started_at: String,
    pub total_records: usize,
    pub input_bytes_total: usize,
    pub output_bytes_total: usize,
    pub compression_ratio: f32,
    pub per_compressor: HashMap<String, CompressorMetrics>,
    pub per_content_type: HashMap<String, ContentTypeMetrics>,
    pub status: OptimizationStatus,
    pub error: Option<String>,
}

/// Per-compressor statistics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CompressorMetrics {
    pub count: usize,
    pub input_bytes: usize,
    pub output_bytes: usize,
}

impl CompressorMetrics {
    fn record(&mut self, input_bytes: usize, output_bytes: usize) {
        self.count += 1;
        self.input_bytes += input_bytes;
        self.output_bytes += output_bytes;
    }

    pub fn compression_ratio(&self) -> f32 {
        if self.input_bytes == 0 {
            0.0
        } else {
            (self.output_bytes as f32 / self.input_bytes as f32) * 100.0
        }
    }
}

/// Per-content-type statistics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ContentTypeMetrics {
    pub count: usize,
    pub input_bytes: usize,
    pub output_bytes: usize,
}

impl ContentTypeMetrics {
    fn record(&mut self, input_bytes: usize, output_bytes: usize) {
        self.count += 1;
        self.input_bytes += input_bytes;
        self.output_bytes += output_bytes;
    }

    pub fn compression_ratio(&self) -> f32 {
        if self.input_bytes == 0 {
            0.0
        } else {
            (self.output_bytes as f32 / self.input_bytes as f32) * 100.0
        }
    }
}

/// Thread-safe metrics repository indexed by query_id
#[derive(Debug, Clone)]
pub struct QueryMetricsRepository {
    metrics: Arc<Mutex<HashMap<String, QueryMetrics>>>,
}

impl QueryMetricsRepository {
    /// Create new metrics repository
    pub fn new() -> Self {
        Self {
            metrics: Arc::new(Mutex::new(HashMap::new())),
        }
    }

    /// Start tracking a new query
    pub fn create_query(&self, query_id: impl Into<String>, project: impl Into<String>) -> String {
        let query_id_str = query_id.into();
        let metrics = QueryMetrics::new(query_id_str.clone(), project);
        let mut repo = self.metrics.lock().unwrap();
        repo.insert(query_id_str.clone(), metrics);
        query_id_str
    }

    /// Get metrics for a specific query
    pub fn get_metrics(&self, query_id: &str) -> Option<QueryMetrics> {
        let repo = self.metrics.lock().unwrap();
        repo.get(query_id).cloned()
    }

    /// Update metrics for a query
    pub fn update_metrics<F>(&self, query_id: &str, f: F) -> Result<(), String>
    where
        F: FnOnce(&mut QueryMetrics),
    {
        let mut repo = self.metrics.lock().unwrap();
        repo.get_mut(query_id)
            .ok_or_else(|| format!("Query {} not found", query_id))
            .map(|metrics| f(metrics))
    }

    /// Get progress for a query
    pub fn get_progress(&self, query_id: &str) -> Option<ProgressSnapshot> {
        self.get_metrics(query_id).map(|m| m.progress())
    }

    /// List all active queries
    pub fn list_queries(&self) -> Vec<String> {
        let repo = self.metrics.lock().unwrap();
        repo.keys().cloned().collect()
    }

    /// Get metrics for all queries in a project
    pub fn get_project_metrics(&self, project: &str) -> Vec<QueryMetrics> {
        let repo = self.metrics.lock().unwrap();
        repo.values()
            .filter(|m| m.project == project)
            .cloned()
            .collect()
    }

    /// Clear completed query metrics (after storing to DB)
    pub fn remove_query(&self, query_id: &str) -> Option<QueryMetrics> {
        let mut repo = self.metrics.lock().unwrap();
        repo.remove(query_id)
    }
}

impl Default for QueryMetricsRepository {
    fn default() -> Self {
        Self::new()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_query_metrics_creation() {
        let metrics = QueryMetrics::new("q1", "project1");
        assert_eq!(metrics.query_id, "q1");
        assert_eq!(metrics.project, "project1");
        assert_eq!(metrics.status, OptimizationStatus::Pending);
    }

    #[test]
    fn test_record_optimized() {
        let mut metrics = QueryMetrics::new("q1", "project1");
        metrics.total_records = 2;
        
        metrics.record_record_optimized("log", "text/plain", 1000, 300);
        metrics.record_record_optimized("text", "text/plain", 500, 250);

        assert_eq!(metrics.records_completed, 2);
        assert_eq!(metrics.input_bytes_total, 1500);
        assert_eq!(metrics.output_bytes_total, 550);
        assert!((metrics.compression_ratio() - 36.67).abs() < 0.1);
    }

    #[test]
    fn test_progress_calculation() {
        let mut metrics = QueryMetrics::new("q1", "project1");
        metrics.total_records = 10;
        metrics.records_completed = 5;

        assert!((metrics.percent_complete() - 50.0).abs() < 0.1);
    }

    #[test]
    fn test_metrics_repository() {
        let repo = QueryMetricsRepository::new();
        
        let query_id = repo.create_query("q1", "project1");
        assert_eq!(query_id, "q1");

        assert!(repo.get_metrics("q1").is_some());
        assert!(repo.get_metrics("q2").is_none());
    }

    #[test]
    fn test_repository_update() {
        let repo = QueryMetricsRepository::new();
        repo.create_query("q1", "project1");

        repo.update_metrics("q1", |m| {
            m.total_records = 100;
            m.record_record_optimized("log", "text/plain", 1000, 300);
        }).unwrap();

        let metrics = repo.get_metrics("q1").unwrap();
        assert_eq!(metrics.total_records, 100);
        assert_eq!(metrics.records_completed, 1);
    }

    #[test]
    fn test_progress_snapshot() {
        let mut metrics = QueryMetrics::new("q1", "project1");
        metrics.total_records = 100;
        metrics.records_completed = 25;
        metrics.input_bytes_total = 10000;
        metrics.output_bytes_total = 3000;

        let progress = metrics.progress();
        assert!((progress.percent_complete - 25.0).abs() < 0.1);
        assert!((progress.compression_ratio - 30.0).abs() < 0.1);
    }

    #[test]
    fn test_per_compressor_stats() {
        let mut metrics = QueryMetrics::new("q1", "project1");
        metrics.record_record_optimized("log", "text/plain", 1000, 100);
        metrics.record_record_optimized("log", "text/plain", 500, 50);

        let log_stats = metrics.per_compressor.get("log").unwrap();
        assert_eq!(log_stats.count, 2);
        assert_eq!(log_stats.input_bytes, 1500);
        assert_eq!(log_stats.output_bytes, 150);
    }
}