//! Checkpoint Uploader - Upload trained model checkpoints to S3
//!
//! This utility uploads all trained model checkpoints from local storage
//! to S3-compatible storage (MinIO in development) for archival and
//! production deployment.
//!
//! Usage:
//!   cargo run --example checkpoint_uploader -- --source-dir ml/trained_models/production

use std::path::{Path, PathBuf};
use std::time::Instant;
use storage::{ObjectStoreBackend, Storage};
use config::schemas::S3Config;
use clap::Parser;
use tracing::{info, warn, error};

#[derive(Parser, Debug)]
#[clap(name = "checkpoint_uploader")]
#[clap(about = "Upload trained model checkpoints to S3")]
struct Args {
    /// Source directory containing checkpoints
    #[clap(short, long, default_value = "ml/trained_models/production")]
    source_dir: PathBuf,

    /// S3 bucket name
    #[clap(short, long, default_value = "foxhunt-ml-models")]
    bucket: String,

    /// Dry run - don't actually upload
    #[clap(short, long)]
    dry_run: bool,
}

#[derive(Debug)]
struct UploadStats {
    total_files: usize,
    uploaded_files: usize,
    failed_files: usize,
    total_bytes: u64,
    duration_secs: f64,
}

impl UploadStats {
    fn new() -> Self {
        Self {
            total_files: 0,
            uploaded_files: 0,
            failed_files: 0,
            total_bytes: 0,
            duration_secs: 0.0,
        }
    }

    fn throughput_mbps(&self) -> f64 {
        if self.duration_secs > 0.0 {
            (self.total_bytes as f64) / (1024.0 * 1024.0 * self.duration_secs)
        } else {
            0.0
        }
    }
}

/// Parse checkpoint filename to extract model name and version
fn parse_checkpoint_filename(filename: &str) -> Option<(String, String, String)> {
    // Expected formats:
    // - dqn_epoch_100.safetensors -> (dqn, epoch_100, .safetensors)
    // - ppo_checkpoint_epoch_200.safetensors -> (ppo, epoch_200, .safetensors)
    // - dqn_final_epoch500.safetensors -> (dqn, epoch500, .safetensors)

    if !filename.ends_with(".safetensors") {
        return None;
    }

    let name_without_ext = filename.trim_end_matches(".safetensors");

    // Try to extract model name and epoch
    if let Some(pos) = name_without_ext.find("_epoch") {
        let model_name = &name_without_ext[..pos];
        let model_clean = model_name.trim_end_matches("_checkpoint").trim_end_matches("_final");
        let epoch_part = &name_without_ext[pos..];

        return Some((
            model_clean.to_string(),
            epoch_part.to_string(),
            ".safetensors".to_string()
        ));
    }

    None
}

/// Generate S3 path for checkpoint
fn get_s3_path(model_name: &str, version: &str, filename: &str) -> String {
    format!("{}/{}/checkpoints/{}", model_name, version, filename)
}

async fn upload_checkpoint(
    backend: &ObjectStoreBackend,
    source_path: &Path,
    s3_path: &str,
    dry_run: bool,
) -> Result<u64, Box<dyn std::error::Error>> {
    let file_size = tokio::fs::metadata(source_path).await?.len();

    if dry_run {
        info!("DRY RUN: Would upload {} ({} bytes) -> {}",
              source_path.display(), file_size, s3_path);
        return Ok(file_size);
    }

    info!("Uploading {} ({} bytes) -> {}",
          source_path.display(), file_size, s3_path);

    // Read file contents
    let data = tokio::fs::read(source_path).await?;

    // Upload to S3
    backend.store(s3_path, &data).await?;

    info!("Successfully uploaded: {}", s3_path);
    Ok(file_size)
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Initialize logging
    tracing_subscriber::fmt()
        .with_env_filter(
            tracing_subscriber::EnvFilter::from_default_env()
                .add_directive("checkpoint_uploader=info".parse()?)
                .add_directive("storage=info".parse()?)
        )
        .init();

    let args = Args::parse();

    info!("Checkpoint Uploader");
    info!("  Source directory: {}", args.source_dir.display());
    info!("  S3 bucket: {}", args.bucket);
    info!("  Dry run: {}", args.dry_run);

    // Configure S3 backend for MinIO
    let s3_config = S3Config {
        bucket_name: args.bucket.clone(),
        region: "us-east-1".to_string(),
        access_key_id: Some("foxhunt".to_string()),
        secret_access_key: Some("foxhunt_dev_password".to_string()),
        session_token: None,
        endpoint_url: Some("http://localhost:9000".to_string()),
        force_path_style: true,
        timeout: std::time::Duration::from_secs(30),
        max_retry_attempts: 3,
        use_ssl: false,
    };

    info!("Initializing S3 backend...");
    let backend = ObjectStoreBackend::new(s3_config, None).await?;
    info!("S3 backend initialized successfully");

    // Scan source directory for checkpoints
    info!("Scanning directory: {}", args.source_dir.display());

    let mut entries = tokio::fs::read_dir(&args.source_dir).await?;
    let mut checkpoints = Vec::new();

    while let Some(entry) = entries.next_entry().await? {
        let path = entry.path();
        if path.is_file() {
            if let Some(filename) = path.file_name().and_then(|n| n.to_str()) {
                if filename.ends_with(".safetensors") {
                    checkpoints.push(path);
                }
            }
        }
    }

    info!("Found {} checkpoint files", checkpoints.len());

    // Upload checkpoints
    let start = Instant::now();
    let mut stats = UploadStats::new();
    stats.total_files = checkpoints.len();

    for checkpoint_path in checkpoints {
        let filename = checkpoint_path.file_name()
            .and_then(|n| n.to_str())
            .unwrap_or("unknown");

        // Parse filename to determine model and version
        let (model_name, version) = if let Some((model, ver, _)) = parse_checkpoint_filename(filename) {
            (model, ver)
        } else {
            warn!("Could not parse checkpoint filename: {}, using defaults", filename);
            ("unknown".to_string(), "v1.0".to_string())
        };

        // Generate S3 path
        let s3_path = get_s3_path(&model_name, &version, filename);

        // Upload checkpoint
        match upload_checkpoint(&backend, &checkpoint_path, &s3_path, args.dry_run).await {
            Ok(size) => {
                stats.uploaded_files += 1;
                stats.total_bytes += size;
            }
            Err(e) => {
                error!("Failed to upload {}: {}", filename, e);
                stats.failed_files += 1;
            }
        }
    }

    stats.duration_secs = start.elapsed().as_secs_f64();

    // Print summary
    println!("\n╔══════════════════════════════════════════════════════════╗");
    println!("║         Checkpoint Upload Summary                        ║");
    println!("╠══════════════════════════════════════════════════════════╣");
    println!("║ Total files:     {:>6}                                  ║", stats.total_files);
    println!("║ Uploaded:        {:>6}                                  ║", stats.uploaded_files);
    println!("║ Failed:          {:>6}                                  ║", stats.failed_files);
    println!("║ Total size:      {:>6} MB                              ║", stats.total_bytes / (1024 * 1024));
    println!("║ Duration:        {:>6.2} seconds                         ║", stats.duration_secs);
    println!("║ Throughput:      {:>6.2} MB/s                           ║", stats.throughput_mbps());
    println!("╚══════════════════════════════════════════════════════════╝");

    if args.dry_run {
        println!("\nDRY RUN COMPLETE - No files were actually uploaded");
    } else {
        println!("\nUpload complete!");

        // Verify uploads by listing S3 bucket
        info!("Verifying uploads...");
        let uploaded_objects = backend.list("").await?;
        println!("S3 bucket now contains {} objects", uploaded_objects.len());
    }

    Ok(())
}

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

    #[test]
    fn test_parse_checkpoint_filename() {
        let test_cases = vec![
            ("dqn_epoch_100.safetensors", Some(("dqn".to_string(), "_epoch_100".to_string(), ".safetensors".to_string()))),
            ("ppo_checkpoint_epoch_200.safetensors", Some(("ppo".to_string(), "_epoch_200".to_string(), ".safetensors".to_string()))),
            ("dqn_final_epoch500.safetensors", Some(("dqn".to_string(), "_epoch500".to_string(), ".safetensors".to_string()))),
            ("invalid.txt", None),
        ];

        for (input, expected) in test_cases {
            let result = parse_checkpoint_filename(input);
            assert_eq!(result, expected, "Failed for input: {}", input);
        }
    }

    #[test]
    fn test_get_s3_path() {
        let path = get_s3_path("dqn", "epoch_100", "dqn_epoch_100.safetensors");
        assert_eq!(path, "dqn/epoch_100/checkpoints/dqn_epoch_100.safetensors");
    }
}