//! Hyperopt Runner for DQN/PPO on Real Databento Market Data
//!
//! Runs hyperparameter optimization using Particle Swarm Optimization (PSO) for
//! DQN, PPO, or both models on downloaded Databento futures data. This binary is
//! part of the walk-forward real-data training pipeline.
//!
//! ## Usage
//!
//! ```bash
//! # Run DQN hyperopt only (10 trials, 10 epochs each)
//! SQLX_OFFLINE=true cargo run -p ml --example hyperopt_baseline --release -- \
//!   --model dqn --trials 10 --epochs 10 \
//!   --data-dir data/cache/futures-baseline
//!
//! # Run PPO hyperopt only
//! SQLX_OFFLINE=true cargo run -p ml --example hyperopt_baseline --release -- \
//!   --model ppo --trials 20 --epochs 15 \
//!   --data-dir data/cache/futures-baseline
//!
//! # Run both models (default)
//! SQLX_OFFLINE=true cargo run -p ml --example hyperopt_baseline --release -- \
//!   --data-dir data/cache/futures-baseline
//! ```
//!
//! ## Output
//!
//! Results are written as JSON to `--output` (default: `ml/trained_models/hyperopt_results.json`).
//!
//! ```json
//! {
//!   "dqn": { "best_objective": 0.123, "best_params": {...}, "trials": 20, "elapsed_secs": 45.3 },
//!   "ppo": { "best_objective": 0.456, "best_params": {...}, "trials": 20, "elapsed_secs": 67.8 }
//! }
//! ```

use anyhow::{Context, Result};
use clap::Parser;
use serde_json::Value;
use std::path::PathBuf;
use std::time::Instant;
use tracing::{error, info, warn, Level};

use ml::hyperopt::adapters::dqn::DQNTrainer;
use ml::hyperopt::adapters::ppo::PPOTrainer;
use ml::hyperopt::paths::{generate_run_id, TrainingPaths};
use ml::hyperopt::ArgminOptimizer;

/// Hyperparameter optimization runner for DQN/PPO on Databento market data
#[derive(Parser, Debug)]
#[command(name = "hyperopt-baseline")]
#[command(about = "Run hyperparameter optimization for DQN/PPO on real Databento futures data")]
struct Args {
    /// Model to optimize: "dqn", "ppo", or "both"
    #[arg(long, default_value = "both")]
    model: String,

    /// Number of PSO trials per model
    #[arg(long, default_value = "20")]
    trials: usize,

    /// Number of initial LHS (Latin Hypercube Sampling) samples
    #[arg(long, default_value = "5")]
    n_initial: usize,

    /// Training epochs per trial (DQN) / episodes per trial (PPO)
    #[arg(long, default_value = "10")]
    epochs: usize,

    /// Path to downloaded DBN data directory
    #[arg(long, default_value = "data/cache/futures-baseline")]
    data_dir: PathBuf,

    /// Output path for JSON results
    #[arg(long, default_value = "ml/trained_models/hyperopt_results.json")]
    output: PathBuf,

    /// Random seed for reproducibility
    #[arg(long, default_value = "42")]
    seed: u64,

    /// Base directory for training run outputs (checkpoints, logs, metrics)
    #[arg(long, default_value = "/tmp/ml_training")]
    base_dir: String,
}

/// Result entry for one model's hyperopt run
fn build_model_result(
    best_objective: f64,
    best_params_json: Value,
    num_trials: usize,
    elapsed_secs: f64,
) -> Value {
    serde_json::json!({
        "best_objective": best_objective,
        "best_params": best_params_json,
        "trials": num_trials,
        "elapsed_secs": elapsed_secs,
    })
}

fn run_dqn_hyperopt(args: &Args) -> Result<Value> {
    info!("========================================");
    info!("  DQN Hyperparameter Optimization");
    info!("========================================");

    let run_id = generate_run_id("hyperopt-dqn");
    let training_paths = TrainingPaths::new(&args.base_dir, "dqn", &run_id);

    info!("Run ID: {}", run_id);
    info!("Data directory: {}", args.data_dir.display());
    info!("Epochs per trial: {}", args.epochs);
    info!("Trials: {}", args.trials);

    let trainer = DQNTrainer::new(&args.data_dir, args.epochs)
        .context("Failed to create DQN trainer")?
        .with_training_paths(training_paths);

    let optimizer = ArgminOptimizer::builder()
        .max_trials(args.trials)
        .n_initial(args.n_initial)
        .seed(args.seed)
        .build();

    let start = Instant::now();
    let result = optimizer
        .optimize(trainer)
        .context("DQN hyperopt optimization failed")?;
    let elapsed = start.elapsed().as_secs_f64();

    info!("DQN hyperopt complete:");
    info!("  Best objective: {:.6}", result.best_objective);
    info!("  Total trials: {}", result.all_trials.len());
    info!("  Elapsed: {:.1}s", elapsed);

    let best_params_json = serde_json::to_value(&result.best_params)
        .ok()
        .unwrap_or(Value::Null);

    Ok(build_model_result(
        result.best_objective,
        best_params_json,
        result.all_trials.len(),
        elapsed,
    ))
}

fn run_ppo_hyperopt(args: &Args) -> Result<Value> {
    info!("========================================");
    info!("  PPO Hyperparameter Optimization");
    info!("========================================");

    let run_id = generate_run_id("hyperopt-ppo");
    let training_paths = TrainingPaths::new(&args.base_dir, "ppo", &run_id);

    info!("Run ID: {}", run_id);
    info!("Data directory: {}", args.data_dir.display());
    info!("Episodes per trial: {}", args.epochs);
    info!("Trials: {}", args.trials);

    let trainer = PPOTrainer::new(&args.data_dir, args.epochs)
        .context("Failed to create PPO trainer")?
        .with_training_paths(training_paths);

    let optimizer = ArgminOptimizer::builder()
        .max_trials(args.trials)
        .n_initial(args.n_initial)
        .seed(args.seed)
        .build();

    let start = Instant::now();
    let result = optimizer
        .optimize(trainer)
        .context("PPO hyperopt optimization failed")?;
    let elapsed = start.elapsed().as_secs_f64();

    info!("PPO hyperopt complete:");
    info!("  Best objective: {:.6}", result.best_objective);
    info!("  Total trials: {}", result.all_trials.len());
    info!("  Elapsed: {:.1}s", elapsed);

    let best_params_json = serde_json::to_value(&result.best_params)
        .ok()
        .unwrap_or(Value::Null);

    Ok(build_model_result(
        result.best_objective,
        best_params_json,
        result.all_trials.len(),
        elapsed,
    ))
}

fn main() -> Result<()> {
    // Initialize tracing
    tracing_subscriber::fmt()
        .with_max_level(Level::INFO)
        .with_target(false)
        .init();

    let args = Args::parse();

    info!("========================================");
    info!("  Hyperopt Baseline Runner");
    info!("========================================");
    info!("Model: {}", args.model);
    info!("Trials: {}", args.trials);
    info!("Initial LHS samples: {}", args.n_initial);
    info!("Epochs/episodes per trial: {}", args.epochs);
    info!("Data directory: {}", args.data_dir.display());
    info!("Output: {}", args.output.display());
    info!("Seed: {}", args.seed);

    // Verify data directory exists
    if !args.data_dir.exists() {
        anyhow::bail!(
            "Data directory not found: {}. Run `download_baseline` first.",
            args.data_dir.display()
        );
    }

    // Verify trials > n_initial (ArgminOptimizer requirement)
    if args.trials <= args.n_initial {
        anyhow::bail!(
            "trials ({}) must be greater than n_initial ({})",
            args.trials,
            args.n_initial
        );
    }

    // Create output directory
    if let Some(parent) = args.output.parent() {
        std::fs::create_dir_all(parent)
            .with_context(|| format!("Failed to create output directory: {}", parent.display()))?;
    }

    let run_dqn = args.model == "dqn" || args.model == "both";
    let run_ppo = args.model == "ppo" || args.model == "both";

    if !run_dqn && !run_ppo {
        anyhow::bail!(
            "Invalid --model value '{}'. Must be 'dqn', 'ppo', or 'both'.",
            args.model
        );
    }

    let mut results = serde_json::Map::new();

    // Run DQN hyperopt
    if run_dqn {
        match run_dqn_hyperopt(&args) {
            Ok(dqn_result) => {
                results.insert("dqn".to_string(), dqn_result);
            },
            Err(e) => {
                error!("DQN hyperopt failed: {:#}", e);
                warn!("Continuing with remaining models...");
                results.insert(
                    "dqn".to_string(),
                    serde_json::json!({ "error": format!("{:#}", e) }),
                );
            },
        }
    }

    // Run PPO hyperopt
    if run_ppo {
        match run_ppo_hyperopt(&args) {
            Ok(ppo_result) => {
                results.insert("ppo".to_string(), ppo_result);
            },
            Err(e) => {
                error!("PPO hyperopt failed: {:#}", e);
                warn!("Continuing...");
                results.insert(
                    "ppo".to_string(),
                    serde_json::json!({ "error": format!("{:#}", e) }),
                );
            },
        }
    }

    // Write results to JSON
    let output_json = Value::Object(results);
    let output_str = serde_json::to_string_pretty(&output_json)
        .context("Failed to serialize results to JSON")?;

    std::fs::write(&args.output, &output_str)
        .with_context(|| format!("Failed to write results to {}", args.output.display()))?;

    info!("========================================");
    info!("  Results saved to: {}", args.output.display());
    info!("========================================");
    info!("{}", output_str);

    Ok(())
}