//! Phase E.0 Task 7 — random-uniform policy reward baseline.
//!
//! Loads MBP-10 snapshots into the Phase E `ExecutionEnv` with a `FillModel`
//! deserialized from JSON (the artifact produced by Task 5b), runs N random-
//! uniform episodes from randomly-sampled starting cursors, and reports
//! mean / std / percentile distribution of terminal reward. This baseline
//! defines the kill-criterion threshold the E.1 DQN smoke must exceed
//! (`mean + 2σ` — written to ISV slots 547/548 in the trainer).
//!
//! ## Run
//!
//! ```bash
//! SQLX_OFFLINE=true cargo run -p ml --release --example alpha_random_baseline -- \
//!   --mbp10-dir /home/jgrusewski/Work/foxhunt/test_data/futures-baseline-mbp10/ES.FUT \
//!   --fill-coeffs config/ml/alpha_fill_coeffs.json \
//!   --horizon 600 \
//!   --n-episodes 10000 \
//!   --out-path config/ml/alpha_random_baseline.json
//! ```
//!
//! ## L1-only data limitation (inherited)
//!
//! Same as the fit binary: `parse_mbp10_streaming` populates only L1. L2/L3
//! posting prices in the synthesized `SnapshotRow` are L1 ± 0.25-tick
//! offsets (ES futures tick size). Fill probabilities at L2/L3 still derive
//! from the JSON-supplied coefficients (which themselves are L1 with
//! attenuated β_0).

use std::fs::File;
use std::io::Write;
use std::path::PathBuf;

use anyhow::{Context, Result};
use clap::Parser;
use tracing::{info, warn};

use data::providers::databento::{
    dbn_parser::DbnParser,
    mbp10::Mbp10Snapshot,
};
use ml::env::action_space::N_ACTIONS;
use ml::env::execution_env::{
    EpisodeState, ExecutionEnv, ExecutionEnvConfig, ReplayRng, SnapshotRow,
};
use ml::env::fill_model::{FillCoeffs, FillModel};
use ml::trainers::dqn::collect_dbn_files_recursive;

/// Convert raw `Mbp10Msg.price` (i64 fixed-point at 1e9 scale per the
/// databento DBN format) to f32 in price units. See
/// `alpha_fit_fill_model.rs` for the rationale (mismatch with
/// `BidAskPair::price_to_f64`'s 1e12 convention).
#[inline]
fn raw_price_to_f32(fixed: i64) -> f32 {
    (fixed as f64 * 1e-9) as f32
}

/// ES futures minimum price increment.
const TICK: f32 = 0.25;

#[derive(Debug, Parser)]
#[command(
    name = "alpha_random_baseline",
    about = "Phase E.0 Task 7 — random-uniform policy reward baseline"
)]
struct Cli {
    /// Directory containing MBP-10 `.dbn[.zst]` files.
    #[arg(long)]
    mbp10_dir: PathBuf,
    /// Path to fitted FillModel JSON (from Task 5b).
    #[arg(long, default_value = "config/ml/alpha_fill_coeffs.json")]
    fill_coeffs: PathBuf,
    /// Episode horizon in snapshots.
    #[arg(long, default_value_t = 600)]
    horizon: usize,
    /// Number of random episodes to simulate.
    #[arg(long, default_value_t = 10_000)]
    n_episodes: usize,
    /// Fixed trade size per fill.
    #[arg(long, default_value_t = 1)]
    trade_size: i32,
    /// Per-contract round-turn cost in price units.
    #[arg(long, default_value_t = 0.0625)]
    cost_per_contract: f32,
    /// Master RNG seed.
    #[arg(long, default_value_t = 0xCAFEBABE_u64)]
    seed: u64,
    /// MBP-10 events between snapshot emissions.
    #[arg(long, default_value_t = 50)]
    snapshot_interval: usize,
    /// Cap on snapshots loaded (memory budget).
    #[arg(long, default_value_t = 500_000)]
    max_snapshots: usize,
    /// Output JSON path.
    #[arg(long, default_value = "config/ml/alpha_random_baseline.json")]
    out_path: PathBuf,
}

fn load_fill_model(path: &std::path::Path) -> Result<FillModel> {
    let s = std::fs::read_to_string(path)
        .with_context(|| format!("reading fill coeffs JSON at {}", path.display()))?;
    let v: serde_json::Value = serde_json::from_str(&s)
        .with_context(|| format!("parsing fill coeffs JSON at {}", path.display()))?;
    let parse_levels = |key: &str| -> Result<[FillCoeffs; 3]> {
        let arr = v[key]
            .as_array()
            .ok_or_else(|| anyhow::anyhow!("missing/non-array field `{}`", key))?;
        if arr.len() != 3 {
            anyhow::bail!("`{}` must have 3 entries, got {}", key, arr.len());
        }
        let mut out: [FillCoeffs; 3] = [FillCoeffs { beta: [0.0; 5] }; 3];
        for (i, lvl) in arr.iter().enumerate() {
            let vv = lvl
                .as_array()
                .ok_or_else(|| anyhow::anyhow!("`{}`[{}] not array", key, i))?;
            if vv.len() != 5 {
                anyhow::bail!("`{}`[{}] must have 5 floats, got {}", key, i, vv.len());
            }
            for k in 0..5 {
                out[i].beta[k] = vv[k]
                    .as_f64()
                    .ok_or_else(|| anyhow::anyhow!("`{}`[{}][{}] not number", key, i, k))?
                    as f32;
            }
        }
        Ok(out)
    };
    Ok(FillModel {
        bid_coeffs: parse_levels("bid_coeffs")?,
        ask_coeffs: parse_levels("ask_coeffs")?,
    })
}

fn main() -> Result<()> {
    tracing_subscriber::fmt()
        .with_env_filter(
            tracing_subscriber::EnvFilter::try_from_default_env()
                .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new("info")),
        )
        .init();
    let cli = Cli::parse();
    info!("Phase E.0 Task 7 — random-uniform baseline starting");
    info!("  mbp10_dir    = {}", cli.mbp10_dir.display());
    info!("  fill_coeffs  = {}", cli.fill_coeffs.display());
    info!("  horizon      = {}", cli.horizon);
    info!("  n_episodes   = {}", cli.n_episodes);
    info!("  trade_size   = {}", cli.trade_size);
    info!("  cost         = {:.4}", cli.cost_per_contract);
    info!("  seed         = {:#x}", cli.seed);

    // --- 1. Load FillModel ---
    let fill_model = load_fill_model(&cli.fill_coeffs)?;
    info!(
        "Loaded FillModel from {} (bid β_0={:+.3}, ask β_0={:+.3})",
        cli.fill_coeffs.display(),
        fill_model.bid_coeffs[0].beta[0],
        fill_model.ask_coeffs[0].beta[0],
    );

    // --- 2. Stream MBP-10 → env::SnapshotRow ---
    let parser = DbnParser::new().context("DbnParser::new")?;
    let files = collect_dbn_files_recursive(&cli.mbp10_dir);
    if files.is_empty() {
        anyhow::bail!("no MBP-10 .dbn[.zst] files in {:?}", cli.mbp10_dir);
    }
    info!("Found {} MBP-10 file(s)", files.len());

    let mut rows: Vec<SnapshotRow> = Vec::with_capacity(cli.max_snapshots);
    'files: for file in &files {
        let mut hit_limit = false;
        let result =
            parser.parse_mbp10_streaming(file, cli.snapshot_interval, |snap: &Mbp10Snapshot| {
                if rows.len() >= cli.max_snapshots {
                    hit_limit = true;
                    return;
                }
                if snap.levels.is_empty() {
                    return;
                }
                let l1 = &snap.levels[0];
                let bid_l1 = raw_price_to_f32(l1.bid_px);
                let ask_l1 = raw_price_to_f32(l1.ask_px);
                if bid_l1 <= 0.0 || ask_l1 <= 0.0 || bid_l1 >= ask_l1 {
                    return;
                }
                let mid = 0.5 * (bid_l1 + ask_l1);
                let spread_bps = 10_000.0 * (ask_l1 - bid_l1) / mid;
                let bid_sz = l1.bid_sz as f32;
                let ask_sz = l1.ask_sz as f32;
                let l1_imbalance = if bid_sz + ask_sz > 0.0 {
                    bid_sz / (bid_sz + ask_sz)
                } else {
                    0.5
                };
                let ofi_sum_5 = bid_sz - ask_sz;
                // Phase E.4.A.3: L1-L10 depth — L1 from real MBP-10,
                // L2-L10 synthesized at ±tick offsets (parser fix
                // 5c0bcb1fd makes real L2-L10 available; wire in
                // Task 5 follow-on).
                let mut bid_l = [0.0_f32; 10];
                let mut ask_l = [0.0_f32; 10];
                for k in 0..10 {
                    bid_l[k] = bid_l1 - (k as f32) * TICK;
                    ask_l[k] = ask_l1 + (k as f32) * TICK;
                }

                rows.push(SnapshotRow {
                    mid_price: mid,
                    bid_l,
                    ask_l,
                    alpha_logit: 0.0,        // Random policy ignores state — placeholder.
                    alpha_confidence: 0.5,   // placeholder.
                    spread_bps,
                    l1_imbalance,
                    ofi_sum_5,
                    mid_drift_5: 0.0,        // placeholder (no rolling history maintained).
                    time_since_trade_s: 0.0, // no trade tape loaded in baseline.
                    book_event_rate: 5.0,    // plausible default, doesn't influence reward.
                });
            });
        match result {
            Ok(c) => info!(
                "  {} → {} streamed snapshots",
                file.file_name().unwrap_or_default().to_string_lossy(),
                c
            ),
            Err(e) => warn!("parser error on {}: {}", file.display(), e),
        }
        if hit_limit {
            info!("max_snapshots cap reached; stopping iteration");
            break 'files;
        }
    }
    info!("Loaded {} snapshots into env", rows.len());
    if rows.len() <= cli.horizon {
        anyhow::bail!(
            "insufficient snapshots ({}) for horizon ({}); reduce horizon or raise --max-snapshots",
            rows.len(),
            cli.horizon
        );
    }

    // --- 3. Construct env, run random episodes ---
    let n_rows = rows.len();
    let mut env = ExecutionEnv::new(
        ExecutionEnvConfig {
            horizon_snapshots: cli.horizon,
            trade_size_contracts: cli.trade_size,
            cost_per_contract: cli.cost_per_contract,
        },
        fill_model,
        rows,
        cli.seed,
    );

    let mut episode_rng = ReplayRng::new(cli.seed.wrapping_add(0xDEAD_BEEF));
    let mut rewards: Vec<f32> = Vec::with_capacity(cli.n_episodes);
    let max_start = n_rows.saturating_sub(cli.horizon + 1).max(1);
    let mut n_fills_total: u64 = 0;

    for ep in 0..cli.n_episodes {
        let start_cursor = (episode_rng.next_u64() as usize) % max_start;
        let env_seed = episode_rng.next_u64();
        let mut action_rng = ReplayRng::new(episode_rng.next_u64());
        env.reset_at(env_seed, start_cursor);
        let mut state = EpisodeState::new();
        let mut terminal_reward = 0.0_f32;
        loop {
            let action = (action_rng.next_u64() % N_ACTIONS as u64) as u8;
            match env.step(action, &mut state) {
                Some((_, reward, done)) => {
                    if done {
                        terminal_reward = reward;
                        break;
                    }
                }
                None => break,
            }
        }
        rewards.push(terminal_reward);
        n_fills_total += state.n_fills as u64;
        if (ep + 1) % 1000 == 0 {
            info!(
                "  episode {}/{} (latest_reward={:+.4}, fills={})",
                ep + 1,
                cli.n_episodes,
                terminal_reward,
                state.n_fills
            );
        }
    }

    // --- 4. Statistics ---
    let n = rewards.len() as f64;
    let mean: f64 = rewards.iter().map(|r| *r as f64).sum::<f64>() / n;
    let var: f64 = rewards
        .iter()
        .map(|r| (*r as f64 - mean).powi(2))
        .sum::<f64>()
        / n;
    let std = var.sqrt();
    let mut sorted = rewards.clone();
    sorted.sort_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
    let pick = |q: f64| -> f32 {
        let idx = (q * (n - 1.0)).round() as usize;
        sorted[idx.min(sorted.len() - 1)]
    };
    let p05 = pick(0.05);
    let p25 = pick(0.25);
    let p50 = pick(0.50);
    let p75 = pick(0.75);
    let p95 = pick(0.95);
    let kill_threshold = mean + 2.0 * std;
    let avg_fills_per_ep = n_fills_total as f64 / n;

    info!(
        "=== Random-uniform baseline ({} episodes, horizon {}) ===",
        cli.n_episodes, cli.horizon
    );
    info!("  mean             = {:+.6}", mean);
    info!("  std              = {:.6}", std);
    info!("  p05              = {:+.6}", p05);
    info!("  p25              = {:+.6}", p25);
    info!("  p50 (median)     = {:+.6}", p50);
    info!("  p75              = {:+.6}", p75);
    info!("  p95              = {:+.6}", p95);
    info!("  kill (mean + 2σ) = {:+.6}", kill_threshold);
    info!("  avg fills/ep     = {:.2}", avg_fills_per_ep);

    // --- 5. Save JSON ---
    let json = serde_json::json!({
        "phase": "E.0 Task 7",
        "n_episodes": cli.n_episodes,
        "horizon": cli.horizon,
        "trade_size_contracts": cli.trade_size,
        "cost_per_contract": cli.cost_per_contract,
        "seed": cli.seed,
        "n_snapshots_loaded": n_rows,
        "snapshot_interval": cli.snapshot_interval,
        "fill_coeffs_path": cli.fill_coeffs.to_string_lossy(),
        "mean_reward": mean,
        "std_reward": std,
        "p05_reward": p05,
        "p25_reward": p25,
        "p50_reward": p50,
        "p75_reward": p75,
        "p95_reward": p95,
        "kill_threshold_mean_plus_2sigma": kill_threshold,
        "avg_fills_per_episode": avg_fills_per_ep,
    });
    let mut f = File::create(&cli.out_path).context("create out file")?;
    write!(f, "{}", serde_json::to_string_pretty(&json)?)?;
    info!("Wrote results to {}", cli.out_path.display());

    Ok(())
}