//! Golden test verifying that per-band weight resolution matches the
//! JSON produced by `scripts/recalibrate.py`.
//!
//! This test sets `PROP_BAND_WEIGHTS_JSON` before any weights lookup so
//! the `OnceLock` cache in `band_config` seeds from the real JSON file.
//! It runs in a separate test binary from `scorer_golden.rs`, so the
//! env var does not affect the existing golden-fixture test.

use std::collections::HashMap;

use serde_json::Value;

use prop_grid_rs::band_config::{self, Weights};

// ── Helpers ──────────────────────────────────────────────────────────

fn weights_sum(w: &Weights) -> f64 {
    w.humidity
        + w.time_of_day
        + w.td_depression
        + w.refractivity
        + w.sky
        + w.season
        + w.wind
        + w.rain
        + w.pressure
        + w.pwat
}

fn parse_json_override_weights(json_path: &str) -> HashMap<u32, Weights> {
    let data = std::fs::read_to_string(json_path).expect("JSON file must exist");
    let root: Value = serde_json::from_str(&data).expect("valid JSON");

    let overrides = root["band_overrides"]
        .as_object()
        .expect("band_overrides must be an object");

    let mut map = HashMap::new();
    for (freq_str, entry) in overrides {
        let freq: u32 = freq_str.parse().expect("band override key must be a u32");
        let w = &entry["weights"];
        let humidity = w["humidity"].as_f64().expect("humidity");
        let time_of_day = w["time_of_day"].as_f64().expect("time_of_day");
        let td_depression = w["td_depression"].as_f64().expect("td_depression");
        let refractivity = w["refractivity"].as_f64().expect("refractivity");
        let sky = w["sky"].as_f64().expect("sky");
        let season = w["season"].as_f64().expect("season");
        let wind = w["wind"].as_f64().expect("wind");
        let rain = w["rain"].as_f64().expect("rain");
        let pwat = w["pwat"].as_f64().expect("pwat");
        let pressure = w["pressure"].as_f64().expect("pressure");

        map.insert(
            freq,
            Weights::new(
                humidity,
                time_of_day,
                td_depression,
                refractivity,
                sky,
                season,
                wind,
                rain,
                pressure,
                pwat,
            ),
        );
    }
    map
}

fn assert_weights_equal(label: &str, got: &Weights, expected: &Weights) {
    let tolerance = 1e-9;
    let factors: [(&str, f64, f64); 10] = [
        ("humidity", got.humidity, expected.humidity),
        ("time_of_day", got.time_of_day, expected.time_of_day),
        ("td_depression", got.td_depression, expected.td_depression),
        ("refractivity", got.refractivity, expected.refractivity),
        ("sky", got.sky, expected.sky),
        ("season", got.season, expected.season),
        ("wind", got.wind, expected.wind),
        ("rain", got.rain, expected.rain),
        ("pressure", got.pressure, expected.pressure),
        ("pwat", got.pwat, expected.pwat),
    ];
    for (name, g, e) in &factors {
        assert!(
            (g - e).abs() < tolerance,
            "{label} factor {name}: got {g}, expected {e}"
        );
    }
}

// ── Tests ────────────────────────────────────────────────────────────

/// Set env var before any test accesses the OnceLock cache.  `std::sync::Once`
/// ensures this runs exactly once even if the test runner spawns multiple
/// threads for `#[test]` functions in this binary.
static ENSURE_ENV: std::sync::Once = std::sync::Once::new();

fn ensure_json_env() {
    ENSURE_ENV.call_once(|| {
        std::env::set_var(
            "PROP_BAND_WEIGHTS_JSON",
            "../../priv/algo/band_weights.json",
        );
    });
}

#[test]
fn json_override_weights_match_file() {
    ensure_json_env();

    let json_path = "../../priv/algo/band_weights.json";
    let expected = parse_json_override_weights(json_path);

    for band in band_config::all_bands() {
        let w = band.weights();

        // Every weight vector must sum to ~1.0
        let sum = weights_sum(&w);
        assert!(
            (sum - 1.0).abs() < 0.001,
            "band {} MHz weights sum = {sum} (expected 1.0 ± 0.001)",
            band.freq_mhz,
        );

        // If JSON has an override for this band, it must match exactly
        if let Some(exp) = expected.get(&band.freq_mhz) {
            assert_weights_equal(&format!("band {} MHz", band.freq_mhz), &w, exp);
        }
    }
}

#[test]
fn all_bands_weights_sum_to_one() {
    ensure_json_env();

    for band in band_config::all_bands() {
        let w = band.weights();
        let sum = weights_sum(&w);
        assert!(
            (sum - 1.0).abs() < 0.001,
            "band {} MHz weights sum = {sum}",
            band.freq_mhz,
        );
    }
}