//! Believability regression harness (T-1083) — the D-245 acceptance-gate enforcer.
//!
//! D-245 makes "the nature layers read alive *anywhere*" the deliverable of the
//! cascade's nature half. This harness is its repeatable instrument: for a set of
//! validation bodies at fixed seeds it runs the real deterministic cascade, computes
//! the [`BelievabilityReport`] (contrast + coherence — never marginal per-tile counts,
//! the T-1083 lesson), and:
//!
//! 1. **Determinism** — derives each body twice and asserts the reports are identical
//!    (the D-010 contract; the strongest invariant, platform-independent).
//! 2. **Golden baseline** — snapshots the reports so any future cascade change that
//!    moves believability (a regression *or* an improvement, e.g. when T-1080/T-1082
//!    land) is caught and must be acknowledged. Regenerate with
//!    `UPDATE_GOLDEN=1 cargo test --test believability_harness`.
//! 3. **D-245 criteria (advisory → strict)** — prints each criterion's pass/fail per
//!    body. Per D-245 the gate starts *budgeted + advisory* (thresholds are Q-123-TBD);
//!    set `BELIEVABILITY_STRICT=1` to make unmet criteria *fail* the test (they do
//!    today — that is the point: T-1080/T-1081/T-1082 are the open work to flip them).
//!
//! Distinct from `derivation_harness` (T-1031), which checks the binding *laws*; this
//! is its believability sibling — laws are necessary, this is the sufficiency gate.
//!
//! Bodies whose committed data (systems.db / heightmap) is absent are **skipped** with
//! a logged note (matching `derivation_harness`), so the harness is robust in trimmed
//! checkouts. The golden is an x86_64 reference (the cascade has f32 warp paths, per
//! `cascade_golden`).

use settled_reach_server::atlas::believability::{
    analyze, cascade_snapshot_for_body, evaluate_criteria, seed_to_u64, BelievabilityReport,
};

const GOLDEN_FILE: &str = "tests/golden/believability.json";

/// `(label, body_id, seed)` — lore-anchored validation bodies spanning the climate
/// extremes the gate must handle: a temperate ocean world (should read lush) and a
/// frozen ice world (must read as a living *cold* landscape, not blank — D-245).
const VALIDATION_BODIES: &[(&str, &str, &str)] = &[
    ("Arbour (temperate/ocean)", "GJ338Bd", "believability-v1"),
    ("Edict (frozen/ice)", "GJ244Ad", "believability-v1"),
];

/// Run the cascade + analyze for one body, or `None` if its committed data is absent.
fn report_for(body_id: &str, seed: &str) -> Option<BelievabilityReport> {
    let world_seed = seed_to_u64(seed);
    match cascade_snapshot_for_body(world_seed, body_id) {
        Ok((snapshot, params)) => {
            let bws = snapshot.into_body_world_state();
            Some(analyze(
                world_seed,
                body_id,
                &bws.districts,
                bws.heightmap_width,
                bws.heightmap_height,
                params.body_radius_km,
            ))
        }
        Err(e) => {
            eprintln!("[believability] SKIP {body_id}: {e}");
            None
        }
    }
}

#[test]
fn believability_determinism_and_golden() {
    let mut reports: Vec<BelievabilityReport> = Vec::new();

    for (label, body_id, seed) in VALIDATION_BODIES {
        let Some(first) = report_for(body_id, seed) else {
            continue;
        };
        // Determinism (D-010): a second full cascade + analyze must match exactly.
        let second = report_for(body_id, seed).expect("body resolved once, must resolve again");
        assert_eq!(
            first, second,
            "[{label}] non-deterministic believability report — D-010 broken"
        );

        // Structural sanity that holds regardless of believability quality or platform.
        assert!(
            first.district_count > 0,
            "[{label}] cascade produced no districts"
        );
        assert!(
            first.coherence.water_districts_wet <= first.coherence.water_districts,
            "[{label}] wet water districts exceed total"
        );

        // Advisory D-245 criteria report (strict via BELIEVABILITY_STRICT=1).
        let strict = std::env::var("BELIEVABILITY_STRICT").is_ok();
        let crit = evaluate_criteria(&first);
        let passes = crit.iter().filter(|c| c.pass).count();
        eprintln!(
            "[believability] {label}: {passes}/{} D-245 criteria pass",
            crit.len()
        );
        for c in &crit {
            eprintln!(
                "    [{}] {} — {}",
                if c.pass { "PASS" } else { "FAIL" },
                c.name,
                c.detail
            );
            if strict {
                assert!(
                    c.pass,
                    "[{label}] D-245 criterion failed (strict): {}",
                    c.name
                );
            }
        }

        reports.push(first);
    }

    if reports.is_empty() {
        eprintln!("[believability] no validation bodies available — skipping golden");
        return;
    }

    // ── Golden baseline ─────────────────────────────────────────────────────
    let golden_path = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR")).join(GOLDEN_FILE);
    let actual_json = serde_json::to_string_pretty(&reports).expect("serialize reports") + "\n";

    if std::env::var("UPDATE_GOLDEN").is_ok() {
        std::fs::create_dir_all(golden_path.parent().unwrap()).expect("mkdir golden");
        std::fs::write(&golden_path, &actual_json).expect("write golden");
        eprintln!("Golden written: {}", golden_path.display());
        return;
    }

    let golden_json = std::fs::read_to_string(&golden_path).unwrap_or_else(|e| {
        panic!(
            "Golden not found: {}.\n\
             First run: UPDATE_GOLDEN=1 cargo test --test believability_harness\n{e}",
            golden_path.display()
        )
    });

    let actual_v: serde_json::Value = serde_json::from_str(&actual_json).expect("reparse actual");
    let golden_v: serde_json::Value = serde_json::from_str(&golden_json).expect("parse golden");
    assert!(
        actual_v == golden_v,
        "Believability golden mismatch — the cascade moved believability (regression OR \
         improvement). If intended (e.g. T-1080/T-1082 landed), update:\n\
         UPDATE_GOLDEN=1 cargo test --test believability_harness\n\nActual:\n{}",
        actual_json.trim()
    );
}