//! The save parser against the three real saves committed under `docs/re/captures`.
//!
//! These need no disc and no emulator — the samples are in the repo — so this
//! runs in plain `cargo test`. The load-bearing assertion is the **byte-identical
//! round-trip**: the title's serializer writes its struct field by field with no
//! packing, so a correct parse must reproduce the payload exactly. Anything less
//! means a field has the wrong width or the chunk stream has an unread gap.

use std::path::{Path, PathBuf};

use sylpheed_formats::savegame::{self, Confidence, DevelopState, GHAD_SIZE, RECORD_COUNT};

fn captures() -> PathBuf {
    Path::new(env!("CARGO_MANIFEST_DIR")).join("../../docs/re/captures")
}

fn sample(name: &str) -> Vec<u8> {
    std::fs::read(captures().join(name)).unwrap_or_else(|e| panic!("read {name}: {e}"))
}

const SAMPLES: [&str; 3] = [
    "savedata-game02-samestate.bin",
    "savedata-game03-developed-mg1.bin",
    "savedata-stage02-5pct.bin",
];

#[test]
fn every_sample_parses_and_round_trips_byte_identically() {
    for name in SAMPLES {
        let raw = sample(name);
        let save = savegame::parse(&raw).unwrap_or_else(|e| panic!("{name}: {e}"));
        assert_eq!(save.payload.len(), 545, "{name}: the whole save is 545 bytes");
        assert_eq!(save.ghad.len(), GHAD_SIZE, "{name}");
        assert_eq!(save.records.len(), RECORD_COUNT, "{name}");
        assert!(
            save.round_trips(),
            "{name}: re-serializing did not reproduce the payload"
        );
    }
}

#[test]
fn phase_is_one_of_the_titles_screen_ids() {
    for name in SAMPLES {
        let save = savegame::parse(&sample(name)).unwrap();
        assert!(
            save.phase.starts_with("GP_"),
            "{name}: phase {:?} is not a GP_* screen id",
            save.phase
        );
    }
}

#[test]
fn trailer_closes_the_stream() {
    for name in SAMPLES {
        let save = savegame::parse(&sample(name)).unwrap();
        let (tname, tag, _) = &save.trailer;
        assert_eq!(tname, "BUNK", "{name}");
        assert_eq!(tag, "NETA", "{name}");
    }
}

/// The develop differential: the `game03` save was taken after developing exactly
/// one Arsenal weapon (Light Machine Gun MG I, 4000 P) from the `game02` state.
/// Exactly three things moved, and this is what gave the blob its alphabet.
#[test]
fn developing_one_weapon_moves_points_ratio_and_two_blob_entries() {
    let before = savegame::parse(&sample("savedata-game02-samestate.bin")).unwrap();
    let after = savegame::parse(&sample("savedata-game03-developed-mg1.bin")).unwrap();

    // Points fell by the item's 4000 P cost — and +28 did NOT move, which is what
    // separates the spendable balance from its twin.
    let (p0, p1) = (before.points().unwrap(), after.points().unwrap());
    assert_eq!(p0 - p1, 4000, "Points should fall by the 4000 P cost");
    let twin = |s: &savegame::SaveGame| {
        savegame::GHAD_LAYOUT
            .iter()
            .find(|f| f.offset == 28)
            .and_then(|f| s.ghad_value(f))
            .unwrap()
    };
    assert_eq!(twin(&before), twin(&after), "+28 must not move on a spend");

    // The clear ratio counts collection, not only stages.
    assert_eq!(
        after.clear_ratio_pct().unwrap(),
        before.clear_ratio_pct().unwrap() + 1
    );

    // Blob: the bought item became developed, its successor became developable.
    let (b, a) = (before.develop_state(), after.develop_state());
    let moved: Vec<usize> = (0..b.len()).filter(|&i| b[i] != a[i]).collect();
    assert_eq!(moved.len(), 2, "exactly two blob entries move, got {moved:?}");
    assert_eq!(a[moved[0]], DevelopState::Developed);
    assert_eq!(a[moved[1]], DevelopState::Developable);
}

/// The two saves of the same state differ only in the header (its FILETIME and
/// the uninitialised pointer padding) — the payload is a pure function of game
/// state.
#[test]
fn payload_is_a_pure_function_of_game_state() {
    let a = savegame::parse(&sample("savedata-game02-samestate.bin")).unwrap();
    let b = savegame::parse(&sample("savedata-stage02-5pct.bin")).unwrap();
    assert_eq!(
        a.payload, b.payload,
        "the same state saved twice must deflate to the same payload"
    );
}

/// The summary copy the Details panel reads must agree with the payload it
/// mirrors — the two are written together, and a disagreement is what a
/// payload-only edit produces.
#[test]
fn header_summary_agrees_with_the_payload_it_mirrors() {
    for name in SAMPLES {
        let save = savegame::parse(&sample(name)).unwrap();
        for m in save.header.summary() {
            let Some(goff) = m.ghad_offset else { continue };
            let spec = savegame::GHAD_LAYOUT
                .iter()
                .find(|f| f.offset == goff)
                .expect("mirror names a real GHAD field");
            let payload_value = save.ghad_value(spec).unwrap();
            assert_eq!(
                u64::from(m.value),
                payload_value,
                "{name}: header {:#x} ({}) disagrees with GHAD +{}",
                m.header_offset,
                m.name,
                goff
            );
        }
    }
}

/// The eleven still-unknown GHAD fields are a documented fact, not an oversight.
/// If a future session names one, this count moves — deliberately.
#[test]
fn unknown_fields_are_still_declared_unknown() {
    let unknown = savegame::GHAD_LAYOUT
        .iter()
        .filter(|f| f.confidence == Confidence::Unknown)
        .count();
    let refuted = savegame::GHAD_LAYOUT
        .iter()
        .filter(|f| f.confidence == Confidence::Refuted)
        .count();
    assert_eq!(unknown, 7, "unknown GHAD fields");
    assert_eq!(refuted, 2, "fields tested and refuted (+36, +56)");
}