//! Golden-file test for ClawOnion v1 binary format.
//!
//! Asserts that a minimal `.onion` file serialises to exact byte values at
//! every spec-defined offset.  This test exists solely to catch **silent
//! `zerocopy` layout regressions** — if any struct field shifts by even one
//! byte, at least one assertion below will fire.
//!
//! The test vector matches §13 of `CLAWONION_SPEC.md`:
//!   - 1 revision (rev 0) on branch `main`
//!   - 1 page at `h5_offset = 0`, 4 096 bytes, filled with `0xAB`
//!   - No revision annotation
//!
//! All offsets are little-endian (LE) as per the spec.

use clawhdf5_onion::format::Codec;
use clawhdf5_onion::writer::OnionFile;
use tempfile::NamedTempFile;

// ─────────────────────────────────────────────────────────────────────────────
// Layout constants (must match CLAWONION_SPEC.md §2 + §3)
// ─────────────────────────────────────────────────────────────────────────────

const HEADER_SIZE: usize = 128;
const REV_ENTRY_SIZE: usize = 112;
const BRANCH_ENTRY_SIZE: usize = 40;
const PAGE_ENTRY_SIZE: usize = 32;
const PAGE_SIZE: u32 = 4096;

const INDEX_OFFSET: usize = HEADER_SIZE; // 128
const BRANCH_OFFSET: usize = INDEX_OFFSET + REV_ENTRY_SIZE; // 240
const PT_OFFSET: usize = BRANCH_OFFSET + BRANCH_ENTRY_SIZE; // 280
const PD_OFFSET: usize = PT_OFFSET + PAGE_ENTRY_SIZE; // 312

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

fn le64(v: u64) -> [u8; 8] {
    v.to_le_bytes()
}
fn le32(v: u32) -> [u8; 4] {
    v.to_le_bytes()
}

/// Build the expected BLAKE3 for one 4096-byte page of 0xAB at h5_offset = 0.
///
/// Algorithm from spec §5:
///   hasher.update(h5_offset.to_le_bytes())
///   hasher.update(uncompressed_page_data)
fn expected_blake3(page_bytes: &[u8]) -> [u8; 32] {
    let mut h = blake3::Hasher::new();
    h.update(&0u64.to_le_bytes()); // h5_offset = 0
    h.update(page_bytes);
    *h.finalize().as_bytes()
}

// ─────────────────────────────────────────────────────────────────────────────
// Golden test
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn golden_minimal_onion_byte_layout() {
    // ── Build the test vector ────────────────────────────────────────────────

    let _tmp = NamedTempFile::new().unwrap();
    let h5_path = _tmp.path().with_extension("h5");
    let base_bytes = b"\x89HDF\r\n\x1a\n".to_vec();
    std::fs::write(&h5_path, &base_bytes).unwrap();

    let mut onion = OnionFile::create(&h5_path, PAGE_SIZE).unwrap();

    // Use Codec::None so data_size == orig_size and page data is unambiguous.
    // This also matches the §13 spec test vector which specifies codec = None.
    onion.set_codec(Codec::None);

    let page_bytes = vec![0xABu8; PAGE_SIZE as usize];
    let mut session = onion.begin_session(None).unwrap();
    session.record_page(0, &page_bytes);
    onion.commit_session(session, None).unwrap();

    let bytes = onion.to_bytes().unwrap();

    // ── Verify total file size ───────────────────────────────────────────────
    // Header(128) + RevisionEntry(112) + BranchEntry(40) + PageTableEntry(32)
    // + PageData(4096) + AnnotationHeap(9)
    let ann_heap: &[u8] = &[0x00, 0x04, 0x00, 0x00, 0x00, b'm', b'a', b'i', b'n'];
    let expected_total = PD_OFFSET + PAGE_SIZE as usize + ann_heap.len(); // 4417
    assert_eq!(
        bytes.len(),
        expected_total,
        "total file size mismatch (got {}, expected {expected_total})",
        bytes.len()
    );

    // ══════════════════════════════════════════════════════════════════════════
    // §3.1 OnionHeader — 128 bytes @ offset 0
    // ══════════════════════════════════════════════════════════════════════════

    // [0..9] magic
    assert_eq!(&bytes[0..9], b"CLAWONION", "magic mismatch");

    // [9] format_version
    assert_eq!(bytes[9], 0x01, "format_version");

    // [10..16] _pad_align — must be zero
    assert_eq!(&bytes[10..16], &[0u8; 6], "_pad_align must be zero");

    // [16..24] feature_flags = 0x07 (COMPRESSION | BRANCHING | PROVENANCE)
    assert_eq!(&bytes[16..24], &le64(0x07), "feature_flags");

    // [24..28] page_size = 4096
    assert_eq!(&bytes[24..28], &le32(4096), "page_size");

    // [28..32] _pad_ps — must be zero
    assert_eq!(&bytes[28..32], &[0u8; 4], "_pad_ps must be zero");

    // [32..40] revision_count = 1
    assert_eq!(&bytes[32..40], &le64(1), "revision_count");

    // [40..44] branch_count = 1
    assert_eq!(&bytes[40..44], &le32(1), "branch_count");

    // [44..48] _pad_bc — must be zero
    assert_eq!(&bytes[44..48], &[0u8; 4], "_pad_bc must be zero");

    // [48..56] index_offset = 128
    assert_eq!(&bytes[48..56], &le64(128), "index_offset");

    // [56..64] branch_offset = 240
    assert_eq!(&bytes[56..64], &le64(240), "branch_offset");

    // [64..72] created_at — f64, time-dependent; skip exact value check,
    //          but assert it's non-zero (a real Unix timestamp).
    let created_at = f64::from_le_bytes(bytes[64..72].try_into().unwrap());
    assert!(
        created_at > 0.0,
        "created_at should be a positive Unix timestamp"
    );

    // [72..128] reserved — 56 bytes, must all be zero
    assert_eq!(
        &bytes[72..128],
        &[0u8; 56],
        "reserved header bytes must be zero"
    );

    // ══════════════════════════════════════════════════════════════════════════
    // §3.2 RevisionEntry — 112 bytes @ offset 128
    // ══════════════════════════════════════════════════════════════════════════

    let re = INDEX_OFFSET; // 128

    // [re+0..re+8] revision = 0
    assert_eq!(&bytes[re..re + 8], &le64(0), "revision number");

    // [re+8..re+12] branch_id = 0 (main)
    assert_eq!(&bytes[re + 8..re + 12], &le32(0), "branch_id");

    // [re+12..re+16] _pad_bi — must be zero
    assert_eq!(&bytes[re + 12..re + 16], &[0u8; 4], "_pad_bi must be zero");

    // [re+16..re+24] parent_rev = u64::MAX (root has no parent)
    assert_eq!(
        &bytes[re + 16..re + 24],
        &le64(u64::MAX),
        "parent_rev (NO_PARENT sentinel)"
    );

    // [re+24..re+28] page_count = 1
    assert_eq!(&bytes[re + 24..re + 28], &le32(1), "page_count");

    // [re+28..re+32] _pad_pc — must be zero
    assert_eq!(&bytes[re + 28..re + 32], &[0u8; 4], "_pad_pc must be zero");

    // [re+32..re+40] page_table_off = 280 (PT_OFFSET)
    assert_eq!(
        &bytes[re + 32..re + 40],
        &le64(PT_OFFSET as u64),
        "page_table_off"
    );

    // [re+40..re+48] timestamp — f64, time-dependent; assert positive
    let ts = f64::from_le_bytes(bytes[re + 40..re + 48].try_into().unwrap());
    assert!(ts > 0.0, "revision timestamp should be positive");

    // [re+48..re+80] blake3 — verify against spec §5 algorithm
    let computed_blake3 = expected_blake3(&page_bytes);
    assert_eq!(
        &bytes[re + 48..re + 80],
        &computed_blake3,
        "BLAKE3 hash mismatch"
    );

    // [re+80..re+96] session_uuid — 16 bytes UUIDv7; must be non-zero
    assert_ne!(
        &bytes[re + 80..re + 96],
        &[0u8; 16],
        "session_uuid must not be all zeros"
    );

    // [re+96..re+104] annotation_off = 0 (no annotation)
    assert_eq!(
        &bytes[re + 96..re + 104],
        &le64(0),
        "annotation_off must be 0 (no annotation)"
    );

    // [re+104] flags = 0 (not a snapshot)
    assert_eq!(bytes[re + 104], 0x00, "revision flags");

    // [re+105..re+112] _pad_flags — must be zero
    assert_eq!(
        &bytes[re + 105..re + 112],
        &[0u8; 7],
        "_pad_flags must be zero"
    );

    // ══════════════════════════════════════════════════════════════════════════
    // §3.3 BranchEntry — 40 bytes @ offset 240
    // ══════════════════════════════════════════════════════════════════════════

    let be = BRANCH_OFFSET; // 240

    // [be+0..be+4] id = 0 (main)
    assert_eq!(&bytes[be..be + 4], &le32(0), "branch id");

    // [be+4..be+8] _pad_id — must be zero
    assert_eq!(&bytes[be + 4..be + 8], &[0u8; 4], "_pad_id must be zero");

    // [be+8..be+16] name_off = 1 (heap-relative; first string after reserved null)
    assert_eq!(
        &bytes[be + 8..be + 16],
        &le64(1),
        "name_off for main branch"
    );

    // [be+16..be+24] head_rev = 0 (updated after commit)
    assert_eq!(
        &bytes[be + 16..be + 24],
        &le64(0),
        "head_rev after first commit"
    );

    // [be+24..be+32] fork_rev = u64::MAX (main is not forked)
    assert_eq!(
        &bytes[be + 24..be + 32],
        &le64(u64::MAX),
        "fork_rev (NO_PARENT for main)"
    );

    // [be+32..be+40] created_at — f64, time-dependent; assert positive
    let branch_ts = f64::from_le_bytes(bytes[be + 32..be + 40].try_into().unwrap());
    assert!(branch_ts > 0.0, "branch created_at should be positive");

    // ══════════════════════════════════════════════════════════════════════════
    // §3.4 PageTableEntry — 32 bytes @ offset 280
    // ══════════════════════════════════════════════════════════════════════════

    let pt = PT_OFFSET; // 280

    // [pt+0..pt+8] h5_offset = 0
    assert_eq!(&bytes[pt..pt + 8], &le64(0), "h5_offset");

    // [pt+8..pt+16] data_offset = 312 (PD_OFFSET, absolute file position)
    assert_eq!(
        &bytes[pt + 8..pt + 16],
        &le64(PD_OFFSET as u64),
        "data_offset (absolute)"
    );

    // [pt+16..pt+20] orig_size = 4096
    assert_eq!(&bytes[pt + 16..pt + 20], &le32(4096), "orig_size");

    // [pt+20..pt+24] data_size = 4096 (codec=None → no compression)
    assert_eq!(
        &bytes[pt + 20..pt + 24],
        &le32(4096),
        "data_size (codec=None, uncompressed)"
    );

    // [pt+24] codec = 0 (None)
    assert_eq!(bytes[pt + 24], 0x00, "codec = None (0)");

    // [pt+25..pt+32] _pad — must be zero
    assert_eq!(&bytes[pt + 25..pt + 32], &[0u8; 7], "_pad must be zero");

    // ══════════════════════════════════════════════════════════════════════════
    // PageData — 4096 bytes @ offset 312
    // ══════════════════════════════════════════════════════════════════════════

    assert_eq!(
        &bytes[PD_OFFSET..PD_OFFSET + 4096],
        page_bytes.as_slice(),
        "page data must equal the uncompressed original bytes"
    );

    // ══════════════════════════════════════════════════════════════════════════
    // §3.5 AnnotationHeap — tail of file
    // ══════════════════════════════════════════════════════════════════════════

    // Last 9 bytes: [0x00 reserved] [u32 LE length=4] ["main"]
    assert_eq!(
        &bytes[bytes.len() - 9..],
        ann_heap,
        "annotation heap content"
    );

    // ══════════════════════════════════════════════════════════════════════════
    // §7 Reconstruction — verify round-trip
    // ══════════════════════════════════════════════════════════════════════════

    let reconstructed = onion.reconstruct_revision(0, &base_bytes).unwrap();
    assert_eq!(
        &reconstructed[..PAGE_SIZE as usize],
        page_bytes.as_slice(),
        "reconstruct_revision must reproduce the original page"
    );
}

// ─────────────────────────────────────────────────────────────────────────────
// Byte-exact format freeze — §13 canonical test vector
// ─────────────────────────────────────────────────────────────────────────────
//
// This test builds the COMPLETE expected byte buffer from pure spec knowledge,
// then compares it against the actual serialised output byte-for-byte.
//
// Dynamic fields (wall-clock timestamps, UUIDs) are zeroed in BOTH buffers
// before the comparison — this preserves the freeze property for all layout
// fields while remaining deterministic.
//
// This complements `golden_minimal_onion_byte_layout` (which checks individual
// fields) by catching any bytes in between that neither test checks explicitly.

#[test]
fn byte_exact_format_freeze() {
    let re = INDEX_OFFSET; // 128 — RevisionEntry start
    let be = BRANCH_OFFSET; // 240 — BranchEntry start
    let pt = PT_OFFSET; // 280 — PageTableEntry start
    let pd = PD_OFFSET; // 312 — PageData start

    // ── Build the actual serialised file ────────────────────────────────────

    let _tmp = NamedTempFile::new().unwrap();
    let h5_path = _tmp.path().with_extension("h5");
    std::fs::write(&h5_path, b"\x89HDF\r\n\x1a\n").unwrap();

    let mut onion = OnionFile::create(&h5_path, PAGE_SIZE).unwrap();
    onion.set_codec(Codec::None);

    let page_bytes = vec![0xABu8; PAGE_SIZE as usize];
    let mut session = onion.begin_session(None).unwrap();
    session.record_page(0, &page_bytes);
    onion.commit_session(session, None).unwrap();

    let mut actual = onion.to_bytes().unwrap();

    // ── Build the expected buffer from spec ──────────────────────────────────

    let ann_heap: &[u8] = &[0x00, 0x04, 0x00, 0x00, 0x00, b'm', b'a', b'i', b'n'];
    let total = pd + PAGE_SIZE as usize + ann_heap.len(); // 4417
    let mut expected = vec![0u8; total];

    // §3.1 OnionHeader (128 bytes)
    expected[0..9].copy_from_slice(b"CLAWONION"); // magic
    expected[9] = 0x01; // format_version
    // [10..16]  = 0 (_pad_align)
    expected[16..24].copy_from_slice(&le64(0x07)); // feature_flags
    expected[24..28].copy_from_slice(&le32(4096)); // page_size
    // [28..32]  = 0 (_pad_ps)
    expected[32..40].copy_from_slice(&le64(1)); // revision_count = 1
    expected[40..44].copy_from_slice(&le32(1)); // branch_count = 1
    // [44..48]  = 0 (_pad_bc)
    expected[48..56].copy_from_slice(&le64(128)); // index_offset
    expected[56..64].copy_from_slice(&le64(240)); // branch_offset
    // [64..72]  = 0 (created_at — zeroed, dynamic)
    // [72..128] = 0 (reserved)

    // §3.2 RevisionEntry (112 bytes @ 128)
    expected[re..re + 8].copy_from_slice(&le64(0)); // revision = 0
    expected[re + 8..re + 12].copy_from_slice(&le32(0)); // branch_id = 0
    // [re+12..re+16] = 0 (_pad_bi)
    expected[re + 16..re + 24].copy_from_slice(&le64(u64::MAX)); // parent_rev = NO_PARENT
    expected[re + 24..re + 28].copy_from_slice(&le32(1)); // page_count = 1
    // [re+28..re+32] = 0 (_pad_pc)
    expected[re + 32..re + 40].copy_from_slice(&le64(pt as u64)); // page_table_off
    // [re+40..re+48] = 0 (timestamp — zeroed, dynamic)
    expected[re + 48..re + 80].copy_from_slice(&expected_blake3(&page_bytes)); // blake3
    // [re+80..re+96] = 0 (session_uuid — zeroed, dynamic)
    // [re+96..re+104] = 0 (annotation_off = 0, no annotation)
    // [re+104] = 0 (flags = 0, not a snapshot)
    // [re+105..re+112] = 0 (_pad_flags)

    // §3.3 BranchEntry (40 bytes @ 240)
    expected[be..be + 4].copy_from_slice(&le32(0)); // id = 0 (main)
    // [be+4..be+8] = 0 (_pad_id)
    expected[be + 8..be + 16].copy_from_slice(&le64(1)); // name_off = 1 (heap offset of "main")
    expected[be + 16..be + 24].copy_from_slice(&le64(0)); // head_rev = 0
    expected[be + 24..be + 32].copy_from_slice(&le64(u64::MAX)); // fork_rev = NO_PARENT
    // [be+32..be+40] = 0 (created_at — zeroed, dynamic)

    // §3.4 PageTableEntry (32 bytes @ 280)
    expected[pt..pt + 8].copy_from_slice(&le64(0)); // h5_offset = 0
    expected[pt + 8..pt + 16].copy_from_slice(&le64(pd as u64)); // data_offset
    expected[pt + 16..pt + 20].copy_from_slice(&le32(4096)); // orig_size
    expected[pt + 20..pt + 24].copy_from_slice(&le32(4096)); // data_size (no compression)
    // [pt+24] = 0 (codec = None)
    // [pt+25..pt+32] = 0 (_pad)

    // PageData (4096 bytes @ 312)
    expected[pd..pd + 4096].fill(0xAB);

    // §3.5 AnnotationHeap (9 bytes at end)
    expected[pd + 4096..].copy_from_slice(ann_heap);

    // ── Zero dynamic fields in both buffers ──────────────────────────────────
    // OnionHeader.created_at
    actual[64..72].fill(0);
    // RevisionEntry.timestamp
    actual[re + 40..re + 48].fill(0);
    // RevisionEntry.session_uuid
    actual[re + 80..re + 96].fill(0);
    // BranchEntry.created_at
    actual[be + 32..be + 40].fill(0);

    // ── Compare byte-for-byte ────────────────────────────────────────────────
    assert_eq!(
        actual.len(),
        expected.len(),
        "total file size mismatch: actual={} expected={}",
        actual.len(),
        expected.len()
    );

    // Find the first differing byte for a useful failure message.
    if actual != expected {
        for i in 0..actual.len() {
            if actual[i] != expected[i] {
                panic!(
                    "byte mismatch at offset 0x{i:03X} ({i}): \
                     actual=0x{:02X} expected=0x{:02X}\n\
                     (fields: header=0..128, rev_entry=128..240, branch=240..280, \
                     page_table=280..312, page_data=312..4408, ann_heap=4408..4417)",
                    actual[i], expected[i]
                );
            }
        }
    }
}

// ─────────────────────────────────────────────────────────────────────────────
// Struct size guards — compile-time; here as runtime assertions too so that
// a zerocopy version bump that somehow bypasses the const asserts still fires.
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn struct_sizes_match_spec() {
    use clawhdf5_onion::format::{BranchEntry, OnionHeader, PageTableEntry, RevisionEntry};
    use std::mem::size_of;

    assert_eq!(
        size_of::<OnionHeader>(),
        128,
        "OnionHeader must be 128 bytes (§3.1)"
    );
    assert_eq!(
        size_of::<RevisionEntry>(),
        112,
        "RevisionEntry must be 112 bytes (§3.2)"
    );
    assert_eq!(
        size_of::<BranchEntry>(),
        40,
        "BranchEntry must be 40 bytes (§3.3)"
    );
    assert_eq!(
        size_of::<PageTableEntry>(),
        32,
        "PageTableEntry must be 32 bytes (§3.4)"
    );
}

// ─────────────────────────────────────────────────────────────────────────────
// Magic / version rejection — §10 conformance
// ─────────────────────────────────────────────────────────────────────────────

#[test]
fn bad_magic_is_rejected() {
    let _tmp = NamedTempFile::new().unwrap();
    let h5_path = _tmp.path().with_extension("h5");
    std::fs::write(&h5_path, b"\x89HDF\r\n\x1a\n").unwrap();

    let mut onion = OnionFile::create(&h5_path, 4096).unwrap();
    onion.set_codec(Codec::None);
    let mut s = onion.begin_session(None).unwrap();
    s.record_page(0, &vec![0u8; 4096]);
    onion.commit_session(s, None).unwrap();

    let mut bytes = onion.to_bytes().unwrap();

    // Corrupt the magic
    bytes[0] = b'X';

    let sidecar = h5_path.with_extension("h5.onion");
    std::fs::write(&sidecar, &bytes).unwrap();

    let err = OnionFile::open(&h5_path).unwrap_err();
    assert!(
        matches!(err, clawhdf5_onion::error::OnionError::InvalidMagic),
        "expected InvalidMagic, got {err:?}"
    );
}

#[test]
fn unknown_version_is_rejected() {
    let _tmp = NamedTempFile::new().unwrap();
    let h5_path = _tmp.path().with_extension("h5");
    std::fs::write(&h5_path, b"\x89HDF\r\n\x1a\n").unwrap();

    let mut onion = OnionFile::create(&h5_path, 4096).unwrap();
    onion.set_codec(Codec::None);
    let mut s = onion.begin_session(None).unwrap();
    s.record_page(0, &vec![0u8; 4096]);
    onion.commit_session(s, None).unwrap();

    let mut bytes = onion.to_bytes().unwrap();

    // Bump format_version to something unknown
    bytes[9] = 0xFF;

    let sidecar = h5_path.with_extension("h5.onion");
    std::fs::write(&sidecar, &bytes).unwrap();

    let err = OnionFile::open(&h5_path).unwrap_err();
    assert!(
        matches!(err, clawhdf5_onion::error::OnionError::UnknownVersion(0xFF)),
        "expected UnknownVersion(0xFF), got {err:?}"
    );
}