//! The audit chain verifier against the fixture logs in `tests/fixtures/audit/`. Do not edit
//! this file or the fixtures: their hashes are real, and one changed byte changes the verdict.
//!
//! Every fixture is a small audit directory. `good` is an undamaged two-day log; the others are
//! `good` with one thing done to it, named by the directory.

use proto::{AuditRecord, ChainReport, ChainVerifier, Hash32, Location, sha256};

const D1: &str = "2026-09-17.jsonl";
const D2: &str = "2026-09-18.jsonl";

fn dir(case: &str) -> String {
    format!("{}/tests/fixtures/audit/{case}", env!("CARGO_MANIFEST_DIR"))
}

/// The `.jsonl` files of a case, in name order, with their bytes.
fn files(case: &str) -> Vec<(String, Vec<u8>)> {
    let dir = dir(case);
    let mut names: Vec<String> = std::fs::read_dir(&dir)
        .unwrap_or_else(|e| panic!("{dir}: {e}"))
        .map(|entry| entry.unwrap().file_name().into_string().unwrap())
        .filter(|name| name.ends_with(".jsonl"))
        .collect();
    names.sort();
    assert!(!names.is_empty(), "{dir}: no files");
    names
        .into_iter()
        .map(|name| {
            let bytes = std::fs::read(format!("{dir}/{name}")).unwrap();
            (name, bytes)
        })
        .collect()
}

fn verify(case: &str) -> ChainReport {
    let mut verifier = ChainVerifier::new();
    for (name, bytes) in files(case) {
        verifier.feed(&name, &bytes);
    }
    verifier.finish()
}

/// Line `line` (1-based) of a file of a case, without its newline.
fn line_of(case: &str, file: &str, line: usize) -> Vec<u8> {
    let (_, bytes) = files(case)
        .into_iter()
        .find(|(name, _)| name == file)
        .unwrap();
    bytes.split(|b| *b == b'\n').nth(line - 1).unwrap().to_vec()
}

fn hash_of(case: &str, file: &str, line: usize) -> Hash32 {
    sha256(&line_of(case, file, line)).unwrap()
}

fn at(file: &str, line: u64) -> Location {
    Location {
        file: file.to_string(),
        line,
    }
}

#[test]
fn good_log_verifies() {
    let report = verify("good");
    assert_eq!(report.failure, None);
    assert_eq!(report.records, 10);
    assert_eq!(report.next_seq, 10);
    assert_eq!(report.head, Some(hash_of("good", D2, 5)));
    assert_eq!(
        report.abandoned,
        vec![6],
        "the ask at seq 6 has no approval"
    );
    assert_eq!(
        report.unfinished,
        vec![7],
        "the allowed call at seq 7 has no result"
    );
    assert!(report.recoveries.is_empty());
    assert!(report.accepted_breaks.is_empty());
    assert!(report.clock_warnings.is_empty());
    assert_eq!(report.torn_tail, None);
}

/// The tampering suite: each case fails, at this file and line, with this text.
#[test]
fn tampering_is_found_at_the_right_line() {
    let parse = "does not parse as an audit record";
    let cases = [
        // The changed line still parses and chains; the line after it no longer chains from it.
        (
            "changed-byte",
            D1,
            4,
            "prev is not the hash of the line before",
        ),
        ("deleted-line", D1, 3, "seq is 3, expected 2"),
        ("swapped-lines", D1, 2, "seq is 2, expected 1"),
        ("seq-gap", D1, 3, "seq is 3, expected 2"),
        (
            "file-not-chained",
            D2,
            1,
            "does not chain from the last line of the file before",
        ),
        ("cut-short", D1, 3, parse),
        (
            "break-wrong-line",
            D1,
            4,
            "prev is not the hash of the line before",
        ),
        (
            "break-wrong-last-good",
            D1,
            4,
            "prev is not the hash of the line before",
        ),
        (
            "break-wrong-prev",
            D1,
            4,
            "prev is not the hash of the line before",
        ),
        (
            "break-wrong-seq",
            D1,
            4,
            "prev is not the hash of the line before",
        ),
        (
            "break-without-failure",
            D2,
            6,
            "an accepted break with no failure before it",
        ),
        ("recovery-wrong-hash", D2, 6, parse),
        ("recovery-wrong-length", D2, 6, parse),
        (
            "recovery-describes-nothing",
            D2,
            6,
            "a recovery record that does not describe the line before it",
        ),
        ("torn-recovery", D2, 6, parse),
    ];
    for (case, file, line, what) in cases {
        let failure = verify(case)
            .failure
            .unwrap_or_else(|| panic!("{case}: verified, but it is damaged"));
        assert_eq!(
            (failure.file.as_str(), failure.line, failure.what.as_str()),
            (file, line, what),
            "{case}"
        );
    }
}

#[test]
fn a_failure_says_what_a_break_record_must_carry() {
    let failure = verify("changed-byte").failure.unwrap();
    assert_eq!(failure.last_good, hash_of("changed-byte", D1, 3));
    assert_eq!(failure.break_prev, hash_of("changed-byte", D2, 5));
    // The failing line should have had seq 3; seven lines run from it to the end of the log.
    assert_eq!(failure.break_seq, 10);
    assert!(!failure.tail_torn);

    // A failure at the very first line: nothing verified, so last_good is all zeros.
    let mut verifier = ChainVerifier::new();
    verifier.file(D1);
    verifier.line(b"not json", true);
    verifier.line(b"nor this", true);
    let failure = verifier.finish().failure.unwrap();
    assert_eq!(
        (failure.line, failure.last_good, failure.break_seq),
        (1, Hash32::ZERO, 2)
    );
    assert_eq!(failure.break_prev, sha256(b"nor this").unwrap());

    let failure = verify("torn-recovery").failure.unwrap();
    assert!(failure.tail_torn, "the last line has no newline");
    assert_eq!(
        failure.break_seq, 12,
        "seq 10 for line 6, and two lines to the end"
    );
}

#[test]
fn verification_stops_counting_at_a_failure() {
    let report = verify("changed-byte");
    assert_eq!(report.records, 3);
    assert_eq!(report.head, Some(hash_of("changed-byte", D1, 3)));
    assert_eq!(report.next_seq, 3);
    assert_eq!(report.torn_tail, None);
}

#[test]
fn a_torn_tail_is_not_a_failure() {
    // (case, file, line, has_newline, records, recovery_seq, file and line of the record before)
    let cases = [
        ("torn-tail", D2, 6, false, 10, 10, (D2, 5)),
        // Complete JSON that lacks only its newline is torn all the same.
        ("torn-tail-complete-json", D2, 6, false, 10, 10, (D2, 5)),
        // A crash between ending a torn line and writing its Recovery.
        ("torn-unparseable-newline", D2, 6, true, 10, 10, (D2, 5)),
        ("torn-first-line", D2, 1, false, 5, 5, (D1, 5)),
    ];
    for (case, file, line, has_newline, records, seq, before) in cases {
        let report = verify(case);
        assert_eq!(report.failure, None, "{case}");
        assert_eq!(report.records, records, "{case}");
        let torn = report
            .torn_tail
            .unwrap_or_else(|| panic!("{case}: no torn tail"));
        let bytes = line_of(case, file, line as usize);
        assert_eq!(torn.at, at(file, line), "{case}");
        assert_eq!(torn.has_newline, has_newline, "{case}");
        assert_eq!(torn.bytes, bytes.len() as u64, "{case}");
        assert_eq!(torn.sha256, sha256(&bytes).unwrap(), "{case}");
        assert_eq!(torn.recovery_seq, seq, "{case}");
        assert_eq!(
            torn.recovery_prev,
            hash_of(case, before.0, before.1),
            "{case}"
        );
        assert_eq!(
            report.next_seq, seq,
            "{case}: the torn line is not a record"
        );
    }
    let whole = line_of("torn-tail-complete-json", D2, 6);
    assert!(
        serde_json::from_slice::<AuditRecord>(&whole).is_ok(),
        "this case must be a line that parses"
    );
}

#[test]
fn an_empty_latest_file_is_fine() {
    let report = verify("empty-latest");
    assert_eq!((report.failure, report.torn_tail), (None, None));
    assert_eq!((report.records, report.next_seq), (5, 5));
}

#[test]
fn a_recovered_line_is_not_a_record_and_not_a_failure() {
    // (case, where the recovered line is, records, abandoned, unfinished)
    let cases = [
        ("recovered", at(D2, 6), 12, vec![6], vec![]),
        // The recovered line is complete JSON with seq 10; the Recovery takes seq 10 again.
        ("recovered-complete-json", at(D2, 6), 12, vec![6], vec![]),
        // Torn on one day, recovered on the next: the Recovery is in the torn line's file.
        ("recovered-next-day", at(D1, 6), 11, vec![7], vec![8]),
        ("recovered-first-line", at(D2, 1), 6, vec![], vec![]),
    ];
    for (case, recovered, records, abandoned, unfinished) in cases {
        let report = verify(case);
        assert_eq!(report.failure, None, "{case}");
        assert_eq!(report.torn_tail, None, "{case}");
        assert_eq!(report.recoveries, vec![recovered], "{case}");
        assert_eq!(report.records, records, "{case}");
        assert_eq!(report.abandoned, abandoned, "{case}");
        assert_eq!(report.unfinished, unfinished, "{case}");
        assert!(report.clock_warnings.is_empty(), "{case}");
    }
}

#[test]
fn a_clock_stepped_back_is_a_warning() {
    let report = verify("clock-back");
    assert_eq!(report.failure, None);
    assert_eq!(report.records, 11);
    assert_eq!(report.clock_warnings, vec![at(D2, 6)]);
}

#[test]
fn an_accepted_break_clears_the_failure_before_it() {
    // (case, where the break record is, records, next_seq)
    let cases = [
        ("accepted-break", at(D1, 6), 5, 7),
        ("accepted-break-older-file", at(D2, 6), 5, 12),
        // A deleted line in day 2 as well: one break covers every failure before it.
        ("accepted-break-two-failures", at(D2, 5), 4, 10),
        // A line in the region claims seq 18446744073709551615. The break's seq is counted
        // from lines, so it is 10 all the same.
        ("accepted-break-max-seq", at(D2, 6), 4, 11),
    ];
    for (case, break_at, records, next_seq) in cases {
        let report = verify(case);
        assert_eq!(report.failure, None, "{case}");
        assert_eq!(report.accepted_breaks, vec![break_at], "{case}");
        assert_eq!(report.records, records, "{case}");
        assert_eq!(report.next_seq, next_seq, "{case}");
    }
    // Records inside the region are not vouched for: the approval of seq 2 is in it.
    let report = verify("accepted-break");
    assert_eq!(report.abandoned, vec![2]);
    assert_eq!(report.unfinished, vec![6]);
}

/// A verifier that starts at the latest file cannot judge a break that names an older one. It
/// checks the break's `prev` and goes on; the full verification judges the rest.
#[test]
fn a_resumed_verifier_accepts_a_break_naming_an_earlier_file() {
    let case = "accepted-break-older-file";
    let last: AuditRecord = serde_json::from_slice(&line_of(case, D1, 5)).unwrap();
    let mut verifier = ChainVerifier::resume(last.seq + 1, hash_of(case, D1, 5));
    let (_, day2) = files(case).into_iter().nth(1).unwrap();
    verifier.feed(D2, &day2);
    let report = verifier.finish();
    assert_eq!(report.failure, None);
    assert_eq!(report.accepted_breaks, vec![at(D2, 6)]);
    assert_eq!((report.records, report.next_seq), (7, 12));

    // The same break with a wrong prev is not accepted, resumed or not.
    let mut verifier = ChainVerifier::resume(last.seq + 1, hash_of(case, D1, 5));
    let (_, day2) = files("break-wrong-prev").into_iter().nth(1).unwrap();
    verifier.feed(D2, &day2);
    assert!(verifier.finish().failure.is_some());
}

#[test]
fn resume_continues_from_the_file_before() {
    let last: AuditRecord = serde_json::from_slice(&line_of("good", D1, 5)).unwrap();
    let (_, day2) = files("good").into_iter().nth(1).unwrap();

    let mut verifier = ChainVerifier::resume(last.seq + 1, hash_of("good", D1, 5));
    verifier.feed(D2, &day2);
    let report = verifier.finish();
    assert_eq!(report.failure, None);
    assert_eq!((report.records, report.next_seq), (5, 10));

    // Resumed from the wrong hash, the first line of the file does not chain.
    let mut verifier = ChainVerifier::resume(last.seq + 1, Hash32::ZERO);
    verifier.feed(D2, &day2);
    let failure = verifier.finish().failure.unwrap();
    assert_eq!((failure.file.as_str(), failure.line), (D2, 1));
    assert_eq!(
        failure.what,
        "does not chain from the last line of the file before"
    );
    assert_eq!(
        failure.last_good,
        Hash32::ZERO,
        "the hash it was resumed with"
    );
}

/// `feed` is `file` and then `line` for each line; both ways must give the same report.
#[test]
fn feed_is_file_then_lines() {
    for case in [
        "good",
        "torn-tail",
        "recovered",
        "changed-byte",
        "empty-latest",
    ] {
        let mut verifier = ChainVerifier::new();
        for (name, bytes) in files(case) {
            verifier.file(&name);
            let mut rest: &[u8] = &bytes;
            while !rest.is_empty() {
                match rest.iter().position(|b| *b == b'\n') {
                    Some(end) => {
                        verifier.line(&rest[..end], true);
                        rest = &rest[end + 1..];
                    }
                    None => {
                        verifier.line(rest, false);
                        rest = &[];
                    }
                }
            }
        }
        assert_eq!(verifier.finish(), verify(case), "{case}");
    }
}

#[test]
fn an_empty_log_is_fine() {
    let report = ChainVerifier::new().finish();
    assert_eq!(
        (report.failure, report.torn_tail, report.head),
        (None, None, None)
    );
    assert_eq!((report.records, report.next_seq), (0, 0));
}