#![no_main]
//! Arbitrary bytes as a WAL file. Reading, and opening for append (which scans
//! the chain and truncates an unverifiable tail), must never panic, hang, or
//! allocate without bound — and after `open` repairs the file, everything
//! `read_entries` returned before must still be returned.
//!
//! The deterministic counterpart that runs in ordinary CI is
//! `tests/wal_properties.rs`; this target explores inputs it cannot reach.

use std::io::Write as _;

use clawhdf5_agent::wal::WalFile;
use libfuzzer_sys::fuzz_target;

fuzz_target!(|data: &[u8]| {
    let Ok(mut tmp) = tempfile::NamedTempFile::new() else {
        return;
    };
    if tmp.write_all(data).and_then(|()| tmp.flush()).is_err() {
        return;
    }
    let before = WalFile::read_entries(tmp.path()).map(|e| e.len());
    // Only the chained formats (header versions 3 and 4) are repaired in
    // place. `open` deliberately recreates a legacy-format file from scratch:
    // `HDF5Memory::open` has already replayed its entries by then.
    let chained = matches!(data.get(4), Some(3 | 4));
    let opened = WalFile::open(tmp.path());
    if !chained {
        return;
    }
    if let (Ok(before), Ok(wal)) = (before, opened) {
        drop(wal);
        let after = WalFile::read_entries(tmp.path()).map(|e| e.len());
        assert_eq!(after.ok(), Some(before), "open() changed what is replayable");
    }
});