When a file does not end with a newline, appending content extends the
last logical line's text and thus its visual height. The incremental
extend path in handle_file_appended only computed heights for newly
created logical lines, missing the old last line whose content changed.
Add VisualHeightIndex::replace_last_line_height() — an O(1) method that
rewrites the final prefix sum entry and total. Called before
extend_from_heights so the correct line is targeted.
Changes:
- progressive_reader.rs: add replace_last_line_height, pub with_params,
7 VHI unit tests
- app.rs: save old_reader_line_count before update, recompute last old
line height in extend path, 2 integration regression tests
Background threads (spawn_indexer, spawn_visual_height_rebuild) previously
held mmap during entire file scan, risking SIGBUS if file was truncated
externally. Now uses BufReader streaming scan with mmap created only
after scan completes, plus stat validation.
Changes:
- spawn_indexer: replace mmap scan with BufReader fill_buf/consume loop,
create mmap post-scan with fd stat validation
- spawn_visual_height_rebuild: replace mmap/FileReader with sequential
BufReader scan, discard results on line count mismatch
- FileReader::open/reload/update_for_append: add stat-after-mmap check
- LineIndex: make fields pub(crate) for direct construction from scan loop
- Add 3 regression tests for truncation scenarios
spawn_indexer builds LineIndex from mmap snapshot but IndexCache::save()
re-opened the file to compute the hash. If the file changed between those
two steps, the cached index would be stored under the wrong hash.
- Add IndexCache::save_with_hash() that computes hash from in-memory data
- Add compute_data_hash() public function (same algorithm as compute_file_hash)
- Update spawn_indexer, FileReader::save_cache, and test callers
File truncation/rotation during mmap lifetime caused SIGBUS crash
because update_for_append() ignored new_size < old_size, leaving
a stale mapping that would fault on access.
Introduce AppendStatus enum (Unchanged/Appended/Reloaded) so the
caller can distinguish shrink events from normal appends. On shrink,
reload() rebuilds the mmap and line index. The TUI layer clamps
cursor and invalidates viewport cache on Reloaded, matching the
existing handle_file_truncated() behavior.
Fixes#1
Add SCAN_AHEAD_LIMIT (10000 lines) to get_line() in Sampling state. Without this, jumping to end-of-file (G) during progressive loading would scan the entire file byte-by-byte on the main thread, blocking the UI and consuming excessive memory. Lines beyond the scanned region + limit now return None, which the TUI renders as empty.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
Add ProgressiveFileReader state machine (Sampling/Ready/Error) with scanned_newlines cache for O(1) line lookups. Implement spawn_indexer() for background mmap-based indexing with cancellation and progress reporting. Add VisualHeightIndex with prefix-sum + binary search for O(log N) visual height queries. Register all new io submodules and extend FileReader with reload(), save_cache(), and accessor methods.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
