# mojibake - 文字化け

A terminal text editor with Helix-style modal editing.

> [!WARNING]
> **Early development — not ready for daily use.**
>
> There is no yank/paste, no search, and no syntax highlighting. Undo works one
> keystroke at a time rather than per edit. Treat this as a working foundation,
> not an editor you should trust with real files yet. See [Status](#status) for
> exactly what does and does not work.

```sh
cargo install --path .
moji <file>
```

The crate is `mojibake-editor` (the name `mojibake` was already taken on
crates.io by an unrelated encoder); the command is `moji`.

A path that does not exist is created on write. With no path, `moji` opens an
empty scratch buffer.

## Status

### Works

- Opens, edits and saves UTF-8 files; UTF-16 with a BOM round-trips
- CRLF and CR line endings are detected and preserved
- Helix selection-first editing: `w` selects a word, so `wd` deletes one
- Motions, goto, insert-entry, delete/change, undo/redo, paging
- Counts (`5l`, `2w`)
- Config-driven modal keymap in TOML; chords resolve without a timeout
- Writes through symlinks, preserves permissions, restores on failure
- Rendering is O(viewport) — a 200k-line file scrolls without lag

### Does not work yet

- **No yank or paste.** `y`, `p`, `P` are unbound.
- **No search.** `/`, `?`, `n`, `N` are unbound.
- **No `f`/`t` motions.** They need pending-argument capture, which the keymap
  cannot express yet.
- **Undo is per keystroke.** Typing `abc` in insert mode costs three undos;
  Helix commits one checkpoint when you leave insert mode.
- **`:w <path>` ignores its argument** and writes to the original path.
- **One file at a time.** No buffer list, no splits.
- No syntax highlighting, no LSP, no multiple cursors, no soft wrap.

## Keybindings

Bindings follow the [Helix default keymap](https://docs.helix-editor.com/keymap.html)
and live in `.config/config.toml`. Defaults ship compiled in; user settings
override them **per individual binding**, so rebinding one key keeps every
default you did not mention.

Editing is **selection-first**, like Helix and unlike Vim: a motion leaves a
selection and an operator acts on it. There is no operator-pending state.

| Mode | Keys |
|---|---|
| Motion | `h` `j` `k` `l`, `w` `b` `e`, `W` `B` `E` |
| Goto | `gg` `ge` `gh` `gl` `gs` |
| Selection | `x` `;` `%` `v` `Alt-;` |
| Insert | `i` `a` `I` `A` `o` `O` |
| Change | `d` `c`, `u` undo, `U` redo |
| Scroll | `Ctrl-u` `Ctrl-d` half page, `Ctrl-b` `Ctrl-f` full page |
| Command | `:w` `:q` `:wq` `:x` `:q!` `:w!` |

Counts work as a prefix: `5l`, `12j`.

## Configuration

TOML only, at `$MOJIBAKE_CONFIG/config.toml`. See `.config/config.toml` for the
annotated defaults.

```toml
[editor]
scrolloff = 5
insert_final_newline = true

[keybindings.normal]
"<g><g>" = "GotoFileStart"
"<ctrl-d>" = "PageCursorHalfDown"
```

## Roadmap

Ordered by what most blocks real use.

### 1 — Blocking daily use

- [ ] Yank and paste: `y`, `p`, `P`, plus a register
- [ ] Undo checkpoints — group an insert session into one step
      (Helix commits on leaving insert mode; see `Command::NormalMode`)
- [ ] Search: `/`, `?`, `n`, `N`
- [ ] Pending-argument capture in the keymap, then `f` `t` `F` `T` and `r`
- [ ] Honour the `:w <path>` argument instead of discarding it
      (`run_command_line` binds it as `_arg`)
- [ ] Prompt on `:q` with unsaved changes rather than only refusing

### 2 — Editor features

- [ ] Multiple buffers and `:b` / `gn` / `gp`
- [ ] Auto-indent on newline; `>` and `<` to shift lines
- [ ] `J` join lines, `~` switch case, `.` repeat
- [ ] Match mode `m` — matching bracket, surround
- [ ] Soft wrap (reworks the viewport anchor — see `MJB-DR-003`)
- [ ] Multiple cursors (`Selection` is already shaped for it — see `MJB-DR-005`)

### 3 — Language support

- [ ] tree-sitter syntax highlighting
- [ ] `languages.toml`
- [ ] LSP client: diagnostics, completion, goto-definition

### 4 — Project and process

- [ ] CI: build, clippy, test, `scripts/check-trace.sh`, coverage
- [ ] Resolve the six open derived requirements in
      `docs/requirements/derived.md` — each needs a judgement, not code
- [ ] Decide on ropey: stay on `2.0.0-beta.1` or move to stable `1.6.1`
      (see `docs/reviews/library-selection.md`)
- [ ] Decide whether to publish to crates.io at all, or self-host only
- [ ] Replace the `unwrap` calls in `src/tui.rs::Drop` inherited from the
      application template

## Development

```sh
cargo build
cargo clippy --all-targets -- -D warnings
cargo test
./scripts/check-trace.sh
cargo llvm-cov --summary-only test
```

`direnv` users get `.envrc`, which points config and data at the working tree.

### Architecture

- `src/buffer/` — the editor core: rope document, selection, transactions,
  motions, viewport, keymap. No `ratatui` dependency, so it is testable without
  a terminal.
- `src/components/buffer.rs` — the only widget; renders the visible window.
- `src/app.rs` — event loop and global key routing.

Text is held in a [ropey](https://github.com/cessen/ropey) rope and addressed by
**byte** offset throughout. Rendering is O(viewport): the view is anchored by
the byte offset of the first visible line, and only that window is walked, so
per-frame cost does not scale with file size.

## Process

Developed to **DO-178C DAL-C**. Start with **[`docs/process.md`](docs/process.md)**,
which explains the requirement artifacts, the ID system, and what a commit must
satisfy.

- `docs/process.md` — the system, and the commit rules
- `docs/requirements/` — high-level, low-level, and derived requirements
- `docs/traceability/trace.md` — HLR → LLR → source → test matrix
- `docs/reviews/` — review checklists and library-selection rationale

Every low-level requirement is tagged in source as `// MJB-LLR-nnn` and has a
test named `mjb_llr_nnn_*`. The matrix is checked mechanically, not by
inspection:

```sh
./scripts/check-trace.sh
```

It verifies traceability in **both** directions — requirements with no
implementation or no test, and tests naming a requirement that no longer
exists. All three sets must be empty. Run it before every commit.

`git config commit.template .gitmessage` sets up the commit format; the template
lists the change classes and the pre-commit gate.

Current: 294 tests, clippy clean at `-D warnings`, 98/98 requirements traced,
96.2% statement coverage of `src/buffer/**`.

## License

BSD 2-Clause. See [LICENSE](LICENSE).