# Dynamic Shell Autocompletion for Artists/Albums/Tracks

## Problem

`rsp play <query>` and `rsp queue <query>` accept freeform strings. No tab-completion for artists, albums, or tracks from the SQLite library DB. User must type full path or query blindly.

## Approach: Direct DB read (no daemon dependency)

Hidden CLI subcommand `rsp complete <entity> [prefix]` that:
1. Opens DB directly (same as `rsp scan` at cli.rs:204-205)
2. Queries with prefix match
3. Prints newline-separated results to stdout
4. Returns empty on error (never crash completion)

Works with or without daemon running. SQLite prefix query is ~1ms.

## Steps

### 1. Add completion query methods to `Database` (`src/database.rs`)

```
pub fn complete_artists(&self, prefix: &str) -> SqlResult<Vec<String>>
pub fn complete_albums(&self, prefix: &str) -> SqlResult<Vec<String>>
pub fn complete_tracks(&self, prefix: &str) -> SqlResult<Vec<String>>
```

SQL:
- artists: `SELECT name FROM artists WHERE name LIKE ? ORDER BY name`
- albums: `SELECT title FROM albums WHERE title LIKE ? ORDER BY title`
- tracks: `SELECT title FROM tracks WHERE title LIKE ? ORDER BY title`

Prefix `"a"` → `LIKE 'a%'`. Limit results (e.g. 25).

### 2. Add hidden `DbComplete` subcommand (`src/cli.rs`)

```
#[clap(hide = true)]
DbComplete {
    entity: String,  // "artists", "albums", "tracks"
    prefix: Option<String>,
}
```

Dispatch in `Cli::run()`:
```
Commands::DbComplete { entity, prefix } => {
    let config = Config::load()?;
    let db = Database::open(&config)?;
    let results = match entity.as_str() { ... };
    for r in results { println!("{r}"); }
}
```

Errors → silent empty (stderr) so completion never breaks.

### 3. Filter `DbComplete` out of generated completions (like `Completions`)

In `Completions` generation (cli.rs:238-253): filter `s.get_name() != "db-complete"`.

### 4. Dynamic zsh completion function

Replace `/usr/share/zsh/site-functions/_rsp` with a wrapper that:

```zsh
#compdef rsp
# Static part (generated by clap)
_rsp_command() { ... }  # clap-generated

# Dynamic overrides
_rsp() {
  case $line[1] in
    play|queue)
      if compset -P 1; then
        # Subcommand → complete tracks/artists/albums
        local -a suggestions
        suggestions=(${(f)"$(rsp complete tracks "$words[CURRENT]")"})
        suggestions+=(${(f)"$(rsp complete artists "$words[CURRENT]")"})
        suggestions+=(${(f)"$(rsp complete albums "$words[CURRENT]")"})
        compadd -a suggestions
      else
        _rsp_command
      fi
      ;;
    *)
      _rsp_command
      ;;
  esac
}
```

For `play <query>`, complete artists + albums + tracks.
Where artists have the biggest priority, then comes albums and at the end tracks.
Additionally, when we have autocompleted an artist, put a '/' after the name. Next autocompletions will autocomplete albums/tracks, do the same for albums.

### 5. Update `Completions` generation to produce the wrapper

In `cli.rs`, after `generate()` for zsh, append the dynamic wrapper code. The generated file becomes: `clap-generated-code` + `_rsp() { ... dynamic ... }`.

Or simpler: write the wrapper as `completions/_rsp.dynamic` and concatenate in install.sh.

### 6. Update `install.sh`

Replace `rsp completions zsh | sudo tee ...` with:
```bash
(rsp completions zsh; echo; cat completions/_rsp) | sudo tee "$dest"
```

### 7. Update `TODO.md`

Mark "[x] Dynamic autocompletion of artists, albums and tracks"

### 8. Tests

Add tests in `tests/database.rs`:
- `test_complete_artists_prefix`
- `test_complete_albums_prefix`
- `test_complete_tracks_prefix`
- `test_complete_empty_db`
- `test_complete_no_match`

Need a test helper that creates a temp DB with known data, runs queries, checks results.

## Files changed

| File | Change |
|------|--------|
| `src/database.rs` | +3 pub methods (complete_artists/albums/tracks) |
| `src/cli.rs` | +DbComplete variant, +dispatch, +filter in Completions |
| `completions/_rsp.dynamic` (new) | zsh dynamic completion wrapper |
| `install.sh` | concatenate static + dynamic |
| `tests/database.rs` | +completion query tests |

## Future: fish/bash

Same pattern. Fish uses `complete -c rsp -n '__fish_seen_subcommand_from play' -a '(rsp complete tracks (commandline -ct))'`. Bash uses `COMPREPLY=($(compgen -W "$(rsp complete tracks "$cur")" -- "$cur"))`. Start with zsh only (user's shell).