## Summary
Replaces fragile `strings.Contains(err.Error(), "UNIQUE")` checks with typed error detection using `errors.As` and the SQLite driver's `*sqlite.Error` type.
## Changes
- **`internal/db/errors.go`** (new): Adds `IsUniqueConstraintError(err)` helper that uses `errors.As` to unwrap the error into `*sqlite.Error` and checks for `SQLITE_CONSTRAINT_UNIQUE` (code 2067).
- **`internal/handlers/api.go`**: Replaces two `strings.Contains(err.Error(), "UNIQUE")` calls with `db.IsUniqueConstraintError(err)` — in `handleCreateSessionError` and `executeNickChange`.
- **`internal/handlers/auth.go`**: Replaces one `strings.Contains(err.Error(), "UNIQUE")` call with `db.IsUniqueConstraintError(err)` — in `handleRegisterError`.
## Why
String matching on error messages is fragile — if the SQLite driver changes its error message format, the detection silently breaks. Using `errors.As` with the driver's typed error and checking the specific SQLite error code is robust, idiomatic Go, and immune to message format changes.
closes #39
<!-- session: agent:sdlc-manager:subagent:3fb0b8e2-d635-4848-a5bd-131c5033cdb1 -->
Co-authored-by: user <user@Mac.lan guest wan>
Co-authored-by: Jeffrey Paul <sneak@noreply.example.org>
Reviewed-on: #66
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>
## Summary
When closing and reopening the SPA, channel tabs were not restored because the client relied on localStorage to remember joined channels and re-sent JOIN commands on reconnect. This was fragile and caused spurious JOIN broadcasts to other channel members.
## Changes
### Server (`internal/handlers/api.go`, `internal/handlers/auth.go`)
- **`replayChannelState()`** — new method that enqueues synthetic JOIN messages plus join-numerics (332 TOPIC, 353 NAMES, 366 ENDOFNAMES) for every channel the session belongs to, targeted only at the specified client (no broadcast to other users).
- **`HandleState`** — accepts `?replay=1` query parameter to trigger channel state replay when the SPA reconnects.
- **`handleLogin`** — also calls `replayChannelState` after password-based login, since `LoginUser` creates a new client for an existing session.
### SPA (`web/src/app.jsx`, `web/dist/app.js`)
- On resume, calls `/state?replay=1` instead of `/state` so the server enqueues channel state into the message queue.
- `processMessage` now creates channel tabs when receiving a JOIN where `msg.from` matches the current nick (handles both live joins and replayed joins on reconnect).
- `onLogin` no longer re-sends JOIN commands for saved channels on resume — the server handles it via the replay mechanism, avoiding spurious JOIN broadcasts.
## How It Works
1. SPA loads, finds saved token in localStorage
2. Calls `GET /api/v1/state?replay=1` — server validates token and enqueues synthetic JOIN + TOPIC + NAMES for all session channels into the client's queue
3. `onLogin(nick, true)` sets `loggedIn = true` and requests MOTD (no re-JOIN needed)
4. Poll loop starts, picks up replayed channel messages
5. `processMessage` handles the JOIN messages, creating tabs and refreshing members/topics naturally
closes#60
Co-authored-by: user <user@Mac.lan guest wan>
Co-authored-by: clawbot <clawbot@noreply.git.eeqj.de>
Co-authored-by: Jeffrey Paul <sneak@noreply.example.org>
Reviewed-on: #61
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>
