# LINE EBA Adapter

## Structure

LINE is migrated into `src/langbot/pkg/platform/adapters/line/` with the standard EBA adapter layout:

- `adapter.py` owns lifecycle, unified webhook handling, signature verification, listener dispatch, and outbound send/reply.
- `event_converter.py` maps LINE webhook events to `message.received`, `message.deleted`, group membership events, and `platform.specific`.
- `message_converter.py` maps common `MessageChain` components to LINE message objects and maps inbound LINE text/image/voice payloads back to EBA components.
- `api_impl.py` implements the optional common APIs against the LINE Messaging API.
- `platform_api.py` declares the safe LINE-specific pass-through actions.
- `manifest.yaml` declares `line-omni`.

The legacy `src/langbot/pkg/platform/sources/line.py` adapter is kept unchanged.

Request handling reuses the proven behaviour of the legacy adapter: `WebhookParser` verifies `X-Line-Signature`, the webhook acknowledges immediately, and each event is converted and dispatched in a background task.

## Configuration

| Field | Required | Notes |
|-------|----------|-------|
| `webhook_url` | No | Generated by LangBot. Paste it into the LINE Developers console and enable "Use webhook". |
| `channel_access_token` | Yes | Long-lived channel access token, used for all outbound calls. |
| `channel_secret` | Yes | Channel secret, used to verify `X-Line-Signature`. |

`bot_account_id` is resolved through `get_bot_info` on startup and is used to drop the adapter's own messages.

## Events

| Event | Notes |
|-------|-------|
| `message.received` | Text, image, voice, and other message types. Group and room chats are mapped to group chat identity. LINE mentions become `At` components. |
| `message.deleted` | Emitted for LINE `unsend` events. |
| `group.member_joined` | Emitted for `memberJoined`; the first listed member is the event subject. |
| `group.member_left` | Emitted for `memberLeft`. |
| `bot.invited_to_group` | Emitted when the Official Account joins a group or room (`join`). |
| `bot.removed_from_group` | Emitted when the Official Account leaves (`leave`). |
| `platform.specific` | `line.follow`, `line.unfollow`, `line.postback`, `line.beacon`, and any other LINE event type, with `chat_id` in `data`. |

Legacy pipeline bindings still receive `FriendMessage` / `GroupMessage`; the adapter converts the unified event for them.

## Common APIs

Required:

- `send_message`
- `reply_message`

Optional:

- `get_user_info`
- `get_group_info`
- `leave_group`
- `call_platform_api`

`reply_message` uses the event's reply token and falls back to `push_message` when the token is rejected or already used, so multi-message answers still arrive.

## Platform APIs

| Action | Notes |
|--------|-------|
| `get_bot_info` | Returns the Official Account profile. |
| `get_profile` | Calls `get_profile` for a user id. |
| `get_group_summary` | Calls `get_group_summary` for a group id. |

## Known Limits

- LINE has no group member listing API, so `get_group_member_list` raises `NotSupportedError`.
- Outbound images require a public URL: the Messaging API fetches `originalContentUrl`, so a base64-only `Image` component raises `NotSupportedError` instead of sending nothing.
- LINE has no message edit API; `edit_message` raises `NotSupportedError`. Streaming output is not supported.
- Requests are capped at five messages per call and 5000 characters per text message; longer chains are split into multiple requests.
- Offline coverage lives in `tests/unit_tests/platform/test_line_eba_adapter.py`. A real channel (webhook delivery, reply tokens, media download) still needs verification against a live LINE Official Account.