import { MODES, type ChatMessage, type Mode } from "../../types";
import {
  parseAdminChannelMessage,
  parseHistoryMessages,
  parsePersistedMessage,
  toRecord,
} from "../../wsParse";
import { frameSessionId, type FrameEvent, type FramePayload, type StoreState } from "./shared";

/** The fields of a `message_edited` payload the chat needs: the edited message's
 *  id and its new content. `sessionId` is carried inside the broadcast DTO (and on
 *  the frame envelope) so the store can confine the patch to that session's bucket;
 *  `mode`/`mood` are optional — an edit never changes them, but the DTO carries them
 *  for completeness. */
interface MessageEdited {
  id: string;
  content: string;
  sessionId?: string;
  mode?: Mode;
  mood?: string;
}

/** Narrow a `message_edited` payload (the updated message DTO), or null when it is
 *  unusable. `content` is required: an edit always carries the new text, and a
 *  frame without it must not blank out a rendered bubble. */
function parseMessageEdited(data: unknown): MessageEdited | null {
  const r = toRecord(data);
  if (!r || typeof r.id !== "string" || r.id === "" || typeof r.content !== "string") {
    return null;
  }
  return {
    id: r.id,
    content: r.content,
    sessionId: typeof r.sessionId === "string" ? r.sessionId : undefined,
    mode:
      typeof r.mode === "string" && MODES.includes(r.mode as Mode)
        ? (r.mode as Mode)
        : undefined,
    mood: typeof r.mood === "string" ? r.mood : undefined,
  };
}

/** 消息落库/编辑/删除帧处理组：message_persisted / message_edited /
 *  message_deleted / channel_persisted。命中（含组内主动丢弃）返回 true，
 *  未命中返回 false 交给下一组。 */
export function handleMessageEvent(ev: FrameEvent, r: FramePayload, s: StoreState): boolean {
  switch (ev.type) {
    case "history": {
      // 握手回放（契约 §3.2，仅 owner/admin，只回放主会话最近 50 条）：此前这帧落到
      // 未知帧兜底被丢掉 ⇒ WS 断线窗口内落库的消息永久缺失（要等切会话/刷新才补）。
      // 并入时按 id 去重、只按精确键（clientMsgId / turnId）认领本端气泡（见
      // sessionCache.mergeHistory）—— 整批回放绝不用内容/时间启发式，以免把正在
      // 流式的气泡错配到某条旧行上。帧壳 sessionId（"web"）就是回放所属会话。
      const msgs = parseHistoryMessages(r?.messages);
      if (msgs.length) {
        s.mergeHistoryPage(frameSessionId(ev, r) ?? msgs[0].sessionId ?? "", msgs);
      }
      return true;
    }
    case "message_persisted": {
      // design/16 §4.2 — a user or assistant message was persisted and broadcast
      // with its backend id. 裁决 16.4.5: the frame is written into the bucket its
      // own `sessionId` names (the store routes it), so a background conversation
      // keeps accumulating instead of being dropped. Within that bucket the store
      // dedups by id and adopts the local optimistic bubble (uid → backend id), so
      // both the originating and remote browsers converge on one message.
      const msg = parsePersistedMessage(r?.message);
      if (msg) {
        s.appendOrUpdateMessage(msg);
        // `turn_begin` 可能早于用户行落库到达（那时 messageIds 在列表里还没有落点，
        // 绑定只记在 turnBindings 里）：这里补一次落地，让气泡及时进灰态。
        s.rebindSessionTurns(msg.sessionId ?? s.activeSessionId);
        // 灰态的**兜底**收口（规范草案 §1.2）：该 `turnId` 的助手回复落库同样收口，
        // 它与 `turn.end` 顺序不定，任一到即收。
        if (msg.role === "assistant" && msg.turnId) {
          s.clearGrey(msg.turnId, msg.sessionId ?? s.activeSessionId);
        }
      }
      return true;
    }
    case "message_edited": {
      // design/16 §4.2 (D3 edit path) — the stored message's content was changed
      // and broadcast with the updated DTO. The backend row stays the single source
      // of truth; this only re-renders the bubble of the session the frame names
      // (the store confines the patch to that session's bucket). Patch by id — an
      // id we do not hold is another session's (or an already-gone) message, never
      // a new row.
      const edit = parseMessageEdited(ev.data);
      if (!edit) return true;
      const patch: Partial<ChatMessage> = { content: edit.content };
      if (edit.mode) patch.mode = edit.mode;
      if (edit.mood) patch.mood = edit.mood;
      s.updateMessageById(edit.id, patch, edit.sessionId ?? ev.sessionId);
      return true;
    }
    case "message_deleted": {
      // design/16 §4.2 (D3 delete path) — the message was removed server-side, so
      // drop it by id instead of waiting for a manual re-read. The frame's session
      // scopes the removal; without one the store searches by id (globally unique).
      const id = r && typeof r.id === "string" ? r.id : "";
      if (id) s.removeMessageById(id, ev.sessionId);
      return true;
    }
    case "channel_persisted": {
      // design/16 §4.6 §4 — an isolated (group/stranger) channel message was
      // persisted and broadcast for the IM adapter log page. The web chat has no
      // handler for this type, so it never reaches the active conversation; the
      // admin adapter log consumes it via `channelEvents` to append in realtime.
      const msg = parseAdminChannelMessage(r?.message);
      if (msg) s.pushChannelEvent(msg);
      return true;
    }
    default:
      return false;
  }
}