import type { IdentityRegistry } from './identity.js';
import type { SubDiscussionStore } from './sub-discussion-store.js';

// Plugin-local before_prompt_build hook that injects per-(agent, channel)
// guides for sub-discussion channels created via the `create-sub-discussion`
// tool. Mirrors the pattern used by ClawPrompts' fabric-chat-injector
// (channelId-aware injection) but with content dynamically supplied at
// channel-creation time instead of read from static files via PrismFacet's
// router/rule registry.
//
// Match logic per turn:
//   ctx.channelId  → store.find()  → sub-discussion entry
//   ctx.agentId    → identity.findByAgentId().fabricUserId
//                    ─ matches entry.hostUserId   → inject hostGuide
//                    ─ matches entry.guestUserIds → inject guestGuide
//                    ─ neither                    → no injection
//
// Fail-closed on unknown agentId/channelId — we never inject "the wrong"
// guide, only the right one or nothing.

const _G = globalThis as Record<string, unknown>;
const DEDUP_KEY = '_fabricSubDiscussionHookDedup';

type PromptCtx = {
  agentId?: string;
  channelId?: string;
  messageProvider?: string;
};

export function registerSubDiscussionHook(
  api: {
    on: (hook: string, handler: (...args: unknown[]) => unknown) => void;
    logger: { info: (m: string) => void; warn: (m: string) => void };
  },
  store: SubDiscussionStore,
  identity: IdentityRegistry,
): void {
  if (!(_G[DEDUP_KEY] instanceof WeakSet)) _G[DEDUP_KEY] = new WeakSet<object>();
  const dedup = _G[DEDUP_KEY] as WeakSet<object>;

  api.on('before_prompt_build', async (...args: unknown[]) => {
    const event = args[0];
    const ctx = (args[1] ?? {}) as PromptCtx;
    // The hook fires both for fabric-driven turns (channelId set) and
    // for other triggers (HF wake, exec-event, etc.) — drop those.
    if (typeof event === 'object' && event !== null) {
      if (dedup.has(event)) return undefined;
      dedup.add(event);
    }
    const agentId = (ctx.agentId ?? '').trim();
    const channelId = (ctx.channelId ?? '').trim();
    if (!agentId || !channelId) return undefined;
    const provider = (ctx.messageProvider ?? '').toLowerCase();
    if (provider && provider !== 'fabric') return undefined;

    const entry = store.find(channelId);
    if (!entry) return undefined;

    const ident = identity.findByAgentId(agentId);
    const myUserId = (ident?.fabricUserId ?? '').trim();
    if (!myUserId) {
      // identity registry caches fabricUserId after the first agentLogin
      // in inbound.ts. If it's missing here, the agent likely hasn't
      // completed login yet — skip rather than guess.
      return undefined;
    }

    if (myUserId === entry.hostUserId) {
      return { appendSystemContext: entry.hostGuide };
    }
    if (entry.guestUserIds.includes(myUserId)) {
      return { appendSystemContext: entry.guestGuide };
    }
    return undefined;
  });
}