import type { RedditAccountRuntime, RedditAccountRuntimeManager } from './reddit-account-runtime.js';
import type { ActiveChat } from './chat/types.js';
import { buildConversationState, mergeConversationState } from './conversation-state.js';

export type RedditUserMessageResult = {
  accountId: string;
  redditUsername: string;
  recipient: string;
  conversationId: string;
  reusedConversation: boolean;
};

type RuntimeConversation = { runtime: RedditAccountRuntime; conversation: ActiveChat };

/** Selects an account and performs one explicit, rate-limited operator/API send. */
export class RedditUserMessenger {
  constructor(private readonly runtimes: RedditAccountRuntimeManager) {}

  async send(username: string, message: string): Promise<RedditUserMessageResult> {
    const recipient = username.trim().replace(/^u\//i, '');
    const running = this.runningRuntimes();
    if (running.length === 0) throw new RedditUserMessageError(503, 'No Reddit account is running');

    const existing = await this.findExistingConversation(running, recipient);
    if (existing) return this.sendExisting(existing, recipient, message);

    const runtime = running
      .filter((item) => item.resources.accountAuth.isFullyAuthenticated())
      .filter((item) => !item.resources.chatService.getInvitationCooldown())
      .sort(compareAvailableRuntimes)[0];
    if (!runtime) throw new RedditUserMessageError(503, 'No authenticated Reddit account is available to start a conversation');

    const started = await runtime.resources.rateLimiter.throttle(
      () => runtime.resources.chatService.startConversationDetailed(recipient, message),
      (result) => result.status === 'sent',
    );
    if (started.status !== 'sent') {
      throw new RedditUserMessageError(started.status === 'terminal' ? 422 : 503, started.reason);
    }
    const conversationId = started.chat.roomId;
    if (!conversationId) throw new RedditUserMessageError(502, 'Reddit confirmed the message without returning a conversation ID');
    this.recordSend(runtime, recipient, `Started chat with u/${recipient}`);
    runtime.resources.conversationStateRepo.save(
      conversationId,
      buildConversationState(started.chat.messages ?? [{ sender: 'Me', text: message, isSelf: true }]),
    );
    return resultFor(runtime, recipient, conversationId, false);
  }

  private runningRuntimes(): RedditAccountRuntime[] {
    return this.runtimes.list()
      .filter((snapshot) => snapshot.state === 'running')
      .flatMap((snapshot) => {
        const runtime = this.runtimes.get(snapshot.accountId);
        return runtime ? [runtime] : [];
      });
  }

  private async findExistingConversation(
    runtimes: RedditAccountRuntime[],
    username: string,
  ): Promise<RuntimeConversation | null> {
    const normalized = normalizeUsername(username);
    const matches = (await Promise.all(runtimes.map(async (runtime) =>
      (await runtime.resources.chatService.getCachedConversations())
        .filter((conversation) => normalizeUsername(conversation.username) === normalized)
        .map((conversation) => ({ runtime, conversation })),
    ))).flat();
    matches.sort((left, right) => right.conversation.lastMessageTime - left.conversation.lastMessageTime
      || left.runtime.session.redditUsername.localeCompare(right.runtime.session.redditUsername));
    return matches[0] ?? null;
  }

  private async sendExisting(
    selected: RuntimeConversation,
    username: string,
    message: string,
  ): Promise<RedditUserMessageResult> {
    const { runtime, conversation } = selected;
    if (!conversation.url || !conversation.roomId) {
      throw new RedditUserMessageError(409, 'The existing conversation is missing its Matrix room details; synchronize chats and retry');
    }
    const sent = await runtime.resources.rateLimiter.throttle(
      () => runtime.resources.chatService.sendChatMessage(conversation.url!, message),
      (success) => success,
    );
    if (!sent) throw new RedditUserMessageError(502, 'Reddit did not confirm the message send');
    const currentMessages = (conversation.messages ?? []).map(({ sender, text, isSelf }) => ({ sender, text, isSelf }));
    const state = mergeConversationState(
      runtime.resources.conversationStateRepo.get(conversation.roomId),
      buildConversationState([...currentMessages, { sender: 'Me', text: message, isSelf: true }]),
    );
    state.automation.status = 'user-overridden';
    state.automation.handoffReason = 'An API message was sent in this conversation.';
    runtime.resources.conversationStateRepo.save(conversation.roomId, state);
    this.recordSend(runtime, username, `Sent chat message to u/${username}`);
    void runtime.resources.chatService.refreshTopChats(5).catch(() => undefined);
    return resultFor(runtime, username, conversation.roomId, true);
  }

  private recordSend(runtime: RedditAccountRuntime, username: string, description: string): void {
    runtime.resources.activityLogRepo.insert({
      timestamp: Date.now(),
      type: 'sent',
      message: description,
      recipient: username,
    });
  }
}

export class RedditUserMessageError extends Error {
  constructor(readonly status: number, message: string) {
    super(message);
  }
}

function compareAvailableRuntimes(left: RedditAccountRuntime, right: RedditAccountRuntime): number {
  return left.resources.rateLimiter.getStats().messagesThisHour
    - right.resources.rateLimiter.getStats().messagesThisHour
    || left.session.redditUsername.localeCompare(right.session.redditUsername);
}

function normalizeUsername(username: string): string {
  return username.trim().replace(/^u\//i, '').toLocaleLowerCase('en-US');
}

function resultFor(
  runtime: RedditAccountRuntime,
  recipient: string,
  conversationId: string,
  reusedConversation: boolean,
): RedditUserMessageResult {
  return {
    accountId: runtime.session.accountId,
    redditUsername: runtime.session.redditUsername,
    recipient: recipient.trim().replace(/^u\//i, ''),
    conversationId,
    reusedConversation,
  };
}