import { fetchGraphJson, type GraphResponse } from "./graph.js";

export type GraphThreadMessage = {
  id?: string;
  from?: {
    user?: { displayName?: string; id?: string };
    application?: { displayName?: string; id?: string };
  };
  body?: { content?: string; contentType?: string };
  createdDateTime?: string;
};

// TTL cache for team ID -> group GUID mapping.
const teamGroupIdCache = new Map<string, { groupId: string; expiresAt: number }>();
const CACHE_TTL_MS = 10 * 60 * 1000; // 10 minutes

/**
 * Strip HTML tags from Teams message content, preserving @mention display names.
 * Teams wraps mentions in <at>Name</at> tags.
 */
export function stripHtmlFromTeamsMessage(html: string): string {
  // Preserve mention display names by replacing <at>Name</at> with @Name.
  let text = html.replace(/<at[^>]*>(.*?)<\/at>/gi, "@$1");
  // Strip remaining HTML tags.
  text = text.replace(/<[^>]*>/g, " ");
  // Decode common HTML entities.
  text = text
    .replace(/&amp;/g, "&")
    .replace(/&lt;/g, "<")
    .replace(/&gt;/g, ">")
    .replace(/&quot;/g, '"')
    .replace(/&#39;/g, "'")
    .replace(/&nbsp;/g, " ");
  // Normalize whitespace.
  return text.replace(/\s+/g, " ").trim();
}

/**
 * Resolve the Azure AD group GUID for a Teams conversation team ID.
 * Results are cached with a TTL to avoid repeated Graph API calls.
 */
export async function resolveTeamGroupId(
  token: string,
  conversationTeamId: string,
): Promise<string> {
  const cached = teamGroupIdCache.get(conversationTeamId);
  if (cached && cached.expiresAt > Date.now()) {
    return cached.groupId;
  }

  // The team ID in channelData is typically the group ID itself for standard teams.
  // Validate by fetching /teams/{id} and returning the confirmed id.
  // Requires Team.ReadBasic.All permission; fall back to raw ID if missing.
  try {
    const path = `/teams/${encodeURIComponent(conversationTeamId)}?$select=id`;
    const team = await fetchGraphJson<{ id?: string }>({ token, path });
    const groupId = team.id ?? conversationTeamId;

    // Only cache when the Graph lookup succeeds — caching a fallback raw ID
    // can cause silent failures for the entire TTL if the ID is not a valid
    // Graph team GUID (e.g. Bot Framework conversation key).
    teamGroupIdCache.set(conversationTeamId, {
      groupId,
      expiresAt: Date.now() + CACHE_TTL_MS,
    });

    return groupId;
  } catch {
    // Fallback to raw team ID without caching so subsequent calls retry the
    // Graph lookup instead of using a potentially invalid cached value.
    return conversationTeamId;
  }
}

/**
 * Fetch a single channel message (the parent/root of a thread).
 * Returns undefined on error so callers can degrade gracefully.
 */
export async function fetchChannelMessage(
  token: string,
  groupId: string,
  channelId: string,
  messageId: string,
): Promise<GraphThreadMessage | undefined> {
  const path = `/teams/${encodeURIComponent(groupId)}/channels/${encodeURIComponent(channelId)}/messages/${encodeURIComponent(messageId)}?$select=id,from,body,createdDateTime`;
  try {
    return await fetchGraphJson<GraphThreadMessage>({ token, path });
  } catch {
    return undefined;
  }
}

/**
 * Fetch thread replies for a channel message, ordered chronologically.
 *
 * **Limitation:** The Graph API replies endpoint (`/messages/{id}/replies`) does not
 * support `$orderby`, so results are always returned in ascending (oldest-first) order.
 * Combined with the `$top` cap of 50, this means only the **oldest 50 replies** are
 * returned for long threads — newer replies are silently omitted. There is currently no
 * Graph API workaround for this; pagination via `@odata.nextLink` can retrieve more
 * replies but still in ascending order only.
 */
export async function fetchThreadReplies(
  token: string,
  groupId: string,
  channelId: string,
  messageId: string,
  limit = 50,
): Promise<GraphThreadMessage[]> {
  const top = Math.min(Math.max(limit, 1), 50);
  // NOTE: Graph replies endpoint returns oldest-first and does not support $orderby.
  // For threads with >50 replies, only the oldest 50 are returned. The most recent
  // replies (often the most relevant context) may be truncated.
  const path = `/teams/${encodeURIComponent(groupId)}/channels/${encodeURIComponent(channelId)}/messages/${encodeURIComponent(messageId)}/replies?$top=${top}&$select=id,from,body,createdDateTime`;
  const res = await fetchGraphJson<GraphResponse<GraphThreadMessage>>({ token, path });
  return res.value ?? [];
}

/**
 * Format thread messages into a context string for the agent.
 * Skips the current message (by id) and blank messages.
 */
export function formatThreadContext(
  messages: GraphThreadMessage[],
  currentMessageId?: string,
): string {
  const lines: string[] = [];
  for (const msg of messages) {
    if (msg.id && msg.id === currentMessageId) continue; // Skip the triggering message.
    const sender = msg.from?.user?.displayName ?? msg.from?.application?.displayName ?? "unknown";
    const contentType = msg.body?.contentType ?? "text";
    const rawContent = msg.body?.content ?? "";
    const content =
      contentType === "html" ? stripHtmlFromTeamsMessage(rawContent) : rawContent.trim();
    if (!content) continue;
    lines.push(`${sender}: ${content}`);
  }
  return lines.join("\n");
}

// Exported for testing only.
export { teamGroupIdCache as _teamGroupIdCacheForTest };