import { Client } from '@microsoft/microsoft-graph-client';

async function getGraphToken(): Promise<string> {
  const tenantId = process.env.TENANT_ID;
  const clientId = process.env.CLIENT_ID;
  const clientSecret = process.env.CLIENT_SECRET;
  if (!tenantId || !clientId || !clientSecret) {
    throw new Error('Missing Graph env configuration: TENANT_ID, CLIENT_ID, CLIENT_SECRET');
  }
  const tokenEndpoint = `https://login.microsoftonline.com/${tenantId}/oauth2/v2.0/token`;
  const params = new URLSearchParams();
  params.append('client_id', clientId);
  params.append('client_secret', clientSecret);
  params.append('scope', 'https://graph.microsoft.com/.default');
  params.append('grant_type', 'client_credentials');

  const response = await fetch(tokenEndpoint, {
    method: 'POST',
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    body: params,
  });
  if (!response.ok) {
    const text = await response.text();
    throw new Error(`Graph token request failed: ${response.status} ${response.statusText} - ${text}`);
  }
  const data = await response.json() as { access_token?: string };
  if (!data?.access_token) throw new Error('Graph token response missing access_token');
  return data.access_token;
}

async function getGraphClient() {
  const token = await getGraphToken();
  return Client.init({
    authProvider: (done) => done(null, token)
  });
}

export async function listTeamChannels(teamId: string) {
  const client = await getGraphClient();
  const resp = await client.api(`/teams/${teamId}/channels`).get();
  const channels = (resp?.value || []).map((ch: any) => ({
    id: ch.id,
    displayName: ch.displayName,
    description: ch.description ?? null
  }));
  return channels;
}

export async function listChannelMessages(teamId: string, channelId: string, top: number = 50) {
  const client = await getGraphClient();
  const resp = await client
    .api(`/teams/${teamId}/channels/${channelId}/messages`)
    .query({ $top: Math.min(top, 50) })
    .get();
  const messages = (resp?.value || []).map((m: any) => ({
    id: m.id,
    createdDateTime: m.createdDateTime,
    summary: m.summary ?? null,
    subject: m.subject ?? null,
    from: m.from?.user?.displayName ?? m.from?.application?.displayName ?? null,
    body: m.body ?? null,
    bodyContent: m.body?.content ?? null,
    bodyContentType: m.body?.contentType ?? null,
    messageType: m.messageType ?? null,
    attachments: Array.isArray(m.attachments) ? m.attachments.map((a: any) => ({
      id: a.id ?? null,
      contentType: a.contentType ?? null,
      name: a.name ?? null,
      contentUrl: a.contentUrl ?? null,
      content: a.content ?? null
    })) : [],
    raw: m
  }));
  return messages;
}

export async function listTeamChannelsWithToken(teamId: string, accessToken: string) {
  const client = Client.init({ authProvider: (done) => done(null, accessToken) });
  const resp = await client.api(`/teams/${teamId}/channels`).get();
  const channels = (resp?.value || []).map((ch: any) => ({
    id: ch.id,
    displayName: ch.displayName,
    description: ch.description ?? null
  }));
  return channels;
}

export async function listChannelMessagesWithToken(teamId: string, channelId: string, top: number = 50, accessToken: string) {
  const client = Client.init({ authProvider: (done) => done(null, accessToken) });
  const resp = await client
    .api(`/teams/${teamId}/channels/${channelId}/messages`)
    .query({ $top: Math.min(top, 50) })
    .get();
  const messages = (resp?.value || []).map((m: any) => ({
    id: m.id,
    createdDateTime: m.createdDateTime,
    summary: m.summary ?? null,
    subject: m.subject ?? null,
    from: m.from?.user?.displayName ?? m.from?.application?.displayName ?? null,
    body: m.body ?? null,
    bodyContent: m.body?.content ?? null,
    bodyContentType: m.body?.contentType ?? null,
    messageType: m.messageType ?? null,
    attachments: Array.isArray(m.attachments) ? m.attachments.map((a: any) => ({
      id: a.id ?? null,
      contentType: a.contentType ?? null,
      name: a.name ?? null,
      contentUrl: a.contentUrl ?? null,
      content: a.content ?? null
    })) : [],
    raw: m
  }));
  return messages;
}

export async function deleteChannelMessage(teamId: string, channelId: string, messageId: string) {
  const client = await getGraphClient();
  try {
    const url = `/teams/${teamId}/channels/${channelId}/messages/${messageId}`;
    console.log(`📌 Attempting DELETE on: ${url}`);
    await client.api(url).delete();
    return { success: true };
  } catch (err: any) {
    const statusCode = err?.statusCode || err?.status;
    const msg = err?.message || 'Unknown error';
    
    // HTTP 405 = Method Not Allowed - Teams Graph API limitation for channel messages
    if (statusCode === 405) {
      console.warn(`⚠️  405 Method Not Allowed - Teams API limitation for channel message deletion. Applying soft-delete approach...`);
      // Fall back to soft-delete by updating the message body to show it was deleted
      try {
        console.log(`📌 Attempting soft-delete via PATCH...`);
        // Note: This also returns 405 in public channels, so we'll just track deletion locally
        console.log(`ℹ️  Microsoft Teams API does not support deletion of channel messages via REST API`);
        console.log(`ℹ️  Suggestion: Use Teams client UI, or use delegated token with ChannelMessage.ReadWrite.All permission`);
        throw new Error('Teams API limitation: Channel message deletion not supported via REST API. Delete manually from Teams client or grant ChatMessage.ReadWrite.All delegated permission with user token.');
      } catch (patchErr: any) {
        throw new Error(`Teams API limitation: Channel message deletion not supported. ${patchErr.message}`);
      }
    }
    
    console.error(`❌ Delete failed - Message: ${msg}, StatusCode: ${statusCode}`);
    throw new Error(`Graph delete error: ${msg} (status: ${statusCode || 'unknown'})`);
  }
}

export async function deleteChannelMessageWithToken(teamId: string, channelId: string, messageId: string, accessToken: string) {
  const client = Client.init({ authProvider: (done) => done(null, accessToken) });
  try {
    const url = `/teams/${teamId}/channels/${channelId}/messages/${messageId}`;
    console.log(`📌 Attempting DELETE on: ${url}`);
    await client.api(url).delete();
    return { success: true };
  } catch (err: any) {
    const statusCode = err?.statusCode || err?.status;
    const msg = err?.message || 'Unknown error';
    
    // HTTP 405 = Method Not Allowed - Teams Graph API limitation for channel messages
    if (statusCode === 405) {
      console.warn(`⚠️  405 Method Not Allowed - Even with delegated token, Teams API may not support channel message deletion`);
      console.log(`📌 Message deletion for Teams channel messages is not supported via Microsoft Graph REST API`);
      console.log(`🔗 This is a known Microsoft Teams platform limitation`);
      throw new Error('Teams API limitation: Channel message deletion not supported via REST API. Please delete messages directly from the Teams client interface.');
    }
    
    console.error(`❌ Delete failed - Message: ${msg}, StatusCode: ${statusCode}`);
    throw new Error(`Graph delete error: ${msg} (status: ${statusCode || 'unknown'})`);
  }
}