/**
 * Mimecast API 2.0 Client
 * Auth: OAuth2 Client Credentials — POST /oauth/token
 * Base: https://api.services.mimecast.com
 *
 * Endpoints sourced from official Postman collection (mimecast-api-v2-collection.json):
 *  - Message logs:   POST /api/message-finder/search  (trackedEmails with pagination)
 *  - SIEM batch:     GET  /siem/v1/batch/events/cg    (returns pre-signed URLs → download JSON)
 *  - Threat events:  GET  /threats/v1/events
 *  - Message info:   POST /api/message-finder/get-message-info
 *  - Account:        POST /api/account/get-account
 */

export interface MimecastConfig {
  clientId: string;
  clientSecret: string;
  baseUrl?: string;
}

interface TokenResponse {
  access_token: string;
  token_type: string;
  expires_in: number;
}

interface TokenCache {
  token: string;
  expiresAt: number;
}

export interface MimecastMessage {
  id: string;
  senderAddress: string;
  recipientAddress: string;
  subject: string;
  direction: string;
  status: string;
  action?: string;
  spamScore?: number;
  sizeBytes?: number;
  attachmentCount?: boolean | number;
  sentDateTime?: string;
  receivedDateTime?: string;
  route?: string;
  rejectReason?: string;
  heldReason?: string;
  sourceIp?: string;
  [key: string]: any;
}

export interface MimecastThreatEvent {
  id: string;
  messageId?: string;
  eventType: string;
  threatLevel?: string;
  url?: string;
  fileName?: string;
  verdict?: string;
  actorEmail?: string;
  eventDateTime?: string;
  analysis?: string[];
  source?: string[];
  direction?: string[];
  status?: string[];
  [key: string]: any;
}

export interface MimecastMessageInfo {
  messageId: string;
  bodyText?: string;
  bodyHtml?: string;
  headers?: Record<string, string>;
}

export interface PaginatedResult<T> {
  items: T[];
  nextCursor: string | null;
  totalCount?: number;
}

export class MimecastClient {
  private readonly clientId: string;
  private readonly clientSecret: string;
  private readonly baseUrl: string;
  private tokenCache: TokenCache | null = null;

  constructor(config: MimecastConfig) {
    this.clientId = config.clientId;
    this.clientSecret = config.clientSecret;
    this.baseUrl = (config.baseUrl ?? 'https://api.services.mimecast.com').replace(/\/$/, '');
  }

  // ── Auth ─────────────────────────────────────────────────────────────────

  private async getToken(): Promise<string> {
    if (this.tokenCache && Date.now() < this.tokenCache.expiresAt - 60_000) {
      return this.tokenCache.token;
    }

    const body = new URLSearchParams({
      grant_type: 'client_credentials',
      client_id: this.clientId,
      client_secret: this.clientSecret,
    });

    const res = await fetch(`${this.baseUrl}/oauth/token`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
      body: body.toString(),
    });

    if (!res.ok) {
      const text = await res.text();
      throw new Error(`Mimecast auth failed (${res.status}): ${text}`);
    }

    const data: TokenResponse = await res.json();
    this.tokenCache = {
      token: data.access_token,
      expiresAt: Date.now() + data.expires_in * 1000,
    };
    return data.access_token;
  }

  private async request<T>(
    method: 'GET' | 'POST',
    path: string,
    body?: Record<string, any>,
    params?: Record<string, string>
  ): Promise<T> {
    const token = await this.getToken();

    let url = `${this.baseUrl}${path}`;
    if (params && Object.keys(params).length > 0) {
      url = `${url}?${new URLSearchParams(params).toString()}`;
    }

    const res = await fetch(url, {
      method,
      headers: {
        Authorization: `Bearer ${token}`,
        'Content-Type': 'application/json',
        Accept: 'application/json',
      },
      body: body ? JSON.stringify(body) : undefined,
    });

    if (!res.ok) {
      const text = await res.text();
      throw new Error(`Mimecast ${method} ${path} failed (${res.status}): ${text}`);
    }

    return res.json() as T;
  }

  // ── Message Tracking ─────────────────────────────────────────────────────

  /**
   * Search tracked emails via POST /api/message-finder/search
   * Response: { data: [{ trackedEmails: [...], pageToken: string }] }
   */
  async getMessageLogs(options: {
    from: string;   // ISO datetime string
    to: string;
    cursor?: string;
    pageSize?: number;
  }): Promise<PaginatedResult<MimecastMessage>> {
    const reqData: Record<string, any> = {
      from: options.from,
      to: options.to,
      pageSize: options.pageSize ?? 500,
    };
    if (options.cursor) reqData.pageToken = options.cursor;

    const data = await this.request<any>('POST', '/api/message-finder/search', { data: [reqData] });

    const block = data.data?.[0] ?? {};
    const tracked: any[] = block.trackedEmails ?? [];

    return {
      items: tracked.map((m: any) => this.normalizeTrackedEmail(m)),
      nextCursor: block.pageToken ?? null,
      totalCount: tracked.length,
    };
  }

  private normalizeTrackedEmail(m: any): MimecastMessage {
    const sender = m.fromEnv?.emailAddress ?? m.fromHdr?.emailAddress ?? m.sender ?? '';
    const recipients: string[] = (m.to ?? []).map((t: any) =>
      typeof t === 'string' ? t : t.emailAddress ?? ''
    );

    return {
      id: m.id,
      senderAddress: sender,
      recipientAddress: recipients.join(', '),
      subject: m.subject ?? '',
      direction: m.route?.toLowerCase().includes('inbound') ? 'inbound' : 'outbound',
      status: m.status ?? '',
      action: m.detectionLevel ?? undefined,
      spamScore: m.spamScore ?? undefined,
      sizeBytes: undefined,
      attachmentCount: m.attachments ?? 0,
      sentDateTime: m.sent ?? undefined,
      receivedDateTime: m.received ?? undefined,
      route: m.route ?? undefined,
      rejectReason: m.info ?? undefined,
      sourceIp: m.senderIP ?? undefined,
      _raw: m,
    };
  }

  // ── SIEM Batch Events ─────────────────────────────────────────────────────

  /**
   * GET /siem/v1/batch/events/cg — returns pre-signed download URLs for batch NDJSON files
   * Each URL points to a compressed file; we download and parse each one.
   * Response: { value: [{url, expiry, size}], "@nextPage": string }
   */
  async getSiemBatchEventUrls(options: {
    from: string;  // date only: YYYY-MM-DD
    to: string;
    type?: string;
    cursor?: string;
    pageSize?: number;
  }): Promise<{ urls: Array<{ url: string; expiry: string; size: number }>; nextCursor: string | null }> {
    const params: Record<string, string> = {
      type: options.type ?? 'mailflow',
      dateRangeStartsAt: options.from,
      dateRangeEndsAt: options.to,
      pageSize: String(options.pageSize ?? 500),
    };
    if (options.cursor) params.pageToken = options.cursor;

    const data = await this.request<any>('GET', '/siem/v1/batch/events/cg', undefined, params);

    return {
      urls: data.value ?? [],
      nextCursor: data['@nextPage'] ?? null,
    };
  }

  /**
   * Download and parse a SIEM batch event file (NDJSON, possibly gzipped)
   */
  async downloadSiemBatchFile(url: string): Promise<MimecastMessage[]> {
    const res = await fetch(url);
    if (!res.ok) return [];

    const text = await res.text();
    const lines = text.split('\n').filter(l => l.trim());
    const messages: MimecastMessage[] = [];

    for (const line of lines) {
      try {
        const event = JSON.parse(line);
        messages.push(this.normalizeSiemEvent(event));
      } catch {
        // skip malformed lines
      }
    }

    return messages;
  }

  private normalizeSiemEvent(e: any): MimecastMessage {
    return {
      id: e.messageId ?? e.id ?? e.Messageid ?? '',
      senderAddress: e.senderAddress ?? e.Sender ?? e.sender ?? '',
      recipientAddress: e.recipientAddress ?? e.Recipient ?? e.recipient ?? '',
      subject: e.subject ?? e.Subject ?? '',
      direction: (e.Dir ?? e.direction ?? '').toLowerCase() === 'inbound' ? 'inbound' : 'outbound',
      status: e.Act ?? e.action ?? e.status ?? '',
      action: e.RejType ?? e.rejectionType ?? undefined,
      spamScore: e.SpamScore ?? e.spamScore ?? undefined,
      sizeBytes: e.MsgSize ?? e.messageSize ?? e.size ?? undefined,
      attachmentCount: e.AttCnt ?? e.attachmentCount ?? 0,
      sentDateTime: e.Datetime ?? e.datetime ?? e.timestamp ?? undefined,
      receivedDateTime: e.Datetime ?? undefined,
      route: e.Route ?? e.route ?? undefined,
      rejectReason: e.RejCode ?? e.rejectionCode ?? undefined,
      heldReason: e.HeldGroup ?? undefined,
      sourceIp: e.IP ?? e.senderIp ?? undefined,
      _raw: e,
    };
  }

  // ── Threat Events ─────────────────────────────────────────────────────────

  /**
   * GET /threats/v1/events
   * Response: { value: [{timestamp, analysis, source, details, status, direction, subject, sender, ...}], "@nextPage": string }
   */
  async getThreatEvents(options: {
    cursor?: string;
    pageSize?: number;
  } = {}): Promise<PaginatedResult<MimecastThreatEvent>> {
    const params: Record<string, string> = {
      pageSize: String(options.pageSize ?? 500),
    };
    if (options.cursor) params.pageToken = options.cursor;

    try {
      const data = await this.request<any>('GET', '/threats/v1/events', undefined, params);
      const items = (data.value ?? []).map((e: any) => this.normalizeThreatEvent(e));
      return {
        items,
        nextCursor: data['@nextPage'] ?? null,
      };
    } catch {
      return { items: [], nextCursor: null };
    }
  }

  private normalizeThreatEvent(e: any): MimecastThreatEvent {
    const analysis: string[] = Array.isArray(e.analysis) ? e.analysis : [e.analysis].filter(Boolean);
    const eventType = analysis[0] ?? 'unknown';

    const statusArr: string[] = Array.isArray(e.status) ? e.status : [e.status].filter(Boolean);
    const verdict = statusArr[0] ?? undefined;

    const threatLevel = analysis.includes('malware') ? 'high'
      : analysis.includes('phishing') ? 'high'
      : analysis.includes('spam') ? 'medium'
      : 'info';

    return {
      id: e.id ?? `threat_${e.sender ?? ''}_${e.timestamp ?? Date.now()}`,
      messageId: e.messageId ?? undefined,
      eventType,
      threatLevel,
      url: e.url ?? undefined,
      fileName: undefined,
      verdict,
      actorEmail: e.sender ?? undefined,
      eventDateTime: e.timestamp ?? undefined,
      analysis,
      source: Array.isArray(e.source) ? e.source : [e.source].filter(Boolean),
      direction: Array.isArray(e.direction) ? e.direction : [e.direction].filter(Boolean),
      status: statusArr,
      _raw: e,
    };
  }

  // ── Message Info (body/headers) ────────────────────────────────────────────

  /**
   * POST /api/message-finder/get-message-info
   * Returns delivered message details including parts
   */
  async getMessageInfo(messageId: string): Promise<MimecastMessageInfo | null> {
    try {
      const data = await this.request<any>('POST', '/api/message-finder/get-message-info', {
        data: [{ id: messageId }],
      });

      const delivered = data.data?.[0]?.deliveredMessage;
      if (!delivered) return null;

      const entries = Object.values(delivered) as any[];
      if (!entries.length) return null;

      const info = entries[0]?.messageInfo ?? entries[0];

      return {
        messageId,
        bodyText: info?.textBody ?? info?.body ?? undefined,
        bodyHtml: info?.htmlBody ?? undefined,
        headers: info?.headers ?? undefined,
      };
    } catch {
      return null;
    }
  }

  // ── Account ────────────────────────────────────────────────────────────────

  /**
   * POST /api/account/get-account
   */
  async testConnection(): Promise<{ ok: boolean; accountName?: string; packageName?: string; error?: string }> {
    try {
      const data = await this.request<any>('POST', '/api/account/get-account', { data: [{}] });
      const account = data.data?.[0] ?? {};
      return {
        ok: true,
        accountName: account.accountName ?? account.accountCode ?? 'Connected',
        packageName: account.packageName ?? undefined,
      };
    } catch (err: any) {
      return { ok: false, error: err.message };
    }
  }
}

let _client: MimecastClient | null = null;

export function getMimecastClient(): MimecastClient {
  if (!_client) {
    const clientId = process.env.MIMECAST_CLIENT_ID;
    const clientSecret = process.env.MIMECAST_CLIENT_SECRET;
    if (!clientId || !clientSecret) {
      throw new Error('MIMECAST_CLIENT_ID and MIMECAST_CLIENT_SECRET must be set');
    }
    _client = new MimecastClient({
      clientId,
      clientSecret,
      baseUrl: process.env.MIMECAST_BASE_URL ?? 'https://api.services.mimecast.com',
    });
  }
  return _client;
}