import { Injectable, Logger } from '@nestjs/common';
import type { AuthProviderCallback } from '@microsoft/microsoft-graph-client';
import {
  CalendarEvent,
  CalendarProvider,
  CalendarSourceUnreachableError,
  isNetworkUnreachableError,
} from '../calendar.service';

/** Optionen, die ntlmPost() unten uebergibt — nichts darueber hinaus. */
interface NtlmOptions {
  url: string;
  username: string;
  password: string;
  domain: string;
  workstation: string;
  body: string;
  headers: Record<string, string>;
  /** Millisekunden bis zum Abbruch mit `code: 'TIMEOUT'` (siehe ntlmPost). */
  timeout: number;
}

/**
 * Antwortform von httpntlm.post, beschrieben aus dem, was gelesen wird.
 *
 * `body` ist `Buffer | string`: httpreq (unter httpntlm) liefert eine
 * Zeichenkette, solange `binary` nicht gesetzt ist (gemessen,
 * httpreq@1.1.1/lib/httpreq.js:391) — hier wird es nicht gesetzt. Siehe die
 * ausfuehrliche Begruendung in inbox/exchange-inbox.provider.ts.
 */
interface NtlmResponse {
  statusCode: number;
  body?: Buffer | string;
}

// eslint-disable-next-line @typescript-eslint/no-require-imports
const httpntlm = require('httpntlm') as {
  post: (opts: NtlmOptions, cb: (err: Error | null, res: NtlmResponse) => void) => void;
};

/**
 * quick-261005: Ohne Grenze wartete ein EWS-Aufruf auf eine nicht
 * erreichbare Adresse rund zwei Minuten (TCP-Verbindungsaufbau des
 * Betriebssystems), der Test-Knopf hing so lange auf „wird geprueft“.
 */
const EWS_TIMEOUT_MS = 15_000;

const NS_SOAP = 'http://schemas.xmlsoap.org/soap/envelope/';
const NS_TYPES = 'http://schemas.microsoft.com/exchange/services/2006/types';
const NS_MESSAGES = 'http://schemas.microsoft.com/exchange/services/2006/messages';

function soapEnvelope(body: string): string {
  return `<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="${NS_SOAP}" xmlns:t="${NS_TYPES}" xmlns:m="${NS_MESSAGES}">
  <soap:Body>${body}</soap:Body>
</soap:Envelope>`;
}

function escapeXml(s: string): string {
  return s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;');
}

function extractAll(xml: string, tag: string): string[] {
  const results: string[] = [];
  const open = `<${tag}`;
  const close = `</${tag}>`;
  let pos = 0;
  while (pos < xml.length) {
    const start = xml.indexOf(open, pos);
    if (start === -1) break;
    const end = xml.indexOf(close, start);
    if (end === -1) break;
    const innerStart = xml.indexOf('>', start) + 1;
    results.push(xml.slice(innerStart, end));
    pos = end + close.length;
  }
  return results;
}

function extractAttr(xml: string, tag: string, attr: string): string {
  const tagStart = xml.indexOf(`<${tag}`);
  if (tagStart === -1) return '';
  const tagEnd = xml.indexOf('>', tagStart);
  const tagStr = xml.slice(tagStart, tagEnd + 1);
  const attrMatch = tagStr.match(new RegExp(`${attr}="([^"]*)"`));
  return attrMatch ? attrMatch[1] : '';
}

function ntlmPost(opts: NtlmOptions): Promise<{ statusCode: number; body: string }> {
  return new Promise((resolve, reject) => {
    // Eigene Zeitgrenze zusaetzlich zu `opts.timeout`: httpreq setzt seine
    // nur als Leerlaufgrenze am Socket, die waehrend des Verbindungsaufbaus
    // ueber den Keep-alive-Agenten von httpntlm NICHT greift — gemessen
    // 05.10.: 134 s bis zum Fehler trotz `timeout: 15000`.
    const timer = setTimeout(() => {
      reject(Object.assign(new Error('EWS request timed out'), { code: 'TIMEOUT' }));
    }, opts.timeout);
    httpntlm.post(opts, (err, res) => {
      clearTimeout(timer);
      if (err) return reject(err);
      resolve({
        statusCode: res.statusCode,
        body: typeof res.body === 'string' ? res.body : (res.body?.toString('utf-8') ?? ''),
      });
    });
  });
}

/**
 * Exchange calendar provider — dispatches on exchangeMode ('graph' vs 'ews').
 *
 * - 'graph': Uses @microsoft/microsoft-graph-client for Exchange Online / M365
 * - 'ews': Uses ews-javascript-api for on-premise Exchange Server
 *
 * Both modes gracefully degrade: on auth failure, returns empty array and
 * surfaces a generic error (no credential details — Security V7 / T-05-13).
 */
@Injectable()
export class ExchangeProvider implements CalendarProvider {
  private readonly logger = new Logger(ExchangeProvider.name);

  /**
   * Fetches events from Exchange, dispatching by exchangeMode.
   * D-08: source TYPE is configurable and attempted — widget must not crash.
   */
  async fetchEvents(
    source: {
      url: string;
      username?: string;
      password?: string;
      exchangeMode?: string | null;
      domain?: string;
      id: string;
      color?: string | null;
    },
    from: Date,
    to: Date,
  ): Promise<CalendarEvent[]> {
    const mode = source.exchangeMode || 'graph';

    try {
      if (mode === 'graph') {
        return await this.fetchViaGraph(source, from, to);
      } else {
        return await this.fetchViaEws(source, from, to);
      }
    } catch (error) {
      // Graceful degradation — T-05-13: no credential details in error
      this.logger.error(
        `Exchange (${mode}) fetch failed for source ${source.id}: ${(error as Error).message}`,
      );
      return [];
    }
  }

  /**
   * Tests connection to Exchange. Returns false on any auth/network failure.
   */
  async testConnection(
    source: {
      url: string;
      username?: string;
      password?: string;
      exchangeMode?: string | null;
      domain?: string;
      id: string;
    },
  ): Promise<boolean> {
    const mode = source.exchangeMode || 'graph';

    try {
      if (mode === 'graph') {
        return await this.testGraphConnection(source);
      } else {
        return await this.testEwsConnection(source);
      }
    } catch (error) {
      // quick-261005: „nicht erreichbar“ getrennt melden, damit die
      // Oberflaeche nicht „Zugangsdaten pruefen“ sagt, wenn das Netz fehlt.
      if (isNetworkUnreachableError(error)) throw new CalendarSourceUnreachableError();
      return false;
    }
  }

  /**
   * Fetches events via Microsoft Graph API (Exchange Online / M365).
   * Uses @microsoft/microsoft-graph-client with /me/calendarView.
   */
  private async fetchViaGraph(
    source: {
      url: string;
      username?: string;
      password?: string;
      id: string;
      color?: string | null;
    },
    from: Date,
    to: Date,
  ): Promise<CalendarEvent[]> {
    // Dynamic import to avoid loading Graph SDK when not needed
    const { Client: GraphClient } = await import(
      '@microsoft/microsoft-graph-client'
    );

    const client = GraphClient.init({
      authProvider: (done: AuthProviderCallback) => {
        // Use the password as the access token (OAuth bearer token)
        // Users configure their OAuth token in the password field for Graph API
        done(null, source.password || '');
      },
    });

    const result = await client
      .api('/me/calendarView')
      .query({
        startDateTime: from.toISOString(),
        endDateTime: to.toISOString(),
      })
      .select('id,subject,start,end,isAllDay,location,bodyPreview')
      .orderby('start/dateTime')
      .top(100)
      .get();

    const events: CalendarEvent[] = [];

    if (result?.value) {
      for (const item of result.value) {
        events.push({
          id: `${source.id}-${item.id}`,
          sourceId: source.id,
          title: item.subject || 'Untitled',
          start: new Date(`${item.start?.dateTime}Z`),
          end: new Date(`${item.end?.dateTime}Z`),
          allDay: item.isAllDay || false,
          location: item.location?.displayName || undefined,
          description: item.bodyPreview || undefined,
          color: source.color ?? undefined,
        });
      }
    }

    return events;
  }

  /**
   * Fetches calendar events via EWS using NTLM authentication (on-premise Exchange).
   * Uses raw SOAP + httpntlm — replaces ews-javascript-api which only supports Basic Auth.
   */
  private async fetchViaEws(
    source: {
      url: string;
      username?: string;
      password?: string;
      domain?: string;
      id: string;
      color?: string | null;
    },
    from: Date,
    to: Date,
  ): Promise<CalendarEvent[]> {
    const fromIso = from.toISOString();
    const toIso = to.toISOString();

    const findSoap = soapEnvelope(`
      <m:FindItem Traversal="Shallow">
        <m:ItemShape>
          <t:BaseShape>IdOnly</t:BaseShape>
          <t:AdditionalProperties>
            <t:FieldURI FieldURI="item:Subject"/>
            <t:FieldURI FieldURI="calendar:Start"/>
            <t:FieldURI FieldURI="calendar:End"/>
            <t:FieldURI FieldURI="calendar:IsAllDayEvent"/>
            <t:FieldURI FieldURI="calendar:Location"/>
          </t:AdditionalProperties>
        </m:ItemShape>
        <m:CalendarView StartDate="${escapeXml(fromIso)}" EndDate="${escapeXml(toIso)}" MaxEntriesReturned="100"/>
        <m:ParentFolderIds>
          <t:DistinguishedFolderId Id="calendar"/>
        </m:ParentFolderIds>
      </m:FindItem>`);

    const res = await this.ewsNtlmPost(source, findSoap, 'FindItem');

    if (res.statusCode !== 200) {
      this.logger.warn(`EWS FindItem calendar returned HTTP ${res.statusCode}`);
      return [];
    }

    const events: CalendarEvent[] = [];
    const itemBlocks = this.splitItemBlocks(res.body, 't:CalendarItem');

    for (const block of itemBlocks) {
      const uid = extractAttr(block, 't:ItemId', 'Id');
      const title = extractAll(block, 't:Subject')[0] ?? 'Untitled';
      const startStr = extractAll(block, 't:Start')[0] ?? '';
      const endStr = extractAll(block, 't:End')[0] ?? '';
      const allDayStr = extractAll(block, 't:IsAllDayEvent')[0] ?? 'false';
      const location = extractAll(block, 't:Location')[0] ?? undefined;

      events.push({
        id: `${source.id}-${uid || String(Date.now())}`,
        sourceId: source.id,
        title,
        start: startStr ? new Date(startStr) : new Date(),
        end: endStr ? new Date(endStr) : new Date(),
        allDay: allDayStr === 'true',
        location: location || undefined,
        description: undefined,
        color: source.color ?? undefined,
      });
    }

    return events;
  }

  private splitItemBlocks(xml: string, tag: string): string[] {
    const blocks: string[] = [];
    const open = `<${tag}`;
    const close = `</${tag}>`;
    let pos = 0;
    while (pos < xml.length) {
      const start = xml.indexOf(open, pos);
      if (start === -1) break;
      const end = xml.indexOf(close, start);
      if (end === -1) break;
      blocks.push(xml.slice(start, end + close.length));
      pos = end + close.length;
    }
    return blocks;
  }

  private async ewsNtlmPost(
    source: { url: string; username?: string; password?: string; domain?: string },
    soap: string,
    action: string,
  ): Promise<{ statusCode: number; body: string }> {
    return ntlmPost({
      url: source.url,
      username: source.username ?? '',
      password: source.password ?? '',
      domain: source.domain ?? '',
      workstation: '',
      body: soap,
      timeout: EWS_TIMEOUT_MS,
      headers: {
        'Content-Type': 'text/xml; charset=utf-8',
        'SOAPAction': `"http://schemas.microsoft.com/exchange/services/2006/messages/${action}"`,
      },
    });
  }

  /**
   * Tests Graph API connection by requesting calendar list.
   */
  private async testGraphConnection(
    source: { url: string; password?: string },
  ): Promise<boolean> {
    const { Client: GraphClient } = await import(
      '@microsoft/microsoft-graph-client'
    );

    const client = GraphClient.init({
      authProvider: (done: AuthProviderCallback) => {
        done(null, source.password || '');
      },
    });

    const result = await client.api('/me/calendars').top(1).get();
    return !!result?.value;
  }

  /**
   * Tests EWS connection using NTLM auth — GetFolder on calendar folder.
   */
  private async testEwsConnection(
    source: { url: string; username?: string; password?: string; domain?: string },
  ): Promise<boolean> {
    const soap = soapEnvelope(`
      <m:GetFolder>
        <m:FolderShape>
          <t:BaseShape>IdOnly</t:BaseShape>
        </m:FolderShape>
        <m:FolderIds>
          <t:DistinguishedFolderId Id="calendar"/>
        </m:FolderIds>
      </m:GetFolder>`);

    const res = await this.ewsNtlmPost(source, soap, 'GetFolder');
    return res.statusCode === 200 && !res.body.includes('ResponseClass="Error"');
  }
}