import {
  Controller,
  Get,
  HttpCode,
  HttpStatus,
  Post,
  Req,
  Res,
  UnauthorizedException,
} from '@nestjs/common';
import { ApiTags } from '@nestjs/swagger';
import { Throttle } from '@nestjs/throttler';
import type { Request, Response } from 'express';
import { Public } from '../decorators/public.decorator';
import { AuthService } from '../auth.service';
import { MfaRequiredResponse } from '../auth.controller';
import { AccessTokenDto } from '../dto/access-token.dto';
import { SENSITIVE_ACTION_THROTTLE } from '../util/throttle';
import { setRefreshTokenCookie } from '../util/refresh-token-cookie';
import { SsoService } from './sso.service';

const PKCE_COOKIE = 'oidcPkceVerifier';
const PKCE_COOKIE_PATH = '/api/v1/auth/sso';
const PKCE_COOKIE_MAX_AGE_MS = 5 * 60 * 1000;

// Scoped to /complete only - the completion endpoint is the only place that
// ever needs to read it, and it's never sent on the wider /auth/sso/* path.
const SSO_CODE_COOKIE = 'oidcSsoCode';
const SSO_CODE_COOKIE_PATH = '/api/v1/auth/sso/complete';
const SSO_CODE_COOKIE_MAX_AGE_MS = 60 * 1000;

interface PkceCookiePayload {
  codeVerifier: string;
  state: string;
}

@ApiTags('auth')
@Controller('auth/sso')
export class SsoController {
  constructor(
    private readonly ssoService: SsoService,
    private readonly authService: AuthService,
  ) {}

  private frontendLoginUrl(): string {
    return `${process.env.FRONTEND_ORIGIN ?? 'http://localhost:3000'}/login`;
  }

  private cookieOptions(path: string, maxAge: number) {
    return {
      httpOnly: true,
      secure: process.env.COOKIE_SECURE !== 'false',
      sameSite: 'lax' as const,
      path,
      maxAge,
    };
  }

  @Public()
  @Get('status')
  status(): { enabled: boolean } {
    return { enabled: this.ssoService.isConfigured() };
  }

  @Public()
  @Get('login')
  async login(@Res() res: Response): Promise<void> {
    const { redirectUrl, codeVerifier, state } =
      await this.ssoService.buildAuthorizationRequest();
    const payload: PkceCookiePayload = { codeVerifier, state };
    res.cookie(
      PKCE_COOKIE,
      JSON.stringify(payload),
      this.cookieOptions(PKCE_COOKIE_PATH, PKCE_COOKIE_MAX_AGE_MS),
    );
    res.redirect(redirectUrl);
  }

  @Public()
  @Get('callback')
  async callback(@Req() req: Request, @Res() res: Response): Promise<void> {
    const rawCookie = (req.cookies as Record<string, string> | undefined)?.[
      PKCE_COOKIE
    ];
    res.clearCookie(PKCE_COOKIE, this.cookieOptions(PKCE_COOKIE_PATH, 0));

    const pkce = this.parsePkceCookie(rawCookie);
    if (!pkce) {
      res.redirect(`${this.frontendLoginUrl()}?ssoError=session_expired`);
      return;
    }

    // Built from the configured redirect URI, not from the Host header a
    // client sends; only the query (code, state, iss) comes from the request.
    const callbackUrl = new URL(process.env.OIDC_REDIRECT_URI as string);
    callbackUrl.search = new URL(req.originalUrl, 'http://placeholder').search;
    const result = await this.ssoService.handleCallback(
      callbackUrl,
      pkce.codeVerifier,
      pkce.state,
    );
    if (result.status === 'error') {
      res.redirect(`${this.frontendLoginUrl()}?ssoError=${result.reason}`);
      return;
    }

    // The one-time completion code never touches the URL (history, server
    // logs, Referer headers) - it travels only in an httpOnly cookie scoped
    // to the /complete endpoint, which the frontend calls right after.
    res.cookie(
      SSO_CODE_COOKIE,
      result.ssoCode,
      this.cookieOptions(SSO_CODE_COOKIE_PATH, SSO_CODE_COOKIE_MAX_AGE_MS),
    );
    res.redirect(`${this.frontendLoginUrl()}?ssoPending=1`);
  }

  @Public()
  @Throttle(SENSITIVE_ACTION_THROTTLE)
  @Post('complete')
  @HttpCode(HttpStatus.OK)
  async complete(
    @Req() req: Request,
    @Res({ passthrough: true }) res: Response,
  ): Promise<AccessTokenDto | MfaRequiredResponse> {
    const ssoCode = (req.cookies as Record<string, string> | undefined)?.[
      SSO_CODE_COOKIE
    ];
    res.clearCookie(
      SSO_CODE_COOKIE,
      this.cookieOptions(SSO_CODE_COOKIE_PATH, 0),
    );
    if (!ssoCode) {
      throw new UnauthorizedException(
        'SSO-Anmeldung abgelaufen, bitte erneut versuchen',
      );
    }
    const { userId } = this.ssoService.verifySsoCode(ssoCode);
    const result = await this.authService.issueTokensForSsoUser(userId);
    if (result.mfaRequired) {
      return { mfaRequired: true, mfaToken: result.mfaToken };
    }
    setRefreshTokenCookie(res, result.refreshToken);
    return { accessToken: result.accessToken };
  }

  private parsePkceCookie(raw: string | undefined): PkceCookiePayload | null {
    if (!raw) {
      return null;
    }
    try {
      const parsed = JSON.parse(raw) as Partial<PkceCookiePayload>;
      if (
        typeof parsed.codeVerifier !== 'string' ||
        typeof parsed.state !== 'string'
      ) {
        return null;
      }
      return { codeVerifier: parsed.codeVerifier, state: parsed.state };
    } catch {
      return null;
    }
  }
}