import { NextRequest, NextResponse } from 'next/server';
import { cookies } from 'next/headers';
import { logger } from '@/lib/logger';
import { discoverOAuth } from '@/lib/oauth/discovery';
import { refreshTokenCookieName } from '@/lib/oauth/tokens';

const CLIENT_SECRET = process.env.OAUTH_CLIENT_SECRET || '';

const COOKIE_OPTIONS = {
  httpOnly: true,
  secure: process.env.NODE_ENV === 'production',
  sameSite: 'lax' as const,
  path: '/',
  maxAge: 30 * 24 * 60 * 60,
};

function getSlot(request: NextRequest): number {
  const raw = request.nextUrl.searchParams.get('slot');
  if (raw === null) return 0;
  const slot = parseInt(raw, 10);
  if (isNaN(slot) || slot < 0 || slot > 4) return 0;
  return slot;
}


function getRequiredConfig() {
  const clientId = process.env.OAUTH_CLIENT_ID;
  const serverUrl = process.env.JMAP_SERVER_URL || process.env.NEXT_PUBLIC_JMAP_SERVER_URL;
  const issuerUrl = process.env.OAUTH_ISSUER_URL;
  if (!clientId || !serverUrl) {
    throw new Error(`OAuth misconfigured: ${[!clientId && 'OAUTH_CLIENT_ID', !serverUrl && 'JMAP_SERVER_URL'].filter(Boolean).join(', ')} not set`);
  }
  const discoveryUrl = issuerUrl?.trim() || serverUrl;
  if (issuerUrl !== undefined && !issuerUrl.trim()) {
    logger.warn('OAUTH_ISSUER_URL is set but empty, falling back to JMAP_SERVER_URL for discovery');
  }
  return { clientId, serverUrl, discoveryUrl };
}

async function getTokenEndpoint(): Promise<string> {
  const { discoveryUrl } = getRequiredConfig();
  const metadata = await discoverOAuth(discoveryUrl);
  if (!metadata?.token_endpoint) {
    throw new Error('OAuth token endpoint not found');
  }
  return metadata.token_endpoint;
}

async function getMetadata(): Promise<import('@/lib/oauth/discovery').OAuthMetadata | null> {
  const { discoveryUrl } = getRequiredConfig();
  return discoverOAuth(discoveryUrl);
}

function buildOAuthParams(base: Record<string, string>): URLSearchParams {
  const { clientId } = getRequiredConfig();
  const params = new URLSearchParams({ ...base, client_id: clientId });
  if (CLIENT_SECRET) {
    params.set('client_secret', CLIENT_SECRET);
  }
  return params;
}

export async function POST(request: NextRequest) {
  try {
    const { code, code_verifier, redirect_uri, slot: bodySlot } = await request.json();

    if (!code || !code_verifier || !redirect_uri) {
      return NextResponse.json({ error: 'Missing required parameters' }, { status: 400 });
    }

    const slot = typeof bodySlot === 'number' && bodySlot >= 0 && bodySlot <= 4 ? bodySlot : getSlot(request);
    const tokenEndpoint = await getTokenEndpoint();

    const params = buildOAuthParams({
      grant_type: 'authorization_code',
      code,
      redirect_uri,
      code_verifier,
    });

    const tokenResponse = await fetch(tokenEndpoint, {
      method: 'POST',
      headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
      body: params.toString(),
    });

    if (!tokenResponse.ok) {
      const errorText = await tokenResponse.text();
      logger.error('Token exchange failed', { status: tokenResponse.status, error: errorText });
      return NextResponse.json({ error: 'Token exchange failed' }, { status: 401 });
    }

    const tokens = await tokenResponse.json();

    if (!tokens.access_token) {
      logger.error('Token response missing access_token', { response: JSON.stringify(tokens).substring(0, 500) });
      return NextResponse.json({ error: 'Invalid token response' }, { status: 502 });
    }

    const response = NextResponse.json({
      access_token: tokens.access_token,
      expires_in: tokens.expires_in || 3600,
    });

    if (tokens.refresh_token) {
      const cookieName = refreshTokenCookieName(slot);
      const cookieStore = await cookies();
      cookieStore.set(cookieName, tokens.refresh_token, COOKIE_OPTIONS);
    }

    return response;
  } catch (error) {
    logger.error('Token exchange error', { error: error instanceof Error ? error.message : 'Unknown error' });
    return NextResponse.json({ error: 'Internal server error' }, { status: 500 });
  }
}

export async function PUT(request: NextRequest) {
  try {
    const slot = getSlot(request);
    const cookieName = refreshTokenCookieName(slot);
    const cookieStore = await cookies();
    const refreshToken = cookieStore.get(cookieName)?.value;

    if (!refreshToken) {
      return NextResponse.json({ error: 'No refresh token' }, { status: 401 });
    }

    const tokenEndpoint = await getTokenEndpoint();

    const params = buildOAuthParams({
      grant_type: 'refresh_token',
      refresh_token: refreshToken,
    });

    const tokenResponse = await fetch(tokenEndpoint, {
      method: 'POST',
      headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
      body: params.toString(),
    });

    if (!tokenResponse.ok) {
      const errorText = await tokenResponse.text();
      logger.error('Token refresh failed', { status: tokenResponse.status, error: errorText });
      cookieStore.delete(cookieName);
      return NextResponse.json({ error: 'Refresh failed' }, { status: 401 });
    }

    const tokens = await tokenResponse.json();

    if (!tokens.access_token) {
      logger.error('Refresh response missing access_token', { response: JSON.stringify(tokens).substring(0, 500) });
      return NextResponse.json({ error: 'Invalid token response' }, { status: 502 });
    }

    if (tokens.refresh_token) {
      cookieStore.set(cookieName, tokens.refresh_token, COOKIE_OPTIONS);
    }

    return NextResponse.json({
      access_token: tokens.access_token,
      expires_in: tokens.expires_in || 3600,
    });
  } catch (error) {
    logger.error('Token refresh error', { error: error instanceof Error ? error.message : 'Unknown error' });
    return NextResponse.json({ error: 'Internal server error' }, { status: 500 });
  }
}

export async function DELETE(request: NextRequest) {
  try {
    const all = request.nextUrl.searchParams.get('all') === 'true';

    if (all) {
      // Revoke and delete all refresh token cookies (slots 0-4)
      const cookieStore = await cookies();
      for (let i = 0; i <= 4; i++) {
        const name = refreshTokenCookieName(i);
        const token = cookieStore.get(name)?.value;
        if (token) {
          // Best-effort revocation
          try {
            const metadata = await getMetadata().catch(() => null);
            if (metadata?.revocation_endpoint) {
              const params = buildOAuthParams({ token, token_type_hint: 'refresh_token' });
              await fetch(metadata.revocation_endpoint, {
                method: 'POST',
                headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
                body: params.toString(),
              }).catch(() => {});
            }
          } catch { /* best effort */ }
          cookieStore.delete(name);
        }
      }
      return NextResponse.json({ ok: true });
    }

    const slot = getSlot(request);
    const cookieName = refreshTokenCookieName(slot);
    const cookieStore = await cookies();
    const refreshToken = cookieStore.get(cookieName)?.value;
    const metadata = await getMetadata().catch((err) => {
      logger.warn('Failed to discover OAuth metadata during logout', {
        error: err instanceof Error ? err.message : 'Unknown error',
      });
      return null;
    });

    if (refreshToken) {
      if (metadata?.revocation_endpoint) {
        const params = buildOAuthParams({
          token: refreshToken,
          token_type_hint: 'refresh_token',
        });

        try {
          const revocationResponse = await fetch(metadata.revocation_endpoint, {
            method: 'POST',
            headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
            body: params.toString(),
          });
          if (!revocationResponse.ok) {
            logger.warn('Token revocation returned error', { status: revocationResponse.status });
          }
        } catch (err) {
          logger.error('Token revocation network error', { error: err instanceof Error ? err.message : 'Unknown error' });
        }
      }

      cookieStore.delete(cookieName);
    }

    let end_session_url: string | undefined;
    if (metadata?.end_session_endpoint) {
      try {
        const parsed = new URL(metadata.end_session_endpoint);
        if (parsed.protocol === 'https:') {
          end_session_url = metadata.end_session_endpoint;
        } else {
          logger.warn('Ignoring non-HTTPS end_session_endpoint', { url: metadata.end_session_endpoint });
        }
      } catch {
        logger.warn('Invalid end_session_endpoint URL', { url: metadata.end_session_endpoint });
      }
    }

    return NextResponse.json({ ok: true, ...(end_session_url && { end_session_url }) });
  } catch (error) {
    logger.error('Token revocation error', { error: error instanceof Error ? error.message : 'Unknown error' });
    return NextResponse.json({ error: 'Internal server error' }, { status: 500 });
  }
}