import { createHash, randomBytes, randomUUID } from 'node:crypto';
import { WORKS_SQUARE_CONFIG } from '../api/works-config';
import { proxyAwareFetch } from '../utils/proxy-fetch';
import type { WorksSquareTokenPayload } from './works-square-session';

const DEFAULT_CLIENT_ID = 'makelore';
const DEFAULT_SCOPE = 'openid profile phone offline_access';
const REDIRECT_URI = 'niancode://auth/callback';
const STATE_TTL_MS = 10 * 60_000;

type PlatformAuthMetadata = {
  authorization_endpoint: string;
  token_endpoint: string;
};

type PendingAuthorization = {
  state: string;
  codeVerifier: string;
  expiresAt: number;
};

const pendingAuthorizations = new Map<string, PendingAuthorization>();
let metadataPromise: Promise<PlatformAuthMetadata> | null = null;

function configuredIssuer(): string {
  const raw = (process.env.PLATFORM_AUTH_ISSUER || WORKS_SQUARE_CONFIG.apiBaseUrl).trim().replace(/\/+$/, '');
  const parsed = new URL(raw);
  if (!['http:', 'https:'].includes(parsed.protocol) || parsed.username || parsed.password || parsed.search || parsed.hash) {
    throw new Error('PLATFORM_AUTH_ISSUER must be an absolute HTTP(S) URL without credentials or query parameters');
  }
  return parsed.toString().replace(/\/$/, '');
}

function configuredClientId(): string {
  return process.env.PLATFORM_AUTH_CLIENT_ID?.trim() || DEFAULT_CLIENT_ID;
}

function configuredScope(): string {
  return process.env.PLATFORM_AUTH_SCOPE?.trim() || DEFAULT_SCOPE;
}

function absoluteHttpUrl(value: unknown, field: string): string {
  if (typeof value !== 'string' || !value.trim()) throw new Error(`OIDC discovery missing ${field}`);
  const parsed = new URL(value);
  if (!['http:', 'https:'].includes(parsed.protocol) || parsed.username || parsed.password) {
    throw new Error(`OIDC discovery returned an invalid ${field}`);
  }
  return parsed.toString();
}

async function loadMetadata(): Promise<PlatformAuthMetadata> {
  const issuer = configuredIssuer();
  const response = await proxyAwareFetch(`${issuer}/.well-known/openid-configuration`, {
    method: 'GET',
    headers: { Accept: 'application/json' },
  });
  if (!response.ok) throw new Error(`OIDC discovery failed (${response.status})`);
  const payload = await response.json() as Record<string, unknown>;
  return {
    authorization_endpoint: absoluteHttpUrl(payload.authorization_endpoint, 'authorization_endpoint'),
    token_endpoint: absoluteHttpUrl(payload.token_endpoint, 'token_endpoint'),
  };
}

async function getMetadata(): Promise<PlatformAuthMetadata> {
  if (!metadataPromise) {
    metadataPromise = loadMetadata().catch((error) => {
      metadataPromise = null;
      throw error;
    });
  }
  return metadataPromise;
}

function takePendingAuthorization(
  requestId: string | null,
  returnedState: string,
): PendingAuthorization | null {
  if (requestId) {
    const pending = pendingAuthorizations.get(requestId);
    pendingAuthorizations.delete(requestId);
    return pending ?? null;
  }

  // The platform redirect is a fixed niancode:// URI and does not append our
  // local request id. The state value is the OIDC correlation handle instead.
  for (const [candidateId, pending] of pendingAuthorizations) {
    if (pending.state === returnedState) {
      pendingAuthorizations.delete(candidateId);
      return pending;
    }
  }
  return null;
}

function cleanupPendingAuthorizations(now = Date.now()): void {
  for (const [requestId, pending] of pendingAuthorizations) {
    if (pending.expiresAt <= now) pendingAuthorizations.delete(requestId);
  }
}

function codeChallengeS256(verifier: string): string {
  return createHash('sha256').update(verifier, 'ascii').digest('base64url');
}

function readTokenPayload(value: unknown): WorksSquareTokenPayload {
  if (!value || typeof value !== 'object' || Array.isArray(value)) {
    throw new Error('OIDC token endpoint returned an invalid response');
  }
  const payload = value as WorksSquareTokenPayload;
  if (typeof payload.access_token !== 'string' || !payload.access_token.trim()) {
    throw new Error('OIDC token endpoint did not return access_token');
  }
  return payload;
}

export async function startPlatformAuthorization(): Promise<{
  requestId: string;
  authorizationUrl: string;
}> {
  cleanupPendingAuthorizations();
  const metadata = await getMetadata();
  const requestId = randomUUID();
  const state = randomBytes(32).toString('base64url');
  const codeVerifier = randomBytes(64).toString('base64url');
  pendingAuthorizations.set(requestId, {
    state,
    codeVerifier,
    expiresAt: Date.now() + STATE_TTL_MS,
  });

  const url = new URL(metadata.authorization_endpoint);
  url.searchParams.set('client_id', configuredClientId());
  url.searchParams.set('response_type', 'code');
  url.searchParams.set('redirect_uri', REDIRECT_URI);
  url.searchParams.set('scope', configuredScope());
  url.searchParams.set('state', state);
  url.searchParams.set('nonce', randomBytes(32).toString('base64url'));
  url.searchParams.set('code_challenge', codeChallengeS256(codeVerifier));
  url.searchParams.set('code_challenge_method', 'S256');

  return { requestId, authorizationUrl: url.toString() };
}

export async function completePlatformAuthorization(
  requestId: string | null,
  code: string,
  returnedState: string,
): Promise<WorksSquareTokenPayload> {
  cleanupPendingAuthorizations();
  const pending = takePendingAuthorization(requestId, returnedState);
  if (!pending || pending.expiresAt <= Date.now()) throw new Error('OIDC authorization request expired');
  if (pending.state !== returnedState) throw new Error('OIDC authorization state mismatch');

  const metadata = await getMetadata();
  const response = await proxyAwareFetch(metadata.token_endpoint, {
    method: 'POST',
    headers: { 'Content-Type': 'application/x-www-form-urlencoded', Accept: 'application/json' },
    body: new URLSearchParams({
      grant_type: 'authorization_code',
      code,
      redirect_uri: REDIRECT_URI,
      client_id: configuredClientId(),
      code_verifier: pending.codeVerifier,
    }).toString(),
  });
  if (!response.ok) {
    const detail = await response.text();
    throw new Error(`OIDC token exchange failed (${response.status}): ${detail.slice(0, 180)}`);
  }
  return readTokenPayload(await response.json());
}

export function resetPlatformAuthorizationForTests(): void {
  pendingAuthorizations.clear();
  metadataPromise = null;
}

export const PLATFORM_AUTH_REDIRECT_URI = REDIRECT_URI;