import type { Env } from './env';

export const AUTH_SESSION_COOKIE_NAME = 'heygo_session' as const;

export const AUTH_ENABLED_PROVIDERS = ['google', 'github'] as const;
export const AUTH_DISABLED_PROVIDERS = ['apple'] as const;

export type EnabledAuthProvider = (typeof AUTH_ENABLED_PROVIDERS)[number];
export type DisabledAuthProvider = (typeof AUTH_DISABLED_PROVIDERS)[number];
export type AuthProvider = EnabledAuthProvider | DisabledAuthProvider;

export interface AuthUser {
  id: string;
  email: string | null;
  name: string | null;
  imageUrl: string | null;
  role: 'user' | 'admin';
}

export interface AuthSession {
  id: string;
  userId: string;
  expiresAt: string;
}

const ENABLED_PROVIDER_SET = new Set<string>(AUTH_ENABLED_PROVIDERS);
const ADMIN_EMAIL_SPLIT_PATTERN = /[\s,;]+/;

export function isAuthProviderEnabled(provider: string): provider is EnabledAuthProvider {
  return ENABLED_PROVIDER_SET.has(provider);
}

export function getSessionCookieAttributes(
  requestUrl: string | URL,
  cookieDomain: string,
): string[] {
  // The request URL is retained so callers can derive a host-specific domain in
  // the future; the shared Domain attribute now comes from the COOKIE_DOMAIN
  // env var so each deployment (dev/prod/local) controls its own scope.
  const url = typeof requestUrl === 'string' ? new URL(requestUrl) : requestUrl;
  const attributes = ['HttpOnly', 'SameSite=Lax', 'Path=/'];

  // Only set Secure over HTTPS. Local dev (wrangler dev) runs on HTTP;
  // a Secure cookie would be silently dropped by the browser.
  if (url.protocol === 'https:') {
    attributes.push('Secure');
  }

  if (cookieDomain) {
    attributes.push(`Domain=${cookieDomain}`);
  }

  return attributes;
}

export class AuthError extends Error {
  readonly status: number;

  constructor(status: number, message: string) {
    super(message);
    this.name = 'AuthError';
    this.status = status;
  }

  toResponse(): Response {
    return Response.json({ error: this.message }, { status: this.status });
  }
}

export function parseCookieHeader(cookieHeader: string | null | undefined): Record<string, string> {
  const cookies: Record<string, string> = {};

  if (!cookieHeader) {
    return cookies;
  }

  for (const part of cookieHeader.split(';')) {
    const equalsIndex = part.indexOf('=');
    if (equalsIndex === -1) {
      continue;
    }

    const key = part.slice(0, equalsIndex).trim();
    const value = part.slice(equalsIndex + 1).trim();

    if (key) {
      cookies[key] = value;
    }
  }

  return cookies;
}

export async function hashSessionToken(token: string): Promise<string> {
  const data = new TextEncoder().encode(token);
  const digest = await crypto.subtle.digest('SHA-256', data);
  return bufferToHex(digest);
}

export function getConfiguredAdminEmails(env: Pick<Env, 'ADMIN_EMAILS'>): Set<string> {
  const raw = env.ADMIN_EMAILS?.trim();
  if (!raw) {
    return new Set();
  }

  return new Set(
    raw
      .split(ADMIN_EMAIL_SPLIT_PATTERN)
      .map((email) => email.trim().toLowerCase())
      .filter(Boolean),
  );
}

export function isConfiguredAdminEmail(
  email: string | null | undefined,
  env: Pick<Env, 'ADMIN_EMAILS'>,
): boolean {
  if (!email) {
    return false;
  }

  return getConfiguredAdminEmails(env).has(email.trim().toLowerCase());
}

function bufferToHex(buffer: ArrayBuffer): string {
  const bytes = new Uint8Array(buffer);
  let hex = '';
  for (const byte of bytes) {
    hex += byte.toString(16).padStart(2, '0');
  }
  return hex;
}

const SESSION_USER_QUERY = `SELECT users.id, users.email, users.name, users.image_url, users.role, sessions.expires_at
FROM sessions JOIN users ON users.id = sessions.user_id
WHERE sessions.session_token_hash = ?
LIMIT 1`;

type SessionUserRow = {
  id: string;
  email: string | null;
  name: string | null;
  image_url: string | null;
  role: 'user' | 'admin';
  expires_at: string;
};

export async function getCurrentUser(request: Request, env: Env): Promise<AuthUser | null> {
  const cookieHeader = request.headers.get('cookie');
  if (!cookieHeader) {
    return null;
  }

  const cookies = parseCookieHeader(cookieHeader);
  const sessionToken = cookies[AUTH_SESSION_COOKIE_NAME];
  if (!sessionToken) {
    return null;
  }

  const tokenHash = await hashSessionToken(sessionToken);

  const row = await env.DB.prepare(SESSION_USER_QUERY).bind(tokenHash).first<SessionUserRow>();
  if (!row) {
    return null;
  }

  const expiresAt = Date.parse(row.expires_at);
  if (Number.isNaN(expiresAt) || expiresAt <= Date.now()) {
    return null;
  }

  return {
    id: row.id,
    email: row.email,
    name: row.name,
    imageUrl: row.image_url,
    role: isConfiguredAdminEmail(row.email, env) ? 'admin' : row.role,
  };
}

export async function requireUser(request: Request, env: Env): Promise<AuthUser> {
  const user = await getCurrentUser(request, env);
  if (!user) {
    throw new AuthError(401, 'Authentication required');
  }
  return user;
}

export async function requireAdmin(request: Request, env: Env): Promise<AuthUser> {
  const user = await requireUser(request, env);
  if (user.role !== 'admin') {
    throw new AuthError(403, 'Admin access required');
  }
  return user;
}