/**
 * Centralized API Configuration
 *
 * This module provides a single source of truth for all API endpoints and URLs.
 * All components should import from here instead of reading environment variables directly.
 *
 * Runtime config injection:
 * - In production containers, NEXT_PUBLIC_* vars are baked at build time and cannot
 *   be overridden via Docker env vars.  The root layout injects runtime values into
 *   `window.__MOSAIC_ENV__` via a synchronous <script>, which this module reads first.
 *
 * Environment Variables:
 * - NEXT_PUBLIC_API_URL: The main API server URL (default: http://localhost:3001)
 * - NEXT_PUBLIC_ORCHESTRATOR_URL: The orchestrator service URL (default: same as API URL)
 * - NEXT_PUBLIC_AUTH_MODE: Auth mode for web app (`real` or `mock`)
 *   - If unset: development defaults to `mock`, production defaults to `real`
 */

/**
 * Read an env variable, preferring runtime-injected values on the client.
 *
 * Execution order guarantees this works:
 * 1. Root layout emits `<script>window.__MOSAIC_ENV__={…}</script>` synchronously.
 * 2. Next.js hydrates, loading client modules that call this helper.
 */
function getEnv(name: string): string | undefined {
  if (typeof window !== "undefined") {
    const w = window as Window & { __MOSAIC_ENV__?: Record<string, string> };
    if (w.__MOSAIC_ENV__?.[name]) {
      return w.__MOSAIC_ENV__[name];
    }
  }
  // Server-side or build-time fallback
  return process.env[name];
}

/**
 * Default API server URL for local development
 */
const DEFAULT_API_URL = "http://localhost:3001";
const DEFAULT_AUTH_MODE = process.env.NODE_ENV === "development" ? "mock" : "real";

const VALID_AUTH_MODES = ["real", "mock"] as const;

export type AuthMode = (typeof VALID_AUTH_MODES)[number];

/**
 * Main API server URL
 * Used for authentication, tasks, events, knowledge, and all core API calls
 */
export const API_BASE_URL = getEnv("NEXT_PUBLIC_API_URL") ?? DEFAULT_API_URL;

function resolveAuthMode(): AuthMode {
  const rawMode = (getEnv("NEXT_PUBLIC_AUTH_MODE") ?? DEFAULT_AUTH_MODE).toLowerCase();

  if (!VALID_AUTH_MODES.includes(rawMode as AuthMode)) {
    throw new Error(
      `Invalid NEXT_PUBLIC_AUTH_MODE "${rawMode}". Expected one of: ${VALID_AUTH_MODES.join(", ")}.`
    );
  }

  if (rawMode === "mock" && process.env.NODE_ENV !== "development") {
    throw new Error("NEXT_PUBLIC_AUTH_MODE=mock is only allowed when NODE_ENV=development.");
  }

  return rawMode as AuthMode;
}

/**
 * Authentication mode for frontend runtime.
 * - real: uses normal BetterAuth/Backend session flow
 * - mock: local-only seeded mock user for FE development
 */
export const AUTH_MODE: AuthMode = resolveAuthMode();

/**
 * Whether local mock auth mode is enabled.
 */
export const IS_MOCK_AUTH_MODE = AUTH_MODE === "mock";

/**
 * Orchestrator service URL
 * Used for agent management, task progress, and orchestration features
 * Falls back to main API URL if not specified (they may run on the same server)
 */
export const ORCHESTRATOR_URL = getEnv("NEXT_PUBLIC_ORCHESTRATOR_URL") ?? API_BASE_URL;

/**
 * Build a full API endpoint URL
 * @param endpoint - The API endpoint path (should start with /)
 * @returns The full URL for the endpoint
 */
export function buildApiUrl(endpoint: string): string {
  return `${API_BASE_URL}${endpoint}`;
}

/**
 * Build a full orchestrator endpoint URL
 * @param endpoint - The orchestrator endpoint path (should start with /)
 * @returns The full URL for the endpoint
 */
export function buildOrchestratorUrl(endpoint: string): string {
  return `${ORCHESTRATOR_URL}${endpoint}`;
}

/**
 * Configuration object for convenient access to all URLs
 */
export const apiConfig = {
  /** Main API base URL */
  baseUrl: API_BASE_URL,
  /** Orchestrator service URL */
  orchestratorUrl: ORCHESTRATOR_URL,
  /** Authentication mode (`real` or `mock`) */
  authMode: AUTH_MODE,
  /** Build full API URL for an endpoint */
  buildUrl: buildApiUrl,
  /** Build full orchestrator URL for an endpoint */
  buildOrchestratorUrl,
} as const;