/**
 * Shared utilities for CLI commands (dev, start, run).
 *
 * This module extracts common patterns used across different launch modes
 * to reduce duplication and ensure consistent behavior.
 */

import type { ChildProcess } from "node:child_process";
import os from "node:os";

import { DEFAULT_AGENTCTL_PORT, DEFAULT_BACKEND_PORT, DEFAULT_WEB_PORT } from "./constants";
import { pickAvailablePort } from "./ports";
import { createProcessSupervisor } from "./process";

export type PortConfig = {
  backendPort: number;
  webPort?: number;
  agentctlPort: number;
  backendUrl: string;
};

/**
 * Picks available ports for all services, using provided values or finding free ports.
 *
 * @param backendPort - Optional preferred backend port
 * @param webPort - Optional preferred web port
 * @returns Resolved ports for all services
 */
export async function pickPorts(backendPort?: number, webPort?: number): Promise<PortConfig> {
  const resolvedBackendPort = backendPort ?? (await pickAvailablePort(DEFAULT_BACKEND_PORT));
  const resolvedWebPort = webPort ?? (await pickAvailablePort(DEFAULT_WEB_PORT));
  const agentctlPort = await pickAvailablePort(DEFAULT_AGENTCTL_PORT);

  return {
    backendPort: resolvedBackendPort,
    webPort: resolvedWebPort,
    agentctlPort,
    backendUrl: `http://localhost:${resolvedBackendPort}`,
  };
}

export async function pickBackendPorts(backendPort?: number): Promise<PortConfig> {
  const resolvedBackendPort = backendPort ?? (await pickAvailablePort(DEFAULT_BACKEND_PORT));
  const agentctlPort = await pickAvailablePort(DEFAULT_AGENTCTL_PORT);

  return {
    backendPort: resolvedBackendPort,
    agentctlPort,
    backendUrl: `http://localhost:${resolvedBackendPort}`,
  };
}

export type BackendEnvOptions = {
  ports: PortConfig;
  /** Log level: debug, info, warn, error (default: info) */
  logLevel?: string;
  /** Route browser pages through an external dev web server. Production serves the SPA from Go. */
  webProxy?: boolean;
  /** Additional environment variables to merge */
  extra?: Record<string, string>;
};

/**
 * Builds environment variables for the backend process.
 *
 * @param options - Configuration options for the backend environment
 * @returns Environment object for the backend process
 */
export function buildBackendEnv(options: BackendEnvOptions): NodeJS.ProcessEnv {
  const { ports, logLevel, webProxy = true, extra } = options;
  if (webProxy && ports.webPort === undefined) {
    throw new Error("webProxy requires a web port");
  }
  const env: NodeJS.ProcessEnv = {
    ...process.env,
    KANDEV_SERVER_PORT: String(ports.backendPort),
    ...(webProxy ? { KANDEV_WEB_INTERNAL_URL: `http://localhost:${ports.webPort}` } : {}),
    KANDEV_AGENT_STANDALONE_PORT: String(ports.agentctlPort),
    ...(logLevel ? { KANDEV_LOG_LEVEL: logLevel } : {}),
    ...extra,
  };
  if (!webProxy) {
    delete env.KANDEV_WEB_INTERNAL_URL;
  }
  return env;
}

export type WebEnvOptions = {
  ports: PortConfig;
  /** Set NODE_ENV to production */
  production?: boolean;
  /** Enable debug mode */
  debug?: boolean;
};

/**
 * Builds environment variables for the web process.
 *
 * @param options - Configuration options for the web environment
 * @returns Environment object for the web process
 */
export function buildWebEnv(options: WebEnvOptions): NodeJS.ProcessEnv {
  const { ports, production = false, debug = false } = options;
  if (ports.webPort === undefined) {
    throw new Error("web env requires a web port");
  }

  const env: NodeJS.ProcessEnv = {
    ...process.env,
    // Internal Vite/server tooling config. Browser traffic enters through Go
    // in every mode so frontend code should use same-origin API/WS URLs.
    KANDEV_API_BASE_URL: ports.backendUrl,
    PORT: String(ports.webPort),
    HOSTNAME: "127.0.0.1",
  };

  if (production) {
    (env as Record<string, string>).NODE_ENV = "production";
  }
  // Explicitly unset so a host-level VITE_KANDEV_API_PORT (from a .env file,
  // Docker env, or CI variable) cannot leak through the process.env spread and
  // reintroduce cross-origin browser API calls.
  delete env.VITE_KANDEV_API_PORT;

  if (debug) {
    env.KANDEV_DEBUG = "true";
    env.VITE_KANDEV_DEBUG = "true";
  }

  return env;
}

/**
 * Returns the host's non-loopback, non-internal IPv4/IPv6 addresses. Used to
 * print LAN / Tailscale / SSH-forwarded browser URLs in the startup banner.
 */
export function listHostNetworkAddresses(): string[] {
  const v4: string[] = [];
  const v6: string[] = [];
  const seen = new Set<string>();
  const interfaces = os.networkInterfaces();
  for (const addrs of Object.values(interfaces)) {
    if (!addrs) continue;
    for (const addr of addrs) {
      if (addr.internal) continue;
      // Skip link-local IPv6 (fe80::/10) and link-local IPv4 (169.254.0.0/16,
      // RFC 3927) — neither is reachable from a remote machine, and the
      // 169.254 range in particular is what Hyper-V assigns to its phantom
      // WSL adapter, which clutters the startup output. The regex covers the
      // full /10 (fe80::–febf::); OS stacks only assign fe80::/64 in practice
      // but a stricter check is the same effort and removes the surprise.
      if (addr.family === "IPv6" && /^fe[89ab]/i.test(addr.address)) continue;
      if (addr.family === "IPv4" && addr.address.startsWith("169.254.")) continue;
      if (seen.has(addr.address)) continue;
      seen.add(addr.address);
      if (addr.family === "IPv4") v4.push(addr.address);
      else v6.push(addr.address);
    }
  }
  // IPv4 first — LAN + Tailscale IPv4 are what people usually want.
  return [...v4, ...v6];
}

export type StartupInfoOptions = {
  /** Mode header line, e.g. "dev mode: using local repo" or "release: v0.0.12 (github latest)" */
  header: string;
  ports: PortConfig;
  /**
   * Which port a user actually opens in a browser. Normal `dev`/`start`/`run`
   * use the Go backend as the entrypoint; `primary: "web"` is retained for
   * diagnostics. Network URLs are only listed under this port — the other one
   * is internal-only. Defaults to "backend".
   */
  primary?: "backend" | "web";
  /** Database file path */
  dbPath?: string;
  /** Log level being used */
  logLevel?: string;
};

/**
 * Logs a unified startup info block to the console.
 *
 * Shows only the URL the user actually opens. The other web/Vite port and the
 * agentctl port are internal plumbing and would only mislead. Below the URL,
 * lists the same port on each non-loopback interface (LAN, Tailscale) so a
 * user opening the app remotely sees the right address.
 */
export function logStartupInfo(options: StartupInfoOptions): void {
  const { header, ports, primary = "backend", dbPath, logLevel } = options;
  let primaryPort = ports.backendPort;
  if (primary === "web") {
    if (ports.webPort === undefined) {
      throw new Error("web startup info requires a web port");
    }
    primaryPort = ports.webPort;
  }
  const primaryUrl = `http://localhost:${primaryPort}`;
  const networkHosts = listHostNetworkAddresses();

  console.log(`[kandev] ${header}`);
  console.log("[kandev] url:", primaryUrl);
  for (const url of networkUrlsForPort(primaryPort, networkHosts)) {
    console.log("[kandev]   network:", url);
  }
  console.log("[kandev] mcp:", `${ports.backendUrl}/mcp`);
  if (dbPath) {
    console.log("[kandev] db:", dbPath);
  }
  if (logLevel) {
    console.log("[kandev] log level:", logLevel);
  }
}

/**
 * Builds `http://<host>:<port>` URLs from a list of host addresses, wrapping
 * IPv6 addresses in brackets per RFC 3986.
 */
export function networkUrlsForPort(port: number, hosts: string[]): string[] {
  return hosts.map((host) => {
    const formatted = host.includes(":") ? `[${host}]` : host;
    return `http://${formatted}:${port}`;
  });
}

/**
 * Attaches a standardized exit handler to a backend process.
 *
 * When the backend exits, this handler logs the exit reason and triggers
 * a graceful shutdown of all supervised processes. If the process was
 * killed by a signal, it exits with code 0; otherwise it uses the
 * process exit code (defaulting to 1).
 *
 * @param backendProc - The backend child process
 * @param supervisor - The process supervisor managing child processes
 */
export function attachBackendExitHandler(
  backendProc: ChildProcess,
  supervisor: ReturnType<typeof createProcessSupervisor>,
  options: { shouldShutdown?: () => boolean } = {},
): void {
  backendProc.on("exit", (code, signal) => {
    console.error(`[kandev] backend exited (code=${code}, signal=${signal})`);
    if (options.shouldShutdown && !options.shouldShutdown()) {
      return;
    }
    const exitCode = signal ? 0 : (code ?? 1);
    void supervisor.shutdown("backend exit").then(() => process.exit(exitCode));
  });
}