/**
 * Shared config for browse CLI + server.
 *
 * Resolution:
 *   1. BROWSE_STATE_FILE env → derive stateDir from parent
 *   2. git rev-parse --show-toplevel → projectDir/.gstack/
 *   3. process.cwd() fallback (non-git environments)
 *
 * The CLI computes the config and passes BROWSE_STATE_FILE to the
 * spawned server. The server derives all paths from that env var.
 */

import * as fs from 'fs';
import * as path from 'path';

export interface BrowseConfig {
  projectDir: string;
  stateDir: string;
  stateFile: string;
  consoleLog: string;
  networkLog: string;
  dialogLog: string;
}

/**
 * Detect the git repository root, or null if not in a repo / git unavailable.
 */
export function getGitRoot(): string | null {
  try {
    const proc = Bun.spawnSync(['git', 'rev-parse', '--show-toplevel'], {
      stdout: 'pipe',
      stderr: 'pipe',
      timeout: 2_000, // Don't hang if .git is broken
    });
    if (proc.exitCode !== 0) return null;
    return proc.stdout.toString().trim() || null;
  } catch {
    return null;
  }
}

/**
 * Resolve all browse config paths.
 *
 * If BROWSE_STATE_FILE is set (e.g. by CLI when spawning server, or by
 * tests for isolation), all paths are derived from it. Otherwise, the
 * project root is detected via git or cwd.
 */
export function resolveConfig(
  env: Record<string, string | undefined> = process.env,
): BrowseConfig {
  let stateFile: string;
  let stateDir: string;
  let projectDir: string;

  if (env.BROWSE_STATE_FILE) {
    stateFile = env.BROWSE_STATE_FILE;
    stateDir = path.dirname(stateFile);
    projectDir = path.dirname(stateDir); // parent of .gstack/
  } else {
    projectDir = getGitRoot() || process.cwd();
    stateDir = path.join(projectDir, '.gstack');
    stateFile = path.join(stateDir, 'browse.json');
  }

  return {
    projectDir,
    stateDir,
    stateFile,
    consoleLog: path.join(stateDir, 'browse-console.log'),
    networkLog: path.join(stateDir, 'browse-network.log'),
    dialogLog: path.join(stateDir, 'browse-dialog.log'),
  };
}

/**
 * Create the .gstack/ state directory if it doesn't exist.
 * Throws with a clear message on permission errors.
 */
export function ensureStateDir(config: BrowseConfig): void {
  try {
    fs.mkdirSync(config.stateDir, { recursive: true });
  } catch (err: any) {
    if (err.code === 'EACCES') {
      throw new Error(`Cannot create state directory ${config.stateDir}: permission denied`);
    }
    if (err.code === 'ENOTDIR') {
      throw new Error(`Cannot create state directory ${config.stateDir}: a file exists at that path`);
    }
    throw err;
  }
}

/**
 * Read the binary version (git SHA) from browse/dist/.version.
 * Returns null if the file doesn't exist or can't be read.
 */
export function readVersionHash(execPath: string = process.execPath): string | null {
  try {
    const versionFile = path.resolve(path.dirname(execPath), '.version');
    return fs.readFileSync(versionFile, 'utf-8').trim() || null;
  } catch {
    return null;
  }
}