import { spawnSync } from 'node:child_process';
import { accessSync, constants } from 'node:fs';
import { join } from 'node:path';

import { resolveBrainHome } from '../fleet/brain-home.js';

/**
 * Shared brain-tool dispatch (fleet CLI integration, Jason ruling
 * 2026-08-28): the npm package embeds the COMMAND SURFACE; operator-owned
 * implementations stay in the brain (tools/). Commands resolve the brain
 * home (MOSAIC_BRAIN_HOME wins — see brain-home.ts) and exec the tool
 * there. Nothing operator-specific ships inside the package.
 *
 * Pass-through contract: arguments, stdout/stderr, and the exit code belong
 * to the tool. The CLI adds nothing on success; absent tools fail loudly
 * with the resolved path (127) instead of guessing.
 */

/** Absolute path of a brain-relative tool. */
export function resolveBrainTool(mosaicHome: string, relPath: string): string {
  return join(resolveBrainHome(mosaicHome), ...relPath.split('/'));
}

/** Map a spawnSync result + tool existence to the CLI exit status. */
export function exitStatusFor(
  result: { status: number | null; error?: NodeJS.ErrnoException },
  toolExists: boolean,
): number {
  if (!toolExists) return 127;
  if (result.status !== null) return result.status;
  return 125; // killed by signal / could not run
}

export function brainToolExists(tool: string): boolean {
  try {
    accessSync(tool, constants.X_OK);
    return true;
  } catch {
    return false;
  }
}

/**
 * Exec a brain tool with full pass-through. `interpreter` runs the tool
 * through e.g. python3 (renderers); omit it for executable scripts.
 * Returns the process exit status; callers assign it to process.exitCode.
 */
export function execBrainTool(
  mosaicHome: string,
  relPath: string,
  args: string[],
  interpreter?: string,
): number {
  const tool = resolveBrainTool(mosaicHome, relPath);
  if (!brainToolExists(tool)) {
    console.error(
      `mosaic: brain tool not found (expected ${tool}). ` +
        'Tool suites live in the brain tree under tools/; ' +
        'check MOSAIC_BRAIN_HOME or the brain checkout.',
    );
    return 127;
  }
  const result = interpreter
    ? spawnSync(interpreter, [tool, ...args], { stdio: 'inherit', env: process.env })
    : spawnSync(tool, args, { stdio: 'inherit', env: process.env });
  return exitStatusFor(result, true);
}