import { existsSync } from 'node:fs';
import { createRequire } from 'node:module';
import { dirname, join, resolve } from 'node:path';
import { fileURLToPath } from 'node:url';

/** Installed application resources and writable project data have different roots. */
export const APPLICATION_ROOT = fileURLToPath(new URL('../../', import.meta.url));

export function resolveVeoRuntime(options: {
  env?: NodeJS.ProcessEnv;
  workspaceRoot?: string;
  flowEntry?: string;
  applicationRoot?: string;
} = {}): { cliRoot: string; flowEntry: string } {
  const env = options.env ?? process.env;
  const explicitEntry = options.flowEntry?.trim() || env.VCLAW_VEO_FLOW_ENTRY?.trim();
  if (explicitEntry) {
    const flowEntry = resolve(explicitEntry);
    return { cliRoot: dirname(flowEntry), flowEntry };
  }
  const explicitRoot = env.VCLAW_VEO_CLI_ROOT?.trim();
  // Project storage is data, never an implicit source of executable code.
  // Legacy sidecars remain supported through an explicit root/entry override.
  const cliRoot = resolve(explicitRoot || join(options.applicationRoot ?? APPLICATION_ROOT, 'vclaw-cli'));
  return { cliRoot, flowEntry: join(cliRoot, 'flow.ts') };
}

/** Offline prerequisite check: this does not authenticate or contact a provider. */
export function veoRuntimeIssues(runtime: { cliRoot: string; flowEntry: string }): string[] {
  if (!existsSync(runtime.flowEntry)) {
    return [`Veo runtime could not find flow.ts at ${runtime.flowEntry}. Set VCLAW_VEO_CLI_ROOT to a bootstrapped vclaw-cli directory.`];
  }
  const require = createRequire(runtime.flowEntry);
  const missing = ['ora', 'image-size', 'puppeteer-real-browser'].filter((name) => {
    try { require.resolve(name); return false; } catch { return true; }
  });
  return missing.length ? [
    `Missing Veo sidecar dependencies: ${missing.join(', ')}. Run bun install --frozen-lockfile in ${runtime.cliRoot}. `
      + 'If the installed package is read-only, copy its vclaw-cli directory to a writable location, install there, and set VCLAW_VEO_CLI_ROOT to that directory.',
  ] : [];
}