/**
 * Install flow — fetch a curated skill's published files from the
 * skillet-skills repo and write them into pi's skills directory.
 * Trusted-surface (CLI) only; the engine never imports this.
 */
import { rmSync } from 'node:fs';
import { join } from 'node:path';
import type { GalleryEntry, SkillFile } from '../types.js';
import { createSkillWriter } from '../skill-writer.js';

const REPO_RAW_BASE =
  'https://raw.githubusercontent.com/dev-resolute/skillet-skills/main';

export class SkillNotFoundError extends Error {
  constructor(public skillName: string) {
    super(`Skill "${skillName}" not found in the gallery.`);
    this.name = 'SkillNotFoundError';
  }
}

export interface FetchedSkill {
  entry: GalleryEntry;
  files: SkillFile[];
}

export async function fetchSkill(name: string): Promise<FetchedSkill> {
  const url = `${REPO_RAW_BASE}/${name}/.skillet/gallery-entry.json`;
  const res = await fetch(url);

  if (res.status === 404) {
    throw new SkillNotFoundError(name);
  }
  if (!res.ok) {
    throw new Error(`failed to fetch skill "${name}": ${res.status}`);
  }

  const entry = (await res.json()) as GalleryEntry;
  if (
    !Array.isArray(entry.files) ||
    entry.files.length === 0 ||
    !Array.isArray(entry.operations)
  ) {
    throw new Error(`gallery entry for "${name}" is malformed`);
  }
  return { entry, files: entry.files };
}

export interface InstallResult {
  apiName: string;
  installedPath: string;
  verifiedCount: number;
}

export async function installSkill(name: string, destDir: string): Promise<InstallResult> {
  const { entry, files } = await fetchSkill(name);
  const installedPath = join(destDir, name);

  rmSync(installedPath, { recursive: true, force: true });

  const writeResult = await createSkillWriter().write(files, installedPath);
  if (!writeResult.success) {
    throw new Error(`failed to write skill "${name}": ${writeResult.errors.join('; ')}`);
  }

  const verifiedCount = entry.operations.filter((op) => op.verification === 'passed').length;
  return { apiName: entry.apiName, installedPath, verifiedCount };
}