import { readdir, readFile } from 'node:fs/promises';
import { basename, dirname, join } from 'node:path';
import type { OpencodeSkillInfo } from './client';

const SKILL_ROOT_NAMES = ['skill', 'skills'] as const;

async function collectSkillFiles(root: string): Promise<string[]> {
  let entries;
  try {
    entries = await readdir(root, { withFileTypes: true });
  } catch (error) {
    if (typeof error === 'object' && error && 'code' in error && error.code === 'ENOENT') {
      return [];
    }
    throw error;
  }

  const files: string[] = [];
  for (const entry of entries) {
    const entryPath = join(root, entry.name);
    if (entry.isFile() && entry.name === 'SKILL.md') {
      files.push(entryPath);
      continue;
    }
    if (entry.isDirectory()) {
      files.push(...await collectSkillFiles(entryPath));
    }
  }
  return files;
}

function unquoteYamlScalar(value: string): string {
  const trimmed = value.trim();
  if (
    (trimmed.startsWith('"') && trimmed.endsWith('"'))
    || (trimmed.startsWith("'") && trimmed.endsWith("'"))
  ) {
    return trimmed.slice(1, -1).trim();
  }
  return trimmed;
}

function readFrontmatterScalar(content: string, key: string): string | undefined {
  const match = content.match(/^---\s*\r?\n([\s\S]*?)\r?\n---(?:\r?\n|$)/);
  if (!match) return undefined;
  const keyPattern = new RegExp(`^${key}:\\s*(.*)$`);
  for (const line of match[1].split(/\r?\n/)) {
    const scalar = line.match(keyPattern);
    if (!scalar) continue;
    const value = unquoteYamlScalar(scalar[1] ?? '');
    return value || undefined;
  }
  return undefined;
}

export async function listInstalledOpencodeSkills(managedConfigDir?: string | null): Promise<OpencodeSkillInfo[]> {
  const configDir = managedConfigDir?.trim();
  if (!configDir) return [];

  const skillFiles = (
    await Promise.all(SKILL_ROOT_NAMES.map((rootName) => collectSkillFiles(join(configDir, rootName))))
  ).flat().sort((left, right) => left.localeCompare(right));

  const seen = new Set<string>();
  const skills: OpencodeSkillInfo[] = [];
  for (const location of skillFiles) {
    const content = await readFile(location, 'utf8');
    const name = readFrontmatterScalar(content, 'name') ?? basename(dirname(location));
    if (!name || seen.has(name)) continue;
    seen.add(name);
    skills.push({
      name,
      description: readFrontmatterScalar(content, 'description'),
      location,
      content,
    });
  }

  return skills;
}