import fs from 'node:fs/promises';
import os from 'node:os';
import path from 'node:path';

import { SkillsProvider } from '@/modules/providers/shared/skills/skills.provider.js';
import type { ProviderSkillSource } from '@/shared/types.js';

const hasGitMarker = async (dirPath: string): Promise<boolean> => {
  try {
    const gitMarkerStats = await fs.stat(path.join(dirPath, '.git'));
    return gitMarkerStats.isDirectory() || gitMarkerStats.isFile();
  } catch {
    return false;
  }
};

const findTopmostGitRoot = async (startPath: string): Promise<string | null> => {
  let currentPath = path.resolve(startPath);
  let topmostGitRoot: string | null = null;

  while (true) {
    if (await hasGitMarker(currentPath)) {
      topmostGitRoot = currentPath;
    }

    const parentPath = path.dirname(currentPath);
    if (parentPath === currentPath) {
      break;
    }

    currentPath = parentPath;
  }

  return topmostGitRoot;
};

const addUniqueSource = (
  sources: ProviderSkillSource[],
  seenRootDirs: Set<string>,
  source: ProviderSkillSource,
): void => {
  const normalizedRootDir = path.resolve(source.rootDir);
  if (seenRootDirs.has(normalizedRootDir)) {
    return;
  }

  seenRootDirs.add(normalizedRootDir);
  sources.push({ ...source, rootDir: normalizedRootDir });
};

export class CodexSkillsProvider extends SkillsProvider {
  constructor() {
    super('codex');
  }

  protected async getSkillSources(workspacePath: string): Promise<ProviderSkillSource[]> {
    const sources: ProviderSkillSource[] = [];
    const seenRootDirs = new Set<string>();
    const repoRoot = await findTopmostGitRoot(workspacePath);

    addUniqueSource(sources, seenRootDirs, {
      scope: 'repo',
      rootDir: path.join(workspacePath, '.agents', 'skills'),
      commandPrefix: '$',
    });

    if (repoRoot) {
      // Codex checks repository skills at the launch folder, one folder above it,
      // and the topmost git root; these can collapse to the same directory.
      addUniqueSource(sources, seenRootDirs, {
        scope: 'repo',
        rootDir: path.join(path.dirname(workspacePath), '.agents', 'skills'),
        commandPrefix: '$',
      });
      addUniqueSource(sources, seenRootDirs, {
        scope: 'repo',
        rootDir: path.join(repoRoot, '.agents', 'skills'),
        commandPrefix: '$',
      });
    }

    addUniqueSource(sources, seenRootDirs, {
      scope: 'user',
      rootDir: path.join(os.homedir(), '.agents', 'skills'),
      commandPrefix: '$',
    });
    addUniqueSource(sources, seenRootDirs, {
      scope: 'admin',
      rootDir: path.join('/etc', 'codex', 'skills'),
      commandPrefix: '$',
    });
    addUniqueSource(sources, seenRootDirs, {
      scope: 'system',
      rootDir: path.join(os.homedir(), '.codex', 'skills', '.system'),
      commandPrefix: '$',
    });

    return sources;
  }
}