/**
 * @license
 * Copyright 2025 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

import * as fs from 'node:fs/promises';
import * as path from 'node:path';
import stripJsonComments from 'strip-json-comments';
import { GEMINI_DIR } from '../utils/paths.js';
import { debugLogger } from '../utils/debugLogger.js';
import { isNodeError } from '../utils/errors.js';

export interface FolderDiscoveryResults {
  commands: string[];
  mcps: string[];
  hooks: string[];
  skills: string[];
  agents: string[];
  settings: string[];
  securityWarnings: string[];
  discoveryErrors: string[];
}

/**
 * A safe, read-only service to discover local configurations in a folder
 * before it is trusted.
 */
export class FolderTrustDiscoveryService {
  /**
   * Discovers configurations in the given workspace directory.
   * @param workspaceDir The directory to scan.
   * @returns A summary of discovered configurations.
   */
  static async discover(workspaceDir: string): Promise<FolderDiscoveryResults> {
    const results: FolderDiscoveryResults = {
      commands: [],
      mcps: [],
      hooks: [],
      skills: [],
      agents: [],
      settings: [],
      securityWarnings: [],
      discoveryErrors: [],
    };

    const geminiDir = path.join(workspaceDir, GEMINI_DIR);
    if (!(await this.exists(geminiDir))) {
      return results;
    }

    await Promise.all([
      this.discoverCommands(geminiDir, results),
      this.discoverSkills(geminiDir, results),
      this.discoverAgents(geminiDir, results),
      this.discoverSettings(geminiDir, results),
    ]);

    return results;
  }

  private static async discoverCommands(
    geminiDir: string,
    results: FolderDiscoveryResults,
  ) {
    const commandsDir = path.join(geminiDir, 'commands');
    if (await this.exists(commandsDir)) {
      try {
        const files = await fs.readdir(commandsDir, { recursive: true });
        results.commands = files
          .filter((f) => f.endsWith('.toml'))
          .map((f) => path.basename(f, '.toml'));
      } catch (e) {
        results.discoveryErrors.push(
          `Failed to discover commands: ${e instanceof Error ? e.message : String(e)}`,
        );
      }
    }
  }

  private static async discoverSkills(
    geminiDir: string,
    results: FolderDiscoveryResults,
  ) {
    const skillsDir = path.join(geminiDir, 'skills');
    if (await this.exists(skillsDir)) {
      try {
        const entries = await fs.readdir(skillsDir, { withFileTypes: true });
        for (const entry of entries) {
          if (entry.isDirectory()) {
            const skillMdPath = path.join(skillsDir, entry.name, 'SKILL.md');
            if (await this.exists(skillMdPath)) {
              results.skills.push(entry.name);
            }
          }
        }
      } catch (e) {
        results.discoveryErrors.push(
          `Failed to discover skills: ${e instanceof Error ? e.message : String(e)}`,
        );
      }
    }
  }

  private static async discoverAgents(
    geminiDir: string,
    results: FolderDiscoveryResults,
  ) {
    const agentsDir = path.join(geminiDir, 'agents');
    if (await this.exists(agentsDir)) {
      try {
        const entries = await fs.readdir(agentsDir, { withFileTypes: true });
        for (const entry of entries) {
          if (
            entry.isFile() &&
            entry.name.endsWith('.md') &&
            !entry.name.startsWith('_')
          ) {
            results.agents.push(path.basename(entry.name, '.md'));
          }
        }
        if (results.agents.length > 0) {
          results.securityWarnings.push('This project contains custom agents.');
        }
      } catch (e) {
        results.discoveryErrors.push(
          `Failed to discover agents: ${e instanceof Error ? e.message : String(e)}`,
        );
      }
    }
  }

  private static async discoverSettings(
    geminiDir: string,
    results: FolderDiscoveryResults,
  ) {
    const settingsPath = path.join(geminiDir, 'settings.json');
    if (!(await this.exists(settingsPath))) return;

    try {
      const content = await fs.readFile(settingsPath, 'utf-8');
      const settings = JSON.parse(stripJsonComments(content)) as unknown;

      if (!this.isRecord(settings)) {
        debugLogger.debug('Settings must be a JSON object');
        return;
      }

      results.settings = Object.keys(settings).filter(
        (key) => !['mcpServers', 'hooks', '$schema'].includes(key),
      );

      results.securityWarnings.push(...this.collectSecurityWarnings(settings));

      const mcpServers = settings['mcpServers'];
      if (this.isRecord(mcpServers)) {
        results.mcps = Object.keys(mcpServers);
      }

      const hooksConfig = settings['hooks'];
      if (this.isRecord(hooksConfig)) {
        const hooks = new Set<string>();
        for (const event of Object.values(hooksConfig)) {
          if (!Array.isArray(event)) continue;
          for (const hook of event) {
            // eslint-disable-next-line no-restricted-syntax
            if (this.isRecord(hook) && typeof hook['command'] === 'string') {
              hooks.add(hook['command']);
            }
          }
        }
        results.hooks = Array.from(hooks);
      }
    } catch (e) {
      results.discoveryErrors.push(
        `Failed to discover settings: ${e instanceof Error ? e.message : String(e)}`,
      );
    }
  }

  private static collectSecurityWarnings(
    settings: Record<string, unknown>,
  ): string[] {
    const warnings: string[] = [];

    const tools = this.isRecord(settings['tools'])
      ? settings['tools']
      : undefined;

    const security = this.isRecord(settings['security'])
      ? settings['security']
      : undefined;

    const folderTrust =
      security && this.isRecord(security['folderTrust'])
        ? security['folderTrust']
        : undefined;

    const allowedTools = tools?.['allowed'];

    const checks = [
      {
        condition: Array.isArray(allowedTools) && allowedTools.length > 0,
        message: 'This project auto-approves certain tools (tools.allowed).',
      },
      {
        condition: folderTrust?.['enabled'] === false,
        message:
          'This project attempts to disable folder trust (security.folderTrust.enabled).',
      },
      {
        condition: tools?.['sandbox'] === false,
        message: 'This project disables the security sandbox (tools.sandbox).',
      },
    ];

    for (const check of checks) {
      if (check.condition) warnings.push(check.message);
    }

    return warnings;
  }

  private static isRecord(val: unknown): val is Record<string, unknown> {
    return !!val && typeof val === 'object' && !Array.isArray(val);
  }

  private static async exists(filePath: string): Promise<boolean> {
    try {
      await fs.stat(filePath);
      return true;
    } catch (e) {
      if (isNodeError(e) && e.code === 'ENOENT') {
        return false;
      }
      throw e;
    }
  }
}