import fs from 'fs';
import path from 'path';

export default class SchemaFileLoader {
  /**
   * Load a schema JSON file and resolve all nested json_dtype references
   *
   * @param {string} filePath - Absolute or relative path to schema file
   * @param {Set<string>} visited - Internal circular reference protection
   * @returns {object} Fully resolved schema JSON
   */
  static load(filePath, visited = new Set()) {
    const absolutePath = path.resolve(filePath);

    if (visited.has(absolutePath)) {
      throw new Error(`Circular schema reference detected: ${absolutePath}`);
    }

    visited.add(absolutePath);

    if (!fs.existsSync(absolutePath)) {
      throw new Error(`Schema file not found: ${absolutePath}`);
    }

    const raw = fs.readFileSync(absolutePath, 'utf-8');
    const schema = JSON.parse(raw);

    const baseDir = path.dirname(absolutePath);
    return this._resolveSchema(schema, baseDir, visited);
  }

  /**
   * Recursively resolve json_dtype references
   */
  static _resolveSchema(schema, baseDir, visited) {
    if (typeof schema !== 'object' || schema === null) return schema;

    for (const field in schema) {
      const rule = schema[field];

      if (!rule || typeof rule !== 'object') continue;

      // Resolve nested JSON object schema
      if (
        rule.type === 'JSONObject' ||
        rule.type === 'JSONArray'
      ) {
        if (typeof rule.json_dtype === 'string') {
          const nestedPath = path.join(baseDir, rule.json_dtype);
          rule.json_dtype = this.load(nestedPath, visited);
        } else if (typeof rule.json_dtype === 'object') {
          rule.json_dtype = this._resolveSchema(
            rule.json_dtype,
            baseDir,
            visited
          );
        }
      }

      // Resolve array of JSON objects
      if (
        rule.type === 'Array' &&
        rule.array_dtype === 'JSONObject'
      ) {
        if (typeof rule.json_dtype === 'string') {
          const nestedPath = path.join(baseDir, rule.json_dtype);
          rule.json_dtype = this.load(nestedPath, visited);
        }
      }
    }

    return schema;
  }
}