import * as fs from 'fs-extra';

import { IEnvironment } from './environment';

/**
 * Configuration object
 */
export class Configuration {
  public config: any = {};
  public loaded = false;

  constructor(
    private env: IEnvironment,
    private file: string,
    private defaults: any = {}
  ) {}

  /**
   * Load the configuration from its file.
   */
  public async load(): Promise<void> {
    this.loaded = true;
    if (!await fs.pathExists(this.file)) {
      this.saveDefaults();
      return;
    }

    const json = await fs.readJson(this.file);
    this.config = json;

    // Assign default values to existing configuration and resave.
    // Eliminates the need for plugins to overwrite the configuration file
    // when exiting.
    if (this.defaults) {
      this.config = Object.assign({}, this.defaults, json);
      await this.save();
    }
  }

  /**
   * Save configuration to its file.
   */
  public async save(): Promise<void> {
    return fs.writeJson(this.file, this.config);
  }

  /**
   * Get a configuration value by key.
   * @param key JSON traverse key (foo.bar.one)
   * @param defval Default value
   * @param from Internal use only
   * @returns Configuration value or default or null
   */
  public get(key: string, defval?: any, from?: any): any {
    if (!from) {
      from = this.config;
    }

    // Recursive object traversal
    if (key.indexOf('.') !== -1) {
      const split = key.split('.');
      const first = this.get(split[0], null, from);
      if (first != null) {
        return this.get(split.slice(1).join('.'), defval, first);
      }
      return defval;
    }

    // Array indexing
    if (key.indexOf('[') !== -1 && key.indexOf(']') !== -1) {
      const match = key.match(/\[(\d+)\]/i);
      const realKey = key.substr(0, key.indexOf('['));
      if (match != null) {
        const index = parseInt(match[1], 10);
        if (from[realKey]) {
          return from[realKey][index];
        }
      }
      return defval;
    }

    if (from[key] == null) {
      return defval;
    }

    return from[key];
  }

  /**
   * Set a configuration value by key.
   * @returns true on success
   */
  public set(key: string, value?: any, from?: any): boolean {
    if (!from) {
      from = this.config;
    }

    // Recursive object traversal
    if (key.indexOf('.') !== -1) {
      const split = key.split('.');
      const first = this.get(split[0], null, from);
      if (first != null) {
        return this.set(split.slice(1).join('.'), value, first);
      }
      return false;
    }

    // Array indexing
    if (key.indexOf('[') !== -1 && key.indexOf(']') !== -1) {
      const match = key.match(/\[(\d+)\]/i);
      const realKey = key.substr(0, key.indexOf('['));
      if (match != null) {
        const index = parseInt(match[1], 10);
        if (from[realKey]) {
          from[realKey][index] = value;
        }
      }
      return false;
    }

    from[key] = value;
    return true;
  }

  /**
   * Set the default configuration before loading.
   * @param defconf Default configuration
   */
  public setDefaults(defconf: any): void {
    this.defaults = defconf;
  }

  /**
   * Save default values to configuration file
   */
  public async saveDefaults(): Promise<void> {
    this.config = this.defaults || {};
    await this.save();
  }
}