import { Inject, Injectable, Optional } from '@nestjs/common';

import { InvalidAppConfig } from '../error';
import { APP_CONFIG_DESCRIPTORS, getDefaultConfig, override } from './register';

export const OVERRIDE_CONFIG_TOKEN = Symbol('OVERRIDE_CONFIG_TOKEN');

@Injectable()
export class ConfigFactory {
  readonly #original: AppConfig;
  readonly #config: AppConfig;
  get config() {
    return this.#config;
  }

  constructor(
    @Inject(OVERRIDE_CONFIG_TOKEN)
    @Optional()
    private readonly overrides: DeepPartial<AppConfig> = {}
  ) {
    this.#original = this.loadDefault();
    this.#config = structuredClone(this.#original);
  }

  clone() {
    // we did not freeze the #config object, it might be modified
    return structuredClone(this.#original);
  }

  override(updates: DeepPartial<AppConfig>) {
    override(this.#original, updates);
    override(this.#config, updates);
  }

  validate(updates: Array<{ module: string; key: string; value: any }>) {
    const errors: InvalidAppConfig[] = [];

    updates.forEach(update => {
      const descriptor = APP_CONFIG_DESCRIPTORS[update.module]?.[update.key];
      if (!descriptor) {
        errors.push(
          new InvalidAppConfig({
            module: update.module,
            key: update.key,
            hint: `Unknown config [${update.key}]`,
          })
        );
        return;
      }

      const { success, error } = descriptor.validate(update.value);
      if (!success) {
        error.issues.forEach(issue => {
          errors.push(
            new InvalidAppConfig({
              module: update.module,
              key: update.key,
              hint: issue.message,
            })
          );
        });
      }
    });

    return errors.length > 0 ? errors : null;
  }

  private loadDefault() {
    const config = getDefaultConfig();
    override(config, this.overrides);
    return config;
  }
}