/**
 * Text Encoding Service Implementation
 *
 * Provides shared encoder/decoder instances with automatic polyfill fallback
 *
 * @module text-encoding@1.0.0
 */

import type { ITextDecoder, ITextEncoder, ITextEncodingService } from './interfaces';
import { TextDecoderPolyfill } from './TextDecoderPolyfill';
import { TextEncoderPolyfill } from './TextEncoderPolyfill';

export class TextEncodingService implements ITextEncodingService {
  readonly encoder: ITextEncoder;
  readonly decoder: ITextDecoder;

  constructor() {
    // Check for native support and use it if available
    if (this.hasNativeSupport()) {
      // Use native implementations if available
      // @ts-expect-error - TextEncoder might exist globally
      this.encoder =
        typeof TextEncoder !== 'undefined' ? new TextEncoder() : new TextEncoderPolyfill();

      // @ts-expect-error - TextDecoder might exist globally
      this.decoder =
        typeof TextDecoder !== 'undefined' ? new TextDecoder() : new TextDecoderPolyfill();
    } else {
      // Use polyfills
      this.encoder = new TextEncoderPolyfill();
      this.decoder = new TextDecoderPolyfill();
    }
  }

  /**
   * Check if native TextEncoder/TextDecoder are available
   */
  private hasNativeSupport(): boolean {
    // @ts-expect-error - Check global scope
    return typeof TextEncoder !== 'undefined' && typeof TextDecoder !== 'undefined';
  }

  /**
   * Encode string to UTF-8 bytes
   */
  encode(text: string): Uint8Array {
    return this.encoder.encode(text);
  }

  /**
   * Decode bytes to string
   */
  decode(bytes: Uint8Array | ArrayBuffer | number[]): string {
    if (Array.isArray(bytes)) {
      // Convert number array to Uint8Array
      return this.decoder.decode(new Uint8Array(bytes));
    }
    return this.decoder.decode(bytes as Uint8Array | ArrayBuffer);
  }

  /**
   * Convenience method: string to UTF-8
   */
  stringToUtf8(text: string): Uint8Array {
    return this.encode(text);
  }

  /**
   * Convenience method: UTF-8 to string
   */
  utf8ToString(bytes: Uint8Array | number[]): string {
    return this.decode(bytes);
  }
}

/**
 * Singleton instance for shared use
 */
let serviceInstance: TextEncodingService | null = null;

/**
 * Get or create the singleton service instance
 */
export function getTextEncodingService(): ITextEncodingService {
  if (!serviceInstance) {
    serviceInstance = new TextEncodingService();
  }
  return serviceInstance;
}