/*
 * Copyright (c) 2025 Huawei Device Co., Ltd.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { int32 } from './InteropTypes';

interface SystemTextEncoder {
  encode(input?: string): Uint8Array;
  encodeInto(src: string, dest: Uint8Array): void;
}

interface WithStreamOption {
  stream?: boolean | undefined;
}

interface SystemTextDecoder {
  decode(input?: ArrayBuffer | null | Uint8Array, options?: WithStreamOption): string;
}

export class CustomTextEncoder {
  static readonly HeaderLen: int32 = Int32Array.BYTES_PER_ELEMENT;

  constructor(
    encoder: SystemTextEncoder | undefined = typeof TextEncoder !== 'undefined' ? new TextEncoder() : undefined
  ) {
    this.encoder = encoder;
  }

  private readonly encoder: SystemTextEncoder | undefined;

  public static stringLength(input: string): int32 {
    let length = 0;
    for (let i = 0; i < input.length; i++) {
      length++;
      let cp = input.codePointAt(i)!;
      if (cp >= 0x10000) {
        i++;
      }
    }
    return length;
  }

  encodedLength(input: string): int32 {
    let length = 0;
    for (let i = 0; i < input.length; i++) {
      let cp = input.codePointAt(i)!;
      if (cp < 0x80) {
        length += 1;
      } else if (cp < 0x800) {
        length += 2;
      } else if (cp < 0x10000) {
        length += 3;
      } else {
        length += 4;
        i++;
      }
    }
    return length;
  }

  private addLength(array: Uint8Array, offset: int32, len: int32): void {
    array[offset] = len & 0xff;
    array[offset + 1] = (len >> 8) & 0xff;
    array[offset + 2] = (len >> 16) & 0xff;
    array[offset + 3] = (len >> 24) & 0xff;
  }

  static getHeaderLength(array: Uint8Array, offset: int32 = 0): int32 {
    return array[offset] | (array[offset + 1] << 8) | (array[offset + 2] << 16) | (array[offset + 3] << 24);
  }

  // Produces array of bytes with encoded string headed by 4 bytes (little endian) size information:
  // [s0][s1][s2][s3] [c_0] ... [c_size-1]
  encode(input: string | undefined, addLength: boolean = true): Uint8Array {
    let headerLen = addLength ? CustomTextEncoder.HeaderLen : 0;
    let result: Uint8Array;
    if (!input) {
      result = new Uint8Array(headerLen);
    } else if (this.encoder !== undefined) {
      result = this.encoder!.encode('s'.repeat(headerLen) + input);
    } else {
      let length = this.encodedLength(input);
      result = new Uint8Array(length + headerLen);
      this.encodeInto(input, result, headerLen);
    }
    if (addLength) {
      this.addLength(result, 0, result.length - headerLen);
    }
    return result;
  }

  // Produces encoded array of strings with size information.
  encodeArray(strings: Array<string>): Uint8Array {
    let totalBytes = CustomTextEncoder.HeaderLen;
    let lengths = new Int32Array(strings.length);
    for (let i = 0; i < lengths.length; i++) {
      let len = this.encodedLength(strings[i]);
      lengths[i] = len;
      totalBytes += len + CustomTextEncoder.HeaderLen;
    }
    let array = new Uint8Array(totalBytes);
    let position = 0;
    this.addLength(array, position, lengths.length);
    position += CustomTextEncoder.HeaderLen;
    for (let i = 0; i < lengths.length; i++) {
      this.addLength(array, position, lengths[i]);
      position += CustomTextEncoder.HeaderLen;
      this.encodeInto(strings[i], array, position);
      position += lengths[i];
    }
    return array;
  }

  encodeInto(input: string, result: Uint8Array, position: int32): Uint8Array {
    if (this.encoder !== undefined) {
      this.encoder!.encodeInto(input, result.subarray(position, result.length));
      return result;
    }
    let index = position;
    for (let stringPosition = 0; stringPosition < input.length; stringPosition++) {
      let cp = input.codePointAt(stringPosition)!;
      if (cp < 0x80) {
        result[index++] = cp | 0;
      } else if (cp < 0x800) {
        result[index++] = (cp >> 6) | 0xc0;
        result[index++] = (cp & 0x3f) | 0x80;
      } else if (cp < 0x10000) {
        result[index++] = (cp >> 12) | 0xe0;
        result[index++] = ((cp >> 6) & 0x3f) | 0x80;
        result[index++] = (cp & 0x3f) | 0x80;
      } else {
        result[index++] = (cp >> 18) | 0xf0;
        result[index++] = ((cp >> 12) & 0x3f) | 0x80;
        result[index++] = ((cp >> 6) & 0x3f) | 0x80;
        result[index++] = (cp & 0x3f) | 0x80;
        stringPosition++;
      }
    }
    result[index] = 0;
    return result;
  }
}

export class CustomTextDecoder {
  static cpArrayMaxSize = 128;
  constructor(
    decoder: SystemTextDecoder | TextDecoder | undefined = typeof TextDecoder !== 'undefined'
      ? new TextDecoder()
      : undefined
  ) {
    this.decoder = decoder;
  }

  private readonly decoder: SystemTextDecoder | TextDecoder | undefined;

  decode(input: Uint8Array): string {
    if (this.decoder !== undefined) {
      return this.decoder!.decode(input);
    }
    const cpSize = Math.min(CustomTextDecoder.cpArrayMaxSize, input.length);
    let codePoints = new Int32Array(cpSize);
    let cpIndex = 0;
    let index = 0;
    let result = '';
    while (index < input.length) {
      let elem = input[index];
      let lead = elem & 0xff;
      let count = 0;
      let value = 0;
      if (lead < 0x80) {
        count = 1;
        value = elem;
      } else if (lead >> 5 === 0x6) {
        value = ((elem << 6) & 0x7ff) + (input[index + 1] & 0x3f);
        count = 2;
      } else if (lead >> 4 === 0xe) {
        value = ((elem << 12) & 0xffff) + ((input[index + 1] << 6) & 0xfff) + (input[index + 2] & 0x3f);
        count = 3;
      } else if (lead >> 3 === 0x1e) {
        value =
          ((elem << 18) & 0x1fffff) +
          ((input[index + 1] << 12) & 0x3ffff) +
          ((input[index + 2] << 6) & 0xfff) +
          (input[index + 3] & 0x3f);
        count = 4;
      }
      codePoints[cpIndex++] = value;
      if (cpIndex === cpSize) {
        cpIndex = 0;
        result += String.fromCodePoint(...codePoints);
      }
      index += count;
    }
    if (cpIndex > 0) {
      result += String.fromCodePoint(...codePoints.slice(0, cpIndex));
    }
    return result;
  }
}