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import { prettyByte } from "./utils/prettyByte.ts";import { ExtensionCodec, ExtensionCodecType } from "./ExtensionCodec.ts";import { getInt64, getUint64 } from "./utils/int.ts";import {  TEXT_DECODER_THRESHOLD,  utf8DecodeJs,  utf8DecodeTD,} from "./utils/utf8.ts";import { createDataView, ensureUint8Array } from "./utils/typedArrays.ts";import { CachedKeyDecoder, KeyDecoder } from "./CachedKeyDecoder.ts";
const enum State {  ARRAY,  MAP_KEY,  MAP_VALUE,}
type MapKeyType = string | number;
const isValidMapKeyType = (key: unknown): key is MapKeyType => {  const keyType = typeof key;
  return keyType === "string" || keyType === "number";};
type StackMapState = {  type: State.MAP_KEY | State.MAP_VALUE;  size: number;  key: MapKeyType | null;  readCount: number;  map: Record<string, unknown>;};
type StackArrayState = {  type: State.ARRAY;  size: number;  array: Array<unknown>;  position: number;};
type StackState = StackArrayState | StackMapState;
const HEAD_BYTE_REQUIRED = -1;
const EMPTY_VIEW = new DataView(new ArrayBuffer(0));const EMPTY_BYTES = new Uint8Array(EMPTY_VIEW.buffer);
// IE11: Hack to support IE11.// IE11: Drop this hack and just use RangeError when IE11 is obsolete.export const DataViewIndexOutOfBoundsError: typeof Error = (() => {  try {    // IE11: The spec says it should throw RangeError,    // IE11: but in IE11 it throws TypeError.    EMPTY_VIEW.getInt8(0);  } catch (e) {    return e.constructor;  }  throw new Error("never reached");})();
const MORE_DATA = new DataViewIndexOutOfBoundsError("Insufficient data");
const DEFAULT_MAX_LENGTH = 0xffff_ffff; // uint32_max
const sharedCachedKeyDecoder = new CachedKeyDecoder();
export class Decoder<ContextType> {  private totalPos = 0;  private pos = 0;
  private view = EMPTY_VIEW;  private bytes = EMPTY_BYTES;  private headByte = HEAD_BYTE_REQUIRED;  private readonly stack: Array<StackState> = [];
  public constructor(    private readonly extensionCodec: ExtensionCodecType<ContextType> =      // deno-lint-ignore no-explicit-any      ExtensionCodec.defaultCodec as any,    // deno-lint-ignore no-explicit-any    private readonly context: ContextType = undefined as any,    private readonly maxStrLength = DEFAULT_MAX_LENGTH,    private readonly maxBinLength = DEFAULT_MAX_LENGTH,    private readonly maxArrayLength = DEFAULT_MAX_LENGTH,    private readonly maxMapLength = DEFAULT_MAX_LENGTH,    private readonly maxExtLength = DEFAULT_MAX_LENGTH,    private readonly keyDecoder: KeyDecoder | null = sharedCachedKeyDecoder,  ) {}
  private reinitializeState() {    this.totalPos = 0;    this.headByte = HEAD_BYTE_REQUIRED;  }
  private setBuffer(    buffer: ArrayLike<number> | ArrayBuffer | BufferSource,  ): void {    this.bytes = ensureUint8Array(buffer);    this.view = createDataView(this.bytes);    this.pos = 0;  }
  private appendBuffer(buffer: ArrayLike<number> | BufferSource) {    // Create a fresh copy of `buffer` while caller might re-use and    // modify the content of the `buffer`.    // This cause data pollution issue like #2.    buffer = ensureUint8Array(buffer).slice();    if (this.headByte === HEAD_BYTE_REQUIRED && !this.hasRemaining()) {      this.setBuffer(buffer);    } else {      // retried because data is insufficient      const remainingData = this.bytes.subarray(this.pos);      const newData = ensureUint8Array(buffer);      const concated = new Uint8Array(remainingData.length + newData.length);      concated.set(remainingData);      concated.set(newData, remainingData.length);      this.setBuffer(concated);    }  }
  private hasRemaining(size = 1) {    return this.view.byteLength - this.pos >= size;  }
  private createNoExtraBytesError(posToShow: number): Error {    const { view, pos } = this;    return new RangeError(      `Extra ${view.byteLength -        pos} of ${view.byteLength} byte(s) found at buffer[${posToShow}]`,    );  }
  public decode(buffer: ArrayLike<number> | ArrayBuffer): unknown {    this.reinitializeState();    this.setBuffer(buffer);    return this.doDecodeSingleSync();  }
  private doDecodeSingleSync(): unknown {    const object = this.doDecodeSync();    if (this.hasRemaining()) {      throw this.createNoExtraBytesError(this.pos);    }    return object;  }
  public async decodeAsync(    stream: AsyncIterable<ArrayLike<number> | BufferSource>,  ): Promise<unknown> {    let decoded = false;    let object: unknown;    for await (const buffer of stream) {      if (decoded) {        throw this.createNoExtraBytesError(this.totalPos);      }
      this.appendBuffer(buffer);
      try {        object = this.doDecodeSync();        decoded = true;      } catch (e) {        if (!(e instanceof DataViewIndexOutOfBoundsError)) {          throw e; // rethrow        }        // fallthrough      }      this.totalPos += this.pos;    }
    if (decoded) {      if (this.hasRemaining()) {        throw this.createNoExtraBytesError(this.totalPos);      }      return object;    }
    const { headByte, pos, totalPos } = this;    throw new RangeError(      `Insufficient data in parcing ${        prettyByte(headByte)      } at ${totalPos} (${pos} in the current buffer)`,    );  }
  public decodeArrayStream(stream: AsyncIterable<ArrayLike<number>>) {    return this.decodeMultiAsync(stream, true);  }
  public decodeStream(stream: AsyncIterable<ArrayLike<number>>) {    return this.decodeMultiAsync(stream, false);  }
  private async *decodeMultiAsync(    stream: AsyncIterable<ArrayLike<number>>,    isArray: boolean,  ) {    let isArrayHeaderRequired = isArray;    let arrayItemsLeft = -1;
    for await (const buffer of stream) {      if (isArray && arrayItemsLeft === 0) {        throw this.createNoExtraBytesError(this.totalPos);      }
      this.appendBuffer(buffer);
      if (isArrayHeaderRequired) {        arrayItemsLeft = this.readArraySize();        isArrayHeaderRequired = false;        this.complete();      }
      try {        while (true) {          yield this.doDecodeSync();          if (--arrayItemsLeft === 0) {            break;          }        }      } catch (e) {        if (!(e instanceof DataViewIndexOutOfBoundsError)) {          throw e; // rethrow        }        // fallthrough      }      this.totalPos += this.pos;    }  }
  private doDecodeSync(): unknown {    DECODE:    while (true) {      const headByte = this.readHeadByte();      let object: unknown;
      if (headByte >= 0xe0) {        // negative fixint (111x xxxx) 0xe0 - 0xff        object = headByte - 0x100;      } else if (headByte < 0xc0) {        if (headByte < 0x80) {          // positive fixint (0xxx xxxx) 0x00 - 0x7f          object = headByte;        } else if (headByte < 0x90) {          // fixmap (1000 xxxx) 0x80 - 0x8f          const size = headByte - 0x80;          if (size !== 0) {            this.pushMapState(size);            this.complete();            continue DECODE;          } else {            object = {};          }        } else if (headByte < 0xa0) {          // fixarray (1001 xxxx) 0x90 - 0x9f          const size = headByte - 0x90;          if (size !== 0) {            this.pushArrayState(size);            this.complete();            continue DECODE;          } else {            object = [];          }        } else {          // fixstr (101x xxxx) 0xa0 - 0xbf          const byteLength = headByte - 0xa0;          object = this.decodeUtf8String(byteLength, 0);        }      } else if (headByte === 0xc0) {        // nil        object = null;      } else if (headByte === 0xc2) {        // false        object = false;      } else if (headByte === 0xc3) {        // true        object = true;      } else if (headByte === 0xca) {        // float 32        object = this.readF32();      } else if (headByte === 0xcb) {        // float 64        object = this.readF64();      } else if (headByte === 0xcc) {        // uint 8        object = this.readU8();      } else if (headByte === 0xcd) {        // uint 16        object = this.readU16();      } else if (headByte === 0xce) {        // uint 32        object = this.readU32();      } else if (headByte === 0xcf) {        // uint 64        object = this.readU64();      } else if (headByte === 0xd0) {        // int 8        object = this.readI8();      } else if (headByte === 0xd1) {        // int 16        object = this.readI16();      } else if (headByte === 0xd2) {        // int 32        object = this.readI32();      } else if (headByte === 0xd3) {        // int 64        object = this.readI64();      } else if (headByte === 0xd9) {        // str 8        const byteLength = this.lookU8();        object = this.decodeUtf8String(byteLength, 1);      } else if (headByte === 0xda) {        // str 16        const byteLength = this.lookU16();        object = this.decodeUtf8String(byteLength, 2);      } else if (headByte === 0xdb) {        // str 32        const byteLength = this.lookU32();        object = this.decodeUtf8String(byteLength, 4);      } else if (headByte === 0xdc) {        // array 16        const size = this.readU16();        if (size !== 0) {          this.pushArrayState(size);          this.complete();          continue DECODE;        } else {          object = [];        }      } else if (headByte === 0xdd) {        // array 32        const size = this.readU32();        if (size !== 0) {          this.pushArrayState(size);          this.complete();          continue DECODE;        } else {          object = [];        }      } else if (headByte === 0xde) {        // map 16        const size = this.readU16();        if (size !== 0) {          this.pushMapState(size);          this.complete();          continue DECODE;        } else {          object = {};        }      } else if (headByte === 0xdf) {        // map 32        const size = this.readU32();        if (size !== 0) {          this.pushMapState(size);          this.complete();          continue DECODE;        } else {          object = {};        }      } else if (headByte === 0xc4) {        // bin 8        const size = this.lookU8();        object = this.decodeBinary(size, 1);      } else if (headByte === 0xc5) {        // bin 16        const size = this.lookU16();        object = this.decodeBinary(size, 2);      } else if (headByte === 0xc6) {        // bin 32        const size = this.lookU32();        object = this.decodeBinary(size, 4);      } else if (headByte === 0xd4) {        // fixext 1        object = this.decodeExtension(1, 0);      } else if (headByte === 0xd5) {        // fixext 2        object = this.decodeExtension(2, 0);      } else if (headByte === 0xd6) {        // fixext 4        object = this.decodeExtension(4, 0);      } else if (headByte === 0xd7) {        // fixext 8        object = this.decodeExtension(8, 0);      } else if (headByte === 0xd8) {        // fixext 16        object = this.decodeExtension(16, 0);      } else if (headByte === 0xc7) {        // ext 8        const size = this.lookU8();        object = this.decodeExtension(size, 1);      } else if (headByte === 0xc8) {        // ext 16        const size = this.lookU16();        object = this.decodeExtension(size, 2);      } else if (headByte === 0xc9) {        // ext 32        const size = this.lookU32();        object = this.decodeExtension(size, 4);      } else {        throw new Error(`Unrecognized type byte: ${prettyByte(headByte)}`);      }
      this.complete();
      const stack = this.stack;      while (stack.length > 0) {        // arrays and maps        const state = stack[stack.length - 1];        if (state.type === State.ARRAY) {          state.array[state.position] = object;          state.position++;          if (state.position === state.size) {            stack.pop();            object = state.array;          } else {            continue DECODE;          }        } else if (state.type === State.MAP_KEY) {          if (!isValidMapKeyType(object)) {            throw new Error(              "The type of key must be string or number but " + typeof object,            );          }
          state.key = object;          state.type = State.MAP_VALUE;          continue DECODE;        } else {          // it must be `state.type === State.MAP_VALUE` here
          // eslint-disable-next-line @typescript-eslint/no-non-null-assertion          state.map[state.key!] = object;          state.readCount++;
          if (state.readCount === state.size) {            stack.pop();            object = state.map;          } else {            state.key = null;            state.type = State.MAP_KEY;            continue DECODE;          }        }      }
      return object;    }  }
  private readHeadByte(): number {    if (this.headByte === HEAD_BYTE_REQUIRED) {      this.headByte = this.readU8();      // console.log("headByte", prettyByte(this.headByte));    }
    return this.headByte;  }
  private complete(): void {    this.headByte = HEAD_BYTE_REQUIRED;  }
  private readArraySize(): number {    const headByte = this.readHeadByte();
    switch (headByte) {      case 0xdc:        return this.readU16();      case 0xdd:        return this.readU32();      default: {        if (headByte < 0xa0) {          return headByte - 0x90;        } else {          throw new Error(            `Unrecognized array type byte: ${prettyByte(headByte)}`,          );        }      }    }  }
  private pushMapState(size: number) {    if (size > this.maxMapLength) {      throw new Error(        `Max length exceeded: map length (${size}) > maxMapLengthLength (${this.maxMapLength})`,      );    }
    this.stack.push({      type: State.MAP_KEY,      size,      key: null,      readCount: 0,      map: {},    });  }
  private pushArrayState(size: number) {    if (size > this.maxArrayLength) {      throw new Error(        `Max length exceeded: array length (${size}) > maxArrayLength (${this.maxArrayLength})`,      );    }
    this.stack.push({      type: State.ARRAY,      size,      array: new Array<unknown>(size),      position: 0,    });  }
  private decodeUtf8String(byteLength: number, headerOffset: number): string {    if (byteLength > this.maxStrLength) {      throw new Error(        `Max length exceeded: UTF-8 byte length (${byteLength}) > maxStrLength (${this.maxStrLength})`,      );    }
    if (this.bytes.byteLength < this.pos + headerOffset + byteLength) {      throw MORE_DATA;    }
    const offset = this.pos + headerOffset;    let object: string;    if (this.stateIsMapKey() && this.keyDecoder?.canBeCached(byteLength)) {      object = this.keyDecoder.decode(this.bytes, offset, byteLength);    } else if (byteLength > TEXT_DECODER_THRESHOLD) {      object = utf8DecodeTD(this.bytes, offset, byteLength);    } else {      object = utf8DecodeJs(this.bytes, offset, byteLength);    }    this.pos += headerOffset + byteLength;    return object;  }
  private stateIsMapKey(): boolean {    if (this.stack.length > 0) {      const state = this.stack[this.stack.length - 1];      return state.type === State.MAP_KEY;    }    return false;  }
  private decodeBinary(byteLength: number, headOffset: number): Uint8Array {    if (byteLength > this.maxBinLength) {      throw new Error(        `Max length exceeded: bin length (${byteLength}) > maxBinLength (${this.maxBinLength})`,      );    }
    if (!this.hasRemaining(byteLength + headOffset)) {      throw MORE_DATA;    }
    const offset = this.pos + headOffset;    const object = this.bytes.subarray(offset, offset + byteLength);    this.pos += headOffset + byteLength;    return object;  }
  private decodeExtension(size: number, headOffset: number): unknown {    if (size > this.maxExtLength) {      throw new Error(        `Max length exceeded: ext length (${size}) > maxExtLength (${this.maxExtLength})`,      );    }
    const extType = this.view.getInt8(this.pos + headOffset);    const data = this.decodeBinary(size, headOffset + 1 /* extType */);    return this.extensionCodec.decode(data, extType, this.context);  }
  private lookU8() {    return this.view.getUint8(this.pos);  }
  private lookU16() {    return this.view.getUint16(this.pos);  }
  private lookU32() {    return this.view.getUint32(this.pos);  }
  private readU8(): number {    const value = this.view.getUint8(this.pos);    this.pos++;    return value;  }
  private readI8(): number {    const value = this.view.getInt8(this.pos);    this.pos++;    return value;  }
  private readU16(): number {    const value = this.view.getUint16(this.pos);    this.pos += 2;    return value;  }
  private readI16(): number {    const value = this.view.getInt16(this.pos);    this.pos += 2;    return value;  }
  private readU32(): number {    const value = this.view.getUint32(this.pos);    this.pos += 4;    return value;  }
  private readI32(): number {    const value = this.view.getInt32(this.pos);    this.pos += 4;    return value;  }
  private readU64(): number {    const value = getUint64(this.view, this.pos);    this.pos += 8;    return value;  }
  private readI64(): number {    const value = getInt64(this.view, this.pos);    this.pos += 8;    return value;  }
  private readF32() {    const value = this.view.getFloat32(this.pos);    this.pos += 4;    return value;  }
  private readF64() {    const value = this.view.getFloat64(this.pos);    this.pos += 8;    return value;  }}