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// ExtensionCodec to handle MessagePack extensions
import { ExtData } from "./ExtData.ts";import { timestampExtension } from "./timestamp.ts";
export type ExtensionDecoderType<ContextType> = (  data: Uint8Array,  extensionType: number,  context: ContextType,) => unknown;
export type ExtensionEncoderType<ContextType> = (  input: unknown,  context: ContextType,) => Uint8Array | null;
// immutable interfce to ExtensionCodecexport type ExtensionCodecType<ContextType> = {  // eslint-disable-next-line @typescript-eslint/naming-convention  __brand?: ContextType;  tryToEncode(object: unknown, context: ContextType): ExtData | null;  decode(data: Uint8Array, extType: number, context: ContextType): unknown;};
export class ExtensionCodec<ContextType = undefined>  implements ExtensionCodecType<ContextType> {  public static readonly defaultCodec: ExtensionCodecType<undefined> =    new ExtensionCodec();
  // ensures ExtensionCodecType<X> matches ExtensionCodec<X>  // this will make type errors a lot more clear  // eslint-disable-next-line @typescript-eslint/naming-convention  __brand?: ContextType;
  // built-in extensions  private readonly builtInEncoders: Array<    ExtensionEncoderType<ContextType> | undefined | null  > = [];  private readonly builtInDecoders: Array<    ExtensionDecoderType<ContextType> | undefined | null  > = [];
  // custom extensions  private readonly encoders: Array<    ExtensionEncoderType<ContextType> | undefined | null  > = [];  private readonly decoders: Array<    ExtensionDecoderType<ContextType> | undefined | null  > = [];
  public constructor() {    this.register(timestampExtension);  }
  public register({    type,    encode,    decode,  }: {    type: number;    encode: ExtensionEncoderType<ContextType>;    decode: ExtensionDecoderType<ContextType>;  }): void {    if (type >= 0) {      // custom extensions      this.encoders[type] = encode;      this.decoders[type] = decode;    } else {      // built-in extensions      const index = 1 + type;      this.builtInEncoders[index] = encode;      this.builtInDecoders[index] = decode;    }  }
  public tryToEncode(object: unknown, context: ContextType): ExtData | null {    // built-in extensions    for (let i = 0; i < this.builtInEncoders.length; i++) {      const encoder = this.builtInEncoders[i];      if (encoder != null) {        const data = encoder(object, context);        if (data != null) {          const type = -1 - i;          return new ExtData(type, data);        }      }    }
    // custom extensions    for (let i = 0; i < this.encoders.length; i++) {      const encoder = this.encoders[i];      if (encoder != null) {        const data = encoder(object, context);        if (data != null) {          const type = i;          return new ExtData(type, data);        }      }    }
    if (object instanceof ExtData) {      // to keep ExtData as is      return object;    }    return null;  }
  public decode(data: Uint8Array, type: number, context: ContextType): unknown {    const decoder = type < 0      ? this.builtInDecoders[-1 - type]      : this.decoders[type];    if (decoder) {      return decoder(data, type, context);    } else {      // decode() does not fail, returns ExtData instead.      return new ExtData(type, data);    }  }}