preserves/implementations/javascript/packages/core/src/pointer.ts

import type { EncoderState } from "./encoder";
import type { DecoderState } from "./decoder";
import type { Value } from "./values";

export type PointerTypeEncode<T> = {
    encode(s: EncoderState, v: T): void;
    toValue(v: T): Value<GenericPointer>;
}

export type PointerTypeDecode<T> = {
    decode(s: DecoderState): T;
    fromValue(v: Value<GenericPointer>): T;
}

export type PointerType<T> = PointerTypeEncode<T> & PointerTypeDecode<T>;

export class Pointer<T> {
    embeddedValue: T;

    constructor(embeddedValue: T) {
        this.embeddedValue = embeddedValue;
    }

    equals(other: any, is: (a: any, b: any) => boolean) {
        return isPointer<T>(other) && is(this.embeddedValue, other.embeddedValue);
    }

    asPreservesText(): string {
        return '#!' + (this.embeddedValue as any).asPreservesText();
    }
}

export function embed<T>(embeddedValue: T): Pointer<T> {
    return new Pointer(embeddedValue);
}

export function isPointer<T>(v: Value<T>): v is Pointer<T> {
    return typeof v === 'object' && 'embeddedValue' in v;
}

export class GenericPointer {
    generic: Value;

    constructor(generic: Value) {
        this.generic = generic;
    }

    equals(other: any, is: (a: any, b: any) => boolean) {
        return typeof other === 'object' && 'generic' in other && is(this.generic, other.generic);
    }

    asPreservesText(): string {
        return this.generic.asPreservesText();
    }
}