import { Encoder } from "./codec";
import { Tag } from "./constants";
import { AsPreserve, PreserveOn } from "./symbols";
import { DefaultPointer, is, Value } from "./values";
import { Record } from './record';
import { Dictionary, Set } from './dictionary';

export const IsPreservesAnnotated = Symbol.for('IsPreservesAnnotated');

export class Annotated<T extends object = DefaultPointer> {
    readonly annotations: Array<Value<T>>;
    readonly item: Value<T>;

    constructor(item: Value<T>) {
        this.annotations = [];
        this.item = item;
    }

    [AsPreserve](): Value<T> {
        return this;
    }

    [PreserveOn](encoder: Encoder<T>) {
        if (encoder.includeAnnotations) {
            for (const a of this.annotations) {
                encoder.emitbyte(Tag.Annotation);
                encoder.push(a);
            }
        }
        encoder.push(this.item);
    }

    equals(other: any): boolean {
        return is(this.item, Annotated.isAnnotated(other) ? other.item : other);
    }

    // hashCode(): number {
    //     return hash(this.item);
    // }

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

    asPreservesText(): string {
        const anns = this.annotations.map((a) => '@' + a.asPreservesText()).join(' ');
        return (anns ? anns + ' ' : anns) + this.item.asPreservesText();
    }

    get [IsPreservesAnnotated](): boolean {
        return true;
    }

    static isAnnotated<T extends object = DefaultPointer>(x: any): x is Annotated<T> {
        return !!x?.[IsPreservesAnnotated];
    }
}

export function peel<T extends object = DefaultPointer>(v: Value<T>): Value<T> {
    return strip(v, 1);
}

export function strip<T extends object = DefaultPointer>(v: Value<T>, depth: number = Infinity): Value<T> {
    function step(v: Value<T>, depth: number): Value<T> {
        if (depth === 0) return v;
        if (!Annotated.isAnnotated<T>(v)) return v;

        const nextDepth = depth - 1;
        function walk(v: Value<T>): Value<T> { return step(v, nextDepth); }

        if (Record.isRecord<T>(v.item)) {
            return Record(step(v.item.label, depth), v.item.map(walk));
        } else if (Array.isArray(v.item)) {
            return (v.item as Array<Value<T>>).map(walk);
        } else if (Set.isSet<T>(v.item)) {
            return v.item.map(walk);
        } else if (Dictionary.isDictionary<Value<T>, T>(v.item)) {
            return v.item.mapEntries((e) => [walk(e[0]), walk(e[1])]);
        } else if (Annotated.isAnnotated(v.item)) {
            throw new Error("Improper annotation structure");
        } else {
            return v.item;
        }
    }
    return step(v, depth);
}

export function annotate<T extends object = DefaultPointer>(v0: Value<T>, ...anns: Value<T>[]): Annotated<T> {
    const v = Annotated.isAnnotated<T>(v0) ? v0 : new Annotated(v0);
    anns.forEach((a) => v.annotations.push(a));
    return v;
}