import { Bytes, Value, Record, Set, Dictionary, Single, Double, Annotated, annotate, Float } from "./values";

export type Fold<T extends object, R = Value<T>> = (v: Value<T>) => R;

export interface FoldMethods<T extends object, R> {
    boolean(b: boolean): R;
    single(f: number): R;
    double(f: number): R;
    integer(i: number): R;
    string(s: string): R;
    bytes(b: Bytes): R;
    symbol(s: symbol): R;

    record(r: Record<any, any, T>, k: Fold<T, R>): R;
    array(a: Array<Value<T>>, k: Fold<T, R>): R;
    set(s: Set<T>, k: Fold<T, R>): R;
    dictionary(d: Dictionary<Value<T>, T>, k: Fold<T, R>): R;

    annotated(a: Annotated<T>, k: Fold<T, R>): R;

    pointer(t: T, k: Fold<T, R>): R;
}

export abstract class ValueFold<T extends object, R extends object = T> implements FoldMethods<T, Value<R>> {
    boolean(b: boolean): Value<R> {
        return b;
    }
    single(f: number): Value<R> {
        return Single(f);
    }
    double(f: number): Value<R> {
        return Double(f);
    }
    integer(i: number): Value<R> {
        return i;
    }
    string(s: string): Value<R> {
        return s;
    }
    bytes(b: Bytes): Value<R> {
        return b;
    }
    symbol(s: symbol): Value<R> {
        return s;
    }
    record(r: Record<any, any, T>, k: Fold<T, Value<R>>): Value<R> {
        return Record(k(r.label), r.map(k));
    }
    array(a: Value<T>[], k: Fold<T, Value<R>>): Value<R> {
        return a.map(k);
    }
    set(s: Set<T>, k: Fold<T, Value<R>>): Value<R> {
        return s.map(k);
    }
    dictionary(d: Dictionary<Value<T>, T>, k: Fold<T, Value<R>>): Value<R> {
        return d.mapEntries(([key, value]) => [k(key), k(value)]);
    }
    annotated(a: Annotated<T>, k: Fold<T, Value<R>>): Value<R> {
        return annotate(k(a.item), ...a.annotations.map(k));
    }
    abstract pointer(t: T, k: Fold<T, Value<R>>): Value<R>;
}

export class IdentityFold<T extends object> extends ValueFold<T, T> {
    pointer(t: T, _k: Fold<T, Value<T>>): Value<T> {
        return t;
    }
}

export class MapFold<T extends object, R extends object> extends ValueFold<T, R> {
    readonly f: (t: T) => R;

    constructor(f: (t: T) => R) {
        super();
        this.f = f;
    }

    pointer(t: T, _k: Fold<T, Value<R>>): Value<R> {
        return this.f(t);
    }
}

export const IDENTITY_FOLD = new IdentityFold();

export function fold<T extends object, R>(v: Value<T>, o: FoldMethods<T, R>): R {
    const walk = (v: Value<T>): R => {
        switch (typeof v) {
            case 'boolean':
                return o.boolean(v);
            case 'number':
                if (!Number.isInteger(v)) {
                    // TODO: Is this convenience warranted?
                    return o.double(v);
                } else {
                    return o.integer(v);
                }
            case 'string':
                return o.string(v);
            case 'symbol':
                return o.symbol(v);
            case 'object':
                if (Record.isRecord<T>(v)) {
                    return o.record(v, walk);
                } else if (Array.isArray(v)) {
                    return o.array(v, walk);
                } else if (Set.isSet<T>(v)) {
                    return o.set(v, walk);
                } else if (Dictionary.isDictionary<Value<T>, T>(v)) {
                    return o.dictionary(v, walk);
                } else if (Annotated.isAnnotated<T>(v)) {
                    return o.annotated(v, walk);
                } else if (Bytes.isBytes(v)) {
                    return o.bytes(v);
                } else if (Float.isSingle(v)) {
                    return o.single(v.value);
                } else if (Float.isDouble(v)) {
                    return o.double(v.value);
                } else {
                    /* fall through */
                }
            default:
                return o.pointer(v, walk);
        }
    };
    return walk(v);
}

export function mapPointers<T extends object, R extends object>(
    v: Value<T>,
    f: (t: T) => R,
): Value<R>
{
    return fold(v, new MapFold(f));
}