135 lines
4.0 KiB
TypeScript
135 lines
4.0 KiB
TypeScript
import { Bytes, Value, Record, Set, Dictionary, Single, Double, Annotated, annotate, Float } from "./values";
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export type Fold<T extends object, R = Value<T>> = (v: Value<T>) => R;
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export interface FoldMethods<T extends object, R> {
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boolean(b: boolean): R;
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single(f: number): R;
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double(f: number): R;
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integer(i: number): R;
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string(s: string): R;
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bytes(b: Bytes): R;
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symbol(s: symbol): R;
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record(r: Record<any, any, T>, k: Fold<T, R>): R;
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array(a: Array<Value<T>>, k: Fold<T, R>): R;
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set(s: Set<T>, k: Fold<T, R>): R;
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dictionary(d: Dictionary<Value<T>, T>, k: Fold<T, R>): R;
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annotated(a: Annotated<T>, k: Fold<T, R>): R;
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pointer(t: T, k: Fold<T, R>): R;
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}
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export abstract class ValueFold<T extends object, R extends object = T> implements FoldMethods<T, Value<R>> {
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boolean(b: boolean): Value<R> {
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return b;
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}
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single(f: number): Value<R> {
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return Single(f);
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}
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double(f: number): Value<R> {
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return Double(f);
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}
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integer(i: number): Value<R> {
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return i;
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}
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string(s: string): Value<R> {
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return s;
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}
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bytes(b: Bytes): Value<R> {
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return b;
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}
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symbol(s: symbol): Value<R> {
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return s;
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}
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record(r: Record<any, any, T>, k: Fold<T, Value<R>>): Value<R> {
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return Record(k(r.label), r.map(k));
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}
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array(a: Value<T>[], k: Fold<T, Value<R>>): Value<R> {
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return a.map(k);
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}
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set(s: Set<T>, k: Fold<T, Value<R>>): Value<R> {
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return s.map(k);
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}
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dictionary(d: Dictionary<Value<T>, T>, k: Fold<T, Value<R>>): Value<R> {
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return d.mapEntries(([key, value]) => [k(key), k(value)]);
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}
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annotated(a: Annotated<T>, k: Fold<T, Value<R>>): Value<R> {
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return annotate(k(a.item), ...a.annotations.map(k));
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}
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abstract pointer(t: T, k: Fold<T, Value<R>>): Value<R>;
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}
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export class IdentityFold<T extends object> extends ValueFold<T, T> {
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pointer(t: T, _k: Fold<T, Value<T>>): Value<T> {
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return t;
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}
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}
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export class MapFold<T extends object, R extends object> extends ValueFold<T, R> {
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readonly f: (t: T) => R;
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constructor(f: (t: T) => R) {
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super();
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this.f = f;
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}
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pointer(t: T, _k: Fold<T, Value<R>>): Value<R> {
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return this.f(t);
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}
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}
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export const IDENTITY_FOLD = new IdentityFold();
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export function fold<T extends object, R>(v: Value<T>, o: FoldMethods<T, R>): R {
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const walk = (v: Value<T>): R => {
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switch (typeof v) {
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case 'boolean':
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return o.boolean(v);
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case 'number':
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if (!Number.isInteger(v)) {
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// TODO: Is this convenience warranted?
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return o.double(v);
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} else {
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return o.integer(v);
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}
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case 'string':
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return o.string(v);
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case 'symbol':
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return o.symbol(v);
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case 'object':
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if (Record.isRecord<T>(v)) {
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return o.record(v, walk);
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} else if (Array.isArray(v)) {
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return o.array(v, walk);
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} else if (Set.isSet<T>(v)) {
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return o.set(v, walk);
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} else if (Dictionary.isDictionary<Value<T>, T>(v)) {
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return o.dictionary(v, walk);
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} else if (Annotated.isAnnotated<T>(v)) {
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return o.annotated(v, walk);
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} else if (Bytes.isBytes(v)) {
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return o.bytes(v);
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} else if (Float.isSingle(v)) {
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return o.single(v.value);
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} else if (Float.isDouble(v)) {
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return o.double(v.value);
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} else {
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/* fall through */
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}
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default:
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return o.pointer(v, walk);
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}
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};
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return walk(v);
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}
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export function mapPointers<T extends object, R extends object>(
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v: Value<T>,
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f: (t: T) => R,
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): Value<R>
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{
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return fold(v, new MapFold(f));
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}
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