1 files changed, 87 insertions, 0 deletions

diff --git a/src/new_fields/Types.ts b/src/new_fields/Types.ts
new file mode 100644
index 000000000..60f08dc90
--- /dev/null
+++ b/src/new_fields/Types.ts
@@ -0,0 +1,87 @@
+import { Field, Opt, FieldResult } from "./Doc";
+import { List } from "./List";
+
+export type ToType<T extends ToConstructor<Field> | ListSpec<Field>> =
+    T extends "string" ? string :
+    T extends "number" ? number :
+    T extends "boolean" ? boolean :
+    T extends ListSpec<infer U> ? List<U> :
+    // T extends { new(...args: any[]): infer R } ? (R | Promise<R>) : never;
+    T extends { new(...args: any[]): List<Field> } ? never :
+    T extends { new(...args: any[]): infer R } ? R : never;
+
+export type ToConstructor<T extends Field> =
+    T extends string ? "string" :
+    T extends number ? "number" :
+    T extends boolean ? "boolean" :
+    T extends List<infer U> ? ListSpec<U> :
+    new (...args: any[]) => T;
+
+export type ToInterface<T extends Interface> = {
+    [P in Exclude<keyof T, "proto">]: FieldResult<ToType<T[P]>>;
+};
+
+// type ListSpec<T extends Field[]> = { List: ToContructor<Head<T>> | ListSpec<Tail<T>> };
+export type ListSpec<T extends Field> = { List: ToConstructor<T> };
+
+// type ListType<U extends Field[]> = { 0: List<ListType<Tail<U>>>, 1: ToType<Head<U>> }[HasTail<U> extends true ? 0 : 1];
+
+export type Head<T extends any[]> = T extends [any, ...any[]] ? T[0] : never;
+export type Tail<T extends any[]> =
+    ((...t: T) => any) extends ((_: any, ...tail: infer TT) => any) ? TT : [];
+export type HasTail<T extends any[]> = T extends ([] | [any]) ? false : true;
+
+//TODO Allow you to optionally specify default values for schemas, which should then make that field not be partial
+export interface Interface {
+    [key: string]: ToConstructor<Field> | ListSpec<Field>;
+    // [key: string]: ToConstructor<Field> | ListSpec<Field[]>;
+}
+
+export function Cast<T extends ToConstructor<Field> | ListSpec<Field>>(field: FieldResult, ctor: T): FieldResult<ToType<T>>;
+export function Cast<T extends ToConstructor<Field> | ListSpec<Field>>(field: FieldResult, ctor: T, defaultVal: WithoutList<ToType<T>> | null): WithoutList<ToType<T>>;
+export function Cast<T extends ToConstructor<Field> | ListSpec<Field>>(field: FieldResult, ctor: T, defaultVal?: ToType<T> | null): FieldResult<ToType<T>> | undefined {
+    if (field instanceof Promise) {
+        return defaultVal === undefined ? field.then(f => Cast(f, ctor) as any) as any : defaultVal === null ? undefined : defaultVal;
+    }
+    if (field !== undefined && !(field instanceof Promise)) {
+        if (typeof ctor === "string") {
+            if (typeof field === ctor) {
+                return field as ToType<T>;
+            }
+        } else if (typeof ctor === "object") {
+            if (field instanceof List) {
+                return field as any;
+            }
+        } else if (field instanceof (ctor as any)) {
+            return field as ToType<T>;
+        }
+    }
+    return defaultVal === null ? undefined : defaultVal;
+}
+
+export function NumCast(field: FieldResult, defaultVal: number | null = 0) {
+    return Cast(field, "number", defaultVal);
+}
+
+export function StrCast(field: FieldResult, defaultVal: string | null = "") {
+    return Cast(field, "string", defaultVal);
+}
+
+export function BoolCast(field: FieldResult, defaultVal: boolean | null = null) {
+    return Cast(field, "boolean", defaultVal);
+}
+
+type WithoutList<T extends Field> = T extends List<infer R> ? R[] : T;
+
+export function FieldValue<T extends Field, U extends WithoutList<T>>(field: FieldResult<T>, defaultValue: U): WithoutList<T>;
+export function FieldValue<T extends Field>(field: FieldResult<T>): Opt<T>;
+export function FieldValue<T extends Field>(field: FieldResult<T>, defaultValue?: T): Opt<T> {
+    return (field instanceof Promise || field === undefined) ? defaultValue : field;
+}
+
+export interface PromiseLike<T> {
+    then(callback: (field: Opt<T>) => void): void;
+}
+export function PromiseValue<T extends Field>(field: FieldResult<T>): PromiseLike<Opt<T>> {
+    return field instanceof Promise ? field : { then(cb: ((field: Opt<T>) => void)) { return cb(field); } };
+}
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