traitify-ts/src/Trait.ts

import { Fn, Pipe, Tuples } from "hotscript"
import { AbstractClass, Class, Opaque } from "type-fest"
import { TraitExpression, emptyTraitExpression } from "./TraitExpression"
import { AbstractTag } from "./abstract"
import { ExtendFn, SimplifyFn, StaticMembers, StaticMembersFn } from "./util"


export type TraitApplierSuperTag = "@thilawyn/traitify-ts/TraitApplierSuper"


export type AddAbstractToImplClass<
    ImplClass extends Class<{}, []>,
    Abstract  extends {},
> = (
    Class<
        Abstract & InstanceType<ImplClass>,
        ConstructorParameters<ImplClass>
    > &
    StaticMembers<ImplClass>
)

export type RemoveAbstractFromImplClass<
    ImplClassWithAbstract extends Class<Abstract, []> & { _tag: TraitApplierSuperTag },
    Abstract              extends {},
> = (
    Class<
        Omit<InstanceType<ImplClassWithAbstract>, keyof Abstract>,
        ConstructorParameters<ImplClassWithAbstract>
    > &
    Omit<StaticMembers<ImplClassWithAbstract>, "_tag">
)


export class Trait<
    Supertraits extends TraitExpression<typeof TraitExpression.NullSuperclass, Trait<any, any, any>[], Trait<any, any, any>[]>,
    Abstract    extends {},
    ImplClass   extends Class<{}, []>,
> {
    constructor(
        readonly supertraits:  Supertraits,
        readonly abstract:     Abstract,
        readonly apply:        (Super: AbstractClass<{}>) => ImplClass,
    ) {}
}

export namespace Trait {
    export type OwnSupertraits<T> = (
        T extends Trait<infer Supertraits, any, any>
            ? Supertraits
            : never
    )
    export interface OwnSupertraitsFn extends Fn {
        return: Trait.OwnSupertraits<this["arg0"]>
    }

    export type OwnAbstract<T> = (
        T extends Trait<any, infer Abstract, any>
            ? Abstract
            : never
    )
    export interface OwnAbstractFn extends Fn {
        return: Trait.OwnAbstract<this["arg0"]>
    }

    export type OwnImplClass<T> = (
        T extends Trait<any, any, infer ImplClass>
            ? ImplClass
            : never
    )
    export interface OwnImplClassFn extends Fn {
        return: Trait.OwnImplClass<this["arg0"]>
    }

    export type OwnImplInstance<T> = (
        T extends Trait<any, any, infer ImplClass>
            ? InstanceType<ImplClass>
            : never
    )
    export interface OwnImplInstanceFn extends Fn {
        return: Trait.OwnImplInstance<this["arg0"]>
    }

    export type OwnClass<T> = (
        T extends Trait<any, infer Abstract, infer ImplClass>
            ? AddAbstractToImplClass<ImplClass, Abstract>
            : never
    )
    export interface OwnClassFn extends Fn {
        return: Trait.OwnClass<this["arg0"]>
    }

    export type OwnInstance<T> = (
        T extends Trait<any, infer Abstract, infer ImplClass>
            ? InstanceType<
                AddAbstractToImplClass<ImplClass, Abstract>
            >
            : never
    )
    export interface OwnInstanceFn extends Fn {
        return: Trait.OwnInstance<this["arg0"]>
    }

    export type Supertraits<T> = (
        T extends Trait<infer Supertraits, any, any>
            ? TraitExpression.AllTraits<Supertraits>
            : never
    )
    export interface SupertraitsFn extends Fn {
        return: Trait.Supertraits<this["arg0"]>
    }

    export type Class<T> = (
        AbstractClass<
            Trait.Instance<T>,
            any[]
        > &
        Pipe<T, [
            Trait.SupertraitsFn,
            Tuples.Append<T>,
            Tuples.Map<Trait.OwnClassFn>,
            Tuples.Map<StaticMembersFn>,
            ExtendFn,
            SimplifyFn,
        ]>
    )
    export interface ClassFn extends Fn {
        return: Trait.Class<this["arg0"]>
    }

    export type Instance<T> = (
        Pipe<T, [
            Trait.SupertraitsFn,
            Tuples.Append<T>,
            Tuples.Map<Trait.OwnInstanceFn>,
            ExtendFn,
            SimplifyFn,
        ]>
    )
    export interface InstanceFn extends Fn {
        return: Trait.Instance<this["arg0"]>
    }
}


export function trait<
    Abstract              extends {},
    ImplClassWithAbstract extends Class<Abstract, []> & { _tag: TraitApplierSuperTag },
>(
    abstract:  Opaque<Abstract, AbstractTag>,
    apply:     (Super: AbstractClass<Abstract> & { _tag: TraitApplierSuperTag }) => ImplClassWithAbstract,
) {
    return new Trait(
        emptyTraitExpression,
        abstract as Abstract,
        apply    as any as (Super: AbstractClass<{}>) => RemoveAbstractFromImplClass<ImplClassWithAbstract, Abstract>,
    )
}