core_ng/server/ProcDecorator/base.ts

import type { Request, Response } from "express";

type MayBePromise<T> = T | Promise<T>;

export type Empty = Record<string, never>;
export type DecoratorResultTrue = {
    result: true;
    type?: string;
    info?: string;
};
export type DecoratorResultFalse = {
    result: false;
    type: string;
    info: string;
}
export type DecoratorResult = DecoratorResultTrue | DecoratorResultFalse;
export type DecoratorStack = DecoratorResult[];

export interface ProcDecorator<Out extends object, In = Empty> {
    (inCtx: In & Partial<Out>, req: Request, res: Response)
        : MayBePromise<[DecoratorResultTrue, Out] | [DecoratorResultFalse, In & Partial<Out>]>;
}

export interface PostProcDecorator<T extends object> {
    (ctx: T, preResult: DecoratorResult, req: Request, res: Response, isValidRoute: boolean): MayBePromise<[DecoratorResult, T]>;
}

export interface ProcDecoratorRunner<Out extends object, In> {
    (inCtx: In, req: Request, res: Response): MayBePromise<[DecoratorStack, Out]>;
}

export interface PostProcDecoratorRunner<T extends object> {
    (ctx: T, preResult: DecoratorStack, req: Request, res: Response, isValidRoute: boolean): MayBePromise<[DecoratorStack, T]>;
}


// eslint-disable-next-line @typescript-eslint/no-explicit-any
type PlainDecorator = ProcDecorator<any, any>;
// eslint-disable-next-line @typescript-eslint/no-explicit-any
type PlainPostDecorator = PostProcDecorator<any>;


export type ProcDecoratorGenerator<Out extends object, In = Empty> = ProcDecorator<Out & In, In>;
export type ProcDecoratorPrePostGenerator<Out extends object, In> = [ProcDecorator<Out & In, In>, PostProcDecorator<Out & In>];

export type ProcDecoratorChain = readonly ((() => PlainDecorator) | (() => [PlainDecorator, PlainPostDecorator]))[];

export type ResolveChain<T> = T extends undefined ? Empty : T extends ProcDecoratorChain ? Resolve<PackChain<T>> : never;


// eslint-disable-next-line @typescript-eslint/no-explicit-any
export type ParseInType<T> = T extends ProcDecorator<any, infer A> ? object extends A ? A : never : never;
// eslint-disable-next-line @typescript-eslint/no-explicit-any
export type ParseOutType<T> = T extends ProcDecorator<infer B, object> ? B : never;

export const EmptyProcDecorator: readonly [ProcDecoratorRunner<Empty, Empty>, PostProcDecoratorRunner<Empty>] = [
    async (ctx) => [[], ctx], async (ctx, stack) => [stack, ctx]
];

export function declProcDecorators<T extends ProcDecoratorChain>(...decorators: T) {
    type OutType = Resolve<PackChain<T>>;

    const preDecorator: PlainDecorator[] = [];
    const postDecorator: (PlainPostDecorator | undefined)[] = [];
    if (decorators) {
        for (const procGen of decorators) {
            const proc = procGen();
            if (Array.isArray(proc)) {
                preDecorator.push(proc[0]);
                postDecorator.push(proc[1]);
            }
            else {
                preDecorator.push(proc);
                postDecorator.push(undefined);
            }
        }
    }

    const packedDecorators: readonly [ProcDecoratorRunner<OutType, Empty>, PostProcDecoratorRunner<OutType>] = [
        async (ctx, req, res) => {
            let rctx = ctx as unknown as OutType;
            const decoratorStack: DecoratorStack = [];
            if (!preDecorator.length) {
                return [decoratorStack, rctx];
            }

            for (const [idx, proc] of preDecorator.entries()) {
                try {
                    const [stackResult, newCtx] = await proc(rctx, req, res);
                    decoratorStack.push(stackResult);

                    if (stackResult.result) {
                        rctx = newCtx;
                        continue;
                    }

                    return [decoratorStack, newCtx];
                }
                catch (e) {
                    while (decoratorStack.length > idx) {
                        decoratorStack.pop();
                    }
                    decoratorStack.push({
                        result: false,
                        type: 'PreThrow',
                        info: `internal error: ${e}`,
                    });

                    return [decoratorStack, rctx];
                }
            }

            return [decoratorStack, rctx];
        },
        async (ctx, stack, req, res) => {
            if (!postDecorator.length) {
                return [stack, ctx];
            }
            let isValidRoute = stack.length === postDecorator.length && stack.every(v => v.result);
            for (let idx = stack.length - 1; idx >= 0; idx--) {
                const preStackResult = stack[idx] as DecoratorResult;
                if (!preStackResult.result) {
                    continue;
                }

                const proc = postDecorator[idx];

                if (!proc) {
                    if (isValidRoute) {
                        stack.pop();
                    }
                    continue;
                }

                try {
                    const [postStackResult, nextCtx] = await proc(ctx, preStackResult, req, res, isValidRoute);
                    if (postStackResult.result) {
                        if (isValidRoute) {
                            stack.pop();
                        }
                        ctx = nextCtx;
                        continue;
                    }

                    isValidRoute = false;
                    stack[idx] = postStackResult;

                    ctx = nextCtx;
                }
                catch (e) {
                    isValidRoute = false;
                    stack[idx] = {
                        result: false,
                        type: 'PostThrow',
                        info: `internal error: ${e}`,
                    };
                }

            }
            return [stack, ctx];
        },
    ] as const;

    return packedDecorators;
}

type Compose2<D extends object, C, B, A = Empty> = B extends C ? ProcDecorator<D & B, A> : never;

type PD1<B extends object, A extends object> = () => ProcDecorator<B, A>;
// eslint-disable-next-line @typescript-eslint/no-explicit-any
type PD2<B extends object, A extends object> = () => [ProcDecorator<B, A>, PostProcDecorator<any>];

export type PackChain<T> =
    T extends readonly [] ? ProcDecorator<Empty, Empty> :
    T extends readonly [PD1<infer B, infer A>] ? ProcDecorator<B, A> :
    T extends readonly [PD2<infer B, infer A>] ? ProcDecorator<B, A> :
    T extends readonly [PD1<infer B, infer A>, PD1<infer D, infer C>, ... infer R] ? PackChain<[() => Compose2<D, C, B, A>, ...R]> :
    T extends readonly [PD2<infer B, infer A>, PD1<infer D, infer C>, ... infer R] ? PackChain<[() => Compose2<D, C, B, A>, ...R]> :
    T extends readonly [PD1<infer B, infer A>, PD2<infer D, infer C>, ... infer R] ? PackChain<[() => Compose2<D, C, B, A>, ...R]> :
    T extends readonly [PD2<infer B, infer A>, PD2<infer D, infer C>, ... infer R] ? PackChain<[() => Compose2<D, C, B, A>, ...R]> :
    never;

type Resolve<T> = T extends ProcDecorator<infer B, infer A> ? Empty extends A ? B : never : never;