TSinjex/src/decorators/Inject.ts

import { TSinjex } from "../classes/mod.ts";
import { InitializationError } from "../interfaces/mod.ts";
import { Identifier, InitDelegate } from "../types/mod.ts";

export function Inject<InstanzType, DependencyType, FieldType extends object>(
    identifier: Identifier,
    init?: InitDelegate<DependencyType, FieldType>,
    isNecessary = true,
): (
    target: undefined,
    context: ClassFieldDecoratorContext<InstanzType, FieldType>,
) => (initialValue: FieldType) => FieldType {
    return function (
        _target: undefined,
        context: ClassFieldDecoratorContext<InstanzType, FieldType>,
    ): (initialValue: FieldType) => FieldType {
        if (context.kind !== "field") {
            throw new Error("Inject decorator can only be used on fields.");
        }

        const initializer = () => {
            let instance: DependencyType | FieldType | undefined;

            const dependency: DependencyType | undefined = TSinjex.getInstance()
                .resolve<DependencyType>(identifier, isNecessary);

            if (init == null || dependency == null) {
                instance = dependency;
            } else {
                try {
                    instance = init(dependency);
                } catch (error) {
                    if (isNecessary) {
                        throw new InitializationError(
                            identifier,
                            error instanceof Error ? error : new Error(String(error)),
                        );
                    } else {
                        console.warn(
                            `Error initializing not necessary dependency ${identifier.toString()}: ${error}`,
                        );
                        instance = undefined;
                    }
                }
            }

            return instance as FieldType;
        };

        return function (_initialValue: FieldType): FieldType {
            return initializer();
        };
    };
}