export enum IsDictionaryOfErrorCode {
    IS_NULL = "IS_NULL",
    IS_UNDEFINED = "IS_UNDEFINED",
    ELEMENT_FAILED_PREDICATE = "ELEMENT_FAILED_PREDICATE"
}

export type ElementPredicate<ErrorCodeT> = ((element : any) => (undefined|ErrorCodeT))|((element : any) => boolean);

/*
    TODO Replace `any` with proper constraints
*/
export type IsDictionaryOfResult<ErrorCodeT extends string|IsDictionaryOfResult<any>> = (
    IsDictionaryOfErrorCode.IS_NULL |
    IsDictionaryOfErrorCode.IS_UNDEFINED |
    {
        index? : number|string,
        argIndex? : number|string,
        error : IsDictionaryOfErrorCode.ELEMENT_FAILED_PREDICATE
    } |
    {
        index? : number|string,
        argIndex? : number|string,
        error : ErrorCodeT
    }
)

//ErrorCodeT should be an enum
export function checkDictionaryOf<ErrorCodeT extends string|{ index? : number|string, argIndex? : number|string, forcedArg? : any, error : any }> (mixed : any, elementPredicate : ElementPredicate<ErrorCodeT>) : undefined|IsDictionaryOfResult<ErrorCodeT> {
    if (mixed === null) {
        return IsDictionaryOfErrorCode.IS_NULL;
    }
    if (mixed === undefined) {
        return IsDictionaryOfErrorCode.IS_UNDEFINED;
    }

    for (let k in mixed) {
        if (mixed.hasOwnProperty(k)) {
            const item = mixed[k];
            const result = elementPredicate(item);
            if (typeof result == "boolean") {
                if (!result) {
                    return {
                        index : k,
                        error : IsDictionaryOfErrorCode.ELEMENT_FAILED_PREDICATE
                    };
                }
            } else {
                if (result !== undefined) {
                    return {
                        index : k,
                        error : result
                    };
                }
            }
        }
    }
    return undefined;
}