package com.sample.javaValidators;

import static com.sample.javaValidators.ValidationResult.invalid;

import static com.sample.javaValidators.ValidationResult.valid;

import java.util.Arrays;

import java.util.function.Function;

import java.util.function.Predicate;

import java.util.stream.Collectors;

public interface UserValidation extends Function<User, ValidationResult> {

static UserValidation nameisNotEmpty(){

return holds(user -> !user.name.trim().isEmpty(), "Name is empty.");

}

static UserValidation holds(Predicate<User> p, String message){

return user -> p.test(user) ? valid() : invalid(message);

}

static UserValidation emailisValid(){

return holds(user -> user.email.contains("@"), "Missing @-sign.");

}

default UserValidation and(UserValidation other){

return user -> {

final ValidationResult result = this.apply(user);

return result.isValid() ? other.apply(user) : result;

};

}

default UserValidation or(UserValidation other){

return user -> {

final ValidationResult result = this.apply(user);

return result.isValid() ? other.apply(user) : result;

};

}

static UserValidation all(UserValidation... validations){

return user -> {

String reasons = Arrays.stream(validations)

.map(v -> v.apply(user))

.filter(r -> !r.isValid())

.map(r -> r.getReason().get())

.collect(Collectors.joining("\n"));

return reasons.isEmpty()?valid():invalid(reasons);

};

}

}