package com.github.yin.flags;

/**

* Provides Flag value access and validation to client classes. Flag value is injected into static

* fields of type {@link Flag} and accessed using {@link #get()}.

*

* {@link #parse(String)} is never used by client classes, but should be implemented if a custom

* return type is desired from {@link #get()}.

*

* @author yin

*/

public interface Flag<T> {

/**

* Validates parsed flag values. May be used to enforce compile-time constraints safely and

* also run-time if care is taken to avoid lockup in a mutually recursive chain of {@link #get()}'s.

*/

@FunctionalInterface

interface Validator<T> {

void validate(T value);

}

/**

* Attaches a {@link Validator} function to this flag instance.

*/

Flag validator(Validator<T> validator);

/**

* Attempts parsing a {@link String} representation of a value and is responsible for calling

* the validator function afterwards.

*/

void parse(String value);

/**

* Returns value stored in the flag, possibly a default value.

*/

T get();

}