/**
 Copyright (c) 2014-present, Facebook, Inc.
 All rights reserved.

 This source code is licensed under the BSD-style license found in the
 LICENSE file in the root directory of this source tree. An additional grant
 of patent rights can be found in the PATENTS file in the same directory.
 */

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@protocol MPTweakObserver;

/**
  @abstract Represents a possible value of a tweak.
  @discussion Should be able to be persisted in user defaults.
    For minimum and maximum values, should implement -compare:.
 */
typedef id MPTweakValue;

/**
  @abstract Represents a tweak
  @discussion A tweak contains a persistent, editable value.
 */
@interface MPTweak : NSObject

/**
  @abstract Creates a new tweak model.
  @discussion This is the designated initializer.
 */
- (instancetype)initWithName:(NSString *)name andEncoding:(NSString *)encoding;

/**
  @abstract This tweak's unique name.
  @discussion Used when reading and writing the tweak's value.
 */
@property (nonatomic, copy, readonly) NSString *name;

/**
 @abstract This tweak's value encoding, as returned by `@encoding`
 */
@property (nonatomic, copy, readonly) NSString *encoding;

/**
 @abstract The default value of the tweak.
 @discussion Use this when the current value is unset.
 */
@property (nonatomic, strong, readwrite) MPTweakValue defaultValue;

/**
  @abstract The current value of the tweak. Can be nil.
  @discussion Changes to this property will be propagated to disk.
 */
@property (nullable, nonatomic, strong, readwrite) MPTweakValue currentValue;

/**
  @abstract The minimum value of the tweak.
  @discussion Optional. If nil, there is no minimum.
 */
@property (nonatomic, strong, readwrite) MPTweakValue minimumValue;

/**
  @abstract The maximum value of the tweak.
  @discussion Optional. If nil, there is no maximum.
 */
@property (nonatomic, strong, readwrite) MPTweakValue maximumValue;

/**
  @abstract Adds an observer to the tweak.
  @param observer The observer. Must not be nil.
  @discussion A weak reference is taken on the observer.
 */
- (void)addObserver:(id<MPTweakObserver>)observer;

/**
  @abstract Removes an observer from the tweak.
  @param observer The observer to remove. Must not be nil.
  @discussion Optional, removing an observer isn't required.
 */
- (void)removeObserver:(id<MPTweakObserver>)observer;

@end

/**
  @abstract Responds to updates when a tweak changes.
 */
@protocol MPTweakObserver <NSObject>

/**
  @abstract Called when a tweak's value changes.
  @param tweak The tweak which changed in value.
 */
- (void)tweakDidChange:(MPTweak *)tweak;

@end

NS_ASSUME_NONNULL_END