//
//  OBSMTLModel+NSCoding.h
//  Mantle
//
//  Created by Justin Spahr-Summers on 2013-02-12.
//  Copyright (c) 2013 GitHub. All rights reserved.
//
#import "OBSMTLModel.h"

/// Defines how a OBSMTLModel property key should be encoded into an archive.
///
/// OBSMTLModelEncodingBehaviorExcluded      - The property should never be encoded.
/// OBSMTLModelEncodingBehaviorUnconditional - The property should always be
///                                         encoded.
/// OBSMTLModelEncodingBehaviorConditional   - The object should be encoded only
///                                         if unconditionally encoded elsewhere.
///                                         This should only be used for object
///                                         properties.
typedef enum : NSUInteger {
    OBSMTLModelEncodingBehaviorExcluded = 0,
    OBSMTLModelEncodingBehaviorUnconditional,
    OBSMTLModelEncodingBehaviorConditional,
} OBSMTLModelEncodingBehavior;

/// Implements default archiving and unarchiving behaviors for OBSMTLModel.
@interface OBSMTLModel (NSCoding) <NSCoding>

/// Initializes the receiver from an archive.
///
/// This will decode the original +modelVersion of the archived object, then
/// invoke -decodeValueForKey:withCoder:modelVersion: for each of the receiver's
/// +propertyKeys.
///
/// Returns an initialized model object, or nil if a decoding error occurred.
- (id)initWithCoder:(NSCoder *)coder;

/// Archives the receiver using the given coder.
///
/// This will encode the receiver's +modelVersion, then the receiver's properties
/// according to the behaviors specified in +encodingBehaviorsByPropertyKey.
- (void)encodeWithCoder:(NSCoder *)coder;

/// Determines how the +propertyKeys of the class are encoded into an archive.
/// The values of this dictionary should be boxed OBSMTLModelEncodingBehavior
/// values.
///
/// Any keys not present in the dictionary will be excluded from the archive.
///
/// Subclasses overriding this method should combine their values with those of
/// `super`.
///
/// Returns a dictionary mapping the receiver's +propertyKeys to default encoding
/// behaviors. If a property is an object with `weak` semantics, the default
/// behavior is OBSMTLModelEncodingBehaviorConditional; otherwise, the default is
/// OBSMTLModelEncodingBehaviorUnconditional.
+ (NSDictionary *)encodingBehaviorsByPropertyKey;

/// Determines the classes that are allowed to be decoded for each of the
/// receiver's properties when using <NSSecureCoding>. The values of this
/// dictionary should be NSArrays of Class objects.
///
/// If any encodable keys (as determined by +encodingBehaviorsByPropertyKey) are
/// not present in the dictionary, an exception will be thrown during secure
/// encoding or decoding.
///
/// Subclasses overriding this method should combine their values with those of
/// `super`.
///
/// Returns a dictionary mapping the receiver's encodable keys (as determined by
/// +encodingBehaviorsByPropertyKey) to default allowed classes, based on the
/// type that each property is declared as. If type of an encodable property
/// cannot be determined (e.g., it is declared as `id`), it will be omitted from
/// the dictionary, and subclasses must provide a valid value to prevent an
/// exception being thrown during encoding/decoding.
+ (NSDictionary *)allowedSecureCodingClassesByPropertyKey;

/// Decodes the value of the given property key from an archive.
///
/// By default, this method looks for a `-decode<Key>WithCoder:modelVersion:`
/// method on the receiver, and invokes it if found.
///
/// If the custom method is not implemented and `coder` does not require secure
/// coding, `-[NSCoder decodeObjectForKey:]` will be invoked with the given
/// `key`.
///
/// If the custom method is not implemented and `coder` requires secure coding,
/// `-[NSCoder decodeObjectOfClasses:forKey:]` will be invoked with the
/// information from +allowedSecureCodingClassesByPropertyKey and the given `key`. The
/// receiver must conform to <NSSecureCoding> for this to work correctly.
///
/// key          - The property key to decode the value for. This argument cannot
///                be nil.
/// coder        - The NSCoder representing the archive being decoded. This
///                argument cannot be nil.
/// modelVersion - The version of the original model object that was encoded.
///
/// Returns the decoded and boxed value, or nil if the key was not present.
- (id)decodeValueForKey:(NSString *)key withCoder:(NSCoder *)coder modelVersion:(NSUInteger)modelVersion;

/// The version of this OBSMTLModel subclass.
///
/// This version number is saved in archives so that later model changes can be
/// made backwards-compatible with old versions.
///
/// Subclasses should override this method to return a higher version number
/// whenever a breaking change is made to the model.
///
/// Returns 0.
+ (NSUInteger)modelVersion;

@end

/// This method must be overridden to support archives created by older versions
/// of Mantle (before the `OBSMTLModel+NSCoding` interface existed).
@interface OBSMTLModel (OldArchiveSupport)

/// Converts an archived external representation to a dictionary suitable for
/// passing to -initWithDictionary:.
///
/// externalRepresentation - The decoded external representation of the receiver.
/// fromVersion            - The model version at the time the external
///                          representation was encoded.
///
/// Returns nil by default, indicating that conversion failed.
+ (NSDictionary *)dictionaryValueFromArchivedExternalRepresentation:(NSDictionary *)externalRepresentation version:(NSUInteger)fromVersion;

@end
