#import <Foundation/Foundation.h>

#import "MGLOfflineRegion.h"

NS_ASSUME_NONNULL_BEGIN

/**
 The state an offline pack is currently in.
 */
typedef NS_ENUM (NSInteger, MGLOfflinePackState) {
    /**
     It is unknown whether the pack is inactive, active, or complete.
     
     This is the initial state of a pack. The state of a pack becomes known by
     the time the shared `MGLOfflineStorage` object sends the first
     `MGLOfflinePackProgressChangedNotification` about the pack. For inactive
     packs, you must explicitly request a progress update using the
     `-[MGLOfflinePack requestProgress]` method.
     
     An invalid pack always has a state of `MGLOfflinePackStateInvalid`, never
     `MGLOfflinePackStateUnknown`.
     */
    MGLOfflinePackStateUnknown = 0,
    /**
     The pack is incomplete and is not currently downloading.
     
     This is the initial state of a pack that is created using the
     `-[MGLOfflinePack addPackForRegion:withContext:completionHandler:]` method,
     as well as after the `-[MGLOfflinePack suspend]` method is
     called.
     */
    MGLOfflinePackStateInactive = 1,
    /**
     The pack is incomplete and is currently downloading.
     
     This is the state of a pack after the `-[MGLOfflinePack resume]` method is
     called.
     */
    MGLOfflinePackStateActive = 2,
    /**
     The pack has downloaded to completion.
     */
    MGLOfflinePackStateComplete = 3,
    /**
     The pack has been removed using the
     `-[MGLOfflineStorage removePack:withCompletionHandler:]` method. Sending
     any message to the pack will raise an exception.
     */
    MGLOfflinePackStateInvalid = 4,
};

/**
 A structure containing information about an offline pack’s current download
 progress.
 */
typedef struct MGLOfflinePackProgress {
    /**
     The number of resources that have been completely downloaded and are ready
     to use offline.
     */
    uint64_t countOfResourcesCompleted;
    /**
     The cumulative size of the downloaded resources (inclusive of tiles) on disk, measured in bytes.
     */
    uint64_t countOfBytesCompleted;
    /**
     The cumulative size of the downloaded tiles on disk, measured in bytes.
     */
    uint64_t countOfTileBytesCompleted;
    /**
     The minimum number of resources that must be downloaded in order to view
     the pack’s full region without any omissions.
     
     At the beginning of a download, this count is a lower bound; the number of
     expected resources may increase as the download progresses.
     */
    uint64_t countOfResourcesExpected;
    /**
     The maximum number of resources that must be downloaded in order to view
     the pack’s full region without any omissions.
     
     At the beginning of a download, when the exact number of required resources
     is unknown, this field is set to `UINT64_MAX`. Thus this count is always an
     upper bound.
     */
    uint64_t maximumResourcesExpected;
} MGLOfflinePackProgress;

/**
 An `MGLOfflinePack` represents a collection of resources necessary for viewing
 a region offline to a local database.
 
 To create an instance of `MGLOfflinePack`, use the
 `+[MGLOfflineStorage addPackForRegion:withContext:completionHandler:]` method.
 A pack created using `-[MGLOfflinePack init]` is immediately invalid.
 */
@interface MGLOfflinePack : NSObject

/**
 The region for which the pack manages resources.
 */
@property (nonatomic, readonly) id <MGLOfflineRegion> region;

/**
 Arbitrary data stored alongside the downloaded resources.
 
 The context typically holds application-specific information for identifying
 the pack, such as a user-selected name.
 */
@property (nonatomic, readonly) NSData *context;

/**
 The pack’s current state.
 
 The state of an inactive or completed pack is computed lazily and is set to
 `MGLOfflinePackStateUnknown` by default. To request the pack’s status, use the
 `-requestProgress` method. To get notified when the state becomes known and
 when it changes, observe KVO change notifications on this pack’s `state` key
 path. Alternatively, you can add an observer for
 `MGLOfflinePackProgressChangedNotification`s about this pack that come from the
 default notification center.
 */
@property (nonatomic, readonly) MGLOfflinePackState state;

/**
 The pack’s current progress.
 
 The progress of an inactive or completed pack is computed lazily, and all its
 fields are set to 0 by default. To request the pack’s progress, use the
 `-requestProgress` method. To get notified when the progress becomes
 known and when it changes, observe KVO change notifications on this pack’s
 `state` key path. Alternatively, you can add an observer for
 `MGLOfflinePackProgressChangedNotification`s about this pack that come from the
 default notification center.
 */
@property (nonatomic, readonly) MGLOfflinePackProgress progress;

/**
 Resumes downloading if the pack is inactive.
 
 A pack resumes asynchronously. To get notified when this pack resumes, observe
 KVO change notifications on this pack’s `state` key path. Alternatively, you
 can add an observer for `MGLOfflinePackProgressChangedNotification`s about this
 pack that come from the default notification center.
 
 When a pack resumes after being suspended, it may begin by iterating over the
 already downloaded resources. As a result, the `progress` structure’s
 `countOfResourcesCompleted` field may revert to 0 before rapidly returning to
 the level of progress at the time the pack was suspended.
 
 To temporarily suspend downloading, call the `-suspend` method.
 */
- (void)resume;

/**
 Temporarily stops downloading if the pack is active.
 
 A pack suspends asynchronously. To get notified when this pack resumes, observe
 KVO change notifications on this pack’s `state` key path. Alternatively, you
 can add an observer for `MGLOfflinePackProgressChangedNotification` about this
 pack that come from the default notification center.
 
 If the pack previously reached a higher level of progress before being
 suspended, it may wait to suspend until it returns to that level.
 
 To resume downloading, call the `-resume` method.
 */
- (void)suspend;

/**
 Request an asynchronous update to the pack’s `state` and `progress` properties.
 
 The state and progress of an inactive or completed pack are computed lazily. If
 you need the state or progress of a pack whose `state` property is currently
 set to `MGLOfflinePackStateUnknown`, observe KVO change notifications on this
 pack’s `state` key path, then call this method. Alternatively, you can add an
 observer for `MGLOfflinePackProgressChangedNotification` about this pack that
 come from the default notification center.
 */
- (void)requestProgress;

@end

NS_ASSUME_NONNULL_END