//
//  ListObserver.swift
//  CoreStore
//
//  Copyright © 2018 John Rommel Estropia
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all
//  copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
//  SOFTWARE.
//

import Foundation
import CoreData


// MARK: - ListObserver

/**
 Implement the `ListObserver` protocol to observe changes to a list of `NSManagedObject`s. `ListObserver`s may register themselves to a `ListMonitor`'s `addObserver(_:)` method:
 ```
 let monitor = dataStack.monitorList(
     From<Person>(),
     OrderBy(.ascending("lastName"))
 )
 monitor.addObserver(self)
 ```
 */
public protocol ListObserver: AnyObject {
    
    /**
     The `NSManagedObject` type for the observed list
     */
    associatedtype ListEntityType: DynamicObject
    
    /**
     Handles processing just before a change to the observed list occurs. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter sourceIdentifier: an optional identifier provided by the transaction source
     */
    func listMonitorWillChange(
        _ monitor: ListMonitor<ListEntityType>,
        sourceIdentifier: Any?
    )
    
    /**
     Handles processing just before a change to the observed list occurs. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     */
    func listMonitorWillChange(
        _ monitor: ListMonitor<ListEntityType>
    )
    
    /**
     Handles processing right after a change to the observed list occurs. (Required)
     
     - parameter monitor: the `ListMonitor` monitoring the object being observed
     - parameter sourceIdentifier: an optional identifier provided by the transaction source
     */
    func listMonitorDidChange(
        _ monitor: ListMonitor<ListEntityType>,
        sourceIdentifier: Any?
    )
    
    /**
     Handles processing right after a change to the observed list occurs. (Required)
     
     - parameter monitor: the `ListMonitor` monitoring the object being observed
     */
    func listMonitorDidChange(
        _ monitor: ListMonitor<ListEntityType>
    )
    
    /**
     This method is broadcast from within the `ListMonitor`'s `refetch(...)` method to let observers prepare for the internal `NSFetchedResultsController`'s pending change to its predicate, sort descriptors, etc. (Optional)
     
     - Important: All `ListMonitor` access between `listMonitorWillRefetch(_:)` and `listMonitorDidRefetch(_:)` will raise and assertion. The actual refetch will happen after the `NSFetchedResultsController`'s last `controllerDidChangeContent(_:)` notification completes.
     - parameter monitor: the `ListMonitor` monitoring the object being observed
     - parameter sourceIdentifier: an optional identifier provided by the transaction source
     */
    func listMonitorWillRefetch(
        _ monitor: ListMonitor<ListEntityType>,
        sourceIdentifier: Any?
    )
    
    /**
     This method is broadcast from within the `ListMonitor`'s `refetch(...)` method to let observers prepare for the internal `NSFetchedResultsController`'s pending change to its predicate, sort descriptors, etc. (Optional)
     
     - Important: All `ListMonitor` access between `listMonitorWillRefetch(_:)` and `listMonitorDidRefetch(_:)` will raise and assertion. The actual refetch will happen after the `NSFetchedResultsController`'s last `controllerDidChangeContent(_:)` notification completes.
     - parameter monitor: the `ListMonitor` monitoring the object being observed
     */
    func listMonitorWillRefetch(
        _ monitor: ListMonitor<ListEntityType>
    )
    
    /**
     After the `ListMonitor`'s `refetch(...)` method is called, this method is broadcast after the `NSFetchedResultsController`'s last `controllerDidChangeContent(_:)` notification completes. (Required)
     
     - Important: When `listMonitorDidRefetch(_:)` is called it should be assumed that all `ListMonitor`'s previous data have been reset, including counts, objects, and persistent stores.
     - parameter monitor: the `ListMonitor` monitoring the object being observed
     - parameter sourceIdentifier: an optional identifier provided by the transaction source
     */
    func listMonitorDidRefetch(
        _ monitor: ListMonitor<ListEntityType>,
        sourceIdentifier: Any?
    )
    
    /**
     After the `ListMonitor`'s `refetch(...)` method is called, this method is broadcast after the `NSFetchedResultsController`'s last `controllerDidChangeContent(_:)` notification completes. (Required)
     
     - Important: When `listMonitorDidRefetch(_:)` is called it should be assumed that all `ListMonitor`'s previous data have been reset, including counts, objects, and persistent stores.
     - parameter monitor: the `ListMonitor` monitoring the object being observed
     */
    func listMonitorDidRefetch(
        _ monitor: ListMonitor<ListEntityType>
    )
}


// MARK: - ListObserver (Default Implementations)

extension ListObserver {
    
    public func listMonitorWillChange(
        _ monitor: ListMonitor<ListEntityType>,
        sourceIdentifier: Any?
    ) {
        
        self.listMonitorWillChange(monitor)
    }
    
    public func listMonitorWillChange(
        _ monitor: ListMonitor<ListEntityType>
    ) {}
    
    public func listMonitorDidChange(
        _ monitor: ListMonitor<ListEntityType>,
        sourceIdentifier: Any?
    ) {
        
        self.listMonitorDidChange(monitor)
    }
    
    public func listMonitorWillRefetch(
        _ monitor: ListMonitor<ListEntityType>,
        sourceIdentifier: Any?
    ) {
        
        self.listMonitorWillRefetch(monitor)
    }
    
    public func listMonitorWillRefetch(
        _ monitor: ListMonitor<ListEntityType>
    ) {}
    
    public func listMonitorDidRefetch(
        _ monitor: ListMonitor<ListEntityType>,
        sourceIdentifier: Any?
    ) {
        
        self.listMonitorDidRefetch(monitor)
    }
}


// MARK: - ListObjectObserver

/**
 Implement the `ListObjectObserver` protocol to observe detailed changes to a list's object. `ListObjectObserver`s may register themselves to a `ListMonitor`'s `addObserver(_:)` method:
 ```
 let monitor = dataStack.monitorList(
     From<MyPersonEntity>(),
     OrderBy(.ascending("lastName"))
 )
 monitor.addObserver(self)
 ```
 */
public protocol ListObjectObserver: ListObserver {
    
    /**
     Notifies that an object was inserted to the specified `NSIndexPath` in the list. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter object: the entity type for the inserted object
     - parameter indexPath: the new `NSIndexPath` for the inserted object
     - parameter sourceIdentifier: an optional identifier provided by the transaction source
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didInsertObject object: ListEntityType,
        toIndexPath indexPath: IndexPath,
        sourceIdentifier: Any?
    )
    
    /**
     Notifies that an object was inserted to the specified `NSIndexPath` in the list. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter object: the entity type for the inserted object
     - parameter indexPath: the new `NSIndexPath` for the inserted object
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didInsertObject object: ListEntityType,
        toIndexPath indexPath: IndexPath
    )
    
    /**
     Notifies that an object was deleted from the specified `NSIndexPath` in the list. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter object: the entity type for the deleted object
     - parameter indexPath: the `NSIndexPath` for the deleted object
     - parameter sourceIdentifier: an optional identifier provided by the transaction source
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didDeleteObject object: ListEntityType,
        fromIndexPath indexPath: IndexPath,
        sourceIdentifier: Any?
    )
    
    /**
     Notifies that an object was deleted from the specified `NSIndexPath` in the list. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter object: the entity type for the deleted object
     - parameter indexPath: the `NSIndexPath` for the deleted object
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didDeleteObject object: ListEntityType,
        fromIndexPath indexPath: IndexPath
    )
    
    /**
     Notifies that an object at the specified `NSIndexPath` was updated. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter object: the entity type for the updated object
     - parameter indexPath: the `NSIndexPath` for the updated object
     - parameter sourceIdentifier: an optional identifier provided by the transaction source
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didUpdateObject object: ListEntityType,
        atIndexPath indexPath: IndexPath,
        sourceIdentifier: Any?
    )
    
    /**
     Notifies that an object at the specified `NSIndexPath` was updated. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter object: the entity type for the updated object
     - parameter indexPath: the `NSIndexPath` for the updated object
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didUpdateObject object: ListEntityType,
        atIndexPath indexPath: IndexPath
    )
    
    /**
     Notifies that an object's index changed. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter object: the entity type for the moved object
     - parameter fromIndexPath: the previous `NSIndexPath` for the moved object
     - parameter toIndexPath: the new `NSIndexPath` for the moved object
     - parameter sourceIdentifier: an optional identifier provided by the transaction source
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didMoveObject object: ListEntityType,
        fromIndexPath: IndexPath,
        toIndexPath: IndexPath,
        sourceIdentifier: Any?
    )
    
    /**
     Notifies that an object's index changed. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter object: the entity type for the moved object
     - parameter fromIndexPath: the previous `NSIndexPath` for the moved object
     - parameter toIndexPath: the new `NSIndexPath` for the moved object
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didMoveObject object: ListEntityType,
        fromIndexPath: IndexPath,
        toIndexPath: IndexPath
    )
}


// MARK: - ListObjectObserver (Default Implementations)

extension ListObjectObserver {
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didInsertObject object: ListEntityType,
        toIndexPath indexPath: IndexPath,
        sourceIdentifier: Any?
    ) {
        
        self.listMonitor(
            monitor,
            didInsertObject: object,
            toIndexPath: indexPath
        )
    }
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didInsertObject object: ListEntityType,
        toIndexPath indexPath: IndexPath
    ) {}
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didDeleteObject object: ListEntityType,
        fromIndexPath indexPath: IndexPath,
        sourceIdentifier: Any?
    ) {
        
        self.listMonitor(
            monitor,
            didDeleteObject: object,
            fromIndexPath: indexPath
        )
    }
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didDeleteObject object: ListEntityType,
        fromIndexPath indexPath: IndexPath
    ) {}
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didUpdateObject object: ListEntityType,
        atIndexPath indexPath: IndexPath,
        sourceIdentifier: Any?
    ) {
        
        self.listMonitor(
            monitor,
            didUpdateObject: object,
            atIndexPath: indexPath
        )
    }
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didUpdateObject object: ListEntityType,
        atIndexPath indexPath: IndexPath
    ) {}
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didMoveObject object: ListEntityType,
        fromIndexPath: IndexPath,
        toIndexPath: IndexPath,
        sourceIdentifier: Any?
    ) {
        
        self.listMonitor(
            monitor,
            didMoveObject: object,
            fromIndexPath: fromIndexPath,
            toIndexPath: toIndexPath
        )
    }
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didMoveObject object: ListEntityType,
        fromIndexPath: IndexPath,
        toIndexPath: IndexPath
    ) {}
}


// MARK: - ListSectionObserver

/**
 Implement the `ListSectionObserver` protocol to observe changes to a list's section info. `ListSectionObserver`s may register themselves to a `ListMonitor`'s `addObserver(_:)` method:
 ```
 let monitor = dataStack.monitorSectionedList(
     From<MyPersonEntity>(),
     SectionBy("age") { "Age \($0)" },
     OrderBy(.ascending("lastName"))
 )
 monitor.addObserver(self)
 ```
 */
public protocol ListSectionObserver: ListObjectObserver {
    
    /**
     Notifies that a section was inserted at the specified index. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter sectionInfo: the `NSFetchedResultsSectionInfo` for the inserted section
     - parameter sectionIndex: the new section index for the new section
     - parameter sourceIdentifier: an optional identifier provided by the transaction source
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didInsertSection sectionInfo: NSFetchedResultsSectionInfo,
        toSectionIndex sectionIndex: Int,
        sourceIdentifier: Any?
    )
    
    /**
     Notifies that a section was inserted at the specified index. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter sectionInfo: the `NSFetchedResultsSectionInfo` for the inserted section
     - parameter sectionIndex: the new section index for the new section
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didInsertSection sectionInfo: NSFetchedResultsSectionInfo,
        toSectionIndex sectionIndex: Int
    )
    
    /**
     Notifies that a section was inserted at the specified index. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter sectionInfo: the `NSFetchedResultsSectionInfo` for the deleted section
     - parameter sectionIndex: the previous section index for the deleted section
     - parameter sourceIdentifier: an optional identifier provided by the transaction source
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didDeleteSection sectionInfo: NSFetchedResultsSectionInfo,
        fromSectionIndex sectionIndex: Int,
        sourceIdentifier: Any?
    )
    
    /**
     Notifies that a section was inserted at the specified index. (Optional)
     The default implementation does nothing.
     
     - parameter monitor: the `ListMonitor` monitoring the list being observed
     - parameter sectionInfo: the `NSFetchedResultsSectionInfo` for the deleted section
     - parameter sectionIndex: the previous section index for the deleted section
     */
    func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didDeleteSection sectionInfo: NSFetchedResultsSectionInfo,
        fromSectionIndex sectionIndex: Int
    )
}


// MARK: - ListSectionObserver (Default Implementations)

extension ListSectionObserver {
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didInsertSection sectionInfo: NSFetchedResultsSectionInfo,
        toSectionIndex sectionIndex: Int,
        sourceIdentifier: Any?
    ) {
        
        self.listMonitor(
            monitor,
            didInsertSection: sectionInfo,
            toSectionIndex: sectionIndex
        )
    }
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didInsertSection sectionInfo: NSFetchedResultsSectionInfo,
        toSectionIndex sectionIndex: Int
    ) {}
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didDeleteSection sectionInfo: NSFetchedResultsSectionInfo,
        fromSectionIndex sectionIndex: Int,
        sourceIdentifier: Any?
    ) {
        
        self.listMonitor(
            monitor,
            didDeleteSection: sectionInfo,
            fromSectionIndex: sectionIndex
        )
    }
    
    public func listMonitor(
        _ monitor: ListMonitor<ListEntityType>,
        didDeleteSection sectionInfo: NSFetchedResultsSectionInfo,
        fromSectionIndex sectionIndex: Int
    ) {}
}