CoreStore/Sources/CoreStoreFetchedResultsController.swift

//
//  CoreStoreFetchedResultsController.swift
//  CoreStore
//
//  Copyright © 2016 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: - CoreStoreFetchedResultsController

@available(OSX 10.12, *)
internal final class CoreStoreFetchedResultsController: NSFetchedResultsController<NSManagedObject> {
    
    // MARK: Internal
    
    @nonobjc
    internal convenience init<T: DynamicObject>(dataStack: DataStack, fetchRequest: NSFetchRequest<NSManagedObject>, from: From<T>?, sectionBy: SectionBy? = nil, applyFetchClauses: @escaping (_ fetchRequest: NSFetchRequest<NSManagedObject>) -> Void) {
        
        self.init(
            context: dataStack.mainContext,
            fetchRequest: fetchRequest,
            from: from,
            sectionBy: sectionBy,
            applyFetchClauses: applyFetchClauses
        )
    }
    
    @nonobjc
    internal init<T: DynamicObject>(context: NSManagedObjectContext, fetchRequest: NSFetchRequest<NSManagedObject>, from: From<T>?, sectionBy: SectionBy? = nil, applyFetchClauses: @escaping (_ fetchRequest: NSFetchRequest<NSManagedObject>) -> Void) {
        
        _ = from?.applyToFetchRequest(
            fetchRequest,
            context: context,
            applyAffectedStores: false
        )
        applyFetchClauses(fetchRequest)
        
        if let from = from {
            
            self.reapplyAffectedStores = { fetchRequest, context in
                
                return from.applyAffectedStoresForFetchedRequest(fetchRequest, context: context)
            }
        }
        else {
            
            guard let from = (fetchRequest.entity.flatMap { $0.managedObjectClassName }).flatMap(NSClassFromString).flatMap({ From<T>($0 as! T.Type) }) else {
                
                CoreStore.abort("Attempted to create a \(CoreStoreFetchedResultsController.self) without a \(cs_typeName(From<T>.self)) clause or an \(cs_typeName(NSEntityDescription.self)).")
            }
            
            self.reapplyAffectedStores = { fetchRequest, context in
                
                return from.applyAffectedStoresForFetchedRequest(fetchRequest, context: context)
            }
        }
        
        super.init(
            fetchRequest: fetchRequest,
            managedObjectContext: context,
            sectionNameKeyPath: sectionBy?.sectionKeyPath,
            cacheName: nil
        )
    }
    
    @nonobjc
    internal func performFetchFromSpecifiedStores() throws {
        
        if !self.reapplyAffectedStores(self.fetchRequest, self.managedObjectContext) {
            
            CoreStore.log(
                .warning,
                message: "Attempted to perform a fetch on an \(cs_typeName(self)) but could not find any persistent store for the entity \(cs_typeName(self.fetchRequest.entityName))"
            )
        }
        try self.performFetch()
    }
    
    @nonobjc
    internal func dynamicCast<U: NSFetchRequestResult>() -> NSFetchedResultsController<U> {
        
        return unsafeBitCast(self, to: NSFetchedResultsController<U>.self)
    }
    
    deinit {
        
        self.delegate = nil
    }
    
    
    // MARK: Private
    
    @nonobjc
    private let reapplyAffectedStores: (_ fetchRequest: NSFetchRequest<NSManagedObject>, _ context: NSManagedObjectContext) -> Bool
}