CoreStore/Sources/XcodeDataModelSchema.swift

//
//  XcodeDataModelSchema.swift
//  CoreStore
//
//  Copyright © 2017 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 CoreData
import Foundation


// MARK: - XcodeDataModelSchema

/**
 The `XcodeDataModelSchema` describes a model version declared in a single *.xcdatamodeld file.
 ```
 CoreStore.defaultStack = DataStack(
     XcodeDataModelSchema(modelName: "MyAppV1", bundle: .main)
 )
 ```
 */
public final class XcodeDataModelSchema: DynamicSchema {
    
    /**
     Initializes an `XcodeDataModelSchema` from an *.xcdatamodeld version name and its containing `Bundle`.
     ```
     CoreStore.defaultStack = DataStack(
         XcodeDataModelSchema(modelName: "MyAppV1", bundle: .main)
     )
     ```
     - parameter modelName: the model version, typically the file name of an *.xcdatamodeld file (without the file extension)
     - parameter bundle: the `Bundle` that contains the .xcdatamodeld's "momd" file. If not specified, the `Bundle.main` will be searched.
     */
    public convenience init(modelName: ModelVersion, bundle: Bundle = Bundle.main) {
        
        guard let modelFilePath = bundle.path(forResource: modelName, ofType: "momd") else {
            
            // For users migrating from very old Xcode versions: Old xcdatamodel files are not contained inside xcdatamodeld (with a "d"), and will thus fail this check. If that was the case, create a new xcdatamodeld file and copy all contents into the new model.
            let foundModels = bundle
                .paths(forResourcesOfType: "momd", inDirectory: nil)
                .map({ ($0 as NSString).lastPathComponent })
            CoreStore.abort("Could not find \"\(modelName).momd\" from the bundle \"\(bundle.bundleIdentifier ?? "<nil>")\". Other model files in bundle: \(foundModels.coreStoreDumpString)")
        }
        
        let modelFileURL = URL(fileURLWithPath: modelFilePath)
        let fileURL = modelFileURL.appendingPathComponent("\(modelName).mom", isDirectory: false)
        self.init(modelName: modelName, modelVersionFileURL: fileURL)
    }
    
    /**
     Initializes an `XcodeDataModelSchema` from an *.xcdatamodeld file URL.
     ```
     CoreStore.defaultStack = DataStack(
         XcodeDataModelSchema(modelName: "MyAppV1", modelVersionFileURL: fileURL)
     )
     ```
     - parameter modelName: the model version, typically the file name of an *.xcdatamodeld file (without the file extension)
     - parameter modelVersionFileURL: the file URL that points to the .xcdatamodeld's "momd" file.
     */
    public required init(modelName: ModelVersion, modelVersionFileURL: URL) {
        
        CoreStore.assert(
            NSManagedObjectModel(contentsOf: modelVersionFileURL) != nil,
            "Could not find the \"\(modelName).mom\" version file for the model at URL \"\(modelVersionFileURL)\"."
        )
        
        self.modelVersion = modelName
        self.modelVersionFileURL = modelVersionFileURL
    }
    
    
    // MARK: DynamicSchema
    
    public let modelVersion: ModelVersion
    
    public func rawModel() -> NSManagedObjectModel {
    
        if let cachedRawModel = self.cachedRawModel {
            
            return cachedRawModel
        }
        if let rawModel = NSManagedObjectModel(contentsOf: self.modelVersionFileURL) {
            
            self.cachedRawModel = rawModel
            return rawModel
        }
        CoreStore.abort("Could not create an \(cs_typeName(NSManagedObjectModel.self)) from the model at URL \"\(self.modelVersionFileURL)\".")
    }
    
    
    // MARK: Internal
    
    internal let modelVersionFileURL: URL
    
    private lazy var rootModelFileURL: URL = cs_lazy { [unowned self] in
     
        return self.modelVersionFileURL.deletingLastPathComponent()
    }
    
    
    // MARK: Private
    
    private weak var cachedRawModel: NSManagedObjectModel?
}