RealmDocument.swift

//
//  Copyright © 2015 The CocoaBots. All rights reserved.

import Cocoa
import RealmSwift

enum RealmDocumentError: ErrorType {
    case FailedToConvertURLToFilePath
}

class RealmDocument: NSDocument {

    var representedRealm = Realm(inMemoryIdentifier: NSUUID().UUIDString)

    convenience init(contentsOfURL url: NSURL, ofType typeName: String) throws {
        self.init()

        do {
            try representedRealm = Realm(url: url)
        } catch {
            fatalError("Yeeeeeah, something went wrong creating the realm for \(url)")
        }
    }

    convenience init(forURL urlOrNil: NSURL?, withContentsOfURL contentsURL: NSURL, ofType typeName: String) throws {
        self.init()

        let originalRealm = try Realm(url: contentsURL, readOnly: true)

        if let url = urlOrNil, let path = url.path {
            try originalRealm.writeCopyToPath(path)
            representedRealm = try Realm(path: path)
        } else {
            let temporaryInMemoryRealmPath = NSTemporaryDirectory().stringByAppendingPathComponent(NSUUID().UUIDString)
            try originalRealm.writeCopyToPath(temporaryInMemoryRealmPath)
            representedRealm = try Realm(path: temporaryInMemoryRealmPath)
        }
    }

    deinit {
        // This is a workaround — ideally Realm would allow initialising an in-memory Realm based on an on-disk representation and this cleanup code would be unnecessary
        if representedRealm.path.hasPrefix(NSTemporaryDirectory()) {
            do {
                let fileManager = NSFileManager.defaultManager()
                try fileManager.removeItemAtPath(representedRealm.path)
            } catch let error as NSError {
                print("Error while deleting temporary Realm: \(error.localizedDescription)")
            }
        }
    }

    override func readFromURL(url: NSURL, ofType typeName: String) throws {
        if let proposedRealmPath = url.path {
            let currentRealmPath = representedRealm.path

            if currentRealmPath != proposedRealmPath {
                try representedRealm.writeCopyToPath(proposedRealmPath)
                representedRealm = try Realm(path: proposedRealmPath)

                let fileManager = NSFileManager.defaultManager()
                try fileManager.removeItemAtPath(currentRealmPath)
            }
        } else {
            throw RealmDocumentError.FailedToConvertURLToFilePath
        }
    }

    override func writeToURL(url: NSURL, ofType typeName: String) throws {
        if let filePath = url.path {
            try representedRealm.writeCopyToPath(filePath)
        } else {
            throw RealmDocumentError.FailedToConvertURLToFilePath
        }
    }

    override var documentEdited: Bool {
        return representedRealm.inWriteTransaction
    }
}

extension Realm {

    convenience init(url: NSURL, readOnly: Bool = false) throws {
        try self.init(path: url.path!, readOnly: readOnly)
    }

    var url: NSURL {
        return NSURL(fileURLWithPath: path, isDirectory: false)
    }

}

extension NSFileManager {

    func safelyCopyItemAtURL(srcURL:NSURL, toURL:NSURL, overwriteIfExists:Bool = false) throws {
        if overwriteIfExists {
            try trashItemAtURL(toURL, resultingItemURL: nil)
        }

        try copyItemAtURL(srcURL, toURL: toURL)
    }

    func safelyMoveItemAtURL(srcURL:NSURL, toURL:NSURL, overwriteIfExists:Bool = false) throws {
        if overwriteIfExists {
            try trashItemAtURL(toURL, resultingItemURL: nil)
        }

        try moveItemAtURL(srcURL, toURL: toURL)
    }
    
}