Category Archives: Techie

struct Book: Codable {
	let title: String
	let author: String
}

class BookRepository {
	func save(book: Book) {
    		let record = try! JSONEncoder().encode(book)
    		UserDefaults.standard.set(record, forKey: book.title)
	}
    
	func get(bookWithTitle title: String) -> Book? {
    		guard let data = UserDefaults.standard.data(forKey: title) else { return nil }
    		let book = try! JSONDecoder().decode(Book.self, from: data)
    		return book
	}
    
	func delete(book: Book) {
    		UserDefaults.standard.removeObject(forKey: book.title)
	}
}

let book = Book(title: "Fear and Loathing in COBOL", author: "Sir Edsger ZX Spectrum")
let repository = BookRepository()
repository.save(book: book)
print(repository.get(bookWithTitle: book.title)!)
repository.delete(book: book)
guard repository.get(bookWithTitle: book.title) == nil else {
	print("Error: can't delete Book from repository!")
	exit(1)
}

    typealias Item = Codable
    typealias ItemIdentifier = String
    
    func create<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier, item: T) async throws
    func read<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier) async throws -> T
    func update<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier, item: T) async throws
    func delete(id: CRUDRepository.ItemIdentifier) async throws
}

    private typealias RecordIdentifier = String
    
    let tableName: String
    let dataTransformer: DataTransformer
    
    init(
   	 tableName: String = "",
   	 dataTransformer: DataTransformer = JSONDataTransformer()
    ) {
   	 self.tableName = tableName
   	 self.dataTransformer = dataTransformer
    }
    
    private func key(id: CRUDRepository.ItemIdentifier) -> RecordIdentifier {
   	 "database_\(tableName)_item_\(id)"
    }
   	 
    private func isExists(id: CRUDRepository.ItemIdentifier) async throws -> Bool {
   	 UserDefaults.standard.data(forKey: key(id: id)) != nil
    }
    
    func create<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier, item: T) async throws {
   	 let data = try await dataTransformer.encode(item)
   	 UserDefaults.standard.set(data, forKey: key(id: id))
   	 UserDefaults.standard.synchronize()
    }
    
    func read<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier) async throws -> T {
   	 guard let data = UserDefaults.standard.data(forKey: key(id: id)) else {
   		 throw CRUDRepositoryError.recordNotFound(id: id)
   	 }
   	 let item: T = try await dataTransformer.decode(data: data)
   	 return item
    }
    
    func update<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier, item: T) async throws {
   	 guard try await isExists(id: id) else {
   		 throw CRUDRepositoryError.recordNotFound(id: id)
   	 }
   	 let data = try await dataTransformer.encode(item)
   	 UserDefaults.standard.set(data, forKey: key(id: id))
   	 UserDefaults.standard.synchronize()
    }
    
    func delete(id: CRUDRepository.ItemIdentifier) async throws {
   	 guard try await isExists(id: id) else {
   		 throw CRUDRepositoryError.recordNotFound(id: id)
   	 }
   	 UserDefaults.standard.removeObject(forKey: key(id: id))
   	 UserDefaults.standard.synchronize()
    }
}

	func encode<T: Encodable>(_ object: T) async throws -> Data
	func decode<T: Decodable>(data: Data) async throws -> T
}

	func encode<T>(_ object: T) async throws -> Data where T : Encodable {
    		let data = try JSONEncoder().encode(object)
    		return data
	}
    
	func decode<T>(data: Data) async throws -> T where T : Decodable {
    		let item: T = try JSONDecoder().decode(T.self, from: data)
    		return item
	}
}

print("One item access example")

do {
	let clientRecordIdentifier = "client"
	let clientOne = Client(name: "Chill Client")
	let repository = UserDefaultsRepository(
    	tableName: "Clients Database",
    	dataTransformer: JSONDataTransformer()
	)
	try await repository.create(id: clientRecordIdentifier, item: clientOne)
	var clientRecord: Client = try await repository.read(id: clientRecordIdentifier)
	print("Client Name: \(clientRecord.name)")
	clientRecord.name = "Busy Client"
	try await repository.update(id: clientRecordIdentifier, item: clientRecord)
	let updatedClient: Client = try await repository.read(id: clientRecordIdentifier)
	print("Updated Client Name: \(updatedClient.name)")
	try await repository.delete(id: clientRecordIdentifier)
	let removedClientRecord: Client = try await repository.read(id: clientRecordIdentifier)
	print(removedClientRecord)
}
catch {
	print(error.localizedDescription)
}

print("Array access example")

let clientArrayRecordIdentifier = "clientArray"
let clientOne = Client(name: "Chill Client")
let repository = UserDefaultsRepository(
	tableName: "Clients Database",
	dataTransformer: JSONDataTransformer()
)
let array = [clientOne]
try await repository.create(id: clientArrayRecordIdentifier, item: array)
let savedArray: [Client] = try await repository.read(id: clientArrayRecordIdentifier)
print(savedArray.first!)

class SQLiteRepository: CRUDRepository {
    private typealias RecordIdentifier = String
    
    let tableName: String
    let dataTransformer: DataTransformer
    private var db: OpaquePointer?

    init(
   	 tableName: String,
   	 dataTransformer: DataTransformer = JSONDataTransformer()
    ) {
   	 self.tableName = tableName
   	 self.dataTransformer = dataTransformer
   	 self.db = openDatabase()
   	 createTableIfNeeded()
    }
    
    private func openDatabase() -> OpaquePointer? {
   	 var db: OpaquePointer? = nil
   	 let fileURL = try! FileManager.default
   		 .url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
   		 .appendingPathComponent("\(tableName).sqlite")
   	 if sqlite3_open(fileURL.path, &db) != SQLITE_OK {
   		 print("error opening database")
   		 return nil
   	 }
   	 return db
    }
    
    private func createTableIfNeeded() {
   	 let createTableString = """
   	 CREATE TABLE IF NOT EXISTS \(tableName) (
   	 id TEXT PRIMARY KEY NOT NULL,
   	 data BLOB NOT NULL
   	 );
   	 """
   	 var createTableStatement: OpaquePointer? = nil
   	 if sqlite3_prepare_v2(db, createTableString, -1, &createTableStatement, nil) == SQLITE_OK {
   		 if sqlite3_step(createTableStatement) == SQLITE_DONE {
       		 print("\(tableName) table created.")
   		 } else {
       		 print("\(tableName) table could not be created.")
   		 }
   	 } else {
   		 print("CREATE TABLE statement could not be prepared.")
   	 }
   	 sqlite3_finalize(createTableStatement)
    }
    
    private func isExists(id: CRUDRepository.ItemIdentifier) async throws -> Bool {
   	 let queryStatementString = "SELECT data FROM \(tableName) WHERE id = ?;"
   	 var queryStatement: OpaquePointer? = nil
   	 if sqlite3_prepare_v2(db, queryStatementString, -1, &queryStatement, nil) == SQLITE_OK {
   		 sqlite3_bind_text(queryStatement, 1, id, -1, nil)
   		 if sqlite3_step(queryStatement) == SQLITE_ROW {
       		 sqlite3_finalize(queryStatement)
       		 return true
   		 } else {
       		 sqlite3_finalize(queryStatement)
       		 return false
   		 }
   	 } else {
   		 print("SELECT statement could not be prepared.")
   		 throw CRUDRepositoryError.databaseError
   	 }
    }
    
    func create<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier, item: T) async throws {
   	 let insertStatementString = "INSERT INTO \(tableName) (id, data) VALUES (?, ?);"
   	 var insertStatement: OpaquePointer? = nil
   	 if sqlite3_prepare_v2(db, insertStatementString, -1, &insertStatement, nil) == SQLITE_OK {
   		 let data = try await dataTransformer.encode(item)
   		 sqlite3_bind_text(insertStatement, 1, id, -1, nil)
   		 sqlite3_bind_blob(insertStatement, 2, (data as NSData).bytes, Int32(data.count), nil)
   		 if sqlite3_step(insertStatement) == SQLITE_DONE {
       		 print("Successfully inserted row.")
   		 } else {
       		 print("Could not insert row.")
       		 throw CRUDRepositoryError.databaseError
   		 }
   	 } else {
   		 print("INSERT statement could not be prepared.")
   		 throw CRUDRepositoryError.databaseError
   	 }
   	 sqlite3_finalize(insertStatement)
    }
    
    func read<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier) async throws -> T {
   	 let queryStatementString = "SELECT data FROM \(tableName) WHERE id = ?;"
   	 var queryStatement: OpaquePointer? = nil
   	 var item: T?
   	 if sqlite3_prepare_v2(db, queryStatementString, -1, &queryStatement, nil) == SQLITE_OK {
   		 sqlite3_bind_text(queryStatement, 1, id, -1, nil)
   		 if sqlite3_step(queryStatement) == SQLITE_ROW {
       		 let queryResultCol1 = sqlite3_column_blob(queryStatement, 0)
       		 let queryResultCol1Length = sqlite3_column_bytes(queryStatement, 0)
       		 let data = Data(bytes: queryResultCol1, count: Int(queryResultCol1Length))
       		 item = try await dataTransformer.decode(data: data)
   		 } else {
       		 throw CRUDRepositoryError.recordNotFound(id: id)
   		 }
   	 } else {
   		 print("SELECT statement could not be prepared")
   		 throw CRUDRepositoryError.databaseError
   	 }
   	 sqlite3_finalize(queryStatement)
   	 return item!
    }
    
    func update<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier, item: T) async throws {
   	 guard try await isExists(id: id) else {
   		 throw CRUDRepositoryError.recordNotFound(id: id)
   	 }
   	 let updateStatementString = "UPDATE \(tableName) SET data = ? WHERE id = ?;"
   	 var updateStatement: OpaquePointer? = nil
   	 if sqlite3_prepare_v2(db, updateStatementString, -1, &updateStatement, nil) == SQLITE_OK {
   		 let data = try await dataTransformer.encode(item)
   		 sqlite3_bind_blob(updateStatement, 1, (data as NSData).bytes, Int32(data.count), nil)
   		 sqlite3_bind_text(updateStatement, 2, id, -1, nil)
   		 if sqlite3_step(updateStatement) == SQLITE_DONE {
       		 print("Successfully updated row.")
   		 } else {
       		 print("Could not update row.")
       		 throw CRUDRepositoryError.databaseError
   		 }
   	 } else {
   		 print("UPDATE statement could not be prepared.")
   		 throw CRUDRepositoryError.databaseError
   	 }
   	 sqlite3_finalize(updateStatement)
    }
    
    func delete(id: CRUDRepository.ItemIdentifier) async throws {
   	 guard try await isExists(id: id) else {
   		 throw CRUDRepositoryError.recordNotFound(id: id)
   	 }
   	 let deleteStatementString = "DELETE FROM \(tableName) WHERE id = ?;"
   	 var deleteStatement: OpaquePointer? = nil
   	 if sqlite3_prepare_v2(db, deleteStatementString, -1, &deleteStatement, nil) == SQLITE_OK {
   		 sqlite3_bind_text(deleteStatement, 1, id, -1, nil)
   		 if sqlite3_step(deleteStatement) == SQLITE_DONE {
       		 print("Successfully deleted row.")
   		 } else {
       		 print("Could not delete row.")
       		 throw CRUDRepositoryError.databaseError
   		 }
   	 } else {
   		 print("DELETE statement could not be prepared.")
   		 throw CRUDRepositoryError.databaseError
   	 }
   	 sqlite3_finalize(deleteStatement)
    }
}

class FileSystemRepository: CRUDRepository {
	private typealias RecordIdentifier = String
    
	let directoryName: String
	let dataTransformer: DataTransformer
	private let fileManager = FileManager.default
	private var directoryURL: URL
    
	init(
    	directoryName: String = "Database",
    	dataTransformer: DataTransformer = JSONDataTransformer()
	) {
    	self.directoryName = directoryName
    	self.dataTransformer = dataTransformer
   	 
    	let paths = fileManager.urls(for: .documentDirectory, in: .userDomainMask)
    	directoryURL = paths.first!.appendingPathComponent(directoryName)
   	 
    	if !fileManager.fileExists(atPath: directoryURL.path) {
        	try? fileManager.createDirectory(at: directoryURL, withIntermediateDirectories: true, attributes: nil)
    	}
	}
    
	private func fileURL(id: CRUDRepository.ItemIdentifier) -> URL {
    	return directoryURL.appendingPathComponent("item_\(id).json")
	}
    
	private func isExists(id: CRUDRepository.ItemIdentifier) async throws -> Bool {
    	return fileManager.fileExists(atPath: fileURL(id: id).path)
	}
    
	func create<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier, item: T) async throws {
    	let data = try await dataTransformer.encode(item)
    	let url = fileURL(id: id)
    	try data.write(to: url)
	}
    
	func read<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier) async throws -> T {
    	let url = fileURL(id: id)
    	guard let data = fileManager.contents(atPath: url.path) else {
        	throw CRUDRepositoryError.recordNotFound(id: id)
    	}
    	let item: T = try await dataTransformer.decode(data: data)
    	return item
	}
    
	func update<T: CRUDRepository.Item>(id: CRUDRepository.ItemIdentifier, item: T) async throws {
    	guard try await isExists(id: id) else {
        	throw CRUDRepositoryError.recordNotFound(id: id)
    	}
    	let data = try await dataTransformer.encode(item)
    	let url = fileURL(id: id)
    	try data.write(to: url)
	}
    
	func delete(id: CRUDRepository.ItemIdentifier) async throws {
    	guard try await isExists(id: id) else {
        	throw CRUDRepositoryError.recordNotFound(id: id)
    	}
    	let url = fileURL(id: id)
    	try fileManager.removeItem(at: url)
	}
}

print("One item access example")

do {
	let clientRecordIdentifier = "client"
	let clientOne = Client(name: "Chill Client")
	let repository = FileSystemRepository(
    	directoryName: "Clients Database",
    	dataTransformer: JSONDataTransformer()
	)
	try await repository.create(id: clientRecordIdentifier, item: clientOne)
	var clientRecord: Client = try await repository.read(id: clientRecordIdentifier)
	print("Client Name: \(clientRecord.name)")
	clientRecord.name = "Busy Client"
	try await repository.update(id: clientRecordIdentifier, item: clientRecord)
	let updatedClient: Client = try await repository.read(id: clientRecordIdentifier)
	print("Updated Client Name: \(updatedClient.name)")
	try await repository.delete(id: clientRecordIdentifier)
	let removedClientRecord: Client = try await repository.read(id: clientRecordIdentifier)
	print(removedClientRecord)
}
catch {
	print(error.localizedDescription)
}

print("Array access example")

let clientArrayRecordIdentifier = "clientArray"
let clientOne = Client(name: "Chill Client")
let repository = FileSystemRepository(
	directoryName: "Clients Database",
	dataTransformer: JSONDataTransformer()
)
let array = [clientOne]
try await repository.create(id: clientArrayRecordIdentifier, item: array)
let savedArray: [Client] = try await repository.read(id: clientArrayRecordIdentifier)
print(savedArray.first!)

	let formatExtension = "xml"
    
	func encode<T: Encodable>(_ item: T) async throws -> Data {
    	let encoder = PropertyListEncoder()
    	encoder.outputFormat = .xml
    	return try encoder.encode(item)
	}
    
	func decode<T: Decodable>(data: Data) async throws -> T {
    	let decoder = PropertyListDecoder()
    	return try decoder.decode(T.self, from: data)
	}
}

print("One item access example")

do {
	let clientRecordIdentifier = "client"
	let clientOne = Client(name: "Chill Client")
	let repository = FileSystemRepository(
    	directoryName: "Clients Database",
    	dataTransformer: XMLDataTransformer()
	)
	try await repository.create(id: clientRecordIdentifier, item: clientOne)
	var clientRecord: Client = try await repository.read(id: clientRecordIdentifier)
	print("Client Name: \(clientRecord.name)")
	clientRecord.name = "Busy Client"
	try await repository.update(id: clientRecordIdentifier, item: clientRecord)
	let updatedClient: Client = try await repository.read(id: clientRecordIdentifier)
	print("Updated Client Name: \(updatedClient.name)")
	try await repository.delete(id: clientRecordIdentifier)
	let removedClientRecord: Client = try await repository.read(id: clientRecordIdentifier)
	print(removedClientRecord)
}
catch {
	print(error.localizedDescription)
}

print("Array access example")

let clientArrayRecordIdentifier = "clientArray"
let clientOne = Client(name: "Chill Client")
let repository = FileSystemRepository(
	directoryName: "Clients Database",
	dataTransformer: XMLDataTransformer()
)
let array = [clientOne]
try await repository.create(id: clientArrayRecordIdentifier, item: array)
let savedArray: [Client] = try await repository.read(id: clientArrayRecordIdentifier)
print(savedArray.first!)