SwiftLogger/Logger/Loggers/DiskLogger/FileWriter.swift

//
// MIT License
//
// Copyright (c) 2018 Wojciech Nagrodzki
//
// 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

protocol File {
    func seekToEndOfFile() -> UInt64
    func swift_write(_ data: Data) throws
    func synchronizeFile()
    func closeFile()
}

protocol FileFactory {
    func makeInstance(forWritingTo: URL) throws -> File
}

/// Allows writing to a file while respecting allowed size limit.
final class FileWriter {
    
    private let file: File
    private let sizeLimit: UInt64
    private var currentSize: UInt64
    
    /// Initializes new FileWriter instance.
    ///
    /// - Parameters:
    ///   - fileURL: URL of the file.
    ///   - fileSizeLimit: Maximum size the file can reach in bytes.
    /// - Throws: An error that may occur while the file is being opened for writing.
    init(fileURL: URL, fileSizeLimit: UInt64, fileFactory: FileFactory) throws {
        file = try fileFactory.makeInstance(forWritingTo: fileURL)
        self.sizeLimit = fileSizeLimit
        currentSize = file.seekToEndOfFile()
    }
}

extension FileWriter: SizeLimitedFile {
    
    func write(_ data: Data) throws {
        let dataSize = UInt64(data.count)
        guard currentSize + dataSize <= sizeLimit else {
            throw SizeLimitedFileQuotaReached()
        }
        try file.swift_write(data)
        currentSize += dataSize
    }
    
    func synchronizeAndCloseFile() {
        file.synchronizeFile()
        file.closeFile()
    }
}