/**
 * Tae Won Ha - http://taewon.de - @hataewon
 * See LICENSE
 */

import Foundation

fileprivate class FileAppender {

  init(with fileUrl: URL) {
    guard fileUrl.isFileURL else {
      preconditionFailure("\(fileUrl) must be a file URL!")
    }

    self.fileUrl = fileUrl
    self.fileDateFormatter.dateFormat = "yyyy-MM-dd_HH-mm-SSS"
    self.setupFileHandle(at: fileUrl)
  }

  func write(_ data: Data) {
    self.fileHandle.write(data)

    if self.fileHandle.offsetInFile >= maxFileSize {
      self.archiveLogFile()
    }
  }

  deinit {
    self.fileHandle.closeFile()
  }

  fileprivate let fileUrl: URL
  fileprivate var fileHandle = FileHandle.standardOutput
  fileprivate let fileDateFormatter = DateFormatter()

  fileprivate func setupFileHandle(at fileUrl: URL) {
    if !fileManager.fileExists(atPath: fileUrl.path) {
      fileManager.createFile(atPath: fileUrl.path, contents: nil)
    }

    if let fileHandle = try? FileHandle(forWritingTo: fileUrl) {
      self.fileHandle = fileHandle
      self.fileHandle.seekToEndOfFile()
    } else {
      NSLog("[ERROR] Could not get handle for \(fileUrl), defaulting to STDOUT")
      self.fileHandle = FileHandle.standardOutput
    }
  }

  fileprivate func archiveLogFile() {
    self.fileHandle.closeFile()

    do {
      let fileTimestamp = self.fileDateFormatter.string(from: Date())
      let fileName = self.fileUrl.deletingPathExtension().lastPathComponent
      let archiveFileName = "\(fileName)-\(fileTimestamp).\(self.fileUrl.pathExtension)"
      let archiveFileUrl = self.fileUrl
        .deletingLastPathComponent().appendingPathComponent(archiveFileName)

      try fileManager.moveItem(at: self.fileUrl, to: archiveFileUrl)
    } catch let error as NSError {
      NSLog("[ERROR] Could not archive log file: \(error)")
    }

    self.setupFileHandle(at: self.fileUrl)
  }
}

class FileLogger {

  enum Level: String {

    case `default` = "DEFAULT"
    case info = "INFO"
    case debug = "DEBUG"
    case error = "ERROR"
    case fault = "FAULT"
  }

  let uuid = UUID().uuidString
  let name: String

  var shouldLogDebug: Bool

  init<T>(as name: T, with fileUrl: URL, shouldLogDebug: Bool? = nil) {
    if let debug = shouldLogDebug {
      self.shouldLogDebug = debug
    } else {
#if DEBUG
      self.shouldLogDebug = true
#else
      self.shouldLogDebug = false
#endif
    }

    switch name {
    case let str as String: self.name = str
    default: self.name = String(describing: name)
    }

    guard fileUrl.isFileURL else {
      preconditionFailure("\(fileUrl) must be a file URL!")
    }

    self.fileUrl = fileUrl
    self.logDateFormatter.dateFormat = "dd HH:mm:SSS"

    fileAppendersAccess.lock()
    defer { fileAppendersAccess.unlock() }
    if let fileAppender = fileAppenders[fileUrl], let ref = fileAppenderRefs[fileUrl] {
      self.fileAppender = fileAppender
      fileAppenderRefs[fileUrl] = ref + 1
    } else {
      self.fileAppender = FileAppender(with: fileUrl)
      fileAppenders[fileUrl] = self.fileAppender
      fileAppenderRefs[fileUrl] = 1
    }
  }

  deinit {
    fileAppendersAccess.lock()
    defer { fileAppendersAccess.unlock() }

    guard let ref = fileAppenderRefs[self.fileUrl] else {
      return
    }

    guard ref > 1 else {
      fileAppenderRefs.removeValue(forKey: self.fileUrl)
      return
    }

    fileAppenderRefs[self.fileUrl] = ref - 1
  }

  func hr(file: String = #file, line: Int = #line, function: String = #function) {
    self.log("----------", level: .debug, file: file, line: line, function: function)
  }

  func mark(file: String = #file, line: Int = #line, function: String = #function) {
    self.log("", level: .debug, file: file, line: line, function: function)
  }

  func `default`<T>(_ message: T,
                    file: String = #file, line: Int = #line, function: String = #function) {

    self.log(message, level: .default, file: file, line: line, function: function)
  }

  func info<T>(_ message: T,
               file: String = #file, line: Int = #line, function: String = #function) {

    self.log(message, level: .info, file: file, line: line, function: function)
  }

  func debug<T>(_ message: T,
                file: String = #file, line: Int = #line, function: String = #function) {

    self.log(message, level: .debug, file: file, line: line, function: function)
  }

  func error<T>(_ message: T,
                file: String = #file, line: Int = #line, function: String = #function) {

    self.log(message, level: .error, file: file, line: line, function: function)
  }

  func fault<T>(_ message: T,
                file: String = #file, line: Int = #line, function: String = #function) {

    self.log(message, level: .fault, file: file, line: line, function: function)
  }

  func log<T>(_ message: T, level: Level = .default,
              file: String = #file, line: Int = #line, function: String = #function) {

    guard self.shouldLogDebug else {
      return
    }

    queue.async {
      let timestamp = self.logDateFormatter.string(from: Date())
      let strMsg = self.string(from: message)

      let logMsg = "\(timestamp) \(self.name) \(function) \(strMsg)"
      let data = "[\(level.rawValue)] \(logMsg)\n".data(using: .utf8) ?? conversionError
      self.fileAppender.write(data)
    }
  }

  fileprivate func string<T>(from obj: T) -> String {
    switch obj {
    case let str as String: return str
    case let convertible as CustomStringConvertible: return convertible.description
    case let convertible as CustomDebugStringConvertible: return convertible.debugDescription
    default: return String(describing: obj)
    }
  }

  fileprivate let fileUrl: URL
  fileprivate let fileAppender: FileAppender
  fileprivate let logDateFormatter = DateFormatter()
}

fileprivate let conversionError = "[ERROR] Could not convert log msg to Data!".data(using: .utf8)!
fileprivate let fileManager = FileManager.default
fileprivate let maxFileSize: UInt64 = 4 * 1024 * 1024
fileprivate let queue = DispatchQueue(label: "logger", qos: .background)
fileprivate let fileAppendersAccess = NSRecursiveLock()
fileprivate var fileAppenders: [URL: FileAppender] = [:]
fileprivate var fileAppenderRefs: [URL: Int] = [:]