Decoder.swift

import Foundation

/// Instances of this class are capable of decoding CSV files as described by the `Codable` protocol.
@dynamicMemberLookup open class CSVDecoder {
  /// Wrap all configurations in a single easy-to-use structure.
  private final var _configuration: Configuration
  /// A dictionary you use to customize the decoding process by providing contextual information.
  open var userInfo: [CodingUserInfoKey:Any]

  /// Creates a CSV decoder with tthe default configuration values.
  /// - parameter configuration: Configuration values for the decoding process.
  public init(configuration: Configuration = Configuration()) {
    self._configuration = configuration
    self.userInfo = Dictionary()
  }

  /// Creates a CSV decoder and passes the default configuration values to the closure.
  /// - parameter configuration: A closure receiving the default configuration values and returning (by `inout`) a tweaked version of them.
  @inlinable public convenience init(configuration: (inout Configuration)->Void) {
    var config = Configuration()
    configuration(&config)
    self.init(configuration: config)
  }

  /// Gives direct access to all the decoder's configuration values.
  /// - parameter member: Writable key path for the decoder's configuration value.
  public final subscript<V>(dynamicMember member: WritableKeyPath<CSVDecoder.Configuration,V>) -> V {
    get { self._configuration[keyPath: member] }
    set { self._configuration[keyPath: member] = newValue }
  }
}

extension CSVDecoder {
  /// Returns a value of the type you specify, decoded from a CSV file (given as a `Data` blob).
  /// - parameter type: The type of the value to decode from the supplied file.
  /// - parameter data: The data blob representing a CSV file.
  public func decode<T:Decodable>(_ type: T.Type, from data: Data) throws -> T {
    let reader = try CSVReader(input: data, configuration: self._configuration.readerConfiguration)
    return try withExtendedLifetime(ShadowDecoder.Source(reader: reader, configuration: self._configuration, userInfo: self.userInfo)) {
      try T(from: ShadowDecoder(source: .passUnretained($0), codingPath: []))
    }
  }

  /// Returns a value of the type you specify, decoded from a CSV file (given as a `String`).
  /// - parameter type: The type of the value to decode from the supplied file.
  /// - parameter string: A Swift string representing a CSV file.
  public func decode<T:Decodable>(_ type: T.Type, from string: String) throws -> T {
    let reader = try CSVReader(input: string, configuration: self._configuration.readerConfiguration)
    return try withExtendedLifetime(ShadowDecoder.Source(reader: reader, configuration: self._configuration, userInfo: self.userInfo)) {
      try T(from: ShadowDecoder(source: .passUnretained($0), codingPath: []))
    }
  }

  /// Returns a value of the type you specify, decoded from a CSV file (being pointed by the url).
  /// - parameter type: The type of the value to decode from the supplied file.
  /// - parameter url: The URL pointing to the file to decode.
  public func decode<T:Decodable>(_ type: T.Type, from url: URL) throws -> T {
    let reader = try CSVReader(input: url, configuration: self._configuration.readerConfiguration)
    return try withExtendedLifetime(ShadowDecoder.Source(reader: reader, configuration: self._configuration, userInfo: self.userInfo)) {
      try T(from: ShadowDecoder(source: .passUnretained($0), codingPath: []))
    }
  }

  /// Returns a value of the type you specify, decoded from a CSV file (provided by the input stream).
  /// - parameter type: The type of the value to decode from the supplied file.
  /// - parameter stream: The input stream providing the raw bytes.
  public func decode<T:Decodable>(_ type: T.Type, from stream: InputStream) throws -> T {
    let reader = try CSVReader(input: stream, configuration: self._configuration.readerConfiguration)
    return try withExtendedLifetime(ShadowDecoder.Source(reader: reader, configuration: self._configuration, userInfo: self.userInfo)) {
      try T(from: ShadowDecoder(source: .passUnretained($0), codingPath: []))
    }
  }
}

extension CSVDecoder {
  /// Returns a sequence for decoding row-by-row from a CSV file (given as a `Data` blob).
  /// - parameter data: The data blob representing a CSV file.
  /// - throws: `CSVError<CSVReader>` exclusively.
  public func lazy(from data: Data) throws -> Lazy {
    let reader = try CSVReader(input: data, configuration: self._configuration.readerConfiguration)
    let source = ShadowDecoder.Source(reader: reader, configuration: self._configuration, userInfo: self.userInfo)
    return Lazy(source: source)
  }

  /// Returns a sequence for decoding row-by-row from a CSV file (given as a `String`).
  /// - parameter string: A Swift string representing a CSV file.
  /// - throws: `CSVError<CSVReader>` exclusively.
  public func lazy(from string: String) throws -> Lazy {
    let reader = try CSVReader(input: string, configuration: self._configuration.readerConfiguration)
    let source = ShadowDecoder.Source(reader: reader, configuration: self._configuration, userInfo: self.userInfo)
    return Lazy(source: source)
  }

  /// Returns a sequence for decoding row-by-row from a CSV file (being pointed by `url`).
  /// - parameter url: The URL pointing to the file to decode.
  /// - throws: `CSVError<CSVReader>` exclusively.
  public func lazy(from url: URL) throws -> Lazy {
    let reader = try CSVReader(input: url, configuration: self._configuration.readerConfiguration)
    let source = ShadowDecoder.Source(reader: reader, configuration: self._configuration, userInfo: self.userInfo)
    return Lazy(source: source)
  }
}

#if canImport(Combine)
import Combine

@available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
extension CSVDecoder: TopLevelDecoder {
  public typealias Input = Data
}
#endif