import CodersClient
import Dependencies
import DependenciesMacros
import FileClient
import Foundation
import ShellClient

public extension DependencyValues {

  /// Interacts with the user's configuration.
  var configurationClient: ConfigurationClient {
    get { self[ConfigurationClient.self] }
    set { self[ConfigurationClient.self] = newValue }
  }
}

/// Represents actions that can be taken on user's configuration files.
///
///
@DependencyClient
public struct ConfigurationClient: Sendable {

  /// Find the user's configuration, searches in the current directory and default
  /// locations where configuration can be stored. An error is thrown if no configuration
  /// is found.
  public var find: @Sendable () async throws -> File

  /// Generate a configuration file for the user.
  public var generate: @Sendable (GenerateOptions) async throws -> String

  /// Load a configuration file from the given file location. If the file is
  /// not provided then we return an empty configuraion item.
  public var load: @Sendable (File?) async throws -> Configuration

  /// Write the configuration to the given file, optionally forcing an overwrite of
  /// the file.
  ///
  /// ## NOTE: This uses the `fileClient.write` under the hood, so if you need to control
  ///          what happens during tests, then you can customize the behavior of the fileClient.
  ///
  var write: @Sendable (File, Configuration, Bool) async throws -> Void

  /// Find the user's configuration and load it.
  public func findAndLoad() async throws -> Configuration {
    let file = try? await find()
    return try await load(file)
  }

  /// Write the configuration to the given file, optionally forcing an overwrite of
  /// the file. If a file already exists and force is not supplied then we will create
  /// a backup of the existing file.
  ///
  /// ## NOTE: This uses the `fileClient.write` under the hood, so if you need to control
  ///          what happens during tests, then you can customize the behavior of the fileClient.
  ///
  /// - Parameters:
  ///   - configuration: The configuration to save.
  ///   - file: The file location and type to save.
  ///   - force: Force overwritting if a file already exists.
  public func write(
    _ configuration: Configuration,
    to file: File,
    force: Bool = false
  ) async throws {
    try await write(file, configuration, force)
  }

  public struct GenerateOptions: Equatable, Sendable {

    public let force: Bool
    public let json: Bool
    public let path: Path?

    public init(
      force: Bool = false,
      json: Bool = false,
      path: Path? = nil
    ) {
      self.force = force
      self.json = json
      self.path = path
    }

    public enum Path: Equatable, Sendable {
      case file(File)
      case directory(String)
    }
  }
}

extension ConfigurationClient: DependencyKey {
  public static var testValue: Self { Self() }

  public static func live(environment: [String: String]) -> Self {
    let liveClient = LiveConfigurationClient(environment: environment)
    return .init(
      find: { try await liveClient.find() },
      generate: { try await liveClient.generate($0) },
      load: { try await liveClient.load(file: $0) },
      write: { try await liveClient.write($1, to: $0, force: $2) }
    )
  }

  public static var liveValue: Self {
    .live(environment: ProcessInfo.processInfo.environment)
  }

  @_spi(Internal)
  public static func mock(_ configuration: Configuration = .mock) -> Self {
    .init(
      find: { throw MockFindError() },
      generate: Self().generate,
      load: { _ in configuration },
      write: Self().write
    )
  }
}

struct LiveConfigurationClient {

  private let environment: [String: String]

  @Dependency(\.coders) var coders
  @Dependency(\.fileClient) var fileManager
  @Dependency(\.logger) var logger

  let validFileNames = [
    "config.json", "config.toml",
    ".hparc.json", ".hparc.toml"
  ]

  init(environment: [String: String]) {
    self.environment = environment
  }

  func find() async throws -> File {
    logger.debug("Begin find configuration.")

    if let pwd = environment["PWD"],
       let file = await findInDirectory(pwd)
    {
      logger.debug("Found configuration in pwd: \(file.path)")
      return file
    }

    if let configHome = environment.hpaConfigHome,
       let file = await findInDirectory(configHome)
    {
      logger.debug("Found configuration in config home env var: \(file.path)")
      return file
    }

    if let configFile = environment.hpaConfigFile,
       isReadable(configFile),
       let file = File(configFile)
    {
      logger.debug("Found configuration in config file env var: \(file.path)")
      return file
    }

    if let file = await findInDirectory(fileManager.homeDirectory()) {
      logger.debug("Found configuration in home directory: \(file.path)")
      return file
    }

    if let file = await findInDirectory("\(environment.xdgConfigHome)/\(HPAKey.configDirName)") {
      logger.debug("Found configuration in xdg config directory: \(file.path)")
      return file
    }

    throw ConfigurationError.configurationNotFound
  }

  func generate(_ options: ConfigurationClient.GenerateOptions) async throws -> String {
    @Dependency(\.logger) var logger

    let file: File

    if let path = options.path {
      switch path {
      case let .file(requestedFile):
        file = requestedFile
      case let .directory(directory):
        file = .init("\(directory)/\(HPAKey.defaultFileNameWithoutExtension).\(options.json ? "json" : "toml")")!
      }
    } else {
      let configDir = "\(environment.xdgConfigHome)/\(HPAKey.configDirName)"
      file = .init("\(configDir)/\(HPAKey.defaultFileName)")!
    }

    logger.debug("Begin generating configuration: \(file.path), force: \(options.force)")

    let expandedPath = file.path.replacingOccurrences(
      of: "~",
      with: fileManager.homeDirectory().cleanFilePath
    )

    let fileUrl = URL(filePath: expandedPath)

    if !options.force {
      guard !fileManager.fileExists(fileUrl) else {
        throw ConfigurationError.fileExists(path: file.path)
      }
    }

    let fileDirectory = fileUrl.deletingLastPathComponent()
    let directoryExists = try await fileManager.isDirectory(fileDirectory)

    if !directoryExists {
      logger.debug("Creating directory at: \(fileDirectory.cleanFilePath)")
      try await fileManager.createDirectory(fileDirectory)
    }

    if case .toml = file {
      // In the case of toml, we copy the internal resource that includes
      // usage comments in the file.
      guard let resourceFile = Bundle.module.url(
        forResource: HPAKey.resourceFileName,
        withExtension: HPAKey.resourceFileExtension
      ) else {
        throw ConfigurationError.resourceNotFound
      }

      try await fileManager.copy(resourceFile, fileUrl)
    } else {
      // Json does not allow comments, so we write the mock configuration
      // to the file path.
      try await write(.mock, to: File(fileUrl)!, force: options.force)
    }

    return fileUrl.cleanFilePath
  }

  func load(file: File?) async throws -> Configuration {
    guard let file else { return .init() }
    let data = try await fileManager.load(file.url)

    switch file {
    case .json:
      return try coders.jsonDecoder().decode(Configuration.self, from: data)
    case .toml:
      guard let string = String(data: data, encoding: .utf8) else {
        throw ConfigurationError.decodingError
      }
      return try coders.tomlDecoder().decode(Configuration.self, from: string)
    }
  }

  func write(
    _ configuration: Configuration,
    to file: File,
    force: Bool
  ) async throws {
    let exists = fileManager.fileExists(file.url)

    if !force, exists {
      let backupUrl = file.url.appendingPathExtension(".back")
      logger.warning("File exists, creating a backup of the existing file at: \(backupUrl.cleanFilePath)")
      try await fileManager.copy(file.url, backupUrl)
    }

    let data: Data

    switch file {
    case .json:
      data = try coders.jsonEncoder().encode(configuration)
    case .toml:
      let string = try coders.tomlEncoder().encode(configuration)
      data = Data(string.utf8)
    }

    try await fileManager.write(data, file.url)
  }

  private func findInDirectory(_ directory: URL) async -> File? {
    for file in validFileNames {
      let url = directory.appending(path: file)
      if isReadable(url), let file = File(url) {
        return file
      }
    }
    return nil
  }

  private func findInDirectory(_ directory: String) async -> File? {
    await findInDirectory(URL(filePath: directory))
  }

  private func isReadable(_ file: URL) -> Bool {
    FileManager.default.isReadableFile(atPath: file.cleanFilePath)
  }

  private func isReadable(_ file: String) -> Bool {
    isReadable(URL(filePath: file))
  }

}

enum ConfigurationError: Error {
  case configurationNotFound
  case resourceNotFound
  case decodingError
  case fileExists(path: String)
}

struct MockFindError: Error {}