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

public extension DependencyValues {
  var configurationClient: ConfigurationClient {
    get { self[ConfigurationClient.self] }
    set { self[ConfigurationClient.self] = newValue }
  }
}

@DependencyClient
public struct ConfigurationClient: Sendable {
  public var find: @Sendable () async throws -> File
  var generate: @Sendable (File, Bool) async throws -> Void
  public var load: @Sendable (File?) async throws -> Configuration
  var write: @Sendable (File, Configuration, Bool) async throws -> Void

  public func findAndLoad() async throws -> Configuration {
    let file = try? await find()
    return try await load(file)
  }

  public func generate(
    at file: File,
    force: Bool = false
  ) async throws {
    try await generate(file, force)
  }

  public func write(
    _ configuration: Configuration,
    to file: File,
    force: Bool = false
  ) async throws {
    try await write(file, configuration, force)
  }
}

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

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

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

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(at file: File, force: Bool) async throws {
    if !force {
      guard !fileManager.fileExists(file.url) else {
        throw ConfigurationError.fileExists(path: file.path)
      }
    }

    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, file.url)
    } else {
      // Json does not allow comments, so we write the mock configuration
      // to the file path.
      try await write(.mock, to: file, force: force)
    }
  }

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

    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)
}