import Foundation

private typealias RuntimeFileCreator = (Data, String, String) throws -> String

private struct PreparedAuthentication {
  let document: SslocalRuntimeDocument
  let id: String?
  let files: [String]
}

/// GUI 独占配置准备与监管发布；Agent 独占稳定链接切换和退休文件回收。
struct RuntimeFileStore {
  enum PersistenceError: Error, Equatable {
    case ioFailure(detail: String)
    case rollbackFailed(detail: String)
  }

  private let paths: RuntimePaths
  var fileURL: URL { paths.fileURL }
  private let fileWriter: (Data, URL) throws -> Void

  init(
    fileURL: URL = ApplicationSupportPaths.current.runtime.fileURL,
    fileWriter: @escaping (Data, URL) throws -> Void = { try AtomicFileWriter.write($0, to: $1) }
  ) {
    paths = RuntimePaths(fileURL: fileURL)
    self.fileWriter = fileWriter
  }

  var directoryURL: URL { paths.directoryURL }
  var supervisionFileURL: URL { paths.supervisionFileURL }
  var failureFileURL: URL { paths.failureFileURL }
  var pidFileURL: URL { paths.pidFileURL }
  var aclFileURL: URL { paths.aclFileURL }
  var runtimeStatusFileURL: URL { paths.runtimeStatusFileURL }

  func write(_ document: SslocalRuntimeDocument) throws {
    try write(PreparedRuntimeContract(document))
  }

  func write(_ contract: PreparedRuntimeContract) throws {
    try RuntimePublication.withLock(in: directoryURL) {
      try publishLocked(contract)
    }
  }

  private func publishLocked(_ contract: PreparedRuntimeContract) throws {
    var created: [URL] = []
    var publicationID: String?
    do {
      guard contract.document.isWellFormed else { throw POSIXError(.EINVAL) }
      let old = RuntimePublication.load(at: supervisionFileURL)
      let generation = try reserveGeneration()
      let prefix = String(format: "%020llu", generation)
      func create(_ data: Data, kind: String, suffix: String) throws -> String {
        let name = "\(kind)-\(prefix)-\(suffix)"
        let url = directoryURL.appendingPathComponent(name)
        guard !FileManager.default.fileExists(atPath: url.path) else { throw POSIXError(.EEXIST) }
        // 先登记：注入的写入器即使在写后抛错，也由 GUI 清理本次未发布文件。
        created.append(url)
        try fileWriter(data, url)
        guard RuntimePublication.isRegularFile(url), try Data(contentsOf: url) == data else {
          throw POSIXError(.EIO)
        }
        return name
      }
      let snapshot = try makeSnapshot(
        contract, old: old, generation: generation,
        create: { try create($0, kind: $1, suffix: $2) })
      // 唯一发布点。所有可引用资源已落盘且校验完成；不提前触碰任何活动链接。
      publicationID = snapshot.deploymentID
      try fileWriter(JSONEncoder().encode(snapshot), supervisionFileURL)
    } catch {
      try handlePublicationFailure(error, publicationID: publicationID, created: created)
    }
  }

  private func makeSnapshot(
    _ contract: PreparedRuntimeContract, old: RuntimeSupervision?, generation: UInt64,
    create: RuntimeFileCreator
  ) throws -> RuntimeSupervision {
    var variants = old?.aclVariants ?? [:]
    var selectedACL: RuntimeSupervision.ACL?
    if let acl = contract.document.aclRuntime {
      guard acl.path == aclFileURL.standardizedFileURL.path, acl.isWellFormed else {
        throw POSIXError(.EINVAL)
      }
      selectedACL = try selectACL(acl, variants: &variants, create: create)
    }
    let authentication = try prepareAuthentication(contract.document, old: old, create: create)
    let configurationData = try authentication.document.jsonData()
    let configurationID =
      reusableConfigurationID(
        for: configurationData, previous: old) ?? UUID().uuidString
    let configuration = try create(configurationData, "config", "sslocal.json")
    let intent = PublishedRuntimeIntent(
      sha256: contract.sha256, configurationSHA256: ProxyACLDocument.digest(configurationData),
      summary: Redactor.documentSummary(contract.document))
    let intentMetadata = try create(JSONEncoder().encode(intent), "config", "intent.json")
    let snapshot = RuntimeSupervision(
      version: 2, generation: generation, deploymentID: UUID().uuidString,
      configuration: configuration, configurationID: configurationID,
      intentMetadata: intentMetadata,
      locals: authentication.document.locals.map {
        .init(
          inboundProtocol: $0.inboundProtocol, localAddress: $0.localAddress,
          localPort: $0.localPort, mode: $0.mode)
      }, ipv6Only: authentication.document.ipv6Only,
      authenticationID: authentication.id, authenticationFiles: authentication.files,
      acl: selectedACL, aclVariants: variants)
    guard snapshot.validated(in: directoryURL) else { throw POSIXError(.EINVAL) }
    return snapshot
  }

  private func selectACL(
    _ acl: ProxyACLDocument, variants: inout [String: RuntimeSupervision.ACL],
    create: RuntimeFileCreator
  ) throws -> RuntimeSupervision.ACL {
    if let cached = variants[acl.summary], cached.sha256 == acl.sha256 { return cached }
    guard !acl.content.isEmpty else { throw POSIXError(.ENOENT) }
    let data = Data(acl.content.utf8)
    let name = try create(data, "acl", "\(acl.summary).ini")
    let selected = RuntimeSupervision.ACL(file: name, sha256: acl.sha256, size: data.count)
    variants[acl.summary] = selected
    return selected
  }

  private func reusableConfigurationID(for data: Data, previous: RuntimeSupervision?) -> String? {
    guard let previous, let identity = previous.configurationID,
      publishedIntent(previous)?.configurationSHA256 == ProxyACLDocument.digest(data),
      (try? Data(contentsOf: directoryURL.appendingPathComponent(previous.configuration))) == data
    else { return nil }
    return identity
  }

  private func handlePublicationFailure(
    _ error: Error, publicationID: String?, created: [URL]
  ) throws {
    // 写入器在原子替换后报错时，发布已经发生；不得删除读者可见资源。
    if let publicationID,
      RuntimePublication.load(at: supervisionFileURL)?.deploymentID == publicationID
    {
      throw PersistenceError.ioFailure(detail: "Publication completed but writer reported failure")
    }
    var failures: [String] = []
    for url in created {
      do { try FileManager.default.removeItem(at: url) } catch {
        if FileManager.default.fileExists(atPath: url.path) {
          failures.append(url.lastPathComponent)
        }
      }
    }
    if !failures.isEmpty {
      throw PersistenceError.rollbackFailed(
        detail: "Unpublished cleanup: " + failures.joined(separator: ","))
    }
    throw PersistenceError.ioFailure(detail: String(describing: error))
  }

  private func prepareAuthentication(
    _ document: SslocalRuntimeDocument,
    old: RuntimeSupervision?,
    create: RuntimeFileCreator
  ) throws -> PreparedAuthentication {
    var authenticationID: String?
    var authenticationFiles: [String] = []
    var encoded = document
    if let auth = encoded.listen.authentication {
      guard auth.directory == directoryURL.standardizedFileURL.path else {
        throw POSIXError(.EINVAL)
      }
      let contents = try auth.fileContents()
      let previousFiles = old?.authenticationFiles ?? []
      let unchanged =
        previousFiles.count == contents.count
        && zip(previousFiles, contents).allSatisfy { name, content in
          (try? Data(contentsOf: directoryURL.appendingPathComponent(name))) == content.1
        }
      if unchanged, let oldID = old?.authenticationID {
        authenticationID = oldID
        authenticationFiles = old?.authenticationFiles ?? []
      } else {
        authenticationID = UUID().uuidString
        for (kind, data) in contents {
          authenticationFiles.append(try create(data, "auth", "\(kind).json"))
        }
      }
      for index in encoded.locals.indices
      where encoded.locals[index].localAddress != "127.0.0.1" {
        if encoded.locals[index].inboundProtocol == "socks" {
          encoded.locals[index].socks5AuthConfigPath =
            directoryURL
            .appendingPathComponent(authenticationFiles[0]).path
        } else {
          encoded.locals[index].httpAuthConfigPath =
            directoryURL
            .appendingPathComponent(authenticationFiles[1]).path
        }
      }
    }
    return PreparedAuthentication(
      document: encoded, id: authenticationID, files: authenticationFiles)
  }

  /// 代次高水位独立于部署文件持久保存。预留失败可留空号，溢出拒绝部署。
  private func reserveGeneration() throws -> UInt64 {
    let url = paths.generationFileURL
    let current: UInt64
    if FileManager.default.fileExists(atPath: url.path) {
      guard let value = UInt64(try String(contentsOf: url, encoding: .utf8)) else {
        throw POSIXError(.EINVAL)
      }
      current = value
    } else {
      current = 0
    }
    guard current < UInt64.max else { throw POSIXError(.EOVERFLOW) }
    try AtomicFileWriter.write(Data(String(current + 1).utf8), to: url)
    return current + 1
  }

}

extension RuntimeFileStore {

  /// 意图比较不解析输出正文；最终字节摘要保留原有磁盘漂移检查。
  func contains(_ contract: PreparedRuntimeContract) -> Bool {
    (try? RuntimePublication.withLock(in: directoryURL) {
      guard let snapshot = RuntimePublication.load(at: supervisionFileURL),
        let intent = publishedIntent(snapshot), intent.sha256 == contract.sha256,
        let data = try? Data(
          contentsOf: directoryURL.appendingPathComponent(snapshot.configuration))
      else { return false }
      return ProxyACLDocument.digest(data) == intent.configurationSHA256
    }) ?? false
  }

  func publishedSummary() -> String? {
    try? RuntimePublication.withLock(in: directoryURL) {
      guard let snapshot = RuntimePublication.load(at: supervisionFileURL) else { return nil }
      return publishedIntent(snapshot)?.summary
    }
  }

  private func publishedIntent(_ snapshot: RuntimeSupervision) -> PublishedRuntimeIntent? {
    guard
      let data = try? Data(contentsOf: directoryURL.appendingPathComponent(snapshot.intentMetadata))
    else { return nil }
    return try? JSONDecoder().decode(PublishedRuntimeIntent.self, from: data)
  }

  func receiptIdentity(for document: SslocalRuntimeDocument) -> String? {
    receiptIdentity(for: document.intentSHA256)
  }

  func receiptIdentity(for intentSHA256: String?) -> String? {
    try? RuntimePublication.withLock(in: directoryURL) {
      let snapshot = RuntimePublication.metadata(at: supervisionFileURL)
      guard let snapshot,
        let identity = publishedIntent(snapshot)?.sha256,
        identity == intentSHA256
      else { return nil }
      return snapshot.deploymentID
    }
  }

  func blocksDeployment(_ document: SslocalRuntimeDocument) -> Bool {
    blocksDeployment(document.intentSHA256)
  }

  func blocksDeployment(_ intentSHA256: String?) -> Bool {
    guard let failure = readFailure() else { return false }
    guard let snapshot = RuntimePublication.metadata(at: supervisionFileURL) else { return true }
    guard failure.deploymentID == snapshot.deploymentID else { return false }
    // GUI 私有身份本身丢失时也不自动重试，用户可显式重试修复派生资源。
    guard
      let identity = publishedIntent(snapshot)?.sha256,
      identity.count == 64
    else { return true }
    return identity == intentSHA256
  }

  func readRuntimeReceipt() -> RuntimeDeploymentReceipt? {
    guard let data = try? Data(contentsOf: runtimeStatusFileURL) else { return nil }
    return try? JSONDecoder().decode(RuntimeDeploymentReceipt.self, from: data)
  }

  func readFailure() -> RuntimeDeploymentFailure? {
    guard let data = try? Data(contentsOf: failureFileURL) else { return nil }
    return try? JSONDecoder().decode(RuntimeDeploymentFailure.self, from: data)
  }

  func recordFailure(reason: String) throws {
    try RuntimePublication.withLock(in: directoryURL) {
      guard let snapshot = RuntimePublication.metadata(at: supervisionFileURL) else {
        throw POSIXError(.EINVAL)
      }
      try AtomicFileWriter.write(
        JSONEncoder().encode(
          RuntimeDeploymentFailure(
            deploymentID: snapshot.deploymentID, reason: reason)), to: failureFileURL)
    }
  }

  /// 只清除旧部署失败。Agent 对本代新确认的失败不得被 GUI 健康任务擦除。
  func settleSuccessfulDeployment() throws {
    try RuntimePublication.withLock(in: directoryURL) {
      guard let snapshot = RuntimePublication.metadata(at: supervisionFileURL) else {
        throw POSIXError(.EINVAL)
      }
      if let failure = readFailure(), failure.deploymentID == snapshot.deploymentID {
        throw POSIXError(.EIO)
      }
      try clearFailure()
    }
  }

  func clearFailure() throws {
    if FileManager.default.fileExists(atPath: failureFileURL.path) {
      try FileManager.default.removeItem(at: failureFileURL)
    }
  }

  var hasUnconfirmedChild: Bool {
    let url = paths.childPIDFileURL
    guard FileManager.default.fileExists(atPath: url.path) else { return false }
    guard let data = try? String(contentsOf: url, encoding: .utf8), let pid = Int32(data), pid > 0
    else { return true }
    return kill(pid, 0) == 0 || errno == EPERM
  }

  /// 仅在确认 wrapper 及其子进程退出后调用；高水位与锁跨停止保留。
  func deleteRuntimeFiles() throws {
    try RuntimePublication.withLock(in: directoryURL) {
      guard !hasUnconfirmedChild else { throw POSIXError(.EBUSY) }
      let manager = FileManager.default
      let removableNames = paths.removableFileNames
      for name in try manager.contentsOfDirectory(atPath: directoryURL.path) {
        if RuntimePublication.generation(of: name) != nil
          || removableNames.contains(name)
          || name.hasPrefix("lan-auth-") || name == "acl-digests.json"
          || (name.hasPrefix("acl-") && name.hasSuffix(".ini"))
          || AtomicFileWriter.isResidueName(name)
        {
          try manager.removeItem(at: directoryURL.appendingPathComponent(name))
        }
      }
    }
  }
}

/// GUI 私有发布事实。意图摘要不进入 Agent 监管资料、回执或诊断。
struct PublishedRuntimeIntent: Codable {
  let sha256: String
  let configurationSHA256: String
  let summary: String
}