//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2024 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#if compiler(>=6)
package import BuildServerProtocol
import BuildSystemIntegration
import Foundation
package import LanguageServerProtocol
import LanguageServerProtocolExtensions
import SKLogging
import SwiftExtensions
import ToolchainRegistry
import TSCExtensions

import struct TSCBasic.AbsolutePath
import class TSCBasic.Process
import struct TSCBasic.ProcessResult
#else
import BuildServerProtocol
import BuildSystemIntegration
import Foundation
import LanguageServerProtocol
import LanguageServerProtocolExtensions
import SKLogging
import SwiftExtensions
import ToolchainRegistry
import TSCExtensions

import struct TSCBasic.AbsolutePath
import class TSCBasic.Process
import struct TSCBasic.ProcessResult
#endif

private let updateIndexStoreIDForLogging = AtomicUInt32(initialValue: 1)

package enum FileToIndex: CustomLogStringConvertible {
  /// A non-header file
  case indexableFile(DocumentURI)

  /// A header file where `mainFile` should be indexed to update the index of `header`.
  case headerFile(header: DocumentURI, mainFile: DocumentURI)

  /// The file whose index store should be updated.
  ///
  /// This file might be a header file that doesn't have build settings associated with it. For the actual compiler
  /// invocation that updates the index store, the `mainFile` should be used.
  package var sourceFile: DocumentURI {
    switch self {
    case .indexableFile(let uri): return uri
    case .headerFile(header: let header, mainFile: _): return header
    }
  }

  /// The file that should be used for compiler invocations that update the index.
  ///
  /// If the `sourceFile` is a header file, this will be a main file that includes the header. Otherwise, it will be the
  /// same as `sourceFile`.
  var mainFile: DocumentURI {
    switch self {
    case .indexableFile(let uri): return uri
    case .headerFile(header: _, mainFile: let mainFile): return mainFile
    }
  }

  package var description: String {
    switch self {
    case .indexableFile(let uri):
      return uri.description
    case .headerFile(header: let header, mainFile: let mainFile):
      return "\(header.description) using main file \(mainFile.description)"
    }
  }

  package var redactedDescription: String {
    switch self {
    case .indexableFile(let uri):
      return uri.redactedDescription
    case .headerFile(header: let header, mainFile: let mainFile):
      return "\(header.redactedDescription) using main file \(mainFile.redactedDescription)"
    }
  }
}

/// A file to index and the target in which the file should be indexed.
package struct FileAndTarget: Sendable {
  package let file: FileToIndex
  package let target: BuildTargetIdentifier
}

/// Describes a task to index a set of source files.
///
/// This task description can be scheduled in a `TaskScheduler`.
package struct UpdateIndexStoreTaskDescription: IndexTaskDescription {
  package static let idPrefix = "update-indexstore"
  package let id = updateIndexStoreIDForLogging.fetchAndIncrement()

  /// The files that should be indexed.
  package let filesToIndex: [FileAndTarget]

  /// The build system manager that is used to get the toolchain and build settings for the files to index.
  private let buildSystemManager: BuildSystemManager

  /// A reference to the underlying index store. Used to check if the index is already up-to-date for a file, in which
  /// case we don't need to index it again.
  private let index: UncheckedIndex

  private let indexStoreUpToDateTracker: UpToDateTracker<DocumentURI>

  /// Whether files that have an up-to-date unit file should be indexed.
  ///
  /// In general, this should be `false`. The only situation when this should be set to `true` is when the user
  /// explicitly requested a re-index of all files.
  private let indexFilesWithUpToDateUnit: Bool

  /// See `SemanticIndexManager.logMessageToIndexLog`.
  private let logMessageToIndexLog: @Sendable (_ taskID: String, _ message: String) -> Void

  /// How long to wait until we cancel an update indexstore task. This timeout should be long enough that all
  /// `swift-frontend` tasks finish within it. It prevents us from blocking the index if the type checker gets stuck on
  /// an expression for a long time.
  private let timeout: Duration

  /// Test hooks that should be called when the index task finishes.
  private let testHooks: IndexTestHooks

  /// The task is idempotent because indexing the same file twice produces the same result as indexing it once.
  package var isIdempotent: Bool { true }

  package var estimatedCPUCoreCount: Int { 1 }

  package var description: String {
    return self.redactedDescription
  }

  package var redactedDescription: String {
    return "update-indexstore-\(id)"
  }

  static func canIndex(language: Language) -> Bool {
    return language.semanticKind != nil
  }

  init(
    filesToIndex: [FileAndTarget],
    buildSystemManager: BuildSystemManager,
    index: UncheckedIndex,
    indexStoreUpToDateTracker: UpToDateTracker<DocumentURI>,
    indexFilesWithUpToDateUnit: Bool,
    logMessageToIndexLog: @escaping @Sendable (_ taskID: String, _ message: String) -> Void,
    timeout: Duration,
    testHooks: IndexTestHooks
  ) {
    self.filesToIndex = filesToIndex
    self.buildSystemManager = buildSystemManager
    self.index = index
    self.indexStoreUpToDateTracker = indexStoreUpToDateTracker
    self.indexFilesWithUpToDateUnit = indexFilesWithUpToDateUnit
    self.logMessageToIndexLog = logMessageToIndexLog
    self.timeout = timeout
    self.testHooks = testHooks
  }

  package func execute() async {
    // Only use the last two digits of the indexing ID for the logging scope to avoid creating too many scopes.
    // See comment in `withLoggingScope`.
    // The last 2 digits should be sufficient to differentiate between multiple concurrently running indexing operation.
    await withLoggingSubsystemAndScope(subsystem: indexLoggingSubsystem, scope: "update-indexstore-\(id % 100)") {
      let startDate = Date()

      await testHooks.updateIndexStoreTaskDidStart?(self)

      let filesToIndexDescription = filesToIndex.map {
        $0.file.sourceFile.fileURL?.lastPathComponent ?? $0.file.sourceFile.stringValue
      }
      .joined(separator: ", ")
      logger.log(
        "Starting updating index store with priority \(Task.currentPriority.rawValue, privacy: .public): \(filesToIndexDescription)"
      )
      let filesToIndex = filesToIndex.sorted(by: { $0.file.sourceFile.stringValue < $1.file.sourceFile.stringValue })
      // TODO: Once swiftc supports it, we should group files by target and index files within the same target together
      // in one swiftc invocation. (https://github.com/swiftlang/sourcekit-lsp/issues/1268)
      for file in filesToIndex {
        await updateIndexStore(forSingleFile: file.file, in: file.target)
      }
      await testHooks.updateIndexStoreTaskDidFinish?(self)
      logger.log(
        "Finished updating index store in \(Date().timeIntervalSince(startDate) * 1000, privacy: .public)ms: \(filesToIndexDescription)"
      )
    }
  }

  package func dependencies(
    to currentlyExecutingTasks: [UpdateIndexStoreTaskDescription]
  ) -> [TaskDependencyAction<UpdateIndexStoreTaskDescription>] {
    let selfMainFiles = Set(filesToIndex.map(\.file.mainFile))
    return currentlyExecutingTasks.compactMap { (other) -> TaskDependencyAction<UpdateIndexStoreTaskDescription>? in
      if !other.filesToIndex.lazy.map(\.file.mainFile).contains(where: { selfMainFiles.contains($0) }) {
        // Disjoint sets of files can be indexed concurrently.
        return nil
      }
      if self.filesToIndex.count < other.filesToIndex.count {
        // If there is an index operation with more files already running, suspend it.
        // The most common use case for this is if we schedule an entire target to be indexed in the background and then
        // need a single file indexed for use interaction. We should suspend the target-wide indexing and just index
        // the current file to get index data for it ASAP.
        return .cancelAndRescheduleDependency(other)
      } else {
        return .waitAndElevatePriorityOfDependency(other)
      }
    }
  }

  private func updateIndexStore(forSingleFile file: FileToIndex, in target: BuildTargetIdentifier) async {
    guard await !indexStoreUpToDateTracker.isUpToDate(file.sourceFile) else {
      // If we know that the file is up-to-date without having ot hit the index, do that because it's fastest.
      return
    }
    guard
      indexFilesWithUpToDateUnit
        || !index.checked(for: .modifiedFiles).hasUpToDateUnit(for: file.sourceFile, mainFile: file.mainFile)
    else {
      logger.debug("Not indexing \(file.forLogging) because index has an up-to-date unit")
      // We consider a file's index up-to-date if we have any up-to-date unit. Changing build settings does not
      // invalidate the up-to-date status of the index.
      return
    }
    if file.mainFile != file.sourceFile {
      logger.log("Updating index store of \(file.forLogging) using main file \(file.mainFile.forLogging)")
    }
    guard let language = await buildSystemManager.defaultLanguage(for: file.mainFile, in: target) else {
      logger.error("Not indexing \(file.forLogging) because its language could not be determined")
      return
    }
    let buildSettings = await buildSystemManager.buildSettings(
      for: file.mainFile,
      in: target,
      language: language,
      fallbackAfterTimeout: false
    )
    guard let buildSettings else {
      logger.error("Not indexing \(file.forLogging) because it has no compiler arguments")
      return
    }
    if buildSettings.isFallback {
      // Fallback build settings don’t even have an indexstore path set, so they can't generate index data that we would
      // pick up. Also, indexing with fallback args has some other problems:
      // - If it did generate a unit file, we would consider the file’s index up-to-date even if the compiler arguments
      //   change, which means that we wouldn't get any up-to-date-index even when we have build settings for the file.
      // - It's unlikely that the index from a single file with fallback arguments will be very useful as it can't tie
      //   into the rest of the project.
      // So, don't index the file.
      logger.error("Not indexing \(file.forLogging) because it has fallback compiler arguments")
      return
    }
    guard let toolchain = await buildSystemManager.toolchain(for: file.mainFile, in: target, language: language) else {
      logger.error(
        "Not updating index store for \(file.forLogging) because no toolchain could be determined for the document"
      )
      return
    }
    let startDate = Date()
    switch language.semanticKind {
    case .swift:
      do {
        try await updateIndexStore(
          forSwiftFile: file.mainFile,
          buildSettings: buildSettings,
          toolchain: toolchain
        )
      } catch {
        logger.error("Updating index store for \(file.forLogging) failed: \(error.forLogging)")
        BuildSettingsLogger.log(settings: buildSettings, for: file.mainFile)
      }
    case .clang:
      do {
        try await updateIndexStore(
          forClangFile: file.mainFile,
          buildSettings: buildSettings,
          toolchain: toolchain
        )
      } catch {
        logger.error("Updating index store for \(file) failed: \(error.forLogging)")
        BuildSettingsLogger.log(settings: buildSettings, for: file.mainFile)
      }
    case nil:
      logger.error(
        "Not updating index store for \(file) because it is a language that is not supported by background indexing"
      )
    }
    await indexStoreUpToDateTracker.markUpToDate([file.sourceFile], updateOperationStartDate: startDate)
  }

  private func updateIndexStore(
    forSwiftFile uri: DocumentURI,
    buildSettings: FileBuildSettings,
    toolchain: Toolchain
  ) async throws {
    guard let swiftc = toolchain.swiftc else {
      logger.error(
        "Not updating index store for \(uri.forLogging) because toolchain \(toolchain.identifier) does not contain a Swift compiler"
      )
      return
    }

    let args =
      try [swiftc.filePath] + buildSettings.compilerArguments + [
        "-index-file",
        "-index-file-path", uri.pseudoPath,
        // batch mode is not compatible with -index-file
        "-disable-batch-mode",
        // Fake an output path so that we get a different unit file for every Swift file we background index
        "-index-unit-output-path", uri.pseudoPath + ".o",
      ]

    try await runIndexingProcess(
      indexFile: uri,
      buildSettings: buildSettings,
      processArguments: args,
      workingDirectory: buildSettings.workingDirectory.map(AbsolutePath.init(validating:))
    )
  }

  private func updateIndexStore(
    forClangFile uri: DocumentURI,
    buildSettings: FileBuildSettings,
    toolchain: Toolchain
  ) async throws {
    guard let clang = toolchain.clang else {
      logger.error(
        "Not updating index store for \(uri.forLogging) because toolchain \(toolchain.identifier) does not contain clang"
      )
      return
    }

    try await runIndexingProcess(
      indexFile: uri,
      buildSettings: buildSettings,
      processArguments: [clang.filePath] + buildSettings.compilerArguments,
      workingDirectory: buildSettings.workingDirectory.map(AbsolutePath.init(validating:))
    )
  }

  private func runIndexingProcess(
    indexFile: DocumentURI,
    buildSettings: FileBuildSettings,
    processArguments: [String],
    workingDirectory: AbsolutePath?
  ) async throws {
    if Task.isCancelled {
      return
    }
    let start = ContinuousClock.now
    let signposter = Logger(subsystem: LoggingScope.subsystem, category: "indexing").makeSignposter()
    let signpostID = signposter.makeSignpostID()
    let state = signposter.beginInterval(
      "Indexing",
      id: signpostID,
      "Indexing \(indexFile.fileURL?.lastPathComponent ?? indexFile.pseudoPath)"
    )
    defer {
      signposter.endInterval("Indexing", state)
    }
    let taskId = "indexing-\(id)"
    logMessageToIndexLog(
      taskId,
      """
      Indexing \(indexFile.pseudoPath)
      \(processArguments.joined(separator: " "))
      """
    )

    let stdoutHandler = PipeAsStringHandler { logMessageToIndexLog(taskId, $0) }
    let stderrHandler = PipeAsStringHandler { logMessageToIndexLog(taskId, $0) }

    let result: ProcessResult
    do {
      result = try await withTimeout(timeout) {
        try await Process.run(
          arguments: processArguments,
          workingDirectory: workingDirectory,
          outputRedirection: .stream(
            stdout: { @Sendable bytes in stdoutHandler.handleDataFromPipe(Data(bytes)) },
            stderr: { @Sendable bytes in stderrHandler.handleDataFromPipe(Data(bytes)) }
          )
        )
      }
    } catch {
      logMessageToIndexLog(taskId, "Finished error in \(start.duration(to: .now)): \(error)")
      throw error
    }
    let exitStatus = result.exitStatus.exhaustivelySwitchable
    logMessageToIndexLog(taskId, "Finished with \(exitStatus.description) in \(start.duration(to: .now))")
    switch exitStatus {
    case .terminated(code: 0):
      break
    case .terminated(code: let code):
      // This most likely happens if there are compilation errors in the source file. This is nothing to worry about.
      let stdout = (try? String(bytes: result.output.get(), encoding: .utf8)) ?? "<failed to decode stdout>"
      let stderr = (try? String(bytes: result.stderrOutput.get(), encoding: .utf8)) ?? "<failed to decode stderr>"
      // Indexing will frequently fail if the source code is in an invalid state. Thus, log the failure at a low level.
      logger.debug(
        """
        Updating index store for \(indexFile.forLogging) terminated with non-zero exit code \(code)
        Stderr:
        \(stderr)
        Stdout:
        \(stdout)
        """
      )
      BuildSettingsLogger.log(level: .debug, settings: buildSettings, for: indexFile)
    case .signalled(signal: let signal):
      if !Task.isCancelled {
        // The indexing job finished with a signal. Could be because the compiler crashed.
        // Ignore signal exit codes if this task has been cancelled because the compiler exits with SIGINT if it gets
        // interrupted.
        logger.error("Updating index store for \(indexFile.forLogging) signaled \(signal)")
        BuildSettingsLogger.log(level: .error, settings: buildSettings, for: indexFile)
      }
    case .abnormal(exception: let exception):
      if !Task.isCancelled {
        logger.error("Updating index store for \(indexFile.forLogging) exited abnormally \(exception)")
        BuildSettingsLogger.log(level: .error, settings: buildSettings, for: indexFile)
      }
    }
  }
}