/*
 * Copyright 2019 Google
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import CommonCrypto
import Foundation
import Utils

struct CarthageBuildOptions {
  /// Location of directory containing all JSON Carthage manifests.
  let jsonDir: URL

  /// Version checking flag.
  let isVersionCheckEnabled: Bool
}

/// Carthage related utility functions. The enum type is used as a namespace here instead of having
/// root functions, and no cases should be added to it.
enum CarthageUtils {}

extension CarthageUtils {
  /// Package all required files for a Carthage release.
  ///
  /// - Parameters:
  ///   - templateDir: The template project directory, contains the dummy Firebase library.
  ///   - carthageJSONDir: Location of directory containing all JSON Carthage manifests.
  ///   - artifacts: Release Artifacts from build.
  ///   - options: Carthage specific options for the build.
  /// - Returns: The path to the root of the Carthage installation.
  static func packageCarthageRelease(templateDir: URL,
                                     artifacts: ZipBuilder.ReleaseArtifacts,
                                     options: CarthageBuildOptions) -> URL? {
    guard let carthagePath = artifacts.carthageDir else { return nil }

    do {
      print("Creating Carthage release...")
      // Package the Carthage distribution with the current directory structure.
      let carthageDir = carthagePath.deletingLastPathComponent().appendingPathComponent("carthage")
      let output = carthageDir.appendingPathComponents([artifacts.firebaseVersion])
      try FileManager.default.createDirectory(at: output, withIntermediateDirectories: true)
      generateCarthageRelease(fromPackagedDir: carthagePath,
                              templateDir: templateDir,
                              jsonDir: options.jsonDir,
                              artifacts: artifacts,
                              outputDir: output,
                              versionCheckEnabled: options.isVersionCheckEnabled)

      print("Done creating Carthage release! Files written to \(output)")

      // Save the directory for later copying.
      return carthageDir
    } catch {
      fatalError("Could not copy output directory for Carthage build: \(error)")
    }
  }

  /// Generates all required files for a Carthage release.
  ///
  /// - Parameters:
  ///   - packagedDir: The packaged directory assembled for the Carthage distribution.
  ///   - templateDir: The template project directory, contains the dummy Firebase library.
  ///   - jsonDir: Location of directory containing all JSON Carthage manifests.
  ///   - firebaseVersion: The version of the Firebase pod.
  ///   - coreDiagnosticsPath: The path to the Core Diagnostics framework built for Carthage.
  ///   - outputDir: The directory where all artifacts should be created.

  private static func generateCarthageRelease(fromPackagedDir packagedDir: URL,
                                              templateDir: URL,
                                              jsonDir: URL,
                                              artifacts: ZipBuilder.ReleaseArtifacts,
                                              outputDir: URL,
                                              versionCheckEnabled: Bool) {
    let directories: [String]
    do {
      directories = try FileManager.default.contentsOfDirectory(atPath: packagedDir.path)
    } catch {
      fatalError("Could not get contents of Firebase directory to package Carthage build. \(error)")
    }
    let firebaseVersion = artifacts.firebaseVersion

    // Loop through each directory available and package it as a separate Zip file.
    for product in directories {
      let fullPath = packagedDir.appendingPathComponent(product)
      guard FileManager.default.isDirectory(at: fullPath) else { continue }

      // Parse the JSON file, ensure that we're not trying to overwrite a release.
      var jsonManifest = parseJSONFile(fromDir: jsonDir, product: product)

      if versionCheckEnabled {
        guard jsonManifest[firebaseVersion] == nil else {
          print("Carthage release for \(product) \(firebaseVersion) already exists - skipping.")
          continue
        }
      }

      // Analytics includes all the Core frameworks and Firebase module, do extra work to package
      // it.
      if product == "FirebaseAnalyticsSwift" {
        createFirebaseFramework(version: firebaseVersion,
                                inDir: fullPath,
                                rootDir: packagedDir,
                                templateDir: templateDir)

        // Copy the NOTICES file from FirebaseCore.
        let noticesName = "NOTICES"
        let coreNotices = fullPath.appendingPathComponents(["FirebaseCore.xcframework",
                                                            noticesName])
        let noticesPath = packagedDir.appendingPathComponent(noticesName)
        do {
          try FileManager.default.copyItem(at: noticesPath, to: coreNotices)
        } catch {
          fatalError("Could not copy \(noticesName) to FirebaseCore for Carthage build. \(error)")
        }
      }

      // Hash the contents of the directory to get a unique name for Carthage.
      let hash: String
      do {
        // Only use the first 16 characters, that's what we did before.
        let fullHash = try HashCalculator.sha256Contents(ofDir: fullPath)
        hash = String(fullHash.prefix(16))
      } catch {
        fatalError("Could not hash contents of \(product) for Carthage build. \(error)")
      }

      // Generate the zip name to write to the manifest as well as the actual zip file.
      let zipName = "\(product)-\(hash).zip"
      let productZip = outputDir.appendingPathComponent(zipName)
      let zipped = Zip.zipContents(ofDir: fullPath, name: zipName)

      do {
        try FileManager.default.moveItem(at: zipped, to: productZip)
      } catch {
        fatalError("Could not move packaged zip file for \(product) during Carthage build. " +
          "\(error)")
      }

      // Force unwrapping because this can't fail at this point.
      let url =
        URL(string: "https://dl.google.com/dl/firebase/ios/carthage/\(firebaseVersion)/\(zipName)")!
      jsonManifest[firebaseVersion] = url

      // Write the updated manifest.
      let manifestPath = outputDir.appendingPathComponent(getJSONFileName(product: product))

      // Unfortunate workaround: There's a strange issue when serializing to JSON on macOS: URLs
      // will have the `/` escaped leading to an odd JSON output. Instead, let's output the
      // dictionary to a String and write that to disk. When Xcode 11 can be used, use a JSON
      // encoder with the `.withoutEscapingSlashes` option on `outputFormatting` like this:
//      do {
//        let encoder = JSONEncoder()
//        encoder.outputFormatting = [.sortedKeys, .prettyPrinted, .withoutEscapingSlashes]
//        let encodedManifest = try encoder.encode(jsonManifest)
//      catch { /* handle error */ }

      // Sort the manifest based on the key, $0 and $1 are the parameters and 0 is the first item in
      // the tuple (key).
      let sortedManifest = jsonManifest.sorted { $0.0 < $1.0 }

      // Generate the JSON format and combine all the lines afterwards.
      let manifestLines = sortedManifest.map { version, url -> String in
        // Two spaces at the beginning of the String are intentional.
        "  \"\(version)\": \"\(url.absoluteString)\""
      }

      // Join all the lines with a comma and newline to make things easier to read.
      let contents = "{\n" + manifestLines.joined(separator: ",\n") + "\n}\n"
      guard let encodedManifest = contents.data(using: .utf8) else {
        fatalError("Could not encode Carthage JSON manifest for \(product) - UTF8 encoding failed.")
      }

      do {
        try encodedManifest.write(to: manifestPath)
        print("Successfully written Carthage JSON manifest for \(product).")
      } catch {
        fatalError("Could not write new Carthage JSON manifest to disk for \(product). \(error)")
      }
    }
  }

  /// Creates a fake Firebase.framework to use the module for `import Firebase` compatibility.
  ///
  /// - Parameters:
  ///   - version: Firebase version.
  ///   - destination: The destination directory for the Firebase framework.
  ///   - rootDir: The root directory that contains other required files (like the Firebase header).
  ///   - templateDir: The template directory containing the dummy Firebase library.
  private static func createFirebaseFramework(version: String,
                                              inDir destination: URL,
                                              rootDir: URL,
                                              templateDir: URL) {
    // Local FileManager for better readability.
    let fm = FileManager.default

    let frameworkDir = destination.appendingPathComponent("Firebase.framework")
    let headersDir = frameworkDir.appendingPathComponent("Headers")
    let modulesDir = frameworkDir.appendingPathComponent("Modules")

    // Create all the required directories.
    do {
      try fm.createDirectory(at: headersDir, withIntermediateDirectories: true)
      try fm.createDirectory(at: modulesDir, withIntermediateDirectories: true)
    } catch {
      fatalError("Could not create directories for Firebase framework in Carthage. \(error)")
    }

    // Copy the Firebase header and modulemap that was created in the Zip file.
    let header = rootDir.appendingPathComponent(Constants.ProjectPath.firebaseHeader)
    do {
      try fm.copyItem(at: header, to: headersDir.appendingPathComponent(header.lastPathComponent))

      // Generate the new modulemap since it differs from the Zip modulemap.
      let carthageModulemap = """
      framework module Firebase {
        header "Firebase.h"
        export *
      }
      """
      let modulemapPath = modulesDir.appendingPathComponent("module.modulemap")
      try carthageModulemap.write(to: modulemapPath, atomically: true, encoding: .utf8)
    } catch {
      fatalError("Couldn't write required files for Firebase framework in Carthage. \(error)")
    }

    // Copy the dummy Firebase library.
    let dummyLib = templateDir.appendingPathComponent(Constants.ProjectPath.dummyFirebaseLib)
    do {
      try fm.copyItem(at: dummyLib, to: frameworkDir.appendingPathComponent("Firebase"))
    } catch {
      fatalError("Couldn't copy dummy library for Firebase framework in Carthage. \(error)")
    }

    // Write the Info.plist.
    generatePlistContents(forName: "Firebase", withVersion: version, to: frameworkDir)
  }

  static func generatePlistContents(forName name: String,
                                    withVersion version: String,
                                    to location: URL) {
    let ver = version.components(separatedBy: "-")[0] // remove any version suffix.
    let plist: [String: String] = ["CFBundleIdentifier": "com.firebase.Firebase-\(name)",
                                   "CFBundleInfoDictionaryVersion": "6.0",
                                   "CFBundlePackageType": "FMWK",
                                   "CFBundleVersion": ver,
                                   "DTSDKName": "iphonesimulator11.2",
                                   "CFBundleExecutable": name,
                                   "CFBundleName": name]

    // Generate the data for an XML based plist.
    let encoder = PropertyListEncoder()
    encoder.outputFormat = .xml
    do {
      let data = try encoder.encode(plist)
      try data.write(to: location.appendingPathComponent("Info.plist"))
    } catch {
      fatalError("Failed to create Info.plist for \(name) during Carthage build: \(error)")
    }
  }

  /// Parses the JSON manifest for the particular product.
  ///
  /// - Parameters:
  ///   - dir: The directory containing all JSON manifests.
  ///   - product: The name of the Firebase product.
  /// - Returns: A dictionary with versions as keys and URLs as values.
  private static func parseJSONFile(fromDir dir: URL, product: String) -> [String: URL] {
    // Parse the JSON manifest.
    let jsonFileName = getJSONFileName(product: product)
    let jsonFile = dir.appendingPathComponent(jsonFileName)
    guard FileManager.default.fileExists(atPath: jsonFile.path) else {
      fatalError("Could not find JSON manifest for \(product) during Carthage build. " +
        "Location: \(jsonFile)")
    }

    let jsonData: Data
    do {
      jsonData = try Data(contentsOf: jsonFile)
    } catch {
      fatalError("Could not read JSON manifest for \(product) during Carthage build. " +
        "Location: \(jsonFile). \(error)")
    }

    // Get a dictionary out of the file.
    let decoder = JSONDecoder()
    do {
      let productReleases = try decoder.decode([String: URL].self, from: jsonData)
      return productReleases
    } catch {
      fatalError("Could not parse JSON manifest for \(product) during Carthage build. " +
        "Location: \(jsonFile). \(error)")
    }
  }

  /// Get the JSON filename for a product
  /// Consider using just the product name post Firebase 7. The conditions are to handle Firebase 6 compatibility.
  ///
  /// - Parameters:
  ///   - product: The name of the Firebase product.
  /// - Returns: JSON file name for a product.
  private static func getJSONFileName(product: String) -> String {
    var jsonFileName: String
    if product == "GoogleSignIn" {
      jsonFileName = "FirebaseGoogleSignIn"
    } else if product == "Google-Mobile-Ads-SDK" {
      jsonFileName = "FirebaseAdMob"
    } else {
      jsonFileName = product
    }
    return jsonFileName + "Binary.json"
  }
}