# This file originates from node2nix
{
  lib,
  stdenv,
  nodejs,
  python2,
  pkgs,
  libtool,
  runCommand,
  writeTextFile,
  writeShellScript,
}: let
  # Workaround to cope with utillinux in Nixpkgs 20.09 and util-linux in Nixpkgs master
  utillinux =
    if pkgs ? utillinux
    then pkgs.utillinux
    else pkgs.util-linux;

  python =
    if nodejs ? python
    then nodejs.python
    else python2;

  # Create a tar wrapper that filters all the 'Ignoring unknown extended header keyword' noise
  tarWrapper = runCommand "tarWrapper" {} ''
    mkdir -p $out/bin

    cat > $out/bin/tar <<EOF
    #! ${stdenv.shell} -e
    $(type -p tar) "\$@" --warning=no-unknown-keyword --delay-directory-restore
    EOF

    chmod +x $out/bin/tar
  '';

  # Function that generates a TGZ file from a NPM project
  buildNodeSourceDist = {
    name,
    version,
    src,
    ...
  }:
    stdenv.mkDerivation {
      name = "node-tarball-${name}-${version}";
      inherit src;
      buildInputs = [nodejs];
      buildPhase = ''
        export HOME=$TMPDIR
        tgzFile=$(npm pack | tail -n 1) # Hooks to the pack command will add output (https://docs.npmjs.com/misc/scripts)
      '';
      installPhase = ''
        mkdir -p $out/tarballs
        mv $tgzFile $out/tarballs
        mkdir -p $out/nix-support
        echo "file source-dist $out/tarballs/$tgzFile" >> $out/nix-support/hydra-build-products
      '';
    };

  # Common shell logic
  installPackage = writeShellScript "install-package" ''
    installPackage() {
      local packageName=$1 src=$2

      local strippedName

      local DIR=$PWD
      cd $TMPDIR

      unpackFile $src

      # Make the base dir in which the target dependency resides first
      mkdir -p "$(dirname "$DIR/$packageName")"

      if [ -f "$src" ]
      then
          # Figure out what directory has been unpacked
          packageDir="$(find . -maxdepth 1 -type d | tail -1)"

          # Restore write permissions to make building work
          find "$packageDir" -type d -exec chmod u+x {} \;
          chmod -R u+w "$packageDir"

          # Move the extracted tarball into the output folder
          mv "$packageDir" "$DIR/$packageName"
      elif [ -d "$src" ]
      then
          # Get a stripped name (without hash) of the source directory.
          # On old nixpkgs it's already set internally.
          if [ -z "$strippedName" ]
          then
              strippedName="$(stripHash $src)"
          fi

          # Restore write permissions to make building work
          chmod -R u+w "$strippedName"

          # Move the extracted directory into the output folder
          mv "$strippedName" "$DIR/$packageName"
      fi

      # Change to the package directory to install dependencies
      cd "$DIR/$packageName"
    }
  '';

  # Bundle the dependencies of the package
  #
  # Only include dependencies if they don't exist. They may also be bundled in the package.
  includeDependencies = {dependencies}:
    lib.optionalString (dependencies != []) (
      ''
        mkdir -p node_modules
        cd node_modules
      ''
      + (lib.concatMapStrings (
          dependency: ''
            if [ ! -e "${dependency.packageName}" ]; then
                ${composePackage dependency}
            fi
          ''
        )
        dependencies)
      + ''
        cd ..
      ''
    );

  # Recursively composes the dependencies of a package
  composePackage = {
    name,
    packageName,
    src,
    dependencies ? [],
    ...
  } @ args:
    builtins.addErrorContext "while evaluating node package '${packageName}'" ''
      installPackage "${packageName}" "${src}"
      ${includeDependencies {inherit dependencies;}}
      cd ..
      ${lib.optionalString (builtins.substring 0 1 packageName == "@") "cd .."}
    '';

  pinpointDependencies = {
    dependencies,
    production,
  }: let
    pinpointDependenciesFromPackageJSON = writeTextFile {
      name = "pinpointDependencies.js";
      text = ''
        var fs = require('fs');
        var path = require('path');

        function resolveDependencyVersion(location, name) {
            if(location == process.env['NIX_STORE']) {
                return null;
            } else {
                var dependencyPackageJSON = path.join(location, "node_modules", name, "package.json");

                if(fs.existsSync(dependencyPackageJSON)) {
                    var dependencyPackageObj = JSON.parse(fs.readFileSync(dependencyPackageJSON));

                    if(dependencyPackageObj.name == name) {
                        return dependencyPackageObj.version;
                    }
                } else {
                    return resolveDependencyVersion(path.resolve(location, ".."), name);
                }
            }
        }

        function replaceDependencies(dependencies) {
            if(typeof dependencies == "object" && dependencies !== null) {
                for(var dependency in dependencies) {
                    var resolvedVersion = resolveDependencyVersion(process.cwd(), dependency);

                    if(resolvedVersion === null) {
                        process.stderr.write("WARNING: cannot pinpoint dependency: "+dependency+", context: "+process.cwd()+"\n");
                    } else {
                        dependencies[dependency] = resolvedVersion;
                    }
                }
            }
        }

        /* Read the package.json configuration */
        var packageObj = JSON.parse(fs.readFileSync('./package.json'));

        /* Pinpoint all dependencies */
        replaceDependencies(packageObj.dependencies);
        if(process.argv[2] == "development") {
            replaceDependencies(packageObj.devDependencies);
        }
        replaceDependencies(packageObj.optionalDependencies);

        /* Write the fixed package.json file */
        fs.writeFileSync("package.json", JSON.stringify(packageObj, null, 2));
      '';
    };
  in ''
    node ${pinpointDependenciesFromPackageJSON} ${
      if production
      then "production"
      else "development"
    }

    ${lib.optionalString (dependencies != [])
      ''
        if [ -d node_modules ]
        then
            cd node_modules
            ${lib.concatMapStrings (dependency: pinpointDependenciesOfPackage dependency) dependencies}
            cd ..
        fi
      ''}
  '';

  # Recursively traverses all dependencies of a package and pinpoints all
  # dependencies in the package.json file to the versions that are actually
  # being used.

  pinpointDependenciesOfPackage = {
    packageName,
    dependencies ? [],
    production ? true,
    ...
  } @ args: ''
    if [ -d "${packageName}" ]
    then
        cd "${packageName}"
        ${pinpointDependencies {inherit dependencies production;}}
        cd ..
        ${lib.optionalString (builtins.substring 0 1 packageName == "@") "cd .."}
    fi
  '';

  # Extract the Node.js source code which is used to compile packages with
  # native bindings
  nodeSources = runCommand "node-sources" {} ''
    tar --no-same-owner --no-same-permissions -xf ${nodejs.src}
    mv node-* $out
  '';

  # Script that adds _integrity fields to all package.json files to prevent NPM from consulting the cache (that is empty)
  addIntegrityFieldsScript = writeTextFile {
    name = "addintegrityfields.js";
    text = ''
      var fs = require('fs');
      var path = require('path');

      function augmentDependencies(baseDir, dependencies) {
          for(var dependencyName in dependencies) {
              var dependency = dependencies[dependencyName];

              // Open package.json and augment metadata fields
              var packageJSONDir = path.join(baseDir, "node_modules", dependencyName);
              var packageJSONPath = path.join(packageJSONDir, "package.json");

              if(fs.existsSync(packageJSONPath)) { // Only augment packages that exist. Sometimes we may have production installs in which development dependencies can be ignored
                  console.log("Adding metadata fields to: "+packageJSONPath);
                  var packageObj = JSON.parse(fs.readFileSync(packageJSONPath));

                  if(dependency.integrity) {
                      packageObj["_integrity"] = dependency.integrity;
                  } else {
                      packageObj["_integrity"] = "sha1-000000000000000000000000000="; // When no _integrity string has been provided (e.g. by Git dependencies), add a dummy one. It does not seem to harm and it bypasses downloads.
                  }

                  if(dependency.resolved) {
                      packageObj["_resolved"] = dependency.resolved; // Adopt the resolved property if one has been provided
                  } else {
                      packageObj["_resolved"] = dependency.version; // Set the resolved version to the version identifier. This prevents NPM from cloning Git repositories.
                  }

                  if(dependency.from !== undefined) { // Adopt from property if one has been provided
                      packageObj["_from"] = dependency.from;
                  }

                  fs.writeFileSync(packageJSONPath, JSON.stringify(packageObj, null, 2));
              }

              // Augment transitive dependencies
              if(dependency.dependencies !== undefined) {
                  augmentDependencies(packageJSONDir, dependency.dependencies);
              }
          }
      }

      if(fs.existsSync("./package-lock.json")) {
          var packageLock = JSON.parse(fs.readFileSync("./package-lock.json"));

          if(![1, 2].includes(packageLock.lockfileVersion)) {
            process.stderr.write("Sorry, I only understand lock file versions 1 and 2!\n");
            process.exit(1);
          }

          if(packageLock.dependencies !== undefined) {
              augmentDependencies(".", packageLock.dependencies);
          }
      }
    '';
  };

  # Reconstructs a package-lock file from the node_modules/ folder structure and package.json files with dummy sha1 hashes
  reconstructPackageLock = writeTextFile {
    name = "addintegrityfields.js";
    text = ''
      var fs = require('fs');
      var path = require('path');

      var packageObj = JSON.parse(fs.readFileSync("package.json"));

      var lockObj = {
          name: packageObj.name,
          version: packageObj.version,
          lockfileVersion: 1,
          requires: true,
          dependencies: {}
      };

      function augmentPackageJSON(filePath, dependencies) {
          var packageJSON = path.join(filePath, "package.json");
          if(fs.existsSync(packageJSON)) {
              var packageObj = JSON.parse(fs.readFileSync(packageJSON));
              dependencies[packageObj.name] = {
                  version: packageObj.version,
                  integrity: "sha1-000000000000000000000000000=",
                  dependencies: {}
              };
              processDependencies(path.join(filePath, "node_modules"), dependencies[packageObj.name].dependencies);
          }
      }

      function processDependencies(dir, dependencies) {
          if(fs.existsSync(dir)) {
              var files = fs.readdirSync(dir);

              files.forEach(function(entry) {
                  var filePath = path.join(dir, entry);
                  var stats = fs.statSync(filePath);

                  if(stats.isDirectory()) {
                      if(entry.substr(0, 1) == "@") {
                          // When we encounter a namespace folder, augment all packages belonging to the scope
                          var pkgFiles = fs.readdirSync(filePath);

                          pkgFiles.forEach(function(entry) {
                              if(stats.isDirectory()) {
                                  var pkgFilePath = path.join(filePath, entry);
                                  augmentPackageJSON(pkgFilePath, dependencies);
                              }
                          });
                      } else {
                          augmentPackageJSON(filePath, dependencies);
                      }
                  }
              });
          }
      }

      processDependencies("node_modules", lockObj.dependencies);

      fs.writeFileSync("package-lock.json", JSON.stringify(lockObj, null, 2));
    '';
  };

  prepareAndInvokeNPM = {
    packageName,
    bypassCache,
    reconstructLock,
    npmFlags,
    production,
  }: let
    forceOfflineFlag =
      if bypassCache
      then "--offline"
      else "--registry http://www.example.com";
  in ''
    # Pinpoint the versions of all dependencies to the ones that are actually being used
    echo "pinpointing versions of dependencies..."
    source $pinpointDependenciesScriptPath

    # Patch the shebangs of the bundled modules to prevent them from
    # calling executables outside the Nix store as much as possible
    patchShebangs .

    # Deploy the Node.js package by running npm install. Since the
    # dependencies have been provided already by ourselves, it should not
    # attempt to install them again, which is good, because we want to make
    # it Nix's responsibility. If it needs to install any dependencies
    # anyway (e.g. because the dependency parameters are
    # incomplete/incorrect), it fails.
    #
    # The other responsibilities of NPM are kept -- version checks, build
    # steps, postprocessing etc.

    export HOME=$TMPDIR
    cd "${packageName}"
    runHook preRebuild

    ${lib.optionalString bypassCache ''
      ${lib.optionalString reconstructLock ''
        if [ -f package-lock.json ]
        then
            echo "WARNING: Reconstruct lock option enabled, but a lock file already exists!"
            echo "This will most likely result in version mismatches! We will remove the lock file and regenerate it!"
            rm package-lock.json
        else
            echo "No package-lock.json file found, reconstructing..."
        fi

        node ${reconstructPackageLock}
      ''}

      node ${addIntegrityFieldsScript}
    ''}

    npm ${forceOfflineFlag} --nodedir=${nodeSources} ${npmFlags} ${lib.optionalString production "--production"} rebuild

    if [ "''${dontNpmInstall-}" != "1" ]
    then
        # NPM tries to download packages even when they already exist if npm-shrinkwrap is used.
        rm -f npm-shrinkwrap.json

        npm ${forceOfflineFlag} --nodedir=${nodeSources} ${npmFlags} ${lib.optionalString production "--production"} install
    fi
  '';

  # Builds and composes an NPM package including all its dependencies
  buildNodePackage = {
    name,
    packageName,
    version ? null,
    dependencies ? [],
    buildInputs ? [],
    production ? true,
    npmFlags ? "",
    dontNpmInstall ? false,
    bypassCache ? false,
    reconstructLock ? false,
    preRebuild ? "",
    dontStrip ? true,
    unpackPhase ? "true",
    buildPhase ? "true",
    meta ? {},
    ...
  } @ args: let
    extraArgs = removeAttrs args ["name" "dependencies" "buildInputs" "dontStrip" "dontNpmInstall" "preRebuild" "unpackPhase" "buildPhase" "meta"];
  in
    stdenv.mkDerivation ({
        name = "${name}${
          if version == null
          then ""
          else "-${version}"
        }";
        buildInputs =
          [tarWrapper python nodejs]
          ++ lib.optional (stdenv.isLinux) utillinux
          ++ lib.optional (stdenv.isDarwin) libtool
          ++ buildInputs;

        inherit nodejs;

        inherit dontStrip; # Stripping may fail a build for some package deployments
        inherit dontNpmInstall preRebuild unpackPhase buildPhase;

        compositionScript = composePackage args;
        pinpointDependenciesScript = pinpointDependenciesOfPackage args;

        passAsFile = ["compositionScript" "pinpointDependenciesScript"];

        installPhase = ''
          source ${installPackage}

          # Create and enter a root node_modules/ folder
          mkdir -p $out/lib/node_modules
          cd $out/lib/node_modules

          # Compose the package and all its dependencies
          source $compositionScriptPath

          ${prepareAndInvokeNPM {inherit packageName bypassCache reconstructLock npmFlags production;}}

          # Create symlink to the deployed executable folder, if applicable
          if [ -d "$out/lib/node_modules/.bin" ]
          then
              ln -s $out/lib/node_modules/.bin $out/bin

              # Patch the shebang lines of all the executables
              ls $out/bin/* | while read i
              do
                  file="$(readlink -f "$i")"
                  chmod u+rwx "$file"
                  patchShebangs "$file"
              done
          fi

          # Create symlinks to the deployed manual page folders, if applicable
          if [ -d "$out/lib/node_modules/${packageName}/man" ]
          then
              mkdir -p $out/share
              for dir in "$out/lib/node_modules/${packageName}/man/"*
              do
                  mkdir -p $out/share/man/$(basename "$dir")
                  for page in "$dir"/*
                  do
                      ln -s $page $out/share/man/$(basename "$dir")
                  done
              done
          fi

          # Run post install hook, if provided
          runHook postInstall
        '';

        meta =
          {
            # default to Node.js' platforms
            platforms = nodejs.meta.platforms;
          }
          // meta;
      }
      // extraArgs);

  # Builds a node environment (a node_modules folder and a set of binaries)
  buildNodeDependencies = {
    name,
    packageName,
    version ? null,
    src,
    dependencies ? [],
    buildInputs ? [],
    production ? true,
    npmFlags ? "",
    dontNpmInstall ? false,
    bypassCache ? false,
    reconstructLock ? false,
    dontStrip ? true,
    unpackPhase ? "true",
    buildPhase ? "true",
    ...
  } @ args: let
    extraArgs = removeAttrs args ["name" "dependencies" "buildInputs"];
  in
    stdenv.mkDerivation ({
        name = "node-dependencies-${name}${
          if version == null
          then ""
          else "-${version}"
        }";

        buildInputs =
          [tarWrapper python nodejs]
          ++ lib.optional (stdenv.isLinux) utillinux
          ++ lib.optional (stdenv.isDarwin) libtool
          ++ buildInputs;

        inherit dontStrip; # Stripping may fail a build for some package deployments
        inherit dontNpmInstall unpackPhase buildPhase;

        includeScript = includeDependencies {inherit dependencies;};
        pinpointDependenciesScript = pinpointDependenciesOfPackage args;

        passAsFile = ["includeScript" "pinpointDependenciesScript"];

        installPhase = ''
          source ${installPackage}

          mkdir -p $out/${packageName}
          cd $out/${packageName}

          source $includeScriptPath

          # Create fake package.json to make the npm commands work properly
          cp ${src}/package.json .
          chmod 644 package.json
          ${lib.optionalString bypassCache ''
            if [ -f ${src}/package-lock.json ]
            then
                cp ${src}/package-lock.json .
                chmod 644 package-lock.json
            fi
          ''}

          # Go to the parent folder to make sure that all packages are pinpointed
          cd ..
          ${lib.optionalString (builtins.substring 0 1 packageName == "@") "cd .."}

          ${prepareAndInvokeNPM {inherit packageName bypassCache reconstructLock npmFlags production;}}

          # Expose the executables that were installed
          cd ..
          ${lib.optionalString (builtins.substring 0 1 packageName == "@") "cd .."}

          mv ${packageName} lib
          ln -s $out/lib/node_modules/.bin $out/bin
        '';
      }
      // extraArgs);

  # Builds a development shell
  buildNodeShell = {
    name,
    packageName,
    version ? null,
    src,
    dependencies ? [],
    buildInputs ? [],
    production ? true,
    npmFlags ? "",
    dontNpmInstall ? false,
    bypassCache ? false,
    reconstructLock ? false,
    dontStrip ? true,
    unpackPhase ? "true",
    buildPhase ? "true",
    ...
  } @ args: let
    nodeDependencies = buildNodeDependencies args;
    extraArgs = removeAttrs args ["name" "dependencies" "buildInputs" "dontStrip" "dontNpmInstall" "unpackPhase" "buildPhase"];
  in
    stdenv.mkDerivation ({
        name = "node-shell-${name}${
          if version == null
          then ""
          else "-${version}"
        }";

        buildInputs = [python nodejs] ++ lib.optional (stdenv.isLinux) utillinux ++ buildInputs;
        buildCommand = ''
          mkdir -p $out/bin
          cat > $out/bin/shell <<EOF
          #! ${stdenv.shell} -e
          $shellHook
          exec ${stdenv.shell}
          EOF
          chmod +x $out/bin/shell
        '';

        # Provide the dependencies in a development shell through the NODE_PATH environment variable
        inherit nodeDependencies;
        shellHook = lib.optionalString (dependencies != []) ''
          export NODE_PATH=${nodeDependencies}/lib/node_modules
          export PATH="${nodeDependencies}/bin:$PATH"
        '';
      }
      // extraArgs);
in {
  buildNodeSourceDist = lib.makeOverridable buildNodeSourceDist;
  buildNodePackage = lib.makeOverridable buildNodePackage;
  buildNodeDependencies = lib.makeOverridable buildNodeDependencies;
  buildNodeShell = lib.makeOverridable buildNodeShell;
}
