discord: use distro layout on Darwin

pkgs/applications/networking/instant-messengers/discord/darwin.nix

@@ -8,9 +8,10 @@
   self,
   lib,
   fetchurl,
-  undmg,
   makeWrapper,
   writeScript,
+  writeShellScript,
+  brotli,
   python3,
   runCommand,
   branch,
@@ -34,7 +35,45 @@ let
   enabledDiscordModsCount = builtins.length (lib.filter (x: x) discordMods);
 
   inherit (source) version;
-  src = fetchurl { inherit (source) url hash; };
+
+  src = fetchurl { inherit (source.distro) url hash; };
+
+  moduleSrcs = lib.mapAttrs (_: mod: fetchurl { inherit (mod) url hash; }) source.modules;
+
+  moduleVersions = lib.mapAttrs (_: mod: mod.version) source.modules;
+
+  configDirName = lib.replaceStrings [ " " ] [ "" ] (lib.toLower binaryName);
+
+  fixDistroSymlinks = writeScript "discord-fix-distro-symlinks.py" ''
+    #!${python3.interpreter}
+    import pathlib
+    import sys
+    import tarfile
+
+    with tarfile.open(sys.argv[1]) as tar:
+        for member in tar:
+            if not member.issym():
+                continue
+            parts = pathlib.PurePosixPath(member.name).parts[1:]
+            if not parts:
+                continue
+            path = pathlib.Path(sys.argv[2], *parts)
+            path.unlink(missing_ok=True)
+            path.symlink_to(member.linkname)
+  '';
+
+  stageModules = writeShellScript "discord-stage-modules" ''
+    store_modules="$1"
+    modules_dir="$HOME/Library/Application Support/${configDirName}/${version}/modules"
+    if [ ! -f "$modules_dir/installed.json" ]; then
+      mkdir -p "$modules_dir"
+      for m in ${lib.concatStringsSep " " (lib.attrNames moduleSrcs)}; do
+        ln -sfn "$store_modules/$m" "$modules_dir/$m"
+      done
+      echo '${builtins.toJSON (lib.mapAttrs (_: mod: { installedVersion = mod; }) moduleVersions)}' \
+        > "$modules_dir/installed.json"
+    fi
+  '';
 
   disableBreakingUpdates =
     runCommand "disable-breaking-updates.py"
@@ -62,22 +101,47 @@ stdenv.mkDerivation {
     ;
 
   nativeBuildInputs = [
-    undmg
+    brotli
     makeWrapper
   ];
 
   sourceRoot = ".";
 
+  dontUnpack = true;
+
   installPhase = ''
     runHook preInstall
 
     mkdir -p $out/Applications
-    cp -r "${desktopName}.app" $out/Applications
+
+    extractDistro() {
+      local src="$1"
+      local dest="$2"
+      local tarball
+      tarball=$(mktemp)
+      brotli -d < "$src" > "$tarball"
+      tar xf "$tarball" --strip-components=1 -C "$dest"
+
+      # Discord's distro tarballs store symlinks with mode 000, which makes
+      # them unreadable on Darwin. Recreate them with normal permissions.
+      ${fixDistroSymlinks} "$tarball" "$dest"
+      rm "$tarball"
+    }
+
+    extractDistro "$src" "$out/Applications"
+
+    ${lib.concatStringsSep "\n" (
+      lib.mapAttrsToList (name: src: ''
+        mkdir -p "$out/Applications/${desktopName}.app/Contents/Resources/modules/${name}"
+        extractDistro ${src} "$out/Applications/${desktopName}.app/Contents/Resources/modules/${name}"
+      '') moduleSrcs
+    )}
 
     # wrap executable to $out/bin
     mkdir -p $out/bin
     makeWrapper "$out/Applications/${desktopName}.app/Contents/MacOS/${binaryName}" "$out/bin/${binaryName}" \
       --run ${lib.getExe disableBreakingUpdates} \
+      --run "${stageModules} $out/Applications/${desktopName}.app/Contents/Resources/modules" \
       --add-flags ${lib.escapeShellArg commandLineArgs}
 
     runHook postInstall