feat(emacs): Add telega.el support r/199

Packages the telega-server binary and adds the required mode into
Emacs.

Unread message count is displayed in the modeline, which is neat.

Probably need to figure out some key bindings for this.

4 files changed, 30 insertions, 0 deletions

diff --git a/third_party/default.nix b/third_party/default.nix
index 1837cf26ca20..890b1777625f 100644
--- a/third_party/default.nix
+++ b/third_party/default.nix
@@ -69,6 +69,7 @@ let
       stdenv
       stern
       symlinkJoin
+      tdlib
       terraform_0_12
       thttpd
       tree
diff --git a/third_party/telega/default.nix b/third_party/telega/default.nix
new file mode 100644
index 000000000000..4fdf0667ff9f
--- /dev/null
+++ b/third_party/telega/default.nix
@@ -0,0 +1,22 @@
+# Telega is an Emacs client for Telegram. It requires a native server
+# component to run correctly, which is built by this derivation.
+{ pkgs, ... }:
+
+with pkgs.third_party;
+
+stdenv.mkDerivation {
+  name = "telega";
+  buildInputs = [ tdlib ];
+
+  src = fetchFromGitHub {
+    owner = "zevlg";
+    repo = "telega.el";
+    rev = "d532b16067cf24728a2aa03a7aeaebe2ceac7df4";
+    sha256 = "1s2sd07sin9sy833wqprhbfk5j1d1s4azzvj6d8k68sxlgz8996m";
+  } + "/server";
+
+  installPhase = ''
+    mkdir -p $out/bin
+    mv telega-server $out/bin/
+  '';
+}
diff --git a/tools/emacs/config/init.el b/tools/emacs/config/init.el
index d601efa67df9..0be9a33963bf 100644
--- a/tools/emacs/config/init.el
+++ b/tools/emacs/config/init.el
@@ -171,6 +171,7 @@
 (use-package nix-util)
 (use-package nginx-mode)
 (use-package rust-mode)
+(use-package telega :config (telega-mode-line-mode 1))
 (use-package terraform-mode)
 (use-package toml-mode)
 (use-package web-mode)
diff --git a/tools/emacs/default.nix b/tools/emacs/default.nix
index c44403e6d692..d36673e363f4 100644
--- a/tools/emacs/default.nix
+++ b/tools/emacs/default.nix
@@ -11,6 +11,9 @@ let
   localPackages = pkgs.tools.emacs-pkgs;
   emacsWithPackages = (third_party.emacsPackagesNgGen third_party.emacs26).emacsWithPackages;
 
+  # $PATH for binaries that need to be available to Emacs
+  emacsBinPath = lib.makeBinPath [ third_party.telega ];
+
   identity = x: x;
   tazjinsEmacs = pkgfun: (emacsWithPackages(epkgs: pkgfun(
   # Actual ELPA packages (the enlightened!)
@@ -68,6 +71,7 @@ let
     sly
     string-edit
     swiper
+    telega
     telephone-line
     terraform-mode
     toml-mode
@@ -90,6 +94,7 @@ let
     term-switcher
   ]))));
 in lib.fix(self: l: f: third_party.writeShellScriptBin "tazjins-emacs" ''
+  export PATH="${emacsBinPath}:$PATH"
   exec ${tazjinsEmacs f}/bin/emacs \
     --debug-init \
     --no-site-file \
@@ -109,6 +114,7 @@ in lib.fix(self: l: f: third_party.writeShellScriptBin "tazjins-emacs" ''
     # Build a derivation that uses the specified local Emacs (i.e.
     # built outside of Nix) instead
     withLocalEmacs = emacsBin: third_party.writeShellScriptBin "tazjins-emacs" ''
+      export PATH="${emacsBinPath}:$PATH"
       export EMACSLOADPATH="${(tazjinsEmacs f).deps}/share/emacs/site-lisp:"
       exec ${emacsBin} \
         --debug-init \