From b2c2944998b3d237c900bbcd95734363d4203cb8 Mon Sep 17 00:00:00 2001
From: Christopher Singley <csingley@gmail.com>
Date: Sun, 29 Oct 2017 19:37:56 -0500
Subject: nzbget.service override nzbget.conf broken paths with current
 derivation

---
 nixos/modules/services/misc/nzbget.nix | 47 +++++++++++++++++++++++-----------
 1 file changed, 32 insertions(+), 15 deletions(-)

diff --git a/nixos/modules/services/misc/nzbget.nix b/nixos/modules/services/misc/nzbget.nix
index b39511624c8..a186d57ceba 100644
--- a/nixos/modules/services/misc/nzbget.nix
+++ b/nixos/modules/services/misc/nzbget.nix
@@ -4,9 +4,7 @@ with lib;
 
 let
   cfg = config.services.nzbget;
-  nzbget = pkgs.nzbget;
-in
-{
+  nzbget = pkgs.nzbget; in {
   options = {
     services.nzbget = {
       enable = mkEnableOption "NZBGet";
@@ -42,21 +40,41 @@ in
         p7zip
       ];
       preStart = ''
-        test -d /var/lib/nzbget || {
-          echo "Creating nzbget state directoy in /var/lib/"
-          mkdir -p /var/lib/nzbget
+        datadir=/var/lib/nzbget
+        cfgtemplate=${cfg.package}/share/nzbget/nzbget.conf
+        test -d $datadir || {
+          echo "Creating nzbget data directory in $datadir"
+          mkdir -p $datadir
         }
-        test -f /var/lib/nzbget/nzbget.conf || {
-          echo "nzbget.conf not found. Copying default config to /var/lib/nzbget/nzbget.conf"
-          cp ${cfg.package}/share/nzbget/nzbget.conf /var/lib/nzbget/nzbget.conf
-          echo "Setting file mode of nzbget.conf to 0700 (needs to be written and contains plaintext credentials)"
-          chmod 0700 /var/lib/nzbget/nzbget.conf
+        test -f $configfile || {
+          echo "nzbget.conf not found. Copying default config $cfgtemplate to $configfile"
+          cp $cfgtemplate $configfile
+          echo "Setting $configfile permissions to 0700 (needs to be written and contains plaintext credentials)"
+          chmod 0700 $configfile
           echo "Setting temporary \$MAINDIR variable in default config required in order to allow nzbget to complete initial start"
           echo "Remember to change this to a proper value once NZBGet startup has been completed"
-          sed -i -e 's/MainDir=.*/MainDir=\/tmp/g' /var/lib/nzbget/nzbget.conf
+          sed -i -e 's/MainDir=.*/MainDir=\/tmp/g' $configfile
         }
-        echo "Ensuring proper ownership of /var/lib/nzbget (${cfg.user}:${cfg.group})."
-        chown -R ${cfg.user}:${cfg.group} /var/lib/nzbget
+        echo "Ensuring proper ownership of $datadir (${cfg.user}:${cfg.group})."
+        chown -R ${cfg.user}:${cfg.group} $datadir
+      '';
+
+      script = ''
+        configfile=/var/lib/nzbget/nzbget.conf
+        args="--daemon --configfile $configfile"
+        # The script in preStart (above) copies nzbget's config template to datadir on first run, containing paths that point to the nzbget derivation installed at the time. 
+        # These paths break when nzbget is upgraded & the original derivation is garbage collected. If such broken paths are found in the config file, override them to point to 
+        # the currently installed nzbget derivation.
+        cfgfallback () {
+          local hit=`grep -Po "(?<=^$1=).*+" "$configfile" | sed 's/[ \t]*$//'` # Strip trailing whitespace
+          ( test $hit && test -e $hit ) || {
+            echo "In $configfile, valid $1 not found; falling back to $1=$2"
+            args+=" -o $1=$2"
+          }
+        }
+        cfgfallback ConfigTemplate ${cfg.package}/share/nzbget/nzbget.conf
+        cfgfallback WebDir ${cfg.package}/share/nzbget/webui
+        ${cfg.package}/bin/nzbget $args
       '';
 
       serviceConfig = {
@@ -64,7 +82,6 @@ in
         User = cfg.user;
         Group = cfg.group;
         PermissionsStartOnly = "true";
-        ExecStart = "${cfg.package}/bin/nzbget --daemon --configfile /var/lib/nzbget/nzbget.conf";
         Restart = "on-failure";
       };
     };
-- 
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