nixos/mantisbt: add a simple service

It doesn't really deserve a package, as it's just a bunch of PHP scripts
copied into a folder and we have to copy on reconfiguration anyway.

nixos/modules/module-list.nix

@@ -220,6 +220,7 @@
   ./services/misc/gitolite.nix
   ./services/misc/gpsd.nix
   ./services/misc/ihaskell.nix
+  ./services/misc/mantisbt.nix
   ./services/misc/mathics.nix
   ./services/misc/matrix-synapse.nix
   ./services/misc/mbpfan.nix

nixos/modules/services/misc/mantisbt.nix

@@ -0,0 +1,68 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+let
+  cfg = config.services.mantisbt;
+
+  freshInstall = cfg.extraConfig == "";
+
+  # combined code+config directory
+  mantisbt = let
+    config_inc = pkgs.writeText "config_inc.php" ("<?php\n" + cfg.extraConfig);
+    src = pkgs.fetchurl {
+      url = "mirror://sourceforge/mantisbt/${name}.tar.gz";
+      sha256 = "1pl6xn793p3mxc6ibpr2bhg85vkdlcf57yk7pfc399g47l8x4508";
+    };
+    name = "mantisbt-1.2.19";
+    in
+      # We have to copy every time; otherwise config won't be found.
+      pkgs.runCommand name
+        { preferLocalBuild = true; allowSubstitutes = false; }
+        (''
+          mkdir -p "$out"
+          cd "$out"
+          tar -xf '${src}' --strip-components=1
+          ln -s '${config_inc}' config_inc.php
+        ''
+        + lib.optionalString (!freshInstall) "rm -r admin/"
+        );
+in
+{
+  options.services.mantisbt = {
+    enable = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Enable the mantisbt web service.
+        This switches on httpd with PHP and database.
+      '';
+    };
+    urlPrefix = mkOption {
+      type = types.string;
+      default = "/mantisbt";
+      description = "The URL prefix under which the mantisbt service appears.";
+    };
+    extraConfig = mkOption {
+      type = types.lines;
+      default = "";
+      description = ''
+        The contents of config_inc.php, without leading <?php.
+        If left empty, the admin directory will be accessible.
+      '';
+    };
+  };
+
+
+  config = mkIf cfg.enable {
+    services.mysql.enable = true;
+    services.httpd.enable = true;
+    services.httpd.enablePHP = true;
+    # The httpd sub-service showing mantisbt.
+    services.httpd.extraSubservices = [ { function = { ... }: {
+      extraConfig =
+        ''
+          Alias ${cfg.urlPrefix} "${mantisbt}"
+        '';
+    };}];
+  };
+}