src: Allow hooks to be run only once

This commit implements the -once flag on the `:hook` command, which
automatically removes a hook after it was run, to avoid having to
declare a group and remove it in the hook implementation.

Closes #2277

src/commands.cc

@@ -842,7 +842,8 @@ const CommandDesc add_hook_cmd = {
     "  * window: hook is executed only for the current window\n",
     ParameterDesc{
         { { "group", { true, "set hook group, see remove-hooks" } },
-          { "always", { false, "run hook even if hooks are disabled" } }},
+          { "always", { false, "run hook even if hooks are disabled" } },
+          { "once", { false, "run the hook only once" } } },
         ParameterDesc::Flags::None, 4, 4
     },
     CommandFlags::None,
@@ -860,9 +861,9 @@ const CommandDesc add_hook_cmd = {
         Regex regex{parser[2], RegexCompileFlags::Optimize};
         const String& command = parser[3];
         auto group = parser.get_switch("group").value_or(StringView{});
-        get_scope(parser[0], context).hooks().add_hook(parser[1], group.str(),
+        const auto flags = (parser.get_switch("always") ? HookFlags::Always : HookFlags::None) \
-                                                       parser.get_switch("always") ?
+                            | (parser.get_switch("once") ? HookFlags::Once : HookFlags::None);
-                                                       HookFlags::Always : HookFlags::None,
+        get_scope(parser[0], context).hooks().add_hook(parser[1], group.str(), flags,
                                                        std::move(regex), command);
     }
 };

src/hook_manager.cc

@@ -63,7 +63,7 @@ CandidateList HookManager::complete_hook_group(StringView prefix, ByteCount pos_
     return res;
 }
 
-void HookManager::run_hook(StringView hook_name, StringView param, Context& context) const
+void HookManager::run_hook(StringView hook_name, StringView param, Context& context)
 {
     const bool only_always = context.hooks_disabled();
 
@@ -123,6 +123,16 @@ void HookManager::run_hook(StringView hook_name, StringView param, Context& cont
 
             CommandManager::instance().execute(to_run.hook->commands, context,
                                                { {}, std::move(env_vars) });
+
+            if (to_run.hook->flags & HookFlags::Once)
+            {
+                auto it = std::find_if(hook_list->value.begin(), hook_list->value.end(),
+                                       [&](const std::unique_ptr<Hook>& h)
+                                       { return h.get() == to_run.hook; });
+
+                m_hooks_trash.push_back(std::move(*it));
+                hook_list->value.erase(it);
+            }
         }
         catch (runtime_error& err)
         {

src/hook_manager.hh

@@ -14,7 +14,8 @@ class Regex;
 enum class HookFlags
 {
     None = 0,
-    Always = 1 << 0
+    Always = 1 << 0,
+    Once = 1 << 1
 };
 constexpr bool with_bit_ops(Meta::Type<HookFlags>) { return true; }
 
@@ -29,7 +30,7 @@ public:
     void remove_hooks(StringView group);
     CandidateList complete_hook_group(StringView prefix, ByteCount pos_in_token);
     void run_hook(StringView hook_name, StringView param,
-                  Context& context) const;
+                  Context& context);
 
 private:
     HookManager();