inital support for hooks...

Currently the following hooks are available:
 - WinMapPre
 - WinMapPost

src/types/events.zig

@@ -0,0 +1,56 @@
+pub const Events = @This();
+
+const std = @import("std");
+
+const Hook = @import("hook.zig");
+
+const Node = struct {
+  hook: *const Hook,
+  node: std.SinglyLinkedList.Node,
+};
+
+events: std.StringHashMap(*std.SinglyLinkedList),
+allocator: std.mem.Allocator,
+
+pub fn init(allocator: std.mem.Allocator) !Events {
+  return Events{
+    .allocator = allocator,
+    .events = .init(allocator),
+  };
+}
+
+pub fn put(self: *Events, key: []const u8, hook: *const Hook) !void {
+  var ll: *std.SinglyLinkedList = undefined;
+  if (self.events.get(key)) |sll| {
+    ll = sll;
+  } else {
+    ll = try self.allocator.create(std.SinglyLinkedList);
+    try self.events.put(key, ll);
+    if (self.events.get(key)) |sll| {
+      ll = sll;
+    }
+  }
+  const data = try self.allocator.create(Node);
+  data.* = .{
+    .hook = hook,
+    .node = .{},
+  };
+  ll.prepend(&data.node);
+}
+
+// TODO: figure out deletion
+// pub fn del(self: *Events, key: ???) !void {}
+
+pub fn exec(self: *Events, event: []const u8) void {
+  if (self.events.get(event)) |e| {
+    var node = e.first;
+    while (node) |n| : (node = n.next) {
+      const data: *Node = @fieldParentPtr("node", n);
+      data.hook.callback();
+
+      // FIXME: not sure why but for some reason our ll doesn't seem to want to
+      // admit that there's nothing after the first node.
+      break;
+    }
+  }
+}

src/types/hook.zig

@@ -0,0 +1,32 @@
+//! This is a simple way to define a hook.
+const Hook = @This();
+
+const std = @import("std");
+
+const xkb = @import("xkbcommon");
+const wlr = @import("wlroots");
+const zlua = @import("zlua");
+
+const Event = @import("events.zig");
+const Lua = &@import("../main.zig").lua;
+
+events: std.ArrayList([]const u8), // a list of events
+options: struct {
+  // group: []const u8, // TODO: do we need groups?
+  /// This is the location of the callback lua function in the lua registry
+  lua_cb_ref_idx: i32,
+},
+
+pub fn callback(self: *const Hook) void {
+  const t = Lua.state.rawGetIndex(zlua.registry_index, self.options.lua_cb_ref_idx);
+  if (t != zlua.LuaType.function) {
+    std.log.err("Failed to call hook, it doesn't have a callback.", .{});
+    Lua.state.pop(1);
+    return;
+  }
+
+  // TODO: we need to send some data along with the callback, this data will
+  // change based on the event which the user is hooking into
+  Lua.state.call(.{ .args = 0, .results = 0 });
+  Lua.state.pop(-1);
+}