1 files changed, 65 insertions, 0 deletions
diff --git a/core/lua/astal/binding.lua b/core/lua/astal/binding.lua
new file mode 100644
index 0000000..50509d1
--- /dev/null
+++ b/core/lua/astal/binding.lua
@@ -0,0 +1,65 @@
+local lgi = require("lgi")
+local GObject = lgi.require("GObject", "2.0")
+
+---@class Binding
+---@field emitter table|Variable
+---@field property? string
+---@field transformFn function
+local Binding = {}
+
+---@param emitter table
+---@param property? string
+---@return Binding
+function Binding.new(emitter, property)
+    return setmetatable({
+        emitter = emitter,
+        property = property,
+        transformFn = function(v)
+            return v
+        end,
+    }, Binding)
+end
+
+function Binding:__tostring()
+    local str = "Binding<" .. tostring(self.emitter)
+    if self.property ~= nil then
+        str = str .. ", " .. self.property
+    end
+    return str .. ">"
+end
+
+function Binding:get()
+    if type(self.emitter.get) == "function" then
+        return self.transformFn(self.emitter:get())
+    end
+    return self.transformFn(self.emitter[self.property])
+end
+
+---@param transform fun(value: any): any
+---@return Binding
+function Binding:as(transform)
+    local b = Binding.new(self.emitter, self.property)
+    b.transformFn = function(v)
+        return transform(self.transformFn(v))
+    end
+    return b
+end
+
+---@param callback fun(value: any)
+---@return function
+function Binding:subscribe(callback)
+    if type(self.emitter.subscribe) == "function" then
+        return self.emitter:subscribe(function()
+            callback(self:get())
+        end)
+    end
+    local id = self.emitter.on_notify:connect(function()
+        callback(self:get())
+    end, self.property, false)
+    return function()
+        GObject.signal_handler_disconnect(self.emitter, id)
+    end
+end
+
+Binding.__index = Binding
+return Binding