1 files changed, 276 insertions, 0 deletions
diff --git a/lang/lua/astal/variable.lua b/lang/lua/astal/variable.lua
new file mode 100644
index 0000000..5a5e169
--- /dev/null
+++ b/lang/lua/astal/variable.lua
@@ -0,0 +1,276 @@
+local lgi = require("lgi")
+local Astal = lgi.require("AstalIO", "0.1")
+local GObject = lgi.require("GObject", "2.0")
+local Binding = require("astal.binding")
+local Time = require("astal.time")
+local Process = require("astal.process")
+
+---@class Variable
+---@field private variable table
+---@field private err_handler? function
+---@field private _value any
+---@field private _poll? table
+---@field private _watch? table
+---@field private poll_interval number
+---@field private poll_exec? string[] | string
+---@field private poll_transform? fun(next: any, prev: any): any
+---@field private poll_fn? function
+---@field private watch_transform? fun(next: any, prev: any): any
+---@field private watch_exec? string[] | string
+local Variable = {}
+Variable.__index = Variable
+
+---@param value any
+---@return Variable
+function Variable.new(value)
+    local v = Astal.VariableBase()
+    local variable = setmetatable({
+        variable = v,
+        _value = value,
+    }, Variable)
+    v.on_dropped = function()
+        variable:stop_watch()
+        variable:stop_watch()
+    end
+    v.on_error = function(_, err)
+        if variable.err_handler then
+            variable.err_handler(err)
+        end
+    end
+    return variable
+end
+
+---@param transform function
+---@return Binding
+function Variable:__call(transform)
+    if transform == nil then
+        transform = function(v)
+            return v
+        end
+        return Binding.new(self)
+    end
+    return Binding.new(self):as(transform)
+end
+
+function Variable:__tostring()
+    return "Variable<" .. tostring(self:get()) .. ">"
+end
+
+function Variable:get()
+    return self._value or nil
+end
+
+function Variable:set(value)
+    if value ~= self:get() then
+        self._value = value
+        self.variable:emit_changed()
+    end
+end
+
+function Variable:start_poll()
+    if self._poll ~= nil then
+        return
+    end
+
+    if self.poll_fn then
+        self._poll = Time.interval(self.poll_interval, function()
+            self:set(self.poll_fn(self:get()))
+        end)
+    elseif self.poll_exec then
+        self._poll = Time.interval(self.poll_interval, function()
+            Process.exec_async(self.poll_exec, function(out, err)
+                if err ~= nil then
+                    return self.variable.emit_error(err)
+                end
+                self:set(self.poll_transform(out, self:get()))
+            end)
+        end)
+    end
+end
+
+function Variable:start_watch()
+    if self._watch then
+        return
+    end
+
+    self._watch = Process.subprocess(self.watch_exec, function(out)
+        self:set(self.watch_transform(out, self:get()))
+    end, function(err)
+        self.variable.emit_error(err)
+    end)
+end
+
+function Variable:stop_poll()
+    if self._poll then
+        self._poll.cancel()
+    end
+    self._poll = nil
+end
+
+function Variable:stop_watch()
+    if self._watch then
+        self._watch.kill()
+    end
+    self._watch = nil
+end
+
+function Variable:is_polling()
+    return self._poll ~= nil
+end
+
+function Variable:is_watching()
+    return self._watch ~= nil
+end
+
+function Variable:drop()
+    self.variable.emit_dropped()
+end
+
+---@param callback function
+---@return Variable
+function Variable:on_dropped(callback)
+    self.variable.on_dropped = callback
+    return self
+end
+
+---@param callback function
+---@return Variable
+function Variable:on_error(callback)
+    self.err_handler = nil
+    self.variable.on_eror = function(_, err)
+        callback(err)
+    end
+    return self
+end
+
+---@param callback fun(value: any)
+---@return function
+function Variable:subscribe(callback)
+    local id = self.variable.on_changed:connect(function()
+        callback(self:get())
+    end)
+    return function()
+        GObject.signal_handler_disconnect(self.variable, id)
+    end
+end
+
+---@param interval number
+---@param exec string | string[] | function
+---@param transform? fun(next: any, prev: any): any
+function Variable:poll(interval, exec, transform)
+    if transform == nil then
+        transform = function(next)
+            return next
+        end
+    end
+    self:stop_poll()
+    self.poll_interval = interval
+    self.poll_transform = transform
+
+    if type(exec) == "function" then
+        self.poll_fn = exec
+        self.poll_exec = nil
+    else
+        self.poll_exec = exec
+        self.poll_fn = nil
+    end
+    self:start_poll()
+    return self
+end
+
+---@param exec string | string[]
+---@param transform? fun(next: any, prev: any): any
+function Variable:watch(exec, transform)
+    if transform == nil then
+        transform = function(next)
+            return next
+        end
+    end
+    self:stop_poll()
+    self.watch_exec = exec
+    self.watch_transform = transform
+    self:start_watch()
+    return self
+end
+
+---@param object table | table[]
+---@param sigOrFn string | fun(...): any
+---@param callback fun(...): any
+---@return Variable
+function Variable:observe(object, sigOrFn, callback)
+    local f
+    if type(sigOrFn) == "function" then
+        f = sigOrFn
+    elseif type(callback) == "function" then
+        f = callback
+    else
+        f = function()
+            return self:get()
+        end
+    end
+    local set = function(...)
+        self:set(f(...))
+    end
+
+    if type(sigOrFn) == "string" then
+        object["on_" .. sigOrFn]:connect(set)
+    else
+        for _, obj in ipairs(object) do
+            obj[1]["on_" .. obj[2]]:connect(set)
+        end
+    end
+    return self
+end
+
+---@param deps Variable | (Binding | Variable)[]
+---@param transform? fun(...): any
+---@return Variable
+function Variable.derive(deps, transform)
+    if type(transform) == "nil" then
+        transform = function(...)
+            return { ... }
+        end
+    end
+
+    if getmetatable(deps) == Variable then
+        local var = Variable.new(transform(deps:get()))
+        deps:subscribe(function(v)
+            var:set(transform(v))
+        end)
+        return var
+    end
+
+    for i, var in ipairs(deps) do
+        if getmetatable(var) == Variable then
+            deps[i] = Binding.new(var)
+        end
+    end
+
+    local update = function()
+        local params = {}
+        for i, binding in ipairs(deps) do
+            params[i] = binding:get()
+        end
+        return transform(table.unpack(params), 1, #deps)
+    end
+
+    local var = Variable.new(update())
+
+    local unsubs = {}
+    for i, b in ipairs(deps) do
+        unsubs[i] = b:subscribe(update)
+    end
+
+    var.variable.on_dropped = function()
+        for _, unsub in ipairs(unsubs) do
+            unsub()
+        end
+    end
+    return var
+end
+
+return setmetatable(Variable, {
+    __call = function(_, v)
+        return Variable.new(v)
+    end,
+})