---------------------------------------------------------------------------
-- @author Lukáš Hrázký
-- @copyright 2012 Lukáš Hrázký
-- @release @AWESOME_VERSION@
---------------------------------------------------------------------------

local pairs = pairs
local type = type
local setmetatable = setmetatable
local base = require("wibox.layout.base")
local widget_base = require("wibox.widget.base")
local math = math

-- wibox.layout.constraint
local constraint = { mt = {} }

--- Draw a constraint layout
function constraint:draw(wibox, cr, width, height)
    if not self.widget then
        return
    end

    local w, h = self:fit(width, height)

    base.draw_widget(wibox, cr, self.widget, 0, 0, w, h)
end

--- Fit a constraint layout into the given space
function constraint:fit(width, height)
    local w, h
    if self.widget then
        w, h = self.widget:fit(width, height)
    else
        w, h = 0, 0
    end

    if self._width > 0 then
        if self.strategy == "exact" then
            w = self._width
        else
            w = math[self.strategy](w, self._width)
        end
    end

    if self._height > 0 then
        if self.strategy == "exact" then
            h = self._height
        else
            h = math[self.strategy](h, self._height)
        end
    end

    return w, h
end

--- Set the widget that this layout adds a constraint on.
function constraint:set_widget(widget)
    if self.widget then
        self.widget:disconnect_signal("widget::updated", self._emit_updated)
    end
    if widget then
        widget_base.check_widget(widget)
        widget:connect_signal("widget::updated", self._emit_updated)
    end
    self.widget = widget
    self:emit_signal("widget::updated")
end

--- Set the strategy to use for the constraining. Valid values are 'max',
-- 'min' or 'exact'. Throws an error on invalid values.
function constraint:set_strategy(val)
    local allowed = {
        max = true,
        min = true,
        exact = true
    }

    if not allowed[val] then
        error("Invalid strategy for constraint layout: " .. tostring(val))
    end

    self.strategy = val
    self:emit_signal("widget::updated")
end

--- Set the maximum width to val.
function constraint:set_width(val)
    self._width = val
    self:emit_signal("widget::updated")
end

--- Set the maximum height to val.
function constraint:set_height(val)
    self._height = val
    self:emit_signal("widget::updated")
end

--- Reset this layout. The widget will be unreferenced, strategy set to "max"
-- and the constraints set to 0.
function constraint:reset()
    self.strategy = "max"
    self._width = 0
    self._height = 0
    self:set_widget(nil)
end

--- Returns a new constraint layout.
-- @param widget A widget to use (optional)
-- @param strategy How to constraint the size. 'max' (default), 'min' or
-- 'exact'. (optional)
-- @param width The maximum width of the widget. 0 for no limit. (optional)
-- @param height The maximum height of the widget. 0 for no limit. (optional)
local function new(widget, strategy, width, height)
    local ret = widget_base.make_widget()

    for k, v in pairs(constraint) do
        if type(v) == "function" then
            ret[k] = v
        end
    end

    ret._emit_updated = function()
        ret:emit_signal("widget::updated")
    end

    ret:set_strategy(strategy or "max")
    ret:set_width(width or 0)
    ret:set_height(height or 0)

    if widget then
        ret:set_widget(widget)
    end

    return ret
end

function constraint.mt:__call(...)
    return new(...)
end

return setmetatable(constraint, constraint.mt)

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