local BASE = (...):gsub('ui$', '')

local Widget = require(BASE..'widget')
local Layout = require(BASE..'layout')

local gear = require 'lib.gear'

local Timer = gear.Timer
local isinstance = gear.meta.isinstance
local pointinrect = gear.rect.pointinside

local Ui = {}
Ui.__index = Ui


-- Scan UI for the LAST widgets with 'cancelfocus' or 'firstfocus' flags
local function resolveautofocus(widget)
    local firstfocus, cancelfocus

    if isinstance(widget, Layout) then
        for _,w in ipairs(widget) do
            local firstf, cancelf

            if not w.nofocus then
                if isinstance(w, Layout) then
                    firstf, cancelf = resolveautofocus(w)
                else
                    if w.firstfocus then
                        firstf = w
                    end
                    if w.cancelfocus then
                        cancelf = w
                    end
                end
            end

            firstfocus = firstf or firstfocus
            cancelfocus = cancelf or cancelfocus
        end

    elseif not widget.nofocus then
        if widget.firstfocus then
            firstfocus = widget
        end
        if widget.cancelfocus then
            cancelfocus = widget
        end
    end

    return firstfocus, cancelfocus
end

local function propagateaction(ui, action)
    local focused = ui.focused
    if focused.grabkeyboard then
        -- A widget stealing input
        -- explicitly consumes any action.
        return true
    end
    while focused ~= nil do
        if focused:onActionInput(action) then
            return true  -- action consumed
        end

        focused = focused.parent
    end

    return false
end

function Ui.new(args)
    local self = setmetatable(args, Ui)
    assert(#self == 1, "Ui.new() must have exactly one root widget.")

    self.device = self.device or require(BASE..'device.love').new()
    self.x = self.x or 0
    self.y = self.y or 0
    self.pointerActive = true
    self.timer = Timer.new()

    local root = self[1]
    if not isinstance(root, Widget) then
        error("Ui.new() bad root Widget type: "..type(root)..".")
    end

    root.x,root.y = self.x,self.y
    root.ui = self
    if isinstance(root, Layout) then
        root:layoutWidgets()
    else
        assert(type(root.w) == 'number', "Ui.new() root Widget must have a numeric width.")
        assert(type(root.h) == 'number', "Ui.new() root Widget must have a numeric height.")
        assert(not root.nofocus, "Ui.new() single root Widget can't be nofocus.")
    end

    self.w,self.h = root.w,root.h

    local firstfocus, cancelfocus = resolveautofocus(root)
    if firstfocus == nil then
        firstfocus = isinstance(root, Layout) and
                     root:firstFocusableWidget() or
                     root
    end

    self.cancelfocus = cancelfocus
    firstfocus:grabFocus()

    return self
end

-- Event propagators for widgets listening to keyboard input
function Ui:keypressed(key, scancode, isrepeat)
    local focused = self.focused

    if focused ~= nil and focused.grabkeyboard then
        focused:keypressed(key, scancode, isrepeat)
    end
end
function Ui:keyreleased(key, scancode)
    local focused = self.focused

    if focused ~= nil and focused.grabkeyboard then
        focused:keyreleased(key, scancode)
    end
end
function Ui:textinput(text)
    local focused = self.focused

    if focused ~= nil and focused.grabkeyboard then
        focused:textinput(text)
    end
end
function Ui:textedited(text, start, length)
    local focused = self.focused

    if focused ~= nil and focused.grabkeyboard then
        focused:textedited(text, start, length)
    end
end

function Ui:update(dt)
    local root = self[1]
    local x,y,w,h = root.x,root.y,root.w,root.h
    local snap = self.device:snapshot()

    self.timer:update(dt)

    -- Propagate pointer events in focus order
    if self.pointerActive then
        if snap.pointer and pointinrect(snap.px,snap.py, x,y,w,h) then
            root:onPointerInput(snap.px,snap.py, snap.clicked, snap.pointing)
        end
    end

    -- Propagate actions from focused widget up
    if snap.action and not propagateaction(self, snap) then
        -- Take global actions if nobody consumed the event
        if snap.cancel and self.cancelfocus then
            -- Focus on the last widget with 'cancelfocus'
            self.cancelfocus:grabFocus()
        end
    end

    -- Perform regular lifetime updates
    root:update(dt)
end

function Ui:draw()
    local root = self[1]

    love.graphics.push('all')
        root:draw()
    love.graphics.pop()
end

return Ui