local Device = require("device")
local Screen = Device.screen
local Input = require("device").input
local Event = require("ui/event")
local util = require("ffi/util")
local DEBUG = require("dbg")
local _ = require("gettext")

-- NOTE: Those have been confirmed on Kindle devices. Might be completely different on Kobo (except for AUTO)!
local WAVEFORM_MODE_INIT        = 0x0    -- Screen goes to white (clears)
local WAVEFORM_MODE_DU          = 0x1    -- Grey->white/grey->black
local WAVEFORM_MODE_GC16        = 0x2    -- High fidelity (flashing)
local WAVEFORM_MODE_GC4         = WAVEFORM_MODE_GC16 -- For compatibility
local WAVEFORM_MODE_GC16_FAST   = 0x3    -- Medium fidelity
local WAVEFORM_MODE_A2          = 0x4    -- Faster but even lower fidelity
local WAVEFORM_MODE_GL16        = 0x5    -- High fidelity from white transition
local WAVEFORM_MODE_GL16_FAST   = 0x6    -- Medium fidelity from white transition
-- Kindle FW >= 5.3
local WAVEFORM_MODE_DU4         = 0x7    -- Medium fidelity 4 level of gray direct update
-- Kindle PW2
local WAVEFORM_MODE_REAGL       = 0x8    -- Ghost compensation waveform
local WAVEFORM_MODE_REAGLD      = 0x9    -- Ghost compensation waveform with dithering

local WAVEFORM_MODE_AUTO        = 0x101

-- there is only one instance of this
local UIManager = {
    default_refresh_type = 0, -- 0 for partial refresh, 1 for full refresh
    default_waveform_mode = WAVEFORM_MODE_GC16, -- high fidelity waveform
    fast_waveform_mode = WAVEFORM_MODE_A2,
    full_refresh_waveform_mode = WAVEFORM_MODE_GC16,
    partial_refresh_waveform_mode = WAVEFORM_MODE_GC16,
    -- force to repaint all the widget is stack, will be reset to false
    -- after each ui loop
    repaint_all = false,
    -- force to do full refresh, will be reset to false
    -- after each ui loop
    full_refresh = false,
    -- force to do partial refresh, will be reset to false
    -- after each ui loop
    partial_refresh = false,
    -- trigger a full refresh when counter reaches FULL_REFRESH_COUNT
    FULL_REFRESH_COUNT = G_reader_settings:readSetting("full_refresh_count") or DRCOUNTMAX,
    refresh_count = 0,

    event_handlers = nil,

    _running = true,
    _window_stack = {},
    _execution_stack = {},
    _dirty = {},
    _zeromqs = {},
}

function UIManager:init()
    self.event_handlers = {
        __default__ = function(input_event)
            self:sendEvent(input_event)
        end,
        SaveState = function()
            self:sendEvent(Event:new("FlushSettings"))
        end,
        Power = function(input_event)
            Device:onPowerEvent(input_event)
        end,
    }
    if Device:isKobo() then
        self.event_handlers["Suspend"] = function(input_event)
            self:sendEvent(Event:new("FlushSettings"))
            Device:onPowerEvent(input_event)
        end
        self.event_handlers["Resume"] = function(input_event)
            Device:onPowerEvent(input_event)
            self:sendEvent(Event:new("Resume"))
        end
        self.event_handlers["Light"] = function()
            Device:getPowerDevice():toggleFrontlight()
        end
        self.event_handlers["__default__"] = function(input_event)
            if Device.screen_saver_mode then
                -- Suspension in Kobo can be interrupted by screen updates. We
                -- ignore user touch input here so screen udpate won't be
                -- triggered in suspend mode
                return
            else
                self:sendEvent(input_event)
            end
        end
        if KOBO_LIGHT_ON_START and tonumber(KOBO_LIGHT_ON_START) > -1 then
            Device:getPowerDevice():setIntensity( math.max( math.min(KOBO_LIGHT_ON_START,100) ,0) )
        end
    elseif Device:isKindle() then
        self.event_handlers["IntoSS"] = function()
            self:sendEvent(Event:new("FlushSettings"))
            Device:intoScreenSaver()
        end
        self.event_handlers["OutOfSS"] = function()
            Device:outofScreenSaver()
            self:sendEvent(Event:new("Resume"))
        end
        self.event_handlers["Charging"] = function()
            Device:usbPlugIn()
        end
        self.event_handlers["NotCharging"] = function()
            Device:usbPlugOut()
            self:sendEvent(Event:new("NotCharging"))
        end
        -- Emulate the stock reader refresh behavior...
        --[[
            NOTE: For ref, on a Touch (debugPaint is my new best friend):
                UI: gc16_fast
                Reader: When flash: if to/from img: gc16, else gc16_fast; when non-flash: auto (seems to prefer gl16_fast); Waiting for marker only on flash
            On a PW2:
                Same as Touch, except reader uses reagl on non-flash, non-flash lasts longer (12 pgs); Always waits for marker
        --]]
        -- We don't really have an easy way to know if we're refreshing the UI, or a page, or if said page contains an image, so go with the highest fidelity option
        self.full_refresh_waveform_mode = WAVEFORM_MODE_GC16
        -- We spend much more time in the reader than the UI, and our UI isn't very graphic anyway, so go with the reader behavior
        if Device.model == "KindlePaperWhite2" then
            self.partial_refresh_waveform_mode = WAVEFORM_MODE_REAGL
        else
            self.partial_refresh_waveform_mode = WAVEFORM_MODE_GL16_FAST
            -- NOTE: Or we could go back to what KOReader did before fa55acc in koreader-base, which was also use WAVEFORM_MODE_AUTO ;). I have *no* idea how the driver makes its choice though...
            --self.partial_refresh_waveform_mode = WAVEFORM_MODE_AUTO
        end
    end
end

-- register & show a widget
-- modal widget should be always on the top
function UIManager:show(widget, x, y)
    DEBUG("show widget", widget.id)
    self._running = true
    local window = {x = x or 0, y = y or 0, widget = widget}
    -- put this window on top of the toppest non-modal window
    for i = #self._window_stack, 0, -1 do
        local top_window = self._window_stack[i]
        -- skip modal window
        if not top_window or not top_window.widget.modal then
            table.insert(self._window_stack, i + 1, window)
            break
        end
    end
    -- and schedule it to be painted
    self:setDirty(widget)
    -- tell the widget that it is shown now
    widget:handleEvent(Event:new("Show"))
    -- check if this widget disables double tap gesture
    if widget.disable_double_tap then
        Input.disable_double_tap = true
    end
end

-- unregister a widget
function UIManager:close(widget)
    DEBUG("close widget", widget.id)
    Input.disable_double_tap = DGESDETECT_DISABLE_DOUBLE_TAP
    local dirty = false
    for i = #self._window_stack, 1, -1 do
        if self._window_stack[i].widget == widget then
            table.remove(self._window_stack, i)
            dirty = true
        elseif self._window_stack[i].widget.disable_double_tap then
            Input.disable_double_tap = true
        end
    end
    if dirty then
        -- schedule remaining widgets to be painted
        for i = 1, #self._window_stack do
            self:setDirty(self._window_stack[i].widget)
        end
    end
end

-- schedule an execution task
function UIManager:schedule(time, action)
    table.insert(self._execution_stack, { time = time, action = action })
end

-- schedule task in a certain amount of seconds (fractions allowed) from now
function UIManager:scheduleIn(seconds, action)
    local when = { util.gettime() }
    local s = math.floor(seconds)
    local usecs = (seconds - s) * 1000000
    when[1] = when[1] + s
    when[2] = when[2] + usecs
    if when[2] > 1000000 then
        when[1] = when[1] + 1
        when[2] = when[2] - 1000000
    end
    self:schedule(when, action)
end

-- register a widget to be repainted
function UIManager:setDirty(widget, refresh_type)
    -- "auto": request full refresh
    -- "full": force full refresh
    -- "partial": partial refresh
    if not refresh_type then
        refresh_type = "auto"
    end
    if widget then
        self._dirty[widget] = refresh_type
    end
end

function UIManager:insertZMQ(zeromq)
    table.insert(self._zeromqs, zeromq)
    return zeromq
end

function UIManager:removeZMQ(zeromq)
    for i = #self._zeromqs, 1, -1 do
        if self._zeromqs[i] == zeromq then
            table.remove(self._zeromqs, i)
        end
    end
end

-- set full refresh rate for e-ink screen
-- and make the refresh rate persistant in global reader settings
function UIManager:setRefreshRate(rate)
    DEBUG("set screen full refresh rate", rate)
    self.FULL_REFRESH_COUNT = rate
    G_reader_settings:saveSetting("full_refresh_count", rate)
end

-- get full refresh rate for e-ink screen
function UIManager:getRefreshRate(rate)
    return self.FULL_REFRESH_COUNT
end

-- signal to quit
function UIManager:quit()
    DEBUG("quit uimanager")
    self._running = false
    for i = #self._window_stack, 1, -1 do
        table.remove(self._window_stack, i)
    end
    for i = #self._execution_stack, 1, -1 do
        table.remove(self._execution_stack, i)
    end
    for i = #self._zeromqs, 1, -1 do
        self._zeromqs[i]:stop()
        table.remove(self._zeromqs, i)
    end
end

-- transmit an event to registered widgets
function UIManager:sendEvent(event)
    if #self._window_stack == 0 then return end
    -- top level widget has first access to the event
    if self._window_stack[#self._window_stack].widget:handleEvent(event) then
        return
    end

    -- if the event is not consumed, active widgets can access it
    for _, widget in ipairs(self._window_stack) do
        if widget.widget.is_always_active then
            if widget.widget:handleEvent(event) then return end
        end
        if widget.widget.active_widgets then
            for _, active_widget in ipairs(widget.widget.active_widgets) do
                if active_widget:handleEvent(event) then return end
            end
        end
    end
end

function UIManager:checkTasks()
    local now = { util.gettime() }

    -- check if we have timed events in our queue and search next one
    local wait_until = nil
    local all_tasks_checked
    repeat
        all_tasks_checked = true
        for i = #self._execution_stack, 1, -1 do
            local task = self._execution_stack[i]
            if not task.time
                or task.time[1] < now[1]
                or task.time[1] == now[1] and task.time[2] < now[2] then
                -- task is pending to be executed right now. do it.
                task.action()
                -- and remove from table
                table.remove(self._execution_stack, i)
                -- start loop again, since new tasks might be on the
                -- queue now
                all_tasks_checked = false
            elseif not wait_until
                or wait_until[1] > task.time[1]
                or wait_until[1] == task.time[1] and wait_until[2] > task.time[2] then
                -- task is to be run in the future _and_ is scheduled
                -- earlier than the tasks we looked at already
                -- so adjust to the currently examined task instead.
                wait_until = task.time
            end
        end
    until all_tasks_checked
    return wait_until
end

-- this is the main loop of the UI controller
-- it is intended to manage input events and delegate
-- them to dialogs
function UIManager:run()
    self._running = true
    while self._running do
        local now = { util.gettime() }
        local wait_until = self:checkTasks()

        --DEBUG("---------------------------------------------------")
        --DEBUG("exec stack", self._execution_stack)
        --DEBUG("window stack", self._window_stack)
        --DEBUG("dirty stack", self._dirty)
        --DEBUG("---------------------------------------------------")

        -- stop when we have no window to show
        if #self._window_stack == 0 then
            DEBUG("no dialog left to show")
            self:quit()
            return nil
        end

        -- repaint dirty widgets
        local dirty = false
        local request_full_refresh = false
        local force_full_refresh = false
        local force_partial_refresh = false
        local force_fast_refresh = false
        for _, widget in ipairs(self._window_stack) do
            -- paint if repaint_all is request
            -- paint also if current widget or any widget underneath is dirty
            if self.repaint_all or dirty or self._dirty[widget.widget] then
                widget.widget:paintTo(Screen.bb, widget.x, widget.y)

                if self._dirty[widget.widget] == "auto" then
                    request_full_refresh = true
                end
                if self._dirty[widget.widget] == "full" then
                    force_full_refresh = true
                end
                if self._dirty[widget.widget] == "partial" then
                    force_partial_refresh = true
                end
                if self._dirty[widget.widget] == "fast" then
                    force_fast_refresh = true
                end
                -- and remove from list after painting
                self._dirty[widget.widget] = nil
                -- trigger repaint
                dirty = true
            end
        end

        if self.full_refresh then
            dirty = true
            force_full_refresh = true
        end

        if self.partial_refresh then
            dirty = true
            force_partial_refresh = true
        end

        self.repaint_all = false
        self.full_refresh = false
        self.partial_refresh = false

        local refresh_type = self.default_refresh_type
        local waveform_mode = self.default_waveform_mode
        if dirty then
            if force_partial_refresh or force_fast_refresh then
                refresh_type = 0
            elseif force_full_refresh or self.refresh_count == self.FULL_REFRESH_COUNT - 1 then
                refresh_type = 1
            end
            -- Handle the waveform mode selection...
            if refresh_type == 1 then
                waveform_mode = self.full_refresh_waveform_mode
            else
                waveform_mode = self.partial_refresh_waveform_mode
            end
            if force_fast_refresh then
                waveform_mode = self.fast_waveform_mode
            end
            if self.update_region_func then
                local update_region = self.update_region_func()
                -- in some rare cases update region has 1 pixel offset
                Screen:refresh(refresh_type, waveform_mode,
                               update_region.x-1, update_region.y-1,
                               update_region.w+2, update_region.h+2)
            else
                Screen:refresh(refresh_type, waveform_mode)
            end
            if self.refresh_type == 1 then
                self.refresh_count = 0
            elseif not force_partial_refresh and not force_full_refresh then
                self.refresh_count = (self.refresh_count + 1)%self.FULL_REFRESH_COUNT
            end
            self.update_region_func = nil
        end

        self:checkTasks()

        -- wait for next event
        -- note that we will skip that if in the meantime we have tasks that are ready to run
        local input_event = nil
        if not wait_until then
            if #self._zeromqs > 0 then
                -- pending message queue, wait 100ms for input
                input_event = Input:waitEvent(1000*100)
                if not input_event or input_event.handler == "onInputError" then
                    for _, zeromq in ipairs(self._zeromqs) do
                        input_event = zeromq:waitEvent()
                        if input_event then break end
                    end
                end
            else
                -- no pending task, wait endlessly
                input_event = Input:waitEvent()
            end
        elseif wait_until[1] > now[1]
        or wait_until[1] == now[1] and wait_until[2] > now[2] then
            local wait_for = { s = wait_until[1] - now[1], us = wait_until[2] - now[2] }
            if wait_for.us < 0 then
                wait_for.s = wait_for.s - 1
                wait_for.us = 1000000 + wait_for.us
            end
            -- wait until next task is pending
            input_event = Input:waitEvent(wait_for.us, wait_for.s)
        end

        -- delegate input_event to handler
        if input_event then
            local handler = self.event_handlers[input_event]
            if handler then
                handler(input_event)
            else
                self.event_handlers["__default__"](input_event)
            end
        end
    end
end

function UIManager:getRefreshMenuTable()
    local function custom_1() return G_reader_settings:readSetting("refresh_rate_1") or 12 end
    local function custom_2() return G_reader_settings:readSetting("refresh_rate_2") or 22 end
    local function custom_3() return G_reader_settings:readSetting("refresh_rate_3") or 99 end
    local function custom_input(name)
        return {
            title = _("Input page number for a full refresh"),
            type = "number",
            hint = "(1 - 99)",
            callback = function(input)
                local rate = tonumber(input)
                G_reader_settings:saveSetting(name, rate)
                UIManager:setRefreshRate(rate)
            end,
        }
    end
    return {
        text = _("E-ink full refresh rate"),
        sub_item_table = {
            {
                text = _("Every page"),
                checked_func = function() return UIManager:getRefreshRate() == 1 end,
                callback = function() UIManager:setRefreshRate(1) end,
            },
            {
                text = _("Every 6 pages"),
                checked_func = function() return UIManager:getRefreshRate() == 6 end,
                callback = function() UIManager:setRefreshRate(6) end,
            },
            {
                text_func = function() return _("Custom ") .. "1: " .. custom_1() .. _(" pages") end,
                checked_func = function() return UIManager:getRefreshRate() == custom_1() end,
                callback = function() UIManager:setRefreshRate(custom_1()) end,
                hold_input = custom_input("refresh_rate_1")
            },
            {
                text_func = function() return _("Custom ") .. "2: " .. custom_2() .. _(" pages") end,
                checked_func = function() return UIManager:getRefreshRate() == custom_2() end,
                callback = function() UIManager:setRefreshRate(custom_2()) end,
                hold_input = custom_input("refresh_rate_2")
            },
            {
                text_func = function() return _("Custom ") .. "3: " .. custom_3() .. _(" pages") end,
                checked_func = function() return UIManager:getRefreshRate() == custom_3() end,
                callback = function() UIManager:setRefreshRate(custom_3()) end,
                hold_input = custom_input("refresh_rate_3")
            },
        }
    }
end

UIManager:init()
return UIManager