require "math"

ReaderPaging = InputContainer:new{
	current_page = 0,
	number_of_pages = 0,
	visible_area = nil,
	page_area = nil,
	show_overlap_enable = true,
	overlap = scaleByDPI(20),
}

function ReaderPaging:init()
	if Device:hasKeyboard() then
		self.key_events = {
			GotoNextPage = {
				{Input.group.PgFwd}, doc = "go to next page",
				event = "GotoPageRel", args = 1 },
			GotoPrevPage = {
				{Input.group.PgBack}, doc = "go to previous page",
				event = "GotoPageRel", args = -1 },

			GotoFirst = {
				{"1"}, doc = "go to start", event = "GotoPercent", args = 0},
			Goto11 = {
				{"2"}, doc = "go to 11%", event = "GotoPercent", args = 11},
			Goto22 = {
				{"3"}, doc = "go to 22%", event = "GotoPercent", args = 22},
			Goto33 = {
				{"4"}, doc = "go to 33%", event = "GotoPercent", args = 33},
			Goto44 = {
				{"5"}, doc = "go to 44%", event = "GotoPercent", args = 44},
			Goto55 = {
				{"6"}, doc = "go to 55%", event = "GotoPercent", args = 55},
			Goto66 = {
				{"7"}, doc = "go to 66%", event = "GotoPercent", args = 66},
			Goto77 = {
				{"8"}, doc = "go to 77%", event = "GotoPercent", args = 77},
			Goto88 = {
				{"9"}, doc = "go to 88%", event = "GotoPercent", args = 88},
			GotoLast = {
				{"0"}, doc = "go to end", event = "GotoPercent", args = 100},
		}
	end
	self.number_of_pages = self.ui.document.info.number_of_pages
end

-- This method will  be called in onSetDimensions handler
function ReaderPaging:initGesListener()
	self.ges_events = {
		TapForward = {
			GestureRange:new{
				ges = "tap",
				range = Geom:new{
					x = Screen:getWidth()/4,
					y = Screen:getHeight()/4,
					w = 3*Screen:getWidth()/4,
					h = 5*Screen:getHeight()/8,
				}
			}
		},
		TapBackward = {
			GestureRange:new{
				ges = "tap",
				range = Geom:new{
					x = 0,
					y = Screen:getHeight()/4,
					w = Screen:getWidth()/4,
					h = 5*Screen:getHeight()/8,
				}
			}
		},
		ToggleFlipping = {
			GestureRange:new{
				ges = "tap",
				range = Geom:new{
					x = 0, y = 0,
					w = Screen:getWidth()/8,
					h = Screen:getHeight()/8
				}
			}
		},
		Swipe = {
			GestureRange:new{
				ges = "swipe",
				range = Geom:new{
					x = 0, y = 0,
					w = Screen:getWidth(),
					h = Screen:getHeight(),
				}
			}
		},
		Pan = {
			GestureRange:new{
				ges = "pan",
				range = Geom:new{
					x = 0, y = 0,
					w = Screen:getWidth(),
					h = Screen:getHeight(),
				},
				rate = 4.0,
			}
		},
		PanRelease = {
			GestureRange:new{
				ges = "pan_release",
				range = Geom:new{
					x = 0, y = 0,
					w = Screen:getWidth(),
					h = Screen:getHeight(),
				},
			}
		},
	}
end

function ReaderPaging:onReadSettings(config)
	self:gotoPage(config:readSetting("last_page") or 1)
	local soe = config:readSetting("show_overlap_enable")
	if not soe then
		self.show_overlap_enable = soe
	end
end

function ReaderPaging:onCloseDocument()
	self.ui.doc_settings:saveSetting("last_page", self.current_page)
	self.ui.doc_settings:saveSetting("percent_finished", self.current_page/self.number_of_pages)
end

function ReaderPaging:onTapForward()
	self:onPagingRel(1)
	return true
end

function ReaderPaging:onTapBackward()
	self:onPagingRel(-1)
	return true
end

function ReaderPaging:onToggleFlipping()
	self.view.flipping_visible = not self.view.flipping_visible
	self.flipping_mode = self.view.flipping_visible
	self.flipping_page = self.current_page
	if self.flipping_mode then
		self:updateOriginalPage(self.current_page)
	else
		self:updateOriginalPage(nil)
	end
	self.ui:handleEvent(Event:new("SetHinting", not self.flipping_mode))
	UIManager:setDirty(self.view.dialog, "partial")
end

function ReaderPaging:updateOriginalPage(page)
	self.original_page = page
end

function ReaderPaging:updateFlippingPage(page)
	self.flipping_page = page
end

function ReaderPaging:flipping(flipping_page, flipping_ges)
	local read = flipping_page - 1
	local unread = self.number_of_pages - flipping_page
	local whole = self.number_of_pages
	local rel_proportion = flipping_ges.distance / Screen:getWidth()
	local abs_proportion = flipping_ges.distance / Screen:getHeight()
	if flipping_ges.direction == "right" then
		self:gotoPage(flipping_page - math.floor(read*rel_proportion))
	elseif flipping_ges.direction == "left" then
		self:gotoPage(flipping_page + math.floor(unread*rel_proportion))
	elseif flipping_ges.direction == "down" then
		self:gotoPage(flipping_page - math.floor(whole*abs_proportion))
	elseif flipping_ges.direction == "up" then
		self:gotoPage(flipping_page + math.floor(whole*abs_proportion))
	end
	UIManager:setDirty(self.view.dialog, "partial")
end

function ReaderPaging:onSwipe(arg, ges)
	if self.flipping_mode then
		self:flipping(self.flipping_page, ges)
		self:updateFlippingPage(self.current_page)
	elseif self.original_page then
		self:gotoPage(self.original_page)
		self:updateOriginalPage(nil)
	elseif ges.direction == "left" or ges.direction == "up" then
		self:onPagingRel(1)
	elseif ges.direction == "right" or ges.direction == "down" then
		self:onPagingRel(-1)
	end
	return true
end

function ReaderPaging:onPan(arg, ges)
	if self.flipping_mode then
		self:flipping(self.flipping_page, ges)
	end
	return true
end

function ReaderPaging:onPanRelease(arg, ges)
	if self.flipping_mode then
		self:updateFlippingPage(self.current_page)
	end
end

function ReaderPaging:onZoomModeUpdate(new_mode)
	-- we need to remember zoom mode to handle page turn event
	self.zoom_mode = new_mode
end

function ReaderPaging:onPageUpdate(new_page_no, orig)
	self.current_page = new_page_no
	if orig ~= "scrolling" then
		self.ui:handleEvent(Event:new("InitScrollPageStates", orig))
	end
end

function ReaderPaging:onViewRecalculate(visible_area, page_area)
	-- we need to remember areas to handle page turn event
	self.visible_area = visible_area:copy()
	self.page_area = page_area
end

function ReaderPaging:onGotoPercent(percent)
	DEBUG("goto document offset in percent:", percent)
	local dest = math.floor(self.number_of_pages * percent / 100)
	if dest < 1 then dest = 1 end
	if dest > self.number_of_pages then
		dest = self.number_of_pages
	end
	self:gotoPage(dest)
	return true
end

function ReaderPaging:onPagingRel(diff)
	if self.view.page_scroll then
		self:onScrollPageRel(diff)
	else
		self:onGotoPageRel(diff)
	end
	return true
end

function ReaderPaging:onInitScrollPageStates(orig)
	DEBUG("init scroll page states")
	if self.view.page_scroll then
		self.orig_page = self.current_page
		self.view.page_states = {}
		local blank_area = Geom:new{}
		blank_area:setSizeTo(self.view.dimen)
		while blank_area.h > 0 do
			local state = self:getNextPageState(blank_area, Geom:new{})
			--DEBUG("init new state", state)
			table.insert(self.view.page_states, state)
			if blank_area.h > 0 then
				blank_area.h = blank_area.h - self.view.page_gap.height
			end
			if blank_area.h > 0 then
				self:gotoPage(self.current_page + 1, "scrolling")
			end
		end
		self:gotoPage(self.orig_page, "scrolling")
	end
	return true
end

function ReaderPaging:onUpdateScrollPageRotation(rotation)
	for _, state in ipairs(self.view.page_states) do
		state.rotation = rotation
	end
	return true
end

function ReaderPaging:onUpdateScrollPageGamma(gamma)
	for _, state in ipairs(self.view.page_states) do
		state.gamma = gamma
	end
	return true
end

function ReaderPaging:getNextPageState(blank_area, offset)
	local page_area = self.view:getPageArea(
		self.view.state.page,
		self.view.state.zoom,
		self.view.state.rotation)
	local visible_area = Geom:new{x = 0, y = 0}
	visible_area.w, visible_area.h = blank_area.w, blank_area.h
	visible_area.x, visible_area.y = page_area.x, page_area.y
	visible_area = visible_area:shrinkInside(page_area, offset.x, offset.y)
	-- shrink blank area by the height of visible area
	blank_area.h = blank_area.h - visible_area.h
	return {
		page = self.view.state.page,
		zoom = self.view.state.zoom,
		rotation = self.view.state.rotation,
		gamma = self.view.state.gamma,
		offset = Geom:new{ x = self.view.state.offset.x, y = 0},
		visible_area = visible_area,
		page_area = page_area,
	}
end

function ReaderPaging:getPrevPageState(blank_area, offset)
	local page_area = self.view:getPageArea(
		self.view.state.page,
		self.view.state.zoom,
		self.view.state.rotation)
	local visible_area = Geom:new{x = 0, y = 0}
	visible_area.w, visible_area.h = blank_area.w, blank_area.h
	visible_area.x = page_area.x
	visible_area.y = page_area.y + page_area.h - visible_area.h
	visible_area = visible_area:shrinkInside(page_area, offset.x, offset.y)
	-- shrink blank area by the height of visible area
	blank_area.h = blank_area.h - visible_area.h
	return {
		page = self.view.state.page,
		zoom = self.view.state.zoom,
		rotation = self.view.state.rotation,
		gamma = self.view.state.gamma,
		offset = Geom:new{ x = self.view.state.offset.x, y = 0},
		visible_area = visible_area,
		page_area = page_area,
	}
end

function ReaderPaging:updateLastPageState(state, blank_area, offset)
	local visible_area = Geom:new{x = 0, y = 0}
	visible_area.w, visible_area.h = blank_area.w, blank_area.h
	visible_area.x, visible_area.y = state.visible_area.x, state.visible_area.y
	if state.page == self.number_of_pages then
		visible_area:offsetWithin(state.page_area, offset.x, offset.y)
	else
		visible_area = visible_area:shrinkInside(state.page_area, offset.x, offset.y)
	end
	-- shrink blank area by the height of visible area
	blank_area.h = blank_area.h - visible_area.h
	state.visible_area = visible_area
	return state
end

function ReaderPaging:updateFirstPageState(state, blank_area, offset)
	local visible_area = Geom:new{x = 0, y = 0}
	visible_area.w, visible_area.h = blank_area.w, blank_area.h
	visible_area.x = state.page_area.x
	visible_area.y = state.visible_area.y + state.visible_area.h - visible_area.h
	if state.page == 1 then
		visible_area:offsetWithin(state.page_area, offset.x, offset.y)
	else
		visible_area = visible_area:shrinkInside(state.page_area, offset.x, offset.y)
	end
	-- shrink blank area by the height of visible area
	blank_area.h = blank_area.h - visible_area.h
	state.visible_area = visible_area
	return state
end

function ReaderPaging:onScrollPageRel(diff)
	DEBUG("scroll relative page:", diff)
	local blank_area = Geom:new{}
	blank_area:setSizeTo(self.view.dimen)
	if diff > 0 then
		local last_page_state = table.remove(self.view.page_states)
		local offset = Geom:new{
			x = 0,
			y = last_page_state.visible_area.h - self.overlap
		}
		-- Scroll down offset should always be greater than 0
		-- otherwise if offset is less than 0 the height of blank area will be
		-- larger than 0 even if page area is much larger than visible area,
		-- which will trigger the drawing of next page leaving part of current
		-- page undrawn. This should also be true for scroll up offset.
		if offset.y < 0 then offset.y = 0 end
		local state = self:updateLastPageState(last_page_state, blank_area, offset)
		--DEBUG("updated state", state)
		self.view.page_states = {}
		if state.visible_area.h > 0 then
			table.insert(self.view.page_states, state)
		end
		--DEBUG("blank area", blank_area)
		local current_page = state.page
		while blank_area.h > 0 do
			blank_area.h = blank_area.h - self.view.page_gap.height
			if blank_area.h > 0 then
				if self.current_page == self.number_of_pages then break end
				self:gotoPage(current_page + 1, "scrolling")
				current_page = current_page + 1
				local state = self:getNextPageState(blank_area, Geom:new{})
				--DEBUG("new state", state)
				table.insert(self.view.page_states, state)
			end
		end
	end
	if diff < 0 then
		local first_page_state = table.remove(self.view.page_states, 1)
		local offset = Geom:new{
			x = 0,
			y = -first_page_state.visible_area.h + self.overlap
		}
		-- scroll up offset should always be less than 0
		if offset.y > 0 then offset.y = 0 end
		local state = self:updateFirstPageState(first_page_state, blank_area, offset)
		--DEBUG("updated state", state)
		self.view.page_states = {}
		if state.visible_area.h > 0 then
			table.insert(self.view.page_states, state)
		end
		--DEBUG("blank area", blank_area)
		local current_page = state.page
		while blank_area.h > 0 do
			blank_area.h = blank_area.h - self.view.page_gap.height
			if blank_area.h > 0 then
				if self.current_page == 1 then break end
				self:gotoPage(current_page - 1, "scrolling")
				current_page = current_page - 1
				local state = self:getPrevPageState(blank_area, Geom:new{})
				--DEBUG("new state", state)
				table.insert(self.view.page_states, 1, state)
			end
		end
	end
	-- update current pageno to the very last part in current view
	self:gotoPage(self.view.page_states[#self.view.page_states].page, "scrolling")
	UIManager:setDirty(self.view.dialog)
end

function ReaderPaging:onGotoPageRel(diff)
	DEBUG("goto relative page:", diff)
	local new_va = self.visible_area:copy()
	local x_pan_off, y_pan_off = 0, 0

	if self.zoom_mode:find("width") then
		y_pan_off = self.visible_area.h * diff
	elseif self.zoom_mode:find("height") then
		x_pan_off = self.visible_area.w * diff
	else
		-- must be fit content or page zoom mode
		if self.visible_area.w == self.page_area.w then
			y_pan_off = self.visible_area.h * diff
		else
			x_pan_off = self.visible_area.w * diff
		end
	end
	-- adjust offset to help with page turn decision
	-- we dont take overlap into account here yet, otherwise new_va will
	-- always intersect with page_area
	x_pan_off = math.roundAwayFromZero(x_pan_off)
	y_pan_off = math.roundAwayFromZero(y_pan_off)
	new_va.x = math.roundAwayFromZero(self.visible_area.x+x_pan_off)
	new_va.y = math.roundAwayFromZero(self.visible_area.y+y_pan_off)

	if new_va:notIntersectWith(self.page_area) then
		-- view area out of page area, do a page turn
		self:gotoPage(self.current_page + diff)
		-- if we are going back to previous page, reset
		-- view area to bottom of previous page
		if x_pan_off < 0 then
			self.view:PanningUpdate(self.page_area.w, 0)
		elseif y_pan_off < 0 then
			self.view:PanningUpdate(0, self.page_area.h)
		end
		-- reset dim_area
		--self.view.dim_area.h = 0
		--self.view.dim_area.w = 0
		--
	else
		-- not end of page yet, goto next view
		-- adjust panning step according to overlap
		if self.show_overlap_enable then
			if x_pan_off > self.overlap then
				-- moving to next view, move view
				x_pan_off = x_pan_off - self.overlap
			elseif x_pan_off < -self.overlap then
				x_pan_off = x_pan_off + self.overlap
			end
			if y_pan_off > self.overlap then
				y_pan_off = y_pan_off - self.overlap
			elseif y_pan_off < -self.overlap then
				y_pan_off = y_pan_off + self.overlap
			end
			-- we have to calculate again to count into overlap
			new_va.x = math.roundAwayFromZero(self.visible_area.x+x_pan_off)
			new_va.y = math.roundAwayFromZero(self.visible_area.y+y_pan_off)
		end
		-- fit new view area into page area
		new_va:offsetWithin(self.page_area, 0, 0)
		-- calculate panning offsets
		local panned_x = new_va.x - self.visible_area.x
		local panned_y = new_va.y - self.visible_area.y
		-- adjust for crazy float point overflow...
		if math.abs(panned_x) < 1 then
			panned_x = 0
		end
		if math.abs(panned_y) < 1 then
			panned_y = 0
		end
		-- singal panning update
		self.view:PanningUpdate(panned_x, panned_y)
		-- update dime area in ReaderView
		if self.show_overlap_enable then
			self.view.dim_area.h = new_va.h - math.abs(panned_y)
			self.view.dim_area.w = new_va.w - math.abs(panned_x)
			if panned_y < 0 then
				self.view.dim_area.y = new_va.y - panned_y
			else
				self.view.dim_area.y = 0
			end
			if panned_x < 0 then
				self.view.dim_area.x = new_va.x - panned_x
			else
				self.view.dim_area.x = 0
			end
		end
		-- update self.visible_area
		self.visible_area = new_va
	end

	return true
end

function ReaderPaging:onRedrawCurrentPage()
	self.ui:handleEvent(Event:new("PageUpdate", self.current_page))
	return true
end

function ReaderPaging:onSetDimensions()
	-- update listening according to new screen dimen
	if Device:isTouchDevice() then
		self:initGesListener()
	end
end

-- wrapper for bounds checking
function ReaderPaging:gotoPage(number, orig)
	if number == self.current_page then
		return true
	end
	if number > self.number_of_pages
	or number < 1 then
		DEBUG("wrong page number: "..number.."!")
		return false
	end
	DEBUG("going to page number", number)

	-- this is an event to allow other controllers to be aware of this change
	self.ui:handleEvent(Event:new("PageUpdate", number, orig))
	return true
end