local Widget = require("ui/widget/widget")
local RenderText = require("ui/rendertext")
local Screen = require("ui/screen")
local Geom = require("ui/geometry")

-- TODO: rename string:gsplit definition

--[[
A TextWidget that handles long text wrapping
--]]
local TextBoxWidget = Widget:new{
	text = nil,
	face = nil,
	bgcolor = 0.0, -- [0.0, 1.0]
	fgcolor = 1.0, -- [0.0, 1.0]
	width = 400, -- in pixels
	height = nil,
	first_line = 1,
	virtual_line = 1, -- used by scroll bar
	line_height = 0.3, -- in em
	v_list = nil,
	_bb = nil,
	_length = 0,
}

function TextBoxWidget:init()
	local v_list = nil
	if self.height then
		v_list = self:_getCurrentVerticalList()
	else
		v_list = self:_getVerticalList()
	end
	self:_render(v_list)
end

function TextBoxWidget:_wrapGreedyAlg(h_list)
	local cur_line_width = 0
	local cur_line = {}
	local v_list = {}

	for k,w in ipairs(h_list) do
		cur_line_width = cur_line_width + w.width
		if cur_line_width <= self.width then
			table.insert(cur_line, w)
		else
			-- wrap to next line
			table.insert(v_list, cur_line)
			cur_line = {}
			cur_line_width = w.width
			table.insert(cur_line, w)
		end
	end
	-- handle last line
	table.insert(v_list, cur_line)

	return v_list
end

--[[
Lua doesn't have a string.split() function and most of the time
you don't really need it because string.gmatch() is enough.
However string.gmatch() has one significant disadvantage for me:
You can't split a string while matching both the delimited
strings and the delimiters themselves without tracking positions
and substrings. The string.gsplit() function below takes care of
this problem. 
Author: Peter Odding
License: MIT/X11
Source: http://snippets.luacode.org/snippets/String_splitting_130
--]]
function string:gsplit(pattern, capture)
	pattern = pattern and tostring(pattern) or '%s+'
	if (''):find(pattern) then
		error('pattern matches empty string!', 2)
	end
	return coroutine.wrap(function()
		local index = 1
		repeat
			local first, last = self:find(pattern, index)
			if first and last then
				if index < first then
					coroutine.yield(self:sub(index, first - 1))
				end
				if capture then
					coroutine.yield(self:sub(first, last))
				end
				index = last + 1
			else
				if index <= #self then
					coroutine.yield(self:sub(index))
				end
				break
			end
		until index > #self
	end)
end

function TextBoxWidget:_getVerticalList(alg)
	if self.vertical_list then
		return self.vertical_list
	end
	-- build horizontal list
	local h_list = {}
	for words in self.text:gmatch("[\32-\127\192-\255]+[\128-\191]*") do
		for word in words:gsplit("%s+", true) do
			for w in word:gsplit("%p+", true) do
				local word_box = {}
				word_box.word = w
				word_box.width = RenderText:sizeUtf8Text(0, Screen:getWidth(), self.face, w, true).x
				table.insert(h_list, word_box)
			end
		end
	end

	-- @TODO check alg here 25.04 2012 (houqp)
	-- @TODO replace greedy algorithm with K&P algorithm  25.04 2012 (houqp)
	self.vertical_list = self:_wrapGreedyAlg(h_list)
	return self.vertical_list
end

function TextBoxWidget:_getCurrentVerticalList()
	local line_height = (1 + self.line_height) * self.face.size
	local v_list = self:_getVerticalList()
	local current_v_list = {}
	local height = 0
	for i = self.first_line, #v_list do
		if height < self.height - line_height then
			table.insert(current_v_list, v_list[i])
			height = height + line_height
		else
			break
		end
	end
	return current_v_list
end

function TextBoxWidget:_getPreviousVerticalList()
	local line_height = (1 + self.line_height) * self.face.size
	local v_list = self:_getVerticalList()
	local previous_v_list = {}
	local height = 0
	if self.first_line == 1 then
		return self:_getCurrentVerticalList()
	end
	self.virtual_line = self.first_line
	for i = self.first_line - 1, 1, -1 do
		if height < self.height - line_height then
			table.insert(previous_v_list, 1, v_list[i])
			height = height + line_height
			self.virtual_line = self.virtual_line - 1
		else
			break
		end
	end
	for i = self.first_line, #v_list do
		if height < self.height - line_height then
			table.insert(previous_v_list, v_list[i])
			height = height + line_height
		else
			break
		end
	end
	if self.first_line > #previous_v_list then
		self.first_line = self.first_line - #previous_v_list
	else
		self.first_line = 1
	end
	return previous_v_list
end

function TextBoxWidget:_getNextVerticalList()
	local line_height = (1 + self.line_height) * self.face.size
	local v_list = self:_getVerticalList()
	local current_v_list = self:_getCurrentVerticalList()
	local next_v_list = {}
	local height = 0
	if self.first_line + #current_v_list > #v_list then
		return current_v_list
	end
	self.virtual_line = self.first_line
	for i = self.first_line + #current_v_list, #v_list do
		if height < self.height - line_height then
			table.insert(next_v_list, v_list[i])
			height = height + line_height
			self.virtual_line = self.virtual_line + 1
		else
			break
		end
	end
	self.first_line = self.first_line + #current_v_list
	return next_v_list
end

function TextBoxWidget:_render(v_list)
	local font_height = self.face.size
	local line_height_px = self.line_height * font_height
	local space_w = RenderText:sizeUtf8Text(0, Screen:getWidth(), self.face, " ", true).x
	local h = (font_height + line_height_px) * #v_list
	self._bb = Blitbuffer.new(self.width, h)
	local y = font_height
	local pen_x = 0
	for _,l in ipairs(v_list) do
		pen_x = 0
		for _,w in ipairs(l) do
			--@TODO Don't use kerning for monospaced fonts.    (houqp)
			-- refert to cb25029dddc42693cc7aaefbe47e9bd3b7e1a750 in master tree
			RenderText:renderUtf8Text(self._bb, pen_x, y, self.face, w.word, true,
						   self.bgcolor, self.fgcolor)
			pen_x = pen_x + w.width
		end
		y = y + line_height_px + font_height
	end
--	-- if text is shorter than one line, shrink to text's width
--	if #v_list == 1 then
--		self.width = pen_x
--	end
end

function TextBoxWidget:getVirtualLineNum()
	return self.virtual_line
end

function TextBoxWidget:getAllLineCount()
	local v_list = self:_getVerticalList()
	return #v_list
end

function TextBoxWidget:getVisLineCount()
	local line_height = (1 + self.line_height) * self.face.size
	return math.floor(self.height / line_height)
end

function TextBoxWidget:scrollDown()
	local next_v_list = self:_getNextVerticalList()
	self:free()
	self:_render(next_v_list)
end

function TextBoxWidget:scrollUp()
	local previous_v_list = self:_getPreviousVerticalList()
	self:free()
	self:_render(previous_v_list)
end

function TextBoxWidget:getSize()
	if self.width and self.height then
		return Geom:new{ w = self.width, h = self.height}
	else
		return Geom:new{ w = self.width, h = self._bb:getHeight()}
	end
end

function TextBoxWidget:paintTo(bb, x, y)
	bb:blitFrom(self._bb, x, y, 0, 0, self.width, self._bb:getHeight())
end

function TextBoxWidget:free()
	if self._bb then
		self._bb:free()
		self._bb = nil
	end
end

return TextBoxWidget
