-- this module implements [[Template:Overlay]]
local p = {}

local mArguments = require('Module:Arguments')

-- used to cache the calculated font color to avoid repeat calculations
local previous_backgroundcolor = ''
local fontcolor = ''

local function buildicon(n, form, lk, c, t)
	local res
	if form == 'text' then
		return tostring(
				mw.html.create('span')
					:css('font-weight', 'bold')
					:css('color', c)
					:wikitext(n)
				)
	elseif form == 'color' or form == 'colour' then
		return tostring(
				mw.html.create('span')
					:css('background-color', c)
					:wikitext('  ')
				)
	else
		-- check if the color is difference from the previous color
		if c ~= previous_backgroundcolor then
			-- color changed, so look up the best font color
			local greatercontrast = require('Module:Color contrast')._greatercontrast
			fontcolor = greatercontrast{c, 'white', 'black', bias = 1.3}
			-- update the previous value for the next check
			previous_backgroundcolor = c
		end
		-- build the inner span for the icon
		local span = mw.html.create('span')
			:css('color', fontcolor)
			:css('font-size', '88%')
			:css('font-weight', 'bold')
			:attr('title', t)
			:wikitext(n)
		-- build the outer div
		local div = mw.html.create('div')
			:css('display', 'inline-block')
			:css('width', 'auto')
			:css('height', 'auto')
			:css('text-align', 'center')
			:css('padding', ((tonumber(n) or 0) < 10) and '0px 4px' or '0px 2px')
			:css('vertical-align', 'middle')
			:css('border-radius', '3px')
			:css('background-color', c)

		-- link the inner span if requested and insert in the div
		if lk ~= '' then
			div:wikitext('[[:' .. lk .. '|' .. tostring(span) .. ']]')
		else
			div:wikitext(tostring(span))
		end
		-- convert to a string
		return tostring(div)
	end
end

local function buildlegend(data, cols, border, caption)
	-- create the outer table to hold the columns
	local root = mw.html.create('table')
		:css('width', '100%')
		:css('border', (border ~= 'no') and '1px #ccc solid' or '')
	-- create the outer row which will contain the columns
	local outerrow = root:tag('tr')
	local percol = math.ceil((#data) / cols)
	local k = 0
	for j=1,cols do
		-- create the outer cell to hold this column
		local colcell = outerrow:tag('td')
			:css('width', (math.floor(10/cols)/10) .. '%')
			:css('vertical-align', 'top')
		-- create the inner table to hold the entries in the column
		local coltable = colcell:tag('table')
			:css('width', '100%')
			:css('font-size', '85%')
			:css('line-height', '95%')
		-- add the entries to the column
		for l = 1,percol do
			k = k + 1
			if k <= #data then
				local rdata = data[k]
				local tr = coltable:tag('tr'):css('vertical-align','top')
				tr:tag('td')
					:css('width', '12px')
					:css('text-align', 'right')
					:css('padding-bottom', '2px')
					:wikitext(rdata[1] or '')
				tr:tag('td')
					:css('padding-bottom', '2px')
					:wikitext(rdata[2] or '')
			end
		end
	end
	return caption .. tostring(root)
end

local function buildlegenditem(im, lk, t)
	local res = {im, ''}
	if t ~= '' then
		if lk ~= '' then
			res[2] = '[[:' .. lk .. '|' .. t .. ']]'
		else
			res[2] = t
		end
	else
		res[2] = '[[:' .. lk .. '|' .. lk .. ']]'
	end
	return res 
end

function p.icon(frame)
	local args = mArguments.getArgs(frame)
	return tostring(
		mw.html.create('div')
			:css('display', 'inline-block')
			:css('line-height', '95%')
			:wikitext(buildicon(args['1'] or '', 
								args['form'] or 'icon',
								args['link'] or '', 
								args['2'] or 'red',
								args['tip'] or ''))
	)
end

function p.main(frame)
	local args = mArguments.getArgs(frame)
	
	local image = args['image'] or ''
	local width = tonumber(args['width'] or 500) or 500
	local height = tonumber(args['height'] or 500) or 500
	local columns = tonumber(args['columns'] or 3) or 3
	local grid = ((args['grid'] or ''):lower() == 'yes') and 'yes' or 'no'
	local legendbox = ((args['legendbox'] or ''):lower() == 'no') and 'no' or 'yes'
	local overlay = (image == '') and 'no' or ( ((args['overlay'] or ''):lower() == 'no') and 'no' or 'yes' )
	local float = args['float'] or 'center'
	local border = ((args['border'] or ''):lower() == 'no') and 'no' or 'yes'
	local padding = args['padding'] or ''

	-- create the root table
	local root = mw.html.create('table')
	if float == 'center' or float == 'centre' then
		root:css('margin-left', 'auto')
			:css('margin-right', 'auto')
	elseif float == 'right' then
		root:css('float', 'right')
			:css('clear', 'right')
			:css('margin-left', '1em')
	elseif float == 'left' then
		root:css('float', 'left')
			:css('clear', 'left')
			:css('margin-right', '1em')
	else
		root:css('float', float)
	end
	if border == 'yes' then
		root:css('border', '1px #ccc solid')
	end

	-- create a list of all the overlay numbers
	local itemnums = {}
	for k, v in pairs( args ) do
		local i = tonumber(tostring(k):match( '^%s*overlay([%d]+)%s*$' ) or '-1')
		if i > -1 then
			table.insert(itemnums, i)
		else
			i = tonumber(tostring(k):match( '^%s*overlay([%d]+)tip%s*$' ) or '-1')
			if i > -1 then
				table.insert(itemnums, i)
			end
		end
	end
	-- sort to process in order
	table.sort( itemnums )
	
	-- remove duplicates
	for k = 2,#itemnums do
		if itemnums[k] == itemnums[k-1] then
			table.remove(itemnums, k)
		end
	end

	-- build the overlay markers and text
	itemdata = {}
	local colori = args['color'] or args['colour'] or 'red'
	local formi = ''	
	for k = 1,#itemnums do
		local i = itemnums[k]
		formi = args['overlay' .. i .. 'form'] or formi
		colori = args['overlay' .. i .. 'color'] or args['overlay' .. i .. 'colour'] or colori
		local linki = args['overlay' .. i .. 'link'] or ''
		local tipi = args['overlay' .. i .. 'tip'] or args['overlay' .. i] or ''
		local overlayi = args['overlay' .. i] or args['overlay' .. i .. 'tip'] or ''
		if (overlayi ~= '' or tipi ~= '') then
			local imagei = buildicon(i, formi, linki, colori, tipi)
			itemdata[k] = buildlegenditem(imagei, args['overlay' .. i .. 'link'] or '', overlayi)
		end
	end

	-- create the overlay image
	if image ~= '' then
		local cell = root:tag('tr'):tag('td')
		cell:attr('align', 'center')
		if( padding ~= '' ) then
			cell:css('padding', padding)
		end
		if( columns > 1 and legendbox == 'yes' ) then
			cell:attr('colspan', columns)
		end
		local imagediv = cell:tag('div')
		imagediv:css('position','relative')
			:css('left', '0px')
			:css('top', '0px')
			:css('width', ((grid == 'yes') and 940 or width) .. 'px')
			:css('height', ((grid == 'yes') and 940 or height) .. 'px')
		if grid == 'yes' then
			imagediv:tag('span')
				:css('position', 'absolute')
				:css('left', '0px')
				:css('top', '0px')
				:css('z-index', '2')
				:wikitext('[[File:Grid 99, 100 int red 50 int yellow (940).svg|940px]]')
		end
		imagediv:tag('span')
			:css('position', 'absolute')
			:css('left', '0px')
			:css('top', '0px')
			:css('z-index', '0')
			:css('width', width .. 'px')
			:css('height', height .. 'px')
			:wikitext('[[File:' .. image .. '|' .. width .. 'x' .. height .. 'px]]')
		if overlay == 'yes' then
			for k = 1,#itemnums do
				local i = itemnums[k]
				local imagei = (itemdata[k])[1]
				for j =0,3 do
					local overlayileftj = args['overlay' .. i .. 'left' .. ((j == 0) and '' or j)] or ''
					local overlayitopj = args['overlay' .. i .. 'top' .. ((j == 0) and '' or j)] or ''
					if overlayileftj ~= '' then
						imagediv:tag('div')
							:css('position', 'absolute')
							:css('left', overlayileftj .. 'px')
							:css('top', overlayitopj .. 'px')
							:css('line-height', '95%')
							:css('z-index', '1')
							:wikitext(imagei)
					end
				end
			end
		end
	end

	-- Split the legend items into sub-legends
	legend = {{}, {}, {}, {}, {}}
	local jmax = itemnums[#itemnums]
	for i=1,5 do
		if args['legend' .. i .. 'start'] then
			-- default is all items
			j1 = 0
			j2 = jmax
			-- set start item number to (legendistart) or (legend(i-1)end + 1)
			if args['legend' .. i .. 'start'] then
				j1 = tonumber(args['legend' .. i .. 'start']) or j1
			elseif args['legend' .. (i-1) .. 'end'] then
				j1 = (tonumber(args['legend' .. (i-1) .. 'end']) or j1) + 1
			end
			-- set end item number to (legendiend) or (legend(i+1)start - 1)
			if args['legend' .. i .. 'end'] then
				j2 = tonumber(args['legend' .. i .. 'end']) or j2
			elseif args['legend' .. (i+1) .. 'start'] then
				j2 = (tonumber(args['legend' .. (i+1) .. 'start']) or j2) - 1
			end
			-- get the items within the range, marking them as they are used
			for k=1,#itemnums do
				j = itemnums[k]
				if (j >= 0 and j >= j1 and j <= j2) then
					table.insert(legend[i], itemdata[k])
					itemnums[k] = -1
				end
			end
		end
	end

	-- Add any left over items to the first legend
	for k = 1,#itemnums do
		if itemnums[k] >= 0 then
			table.insert(legend[1], itemdata[k])
		end
	end

	-- Build the legend
	if columns > 0 then
		for i = 1,5 do
			local locallegend = legend[i]
			if (locallegend and #locallegend > 0) then
				local cell = root:tag('tr'):tag('td')
				cell:wikitext(buildlegend(locallegend, columns, border, args['legend' .. i .. 'title'] or ''))
			end
		end
	end

	return tostring(root)
end

return p