Module:Box-header

 local getArgs = require('Module:Arguments').getArgs

 local p = {}
 ---------- Config data ----------
 local namedColours = mw.loadData( 'Module:Box-header/colours' )
 local modes = {
	lightest = { sat=0.10, val=1.00 },
	light = { sat=0.15, val=0.95 },
	normal = { sat=0.40, val=0.85 },
	dark = { sat=0.90, val=0.70 },
	darkest = { sat=1.00, val=0.45 },
	content = { sat=0.04, val=1.00 },
	grey = { sat=0.00 }
 }
 local min_contrast_ratio_normal_text = 7 -- i.e 7:1
 local min_contrast_ratio_large_text = 4.5 -- i.e. 4.5:1

 -- Template parameter aliases
 -- Specify each as either a single value, or a table of values
 -- Aliases are checked left-to-right, i.e. `['one'] = { 'two', 'three' }` is equivalent to using `{{{one| {{{two| {{{three|}}} }}} }}}` in a template
 local parameterAliases = {
	['1'] = 1,
	['2'] = 2,
	['colour'] = 'color'
 }

 ---------- Dependecies ----------
 local colourContrastModule = require('Module:Color contrast')
 local hex = require( 'luabit.hex' )

 ---------- Utility functions ----------
 local function getParam(args, parameter)
	if args[parameter] then
		return args[parameter]
	end
	local aliases = parameterAliases[parameter]
	if not aliases then
		return nil
	end
	if type(aliases) ~= 'table' then
		return args[aliases]
	end
	for _, alias in ipairs(aliases) do
		if args[alias] then
			return args[alias]
		end
	end
	return nil
 end

 local function setCleanArgs(argsTable)
	local cleanArgs = {}
	for key, val in pairs(argsTable) do
		if type(val) == 'string' then
			val = val:match('^%s*(.-)%s*$')
			if val ~= '' then
				cleanArgs[key] = val
			end
		else
			cleanArgs[key] = val
		end
	end
	return cleanArgs
 end

 -- Merge two tables into a new table. If the are any duplicate keys, the values from the second overwrite the values from the first.
 local function mergeTables(first, second)
	local merged = {}
	for key, val in pairs(first) do
		merged[key] = val
	end
	for key, val in pairs(second) do
		merged[key] = val
	end
	return merged
 end

 local function toOpenTagString(selfClosedHtmlObject)
	local closedTagString = tostring(selfClosedHtmlObject)
	local openTagString = mw.ustring.gsub(closedTagString, ' />$', '>')
	return openTagString
 end

 local function normaliseHexTriplet(hexString)
	if not hexString then return nil end
	local hexComponent = mw.ustring.match(hexString, '^#(%x%x%x)$') or mw.ustring.match(hexString, '^#(%x%x%x%x%x%x)$')
	if hexComponent and #hexComponent == 6 then
		return mw.ustring.upper(hexString)
	end
	if hexComponent and #hexComponent == 3 then
		local r = mw.ustring.rep(mw.ustring.sub(hexComponent, 1, 1), 2)
		local g = mw.ustring.rep(mw.ustring.sub(hexComponent, 2, 2), 2)
		local b = mw.ustring.rep(mw.ustring.sub(hexComponent, 3, 3), 2)
		return '#' .. mw.ustring.upper(r .. g .. b)
	end
	return nil
 end

 ---------- Conversions ----------
 local function decimalToPaddedHex(number)
	local prefixedHex = hex.to_hex(tonumber(number)) -- prefixed with '0x'
	local padding = #prefixedHex == 3 and '0' or '' 
	return mw.ustring.gsub(prefixedHex, '0x', padding)
 end
 local function hexToDecimal(hexNumber)
	return tonumber(hexNumber, 16)
 end
 local function RGBtoHexTriplet(R, G, B)
	return '#' .. decimalToPaddedHex(R) .. decimalToPaddedHex(G) .. decimalToPaddedHex(B)
 end
 local function hexTripletToRGB(hexTriplet)
	local R_hex, G_hex, B_hex = string.match(hexTriplet, '(%x%x)(%x%x)(%x%x)')
	return hexToDecimal(R_hex), hexToDecimal(G_hex), hexToDecimal(B_hex)
 end
 local function HSVtoRGB(H, S, V) -- per [[HSL and HSV#Converting_to_RGB]]
	local C = V * S
	local H_prime = H / 60
	local X = C * ( 1 - math.abs(math.fmod(H_prime, 2) - 1) )
	local R1, G1, B1
	if H_prime <= 1 then
		R1 = C
		G1 = X
		B1 = 0
	elseif H_prime <= 2 then
		R1 = X
		G1 = C
		B1 = 0
	elseif H_prime <= 3 then
		R1 = 0
		G1 = C
		B1 = X
	elseif H_prime <= 4 then
		R1 = 0
		G1 = X
		B1 = C
	elseif H_prime <= 5 then
		R1 = X
		G1 = 0
		B1 = C
	elseif H_prime <= 6 then
		R1 = C
		G1 = 0
		B1 = X
	end	
	local m = V - C
	local R = R1 + m
	local G = G1 + m
	local B = B1 + m

	local R_255 = math.floor(R*255)
	local G_255 = math.floor(G*255)
	local B_255 = math.floor(B*255)
	return R_255, G_255, B_255
 end
 local function RGBtoHue(R_255, G_255, B_255) -- per [[HSL and HSV#Hue and chroma]]
	local R = R_255/255
	local G = G_255/255
	local B = B_255/255

	local M = math.max(R, G, B)
	local m = math.min(R, G, B)
	local C = M - m
	local H_prime
	if C == 0 then
		return null
	elseif M == R then
		H_prime = math.fmod(((G - B)/C + 6), 6) -- adding six before taking mod ensures positive value
	elseif M == G then
		H_prime = (B - R)/C + 2
	elseif M == B then
		H_prime = (R - G)/C + 4
	end
	local H = 60 * H_prime
	return H
 end
 local function nameToHexTriplet(name)
	if not name then return nil end
	local codename = mw.ustring.gsub(mw.ustring.lower(name), ' ', '')
	return namedColours[codename]
 end

 ---------- Choose colours ----------
 local function calculateColours(H, S, V, minContrast)
	local bgColour = RGBtoHexTriplet(HSVtoRGB(H, S, V))
	local textColour = colourContrastModule._greatercontrast({bgColour})
	local contrast = colourContrastModule._ratio({ bgColour, textColour })
	if contrast >= minContrast then
		return bgColour, textColour
	elseif textColour == '#FFFFFF' then
		-- make the background darker and slightly increase the saturation
		return calculateColours(H, math.min(1, S+0.005), math.max(0, V-0.03), minContrast)
	else
		-- make the background lighter and slightly decrease the saturation
		return calculateColours(H, math.max(0, S-0.005), math.min(1, V+0.03), minContrast)
	end
 end

 local function makeColours(hue, modeName)
	local mode = modes[modeName]
	local isGrey = not(hue)
	if isGrey then hue = 0 end

	local borderSat = isGrey and modes.grey.sat or 0.15
	local border = RGBtoHexTriplet(HSVtoRGB(hue, borderSat, 0.75))

	local titleSat = isGrey and modes.grey.sat or mode.sat
	local titleBackground, titleForeground = calculateColours(hue, titleSat, mode.val, min_contrast_ratio_large_text)

	local contentSat = isGrey and modes.grey.sat or modes.content.sat
	local contentBackground, contentForeground = calculateColours(hue, contentSat, modes.content.val, min_contrast_ratio_normal_text)

	return border, titleForeground, titleBackground, contentForeground, contentBackground
 end

 local function findHue(colour)
	local colourAsNumber = tonumber(colour)
	if colourAsNumber and ( -1 < colourAsNumber ) and ( colourAsNumber < 360) then
		return colourAsNumber
	end

	local colourAsHexTriplet = normaliseHexTriplet(colour) or nameToHexTriplet(colour)
	if colourAsHexTriplet then
		return RGBtoHue(hexTripletToRGB(colourAsHexTriplet))
	end

	return null
 end

 local function normaliseMode(mode)
	if not mode or not modes[mw.ustring.lower(mode)] or mw.ustring.lower(mode) == 'grey' then
		return 'normal'
	end
	return mw.ustring.lower(mode)
 end
 ---------- Build output ----------
 local function boxHeaderOuter(args)
	local baseStyle = {
		clear = 'both',
		['box-sizing'] = 'border-box',
		border = ( getParam(args, 'border-type') or 'solid' ) .. ' ' .. ( getParam(args, 'titleborder') or getParam(args, 'border') or '#ababab' ),
		background = getParam(args, 'titlebackground') or '#bcbcbc',
		color = getParam(args, 'titleforeground') or '#000',
		padding = getParam(args, 'padding') or '.1em',
		['text-align'] = getParam(args, 'title-align') or 'center',
		['font-family'] = getParam(args, 'font-family') or 'sans-serif',
		['font-size'] = getParam(args, 'titlefont-size') or '100%',
		['margin-bottom'] = '0px',
	}


	local tag = mw.html.create('div', {selfClosing = true})
		:addClass('box-header-title-container')
		:addClass('flex-columns-noflex')
		:css(baseStyle)
		:css('border-width', ( getParam(args, 'border-top') or getParam(args, 'border-width') or '1' ) .. 'px ' .. ( getParam(args, 'border-width') or '1' ) .. 'px 0')
		:css('padding-top', getParam(args, 'padding-top') or '.1em')
		:css('padding-left', getParam(args, 'padding-left') or '.1em')
		:css('padding-right', getParam(args, 'padding-right') or '.1em')
		:css('padding-bottom', getParam(args, 'padding-bottom') or '.1em')
		:css('moz-border-radius', getParam(args, 'title-border-radius') or '0')
		:css('webkit-border-radius', getParam(args, 'title-border-radius') or '0')
		:css('border-radius', getParam(args, 'title-border-radius') or '0')
	return toOpenTagString(tag)
 end

 local function boxHeaderTopLinks(args)
	local style = {
		float = 'right',
		['margin-bottom'] = '.1em',
		['font-size'] = getParam(args, 'font-size') or '80%',
		color = getParam(args, 'titleforeground') or '#000'
	}
	local tag = mw.html.create('div', {selfClosing = true})
		:addClass('plainlinks noprint' )
		:css(style)
	return toOpenTagString(tag)
 end

 local function boxHeaderEditLink(args)
	local page = getParam(args, 'editpage')
	if not page or page == '{{{2}}}'
	then
		return ''
	end
	local style = {
		color = getParam(args, 'titleforeground') or '#000'
	}
	local tag = mw.html.create('span')
		:css(style)
		:wikitext('edit')
	local linktext = tostring(tag)
	local linktarget = tostring(mw.uri.fullUrl(page, {action='edit', section=getParam(args, 'section')}))
	return '[' .. linktarget .. ' ' .. linktext .. ']&nbsp;'
 end

 local function boxHeaderViewLink(args)
	local style = {
		color = getParam(args, 'titleforeground') or '#000'
	}
	local tag = mw.html.create('span')
		:css(style)
		:wikitext('view')
	local linktext = tostring(tag)
	local linktarget = ':' .. getParam(args, 'viewpage')
	return "<b>·</b>&nbsp;[[" .. linktarget .. '|' .. linktext .. ']]&nbsp;'
 end

 local function boxHeaderTitle(args)
	local baseStyle = {
		['font-family'] = getParam(args, 'title-font-family') or 'sans-serif',
		['font-size'] = getParam(args, 'title-font-size') or '100%',
		['font-weight'] = getParam(args, 'title-font-weight') or 'bold',
		border = 'none',
		margin = '0',
		padding = '0',
		color = getParam(args, 'titleforeground') or '#000';
	}
	local tagName = getParam(args, 'SPAN') and 'span' or 'h2'
	local tag = mw.html.create(tagName)
		:css(baseStyle)
		:css('padding-bottom', '.1em')
		:wikitext(getParam(args, 'title'))
	if getParam(args, 'extra') then
		local rules = mw.text.split(getParam(args, 'extra'), ';', true)
		for _, rule in pairs(rules) do
			local parts = mw.text.split(rule, ':', true)
			local prop = parts[1]
			local val = parts[2]
			if prop and val then
				tag:css(prop, val)
			end
		end
	end
	return tostring(tag)
 end

 local function boxBody(args)
	local baseStyle = {
		['box-sizing'] = 'border-box',
		border = ( getParam(args, 'border-width') or '1' ) .. 'px solid ' .. ( getParam(args, 'border') or '#ababab'),
		['vertical-align'] = 'top';
		background = getParam(args, 'background') or '#fefeef',
		opacity = getParam(args, 'background-opacity') or '1',
		color = getParam(args, 'foreground') or '#000',
		['text-align'] = getParam(args, 'text-align') or 'left',
		margin = '0 0 10px',
		padding = getParam(args, 'padding') or '1em',
	}
	local tag = mw.html.create('div', {selfClosing = true})
		:css(baseStyle)
		:css('border-top-width', ( getParam(args, 'border-top') or '1' ) .. 'px')
		:css('padding-top', getParam(args, 'padding-top') or '.3em')
		:css('border-radius', getParam(args, 'border-radius') or '0')
	return toOpenTagString(tag)
 end

 local function contrastCategories(args)
	local cats = ''

	local titleText = nameToHexTriplet(getParam(args, 'titleforeground')) or normaliseHexTriplet(getParam(args, 'titleforeground')) or '#000000'
	local titleBackground = nameToHexTriplet(getParam(args, 'titlebackground')) or normaliseHexTriplet(getParam(args, 'titlebackground')) or '#bcbcbc'
	local titleContrast = colourContrastModule._ratio({titleBackground, titleText})
	local insufficientTitleContrast = type(titleContrast) == 'number' and ( titleContrast < min_contrast_ratio_large_text )

	local bodyText = nameToHexTriplet(getParam(args, 'foreground')) or normaliseHexTriplet(getParam(args, 'foreground')) or '#000000'
	local bodyBackground = nameToHexTriplet(getParam(args, 'background')) or normaliseHexTriplet(getParam(args, 'background')) or '#fefeef'
	local bodyContrast = colourContrastModule._ratio({bodyBackground, bodyText})
	local insufficientBodyContrast = type(bodyContrast) == 'number' and ( bodyContrast < min_contrast_ratio_normal_text )

	if insufficientTitleContrast and insufficientBodyContrast then
		return '[[Category:Box-header with insufficient title contrast]][[Category:Box-header with insufficient body contrast]]'
	elseif insufficientTitleContrast then
		return '[[Category:Box-header with insufficient title contrast]]'
	elseif insufficientBodyContrast then
		return '[[Category:Box-header with insufficient body contrast]]'
	else
		return ''
	end
 end

 ---------- Main functions / entry points ----------

 -- Entry point for templates (manually-specified colours)
 function p.boxHeader(frame)
	local args = getArgs(frame)
	local page = args.editpage
	if not args.editpage or args.editpage == '' then
		page = mw.title.getCurrentTitle().prefixedText
	end
	local output = p._boxHeader(args, page)
	if mw.ustring.find(output, '{') then
		return frame:preprocess(output)
	end
	return output
 end

 -- Entry point for modules (manually-specified colours)
 function p._boxHeader(_args, page)
	local args = setCleanArgs(_args)
	if page and not args.editpage then
		args.editpage = page
	end
	if not args.title then
		args.title = '{{{title}}}'
	end
	local output = {}
	table.insert(output, boxHeaderOuter(args))
	if not getParam(args, 'EDITLINK') then
		table.insert(output, boxHeaderTopLinks(args))
		if not getParam(args, 'noedit') then
			table.insert(output, boxHeaderEditLink(args))
		end
		if getParam(args, 'viewpage') then
			table.insert(output, boxHeaderViewLink(args))
		end
		if getParam(args, 'top') then
			table.insert(output, getParam(args, 'top') .. '&nbsp;')
		end
		table.insert(output, '</div>')
	end
	table.insert(output, boxHeaderTitle(args))
	table.insert(output, '</div>')
	table.insert(output, boxBody(args))
	if not getParam(args, 'TOC') then
		table.insert(output, '__NOTOC__')
	end
	if not getParam(args, 'EDIT') then
		table.insert(output, '__NOEDITSECTION__')
	end
	table.insert(output, contrastCategories(args))

	return table.concat(output)
 end

 -- Entry point for templates (automatically calculated colours)
 function p.autoColour(frame)
	local args = getArgs(frame)
	local colourParam = getParam(args, 'colour')
	local generatedColour = nil
	if not colourParam or colourParam == '' then
		-- convert the root page name into a number and use that
		local root = mw.title.getCurrentTitle().rootPageTitle.prefixedText
		local rootStart = mw.ustring.sub(root, 1, 12)
		local digitsFromRootStart = mw.ustring.gsub(rootStart, ".", function(s) return math.fmod(string.byte(s, 2) or string.byte(s, 1), 10) end)
		local numberFromRoot = tonumber(digitsFromRootStart, 10)
		generatedColour = math.fmod(numberFromRoot, 360)
	end
	local output = p._autoColour(args, generatedColour)
	if mw.ustring.find(output, '{') then
		return frame:preprocess(output)
	end
	return output
 end

 -- Entry point for modules (automatically calculated colours)
 function p._autoColour(_args, generatedColour)
	local args = setCleanArgs(_args)
	local hue = generatedColour or findHue(getParam(args, 'colour'))
	local mode = normaliseMode(getParam(args, 'mode'))
	local border, titleForeground, titleBackground, contentForeground, contentBackground = makeColours(hue, mode)
	local boxTemplateArgs = mergeTables(args, {
		title = getParam(args, '1') or '{{{1}}}',
		editpage = getParam(args, '2') or '',
		noedit = getParam(args, '2') and '' or 'yes',
		border = border,
		titleforeground = titleForeground,
		titlebackground = titleBackground,
		foreground = contentForeground,
		background = contentBackground
	})
	return p._boxHeader(boxTemplateArgs)
 end
	
 return p