-- Local version of string formatting function
local format = mw.ustring.format
-- Local version of string trimming function
local trim = mw.text.trim
-- Store this function in a local variable to avoid expensive table lookups.
local insert = table.insert

-- mw.html object for the generated row
local row
-- Default row span for all columns (`jspan` = "junction span")
local jspan
-- Any error messages produced that will be added to the output
local errorMsg = {}

-- A specification for self-closing HTML tag.
local selfClosing = {selfClosing = true}

---
-- Converts the distance specified in unit from `unit` specified in `unitdef`
-- to the other supported unit.
local function convert
	if unit == nil or unitdef == nil then return {} end

	-- Import module to convert length.
	local util = require("Module:Road data/util")
	local lengths = util.convertLengths({[unitdef] = unit})
	if lengths.error then -- An error occurred during conversion.
		-- Add the transcluding page to an error tracking category.
		local page = mw.title.getCurrentTitle -- Get transcluding page's title
		local pagename = page.prefixedText -- Extract page's full title as string
		-- Create category string
		local category = format
		insert -- Add error category to error message table.
	end
	return lengths
end

--- Creates cells for the location columns.
local function locations(args)
	-- Unitary, e.g., state line
	local unitary = args.unitary -- Value to span all of the location columns
	if unitary then
		-- Text alignment of the cell contents, default to "left".
		local align = args.unitary_align or 'left'
		row:tag('td') -- Create unitary cell
		return
	end

	-- Create cells for regular location columns.

	-- Region, for disambiguation and potentially for display
	local region = args.region
	if region or args.region_special then
		-- Row span for region; must be specified to display a region cell.
		local regionSpan = args.regionspan
		if regionSpan then
			row:tag('td') -- Create a region cell
				-- Store region text in the cell.
				-- `region_special` argument overrides wikilinked `region` argument.
		end
	end

	-- Primary topic requires no specialization to supplied locations.
	local primaryTopic = args.primary_topic ~= 'no'

	-- Note below main text in the next column
	local sub1note = args.sub1_note -- check existence later
	-- Row span for the last location column, default to `jspan`
	local sub2span = args.sub2span or jspan

	-- Independent city
	local indepCityText -- Value to span both subdivision columns.
	if args.indep_city_special then
		indepCityText = args.indep_city_special -- Overrides `indep_city` argument.
	elseif args.indep_city then
		local indepCity = args.indep_city
		local cityLink -- Wikilink for independent city
		if primaryTopic then
			cityLink = format
		elseif region then
			-- Specialize independent city to the region.
			cityLink = format
		end
		if cityLink then
			indepCityText = "City of " .. cityLink
		end
	end
	if indepCityText then -- Display independent city.
		-- Text alignment of the cell contents, default to "left".
		local align = args.indep_city_align or 'left'
		local indepCityCell = row:tag('td') -- Create independent city cell
		if sub1note then -- A note is provided.
			indepCityCell:tag -- Add a line break to the cell.
			-- Add the note to the cell, within an HTML  tag.
			indepCityCell:tag('small'):wikitext(sub1note)
		end
		return
	end

	-- Create two cells for the first- and second-level subdivisions.

	-- First-level subdivision, e.g., county
	-- Name of the type of subdivision, e.g., "County" and "Parish"
	local sub1name = args.sub1name -- check existence later
	local sub1Text -- Value for first-level subdivision column.
	if args.sub1_special then
		sub1Text = args.sub1_special -- Overrides `sub1` argument.
	elseif args.sub1 then
		local sub1 = args.sub1
		if primaryTopic then
			-- Add type (if specified) to wikilink for first-level subdivision.
			local sub1Link = sub1name and format or sub1
			sub1Text = format
		elseif region and sub1name then
			-- Add type to first-level subdivision.
			local sub1Typed = trim(format)
			-- Specialize first-level subdivision, with type added, to the region.
			sub1Text = format
		end
	end
	if sub1Text then -- Display first-level subdivision.
		-- Row span for first-level subdivision, default to `jspan`.
		local sub1span = args.sub1span or jspan
		local sub1Cell = row:tag('td') -- Create first-level subdivision cell
		if sub1note then -- A note is provided.
			sub1Cell:tag -- Add a line break to the cell.
			-- Add the note to the cell, within an HTML  tag.
			sub1Cell:tag('small'):wikitext(sub1note)
		end
	end

	-- Second-level subdivision, e.g., city and town
	local sub2Text -- Value for second-level subdivision column.
	if args.sub2_special then
		sub2Text = args.sub2_special -- Overrides `sub2` argument.
	elseif args.sub2 then
		local sub2 = args.sub2
		if sub2 == "none" or sub2 == "&nbsp;" then
			sub2Text = "&#8203;" -- Zero-width space
		elseif primaryTopic then
			sub2Text = format
		else
			local sub2Link = {sub2}
			local sub2Name = sub2
			-- Type of area, e.g., city and village, as a form of disambiguation
			local area = args.area
			if area then
				insert(sub2Link, format(' (%s)', area)) -- Add area to wikilink.
				local areas = { -- table of different area types
					borough = "Borough",
					city = "City",
					community = "Community",
					CDP = "Community",
					hamlet = "Hamlet",
					town = "Town",
					village = "Village",
					["unorganized territory"] = "Unorganized Territory"
				-- Add area name to displayed wikitext.
				sub2Name = format
			end
			insert
			-- Some second-level subdivisions are not unique in a given region.
			-- `sub1dab` is the first-level subdivision to be used for disambiguation.
			local sub1dab = args.sub1dab 
			if sub1dab and sub1name then
				insert(sub2Link, trim(format) .. ", ")
			end
			if region then
				insert -- Add region to wikilink
			end

			sub2Text = format("%s", table.concat(sub2Link), sub2Name)
		end
	end
	if sub2Text then -- Display second-level subdivision.
		row:tag('td') -- Create second-level subdivision cell
	end
end

--- Creates cells for the distance columns.
local function units(args)
	-- Alternate units, e.g., California's postmiles.
	local alt_unit = args.altunit
	if alt_unit then -- Alternate units override standard units.
		-- Row span (`auspan` = "alt[ernate] unit span")
		local auspan = args.auspan or jspan
		-- Create the alternate unit cell as a header cell for the row,
		-- since it is usually unique within the table.
		row:tag('th'):attr
	else
		-- Convert numeric distances to a secondary unit, and display both units.
		-- Distance in the primary unit, or 'none'
		local unit = args.unit
		-- If `unit` is "none", no cells are displayed.
		if unit == "none" then return end
		local unitdef = args.unitdef or "km" -- The primary unit ('mi' or 'km')
		-- Convert and format the distance.
		local lengths = convert
		-- Row span (`uspan` = "unit span")
		local uspan = args.uspan or jspan
		-- Create the primary unit cell as a header cell for the row,
		-- since it is usually unique within the table.
		local primary = row:tag('th'):attr
			-- Store the primary distance and any conversion error message in the cell.
		local secondary = row:tag('td') -- Create the secondary unit cell.

		local unit_ref = args.unit_ref
		if unit_ref then -- A reference is provided for the distance.
			primary:wikitext(unit_ref) -- Add reference to the primary distance cell.
		end

		local unit2 = args.unit2
		if unit2 then -- A second distance is provided.
			local line = args.line -- A horizontal rule may be requested between the distances.
			if line then
				-- Add a horizontal rule to both cells.
				primary:tag
				secondary:tag
			else
				-- Add an en-dash and a line break to both cells.
				primary:wikitext('–'):tag
				secondary:wikitext('–'):tag
			end
			-- Convert and format the second distance.
			local lengths2 = convert
			-- Add the second distance and any conversion error message to the primary distance cell.
			primary:wikitext
			-- Add the converted second distance to the secondary distance cell.
			secondary:wikitext(lengths2[lengths2.comp])
			end
		
		local unit2_ref = args.unit2_ref
		if unit2_ref then -- A reference is provided for the distance.
			primary:wikitext(unit2_ref) -- Add reference to the primary distance cell.
		end
	end
end

-- Color specified by any supplied type
local color
-- Tooltip specified by any supplied type
local title

--- Apply any type-derived coloring and tooltip to the given cell.
local function applyTypeStyle(cell)
	cell:attr:css
end

--- Creates a cell for places, such as bridges and rest areas.
local function place(args)
	local place = args.place -- Contents of the place cell
	-- Do nothing if `place` is "none"
	if place == "none" then return end
	local colspan = 2 -- Initial column span
	local exit = args[1] -- Whether this table has exit number columns
	local named = args[2] -- Whether this table has named junction column
	-- Adjust column span
	if exit == "old" then colspan = colspan + 2
	elseif exit == "exit" then colspan = colspan + 1
	end
	if named == "name" then colspan = colspan + 1 end
	-- Row span (`pspan` = "place span")
	local pspan = args.pspan or jspan
	local placeCell = row:tag('td') -- Create place cell
	applyTypeStyle(placeCell)
end

--- Creates cells for exit number and named junction columns.
local function exits(args)
	local exit = args[1] -- 'exit', 'old', or nil
	local named = args[2] -- 'name' or nil

	if exit == 'old' then -- Add old exit number cell
		-- Row span (`ospan` = "old span")
		local ospan = args.ospan or jspan
		row:tag('td') -- Create old exit number cell
	end

	if exit then -- "exit" or "old" is defined; add current exit number cell
		-- Row span (`espan` = "exit span")
		local espan = args.espan or jspan
		local exitCell = row:tag('td') -- Create exit number cell
		applyTypeStyle(exitCell)
	end

	if named then -- Junction list has a junction name column
		local namespan = args.namespan or jspan -- Row span
		local nameCell = row:tag('td') -- Create junction name cell
		applyTypeStyle(nameCell)
	end
end

--- Creates cell for the destinations column.
local function destinations(args)
	local road = args.road -- Contents of the destinations cell
	-- Do nothing if `road` is "none"
	if road == "none" then return end
	-- Column span (`rcspan` = "road column span"), default to 1
	local rcspan = args.rcspan or 1
	-- Row span (`rspan` = "road span")
	local rspan = args.rspan or jspan
	local destCell = row:tag('td') -- Create destination cell
	applyTypeStyle(destCell)
end

--- Creates cell for the notes column.
local function notes(args)
	local notes = args.notes -- Contents of the notes cell
	-- Do nothing if `notes` is "none"
	if notes == "none" then return end
	-- Row span (`nspan` = "notes span")
	local nspan = args.nspan or jspan
	local notesCell = row:tag('td') -- Create notes cell
	applyTypeStyle(notesCell)
end

---
-- Returns a row in the junction list.
-- Accessible from other Lua modules
function p._jctint(args)
	jspan = args.jspan or 1 -- Global row span for all columns; defaults to 1
	-- } argument to determine color and tooltips
	local argType = args.type
	if argType then -- } was passed
		-- Type-based data for colors and tooltips
		if argType == 'mplex' then
			local page = mw.title.getCurrentTitle -- Get transcluding page's title
			local pagename = page.prefixedText -- Extract page's full title as string
			insert(errorMsg,
				format)
		end
		local types = mw.loadData("Module:Road data/RJL types")
		local typeData = types[string.lower(argType)] -- Retrieve the type data
		if typeData then
			color = typeData.color -- Store the color globally
			title = typeData.jctint -- Store the tooltip globally
		else
			-- Add error category to error message table.
			local page = mw.title.getCurrentTitle -- Get transcluding page's title
			local pagename = page.prefixedText -- Extract page's full title as string
			insert(errorMsg,
				format)
		end
	end

	local root = mw.html.create -- Create the root mw.html object to return
	-- Create the table row and store it globally
	row = root:tag('tr'):css

	locations(args) -- Handle location arguments
	units(args) -- Handle distance arguments
	if args.place then -- } spans all columns to the right of the distances
		place(args) -- Create cell for place
	else
		exits(args) -- Handle exit/named junction arguments
		destinations(args) -- Handle destinations
		notes(args) -- Handle notes
	end

	-- Return the HTML code in the mw.html object as a string, plus any error messages
	return tostring(root) .. table.concat(errorMsg)
end

--- Entry function for 
function p.jctint(frame)
	-- Import module function to work with passed arguments
	local getArgs = require('Module:Arguments').getArgs
	-- Gather passed arguments into easy-to-use table
	local args = getArgs(frame)
	return p._jctint(args)
end