local templatestyles = 'Module:Sandbox/Synpath/styles.css'
local getArgs = require('Module:Arguments').getArgs
local tracking, preview = {}, {}
local p = {}

local function isImage(input_string)
	--adapted from Module:Gallery 09-02-2025
    local input_string = input_string:lower() -- Case insensitive check

    -- Check if it starts with "File:", "Image:", or "Media:"
    local _, prefix = input_string:match("^(%[%[)?(%a-):")
    if prefix and (prefix == "file" or prefix == "image" or prefix == "media") then
        return true
    end
    
    local valid_extensions = {
        "apng", "djvu", "flac", "gif", "jfi", "jfif", "jif", "jpe", "jpeg", "jpg",
        "m1a", "m1v", "m2a", "m2v", "mid", "mp1", "mp2", "mp3", "mpa", "mpe", "mpeg", "mpg",
        "mpv", "oga", "ogg", "ogv", "opus", "pdf", "png", "stl", "svg", "svgz", "tif", "tiff",
        "wav", "wave", "webm", "webp", "xcf"
    }
    
    -- Extract file extension, of 3 or 4 characters only
    local ext = file:match("%.(%w%w%w%w?)$")
    
    -- Check if the extension is in the valid list
    if ext then
        for _, valid_ext in ipairs(valid_extensions) do
            if ext == valid_ext then
            	table.insert(tracking, '[[Category:Pages using gallery without a media namespace prefix]]')
                return true
            end
        end
    end
    return false
end

local function checkarg(k,v,previouskind)
	--I'm sure there's a better way to do this, but just make it work for now
	if k and type(k) == 'string' and v and v ~= '' then
		if k:match('^%d+$') then
			--unparameterized values are treated as captions when following an image
			--unless they have a valid file extension or namespace
			if previouskind == 'image' or previouskind == 'unparameterized_image' 
				and isImage(v) == false then
				return 'unparameterized_caption'
			else
				--assume here that the user has entered wikitext of an image
				return 'unparameterized_image'
			end
		elseif k:match('^image%d+$') then
			--assume here that the user has entered wikitext of an image
			return 'image'
		elseif k:match('^caption%d+$') then
			--just for clarity/readability
			return 'caption'
		elseif k == 'containerclass' or k == 'itemclass' or k == 'imageclass' 
			or k == 'captionclass' or k == 'widths' or k == 'heights' 
			or k == 'itemstyles' or k == 'imagestyles' or k =='captionstyles' 
			or k == 'mode' or k:match('^class%d+$') then
			return 'string'
		--else
			-- invalid, omit error tracking categorization for now
			--adapted from Module:Gallery 09-02-2025
			--local vlen = mw.ustring.len(k)
			--k = mw.ustring.sub(k, 1, (vlen < 25) and vlen or 25)
			--k = mw.ustring.gsub(k, '[^%w%-_ ]', '?')
			--table.insert(tracking, '[[Category:Pages using gallery with unknown parameters|' .. k .. ']]')
			--table.insert(preview, '"' .. k .. '"')
		end
	end
	return 'invalid'
end

local function file_affixes(file_wikitext)
	--[[
	prepend two open brackets or "File:" and append two closing brackets as needed
	]]--
	local prefix5 = file_wikitext:sub(1,5):lower()
	local prefix6 = file_wikitext:sub(1,6):lower()
	
	if file_wikitext:sub(1,2) == "[[" then
		return file_wikitext --just assume the editor wrote their wikitext right
	elseif prefix5 == "file:" or prefix6 == "media:" or prefix6 == "image:" then
		return "[[" .. file_wikitext .. "]]"
	else
		return "[[File:" .. file_wikitext .. "]]"
	end
end

local function add_gallery_flex_item(args, tbl, image, caption)
	tbl
		:tag('div')
		:addClass('mod-gallery-flex-item')
		:addClass(args.itemclass)
		:css('width', args.widths)
		:css('style', args.itemstyles) --for one off exceptions
		:tag('div')
			:addClass('mod-gallery-flexbox-image')
			:addClass(args.imageclass)
			:css('height', args.heights)
			:css('style', args.imagestyles) --for one off exceptions
			:wikitext(image)
			:done()
		:tag('div')
			:addClass('mod-gallery-flexbox-caption')
			:addClass(args.captionclass)
			:css('style', args.captionstyles) --for one off exceptions
			:wikitext(caption)
			:done()
		:done() --end div; flex-item
end

local function add_gallery_flex_item_no_caption(args, tbl, image)
	tbl
		:tag('div')
		:addClass('mod-gallery-flex-item')
		:addClass(args.itemclass)
		:css('width', args.widths)
		:css('style', args.itemstyles) --for one off exceptions
		:tag('div')
			:addClass('mod-gallery-flexbox-image')
			:addClass(args.imageclass)
			:css('height', args.heights)
			:css('style', args.imagestyles) --for one off exceptions
			:wikitext(image)
			:done()
		:done() --end div; flex-item
end

local function _galleryflexbox(passedargs, frame)
    -- check parameters and reassign those that have values
    error(error(table.concat(passedargs, ',')))
    local args = {}
    local unparameterized_images = {}
    local unparameterized_captions = {}
    local N_images = 0
    local N_un_img = 0
    local argkind = 'invalid'
    local prevkind = 'invalid'
    
    for k, v in pairs(passedargs) do
    	argkind = checkarg(k,v) --also adds invalid parameter tracking
    	
    	if argkind == 'image' then
    		prevkind = 'image'
    		N_images = N_images + 1
    		args[k] = file_affixes(v)
    	elseif argkind == 'unparameterized_image' then
    		prevkind = 'unparameterized_image'
    		N_un_img = N_un_img + 1
    		unparameterized_images[N_un_img] = file_affixes(v)
    	elseif argkind == 'caption' then
    		prevkind = 'caption'
    		args[k] = v
    	elseif argkind == 'unparameterized_caption' and prevkind == 'unparameterized_image'  then
    		prevkind = 'unparameterized_caption'
    		unparameterized_captions[N_un_img] = v
    	elseif argkind == 'string' then --valid, named parameters
    		args[k] = v
    	end
	end
	
	-- generate flexbox html
	local tbl = mw.html.create('div')
	tbl:addClass('mod-gallery-flexbox')
	
	if args.containerclass == nil then
		tbl:addClass('mod-gallery-flexbox-default')
	elseif args.mode then
		tbl:addClass('mod-gallery-flexbox-' .. args.mode)
	else
		tbl:addClass(args.containerclass)
	end

	for i = 1, N_images do --repeat for each named image (i.e. image(n))
		add_gallery_flex_item(args, tbl, args['image' .. i], args['caption' .. i])
		--[[
		tbl
			:tag('div')
			:addClass('mod-gallery-flex-item')
			:addClass(args.itemclass)
			:css('width', args.widths)
			:css('style', args.itemstyles) --for one off exceptions
			:tag('div')
				:addClass('mod-gallery-flexbox-image')
				:addClass(args.imageclass)
				:css('height', args.heights)
				:css('style', args.imagestyles) --for one off exceptions
				:wikitext(args['image' .. i])
				:done()
			:tag('div')
				:addClass('mod-gallery-flexbox-caption')
				:addClass(args.captionclass)
				:css('style', args.captionstyles) --for one off exceptions
				:wikitext(args['caption' .. i])
				:done()
			:done() --end div; flex-item
		]]--
	end
	for i = 1, N_un_img do --repeat for each unnamed image (i.e. image(n))
		add_gallery_flex_item(args, tbl, unparameterized_images[i], unparameterized_captions[i])
	end
	
	-- error tracking 
	local trackstr = (#tracking > 0) and table.concat(tracking, '') or ''
	if #preview > 0 then
		trackstr = require('Module:If preview')._warning({
			'Unknown parameters ' .. table.concat(preview, '; ') .. '.'
		}) .. trackstr
	end
	
	return frame:extensionTag{ name = 'templatestyles', args = { src = templatestyles} } .. tostring(tbl) .. trackstr
end

function p.main(frame)
	local args = getArgs(frame)
	return _galleryflexbox(args, frame)
end

return p