-- images-handling.lua
-- SPDX-FileCopyrightText: 2023–2025 toastal <toastal@posteo.net>
-- SPDX-License-Identifier: MPL-2.0

Plugin.require_version("4.4.0")

function append_dimensions(og_elem, src)
	local local_path = Sys.join_path_unix(build_dir, src)
	if Sys.file_exists(local_path) then
		local exif_output = Sys.get_program_output(format("exiftool %s -s -ImageSize | gawk -F ':' '{print $2}'", local_path))
		if exif_output then
			local trimmed_exif_output = String.trim(exif_output)
			local dims = Regex.split(trimmed_exif_output, "x")
			if size(dims) == 2 then
				HTML.set_attribute(og_elem, "width", dims[1])
				HTML.set_attribute(og_elem, "height", dims[2])
			else
				Log.warning(format("Invalid size `%s` for `%s`", trimmed_exif_output, local_path))
			end
		else
			Log.warning(format("Missing image size for `%s`", local_path))
		end
	end
end

function is_smaller_size_by(ext, percent, old, new)
	if (not Value.is_int(old)) or (not Value.is_int(new)) or new < 1 then
		return false
	else
		local diff = 1.0 - ((new + 0.0) / (old + 0.0))
		return (percent + 0.0) < diff
	end
end

function append_2x(og_elem, og_src)
	local has_srcset = HTML.get_attribute(og_elem, "srcset")
	-- bail if srcset exists
	if not has_srcset then
		local extension = Sys.get_extension(og_src)
		local hi_path = Sys.strip_extensions(og_src) .. "@2x." .. extension
		-- BUG: this includes `/` as well as no Windows support 🤷
		local hi_local_path = Sys.join_path_unix(build_dir, hi_path)
		if Sys.get_file_size(hi_local_path) then
			HTML.set_attribute(og_elem, "srcset", hi_path .. " 2x")
		end
	end
end

function append_source(picture, og_src, og_file_size, extension, mime_type)
	if Sys.get_extension(og_src) ~= extension then
		local alt_path = Sys.strip_extensions(og_src) .. "." .. extension
		-- BUG: this includes `/` as well as no Windows support 🤷
		local alt_local_path = Sys.join_path_unix(build_dir, alt_path)
		local srcset = ""
		if Sys.file_exists(alt_local_path) then
			local asset_file_size = Sys.get_file_size(alt_local_path)
			local alt_path_2x = Sys.strip_extensions(og_src) .. "@2x." .. extension
			-- BUG: this includes `/` as well as no Windows support 🤷
			local alt_local_path_2x = Sys.join_path_unix(build_dir, alt_path_2x)
			local alt_2x_exists = Sys.file_exists(alt_local_path_2x)
			if is_smaller_size_by(extension, 0.05, og_file_size, asset_file_size) then
				local source = HTML.create_element("source")
				local srcset = alt_path
				if alt_2x_exists then
					srcset = srcset .. ", " .. alt_path_2x .. " 2x"
				end
				HTML.set_attribute(source, "srcset", srcset)
				HTML.set_attribute(source, "type", mime_type)
				HTML.prepend_child(picture, source)
			else
				-- If we ain’t using it, then it’s best to delete it
				Sys.delete_file(alt_local_path)
				if alt_2x_exists then
					Sys.delete_file(alt_local_path_2x)
				end
			end
		end
	end
end

function process_img(elem)
	local parent = HTML.parent(elem)
	local picture = HTML.create_element("picture")
	local og_class = HTML.get_attribute(elem, "class")
	if og_class then
		HTML.set_attribute(picture, "class", og_class)
	end
	HTML.delete_attribute(elem, "class")
	HTML.append_child(picture, elem)

	-- append empty alt if missing
	if Value.is_nil(HTML.get_attribute(elem, "alt")) then
		HTML.set_attribute(elem, "alt", "")
	end

	local src = HTML.get_attribute(elem, "src")
	local file_size = Sys.get_file_size(Sys.join_path(build_dir, src))
	if Value.is_int(file_size) then
		append_dimensions(elem, src)
		append_2x(elem, src)
		append_source(picture, src, file_size, "jxl", "image/jxl")
	else
		Log.warning(format("Image not found or wrong permissions or empty for “%s”; skipping.", src))
	end

	HTML.prepend_child(parent, picture)
end

Table.iter_values(process_img, HTML.select(page, "img[src^=\"/\"]"))