local M = {}

M.proto = "http"

local function isHttp()
	return M.proto == "http"
end

local function isGemini()
	return M.proto == "gemini"
end

local function esc(s)
	s = s or ""
	s = s:gsub("&", "&")
	s = s:gsub("<", "&lt;")
	s = s:gsub(">", "&gt;")
	return s
end

M.p = function(s)
	s = s or ""
	if isHttp() then
		return "<p>" .. esc(s) .. "</p>"
	elseif isGemini() then
		return s
	end
end

M.h = function(level, s)
	level = tonumber(level) or 1
	if level < 1 then level = 1 end
	if level > 6 then level = 6 end
	s = s or ""
	if isHttp() then
		return "<h" .. level .. ">" .. esc(s) .. "</h" .. level .. ">"
	elseif isGemini() then
		return string.rep("#", level) .. " " .. s
	end
end

M.codeblock = function(s)
	s = s or ""
	if isHttp() then
		return "<pre><code>" .. esc(s) .. "</code></pre>"
	elseif isGemini() then
		return "```\n" .. s .. "\n```"
	end
end

M.inline = function(s)
	s = s or ""
	if isHttp() then
		return "<code>" .. esc(s) .. "</code>"
	elseif isGemini() then
		return "`" .. s .. "`"
	end
end

M.link = function(text, url)
	text = text or ""
	url = url or ""
	if isHttp() then
		return "<a href=\"" .. esc(url) .. "\">" .. esc(text) .. "</a>"
	elseif isGemini() then
		return "=> " .. url .. " " .. text
	end
end

M.list = function(items, ordered)
	items = items or {}
	if isHttp() then
		local tag = ordered and "ol" or "ul"
		local out = "<" .. tag .. ">"
		for _, v in ipairs(items) do
			out = out .. "<li>" .. esc(v) .. "</li>"
		end
		out = out .. "</" .. tag .. ">"
		return out
	elseif isGemini() then
		local out = {}
		for i, v in ipairs(items) do
			if ordered then
				table.insert(out, i .. ". " .. v)
			else
				table.insert(out, "* " .. v)
			end
		end
		return table.concat(out, "\n")
	end
end

M.blockquote = function(s)
	s = s or ""
	if isHttp() then
		return "<blockquote>" .. esc(s) .. "</blockquote>"
	elseif isGemini() then
		return "> " .. s
	end
end

M.rule = function()
	if isHttp() then
		return "<hr />"
	elseif isGemini() then
		return "---"
	end
end

M.image = function(alt, src)
	alt = alt or ""
	src = src or ""
	if isHttp() then
		return "<img src=\"" .. esc(src) .. "\" alt=\"" .. esc(alt) .. "\" />"
	elseif isGemini() then
		return "=> " .. src .. " " .. alt
	end
end

M.file = function(text, url)
	text = text or ""
	url = url or ""
	if isHttp() then
		return "<a href=\"" .. esc(url) .. "\" download>" .. esc(text) .. "</a>"
	elseif isGemini() then
		return "=> " .. url .. " " .. text
	end
end

M.note = function(text)
	text = text or ""
	if isHttp() then
		return "<div class=\"note\">" .. esc(text) .. "</div>"
	elseif isGemini() then
		local width = 31

		local function wrap_line(line)
			local out = {}
			local i = 1
			local len = #line

			if len == 0 then
				out[#out + 1] = ""
				return out
			end

			while i <= len do
				out[#out + 1] = line:sub(i, i + width - 1)
				i = i + width
			end

			return out
		end

		local lines = {}

		for line in (text .. "\n"):gmatch("(.-)\n") do
			local wrapped = wrap_line(line)
			for _, w in ipairs(wrapped) do
				lines[#lines + 1] = w
			end
		end

		local border = "+" .. string.rep("=", width + 2) .. "+"
		local empty = "|" .. string.rep(" ", width + 2) .. "|"

		local out = {}
		out[#out + 1] = border
		out[#out + 1] = empty

		for _, line in ipairs(lines) do
			local padding = width - #line
			out[#out + 1] = "| " .. line .. string.rep(" ", padding) .. " |"
		end

		out[#out + 1] = empty
		out[#out + 1] = border

		return table.concat(out, "\n")
	end
end

return M