local M = {}
local api = vim.api
local buf, win

local function open_window()
	buf = api.nvim_create_buf(false, true)

	api.nvim_buf_set_option(buf, "bufhidden", "wipe")

	-- get dimensions
	local width = api.nvim_get_option("columns")
	local height = api.nvim_get_option("lines")

	-- calculate our floating window size
	local win_height = math.ceil(height * 0.8 - 4)
	local win_width = math.ceil(width * 0.9)

	-- and its starting position
	local row = math.ceil((height - win_height) / 2 - 1)
	local col = math.ceil((width - win_width) / 2)

	-- set some options
	local opts = {
		style = "minimal",
		relative = "editor",
		width = win_width,
		height = win_height,
		row = row,
		col = col,
	}

	-- and finally create it with buffer attached
	win = api.nvim_open_win(buf, true, opts)
end

local function httprequest(url)
	local command = string.format("wget -q -O - '%s'", url)

	local handle = io.popen(command)
	local response = ""
	if handle ~= nil then
		response = handle:read("*a")
		handle:close()
	else
		response = "ERROR"
	end

	return response
end

function M.lookup()
	local keywords = vim.fn.getreg("*") -- receive yanked text
	local url = "https://dl.acm.org/action/doSearch?AllField=" .. keywords
	url, empty = url:gsub(" ", "+")
	open_window()

	-- enable write to buffer
	api.nvim_buf_set_option(buf, "modifiable", true)

	api.nvim_buf_set_lines(buf, 0, 1, false, {
		"  Interesting ACM Publications",
	})

	api.nvim_buf_set_lines(buf, 1, 2, false, {
		"  Requesting papers from ACM...",
	})

	-- Setup a http socket and request
	local command = string.format("wget -q -O - '%s'", url)

	-- Execute the wget command and capture its output
	local handle = io.popen(command)
	local response = ""
	if handle ~= nil then
		response = handle:read("*a")
		handle:close()
	else
		response = ""
	end

	-- extract the rss feed link
	local rss_url = response:match('"https://dl%.acm%.org/action/showFeed%?.-"')
	if rss_url == nil then
		api.nvim_buf_set_lines(buf, 3, 4, false, {
			"  ERROR: Could not locate Feed!",
		})
		return
	end
	rss_url = rss_url:sub(2, #rss_url - 1)

	api.nvim_buf_set_lines(buf, 3, 4, false, {
		"  Feed found at: " .. rss_url,
	})

	local rss_content = httprequest(rss_url)
	api.nvim_buf_set_lines(buf, 4, 5, false, {
		"  Received feed content",
	})

	-- skip initial block
	local b, b_start = rss_content:find("</image>", 1, false)

	-- select titles from response
	b = b_start
	local titles = {}
	while true do
		local x, y = rss_content:find("<title>.-</title>", b, false)

		-- stop if no further occurrences are found
		if x == nil or y == nil then
			break
		end

		-- save substring to titles
		table.insert(titles, rss_content:sub(x + 7, y - 8))
		b = y
	end

	-- select links from rss_content
	b = b_start
	local links = {}
	while true do
		local x, y = rss_content:find("<link>.-</link>", b, false)

		-- stop if no further occurrences are found
		if x == nil or y == nil then
			break
		end

		-- save substring to links
		table.insert(links, rss_content:sub(x + 6, y - 7))
		b = y
	end

	-- select dates from rss_content
	b = b_start
	local dates = {}
	while true do
		local x, y = rss_content:find("<dc:date>.-</dc:date>", b, false)

		-- stop if no further occurrences are found
		if x == nil or y == nil then
			break
		end

		-- save substring to dates
		table.insert(dates, rss_content:sub(x + 9, y - 10))
		b = y
	end

	api.nvim_buf_set_lines(buf, 1, -1, false, {
		"  Found entries: " .. #dates,
	})

	local current_line = 4
	for x = 1, #dates do
		api.nvim_buf_set_lines(buf, current_line, -1, false, { "  Title:   " .. titles[x] })
		current_line = current_line + 1
		api.nvim_buf_set_lines(buf, current_line, -1, false, { "  Date:    " .. dates[x] })
		current_line = current_line + 1
		api.nvim_buf_set_lines(buf, current_line, -1, false, { "  Website: " .. links[x] })
		current_line = current_line + 1
		api.nvim_buf_set_lines(buf, current_line, -1, false, { "" })
		current_line = current_line + 2
	end
	api.nvim_buf_set_lines(buf, current_line, -1, false, { "End of feed entries." })

	-- disable write / make buffer readonly
	api.nvim_buf_set_option(buf, "modifiable", false)
end

return M