local M = {
	moduleNames = { "init.lua", "__init__.py" },
	separatorC = "|",
	modifiedC = "+",
}

M.title = function(bufnr, isSelected)
	local file = vim.fn.simplify(vim.fn.bufname(bufnr))
	local tail = vim.fn.fnamemodify(file, ':t')
	local buftype = vim.fn.getbufvar(bufnr, '&buftype')
	local filetype = vim.fn.getbufvar(bufnr, '&filetype')

	if buftype == "help" then
		return "help:" .. vim.fn.fnamemodify(tail, ':r')
	elseif filetype == "netrw" then
		return file == "" and "netrw" or vim.fn.fnamemodify(file, ':p:~')
	elseif buftype ~= "" then
		return buftype
	elseif file == "" then
		return filetype == "" and "[No Name]" or filetype
	elseif vim.tbl_contains(M.moduleNames, tail) then
		return vim.fn.fnamemodify(vim.fn.fnamemodify(file, ':p:~:h'), ':t') .. "/" .. tail -- e.g. minitab/init.lua
	end

	return tail
end

M.modified = function(bufnr)
	return vim.fn.getbufvar(bufnr, '&modified') == 1 and M.modifiedC or ""
end

M.windowCount = function(index, hl)
	local nwins = #vim.tbl_filter(function(winnr)
		return vim.fn.win_gettype(winnr) == ""  -- windows will appear or disappear at random when editing files etc for no discernible reason
	end, vim.api.nvim_tabpage_list_wins(index))
	return nwins > 1 and '%#TabLineSel#' .. nwins .. hl or ""
end

M.separator = function(index, hl)
	return (index < vim.fn.tabpagenr('$') and '%#TabLine#' .. M.separatorC or "")
end

M.cell = function(index)
	local isSelected = vim.fn.tabpagenr() == index
	local buflist = vim.fn.tabpagebuflist(index)
	local winnr = vim.fn.tabpagewinnr(index)
	local bufnr = buflist[winnr]
	local hl = (isSelected and '%#TabLineSel#' or '%#TabLine#')

	local prefix = M.windowCount(index, hl) .. M.modified(bufnr) .. " "
	return hl .. '%' .. index .. 'T' .. " " ..
		(prefix == " " and "" or prefix) ..
		M.title(bufnr, isSelected) .. " " ..
		M.separator(index)
end

M.tabline = function()
	local line = ""
	for i = 1, vim.fn.tabpagenr('$'), 1 do
		line = line .. M.cell(i)
	end
	line = line .. '%#TabLineFill#%='
	if vim.fn.tabpagenr("$") > 1 then
		line = line .. '%#TabLine#%999XX'
	end
	return line
end

local setup = function(opts)
	if opts then
		for key, value in pairs(opts) do
			M[key] = value
		end
	end

	vim.opt.tabline = "%!v:lua.require'minitab'.helpers.tabline()"
end

return {
	helpers = M,
	setup = setup,
}