--
-- Session plugin
--

local session_dir = vim.fn.stdpath("state") .. "/sessions"
local session_default = session_dir .. "/default.vim"
if not vim.uv.fs_stat(session_dir) then
	vim.uv.fs_mkdir(session_dir, tonumber("755", 8))
	vim.notify("Sessions save directory created at " .. session_dir)
end

-- :mksession doesn't persist tab-local vars (t:tabname), so we write tab names to a sidecar
-- JSON file alongside the .vim session. Names are stored positionally because :mksession
-- recreates tabs in their original order, making the index stable across reloads.
local function tabnames_path(path)
	return (path:gsub("%.vim$", "")) .. ".tabnames.json"
end

local function save_session(path)
	vim.cmd.mksession({ path, bang = true })
	local names = {}
	for i, tp in ipairs(vim.api.nvim_list_tabpages()) do
		-- pcall: nvim_tabpage_get_var errors when the variable isn't set on that tab
		local ok, name = pcall(vim.api.nvim_tabpage_get_var, tp, "tabname")
		names[i] = (ok and type(name) == "string") and name or ""
	end
	local f = io.open(tabnames_path(path), "w")
	if f then
		f:write(vim.json.encode(names))
		f:close()
	end
end

local function load_session(path)
	vim.cmd.source(path)
	local f = io.open(tabnames_path(path), "r")
	if not f then
		return
	end
	local names = vim.json.decode(f:read("*a"))
	f:close()
	for i, tp in ipairs(vim.api.nvim_list_tabpages()) do
		if names[i] and names[i] ~= "" then
			vim.api.nvim_tabpage_set_var(tp, "tabname", names[i])
		end
	end
	vim.cmd.redrawtabline()
end

local function reload_session(path)
	save_session(path)
	vim.cmd.restart({ args = { "+qall", "SessionLoad", path } })
end

local function delete_session(path)
	vim.fs.rm(path)
	local sidecar = tabnames_path(path)
	if vim.uv.fs_stat(sidecar) then
		vim.fs.rm(sidecar)
	end
end

local function session_completefunc(arg_lead, _, _)
	local completions = {}
	for path in vim.fs.dir(session_dir) do
		if string.match(path, "^" .. arg_lead) and string.match(path, ".vim$") then
			completions[#completions + 1] = path:sub(1, -5)
		end
	end
	return completions
end

local function session_op(base, op)
	local path = #base > 0 and base or session_default
	if not string.match(path, "^" .. session_dir) then
		path = session_dir .. "/" .. path
	end
	if not string.match(path, "%.vim$") then
		path = path .. ".vim"
	end
	op(path)
end

vim.api.nvim_create_user_command("SessionSave", function(ev)
	session_op(ev.args, save_session)
end, { desc = "Save session", nargs = "?", complete = session_completefunc })
vim.api.nvim_create_user_command("SessionLoad", function(ev)
	session_op(ev.args, load_session)
end, { desc = "Load session", nargs = "?", complete = session_completefunc })
vim.api.nvim_create_user_command("SessionDelete", function(ev)
	session_op(ev.args, delete_session)
end, { desc = "Delete session", nargs = "?", complete = session_completefunc })
vim.api.nvim_create_user_command("SessionRestart", function(ev)
	session_op(ev.args, reload_session)
end, { desc = "Reload session", nargs = "?", complete = session_completefunc })
vim.api.nvim_create_user_command("SessionExitSave", function(ev)
	session_op(ev.args, save_session)
	vim.cmd.qall()
end, { desc = "Save session and exit", nargs = "?", complete = session_completefunc })
vim.api.nvim_create_user_command("SessionExitNoSave", function()
	vim.cmd.qall()
end, { desc = "Exit without saving session", nargs = "?", complete = session_completefunc })