local M = {}


local INTERVAL_MS = 10 * 1000
local SILENT = true


-- Because a timer cannot be converted to Vim value,
-- store indice of timers instead of timer instances.
local timers = {}


local function handler()
   if not vim.bo.modified then
      return
   end
   if vim.bo.readonly then
      return
   end
   if vim.bo.buftype ~= '' then
      return
   end
   if vim.fn.bufname() == '' then
      return
   end

   if not SILENT then
      vim.cmd([[echohl Comment]])
      vim.cmd([[echo 'Auto-saving...']])
      vim.cmd([[echohl None]])
   end

   vim.cmd([[silent! write]])

   if not SILENT then
      vim.cmd([[echohl Comment]])
      vim.cmd([[echo 'Saved.']])
      vim.cmd([[echohl None]])
   end
end


function M.enable()
   if vim.b.autosave_timer_id then
      return
   end

   local timer = vim.loop.new_timer()
   timer:start(INTERVAL_MS, INTERVAL_MS, vim.schedule_wrap(handler))
   local tid = #timers + 1
   timers[tid] = timer
   vim.b.autosave_timer_id = tid
end


function M.disable()
   if not vim.b.autosave_timer_id then
      return
   end

   local tid = vim.b.autosave_timer_id
   vim.b.autosave_timer_id = nil
   if not timers[tid] then
      return
   end
   timers[tid]:close()
   timers[tid] = nil
end


function M.toggle()
   if vim.b.autosave_timer_id then
      M.disable()
   else
      M.enable()
   end
end


return M