local M = {}

local stats = require("luacov.stats")
local data = stats.load()
local statsfile = stats.start()
M.statsfile = statsfile

local tick = package.loaded["luacov.tick"]
local ctr = 0
local luacovlock = os.tmpname()

local booting = true
local skip = {}
M.skip = skip

local function on_line(_, line_nr)
   if tick then
      ctr = ctr + 1
      if ctr == 100 then
         ctr = 0
         stats.save(data, statsfile)
      end
   end

   -- get name of processed file; ignore Lua code loaded from raw strings
   local name = debug.getinfo(2, "S").source
   if not name:match("^@") then
      return
   end
   name = name:sub(2)

   -- skip 'luacov.lua' in coverage report
   if booting then
      skip[name] = true
      booting = false
   end

   if skip[name] then
      return
   end

   local file = data[name]
   if not file then
      file = {max=0}
      data[name] = file
   end
   if line_nr > file.max then
      file.max = line_nr
   end
   file[line_nr] = (file[line_nr] or 0) + 1
end

local function on_exit()
   os.remove(luacovlock)
   stats.save(data, statsfile)
   stats.stop(statsfile)
end

local function init()
   if not tick then
      M.on_exit_trick = io.open(luacovlock, "w")
      debug.setmetatable(M.on_exit_trick, { __gc = on_exit } )
   end

   debug.sethook(on_line, "l")

   local rawcoroutinecreate = coroutine.create
   coroutine.create = function(...)
      local co = rawcoroutinecreate(...)
      debug.sethook(co, on_line, "l")
      return co
   end
   coroutine.wrap = function(...)
      local co = rawcoroutinecreate(...)
      debug.sethook(co, on_line, "l")
      return function()
         local r = { coroutine.resume(co) }
         if not r[1] then
            error(r[2])
         end
         return unpack(r, 2)
      end
   end

   local rawexit = os.exit
   os.exit = function(...)
      on_exit()
      rawexit(...)
   end
end

init()

return M