local core = require "core"
local process = require "process"

-- tiny helpers
local function join(a, b) return (a:sub(-1) == "/" and a or (a .. "/")) .. b end

---@class mdb
local mdb = {
  proc = nil, ---@type process|nil
  state = 'idle',
}

---@meta
function mdb.log(msg) end
---@meta
function mdb.error(msg) end
---@meta
function mdb.on_connected() end
---@meta
function mdb.on_pause(file, line) end

function mdb:new(o)
  o = o or {}
  setmetatable(o, self)
  self.__index = self
  return o
end

function mdb:set_state(newstate)
  self.state = newstate
end

function mdb:parse_line(line)
  self.log('mdb> '..line)
  local words = {}
  for w in line:gmatch("%w+") do table.insert(words, w) end

  if words[1] == 'Paused' then
    -- Breakpoint hit
    if #words ~= 7 then return end
    local file = words[4]
    local linenr = tonumber(words[7])
    self:set_state("paused")
    core.add_thread(function() self.on_pause(file, linenr) end)
  elseif words[1] == "Type" then
    -- mobdebug started
    self:set_state("paused")
    core.add_thread(function() self.on_connected() end)
  end
end

function mdb:spawn(lua, root)
  local vendor_glob = join(root, "vendor/?.lua")

  local cmd = {}
   if type(lua) == "table" then
    for i=1, #lua do table.insert(cmd, lua[i]) end
  else
    table.insert(cmd, lua)
  end
  table.insert(cmd, "-e")
  table.insert(cmd, string.format([[
    package.path = %q .. ";" .. package.path
    require("mobdebug").listen()
  ]], vendor_glob))

  self:set_state('spawning')

  local proc = process.start(cmd, {
    stdout = process.REDIRECT_PIPE,
    stderr = process.REDIRECT_PIPE,
  })
  self.proc = proc

  self:set_state('connecting')

  core.add_thread(function()
      while true do
        core.redraw = true
        coroutine.yield(0.016) -- 60FPS
        local sout = self.proc:read_stdout()
        local serr = self.proc:read_stderr()
        if sout == nil and serr == nil then
          -- mdb exited
          break
        end
        if sout and sout~="" then
          for l in string.gmatch(sout, "([^\n]+)") do
            self:parse_line(l)
          end
        end
      end
  end)
end

function mdb:cmd(c)
  -- commands are only possible when mdb is paused
  if self.state == "paused" then
    self.log('>>>'..c)
    self.proc:write(c..'\n')
  else
    self.error('mdb not paused')
  end
end

function mdb:run()
  self:cmd("run")
end

function mdb:setb(file, line)
  self:cmd(string.format("setb %s %d", file, line))
end

function mdb:kill()
  self.proc:kill()
  self.proc:kill()
end

return mdb