add inter-process communication (ipc) plugin (#127)

* adds single instance support and basic file dragging from instance to instance

2 files changed, 1027 insertions, 0 deletions

diff --git a/README.md b/README.md
index 50c49b1..ab84be5 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,7 @@ _Note: if you make a pull request, the table should be updated and kept in alpha
 | [`immersive-title`](https://github.com/takase1121/lite-xl-immersive-title)\*                                   | Dark (or even Mica!) title bar for Lite XL                                                                                                                                                                                                                                                       |
 | [`indent_convert`](plugins/indent_convert.lua?raw=1)                                                           | Convert between tabs and spaces indentation                                                                                                                                                                                                                                                      |
 | [`indentguide`](plugins/indentguide.lua?raw=1)                                                                 | Adds indent guides _([screenshot](https://user-images.githubusercontent.com/3920290/79640716-f9860000-818a-11ea-9c3b-26d10dd0e0c0.png))_                                                                                                                                                         |
+| [`ipc`](plugins/ipc.lua?raw=1)                                                                                 | Adds inter-process communication support                                                                                                                                                                                                                                                         |
 | [`Kinc Projects`](https://github.com/Kode-Community/kinc_plugin)\*                                             | Adds [Kinc](https://github.com/Kode/Kinc) Project generation with basic build commands(depends on [`console`](https://github.com/franko/console))                                                                                                                                                |
 | [`language_angelscript`](plugins/language_angelscript.lua?raw=1)                                               | Syntax for the [Angelscript](https://www.angelcode.com/angelscript/) programming language                                                                                                                                                                                                        |
 | [`language_assembly_x86`](plugins/language_assembly_x86.lua?raw=1)                                             | Syntax for Intel x86 assembly                                                                                                                                                                                                                                                                    |
diff --git a/plugins/ipc.lua b/plugins/ipc.lua
new file mode 100644
index 0000000..128e39c
--- /dev/null
+++ b/plugins/ipc.lua
@@ -0,0 +1,1026 @@
+-- mod-version:3
+--
+-- Crossplatform file based IPC system for lite-xl.
+-- @copyright Jefferson Gonzalez <jgmdev@gmail.com>
+-- @license MIT
+--
+local core = require "core"
+local config = require "core.config"
+local common = require "core.common"
+local command = require "core.command"
+local Object = require "core.object"
+local RootView = require "core.rootview"
+local settings_found, settings = pcall(require, "plugins.settings")
+
+---The maximum amount of seconds a message will be broadcasted.
+---@type integer
+local MESSAGE_EXPIRATION=3
+
+---@class config.plugins.ipc
+---@field single_instance boolean
+---@field dirs_instance boolean
+config.plugins.ipc = common.merge({
+  single_instance = true,
+  dirs_instance = true,
+  -- The config specification used by the settings gui
+  config_spec = {
+    name = "Inter-process communication",
+    {
+      label = "Single Instance",
+      description = "Run a single instance of lite-xl.",
+      path = "single_instance",
+      type = "toggle",
+      default = true
+    },
+    {
+      label = "Directories Instance",
+      description = "Open a new instance for directories.",
+      path = "dirs_instance",
+      type = "toggle",
+      default = true
+    }
+  }
+}, config.plugins.ipc)
+
+---@alias plugins.ipc.onmessageread fun(message: plugins.ipc.message) | nil
+---@alias plugins.ipc.onreplyread fun(reply: plugins.ipc.reply) | nil
+---@alias plugins.ipc.onmessage fun(message: plugins.ipc.message, reply: plugins.ipc.reply) | nil
+---@alias plugins.ipc.onreply fun(reply: plugins.ipc.reply) | nil
+---@alias plugins.ipc.function fun(...)
+
+---@alias plugins.ipc.messagetype
+---| '"message"'
+---| '"method"'
+---| '"signal"'
+
+---@class plugins.ipc.message
+---@field id string
+---@field sender string
+---@field name string
+---@field type plugins.ipc.messagetype | string
+---@field destinations table<integer,string>
+---@field data table<string,any>
+---@field timestamp number
+---@field on_read plugins.ipc.onmessageread
+---@field on_reply plugins.ipc.onreply
+---@field replies plugins.ipc.reply[]
+local IPCMessage = {
+  ---Id of the message
+  id = "",
+  ---The id of process that sent the message
+  sender = "",
+  ---Name of the message
+  name = "",
+  ---Type of message.
+  type = "",
+  ---List with id of the instance that should receive the message.
+  destinations = {},
+  ---A list of named values sent to receivers.
+  data = {},
+  ---Time in seconds when the message was sent for automatic expiration purposes.
+  timestamp = 0,
+  ---Optional callback executed by the receiver when the message is read.
+  on_read = function(message) end,
+  ---Optional callback executed when a reply to the message is received.
+  on_reply = function(reply) end,
+  ---The received replies for the message.
+  replies = {}
+}
+
+---@class plugins.ipc.reply
+---@field id string
+---@field sender string
+---@field replier string
+---@field data table<string,any>
+---@field timestamp number
+---@field on_read plugins.ipc.onreplyread
+local IPCReply = {
+  ---Id of the message
+  id = "",
+  ---The id of process that sent the message
+  sender = "",
+  ---The id of the replier
+  replier = "",
+  ---A list of named values sent back to sender.
+  data = {},
+  ---Time in seconds when the reply was sent for automatic expiration purposes.
+  timestamp = 0,
+  ---Optional callback executed by the sender when the reply is read.
+  on_read = function(reply) end
+}
+
+---@class plugins.ipc.instance
+---@field id string
+---@field position integer
+---@field last_update integer
+---@field messages plugins.ipc.message[]
+---@field replies plugins.ipc.reply[]
+---@field properties table
+local IPCInstance = {
+  ---Process id of the instance.
+  id = "",
+  ---The position in which the instance was launched.
+  position = 0,
+  ---Flag that indicates if this instance was the first started.
+  primary = false,
+  ---Indicates the last time this instance updated its session file.
+  last_update = 0,
+  ---The messages been broadcasted.
+  messages = {},
+  ---The replies been broadcasted.
+  replies = {},
+  ---Table of properties associated with the instance.
+  properties = {}
+}
+
+---@class core.ipc : core.object
+---@field private id string
+---@field private user_dir string
+---@field private running boolean
+---@field private file string
+---@field private primary boolean
+---@field private position integer
+---@field private messages plugins.ipc.message[]
+---@field private replies plugins.ipc.reply[]
+---@field private listeners table<string,table<integer,plugins.ipc.onmessage>>
+---@field private signals table<string,integer>
+---@field private methods table<string,integer>
+---@field private signal_definitions table<integer,string>
+---@field private method_definitions table<integer,string>
+local IPC = Object:extend()
+
+---@class plugins.ipc.threads
+---@field cr thread
+---@field wake number
+
+---List of threads belonging to all instantiated IPC objects.
+---@type plugins.ipc.threads[]
+local threads = {}
+
+---Register a new thread to be run on the background.
+---@param f function
+local function add_thread(f)
+  local key = #threads + 1
+  threads[key] = { cr = coroutine.create(f), wake = 0 }
+  return key
+end
+
+---Updates the session file of an IPC object.
+---@param self core.ipc
+local function update_file(self)
+  local file, errmsg = io.open(self.file, "w+")
+
+  if file then
+    local output = "-- Warning: Generated by IPC system do not edit manually!\n"
+      .. "return " .. common.serialize(
+      {
+        id = self.id,
+        primary = self.primary,
+        position = self.position,
+        last_update = os.time(),
+        messages = self.messages,
+        replies = self.replies,
+        signals = self.signal_definitions,
+        methods = self.method_definitions
+      },
+      {
+        pretty = true
+      }
+    )
+
+    output = output:gsub("%s+%[\"on_reply\"%].-\n", "")
+
+    file:write(output)
+    file:close()
+  else
+    core.error("IPC Error: failed updating status (%s)", errmsg)
+  end
+end
+
+---Constructor
+---@param id? string Defaults to current lite-xl process id.
+function IPC:new(id)
+  self.id = id or tostring(system.get_process_id())
+  self.user_dir = USERDIR .. "/ipc"
+  self.file = self.user_dir .. "/" .. self.id .. ".lua"
+  self.primary = false
+  self.running = false
+  self.messages = {}
+  self.replies = {}
+  self.listeners = {}
+  self.signals = {}
+  self.methods = {}
+  self.signal_definitions = {}
+  self.method_definitions = {}
+
+  local ipc_dir_status = system.get_file_info(self.user_dir)
+
+  if not ipc_dir_status then
+    local created, errmsg = common.mkdirp(self.user_dir)
+    if not created then
+      core.error("Error initializing IPC system: %s", errmsg)
+      return
+    end
+  end
+
+  local file, errmsg = io.open(self.file, "w+")
+
+  if not file then
+    core.error("Error initializing IPC system: %s", errmsg)
+    return
+  else
+    file:close()
+    os.remove(self.file)
+  end
+
+  -- Execute to set the instance position and primary attribute if no other running.
+  local instances = self:get_instances()
+  self.primary = #instances == 0 and true or false
+  self.position = #instances + 1
+
+  self:start()
+end
+
+---Starts and registers the ipc session and monitoring.
+function IPC:start()
+  if not self.running then
+    self.running = true
+
+    update_file(self)
+
+    local wait_time = 0.3
+
+    local this = self
+    self.coroutine_key = add_thread(function()
+      coroutine.yield(wait_time)
+      while(true) do
+        this:read_messages()
+        this:read_replies()
+        update_file(this)
+        coroutine.yield(wait_time)
+      end
+    end)
+  end
+end
+
+---Stop and unregister the ipc session and monitoring.
+function IPC:stop()
+  self.running = false
+  table.remove(threads, self.coroutine_key)
+  os.remove(self.file)
+end
+
+---Get a list of running lite-xl instances.
+---@return plugins.ipc.instance[]
+function IPC:get_instances()
+  ---@type plugins.ipc.instance[]
+  local instances = {}
+
+  local files, errmsg = system.list_dir(self.user_dir)
+
+  if files then
+    for _, file in ipairs(files) do
+      if string.match(file, "^%d+%.lua$") then
+        local path = self.user_dir .. "/" .. file
+        local file_info = system.get_file_info(path)
+        if file_info and file_info.type == "file" then
+          ::read_instance_file::
+          ---@type plugins.ipc.instance
+          local instance = dofile(path)
+          if instance and instance.id ~= self.id then
+            if instance.last_update + 2 > os.time() then
+              table.insert(instances, instance)
+            else
+              -- Delete expired instance session maybe result of a crash
+              os.remove(path)
+            end
+          elseif not instance and path ~= self.file then
+            --We retry reading the file since it was been modified
+            --by its owner instance.
+            goto read_instance_file
+          end
+        end
+      end
+    end
+  else
+    core.error("IPC Error: failed getting running instances (%s)", errmsg)
+  end
+
+  local instances_count = #instances
+
+  if instances_count > 0 then
+    table.sort(instances, function(ia, ib)
+      return ia.position < ib.position
+    end)
+  end
+
+  if not self.primary and self.position then
+    if instances_count == 0 or instances[1].position > self.position then
+      self.primary = true
+    end
+  end
+
+  return instances
+end
+
+---@class plugins.ipc.vardecl
+---@field name string
+---@field type string
+---@field optional boolean
+
+---Generate a string representation of a function
+---@param name string
+---@param params? plugins.ipc.vardecl[]
+---@param returns? plugins.ipc.vardecl[]
+---@return string function_definition
+local function generate_definition(name, params, returns)
+  local declaration = name .. "("
+
+  if params and #params > 0 then
+    local params_string = ""
+    for _, param in ipairs(params) do
+      params_string = params_string .. param.name
+      if param.optional then
+        params_string = params_string .. "?: "
+      else
+        params_string = params_string .. ": "
+      end
+      params_string = params_string .. param.type .. ", "
+    end
+    local params_stripped = params_string:gsub(", $", "")
+    declaration = declaration .. params_stripped
+  end
+
+  declaration = declaration .. ")"
+
+  if returns and #returns > 0 then
+    declaration = declaration .. " -> "
+    local returns_string = ""
+    for _, ret in ipairs(returns) do
+      if ret.name then
+        returns_string = returns_string .. ret.name .. ": "
+      end
+      returns_string = returns_string .. ret.type
+      if ret.optional then
+        returns_string = returns_string .. "?, "
+      else
+        returns_string = returns_string .. ", "
+      end
+    end
+    local returns_stripped = returns_string:gsub(", $", "")
+    declaration = declaration .. returns_stripped
+  end
+
+  return declaration
+end
+
+---Retrieve the id of the primary instance if found.
+---@return string | nil
+function IPC:get_primary_instance()
+  local instances = self:get_instances()
+  for _, instance in ipairs(instances) do
+    if instance.primary then
+      return instance.id
+    end
+  end
+  return nil
+end
+
+---Get a queued message.
+---@param message_id string
+---@return plugins.ipc.message | nil
+function IPC:get_message(message_id)
+  for _, message in ipairs(self.messages) do
+    if message.id == message_id then
+      return message
+    end
+  end
+  return nil
+end
+
+---Remove a message from the queue.
+---@param message_id string
+function IPC:remove_message(message_id)
+  for m, message in ipairs(self.messages) do
+    if message.id == message_id then
+      table.remove(self.messages, m)
+      break
+    end
+  end
+end
+
+---Get the reply sent to a specific message.
+---@param message_id string
+---@return plugins.ipc.reply | nil
+function IPC:get_reply(message_id)
+  for _, reply in ipairs(self.replies) do
+    if reply.id == message_id then
+      return reply
+    end
+  end
+  return nil
+end
+
+---Verify all the messages sent by running instances, read those directed
+---to the currently running instance and reply to them.
+function IPC:read_messages()
+  local instances = self:get_instances()
+
+  local awaiting_replies = {}
+
+  for _, instance in ipairs(instances) do
+    for _, message in ipairs(instance.messages) do
+      for _, destination in ipairs(message.destinations) do
+        if destination == self.id then
+          local reply = self:get_reply(message.id)
+
+          if not reply then
+            if message.on_read then
+              local on_read, errmsg = load(message.on_read)
+              if on_read then
+                local executed = core.try(function() on_read(message) end)
+                if not executed then
+                  core.error(
+                    "IPC Error: could not run message on_read\n"
+                      .. "Message: %s\n",
+                    common.serialize(message, {pretty = true})
+                  )
+                end
+              else
+                core.error(
+                  "IPC Error: could not run message on_read (%s)\n"
+                    .. "Message: %s\n",
+                  errmsg,
+                  common.serialize(message, {pretty = true})
+                )
+              end
+            end
+
+            ---@type plugins.ipc.reply
+            reply = {}
+            reply.id = message.id
+            reply.sender = message.sender
+            reply.replier = self.id
+            reply.data = {}
+            reply.on_read = nil
+
+            local type_name = message.type .. "." .. message.name
+
+            -- Allow listeners to react to message and modify reply
+            if self.listeners[type_name] and #self.listeners[type_name] > 0 then
+              for _, on_message in ipairs(self.listeners[type_name]) do
+                on_message(message, reply)
+              end
+            end
+
+            if reply.on_read then
+              reply.on_read = string.dump(reply.on_read)
+            end
+
+            reply.timestamp = os.time()
+          end
+
+          table.insert(awaiting_replies, reply)
+          break
+        end
+      end
+    end
+  end
+
+  self.replies = awaiting_replies
+end
+
+---Reads replies directed to messages sent by the currently running instance
+---and if any returns them.
+---@return plugins.ipc.reply[] | nil
+function IPC:read_replies()
+  if #self.messages == 0 then
+    return
+  end
+
+  local instances = self:get_instances()
+
+  local replies = {}
+
+  local messages_removed = 0;
+  for m=1, #self.messages do
+    local message = self.messages[m-messages_removed]
+    local message_removed = false
+
+    local destinations_removed = 0
+    for d=1, #message.destinations do
+      local destination = message.destinations[d-destinations_removed]
+
+      local found = false
+      for _, instance in ipairs(instances) do
+        if instance.id == destination then
+          found = true
+          for _, reply in ipairs(instance.replies) do
+            if reply.id == message.id then
+              local reply_registered = false
+              for _, message_reply in ipairs(message.replies) do
+                if message_reply.replier == instance.id then
+                  reply_registered = true
+                  break
+                end
+              end
+              if not reply_registered then
+                if message.on_reply then
+                  message.on_reply(reply)
+                end
+
+                if reply.on_read then
+                  local on_read, errmsg = load(reply.on_read)
+                  if on_read then
+                    local executed = core.try(function() on_read(reply) end)
+                    if not executed then
+                      core.error(
+                        "IPC Error: could not run reply on_read\n"
+                          .. "Message: %s\n"
+                          .. "Reply: %s",
+                        common.serialize(message, {pretty = true}),
+                        common.serialize(reply, {pretty = true})
+                      )
+                    end
+                  else
+                    core.error(
+                      "IPC Error: could not run reply on_read (%s)\n"
+                        .. "Message: %s\n"
+                        .. "Reply: %s",
+                      errmsg,
+                      common.serialize(message, {pretty = true}),
+                      common.serialize(reply, {pretty = true})
+                    )
+                  end
+                end
+
+                table.insert(replies, reply)
+                table.insert(message.replies, reply)
+              end
+            end
+          end
+          break
+        end
+      end
+      if not found then
+        table.remove(message.destinations, d-destinations_removed)
+        destinations_removed = destinations_removed + 1
+        if #message.destinations == 0 then
+          table.remove(self.messages, m-messages_removed)
+          messages_removed = messages_removed + 1
+          message_removed = true
+        end
+      end
+    end
+    if
+      not message_removed
+      and
+      (
+        #message.replies == #message.destinations
+        or
+        message.timestamp + MESSAGE_EXPIRATION < os.time()
+      )
+    then
+      table.remove(self.messages, m-messages_removed)
+      messages_removed = messages_removed + 1
+    end
+  end
+
+  return replies
+end
+
+---Blocks execution of current instance to wait for all replies by the
+---specified message and when finished returns them.
+---@param message_id string
+---@return plugins.ipc.reply[] | nil
+function IPC:wait_for_replies(message_id)
+  local message_data = self:get_message(message_id)
+
+  update_file(self)
+
+  if message_data then
+    self:read_replies()
+    while true do
+      if
+        message_data.replies
+        and
+        #message_data.replies == #message_data.destinations
+      then
+        return message_data.replies
+      elseif not self:get_message(message_id) then
+        return message_data.replies
+      end
+      self:read_replies()
+    end
+  end
+  return nil
+end
+
+---Blocks execution of current instance to wait for all messages to
+---be replied to.
+function IPC:wait_for_messages()
+  update_file(self)
+  while #self.messages > 0 do
+    self:read_replies()
+    system.sleep(0.1)
+  end
+end
+
+---@class plugins.ipc.sendmessageoptions
+---@field data table<string,any> @Optional data given to the receiver.
+---@field on_reply plugins.ipc.onreply @Callback that allows monitoring all the replies received for this message.
+---@field on_read plugins.ipc.onmessage @Function executed by the message receiver.
+---@field destinations string | table<integer,string> | nil @Id of the running instances to receive the message, if not set all running instances will receive the message.
+
+---Queue a new message to be sent to other lite-xl instances.
+---@param name string
+---@param options? plugins.ipc.sendmessageoptions
+---@param message_type? plugins.ipc.messagetype
+---@return string | nil message_id
+function IPC:send_message(name, options, message_type)
+  options = options or {}
+
+  local found_destinations = {}
+  local instances = self:get_instances()
+  local destinations = options.destinations
+
+  if type(destinations) == "string" then
+    destinations = { destinations }
+  end
+
+  if not destinations then
+    for _, instance in ipairs(instances) do
+      table.insert(found_destinations, instance.id)
+    end
+  else
+      for _, destination in ipairs(destinations) do
+        for _, instance in ipairs(instances) do
+          if instance.id == destination then
+            table.insert(found_destinations, destination)
+          end
+        end
+      end
+  end
+
+  if #found_destinations <= 0 then
+    return nil
+  end
+
+  ---@type plugins.ipc.message
+  local message = {}
+  message.id = self.id .. "." .. tostring(system.get_time())
+  message.name = name
+  message.type = message_type or "message"
+  message.sender = self.id
+  message.data = options.data or {}
+  message.destinations = found_destinations
+  message.timestamp = os.time()
+  message.on_reply = options.on_reply or nil
+  message.on_read = options.on_read and string.dump(options.on_read) or nil
+  message.replies = {}
+
+  table.insert(self.messages, message)
+
+  update_file(self)
+
+  return message.id
+end
+
+---Add a listener for a given type of message.
+---@param name string
+---@param callback plugins.ipc.onmessage
+---@param message_type? plugins.ipc.messagetype
+---@return integer listener_position
+function IPC:listen_message(name, callback, message_type)
+  message_type = message_type or "message"
+
+  local type_name = message_type .. "." .. name
+  if not self.listeners[type_name] then
+    self.listeners[type_name] = {}
+  end
+
+  table.insert(self.listeners[type_name], callback)
+
+  return #self.listeners[type_name]
+end
+
+---Listen for a given signal.
+---@param name string
+---@param callback plugins.ipc.function
+---@return integer listener_position
+function IPC:listen_signal(name, callback)
+  local signal_cb = function(message)
+    callback(table.unpack(message.data))
+  end
+  return self:listen_message(name, signal_cb, "signal")
+end
+
+---Add a new signal that can be sent to other instances.
+---@param name string A unique name for the signal.
+---@param params? plugins.ipc.vardecl[] Parameters that are going to be passed into callback.
+function IPC:register_signal(name, params)
+  if self.signals[name] then
+    core.log_quiet("IPC: Overriding signal '%s'", name)
+    table.remove(self.signal_definitions, self.signals[name])
+  end
+
+  self.signals[name] = table.insert(
+    self.signal_definitions,
+    generate_definition(name, params)
+  )
+
+  table.sort(self.signal_definitions)
+end
+
+---Add a new method that can be invoked from other instances.
+---@param name string A unique name for the method.
+---@param method fun(...) Function invoked when the method is called.
+---@param params? plugins.ipc.vardecl[] Parameters that are going to be passed into method.
+---@param returns? plugins.ipc.vardecl[] Return values of the method.
+function IPC:register_method(name, method, params, returns)
+  if self.methods[name] then
+    core.log_quiet("IPC: Overriding method '%s'", name)
+    table.remove(self.method_definitions, self.methods[name])
+  end
+
+  self.methods[name] = table.insert(
+    self.method_definitions,
+    generate_definition(name, params, returns)
+  )
+
+  table.sort(self.method_definitions)
+
+  self:listen_message(name, function(message, reply)
+    local ret = table.pack(method(table.unpack(message.data)))
+    reply.data = ret
+  end, "method")
+end
+
+---Broadcast a signal to running instances.
+---@param destinations string | table<integer, string> | nil
+---@param name string
+---@vararg any signal_parameters
+function IPC:signal(destinations, name, ...)
+  self:send_message(name, {
+    destinations = destinations,
+    data = table.pack(self.id, ...)
+  }, "signal")
+end
+
+---Call a method on another instance and wait for reply.
+---@param destinations string | table<integer, string> | nil
+---@param name string
+---@return any | table<string,table> return_of_called_method
+function IPC:call(destinations, name, ...)
+  local message_id = self:send_message(name, {
+    destinations = destinations,
+    data = table.pack(...)
+  }, "method")
+
+  local ret = nil
+
+  if message_id then
+    local replies = self:wait_for_replies(message_id)
+    if replies and #replies > 1 then
+      ret = {}
+      for _, reply in ipairs(replies) do
+        ret[reply.replier] = reply.data
+      end
+    elseif replies and #replies > 0 then
+      return table.unpack(replies[1].data)
+    end
+  else
+    core.error("IPC Error: could not make call to '%s'", name)
+  end
+
+  return ret
+end
+
+---Call a method on another instance asynchronously waiting for the replies.
+---@param destinations string | table<integer, string> | nil
+---@param name string
+---@param callback fun(id: string, ret: table) | nil Called with the returned values
+---@return string | nil message_id
+function IPC:call_async(destinations, name, callback, ...)
+  return self:send_message(name, {
+    destinations = destinations,
+    data = table.pack(...),
+    on_reply = callback and function(reply)
+      callback(reply.replier, reply.data)
+    end or nil
+  }, "method")
+end
+
+---Main ipc session for current instance.
+---@type core.ipc
+local ipc = IPC()
+
+---Get the IPC session for the running lite-xl instance.
+---@return core.ipc
+function IPC.current()
+  return ipc
+end
+
+--------------------------------------------------------------------------------
+-- Override system.wait_event to allow ipc monitoring on the background.
+--------------------------------------------------------------------------------
+local system_wait_event = system.wait_event
+
+local run_threads = coroutine.wrap(function()
+  while true do
+    for k, thread in pairs(threads) do
+      if thread.wake < system.get_time() then
+        local _, wait = assert(coroutine.resume(thread.cr))
+        if coroutine.status(thread.cr) == "dead" then
+          table.remove(threads, k)
+        elseif wait then
+          thread.wake = system.get_time() + wait
+        end
+      end
+      coroutine.yield()
+    end
+  end
+end)
+
+system.wait_event = function(timeout)
+  run_threads()
+
+  if not timeout then
+    if not system.window_has_focus() then
+      local t = system.get_time()
+      local h = 0.5 / 2
+      local dt = math.ceil(t / h) * h - t
+
+      system_wait_event(dt + 1 / config.fps)
+    else
+      system_wait_event()
+    end
+  else
+    system_wait_event(timeout)
+  end
+end
+
+--------------------------------------------------------------------------------
+-- Override system.show_fatal_error to be able and destroy session file on crash.
+--------------------------------------------------------------------------------
+local system_show_fatal_error = system.show_fatal_error
+
+system.show_fatal_error = function(title, message)
+  if title == "Lite XL internal error" then
+    ipc:stop()
+  end
+  system_show_fatal_error(title, message)
+end
+
+--------------------------------------------------------------------------------
+-- Override core.run to destroy ipc session file on exit.
+--------------------------------------------------------------------------------
+local core_run = core.run
+
+core.run = function()
+  core_run()
+  ipc:stop()
+end
+
+--------------------------------------------------------------------------------
+-- Override system.get_time temporarily as first function called on core.run
+-- to allow settings gui to properly load ipc config options.
+--------------------------------------------------------------------------------
+local system_get_time = system.get_time
+
+system.get_time = function()
+  if settings_found and not settings.ui then
+    return system_get_time()
+  end
+
+  if config.plugins.ipc.single_instance then
+    system.get_time = system_get_time
+
+    local primary_instance = ipc:get_primary_instance()
+    if primary_instance and ARGS[2] then
+      local open_directory = false
+      for i=2, #ARGS do
+        local path = system.absolute_path(ARGS[i])
+
+        if path then
+          local path_info = system.get_file_info(path)
+          if path_info then
+            if path_info.type == "file" then
+              ipc:call_async(primary_instance, "core.open_file", nil, path)
+            else
+              if not config.plugins.ipc.dirs_instance then
+                ipc:call_async(primary_instance, "core.open_directory", nil, path)
+              else
+                if #ARGS > 2 then
+                  system.exec(string.format("%q %q", EXEFILE, path))
+                else
+                  open_directory = true
+                end
+              end
+            end
+          end
+        end
+      end
+      ipc:wait_for_messages()
+      if not open_directory then
+        os.exit()
+      end
+    end
+  else
+    system.get_time = system_get_time
+  end
+
+  return system_get_time()
+end
+
+--------------------------------------------------------------------------------
+-- Register methods for opening files and directories.
+--------------------------------------------------------------------------------
+ipc:register_method("core.open_file", function(file)
+  if system.get_file_info(file) then
+    if system.raise_window then system.raise_window() end
+    core.root_view:open_doc(core.open_doc(file))
+  end
+end, {{name = "file", type = "string"}})
+
+ipc:register_method("core.open_directory", function(directory)
+  if system.get_file_info(directory) then
+    if system.raise_window then system.raise_window() end
+    core.add_project_directory(directory)
+  end
+end, {{name = "directory", type = "string"}})
+
+--------------------------------------------------------------------------------
+-- Register file dragging signals from instance to instance
+--------------------------------------------------------------------------------
+ipc:register_signal("core.tab_drag_start", {{name = "file", type = "string"}})
+ipc:register_signal("core.tab_drag_stop")
+ipc:register_signal("core.tab_drag_received", {{name = "file", type = "string"}})
+
+local rootview_tab_dragging = false
+local rootview_dragged_node = nil
+local rootview_waiting_drop_file = ""
+local rootview_waiting_drop_instance = ""
+
+local rootview_on_mouse_moved = RootView.on_mouse_moved
+function RootView:on_mouse_moved(x, y, dx, dy)
+  rootview_on_mouse_moved(self, x, y, dx, dy)
+  if
+    self.dragged_node and self.dragged_node.dragging
+    and
+    not rootview_tab_dragging
+  then
+    ---@type core.doc
+    local doc = core.active_view.doc
+    if doc and doc.abs_filename then
+      rootview_tab_dragging = true
+      ipc:signal(nil, "core.tab_drag_start", doc.abs_filename)
+      rootview_dragged_node = self.dragged_node
+    end
+  elseif rootview_dragged_node then
+    local w, h, wx, wy = system.get_window_size()
+    if x < 0 or x > w or y < 0 or y > h then
+      self.dragged_node = nil
+      self:set_show_overlay(self.drag_overlay, false)
+    elseif not self.dragged_node then
+      self.dragged_node = rootview_dragged_node
+      self:set_show_overlay(self.drag_overlay, true)
+    end
+    core.request_cursor("hand")
+  elseif rootview_waiting_drop_file ~= "" then
+    ipc:signal(
+      rootview_waiting_drop_instance,
+      "core.tab_drag_received",
+      rootview_waiting_drop_file
+    )
+    core.root_view:open_doc(core.open_doc(rootview_waiting_drop_file))
+    rootview_waiting_drop_file = ""
+  end
+end
+
+local rootview_on_mouse_released = RootView.on_mouse_released
+function RootView:on_mouse_released(button, x, y, ...)
+  rootview_on_mouse_released(self, button, x, y, ...)
+  if rootview_tab_dragging then
+    rootview_tab_dragging = false
+    rootview_dragged_node = nil
+    ipc:signal(nil, "core.tab_drag_stop")
+  end
+end
+
+ipc:listen_signal("core.tab_drag_start", function(instance, file)
+  rootview_waiting_drop_instance = instance
+  rootview_waiting_drop_file = file
+end)
+
+ipc:listen_signal("core.tab_drag_stop", function()
+  rootview_waiting_drop_instance = ""
+  rootview_waiting_drop_file = ""
+end)
+
+ipc:listen_signal("core.tab_drag_received", function()
+  command.perform("root:close")
+end)
+
+
+return IPC