diff --git a/lua/dante/callbacks.lua b/lua/dante/callbacks.lua
new file mode 100644
index 0000000..114c0ba
--- /dev/null
+++ b/lua/dante/callbacks.lua
@@ -0,0 +1,63 @@
+local M = {}
+
+---Callback function to handle the completion of a chat request.
+---@param res table
+---@param opts Options
+---@return function
+M.on_chat_completion = function(res, opts)
+  return function(obj)
+    local finish_reason = obj.choices[1].finish_reason
+    local content = obj.choices[1].message.content
+    if finish_reason == "stop" then
+      local lines = vim.split(content, "\n", { plain = true, trimempty = false })
+      vim.api.nvim_buf_set_lines(res.buf, -2, -1, true, lines)
+      if opts.verbose and obj.usage then
+        vim.notify("usage = " .. vim.inspect(obj.usage), vim.log.levels.INFO)
+      end
+      vim.notify("Done.", vim.log.levels.INFO)
+    else
+      vim.notify("An error occured during text genereation.", vim.log.levels.ERROR)
+    end
+  end
+end
+
+---Callback function to handle the completion chunk of a chat request.
+---@param res table
+---@param opts Options
+---@return function
+M.on_chat_completion_chunk = function(res, opts)
+  return function(obj)
+    local finish_reason = obj.choices[1].finish_reason
+    local content = obj.choices[1].delta.content
+    if finish_reason == vim.NIL then
+      local lines = vim.split(content, "\n", { plain = true, trimempty = false })
+      local last_line, last_column = require("dante.utils").last(res.buf)
+      vim.api.nvim_buf_set_text(res.buf, last_line, last_column, last_line, last_column, lines)
+      if opts.verbose and obj.usage then
+        vim.notify("usage = " .. vim.inspect(obj.usage), vim.log.levels.INFO)
+      end
+    elseif finish_reason == "stop" then
+      vim.notify("Done.", vim.log.levels.INFO)
+    else
+      vim.notify("An error occured during text genereation.", vim.log.levels.ERROR)
+    end
+  end
+end
+
+---Callback function to handle the exit of a chat request.
+---@param res table
+---@param req table
+---@param opts Options
+---@param after_lines string[]
+---@return function
+M.on_exit = function(res, req, opts, after_lines)
+  return function()
+    vim.api.nvim_buf_set_lines(res.buf, -1, -1, true, after_lines)
+    vim.api.nvim_set_current_win(res.win)
+    vim.cmd("diffthis")
+    vim.api.nvim_set_current_win(req.win)
+    vim.cmd("diffthis")
+  end
+end
+
+return M
diff --git a/lua/dante/init.lua b/lua/dante/init.lua
index 4dc147b..e38e31d 100644
--- a/lua/dante/init.lua
+++ b/lua/dante/init.lua
@@ -1,168 +1,112 @@
 local ai = require("ai")
+local utils = require("dante.utils")
+local callbacks = require("dante.callbacks")
 
 local dante = {}
 
----Setup global options for Dante
----@param options Options: global optoins for Dante.
+--- Setup global options for Dante
+---@param options Options: global options for Dante
 function dante.setup(options)
   require("dante.config").setup(options)
 end
 
----Replace all placeholders in the content string
----@param content string: The content string to be formatted
----@param start_line integer: The start line of the selected text
----@param end_line integer: The end line of the selected text
----@param buf integer: The buffer number of the selected text
----@return string: The formatted content string
-function dante.format(content, start_line, end_line, buf)
-  local result = ""
-  local last_end = 1
-
-  -- Function to get the replacement for a placeholder
-  local function get_replacement(placeholder)
-    if placeholder == "{{SELECTED_LINES}}" then
-      local range_lines = vim.api.nvim_buf_get_lines(0, start_line - 1, end_line, false)
-      return table.concat(range_lines, "\n")
-    elseif placeholder == "{{NOW}}" then
-      return os.date("Today is %a, %d %b %Y %H:%M:%S %z")
-    -- Add other placeholders here...
-    else
-      -- If not recognized, keep the original placeholder
-      vim.notify("Unrecognized placeholder: " .. placeholder, vim.log.levels.WARN)
-      return placeholder
-    end
-  end
+--- Setup the UI for Dante
+---@param opts Options: The options for Dante
+local function setup_ui(opts)
+  -- Diff options
+  local diff = {
+    "internal",
+    "filler",
+    "closeoff",
+    "followwrap",
+    "iblank",
+  }
+  vim.cmd("set diffopt=" .. table.concat(diff, ","))
+
+  -- Request
+  local req = {
+    name = vim.api.nvim_buf_get_name(0),
+    buf = vim.api.nvim_get_current_buf(),
+    win = vim.api.nvim_get_current_win(),
+  }
+
+  local buf_opts = {
+    ft = vim.bo.filetype,
+  }
+
+  local win_opts = {
+    wrap = vim.wo.wrap,
+    lbr = vim.wo.linebreak,
+    bri = vim.wo.breakindent,
+  }
 
-  -- Find and replace all placeholders
-  for placeholder_start, placeholder_end in content:gmatch("(){{.-}}()") do
-    local placeholder = content:sub(placeholder_start, placeholder_end - 1)
-    result = result .. content:sub(last_end, placeholder_start - 1)
-    result = result .. get_replacement(placeholder)
-    last_end = placeholder_end
+  -- Response
+  local res = {
+    buf = vim.api.nvim_create_buf(false, true),
+    name = utils.generate_buf_name(),
+  }
+  vim.api.nvim_buf_set_name(res.buf, res.name)
+  for opt, value in pairs(buf_opts) do
+    vim.api.nvim_set_option_value(opt, value, { buf = res.buf })
   end
 
-  -- Append any remaining content after the last placeholder
-  result = result .. content:sub(last_end)
-
-  return result
-end
-
----Get the last line, column and line count in the chat buffer
----Thanks to Oli Morris for this function
----https://github.com/olimorris/codecompanion.nvim/blob/
----  f8db284e1197a8cc4235afa30dcc3e8d4f3f45a5
----  /lua/codecompanion/strategies/chat.lua#L987
----@param buf integer: The buffer number
----@return integer: number of the last line
----@return integer: number of columns in the last line
-local function last(buf)
-  local line_count = vim.api.nvim_buf_line_count(buf)
-  local last_line = line_count - 1
-  if last_line < 0 then
-    return 0, 0
-  end
-  local last_line_content = vim.api.nvim_buf_get_lines(buf, -2, -1, false)
-  if not last_line_content or #last_line_content == 0 then
-    return last_line, 0
+  -- TODO: do not open the window if overlay | vertical | horizontal
+  res.win = vim.api.nvim_open_win(res.buf, true, { split = "right", win = req.win })
+  for opt, value in pairs(win_opts) do
+    vim.api.nvim_set_option_value(opt, value, { win = res.win })
   end
-  local last_column = #last_line_content[1]
-  return last_line, last_column
+
+  return req, res
 end
 
----Represents a chat completion request to be sent to the model.
----Reference: https://platform.openai.com/docs/api-reference/chat/create
+--- Represents a chat completion request to be sent to the model.
+--- Reference: https://platform.openai.com/docs/api-reference/chat/create
 ----@alias RequestObject table (already defined in ai.nvim)
 
----Run Dante with the given preset
----@param preset_key string: One of the preset from options
+--- Run Dante with the given preset
+---@param preset_key string: One of the presets from options
 ---@param start_line integer: The start line of the selected text
 ---@param end_line integer: The end line of the selected text
 ---@return integer: Job id of the running job (curl request)
 function dante.main(preset_key, start_line, end_line)
+  local opts = require("dante.config").options
+
   -- LLM Client
-  local options = require("dante.config").options
-  local preset = vim.deepcopy(options.presets[preset_key])
+  local preset = vim.deepcopy(opts.presets[preset_key])
   local client = ai.Client:new(preset.client.base_url, preset.client.api_key)
 
   -- Format the messages content (e.g. substitute selected text)
   for _, message in ipairs(preset.request.messages) do
-    message.content = dante.format(message.content, start_line, end_line)
+    message.content = utils.format(message.content, start_line, end_line)
   end
 
-  -- Request UI
-  local req_win = vim.api.nvim_get_current_win()
-  local req_buf = vim.api.nvim_get_current_buf()
-  local filetype = vim.bo.filetype
-  local wrap = vim.wo.wrap
-  local linebreak = vim.wo.linebreak
-  local breakindent = vim.wo.breakindent
-  vim.cmd("set diffopt=internal,filler,closeoff,followwrap,iblank")
-
-  -- Generate a unique buffer name
-  local current_time = os.time()
-  local hex_time = string.format("%x", current_time)
-  local res_buf_name = "[Dante] " .. hex_time
-
-  -- Response
-  vim.cmd("vsplit")
-  local res_win = vim.api.nvim_get_current_win()
-  local res_buf = vim.api.nvim_create_buf(false, true)
-  vim.api.nvim_win_set_buf(res_win, res_buf)
-  vim.api.nvim_buf_set_name(res_buf, res_buf_name)
-  vim.api.nvim_set_option_value("filetype", filetype, { buf = res_buf })
-  vim.api.nvim_set_option_value("wrap", wrap, { win = res_win })
-  vim.api.nvim_set_option_value("linebreak", linebreak, { win = res_win })
-  vim.api.nvim_set_option_value("breakindent", breakindent, { win = res_win })
+  local req, res = setup_ui(opts)
 
   -- Partition request buffer
-  local before_lines = vim.api.nvim_buf_get_lines(req_buf, 0, start_line - 1, true)
-  local after_lines = vim.api.nvim_buf_get_lines(req_buf, end_line, -1, true)
+  local before_lines = vim.api.nvim_buf_get_lines(req.buf, 0, start_line - 1, true)
+  local after_lines = vim.api.nvim_buf_get_lines(req.buf, end_line, -1, true)
 
   -- Add line before the response
-  vim.api.nvim_buf_set_lines(res_buf, 0, 0, true, before_lines)
-  vim.api.nvim_win_set_cursor(res_win, { start_line, 0 })
-
-  local function on_chat_completion(obj)
-    local finish_reason = obj.choices[1].finish_reason
-    local content = obj.choices[1].message.content
-    if finish_reason == "stop" then
-      local lines = vim.split(content, "\n", { plain = true, trimempty = false })
-      vim.api.nvim_buf_set_lines(res_buf, -2, -1, true, lines)
-      if options.verbose and obj.usage then
-        vim.notify("usage = " .. vim.inspect(obj.usage), vim.log.levels.INFO)
-      end
-      vim.notify("Done.", vim.log.levels.INFO)
-    else
-      vim.notify("An error occured during text genereation.", vim.log.levels.ERROR)
-    end
-  end
-
-  local function on_chat_completion_chunk(obj)
-    local finish_reason = obj.choices[1].finish_reason
-    local content = obj.choices[1].delta.content
-    if finish_reason == vim.NIL then
-      local lines = vim.split(content, "\n", { plain = true, trimempty = false })
-      local last_line, last_column = last(res_buf)
-      vim.api.nvim_buf_set_text(res_buf, last_line, last_column, last_line, last_column, lines)
-      if options.verbose and obj.usage then
-        vim.notify("usage = " .. vim.inspect(obj.usage), vim.log.levels.INFO)
-      end
-    elseif finish_reason == "stop" then
-      vim.notify("Done.", vim.log.levels.INFO)
-    else
-      vim.notify("An error occured during text genereation.", vim.log.levels.ERROR)
-    end
-  end
-
-  local function on_exit()
-    vim.api.nvim_buf_set_lines(res_buf, -1, -1, true, after_lines)
-    vim.api.nvim_set_current_win(res_win)
-    vim.cmd("diffthis")
-    vim.api.nvim_set_current_win(req_win)
-    vim.cmd("diffthis")
-  end
-
-  return client:chat_completion_create(preset.request, on_chat_completion, on_chat_completion_chunk, nil, nil, on_exit)
+  vim.api.nvim_buf_set_lines(res.buf, 0, 0, true, before_lines)
+
+  -- NOTE: maybe remove this
+  -- vim.api.nvim_win_set_cursor(res_win, { start_line, 0 })
+
+  local on_chat_completion = callbacks.on_chat_completion(res, opts)
+  local on_chat_completion_chunk = callbacks.on_chat_completion_chunk(res, opts)
+
+  local on_stdout = nil -- use ai.nvim on_stdout
+  local on_stderr = nil -- use ai.nvim on_stderr
+  local on_exit = callbacks.on_exit(res, req, opts, after_lines)
+
+  return client:chat_completion_create(
+    preset.request,
+    on_chat_completion,
+    on_chat_completion_chunk,
+    on_stdout,
+    on_stderr,
+    on_exit
+  )
 end
 
 return dante
diff --git a/lua/dante/utils.lua b/lua/dante/utils.lua
new file mode 100644
index 0000000..cc32eea
--- /dev/null
+++ b/lua/dante/utils.lua
@@ -0,0 +1,80 @@
+local M = {}
+
+---Get the last line, column and line count in the chat buffer
+---Thanks to Oli Morris for this function
+---https://github.com/olimorris/codecompanion.nvim/blob/
+---  f8db284e1197a8cc4235afa30dcc3e8d4f3f45a5
+---  /lua/codecompanion/strategies/chat.lua#L987
+---@param buf integer: The buffer number
+---@return integer: number of the last line
+---@return integer: number of columns in the last line
+M.last = function(buf)
+  local line_count = vim.api.nvim_buf_line_count(buf)
+  local last_line = line_count - 1
+  if last_line < 0 then
+    return 0, 0
+  end
+  local last_line_content = vim.api.nvim_buf_get_lines(buf, -2, -1, false)
+  if not last_line_content or #last_line_content == 0 then
+    return last_line, 0
+  end
+  local last_column = #last_line_content[1]
+  return last_line, last_column
+end
+
+---Generate a unique buffer name.
+---It uses the current time in hexadecimal format prefixed with "[Dante] ".
+---@return string: The generated buffer name
+M.generate_buf_name = function()
+  -- Generate a unique buffer name
+  local current_time = os.time()
+  local hex_time = string.format("%x", current_time)
+  local res_buf_name = "[Dante] " .. hex_time
+  return res_buf_name
+end
+
+---Replace all placeholders in the content string
+---This is the core function that enable the user specify how to add context in LLM requests.
+---Supported place holders are:
+---  - `{{SELECTED_LINES}}`: The selected lines in the editor from VISUAL mode
+---  - `{{NOW}}`: The current date and time
+---@param content string: The content string to be formatted
+---@param start_line integer: The start line of the selected text
+---@param end_line integer: The end line of the selected text
+---@return string: The formatted content string
+M.format = function(content, start_line, end_line)
+  local result = ""
+  local last_end = 1
+
+  ---Function to get the replacement for a placeholder
+  ---@param placeholder string: The placeholder to be replaced
+  ---@return string
+  local function get_replacement(placeholder)
+    if placeholder == "{{SELECTED_LINES}}" then
+      local range_lines = vim.api.nvim_buf_get_lines(0, start_line - 1, end_line, false)
+      return table.concat(range_lines, "\n")
+    elseif placeholder == "{{NOW}}" then
+      return tostring(os.date("Today is %a, %d %b %Y %H:%M:%S %z"))
+    -- Add other placeholders here...
+    else
+      -- If not recognized, keep the original placeholder
+      vim.notify("Unrecognized placeholder: " .. placeholder, vim.log.levels.WARN)
+      return placeholder
+    end
+  end
+
+  -- Find and replace all placeholders
+  for placeholder_start, placeholder_end in content:gmatch("(){{.-}}()") do
+    ---@diagnostic disable-next-line: param-type-mismatch
+    local placeholder = content:sub(placeholder_start, placeholder_end - 1)
+    result = result .. content:sub(last_end, placeholder_start - 1)
+    result = result .. get_replacement(placeholder)
+    last_end = placeholder_end
+  end
+
+  -- Append any remaining content after the last placeholder
+  result = result .. content:sub(last_end)
+  return result
+end
+
+return M