Add first version of buffer and file completion

README.md

@@ -361,6 +361,8 @@ to consider a visual selection within an API request.
     -- Type of spinner animation to display while loading
     -- Available options: "dots", "line", "star", "bouncing_bar", "bouncing_ball"
     spinner_type = "star",
+    -- Show hints for context added through completion with @file, @buffer or @directory
+    show_context_hints = true
 }
 ```
 
@@ -522,6 +524,29 @@ require("parrot").setup {
 }
 ```
 
+## Completion
+
+Instead of using the [template placeholders](#template-placeholders),
+`parrot.nvim` supports inline completion via [nvim-cmp](https://github.com/hrsh7th/nvim-cmp) for additional contexts:
+
+- `@buffer:foo.txt` - Includes the content of the open buffer `foo.txt`
+- `@file:test.lua` - Includes the content of the file `test.lua`
+- `@directory:src/` - Includes all file contents from the directory `src/`
+
+> Hint: The option `show_context_hints` allows you to transparently see notifications about the
+actual file contents considered by the request. The completion keywords (e.g., `@file`) need to be placed
+on a **new line**!
+
+### Setup for nvim-cmp
+
+To enable `parrot.nvim` completions, add the source to your nvim-cmp configuration:
+
+```lua
+sources = cmp.config.sources({
+  { name = "parrot_completion" },
+}),
+```
+
 ## Statusline Support
 
 Knowing the current chat or command model can be shown using your favorite statusline plugin.

lua/parrot/chat_handler.lua

@@ -11,6 +11,7 @@ local Spinner = require("parrot.spinner")
 local Job = require("plenary.job")
 local pft = require("plenary.filetype")
 local ResponseHandler = require("parrot.response_handler")
+local completion = require("parrot.completion")
 
 local ChatHandler = {}
 
@@ -43,6 +44,7 @@ function ChatHandler:new(options, providers, available_providers, available_mode
       last_line1 = nil,
       last_line2 = nil,
     },
+    completion = completion,
   }, self)
 end
 
@@ -86,7 +88,6 @@ function ChatHandler:get_provider(is_chat)
 end
 
 --- Retrieves the current provider for chat or command.
----@param is_chat boolean True for chat provider, false for command provider.
 ---@return table | nil Provider table or nil if not found.
 function ChatHandler:buf_handler()
   local gid = utils.create_augroup("PrtBufHandler", { clear = true })
@@ -747,6 +748,11 @@ function ChatHandler:_chat_respond(params)
     spinner:start("calling API...")
   end
 
+  -- add completion context
+  for _, message in ipairs(messages) do
+    message.content = self.completion.context.insert_contexts(message.content)
+  end
+
   -- call the model and write response
   self:query(
     buf,
@@ -1511,6 +1517,11 @@ function ChatHandler:prompt(params, target, model_obj, prompt, template, reset_h
       spinner = Spinner:new(self.options.spinner_type)
       spinner:start("calling API...")
     end
+
+    -- add completion context
+    for _, message in ipairs(messages) do
+      message.content = self.completion.context.insert_contexts(message.content)
+    end
     self:query(
       buf,
       prov,