feat: pasting image within buffer (#331)

Signed-off-by: Aaron Pham <contact@aarnphm.xyz>

lua/avante/clipboard.lua

@@ -0,0 +1,74 @@
+---NOTE: this module is inspired by https://github.com/HakonHarnes/img-clip.nvim/tree/main
+---@see https://github.com/ekickx/clipboard-image.nvim/blob/main/lua/clipboard-image/paste.lua
+
+local Path = require("plenary.path")
+local Utils = require("avante.utils")
+local Config = require("avante.config")
+---@module "img-clip"
+local ImgClip = nil
+
+---@class AvanteClipboard
+---@field get_base64_content fun(filepath: string): string | nil
+---
+---@class avante.Clipboard: AvanteClipboard
+local M = {}
+
+---@type Path
+local paste_directory = nil
+
+---@return Path
+local function get_paste_directory()
+  if paste_directory then
+    return paste_directory
+  end
+  paste_directory = Path:new(Config.history.storage_path):joinpath("pasted_images")
+  return paste_directory
+end
+
+M.support_paste_image = Config.support_paste_image
+
+M.setup = function()
+  get_paste_directory()
+
+  if not paste_directory:exists() then
+    paste_directory:mkdir({ parent = true })
+  end
+
+  if M.support_paste_image() and ImgClip == nil then
+    ImgClip = require("img-clip")
+  end
+end
+
+---@param line string
+M.paste_image = function(line)
+  if not Config.support_paste_image() then
+    return false
+  end
+
+  return ImgClip.paste_image({
+    dir_path = paste_directory:absolute(),
+    prompt_for_file_name = false,
+    filetypes = {
+      AvanteInput = { url_encode_path = true, template = "\nimage: $FILE_PATH\n" },
+    },
+  }, line)
+end
+
+---@param filepath string
+M.get_base64_content = function(filepath)
+  local os_mapping = Utils.get_os_name()
+  ---@type vim.SystemCompleted
+  local output
+  if os_mapping == "darwin" or os_mapping == "linux" then
+    output = Utils.shell_run(("cat %s | base64 | tr -d '\n'"):format(filepath))
+    if output.code == 0 then
+      return output.stdout
+    else
+      error("Failed to convert image to base64")
+    end
+  else
+    Utils.warn("Windows is not supported yet", { title = "Avante" })
+  end
+end
+
+return M