feat(clipboard): initial support (#279)

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

lua/avante/clipboard/darwin.lua

@@ -0,0 +1,59 @@
+local Utils = require("avante.utils")
+
+---@class AvanteClipboard
+local M = {}
+
+M.clip_cmd = nil
+
+M.get_clip_cmd = function()
+  if M.clip_cmd then
+    return M.clip_cmd
+  end
+  if vim.fn.executable("pngpaste") == 1 then
+    M.clip_cmd = "pngpaste"
+  elseif vim.fn.executable("osascript") == 1 then
+    M.clip_cmd = "osascript"
+  end
+  return M.clip_cmd
+end
+
+M.has_content = function()
+  local cmd = M.get_clip_cmd()
+  ---@type vim.SystemCompleted
+  local output
+
+  if cmd == "pngpaste" then
+    output = Utils.shell_run("pngpaste -")
+    return output.code == 0
+  elseif cmd == "osascript" then
+    output = Utils.shell_run("osascript -e 'clipboard info'")
+    return output.code == 0 and output.stdout ~= nil and output.stdout:find("class PNGf") ~= nil
+  end
+
+  Utils.warn("Failed to validate clipboard content", { title = "Avante" })
+  return false
+end
+
+M.get_content = function()
+  local cmd = M.get_clip_cmd()
+  ---@type vim.SystemCompleted
+  local output
+
+  if cmd == "pngpaste" then
+    output = Utils.shell_run("pngpaste - | base64 | tr -d '\n'")
+    if output.code == 0 then
+      return output.stdout
+    end
+  elseif cmd == "osascript" then
+    output = Utils.shell_run(
+      [[osascript -e 'set theFile to (open for access POSIX file "/tmp/image.png" with write permission)' -e 'try' -e 'write (the clipboard as «class PNGf») to theFile' -e 'end try' -e 'close access theFile'; ]]
+        .. [[cat /tmp/image.png | base64 | tr -d '\n']]
+    )
+    if output.code == 0 then
+      return output.stdout
+    end
+  end
+  error("Failed to get clipboard content")
+end
+
+return M