perf(sidebar): update the buffer more efficiently (#724)

lua/avante/utils/init.lua

@@ -682,4 +682,46 @@ function M.create_new_buffer_with_file(filepath)
   return buf
 end
 
+---@param bufnr integer
+---@param new_lines string[]
+---@return { start_line: integer, end_line: integer, content: string[] }[]
+local function get_buffer_content_diffs(bufnr, new_lines)
+  local old_lines = api.nvim_buf_get_lines(bufnr, 0, -1, false)
+  local diffs = {}
+  local prev_diff_idx = nil
+  for i, line in ipairs(new_lines) do
+    if line ~= old_lines[i] then
+      if prev_diff_idx == nil then prev_diff_idx = i end
+    else
+      if prev_diff_idx ~= nil then
+        local content = vim.list_slice(new_lines, prev_diff_idx, i - 1)
+        table.insert(diffs, { start_line = prev_diff_idx, end_line = i, content = content })
+        prev_diff_idx = nil
+      end
+    end
+  end
+  if prev_diff_idx ~= nil then
+    table.insert(
+      diffs,
+      { start_line = prev_diff_idx, end_line = #new_lines + 1, content = vim.list_slice(new_lines, prev_diff_idx) }
+    )
+  end
+  if #new_lines < #old_lines then
+    table.insert(diffs, { start_line = #new_lines + 1, end_line = #old_lines + 1, content = {} })
+  end
+  table.sort(diffs, function(a, b) return a.start_line > b.start_line end)
+  return diffs
+end
+
+--- Update the buffer content more efficiently by only updating the changed lines
+---@param bufnr integer
+---@param new_lines string[]
+function M.update_buffer_content(bufnr, new_lines)
+  local diffs = get_buffer_content_diffs(bufnr, new_lines)
+  if #diffs == 0 then return end
+  for _, diff in ipairs(diffs) do
+    api.nvim_buf_set_lines(bufnr, diff.start_line - 1, diff.end_line - 1, false, diff.content)
+  end
+end
+
 return M