From 241a45fe13482cf3fbc3eea9fd4d02e2ef56a0ce Mon Sep 17 00:00:00 2001
From: jinzhongjia <mail@nvimer.org>
Date: Tue, 3 Feb 2026 20:10:18 +0800
Subject: [PATCH] perf: optimize string concatenation with table.concat

Replace inefficient string concatenation loops with table.concat to improve performance when building base62 IDs and timestamp hex strings. Cache namespace ID creation in input_window to avoid repeated API calls.
---
 lua/opencode/id.lua              | 13 +++++++------
 lua/opencode/ui/input_window.lua |  9 ++++++---
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/lua/opencode/id.lua b/lua/opencode/id.lua
index c15b04d4..106089eb 100644
--- a/lua/opencode/id.lua
+++ b/lua/opencode/id.lua
@@ -18,14 +18,14 @@ local LENGTH = 26
 -- Generate random base62 string
 local function random_base62(length)
   local chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
-  local result = ''
+  local parts = {}
 
-  for _ = 1, length do
+  for i = 1, length do
     local rand = math.random(1, 62)
-    result = result .. chars:sub(rand, rand)
+    parts[i] = chars:sub(rand, rand)
   end
 
-  return result
+  return table.concat(parts)
 end
 
 -- Convert number to hex string with padding
@@ -81,11 +81,12 @@ local function generate_new_id(prefix, descending)
   end
 
   -- Extract 6 bytes (48 bits) from the timestamp
-  local time_bytes = ''
+  local time_parts = {}
   for i = 5, 0, -1 do
     local byte_val = band(rshift(now, i * 8), 0xff)
-    time_bytes = time_bytes .. to_hex_padded(byte_val, 1)
+    time_parts[6 - i] = to_hex_padded(byte_val, 1)
   end
+  local time_bytes = table.concat(time_parts)
 
   -- Generate random suffix
   local random_suffix = random_base62(LENGTH - 12)
diff --git a/lua/opencode/ui/input_window.lua b/lua/opencode/ui/input_window.lua
index 48f86a3c..a2021360 100644
--- a/lua/opencode/ui/input_window.lua
+++ b/lua/opencode/ui/input_window.lua
@@ -8,6 +8,9 @@ M._hidden = false
 M._toggling = false
 M._resize_scheduled = false
 
+-- Cache namespace ID to avoid repeated creation
+local placeholder_ns = vim.api.nvim_create_namespace('input_placeholder')
+
 local function get_content_height(windows)
   local line_count = vim.api.nvim_buf_line_count(windows.input_buf)
   if line_count <= 0 then
@@ -303,7 +306,7 @@ function M.refresh_placeholder(windows, input_lines)
     input_lines = vim.api.nvim_buf_get_lines(windows.input_buf, 0, -1, false)
   end
   if #input_lines == 1 and input_lines[1] == '' then
-    local ns_id = vim.api.nvim_create_namespace('input_placeholder')
+    local ns_id = placeholder_ns
     local win_width = vim.api.nvim_win_get_width(windows.input_win)
     local padding = string.rep(' ', win_width)
     local slash_key = config.get_key_for_function('input_window', 'slash_commands')
@@ -338,7 +341,7 @@ function M.refresh_placeholder(windows, input_lines)
       virt_text_pos = 'overlay',
     })
   else
-    vim.api.nvim_buf_clear_namespace(windows.input_buf, vim.api.nvim_create_namespace('input_placeholder'), 0, -1)
+    vim.api.nvim_buf_clear_namespace(windows.input_buf, placeholder_ns, 0, -1)
   end
 end
 
@@ -346,7 +349,7 @@ function M.clear_placeholder(windows)
   if not windows or not windows.input_buf then
     return
   end
-  vim.api.nvim_buf_clear_namespace(windows.input_buf, vim.api.nvim_create_namespace('input_placeholder'), 0, -1)
+  vim.api.nvim_buf_clear_namespace(windows.input_buf, placeholder_ns, 0, -1)
 end
 
 function M.recover_input(windows)