From a42470d8051e13863a5f22ab7f2a5e4316857527 Mon Sep 17 00:00:00 2001
From: glepnir <glephunter@gmail.com>
Date: Tue, 21 May 2024 15:28:26 +0800
Subject: [PATCH] improve performance close #14

---
 lua/indentmini/init.lua | 53 +++++++++++++++++++----------------------
 1 file changed, 25 insertions(+), 28 deletions(-)

diff --git a/lua/indentmini/init.lua b/lua/indentmini/init.lua
index be34ecb..c79aa35 100644
--- a/lua/indentmini/init.lua
+++ b/lua/indentmini/init.lua
@@ -19,20 +19,14 @@ ffi.cdef([[
   int get_sw_value(buf_T *buf);
   typedef int32_t linenr_T;
   int get_indent_lnum(linenr_T lnum);
-  char *ml_get_buf(buf_T *buf, linenr_T lnum, bool will_change);
+  colnr_T ml_get_len(linenr_T lnum);
   size_t strlen(const char *__s);
 ]])
 
 local cache = { snapshot = {} }
 
-local function line_is_empty(bufnr, lnum)
-  local err = ffi.new('Error')
-  local handle = ffi.C.find_buffer_by_handle(bufnr, err)
-  if lnum > cache.count then
-    return nil
-  end
-  local data = ffi.C.ml_get_buf(handle, lnum, false)
-  return tonumber(ffi.C.strlen(data)) == 0
+local function line_is_empty(lnum)
+  return tonumber(ffi.C.ml_get_len(lnum)) == 0
 end
 
 local function get_sw_value(bufnr)
@@ -50,56 +44,59 @@ local function non_or_space(row, col)
   return text and (#text == 0 or text == ' ') or false
 end
 
-local function find_row(bufnr, row, curindent, direction, render)
+local function find_in_snapshot(lnum)
+  if not cache.snapshot[lnum] then
+    cache.snapshot[lnum] = { get_indent(lnum), line_is_empty(lnum) }
+  end
+  return unpack(cache.snapshot[lnum])
+end
+
+local function find_row(row, curindent, direction, render)
   local target_row = row + direction
-  local snapshot = cache.snapshot
   while true do
-    local empty = line_is_empty(bufnr, target_row + 1)
+    if target_row < 0 or target_row > cache.count - 1 then
+      return INVALID
+    end
+    local target_indent, empty = find_in_snapshot(target_row + 1)
     if empty == nil then
       return INVALID
     end
-    local target_indent = snapshot[target_row + 1] or get_indent(target_row + 1)
-    snapshot[target_row + 1] = target_indent
     if target_indent == 0 and not empty and render then
       break
     elseif not empty and (render and target_indent > curindent or target_indent < curindent) then
       return target_row
     end
     target_row = target_row + direction
-    if target_row < 0 or target_row > cache.count - 1 then
-      return INVALID
-    end
   end
   return INVALID
 end
 
-local function current_line_range(winid, bufnr, shiftw)
+local function current_line_range(winid, shiftw)
   local row = api.nvim_win_get_cursor(winid)[1] - 1
   local indent = get_indent(row + 1)
   if indent == 0 then
     return INVALID, INVALID, INVALID
   end
-  local top_row = find_row(bufnr, row, indent, UP, false)
-  local bot_row = find_row(bufnr, row, indent, DOWN, false)
+  local top_row = find_row(row, indent, UP, false)
+  local bot_row = find_row(row, indent, DOWN, false)
   return top_row, bot_row, math.floor(indent / shiftw)
 end
 
 local function on_line(_, winid, bufnr, row)
-  local is_empty = line_is_empty(bufnr, row + 1)
+  local indent, is_empty = find_in_snapshot(row + 1)
   if is_empty == nil then
     return
   end
-  local indent = cache.snapshot[row + 1] or get_indent(row + 1)
   local top_row, bot_row
   if indent == 0 and is_empty then
-    top_row = find_row(bufnr, row, indent, UP, true)
-    bot_row = find_row(bufnr, row, indent, DOWN, true)
+    top_row = find_row(row, indent, UP, true)
+    bot_row = find_row(row, indent, DOWN, true)
     local top_indent = top_row >= 0 and get_indent(top_row + 1) or 0
     local bot_indent = bot_row >= 0 and get_indent(bot_row + 1) or 0
     indent = math.max(top_indent, bot_indent)
   end
   --TODO(glepnir): should remove this or before find_row ? duplicated
-  local reg_srow, reg_erow, cur_inlevel = current_line_range(winid, bufnr, cache.shiftwidth)
+  local reg_srow, reg_erow, cur_inlevel = current_line_range(winid, cache.shiftwidth)
   for i = 1, indent - 1, cache.shiftwidth do
     local col = i - 1
     local level = math.floor(col / cache.shiftwidth) + 1
@@ -109,10 +106,9 @@ local function on_line(_, winid, bufnr, row)
     end
     if col >= cache.leftcol and non_or_space(row, col) then
       opt.config.virt_text[1][2] = higroup
-      if line_is_empty and col > 0 then
+      if is_empty and col > 0 then
         opt.config.virt_text_win_col = i - 1
       end
-      --TODO(glepnir): store id with changedtick then compare for performance
       buf_set_extmark(bufnr, ns, row, col, opt.config)
       opt.config.virt_text_win_col = nil
     end
@@ -133,8 +129,9 @@ local function on_win(_, winid, bufnr, topline, botline)
   cache.leftcol = vim.fn.winsaveview().leftcol
   cache.shiftwidth = get_sw_value(bufnr)
   cache.count = api.nvim_buf_line_count(bufnr)
+  cache.tick = api.nvim_buf_get_changedtick(bufnr)
   for i = topline, botline do
-    cache.snapshot[i] = get_indent(i)
+    cache.snapshot[i + 1] = { get_indent(i + 1), line_is_empty(i + 1) }
   end
 end