Add reverse option to `search.find`

data/core/doc/search.lua

@@ -23,6 +23,45 @@ local function init_args(doc, line, col, text, opt)
 end
 
 
+local function plain_rfind(text, pattern, index)
+  local len = #text
+  text = text:reverse()
+  pattern = pattern:reverse()
+  if index >= 0 then
+    index = len - index + 1
+  else
+    index = index * -1
+  end
+  local s, e = text:find(pattern, index, true)
+  return e and len - e + 1, s and len - s + 1
+end
+
+
+local function rfind(text, pattern, index, plain)
+  if plain then return plain_rfind(text, pattern, index) end
+  local s, e = text:find(pattern)
+  local last_s, last_e
+  if index < 0 then index = #text - index + 1 end
+  while e and e <= index do
+    last_s, last_e = s, e
+    s, e = text:find(pattern, s + 1)
+  end
+  return last_s, last_e
+end
+
+
+local function rcmatch(re, text, index)
+  local s, e = re:cmatch(text)
+  local last_s, last_e
+  if index < 0 then index = #text - index + 1 end
+  while e and e <= index + 1 do
+    last_s, last_e = s, e
+    s, e = re:cmatch(text, s + 1)
+  end
+  return last_s, last_e
+end
+
+
 function search.find(doc, line, col, text, opt)
   doc, line, col, text, opt = init_args(doc, line, col, text, opt)
 
@@ -30,31 +69,49 @@ function search.find(doc, line, col, text, opt)
   if opt.regex then
     re = regex.compile(text, opt.no_case and "i" or "")
   end
-  for line = line, #doc.lines do
+  local start, finish, step = line, #doc.lines, 1
+  if opt.reverse then
+    start, finish, step = line, 1, -1
+  end
+  for line = start, finish, step do
     local line_text = doc.lines[line]
     if opt.regex then
-      local s, e = re:cmatch(line_text, col)
+      local s, e
+      if opt.reverse then
+        s, e = rcmatch(re, line_text, col - 1)
+      else
+        s, e = re:cmatch(line_text, col)
+      end
       if s then
         return line, s, line, e
       end
-      col = 1
+      col = opt.reverse and -1 or 1
     else
       if opt.no_case then
         line_text = line_text:lower()
       end
-      local s, e = line_text:find(text, col, true)
+      local s, e
+      if opt.reverse then
+        s, e = rfind(line_text, text, col - 1, true)
+      else
+        s, e = line_text:find(text, col, true)
+      end
       if s then
         return line, s, line, e + 1
       end
-      col = 1
+      col = opt.reverse and -1 or 1
     end
   end
 
   if opt.wrap then
-    opt = { no_case = opt.no_case, regex = opt.regex }
+    opt = { no_case = opt.no_case, regex = opt.regex, reverse = opt.reverse }
+    if opt.reverse then
+      return search.find(doc, #doc.lines, #doc.lines[#doc.lines], text, opt)
+    else
       return search.find(doc, 1, 1, text, opt)
     end
   end
+end
 
 
 return search