Lua - Find "tags" in string?

Question

I'm planning on using Lua patterns, unless there's a better way to do this.

I want to be able to parse a string, and look for "tags". For example, I'd like to find the '[color=???][/color]' part of a string, not care what comes after the equals, not care what's inbetween the tags and not care where the are in the string, as long as they are somewhere in the string, and that 'color=' has a hex value after it. Here is a sample string:

mystring = 'Hello, [color=#0026FF]world[/color]!'
--                 ^^^^^^^^^^^^^^^     ^^^^^^^^

Answer 1

Patterns in the manual

First step, split the tokens:

function split_tag(s, i)
  i = (i or 0) + 1
  local j = s:sub(i, i)
  if j == "" then
    return
  end
  j = s:find(j == "[" and "]" or ".%f[[\0]", i) or #s
  -- In Pre-5.2 Lua use %z instead of \0 in the pattern
  return j + 1, s:sub(i, j)
end
for k, v in split_tags, 'Hello, [color=#0026FF][bold]world[/bold][/color]!' do
  print(('%q\n'):format(v))
end

Thus, you get your input string

'Hello, [color=#0026FF][bold]world[/bold][/color]!'

split into

"Hello, "
"[color=#0026FF]"
"[bold]"
"world"
"[/bold]"
"[/color]"
"!"

Standard parentheses matching algorithm left as an exercise for the reader.