Search each line for a pattern

search_lines.moon

-- Search for pattern on each line.
search_lines = (str, pattern) ->
  line = str\find '\n'

  if line == nil
    i = 0
    return ->
      if i ~= nil
        h, i, match = str\find '^'..pattern, i
        return h, i, match if h ~= nil

  else
    h, i, mid, match = 0, 1
    return ->

      -- First line first.
      if h == 0
        h, i, match = str\find "^#{pattern}\n"
        return h, i, match if h ~= nil
        h = 1

      -- Check if string is 3+ lines.
      if h == 1
        line = str\find '\n', line + 1
        mid = "\n#{pattern}\n" if line ~= nil

      -- Middle lines next.
      if mid ~= nil
        h, i, match = str\find p, i
        return h, i, match if h ~= nil
        mid = nil

      -- Last line last.
      if h ~= -1
        h = -1
        return str\find "\n#{pattern}$", i

for startIndex, endIndex, captured in search_lines(input, pattern)
  print startIndex, endIndex, captured

The captured variable only exists if () is used in the pattern.

You cannot use () more than once in the pattern.