module NickPattern

# File lib/nick_pattern.rb, line 98
def escape_char_class(chars)
  chars.chars.map do |c|
    case c
    when "\\", "]", "-", "^"
      "\\#{c}"
    else
      Regexp.escape(c)
    end
  end.join
end

# File lib/nick_pattern.rb, line 14
def match?(nick, entry)
  nick = nick.to_s
  entry = entry.to_s
  return nick.casecmp?(entry) unless pattern?(entry)

  re = to_regexp(entry)
  return false unless re

  !!(nick =~ re)
end

# File lib/nick_pattern.rb, line 57
def parse_char_class(pattern, start_idx)
  return nil unless pattern[start_idx] == "["

  i = start_idx + 1
  return nil if i >= pattern.length

  negated = false
  if pattern[i] == "!" || pattern[i] == "^"
    negated = true
    i += 1
  end

  return nil if i >= pattern.length

  chars = +""
  until pattern[i] == "]"
    return nil if i >= pattern.length

    if i + 2 < pattern.length && pattern[i + 1] == "-" && pattern[i + 2] != "]"
      from = pattern[i]
      to = pattern[i + 2]
      return nil if from.ord > to.ord

      (from.ord..to.ord).each { |cp| chars << cp.chr(Encoding::UTF_8) }
      i += 3
    else
      chars << pattern[i]
      i += 1
    end
  end

  i += 1
  body = if negated
           "[^#{escape_char_class(chars)}]"
         else
           "[#{escape_char_class(chars)}]"
         end

  { body: body, consumed: i - start_idx }
end

# File lib/nick_pattern.rb, line 10
def pattern?(entry)
  entry.to_s.match?(/[\*\?\[]/)
end

# File lib/nick_pattern.rb, line 25
def to_regexp(pattern)
  i = 0
  len = pattern.length
  re = +"\\A"

  while i < len
    char = pattern[i]
    case char
    when "*"
      re << ".*"
      i += 1
    when "?"
      re << "."
      i += 1
    when "["
      parsed = parse_char_class(pattern, i)
      return nil unless parsed

      re << parsed[:body]
      i += parsed[:consumed]
    else
      re << Regexp.escape(char)
      i += 1
    end
  end

  re << "\\z"
  Regexp.new(re, Regexp::IGNORECASE)
rescue RegexpError
  nil
end