module IrcPaint

# File lib/irc_paint.rb, line 24
def block_at_plain_index(line, pos)
  return nil if pos.to_i < 1

  segments(line).find do |segment|
    pos >= segment[:plain_start] && pos <= segment[:plain_end]
  end
end

# File lib/irc_paint.rb, line 145
def control_char?(char)
  char == CTRL || char == RESET_ALL || char == BOLD || char == UNDERLINE
end

# File lib/irc_paint.rb, line 92
def parse_parts(line)
  parts = []
  index = 0
  plain = 0

  while index < line.length
    char = line[index]
    if control_char?(char)
      raw, code_fg, code_bg, advance = read_control(line, index)
      parts << { type: :code, raw: raw, fg: code_fg, bg: code_bg }
      index += advance
    else
      start = index
      index += 1 while index < line.length && !control_char?(line[index])
      content = line[start...index]
      next if content.empty?

      plain_start = plain + 1
      plain_end = plain + content.length
      parts << { type: :text, content: content, plain_start: plain_start, plain_end: plain_end }
      plain = plain_end
    end
  end

  parts
end

# File lib/irc_paint.rb, line 20
def plain_length(text)
  TextAlign.plain_length(text)
end

# File lib/irc_paint.rb, line 120
def read_control(line, index)
  char = line[index]
  case char
  when CTRL
    if index + 1 >= line.length || !line[index + 1].match?(/\d/)
      return [CTRL, nil, nil, 1]
    end

    match = line[index + 1..].match(COLOR_PATTERN)
    return [CTRL, nil, nil, 1] unless match

    raw = CTRL + match[0]
    fg = match[1].to_i
    bg = match[2] ? match[2].to_i : nil
    [raw, fg, bg, 1 + match[0].length]
  when RESET_ALL
    [RESET_ALL, nil, nil, 1]
  when BOLD, UNDERLINE
    [char, nil, nil, 1]
  else
    [char, nil, nil, 1]
  end
end

# File lib/irc_paint.rb, line 32
def recolor_at(line, pos, fg:, bg: nil)
  block = block_at_plain_index(line, pos)
  raise ArgumentError, "no colour block at position #{pos}" unless block

  recolor_segment(line, block, fg: fg, bg: bg)
end

# File lib/irc_paint.rb, line 39
def recolor_range(line, plain_start:, plain_end:, fg:, bg: nil)
  segment = segments(line).find do |entry|
    entry[:plain_start] == plain_start.to_i && entry[:plain_end] == plain_end.to_i
  end
  return line unless segment

  recolor_segment(line, segment, fg: fg, bg: bg)[:line]
end

# File lib/irc_paint.rb, line 77
def recolor_segment(line, segment, fg:, bg: nil)
  new_code = IrcFormat.color(fg, bg)
  updated = line.sub(
    /#{Regexp.escape(segment[:open_raw])}#{Regexp.escape(segment[:text])}/,
    "#{new_code}#{segment[:text]}"
  )
  {
    line: updated,
    plain_start: segment[:plain_start],
    plain_end: segment[:plain_end],
    fg: fg,
    bg: bg
  }
end

# File lib/irc_paint.rb, line 48
def segments(line)
  parts = parse_parts(line.to_s)
  text_segments = []
  open_raw = +""
  fg = nil
  bg = nil

  parts.each do |part|
    case part[:type]
    when :code
      open_raw = part[:raw]
      fg = part[:fg]
      bg = part[:bg]
    when :text
      text_segments << {
        text: part[:content],
        open_raw: open_raw,
        fg: fg,
        bg: bg,
        plain_start: part[:plain_start],
        plain_end: part[:plain_end]
      }
      open_raw = +""
    end
  end

  text_segments
end