module BannerParse

# File lib/banner_parse.rb, line 87
def parse(args)
  text = TextUtil.squish(args)
  return { error: USAGE } if text.empty?

  prefix = strip_colour_prefix(text)
  return { error: prefix[:error] } if prefix[:error]

  text = prefix[:text]
  engine_part = strip_engine_prefix(text)
  return { error: engine_part[:error] } if engine_part[:error]

  text = engine_part[:text]
  segments = text.split(/\s+\.\s+/)
  heading = TextUtil.squish(segments.first).upcase
  return { error: "Heading is required." } if heading.empty?
  return { error: "Heading may be at most #{MAX_HEADING_LENGTH} characters." } if heading.length > MAX_HEADING_LENGTH
  unless HEADING_PATTERN.match?(heading)
    return { error: "Heading may only contain letters, digits, and spaces." }
  end

  subheadings = []
  segments.drop(1).each do |segment|
    piece = TextUtil.squish(segment)
    return { error: "Each subheading needs a label." } if piece.empty?

    label, body = piece.split(/\s+/, 2)
    subheadings << { label: label, body: body.to_s }
  end

  if subheadings.length > MAX_SUBHEADINGS
    return { error: "At most #{MAX_SUBHEADINGS} subheadings allowed." }
  end

  result = { heading: heading, subheadings: subheadings }
  result[:engine] = engine_part[:engine] if engine_part[:engine]
  if prefix.key?(:title_fg)
    result[:title_fg] = prefix[:title_fg]
    result[:title_bg] = prefix[:title_bg]
  end
  result
end

# File lib/banner_parse.rb, line 25
def strip_colour_prefix(text)
  squished = TextUtil.squish(text)
  return { text: squished } if squished.empty?

  if (match = squished.match(DUAL_COLOUR_ONLY_PATTERN))
    fg_colour = IrcFormat.parse_colour_spec(match[1])
    return fg_colour if fg_colour[:error]

    bg_colour = IrcFormat.parse_colour_spec(match[2])
    return bg_colour if bg_colour[:error]

    return { error: "Heading is required." }
  end

  if (match = squished.match(SPACE_COLOUR_PATTERN))
    fg_colour = IrcFormat.parse_colour_spec(match[1])
    return fg_colour if fg_colour[:error]

    bg_colour = IrcFormat.parse_colour_spec(match[2])
    return bg_colour if bg_colour[:error]

    return {
      text: match[3],
      title_fg: fg_colour[:fg],
      title_bg: bg_colour[:fg]
    }
  end

  return { text: squished } unless squished.match?(/\s/)

  first, rest = squished.split(/\s+/, 2)
  if first.match?(COLOUR_TOKEN_PATTERN)
    colour = IrcFormat.parse_colour_spec(first)
    return colour if colour[:error]

    return {
      text: rest,
      title_fg: colour[:fg],
      title_bg: colour[:bg]
    }
  end

  if first.match?(LOOKS_LIKE_COLOUR_PATTERN)
    return { error: "Invalid colour — use fg or fg,bg (0-98)." }
  end

  { text: squished }
end

# File lib/banner_parse.rb, line 74
def strip_engine_prefix(text)
  squished = TextUtil.squish(text)
  return { text: squished } if squished.empty?

  first, rest = squished.split(/\s+/, 2)
  engine = BannerEngines.resolve_id(first)
  return { text: squished } unless engine

  return { error: "Heading is required." } if rest.to_s.strip.empty?

  { engine: engine, text: rest }
end