require 'nokogiri'

file = ARGV[0]

xml = Nokogiri::XML(File.read(file))

title = xml.css('title').text
content = xml.css('lyrics').text

def to_lines(content)
  file_lines = content.split("\n")
  lines = []

  pair = []

  file_lines.each do |line|
    if pair.any?
      pair << line[1..-1]
      pair[1] ||= ""
      lines << pair
      pair = []
    elsif line[0] == '.' && pair.empty?
      pair = [line[1..-1]]
    elsif line[0] == ' ' && pair.empty?
      pair = []
      lines << ["", line]
    elsif line =~ /\[V(\d*)\]/
      pair = []
      lines << ["", "Verse #{$1}:"]
    elsif line =~ /\[C(\d*)\]/
      pair = []
      number = $1.length != 0 ? " #{$1}" : ""
      lines << ["", "Chorus#{number}:"]
    elsif line =~ /\[PC(\d*)\]/
      pair = []
      number = $1.length != 0 ? " #{$1}" : ""
      lines << ["", "Prechorus#{number}:"]
    elsif line =~ /\[B(\d*)\]/
      pair = []
      number = $1.length != 0 ? " #{$1}" : ""
      lines << ["", "Bridge#{number}:"]
    elsif line.strip == ""
      pair = []
      lines << ["", ""]
    else
      pair = []
    end
  end

  lines
end

def get_chord_positions(chord_line)
  positions = []

  chord = ""
  start_pos = 0

  (0..chord_line.length - 1).each do |i|
    if chord_line[i] == ' ' && chord != ""
      positions << [chord, start_pos]
      chord = ""
      start_pos = 0
    end

    if chord_line[i] != ' '
      start_pos = i if chord == ""
      chord << chord_line[i]
    end
  end

  if chord != ""
    positions << [chord, start_pos]
  end

  positions
end

def interpolate_line(chord_positions, lyrics)
  output = lyrics.dup

  offset = 0

  chord_positions.each do |chord, position|
    insert_string = "[#{chord}]"
    if output.length < (position + offset)
      output << (" " * (position + offset - output.length))
    end
    output.insert(position + offset, insert_string)
    offset += insert_string.length
  end

  output.strip
end

lines = to_lines(content)
onsong = lines.map { |chords, lyrics| [get_chord_positions(chords), lyrics] }.map{ |chord_positions, lyrics| interpolate_line(chord_positions, lyrics) }

key = get_chord_positions(lines.find { |chords, lyrics| chords.length != 0 }[0])[0][0] rescue nil

puts title
puts "Key: [#{key}]" if key
onsong.each do |line|
  puts line
end