#! /usr/bin/ruby

def quit(message, status=1)
  STDERR.puts(message)
  exit(status)
end

quit('usage: input [output]', 0) \
  if ARGV.empty? \
  or ARGV.length > 2 \
  or %w[-h --help].any? { |flag| ARGV.include?(flag) }

input, output = ARGV

output = input.delete_suffix('.typ') + '-expanded.typ' if output.nil?

quit('error: file does not exist') if not File.file?(input)

@source = File.read(input)

def show(location)
  eol = @source[location] == ?\n
  location -= 1 if eol
  left = (@source.rindex(?\n, location) || -1) + 1
  right = (@source.index(?\n, location) ||  0) - 1
  line = @source[left..right].rstrip
  prev, post = '', ''
  if left > 1
    prev_left = (@source.rindex(?\n, left - 2) || -1) + 1
    prev = @source[prev_left..(left - 2)].rstrip
  end
  if right != -1
    post_right = (@source.index(?\n, right + 2) || 0) - 1
    post = @source[(right + 2)..post_right].rstrip
  end
  offset = 0
  linenumber = 0
  until offset.nil? or offset >= location
    offset = @source.index(?\n, offset) + 1
    linenumber += 1
  end
  linenums = [-1, 0, 1].map { |d| linenumber + d }.map(&:to_s)
  width = linenums.map(&:length).max()
  a, b, c = linenums.map { |n| n.rjust(width) }
  s = ' ' * width
  location += 1 if eol
  STDERR.puts("\e[2m#{s} ┃\e[22m")
  STDERR.puts("\e[2m#{a} ┃ #{prev}\e[22m") if not prev.empty?
  STDERR.puts("\e[2m#{b} ┃ #{line}\e[22m")
  STDERR.puts("\e[2m#{s} ┇\e[22m #{' ' * (location - left)}\e[31m^\e[39m")
  STDERR.puts("\e[2m#{c} ┃ #{post}\e[22m") if not post.empty?
  STDERR.puts("\e[2m#{s} ┃\e[22m") if not post.empty?
end

def error(message, location)
  STDERR.puts("error: #{message}")
  show(location)
  exit(1)
end

BREAKPOINTS = /(?<!['"])[\[\(]|[\]\)](?!['"])|^ *\/\/ *pause *$/
PAUSE = /^ *\/\/ *pause *\n/

PAIRS = {
  ?[ => ?],
  ?( => ?),
}

offset = 0
parts = []

while true
  func = @source.index('#slide', offset)
  break if func.nil?

  parts << @source[offset...func]

  open = @source.index('[', func + 6)
  error('missing content after #slide', func + 6) if open.nil?
  # error('unexpected characters before opening bracket', open) \
  #   if not @source[(func + 6)...open].strip.empty?

  mark = open + 1
  stack = [[?], open]]

  while true
    match = BREAKPOINTS.match(@source, mark)
    error('unmatched opening delimiter', stack[-1]) if match.nil?
    case match.match(0)
    when ?[, ?(
      stack.push([PAIRS[match.match(0)], match.begin(0)])
    when ?], ?)
      delim, open = stack.pop()
      if delim != match.match(0)
        STDERR.puts("error: mismatched delimiters")
        STDERR.puts("info: opening delimiter here:")
        show(open)
        STDERR.puts("info: closing delimiter here:")
        show(match.begin(0))
        exit(1)
      end
    else
      parts << @source[func...match.begin(0)].gsub(PAUSE, '')
      parts << stack.reverse_each.map(&:first).join() + ?\n
    end
    mark = match.end(0)
    break if stack.empty?
  end

  parts << @source[func...mark]
  offset = mark
end

parts << @source[offset..]

File.write(output, parts.join())