#!/usr/bin/env ruby
#
# This script replaces all attempts in a Vanilla demo to switch directly
# to the super shotgun with attempts to switch to the normal shotgun 
# (which should work correctly assuming the player _has_ the super
# shotgun).

raise "Usage: demo-fixer <infile> <outfile>" if ARGV.length < 2

infile = File.open(ARGV[0], "rb")
outfile = File.open(ARGV[1], "wb")

# demo header

13.times do 
    c = infile.getc
    outfile.putc(c)
end

EOF = 0x80
CHANGE = 4
WEAPONMASK = 8 + 16 + 32 + 64
WEAPONSHIFT = 3
WEAP_SSG = 8
WEAP_SHOTGUN = 2

# read all ticcmds

loop do
    # read a ticcmd

    forward = infile.getc

    if forward == EOF
        # end of file?
        outfile.putc(EOF)
        break
    end
    side = infile.getc
    angle = infile.getc
    buttons = infile.getc

    if (buttons & CHANGE) != 0
        weap = (buttons & WEAPONMASK) >> WEAPONSHIFT
        if weap == WEAP_SSG
            # ssg!

            # mask out the weapon number

            buttons = buttons & ~WEAPONMASK

            # if they are switching to the ssg, they probably have it

            buttons |= WEAP_SHOTGUN << WEAPONSHIFT
        end
    end

    # write the new ticcmd to the file

    outfile.putc(forward)
    outfile.putc(side)
    outfile.putc(angle)
    outfile.putc(buttons)
end

infile.close
outfile.close