#!/usr/bin/ruby -w

def time_from_str(str)
    if str =~ /^(\d+):(\d+):(\d+)(,\d+)?$/
        h, m, s = $1, $2, $3
        Time.local(2006, 1, 1, h.to_i, m.to_i, s.to_i)
    else
        raise ArgumentError, "Invalid syntax for time: #{str}"
    end
end

if ARGV.size != 3
    $stderr.puts "I need three parameters"
    $stderr.puts "#{$0} file.srt ref_srt_time ref_movie_time"
    exit(1)
end

filename       = ARGV.shift
srt_time_str   = ARGV.shift
movie_time_str = ARGV.shift

# Convert reference times to proper Time objects
start_time = Time.local(2006, 1, 1)
srt_time   = time_from_str(srt_time_str)
movie_time = time_from_str(movie_time_str)

factor = (srt_time - start_time) / (movie_time - start_time)

# For performance
h1, m1, s1, us1 = nil, nil, nil, nil
h2, m2, s2, us2 = nil, nil, nil, nil
t1, t2 = nil, nil
line, count = nil, nil
File.readlines(filename).each_with_index do |line,count|
    if line =~ /^(\d\d):(\d\d):(\d\d),(\d+) --> (\d\d):(\d\d):(\d\d),(\d+)/
        h1, m1, s1, us1, h2, m2, s2, us2 = $1, $2, $3, $4, $5, $6, $7, $8
        h1, m1, s1, us1 = h1.to_i, m1.to_i, s1.to_i, us1.to_i * 1_000
        h2, m2, s2, us2 = h2.to_i, m2.to_i, s2.to_i, us2.to_i * 1_000
        t1 = Time.local(2006, 1, 1, h1, m1, s1, us1)
        t2 = Time.local(2006, 1, 1, h2, m2, s2, us2)
        t1 = Time.at((t1.to_i - start_time.to_i) * factor)
        t2 = Time.at((t2.to_i - start_time.to_i) * factor)
        line = "#{t1.hour.to_s.rjust(2, '0')}:#{t1.min.to_s.rjust(2, '0')}:#{t1.sec.to_s.rjust(2, '0')},#{t1.usec / 1000} --> #{t2.hour.to_s.rjust(2, '0')}:#{t2.min.to_s.rjust(2, '0')}:#{t2.sec.to_s.rjust(2, '0')},#{t2.usec / 1000}\r\n"
    end

    $stderr.puts "#{count} lines..." if count % 100 == 0 and count != 0
    print line
end