#!/usr/bin/ruby

require 'gdbm'

def xyz(lat, lon)
  phi = Math::PI * lat / 180.0
  lam = Math::PI * lon / 180.0
  z = Math::sin(phi)
  x = Math::cos(phi) * Math::cos(lam)
  y = Math::cos(phi) * Math::sin(lam)
  [x, y, z]
end

dbfile = ARGV.shift
raise "usage: #$0 dbfile [input ...]" unless dbfile
GDBM.open(dbfile) {|db|
  stations = db.keys
  for cccc in stations
    r = Hash[*db[cccc].to_s.split(/\t/).map{|s| s.split(/:/, 2)}.flatten]
    la1, lo1, la2, lo2 = r.values_at('la1', 'lo1', 'la2', 'lo2')
    next unless la1 and lo1 and la2 and lo2
    la1, lo1, la2, lo2 = [la1, lo1, la2, lo2].map{|s| s.to_f}
    x1 = xyz(la1, lo1)
    x2 = xyz(la2, lo2)
    d12 = Math::hypot(Math::hypot(x2[0] - x1[0], x2[1] - x1[1]), x2[2] - x1[2])
    d12 = format('%6.2f', Math::asin(d12 * 0.5) / Math::PI * 360.0)
    r['d12'] = d12
    STDOUT.write "[#{cccc} #{d12}]"
    db[cccc] = r.to_a.sort.map{|kv| kv.join(':')}.join("\t")
  end
  puts '.'
}