#!/usr/bin/env php
<?php # -*- coding: utf-8 mode: php -*- vim:sw=4:sts=4:et:ai:si:sta:fenc=utf-8

function wfBaseConvert( $input, $sourceBase, $destBase, $pad = 1, $lowercase = true ) {
  $input = strval( $input );
  if( $sourceBase < 2 ||
    $sourceBase > 36 ||
    $destBase < 2 ||
    $destBase > 36 ||
    $pad < 1 ||
    $sourceBase != intval( $sourceBase ) ||
    $destBase != intval( $destBase ) ||
    $pad != intval( $pad ) ||
    !is_string( $input ) ||
    $input == '' ) {
    return false;
  }
  $digitChars = ( $lowercase ) ? '0123456789abcdefghijklmnopqrstuvwxyz' : '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
  $inDigits = array();
  $outChars = '';

  // Decode and validate input string
  $input = strtolower( $input );
  for( $i = 0; $i < strlen( $input ); $i++ ) {
    $n = strpos( $digitChars, $input[$i] );
    if( $n === false || $n > $sourceBase ) {
      return false;
    }
    $inDigits[] = $n;
  }

  // Iterate over the input, modulo-ing out an output digit
  // at a time until input is gone.
  while( count( $inDigits ) ) {
    $work = 0;
    $workDigits = array();

    // Long division...
    foreach( $inDigits as $digit ) {
      $work *= $sourceBase;
      $work += $digit;

      if( $work < $destBase ) {
        // Gonna need to pull another digit.
        if( count( $workDigits ) ) {
          // Avoid zero-padding; this lets us find
          // the end of the input very easily when
          // length drops to zero.
          $workDigits[] = 0;
        }
      } else {
        // Finally! Actual division!
        $workDigits[] = intval( $work / $destBase );

        // Isn't it annoying that most programming languages
        // don't have a single divide-and-remainder operator,
        // even though the CPU implements it that way?
        $work = $work % $destBase;
      }
    }

    // All that division leaves us with a remainder,
    // which is conveniently our next output digit.
    $outChars .= $digitChars[$work];

    // And we continue!
    $inDigits = $workDigits;
  }

  while( strlen( $outChars ) < $pad ) {
    $outChars .= '0';
  }

  return strrev( $outChars );
}

function base36Sha1( $text ) {
  return wfBaseConvert( sha1( $text ), 16, 36, 31 );
}

if ($argc > 1) {
  $inf = fopen($argv[1], "rb");
  if ($inf === FALSE) exit(1);
  $close = TRUE;
} else {
  $inf = STDIN;
  $close = FALSE;
}

$data = stream_get_contents($inf);
fwrite(STDOUT, base36Sha1($data));
fwrite(STDOUT, "\n");

if ($close) fclose($inf);