extract_transactions.php for Gnucash

<?php

/*
 * This script will remove transactions from a given GNUcash book file. This was useful to me
 * when I deleted a bunch of accounts and then was stuck with thousands of entries under
 * the "Imbalance" category. AFAIK, there is no official way to perform this action.
 *
 * To use:
 * 1. Make a copy of your gnucash file with a gzip extension: `cp my_file.gnucash my_file.gz`
 * 2. Un-gzip it: `gzip -d my_file.gz`
 * 3. Open it in a text editor and look for the <gnc:account> block for the account in question.
 *    Usually you can just text search for the account name.
 * 4. Copy down the GUID for the account, it will look something like:
 *      <act:id type="guid">585c23271c91aa83b48179a21b12683b</act:id>
 * 5. Modify the variables below based on the last few steps.
 * 6. Run the PHP script in the same directory as the GNUcash file: `php extract_transactions.php`
 * 7. Gzip the resulting file (it is the same name as the original with a '.out' extension on it)
 *    and rename it to `whatever_you_want.gnucash`.
 */

/* XXX ** Fill out these variables: **********/
$filename = 'my_file';
$guid = '';
/*********************************************/

$file = file($filename);
$file_out = fopen($filename.'.out', 'w');

// States:
// 0 - outside transaction
// 1 - inside transaction
// 2 - inside bad transaction
// 3 - exiting bad transaction
// 4 - exiting good transaction
$state = 0;

$str_trn_start = 'gnc:transaction';
$str_trn_stop = '/gnc:transaction';

$buffer = '';

foreach ($file as $line_num => $line) {
    if ($state == 0) {
        if (strpos($line, $str_trn_start)) {
            // We're entering a transaction
            $state = 1;
        } else {
            // We left a normal good line, write it
            fwrite($file_out, $line);
        }
    }

    // Buffer-building states
    if ($state == 1) {
        // if we're in a potentially good transaction, add the line to the buffer
        $buffer .= $line;
        // Check if this is a bad transaction
        if (strpos($line, $guid)) {
            $state = 2;
        }

        // Check if we're leaving this transaction
        if (strpos($line, $str_trn_stop)) {
            $state = 4;
        }
    }
    elseif ($state == 2) {
        // inside bad transaction

        // Check if we're leaving this transaction
        if (strpos($line, $str_trn_stop)) {
            $state = 3;
        }
    }

    // Buffer writing states
    if ($state == 3) {
        // We left a bad transaction. Clear the buffer and move on.
        $buffer = '';
        $state = 0;
    }
    elseif ($state == 4) {
        // We've left a good transaction, write the buffer
        echo "writing good transaction to file\n";
        fwrite($file_out, $buffer);
        $buffer = '';
        $state = 0;
    }

    //echo $state;
}

fclose($file_out);

?>