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<?php
// lib/Asciidoc.php

/**
 * Supplies functions that convert Asciidoc source text into HTML or PDF output.
 */
class Asciidoc
{
    /**
     * Converts Asciidoc source text into HTML output.
     *
     * @param string $source_text Asciidoc source text.
     */
    public static function convert_to_html($source_text)
    {
        return self::run_asciidoc($source_text);
    }

    /**
     * Converts Asciidoc source text into HTML output.
     *
     * @param string $source_text Asciidoc source text.
     */
    public static function convert_to_pdf($source_text)
    {
        return self::run_a2x($source_text);
    }

    /**
     * Runs the 'asciidoc' executable. Returns the resulting HTML as a string.
     *
     * @param string $source_text Asciidoc source text.
     */
    private static function run_asciidoc($source_text)
    {
        $result =
            self::run_shell_command(
                self::get_home_dir() . '/bin/asciidoc',
                array(
                    '--out-file=-',
                    '-',
                    self::SHELL_MULTILINE_TEXT_START
                        . self::SHELL_NEWLINE
                        . addslashes($source_text)
                        . self::SHELL_NEWLINE
                        . self::SHELL_MULTILINE_TEXT_END
                        . self::SHELL_NEWLINE,
                ));

        return $result;
    }

    /**
     * Runs the 'a2x' executable. Returns the resulting PDF as binary data.
     *
     * @param string $source_text Asciidoc source text.
     */
    private static function run_a2x($source_text)
    {
        $base_temp_file_path = tempnam(sys_get_temp_dir(), 'a2x');

        $temp_input_file_path = $base_temp_file_path . '.txt';
        $temp_output_file_path = $base_temp_file_path . '.pdf';

        file_put_contents($temp_input_file_path, $source_text);

        self::run_shell_command(
            self::get_home_dir() . '/bin/a2x',
            array(
                '--no-xmllint',
                '--format=pdf',
                '--conf-file='
                    . escapeshellarg(
                        self::get_home_dir() . '/.asciidoc/a2x.conf'),
                '--destination-dir='
                    . escapeshellarg(dirname($temp_output_file_path)),
                escapeshellarg($temp_input_file_path),
            ));

        return file_get_contents($temp_output_file_path);
    }

    /**
     * Runs a shell command.
     *
     * @param string $executable_path Path to the executable.
     * @param array $arguments
     *     Command-line arguments to pass to the executable.
     */
    private static function run_shell_command(
        $executable_path,
        array $arguments=array())
    {
        $command =
            escapeshellcmd($executable_path)
                . self::SHELL_ARGUMENT_SEPARATOR
                . implode(
                    self::SHELL_ARGUMENT_SEPARATOR,
                    $arguments);

        return system($command);
    }

    /**
     * Gets the current user's home directory.
     */
    private static function get_home_dir()
    {
        $process_user = posix_getpwuid(posix_geteuid());

        $result = '/home/' . $process_user['name'];

        return $result;
    }

    /**
     * Separator placed between command arguments, in the OS shell.
     */
    const SHELL_ARGUMENT_SEPARATOR = ' ';

    /**
     * Delimiter for the start of a multiline block of text, in the OS shell.
     */
    const SHELL_MULTILINE_TEXT_START = '<<EOF';

    /**
     * Delimiter for the end of a multiline block of text, in the OS shell.
     */
    const SHELL_MULTILINE_TEXT_END = 'EOF';

    /**
     * Newline, in the OS shell.
     *
     * Double quotes are necessary for an unescaped newline.
     * Single quotes result in an esacaped newline (backslash followed by the letter 'n').
     */
    const SHELL_NEWLINE = "\n";
}

?>