<?php
/**
 * Example usage:
 *
 * // Initalize the client
 * $imap = DIOIMAP::init();
 *
 * // Initalize the email client without a postfix and search for the latest unread email
 * $emailMessage = DIOIMAP::init()->findEmail();
 *
 * // Reinitalize the stream, and find the latest email with the subject "Test 123"
 * $secondEmail = $imap->reinit()->findEmail("Test 123");
 *
 * // Occasionally, the stream needs to be reset if the instance has done nothing for a while
 * $imap = $imap->reinit();
 * $imap->reinit()->findEmail();
 *
 */
class DIOIMAP {
    const _IMAP_HOST = '{imap.gmail.com:993/imap/ssl/novalidate-cert}INBOX';
    private $imapStream;
    private $user;
    private $password;
    private $expectedRecipient;
    private $subject;
    private $latestId;

    private static $lastPostfix = '';
    /**
     * Bootstrap a DIOIMAP object
     * @param $postfix (string) RFC 2822 email tag ex: $postfix = "testTag" -> $expectedRecipient = "myGmailAcct+testTag@gmail.com"
     */
    public static function init($postfix = '')
    {
        $key = 'myGmailAcct%s@gmail.com';
        $user = sprintf($key, "");
        $expectedRecipient = empty($postfix) ? $user : sprintf($key, "+$postfix");
        self::$lastPostfix = $postfix;

        return new self($user, 'password!@', $expectedRecipient);
    }

    /**
     * @param $user (string) IMAP Server username
     * @param $pass (string) IMAP Server password
     * @param $expectedRecipient (string) Expected recipient (in the "TO" field) of a set of email in the inbox
     */
    public function __construct($user, $pass, $expectedRecipient)
    {
        date_default_timezone_set("UTC");
        $this->user = $user;
        $this->password = $pass;
        $this->expectedRecipient = $expectedRecipient;
        $this->openConnection();
    }

    private static $TEMP_lastDate;
    /**
     * Return the latest email id meeting the specified recipient and subject criteria
     * @param $iteration (int) OPTIONAL The number used to identify the recursive position
     * @param $maxDepth (int) OPTIONAL The number used to limit the recursive depth.
     * @throws Exception No new emails found matching search criteria
     * @return (int) IMAP server id of the found email
     */
    private function refresh($iteration = 0, $maxDepth = 5)
    {
        $theNow = new DateTime();
        $emailStack = imap_search(
            $this->imapStream,
            sprintf("TO %s %s UNSEEN NEW",
                $this->expectedRecipient,
                empty($this->subject) ? "" : sprintf('SUBJECT "%s"', $this->subject)
            ),
            SE_UID
        );
        $this->close();
        $this->openConnection();

        var_dump("Returned Email Stack");
        var_dump($emailStack);
        if (!$emailStack)
        {
            if ($iteration < $maxDepth)
            {
                sleep(10);
                var_dump($this->imapStream);
                var_dump("Iteration: $iteration");
                var_dump("Time diff:\n");
                var_dump(self::$TEMP_lastDate->diff($theNow)->format("%h:%i:%s"));
                var_dump("\n\n");
                self::$TEMP_lastDate = $theNow;
                $this->refresh($iteration+1, $maxDepth);

            }
            throw new Exception(
                sprintf(
                    "No new emails found matching criteria: user=%s subject=%s attempt=%s depth=%s",
                    $this->expectedRecipient,
                    $this->subject,
                    $iteration,
                    $maxDepth
                )
            );
        }
        $this->latestId = array_pop($emailStack); // Get latest email only
        // foreach($emailStack as $mailId)
        // {
        //     imap_clearflag_full($this->imapStream, $mailId, "//Seen");
        // }
        return $this->latestId;
    }

    /**
     * Find and return the latest email meeting the specified recipient and subject criteria
     * @return (string) The email body
     */
    public function findEmail($subject = '')
    {
        $this->subject = $subject;
        self::$TEMP_lastDate = new DateTime();
        $this->refresh(0, 30);
        $emailBody = $this->fetch($this->latestId);
        $emailBody = $this->decode($emailBody);
        return $emailBody;
    }

    public function reinit()
    {
        $this->close();
        return self::init(self::$lastPostfix);
    }

    /**
     * Close the connection to the IMAP server
     */
    public function close()
    {
        imap_close($this->imapStream);
    }

    /**
     * Return the expected recipient
     * @return (string) The expected recipient
     */
    public function getRecipient()
    {
        return $this->expectedRecipient;
    }

    private function decode($emailBody)
    {
        $structure = imap_fetchstructure($this->imapStream, $this->latestId);
        switch ($structure->encoding)
        {
            case 3:
                $emailBody = imap_base64($emailBody);
                break;
            case 4:
            case 0:
                $emailBody = imap_qprint($emailBody);
                break;
            default:
                throw new Exception(
                    sprintf("Unknown encoding of email body encoding=%s", $structure->encoding)
                );
        }
        return $emailBody;
    }

    private function openConnection()
    {
        $this->imapStream = imap_open(self::_IMAP_HOST, $this->user, $this->password);
        if (!$this->imapStream) throw new Exception("Cannot connect to " . self::_IMAP_HOST);
    }

    private function fetch($msgNumber)
    {
        return imap_fetchbody($this->imapStream, $msgNumber, "2", FT_UID);
    }
}