<?php

/**
 * OAI-PMH Harvest Tool
 *
 * PHP version 7
 *
 * Copyright (c) Demian Katz 2010.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * @category VuFind
 * @package  Harvest_Tools
 * @author   Demian Katz <demian.katz@villanova.edu>
 * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
 * @link     https://vufind.org/wiki/indexing:oai-pmh Wiki
 */

namespace VuFindHarvest\OaiPmh;

use VuFindHarvest\ConsoleOutput\WriterAwareTrait;
use VuFindHarvest\Exception\OaiException;

use function count;

/**
 * OAI-PMH Harvest Tool
 *
 * @category VuFind
 * @package  Harvest_Tools
 * @author   Demian Katz <demian.katz@villanova.edu>
 * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
 * @link     https://vufind.org/wiki/indexing:oai-pmh Wiki
 */
class Harvester
{
    use WriterAwareTrait;

    /**
     * Record writer
     *
     * @var RecordWriter
     */
    protected $writer;

    /**
     * Low-level OAI-PMH communicator
     *
     * @var Communicator
     */
    protected $communicator;

    /**
     * State manager
     *
     * @var StateManager
     */
    protected $stateManager;

    /**
     * Target set(s) to harvest (null for all records)
     *
     * @var string|array
     */
    protected $set = null;

    /**
     * Metadata type to harvest
     *
     * @var string
     */
    protected $metadataPrefix = 'oai_dc';

    /**
     * Harvest end date (null for no specific end)
     *
     * @var string
     */
    protected $harvestEndDate;

    /**
     * Harvest start date (null for no specific start)
     *
     * @var string
     */
    protected $startDate = null;

    /**
     * Date granularity ('auto' to autodetect)
     *
     * @var string
     */
    protected $granularity = 'auto';

    /**
     * Identify information from OAI host
     *
     * @var stdClass
     */
    protected $identifyResponse = null;

    /**
     * Flag to limit number of harvested records (null = no limit).
     * Used only for testing.
     *
     * @var ?int
     */
    protected $stopAfter = null;

    /**
     * Count harvested records.
     */
    protected $recordsCount = 0;

    /**
     * Constructor.
     *
     * @param Communicator $communicator Low-level API client
     * @param RecordWriter $writer       Record writer
     * @param StateManager $stateManager State manager
     * @param array        $settings     OAI-PMH settings
     */
    public function __construct(
        Communicator $communicator,
        RecordWriter $writer,
        StateManager $stateManager,
        $settings = []
    ) {
        // Don't time out during harvest!!
        set_time_limit(0);

        // Store dependencies
        $this->communicator = $communicator;
        $this->writer = $writer;
        $this->stateManager = $stateManager;

        // Store other settings
        $this->storeDateSettings($settings);
        $this->storeMiscSettings($settings);
    }

    /**
     * Set an end date for the harvest (only harvest records BEFORE this date).
     *
     * @param string $date End date (YYYY-MM-DD format).
     *
     * @return void
     */
    public function setEndDate($date)
    {
        $this->harvestEndDate = $date;
    }

    /**
     * Set a start date for the harvest (only harvest records AFTER this date).
     *
     * @param string $date Start date (YYYY-MM-DD format).
     *
     * @return void
     */
    public function setStartDate($date)
    {
        $this->startDate = $date;
    }

    /**
     * Harvest all available documents.
     *
     * @return void
     *
     * @throws \Exception
     */
    public function launch()
    {
        // Normalize sets setting to an array:
        $sets = (array)$this->set;
        if (empty($sets)) {
            $sets = [null];
        }

        // The harvestEndDate may be null. Some OAI-PMH hosts may depend on a
        // null value for backwards compatibility and reliability for various
        // edge cases, so we allow a null value to be used during the initial
        // records request. However, we still need to track an explicit end
        // date, based on the current OAI server time, as the basis for future
        // harvest start ranges. Note that this value can also be declared via
        // state data as it should always track the time the harvest was
        // first started.
        // @see https://github.com/vufind-org/vufindharvest/issues/7
        if (empty($this->harvestEndDate)) {
            $explicitHarvestEndDate = $this->getIdentifyResponse()->responseDate;
            // Add support for OAI-PMH hosts that require day granularity by
            // converting the date format if necessary.
            $granularity = $this->granularity == 'auto' ?
                $this->getIdentifyResponse()->granularity : $this->granularity;
            if ($granularity == 'YYYY-MM-DD') {
                $explicitHarvestEndDate = substr($explicitHarvestEndDate, 0, 10);
            }
        } else {
            $explicitHarvestEndDate = $this->harvestEndDate;
        }

        // Load last state, if applicable (used to recover from server failure).
        if ($state = $this->stateManager->loadState()) {
            $this->write("Found saved state; attempting to resume.\n");
            // State data must contain 4 values for reliable resumption.
            if (count($state) !== 4) {
                $this->stateManager->clearState();
                throw new \Exception(
                    'Corrupt or incomplete state data detected; '
                    . 'removing last_state.txt. Please restart harvest.'
                );
            }
            [
                $resumeSet,
                $resumeToken,
                $this->startDate,
                $explicitHarvestEndDate
            ] = $state;
        }

        // Loop through all of the selected sets:
        foreach ($sets as $set) {
            // If we're resuming and there are multiple sets, find the right one.
            if (isset($resumeToken) && $resumeSet != $set) {
                continue;
            }

            // If we have a token to resume from, pick up there now...
            if (isset($resumeToken)) {
                $token = $resumeToken;
                unset($resumeToken);
            } else {
                // ...otherwise, start harvesting at the requested date:
                $token = $this->getRecordsByDate(
                    $this->startDate,
                    $set,
                    $this->harvestEndDate
                );
            }

            // Keep harvesting as long as a resumption token is provided:
            while ($token !== false) {
                // If stopAfter is set, stop harvesting after given limit
                if (
                    !empty($this->stopAfter)
                    && $this->recordsCount >= $this->stopAfter
                ) {
                    $this->writeLine(
                        'reached limit of records to harvest: ' . $this->stopAfter
                    );
                    $this->writeLine('stop harvesting.');
                    $token = false;
                    break;
                }
                // Save current state in case we need to resume later:
                $this->stateManager->saveState(
                    $set,
                    $token,
                    $this->startDate,
                    $explicitHarvestEndDate
                );
                $token = $this->getRecordsByToken($token);
            }
        }

        // If we made it this far, all was successful. Save last harvest info and
        // clean up the stored state (unless we have a limit imposed by stopAfter)
        if (empty($this->stopAfter)) {
            $this->stateManager->saveDate($explicitHarvestEndDate);
        }
        $this->stateManager->clearState();
    }

    /**
     * Make an OAI-PMH request.  Die if there is an error; return a SimpleXML object
     * on success.
     *
     * @param string $verb   OAI-PMH verb to execute.
     * @param array  $params GET parameters for ListRecords method.
     *
     * @return object        SimpleXML-formatted response.
     */
    protected function sendRequest($verb, $params = [])
    {
        $response = $this->communicator->request($verb, $params);
        $this->checkResponseForErrors($response);
        return $response;
    }

    /**
     * Check an OAI-PMH response for errors that need to be handled.
     *
     * @param object $result OAI-PMH response (SimpleXML object)
     *
     * @return void
     *
     * @throws \Exception
     * @throws OaiException
     */
    protected function checkResponseForErrors($result)
    {
        // Detect errors and die if one is found:
        if ($result->error) {
            $attribs = $result->error->attributes();

            // If this is a bad resumption token error and we're trying to
            // restore a prior state, we should clean up.
            if (
                $attribs['code'] == 'badResumptionToken'
                && $this->stateManager->loadState()
            ) {
                $this->stateManager->clearState();
                throw new \Exception(
                    'Token expired; removing last_state.txt. Please restart harvest.'
                );
            }
            throw new OaiException($attribs['code'], $result->error);
        }
    }

    /**
     * Harvest records using OAI-PMH.
     *
     * @param array $params GET parameters for ListRecords method.
     *
     * @return mixed        Resumption token if provided, false if finished
     */
    protected function getRecords($params)
    {
        // Make the OAI-PMH request:
        $response = $this->sendRequest('ListRecords', $params);

        // Save the records from the response:
        if ($response->ListRecords->record) {
            $newRecords = count($response->ListRecords->record);
            $this->writeLine(
                '[' . $this->recordsCount . ' records harvested] Processing '
                . $newRecords . ' records...'
            );
            // count numRecords
            $this->recordsCount += $newRecords;
            $this->writer->write($response->ListRecords->record);
        }

        // If we have a resumption token, keep going; otherwise, we're done.
        if (
            isset($response->ListRecords->resumptionToken)
            && !empty($response->ListRecords->resumptionToken)
        ) {
            return $response->ListRecords->resumptionToken;
        }
        return false;
    }

    /**
     * Harvest records via OAI-PMH using date and set.
     *
     * @param string $from  Harvest start date (null for no specific start).
     * @param string $set   Set to harvest (null for all records).
     * @param string $until Harvest end date (null for no specific end).
     *
     * @return mixed        Resumption token if provided, false if finished
     */
    protected function getRecordsByDate($from = null, $set = null, $until = null)
    {
        $params = ['metadataPrefix' => $this->metadataPrefix];
        if (!empty($from)) {
            $params['from'] = $from;
        }
        if (!empty($set)) {
            $params['set'] = $set;
        }
        if (!empty($until)) {
            $params['until'] = $until;
        }
        return $this->getRecords($params);
    }

    /**
     * Harvest records via OAI-PMH using resumption token.
     *
     * @param string $token Resumption token.
     *
     * @return mixed        Resumption token if provided, false if finished
     */
    protected function getRecordsByToken($token)
    {
        return $this->getRecords(['resumptionToken' => (string)$token]);
    }

    /**
     * Get identify information from OAI-PMH host. Unless $reset = TRUE, this
     * method will only invoke an OAI-PMH call upon its first usage and will
     * return cached data after that.
     *
     * @param boolean $reset Whether-or-not to reset identity information
     *                       already fetched during this request.
     *
     * @return stdClass       An object of response properties as defined by
     *                        http://www.openarchives.org/OAI/openarchivesprotocol.html#Identify
     *                        plus a 'responseDate' property representing the
     *                        datestamp of the identify response in the form
     *                        YYYY-MM-DDThh:mm:ssZ
     *
     * @see http://www.openarchives.org/OAI/openarchivesprotocol.html#Identify
     */
    protected function getIdentifyResponse($reset = false)
    {
        if (empty($this->identifyResponse) || $reset) {
            $response = $this->sendRequest('Identify');
            // Save callers the burden of casting XML elements by preparing a
            // flat list of string properties.
            $this->identifyResponse = (object)(array)$response->Identify;
            $this->identifyResponse->responseDate = (string)$response->responseDate;
        }
        return $this->identifyResponse;
    }

    /**
     * Set date range configuration (support method for constructor).
     *
     * @param array $settings Configuration
     *
     * @return void
     */
    protected function storeDateSettings($settings)
    {
        // Set up start/end dates:
        $from = empty($settings['from'])
            ? $this->stateManager->loadDate() : $settings['from'];
        $until = empty($settings['until']) ? null : $settings['until'];
        $this->setStartDate($from);
        $this->setEndDate($until);
    }

    /**
     * Set miscellaneous configuration (support method for constructor).
     *
     * @param array $settings Configuration
     *
     * @return void
     */
    protected function storeMiscSettings($settings)
    {
        if (isset($settings['set'])) {
            $this->set = $settings['set'];
        }
        if (isset($settings['metadataPrefix'])) {
            $this->metadataPrefix = $settings['metadataPrefix'];
        }
        if (isset($settings['dateGranularity'])) {
            $this->granularity = $settings['dateGranularity'];
        }
        if (isset($settings['stopAfter'])) {
            $this->stopAfter = $settings['stopAfter'];
        }
    }
}