<?php
// Own namespace
namespace Org\Mxchange\CoreFramework\Index;

// Import framework stuff
use Org\Mxchange\CoreFramework\Factory\Object\ObjectFactory;
use Org\Mxchange\CoreFramework\Filesystem\File\BaseBinaryFile;
use Org\Mxchange\CoreFramework\Generic\UnsupportedOperationException;
use Org\Mxchange\CoreFramework\Iterator\Filesystem\SeekableWritableFileIterator;
use Org\Mxchange\CoreFramework\Object\BaseFrameworkSystem;
use Org\Mxchange\CoreFramework\Utils\String\StringUtils;
use Org\Mxchange\CoreFramework\Traits\Iterator\IteratorTrait;

// Import SPL stuff
use \SplFileInfo;
use \UnexpectedValueException;

/**
 * A general index class
 *
 * @author		Roland Haeder <webmaster@ship-simu.org>
 * @version		0.0.0
 * @copyright	Copyright (c) 2007, 2008 Roland Haeder, 2009 - 2020 Core Developer Team
 * @license		GNU GPL 3.0 or any newer version
 * @link		http://www.ship-simu.org
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 */
abstract class BaseIndex extends BaseFrameworkSystem implements Indexable {
	// Load traits
	use IteratorTrait;

	/**
	 * Minimum block length
	 */
	private static $minimumBlockLength = 0;

	/**
	 * Protected constructor
	 *
	 * @param	$className	Name of the class
	 * @return	void
	 */
	protected function __construct (string $className) {
		// Call parent constructor
		parent::__construct($className);
	}

	/**
	 * Reads the file header
	 *
	 * @return	void
	 * @throws	UnexpectedValueException	If header length or count of elements is invalid
	 */
	public function readFileHeader () {
		// First rewind to beginning as the header sits at the beginning ...
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: CALLED!');
		$this->getIteratorInstance()->rewind();

		// Then read it (see constructor for calculation)
		$data = $this->getIteratorInstance()->read($this->getIteratorInstance()->getHeaderSize());

		// Have all requested bytes been read?
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput(sprintf('BASE-INDEX: Read %d bytes (%d wanted).', strlen($data), $this->getIteratorInstance()->getHeaderSize()));
		if (strlen($data) != $this->getIteratorInstance()->getHeaderSize()) {
			// Invalid header length
			throw new UnexpectedValueException(sprintf('data(%d)=%s is not expected length %d',
				strlen($data),
				$data,
				$this->getIteratorInstance()->getHeaderSize()
			));
		} elseif (empty(trim($data, chr(0)))) {
			// Empty file header
			/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: File header is empty - EXIT!');
			return;
		} elseif (substr($data, -1, 1) != chr(BaseBinaryFile::SEPARATOR_HEADER_ENTRIES)) {
			// Bad last character
			throw new UnexpectedValueException(sprintf('data=%s does not end with "%s"',
				$data,
				chr(BaseBinaryFile::SEPARATOR_HEADER_ENTRIES)
			));
		}

		// Okay, then remove it
		$data = substr($data, 0, -1);

		// And update seek position
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: Calling this->iteratorInstance->updateSeekPosition() ...');
		$this->getIteratorInstance()->updateSeekPosition();

		/*
		 * Now split it:
		 *
		 * 0 => magic
		 * 1 => total entries
		 */
		$header = explode(chr(BaseBinaryFile::SEPARATOR_HEADER_DATA), $data);

		// Check if the array has only 3 elements
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput(sprintf('BASE-INDEX: header()=%d', count($header)));
		//* PRINTR-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput(sprintf('BASE-INDEX: header(%d)=%s', count($header), print_r($header, true)));
		if (count($header) != 2) {
			// Bad header
			throw new UnexpectedValueException(sprintf('header()=%d is not expected value 2', count($header)));
		} elseif ($header[0] !== Indexable::INDEX_MAGIC) {
			// Magic must be in first element
			throw new UnexpectedValueException(sprintf('header[0]=%s is not the expected magic (%s)', $header[0], Indexable::INDEX_MAGIC));
		} elseif (strlen($header[1]) != BaseBinaryFile::LENGTH_COUNT) {
			// Length of total entries not matching
			throw new UnexpectedValueException(sprintf('header[1](%d)=%s does not have expected length %d', strlen($header[1]), $header[1], BaseBinaryFile::LENGTH_COUNT));
		}

		// Decode count
		$header[1] = hex2bin($header[1]);

		// Set it here
		$this->getIteratorInstance()->setHeader($header);

		// Trace message
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: EXIT!');
	}

	/**
	 * Flushes the file header
	 *
	 * @return	void
	 */
	public function flushFileHeader () {
		// Put all informations together
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: CALLED!');
		$header = sprintf('%s%s%s%s',
			// Magic
			Indexable::INDEX_MAGIC,

			// Separator header data
			chr(BaseBinaryFile::SEPARATOR_HEADER_DATA),

			// Total entries
			str_pad(StringUtils::dec2hex($this->getIteratorInstance()->getCounter()), BaseBinaryFile::LENGTH_COUNT, '0', STR_PAD_LEFT),

			// Separator header<->entries
			chr(BaseBinaryFile::SEPARATOR_HEADER_ENTRIES)
		);

		// Write it to disk (header is always at seek position 0)
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput(sprintf('BASE-INDEX: Calling this->iteratorInstance->writeAtPosition(0, header=%s) ...', $header));
		$this->getIteratorInstance()->writeAtPosition(0, $header);

		// Trace message
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: EXIT!');
	}

	/**
	 * Initializes this index
	 *
	 * @param	$fileInfoInstance	An instance of a SplFileInfo class
	 * @return	void
	 * @todo	Currently the index file is not cached, please implement a memory-handling class and if enough RAM is found, cache the whole index file.
	 */
	protected function initIndex (SplFileInfo $fileInfoInstance) {
		// Get a file i/o pointer instance for index file
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput(sprintf('BASE-INDEX: fileInfoInstance[%s]=%s - CALLED!', get_class($fileInfoInstance), $fileInfoInstance));
		$fileInstance = ObjectFactory::createObjectByConfiguredName('index_file_class', array($fileInfoInstance, $this));

		// Get iterator instance
		$iteratorInstance = ObjectFactory::createObjectByConfiguredName('file_iterator_class', [$fileInstance]);

		// Set iterator here
		$this->setIteratorInstance($iteratorInstance);

		// Calculate header size
		$headerSize = (
			strlen(Indexable::INDEX_MAGIC) +
			strlen(chr(BaseBinaryFile::SEPARATOR_HEADER_DATA)) +
			BaseBinaryFile::LENGTH_COUNT +
			strlen(chr(BaseBinaryFile::SEPARATOR_HEADER_ENTRIES))
		);

		// Set it
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput(sprintf('BASE-INDEX: Setting headerSize=%d ...', $headerSize));
		$this->getIteratorInstance()->setHeaderSize($headerSize);

		// Init counters and gaps array
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: Calling this->iteratorInstance->initCountersGapsArray() ...');
		$this->getIteratorInstance()->initCountersGapsArray();

		// Default is not created
		$created = false;

		// Is the file's header initialized?
		if (!$this->getIteratorInstance()->isFileHeaderInitialized()) {
			// First pre-allocate a bit
			/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: Calling this->iteratorInstance->preAllocateFile(index) ...');
			$this->getIteratorInstance()->preAllocateFile('index');

			// Then write file header
			/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: Calling this->iteratorInstance->createFileHeader() ...');
			$this->getIteratorInstance()->createFileHeader();

			// Mark as freshly created
			$created = true;
		}

		// Load the file header
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: Calling this->readFileHeader() ...');
		$this->readFileHeader();

		// Freshly created?
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput(sprintf('BASE-INDEX: created=%d', intval($created)));
		if (!$created) {
			// Analyze file structure
			/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: Calling this->iteratorInstance->analyzeFileStructure() ...');
			$this->getIteratorInstance()->analyzeFileStructure();
		}

		// Trace message
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: EXIT!');
	}

	/**
	 * Calculates minimum length for one entry/block
	 *
	 * @return	$length		Minimum length for one entry/block
	 */
	public function calculateMinimumBlockLength () {
		// Is it "cached"?
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: CALLED!');
		if (self::$minimumBlockLength == 0) {
			// Calulcate it
			//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput('BASE-INDEX: Calculating ...');
			self::$minimumBlockLength = (
				// Type
				BaseBinaryFile::LENGTH_TYPE + strlen(chr(BaseBinaryFile::SEPARATOR_TYPE_POSITION)) +
				// Position
				BaseBinaryFile::LENGTH_POSITION + strlen(chr(BaseBinaryFile::SEPARATOR_ENTRIES))
			);
		}

		// Return it
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput(sprintf('BASE-INDEX: self::minimumBlockLength=%d - EXIT!', self::$minimumBlockLength));
		return self::$minimumBlockLength;
	}

	/**
	 * Determines whether the EOF has been reached
	 *
	 * @return	$isEndOfFileReached		Whether the EOF has been reached
	 * @throws	UnsupportedOperationException	If this method is called
	 */
	public function isEndOfFileReached () {
		throw new UnsupportedOperationException(array($this, __FUNCTION__), self::EXCEPTION_UNSPPORTED_OPERATION);
	}

	/**
	 * Initializes counter for valid entries, arrays for damaged entries and
	 * an array for gap seek positions. If you call this method on your own,
	 * please re-analyze the file structure. So you are better to call
	 * analyzeFileStructure() instead of this method.
	 *
	 * @return	void
	 * @throws	UnsupportedOperationException	This method is not (and maybe never will be) supported
	 */
	public function initCountersGapsArray () {
		throw new UnsupportedOperationException(array($this, __FUNCTION__, $this->getIteratorInstance()->getPointerInstance()), self::EXCEPTION_UNSPPORTED_OPERATION);
	}

	/**
	 * Getter for header size
	 *
	 * @return	$totalEntries	Size of file header
	 * @throws	UnsupportedOperationException	This method is not (and maybe never will be) supported
	 */
	public final function getHeaderSize () {
		throw new UnsupportedOperationException(array($this, __FUNCTION__, $this->getIteratorInstance()->getPointerInstance()), self::EXCEPTION_UNSPPORTED_OPERATION);
	}

	/**
	 * Setter for header size
	 *
	 * @param	$headerSize		Size of file header
	 * @return	void
	 * @throws	UnsupportedOperationException	This method is not (and maybe never will be) supported
	 */
	public final function setHeaderSize (int $headerSize) {
		throw new UnsupportedOperationException(array($this, __FUNCTION__, $this->getIteratorInstance()->getPointerInstance()), self::EXCEPTION_UNSPPORTED_OPERATION);
	}

	/**
	 * Getter for header array
	 *
	 * @return	$totalEntries	Size of file header
	 * @throws	UnsupportedOperationException	This method is not (and maybe never will be) supported
	 */
	public final function getHeader () {
		throw new UnsupportedOperationException(array($this, __FUNCTION__, $this->getIteratorInstance()->getPointerInstance()), self::EXCEPTION_UNSPPORTED_OPERATION);
	}

	/**
	 * Setter for header
	 *
	 * @param	$header		Array for a file header
	 * @return	void
	 * @throws	UnsupportedOperationException	This method is not (and maybe never will be) supported
	 */
	public final function setHeader (array $header) {
		throw new UnsupportedOperationException(array($this, __FUNCTION__, $this->getIteratorInstance()->getPointerInstance()), self::EXCEPTION_UNSPPORTED_OPERATION);
	}

	/**
	 * Updates seekPosition attribute from file to avoid to much access on file.
	 *
	 * @return	void
	 * @throws	UnsupportedOperationException	This method is not (and maybe never will be) supported
	 */
	public function updateSeekPosition () {
		throw new UnsupportedOperationException(array($this, __FUNCTION__, $this->getIteratorInstance()->getPointerInstance()), self::EXCEPTION_UNSPPORTED_OPERATION);
	}

	/**
	 * Getter for total entries
	 *
	 * @return	$totalEntries	Total entries in this file
	 * @throws	UnsupportedOperationException	This method is not (and maybe never will be) supported
	 */
	public final function getCounter () {
		throw new UnsupportedOperationException(array($this, __FUNCTION__, $this->getIteratorInstance()->getPointerInstance()), self::EXCEPTION_UNSPPORTED_OPERATION);
	}

	/**
	 * "Getter" for file size
	 *
	 * @return	$fileSize	Size of currently loaded file
	 */
	public function getFileSize () {
		// Call iterator's method
		return $this->getIteratorInstance()->getFileSize();
	}

	/**
	 * Writes data at given position
	 *
	 * @param	$seekPosition	Seek position
	 * @param	$data			Data to be written
	 * @param	$flushHeader	Whether to flush the header (default: flush)
	 * @return	void
	 * @throws	UnsupportedOperationException	This method is not (and maybe never will be) supported
	 */
	public function writeData (int $seekPosition, string $data, bool $flushHeader = true) {
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput(sprintf('seekPosition=%s,data[]=%s,flushHeader=%d - CALLED!', $seekPosition, gettype($data), intval($flushHeader)));
		throw new UnsupportedOperationException(array($this, __FUNCTION__, $this->getIteratorInstance()->getPointerInstance()), self::EXCEPTION_UNSPPORTED_OPERATION);
	}

	/**
	 * Writes given value to the file and returns a hash and gap position for it
	 *
	 * @param	$groupId	Group identifier
	 * @param	$value		Value to be added to the stack
	 * @return	$data		Hash and gap position
	 * @throws	UnsupportedOperationException	If this method is called
	 */
	public function writeValueToFile (string $groupId, $value) {
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput(sprintf('groupId=%s,value[%s]=%s - CALLED!', $groupId, gettype($value), print_r($value, true)));
		throw new UnsupportedOperationException(array($this, __FUNCTION__), self::EXCEPTION_UNSPPORTED_OPERATION);
	}

	/**
	 * Writes given raw data to the file and returns a gap position and length
	 *
	 * @param	$groupId	Group identifier
	 * @param	$hash		Hash from encoded value
	 * @param	$encoded	Encoded value to be written to the file
	 * @return	$data		Gap position and length of the raw data
	 */
	public function writeDataToFreeGap (string $groupId, string $hash, string $encoded) {
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugOutput(sprintf('groupId=%s,hash=%s,encoded()=%d - CALLED!', $groupId, $hash, strlen($encoded)));
		throw new UnsupportedOperationException(array($this, __FUNCTION__), self::EXCEPTION_UNSPPORTED_OPERATION);
	}

}