/*
Source File : DecryptionHelper.h


Copyright 2016 Gal Kahana PDFWriter

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.


*/
#pragma once

#include "EStatusCode.h"
#include "XCryptor.h"

#include <string>

class PDFParser;
class IByteReader;
class PDFStreamInput;
class PDFObject;

class DecryptionHelper {

public:
	DecryptionHelper(void);
	virtual ~DecryptionHelper(void);


	/*
		Setup will fail for unsupported decryption options (will not fail for failing to authenticate!).
		Checks password so later can ask DidFailPasswordVerification and DidSucceedOwnerPasswordVerification to verify authentication. 
	*/
	PDFHummus::EStatusCode Setup(PDFParser* inParser,const std::string& inPassword);

	/*
		Queries.

		1. IsEncrypted means PDF is encrypted
		2. SupportsDecryption means that DecryptionHelper supports the kind of encryption defined in the PDF
		3. CanDecryptDocument means that DecryptionHelper can decrypt document. means decryption is supported, and password is good
		4. DidFailPasswordVerification meams that password verification didnt went through. either decryption not supported, or password no good
		5. DidSucceedOwnerPasswordVerification means that password verification succeeded, and the user has owner priviliges
	*/
	bool IsEncrypted() const;
	bool SupportsDecryption() const;
	bool CanDecryptDocument() const;
	bool DidFailPasswordVerification() const;
	bool DidSucceedOwnerPasswordVerification() const;

	std::string DecryptString(const std::string& inStringToDecrypt);

	void OnObjectStart(long long inObjectID, long long inGenerationNumber);
	void OnObjectEnd(PDFObject* inObject);
	// this should be used by parser to grab a default filter for stream. will return null if a stream-specific filter is to be used, or that there's no encryption expected
	// for this stream
	IByteReader* CreateDefaultDecryptionFilterForStream(PDFStreamInput* inStream, IByteReader* inToWrapStream);

	// use this for creating a decryption filter for a stream that uses a stream-specific crypt filter
	IByteReader* CreateDecryptionFilterForStream(PDFStreamInput* inStream, IByteReader* inToWrapStream, const std::string& inCryptName);

	unsigned int GetLength() const;
	unsigned int GetV() const;
	unsigned int GetRevision() const;
	long long GetP() const;
	bool GetEncryptMetaData() const;
	const ByteList& GetFileIDPart1() const;
	const ByteList& GetO() const;
	const ByteList& GetU() const;
	const ByteList& GetOE() const;
	const ByteList& GetUE() const;
	const ByteList& GetPerms() const;
	const StringToXCryptorMap& GetXcrypts() const;
	XCryptor* GetStreamXcrypt() const;
	XCryptor* GetStringXcrypt() const;

	// Reset after or before usage
	void Reset();

	// client can tell at times to halt encryption, when knowing that parsing content that's not encrypted (in encrypted object stream, for instances)
	void PauseDecryption();
	// use this to flag that a previous pause of encryption may now be released. encryption can continue
	void ReleaseDecryption();

	/*
	IsEncrypting will return true if actually encrypting now. it may be false if encryption was not requested, not supported or that the encrytion
	mechanism is not currently in a state that encrypts (say when writing an encryption dictionary).
	*/
	bool IsDecrypting();

//	void HaltDecryption();
//	void ContinueDecryption();
private:
	PDFParser* mParser;

	// named xcrypts, for V4
	StringToXCryptorMap mXcrypts; 
	// xcrypt to use for streams
	XCryptor* mXcryptStreams;
	// xcrypt to use for strings
	XCryptor* mXcryptStrings;

	bool mIsEncrypted;
	bool mSupportsDecryption;
	int mDecryptionPauseLevel;

	// Generic encryption
	unsigned int mV;
	unsigned int mLength; // mLength is in bytes!
	
	IByteReader* CreateDecryptionReader(IByteReader* inSourceStream,const ByteList& inEncryptionKey, bool inUsingAES);
	XCryptor* GetCryptForStream(PDFStreamInput* inStream);

	// Standard filter specific
	bool mFailedPasswordVerification;
	bool mDidSucceedOwnerPasswordVerification;

	unsigned int mRevision;
	ByteList mO;
	ByteList mU;
	ByteList mOE;
	ByteList mUE;
	ByteList mPerms;
	long long mP;
	bool mEncryptMetaData;
	ByteList mFileIDPart1;

	bool AuthenticateUserPassword(const ByteList& inPassword);
	bool AuthenticateOwnerPassword(const ByteList& inPassword);

	void Release();
};