// SPDX-FileCopyrightText: 2023 Francesco Pretto <ceztko@gmail.com>
// SPDX-License-Identifier: LGPL-2.0-or-later OR MPL-2.0

#ifndef PDF_SIGNER_CMS_H
#define PDF_SIGNER_CMS_H

#include <chrono>
#include "PdfSigner.h"

extern "C"
{
    // OpenSSL forward declaration
    struct evp_pkey_st;
    // libxml2 forward declaration
    typedef struct _xmlNode xmlNode;
    typedef xmlNode* xmlNodePtr;
}

namespace PoDoFo
{
    class CmsContext;

    using PdfSigningService = std::function<void(bufferview hashToSign, bool dryrun, charbuff& signedHash)>;
    using PdfSignedHashHandler = std::function<void(bufferview signedhHash, bool dryrun)>;

    enum class PdfSignerCmsFlags : uint32_t
    {
        None = 0,
        ///< When supplying a PdfSigningService, specify if the service
        ///< expects a bare digest (the default), or if should be wrapped
        ///< in a ASN.1 structure with encryption and hashing type (PKCS#1 v1.5
        ///< encapsulation), and the signing service will just perform an
        ///< encryption with private key
        ServiceDoWrapDigest = 1,
        ///< When supplying an external PdfSigningService, specify if
        ///< the service should be called for a dry run
        ServiceDoDryRun = 2,
    };

    struct PODOFO_API PdfSignerCmsParams final
    {
        PdfSignatureType SignatureType = PdfSignatureType::PAdES_B;
        [[deprecated("Encryption should be automatically detected from the public key in the certificate")]]
        PdfSignatureEncryption Encryption = PdfSignatureEncryption::RSA;
        PdfHashingAlgorithm Hashing = PdfHashingAlgorithm::SHA256;
        PdfSigningService SigningService;
        nullable<std::chrono::seconds> SigningTimeUTC;
        PdfSignedHashHandler SignedHashHandler;
        PdfSignerCmsFlags Flags = PdfSignerCmsFlags::None;
    };

    enum class PdfSignatureAttributeFlags : uint32_t
    {
        None = 0,
        ///< The attribute is a signed attribute. By default, it is unsigned
        SignedAttribute = 1,
        ///< The input is interpreted as a raw octet string
        AsOctetString = 2,
    };

    /// This class computes a CMS signature according to RFC 5652
    class PODOFO_API PdfSignerCms : public PdfSigner
    {
        friend class PdfSigningContext;
    public:
        /// Load X.509 certificate and supply a ASN.1 DER encoded private key
        /// @param cert ASN.1 DER encoded X.509 certificate
        /// @param pkey ASN.1 DER encoded private key (PKCS#1 or PKCS#8) formats. It can be empty.
        /// In that case signing can be supplied by a signing service, or
        /// performing a deferred signing
        PdfSignerCms(const bufferview& cert, const bufferview& pkey,
            const PdfSignerCmsParams& parameters = { });

        /// Load a X.509 certificate without supplying a private key
        /// @param cert ASN.1 DER encoded X.509 certificate
        /// @remarks signing can be supplied by a signing service, or performing a deferred signing
        PdfSignerCms(const bufferview& cert, const PdfSignerCmsParams& parameters = { });

        ~PdfSignerCms();

    private:
        /// This is used for deserialization by PdfSigningContext
        PdfSignerCms();

    public:
        void AppendData(const bufferview& data) override;
        void ComputeSignature(charbuff& buffer, bool dryrun) override;
        void FetchIntermediateResult(charbuff& result) override;
        void ComputeSignatureDeferred(const bufferview& processedResult, charbuff& contents, bool dryrun) override;
        void Reset() override;
        std::string GetSignatureFilter() const override;
        std::string GetSignatureSubFilter() const override;
        std::string GetSignatureType() const override;
        bool SkipBufferClear() const override;

        /// Add a signature attribute with given identifier from the input
        /// @param nid the numerical identifier
        /// @param attr the attribute bytes. By default, the bytes are parsed for valid ASN.1 input
        void AddAttribute(const std::string_view& nid, const bufferview& attr, PdfSignatureAttributeFlags flags = PdfSignatureAttributeFlags::None);

        /// Reserve some size in the final signature. It is used in dry-runs to enlarge the signature buffer
        /// @remarks the total reserved size is reset on Reset()
        void ReserveAttributeSize(unsigned attrSize);

    public:
        unsigned GetSignedHashSize() const;

        const PdfSignerCmsParams& GetParameters() const { return m_parameters; }

    private:
        // Called by PdfSigningContext
        void Dump(xmlNodePtr signerElem, std::string& temp);
        void Restore(xmlNodePtr signerElem, charbuff& temp);
    private:
        void ensureEventBasedSigning();
        void ensureDeferredSigning();
        void checkContextInitialized();
        void ensureContextInitialized();
        void resetContext();
        void doSign(const bufferview& input, charbuff& output);
        void tryEnlargeSignatureContents(charbuff& contents);
    private:
        nullable<bool> m_deferredSigning;
        charbuff m_certificate;
        std::unique_ptr<CmsContext> m_cmsContext;
        struct evp_pkey_st* m_privKey;
        PdfSignerCmsParams m_parameters;
        unsigned m_reservedSize;

        // Temporary buffer variables
        // NOTE: Don't clear it in Reset() override
        charbuff m_encryptedHash;
    };
}

ENABLE_BITMASK_OPERATORS(PoDoFo::PdfSignerCmsFlags);
ENABLE_BITMASK_OPERATORS(PoDoFo::PdfSignatureAttributeFlags);

#endif // PDF_SIGNER_CMS_H
