/*
* Copyright (c) 2013-2022, The PurpleI2P Project
*
* This file is part of Purple i2pd project and licensed under BSD3
*
* See full license text in LICENSE file at top of project tree
*/

#include <string.h>
#include <openssl/evp.h>
#include <openssl/ssl.h>
#include "Crypto.h"
#include "FS.h"
#include "Log.h"
#include "Family.h"
#include "Config.h"

namespace i2p {
    namespace data {
        Families::Families() {
        }

        Families::~Families() {
        }

        void Families::LoadCertificate(const std::string &filename) {
            SSL_CTX *ctx = SSL_CTX_new(TLS_method());
            int ret = SSL_CTX_use_certificate_file(ctx, filename.c_str(), SSL_FILETYPE_PEM);
            if (ret) {
                SSL *ssl = SSL_new(ctx);
                X509 *cert = SSL_get_certificate(ssl);
                if (cert) {
                    std::shared_ptr<i2p::crypto::Verifier> verifier;
                    // extract issuer name
                    char name[100];
                    X509_NAME_oneline(X509_get_issuer_name(cert), name, 100);
                    char *cn = strstr(name, "CN=");
                    if (cn) {
                        cn += 3;
                        char *family = strstr(cn, ".family");
                        if (family) family[0] = 0;
                    }
                    auto pkey = X509_get_pubkey(cert);
                    int keyType = EVP_PKEY_base_id(pkey);
                    switch (keyType) {
                        case EVP_PKEY_DSA:
                            // TODO:
                            break;
                        case EVP_PKEY_EC: {
                            EC_KEY *ecKey = EVP_PKEY_get1_EC_KEY(pkey);
                            if (ecKey) {
                                auto group = EC_KEY_get0_group(ecKey);
                                if (group) {
                                    int curve = EC_GROUP_get_curve_name(group);
                                    if (curve == NID_X9_62_prime256v1) {
                                        uint8_t signingKey[64];
                                        BIGNUM *x = BN_new(), *y = BN_new();
                                        EC_POINT_get_affine_coordinates_GFp(group,
                                                                            EC_KEY_get0_public_key(ecKey), x, y, NULL);
                                        i2p::crypto::bn2buf(x, signingKey, 32);
                                        i2p::crypto::bn2buf(y, signingKey + 32, 32);
                                        BN_free(x);
                                        BN_free(y);
                                        verifier = std::make_shared<i2p::crypto::ECDSAP256Verifier>();
                                        verifier->SetPublicKey(signingKey);
                                    } else
                                        LogPrint(eLogWarning, "Family: elliptic curve ", curve, " is not supported");
                                }
                                EC_KEY_free(ecKey);
                            }
                            break;
                        }
                        default:
                            LogPrint(eLogWarning, "Family: Certificate key type ", keyType, " is not supported");
                    }
                    EVP_PKEY_free(pkey);
                    if (verifier && cn)
                        m_SigningKeys.emplace(cn, std::make_pair(verifier, m_SigningKeys.size() + 1));
                }
                SSL_free(ssl);
            } else
                LogPrint(eLogError, "Family: Can't open certificate file ", filename);
            SSL_CTX_free(ctx);
        }

        void Families::LoadCertificates() {
            std::string certDir = i2p::fs::GetCertsDir() + i2p::fs::dirSep + "family";

            std::vector<std::string> files;
            int numCertificates = 0;

            if (!i2p::fs::ReadDir(certDir, files)) {
                LogPrint(eLogWarning, "Family: Can't load family certificates from ", certDir);
                return;
            }

            for (const std::string &file: files) {
                if (file.compare(file.size() - 4, 4, ".crt") != 0) {
                    LogPrint(eLogWarning, "Family: ignoring file ", file);
                    continue;
                }
                LoadCertificate(file);
                numCertificates++;
            }
            LogPrint(eLogInfo, "Family: ", numCertificates, " certificates loaded");
        }

        bool Families::VerifyFamily(const std::string &family, const IdentHash &ident,
                                    const char *signature, const char *key) const {
            uint8_t buf[100], signatureBuf[64];
            size_t len = family.length(), signatureLen = strlen(signature);
            if (len + 32 > 100) {
                LogPrint(eLogError, "Family: ", family, " is too long");
                return false;
            }

            memcpy(buf, family.c_str(), len);
            memcpy(buf + len, (const uint8_t *) ident, 32);
            len += 32;
            Base64ToByteStream(signature, signatureLen, signatureBuf, 64);
            auto it = m_SigningKeys.find(family);
            if (it != m_SigningKeys.end())
                return it->second.first->Verify(buf, len, signatureBuf);
            // TODO: process key
            return true;
        }

        FamilyID Families::GetFamilyID(const std::string &family) const {
            auto it = m_SigningKeys.find(family);
            if (it != m_SigningKeys.end())
                return it->second.second;
            return 0;
        }

        std::string CreateFamilySignature(const std::string &family, const IdentHash &ident) {
            auto filename = i2p::fs::DataDirPath("family", (family + ".key"));
            std::string sig;
            SSL_CTX *ctx = SSL_CTX_new(TLS_method());
            int ret = SSL_CTX_use_PrivateKey_file(ctx, filename.c_str(), SSL_FILETYPE_PEM);
            if (ret) {
                SSL *ssl = SSL_new(ctx);
                EVP_PKEY *pkey = SSL_get_privatekey(ssl);
                EC_KEY *ecKey = EVP_PKEY_get1_EC_KEY(pkey);
                if (ecKey) {
                    auto group = EC_KEY_get0_group(ecKey);
                    if (group) {
                        int curve = EC_GROUP_get_curve_name(group);
                        if (curve == NID_X9_62_prime256v1) {
                            uint8_t signingPrivateKey[32], buf[50], signature[64];
                            i2p::crypto::bn2buf(EC_KEY_get0_private_key(ecKey), signingPrivateKey, 32);
                            i2p::crypto::ECDSAP256Signer signer(signingPrivateKey);
                            size_t len = family.length();
                            memcpy(buf, family.c_str(), len);
                            memcpy(buf + len, (const uint8_t *) ident, 32);
                            len += 32;
                            signer.Sign(buf, len, signature);
                            len = Base64EncodingBufferSize(64);
                            char *b64 = new char[len + 1];
                            len = ByteStreamToBase64(signature, 64, b64, len);
                            b64[len] = 0;
                            sig = b64;
                            delete[] b64;
                        } else
                            LogPrint(eLogWarning, "Family: elliptic curve ", curve, " is not supported");
                    }
                }
                SSL_free(ssl);
            } else
                LogPrint(eLogError, "Family: Can't open keys file: ", filename);
            SSL_CTX_free(ctx);
            return sig;
        }
    }
}