package model

import (
	"bytes"
	"errors"
	"fmt"

	"go.yandata.net/iod/iod/go-trustlog/api/logger"
	"go.yandata.net/iod/iod/go-trustlog/internal/helpers"
)

// Envelope 包装序列化后的数据，包含元信息和报文体。
// 用于 Trustlog 接口类型的序列化和反序列化。
type Envelope struct {
	ProducerID string // 日志提供者ID
	Signature  []byte // 签名（根据客户端密钥与指定算法进行签名，二进制格式）
	Body       []byte // CBOR序列化的报文体
}

// EnvelopeConfig 序列化配置。
type EnvelopeConfig struct {
	Signer Signer // 签名器，用于签名和验签
}

// VerifyConfig 验签配置。
type VerifyConfig struct {
	Signer Signer // 签名器，用于验签
}

// NewEnvelopeConfig 创建Envelope配置。
func NewEnvelopeConfig(signer Signer) EnvelopeConfig {
	log := logger.GetGlobalLogger()
	log.Debug("Creating new EnvelopeConfig",
		"signerType", fmt.Sprintf("%T", signer),
	)
	return EnvelopeConfig{
		Signer: signer,
	}
}

// NewSM2EnvelopeConfig 创建使用SM2签名的Envelope配置。
// 便捷方法，用于快速创建SM2签名器配置。
func NewSM2EnvelopeConfig(privateKey, publicKey []byte) EnvelopeConfig {
	log := logger.GetGlobalLogger()
	log.Debug("Creating new SM2 EnvelopeConfig",
		"privateKeyLength", len(privateKey),
		"publicKeyLength", len(publicKey),
	)
	return EnvelopeConfig{
		Signer: NewSM2Signer(privateKey, publicKey),
	}
}

// NewVerifyConfig 创建验签配置。
func NewVerifyConfig(signer Signer) VerifyConfig {
	log := logger.GetGlobalLogger()
	log.Debug("Creating new VerifyConfig",
		"signerType", fmt.Sprintf("%T", signer),
	)
	return VerifyConfig{
		Signer: signer,
	}
}

// NewSM2VerifyConfig 创建使用SM2签名的验签配置。
// 便捷方法，用于快速创建SM2签名器验签配置。
// 注意：验签只需要公钥，但SM2Signer需要同时提供私钥和公钥（私钥可以为空）。
func NewSM2VerifyConfig(publicKey []byte) VerifyConfig {
	return VerifyConfig{
		Signer: NewSM2Signer(nil, publicKey),
	}
}

//
// ===== Envelope 序列化/反序列化 =====
//

// MarshalEnvelope 将 Envelope 序列化为 TLV 格式（Varint长度编码）。
// 格式：[字段1长度][字段1值:producerID][字段2长度][字段2值:签名][字段3长度][字段3值:CBOR报文体]。
func MarshalEnvelope(env *Envelope) ([]byte, error) {
	log := logger.GetGlobalLogger()
	log.Debug("Marshaling envelope to TLV format")
	if env == nil {
		log.Error("Envelope is nil")
		return nil, errors.New("envelope cannot be nil")
	}

	buf := new(bytes.Buffer)
	writer := helpers.NewTLVWriter(buf)

	log.Debug("Writing producerID to TLV",
		"producerID", env.ProducerID,
	)
	if err := writer.WriteStringField(env.ProducerID); err != nil {
		log.Error("Failed to write producerID",
			"error", err,
			"producerID", env.ProducerID,
		)
		return nil, fmt.Errorf("failed to write producerID: %w", err)
	}

	log.Debug("Writing signature to TLV",
		"signatureLength", len(env.Signature),
	)
	if err := writer.WriteField(env.Signature); err != nil {
		log.Error("Failed to write signature",
			"error", err,
			"signatureLength", len(env.Signature),
		)
		return nil, fmt.Errorf("failed to write signature: %w", err)
	}

	log.Debug("Writing body to TLV",
		"bodyLength", len(env.Body),
	)
	if err := writer.WriteField(env.Body); err != nil {
		log.Error("Failed to write body",
			"error", err,
			"bodyLength", len(env.Body),
		)
		return nil, fmt.Errorf("failed to write body: %w", err)
	}

	result := buf.Bytes()
	log.Debug("Envelope marshaled successfully",
		"producerID", env.ProducerID,
		"totalLength", len(result),
	)
	return result, nil
}

// UnmarshalEnvelope 完整反序列化：读取所有字段。
// 解析完整的Envelope结构，包括所有元数据和Body。
// 为了向后兼容，如果遇到旧格式（包含原hash字段），会自动跳过该字段。
func UnmarshalEnvelope(data []byte) (*Envelope, error) {
	log := logger.GetGlobalLogger()
	log.Debug("Unmarshaling envelope from TLV format",
		"dataLength", len(data),
	)
	if len(data) == 0 {
		log.Error("Data is empty")
		return nil, errors.New("data is empty")
	}

	r := bytes.NewReader(data)
	reader := helpers.NewTLVReader(r)

	log.Debug("Reading producerID from TLV")
	producerID, err := reader.ReadStringField()
	if err != nil {
		log.Error("Failed to read producerID",
			"error", err,
		)
		return nil, fmt.Errorf("failed to read producerID: %w", err)
	}
	log.Debug("ProducerID read successfully",
		"producerID", producerID,
	)

	// 读取第一个字段（可能是原hash或签名）
	log.Debug("Reading field 1 from TLV")
	field1, err := reader.ReadField()
	if err != nil {
		log.Error("Failed to read field 1",
			"error", err,
		)
		return nil, fmt.Errorf("failed to read field 1: %w", err)
	}
	log.Debug("Field 1 read successfully",
		"field1Length", len(field1),
	)

	// 读取第二个字段（可能是签名或body）
	log.Debug("Reading field 2 from TLV")
	field2, err := reader.ReadField()
	if err != nil {
		log.Error("Failed to read field 2",
			"error", err,
		)
		return nil, fmt.Errorf("failed to read field 2: %w", err)
	}
	log.Debug("Field 2 read successfully",
		"field2Length", len(field2),
	)

	// 尝试读取第三个字段来判断格式
	log.Debug("Attempting to read field 3 to determine format")
	field3, err := reader.ReadField()
	if err == nil {
		// 有第三个字段，说明是旧格式：producerID, originalHash, encryptedHash, body
		// field1 = originalHash, field2 = encryptedHash/signature, field3 = body
		log.Debug("Detected old format (with originalHash)",
			"producerID", producerID,
			"signatureLength", len(field2),
			"bodyLength", len(field3),
		)
		return &Envelope{
			ProducerID: producerID,
			Signature:  field2,
			Body:       field3,
		}, nil
	}

	// 没有第三个字段，说明是新格式：producerID, signature, body
	// field1 = signature, field2 = body
	log.Debug("Detected new format (without originalHash)",
		"producerID", producerID,
		"signatureLength", len(field1),
		"bodyLength", len(field2),
	)
	return &Envelope{
		ProducerID: producerID,
		Signature:  field1,
		Body:       field2,
	}, nil
}

//
// ===== 部分反序列化（无需反序列化全部报文） =====
//

// UnmarshalEnvelopeProducerID 部分反序列化：只读取字段1（producerID）。
// 用于快速获取producerID而不解析整个Envelope。
func UnmarshalEnvelopeProducerID(data []byte) (string, error) {
	if len(data) == 0 {
		return "", errors.New("data is empty")
	}

	r := bytes.NewReader(data)
	reader := helpers.NewTLVReader(r)

	producerID, err := reader.ReadStringField()
	if err != nil {
		return "", fmt.Errorf("failed to read producerID: %w", err)
	}

	return producerID, nil
}

// UnmarshalEnvelopeSignature 部分反序列化：读取字段1、2（producerID, 签名）。
// 用于获取签名信息而不解析整个Body。
// 为了向后兼容，如果遇到旧格式（包含原hash字段），会自动跳过该字段。
func UnmarshalEnvelopeSignature(data []byte) (string, []byte, error) {
	if len(data) == 0 {
		return "", nil, errors.New("data is empty")
	}

	r := bytes.NewReader(data)
	reader := helpers.NewTLVReader(r)

	producerID, err := reader.ReadStringField()
	if err != nil {
		return "", nil, fmt.Errorf("failed to read producerID: %w", err)
	}

	// 读取第一个字段（可能是原hash或签名）
	field1, err := reader.ReadField()
	if err != nil {
		return "", nil, fmt.Errorf("failed to read field 1: %w", err)
	}

	// 读取第二个字段（可能是签名或body）
	field2, err := reader.ReadField()
	if err != nil {
		return "", nil, fmt.Errorf("failed to read field 2: %w", err)
	}

	// 尝试读取第三个字段来判断格式
	_, err = reader.ReadField()
	if err == nil {
		// 有第三个字段，说明是旧格式：producerID, originalHash, encryptedHash/signature, body
		// field1 = originalHash, field2 = signature
		return producerID, field2, nil
	}

	// 没有第三个字段，说明是新格式：producerID, signature, body
	// field1 = signature
	return producerID, field1, nil
}

//
// ===== Trustlog 序列化/反序列化 =====
//

// MarshalTrustlog 序列化 Trustlog 为 Envelope 格式。
// Trustlog 实现了 Trustlog 接口，自动提取 producerID 并使用 Canonical CBOR 编码。
func MarshalTrustlog(t Trustlog, config EnvelopeConfig) ([]byte, error) {
	log := logger.GetGlobalLogger()
	log.Debug("Marshaling Trustlog to Envelope format",
		"trustlogType", fmt.Sprintf("%T", t),
	)
	if t == nil {
		log.Error("Trustlog is nil")
		return nil, errors.New("trustlog cannot be nil")
	}

	producerID := t.GetProducerID()
	if producerID == "" {
		log.Error("ProducerID is empty")
		return nil, errors.New("producerID cannot be empty")
	}
	log.Debug("ProducerID extracted",
		"producerID", producerID,
	)

	// 1. 序列化CBOR报文体（使用 Trustlog 的 MarshalBinary，确保使用 Canonical CBOR）
	log.Debug("Marshaling trustlog to CBOR binary")
	bodyCBOR, err := t.MarshalBinary()
	if err != nil {
		log.Error("Failed to marshal trustlog to CBOR",
			"error", err,
			"producerID", producerID,
		)
		return nil, fmt.Errorf("failed to marshal trustlog: %w", err)
	}
	log.Debug("Trustlog marshaled to CBOR successfully",
		"producerID", producerID,
		"bodyLength", len(bodyCBOR),
	)

	// 2. 计算签名
	if config.Signer == nil {
		log.Error("Signer is nil")
		return nil, errors.New("signer is required")
	}
	log.Debug("Signing trustlog body",
		"producerID", producerID,
		"bodyLength", len(bodyCBOR),
	)
	signature, err := config.Signer.Sign(bodyCBOR)
	if err != nil {
		log.Error("Failed to sign trustlog body",
			"error", err,
			"producerID", producerID,
		)
		return nil, fmt.Errorf("failed to sign data: %w", err)
	}
	log.Debug("Trustlog body signed successfully",
		"producerID", producerID,
		"signatureLength", len(signature),
	)

	// 3. 构建Envelope
	env := &Envelope{
		ProducerID: producerID,
		Signature:  signature,
		Body:       bodyCBOR,
	}

	// 4. 序列化为TLV格式
	log.Debug("Marshaling envelope to TLV format",
		"producerID", producerID,
	)
	return MarshalEnvelope(env)
}

// UnmarshalTrustlog 反序列化 Envelope 为 Trustlog。
// 解析Envelope数据并恢复 Trustlog 结构。
func UnmarshalTrustlog(data []byte, t Trustlog) error {
	log := logger.GetGlobalLogger()
	log.Debug("Unmarshaling Envelope to Trustlog",
		"trustlogType", fmt.Sprintf("%T", t),
		"dataLength", len(data),
	)
	if t == nil {
		log.Error("Trustlog is nil")
		return errors.New("trustlog cannot be nil")
	}

	env, err := UnmarshalEnvelope(data)
	if err != nil {
		log.Error("Failed to unmarshal envelope",
			"error", err,
		)
		return err
	}
	log.Debug("Envelope unmarshaled successfully",
		"producerID", env.ProducerID,
		"bodyLength", len(env.Body),
	)

	// 使用 Trustlog 的 UnmarshalBinary 反序列化
	log.Debug("Unmarshaling trustlog body from CBOR",
		"producerID", env.ProducerID,
	)
	if errUnmarshal := t.UnmarshalBinary(env.Body); errUnmarshal != nil {
		log.Error("Failed to unmarshal trustlog body",
			"error", errUnmarshal,
			"producerID", env.ProducerID,
		)
		return fmt.Errorf("failed to unmarshal trustlog body: %w", errUnmarshal)
	}
	log.Debug("Trustlog unmarshaled successfully",
		"producerID", env.ProducerID,
	)
	return nil
}

//
// ===== Operation 序列化/反序列化 =====
//

// MarshalOperation 序列化 Operation 为 Envelope 格式。
func MarshalOperation(op *Operation, config EnvelopeConfig) ([]byte, error) {
	return MarshalTrustlog(op, config)
}

// UnmarshalOperation 反序列化 Envelope 为 Operation。
func UnmarshalOperation(data []byte) (*Operation, error) {
	var op Operation
	if err := UnmarshalTrustlog(data, &op); err != nil {
		return nil, err
	}
	return &op, nil
}

//
// ===== Record 序列化/反序列化 =====
//

// MarshalRecord 序列化 Record 为 Envelope 格式。
func MarshalRecord(record *Record, config EnvelopeConfig) ([]byte, error) {
	return MarshalTrustlog(record, config)
}

// UnmarshalRecord 反序列化 Envelope 为 Record。
func UnmarshalRecord(data []byte) (*Record, error) {
	var record Record
	if err := UnmarshalTrustlog(data, &record); err != nil {
		return nil, err
	}
	return &record, nil
}

//
// ===== 验证 =====
//

// VerifyEnvelope 验证Envelope的完整性（使用EnvelopeConfig）。
// 验证签名是否匹配，确保数据未被篡改。
// 如果验证成功，返回解析后的Envelope结构体指针；如果验证失败，返回错误。
func VerifyEnvelope(data []byte, config EnvelopeConfig) (*Envelope, error) {
	if config.Signer == nil {
		return nil, errors.New("signer is required for verification")
	}

	verifyConfig := VerifyConfig(config)
	return VerifyEnvelopeWithConfig(data, verifyConfig)
}

// VerifyEnvelopeWithConfig 验证Envelope的完整性（使用VerifyConfig）。
// 验证签名是否匹配，确保数据未被篡改。
// 如果验证成功，返回解析后的Envelope结构体指针；如果验证失败，返回错误。
func VerifyEnvelopeWithConfig(data []byte, config VerifyConfig) (*Envelope, error) {
	log := logger.GetGlobalLogger()
	log.Debug("Verifying envelope",
		"dataLength", len(data),
	)
	if config.Signer == nil {
		log.Error("Signer is nil")
		return nil, errors.New("signer is required for verification")
	}

	env, err := UnmarshalEnvelope(data)
	if err != nil {
		log.Error("Failed to unmarshal envelope",
			"error", err,
		)
		return nil, fmt.Errorf("failed to unmarshal envelope: %w", err)
	}
	log.Debug("Envelope unmarshaled for verification",
		"producerID", env.ProducerID,
		"bodyLength", len(env.Body),
		"signatureLength", len(env.Signature),
	)

	// 验证签名
	log.Debug("Verifying signature",
		"producerID", env.ProducerID,
	)
	valid, err := config.Signer.Verify(env.Body, env.Signature)
	if err != nil {
		log.Error("Failed to verify signature",
			"error", err,
			"producerID", env.ProducerID,
		)
		return nil, fmt.Errorf("failed to verify signature: %w", err)
	}

	if !valid {
		log.Warn("Signature verification failed",
			"producerID", env.ProducerID,
		)
		return nil, errors.New("signature verification failed")
	}

	log.Debug("Envelope verified successfully",
		"producerID", env.ProducerID,
	)
	return env, nil
}