// sm2.go
package crypt

import (
	"context"
	"fmt"

	"github.com/sashabaranov/go-openai"
	"github.com/sashabaranov/go-openai/jsonschema"
)

type SM2SignTool struct{}

func (t *SM2SignTool) Name() string { return "sm2_sign" }

func (t *SM2SignTool) Description() string {
	return "SM2国密签名实现指南。当文档要求使用国密SM2算法进行签名时使用，包含SM2公私钥加载和签名验证"
}

func (t *SM2SignTool) GetFunctionDefinition() openai.FunctionDefinition {
	return openai.FunctionDefinition{
		Name:        t.Name(),
		Description: t.Description(),
		Parameters: jsonschema.Definition{
			Type: jsonschema.Object,
			Properties: map[string]jsonschema.Definition{
				"encoding": {
					Type:        jsonschema.String,
					Description: "输出编码方式，base64 或 hex，默认 base64",
					Enum:        []string{"base64", "hex"},
				},
			},
			Required: []string{},
		},
	}
}

func (t *SM2SignTool) GetDetail(ctx context.Context, params map[string]string) (string, error) {
	encoding := "base64"
	if v, ok := params["encoding"]; ok && v != "" {
		encoding = v
	}

	return fmt.Sprintf(`
### SM2国密签名完整实现指南

**前置要求**：需要安装 github.com/tjfoc/gmsm

`+"```bash"+`
go get github.com/tjfoc/gmsm
`+"```"+`

`+"```go"+`
package crypto

import (
    "encoding/base64"
    "encoding/hex"
    "github.com/tjfoc/gmsm/sm2"
    "github.com/tjfoc/gmsm/x509"
)

// SignWithSM2 使用SM2私钥签名
func SignWithSM2(data []byte, privateKeyPEM string) (string, error) {
    // 加载SM2私钥
    privateKey, err := x509.ReadPrivateKeyFromPem([]byte(privateKeyPEM), nil)
    if err != nil {
        return "", err
    }
    
    // SM2签名
    signature, err := sm2.Sign(privateKey, data)
    if err != nil {
        return "", err
    }
    
    return base64.StdEncoding.EncodeToString(signature), nil
}

// SignWithSM2AndEncoding 使用SM2私钥签名并指定编码方式
func SignWithSM2AndEncoding(data []byte, privateKeyPEM string, encoding string) (string, error) {
    privateKey, err := x509.ReadPrivateKeyFromPem([]byte(privateKeyPEM), nil)
    if err != nil {
        return "", err
    }
    
    signature, err := sm2.Sign(privateKey, data)
    if err != nil {
        return "", err
    }
    
    if encoding == "hex" {
        return hex.EncodeToString(signature), nil
    }
    return base64.StdEncoding.EncodeToString(signature), nil
}

// VerifySM2 验证SM2签名
func VerifySM2(data []byte, signature []byte, publicKeyPEM string) error {
    publicKey, err := x509.ReadPublicKeyFromPem([]byte(publicKeyPEM))
    if err != nil {
        return err
    }
    
    return sm2.Verify(publicKey, data, signature)
}
`+"```"+`

**注意事项**：
- 确保私钥格式正确（PEM格式）
- SM2签名结果包含R和S两个大整数
- 确认编码方式（Base64还是Hex）
`, encoding), nil
}

func (t *SM2SignTool) Execute(ctx context.Context, params map[string]string) (string, error) {
	return t.GetDetail(ctx, params)
}