package yuyuecha

import (
	"crypto/hmac"
	"crypto/md5"
	"crypto/rand"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"strconv"
	"strings"
	"time"
	"unicode"
)

// HashIDCard 将身份证号转为上游要求的身份摘要。
// 规则：已是 32 位 MD5 / 64 位 SHA-256 十六进制则原样小写返回；否则对规范化身份证号做 MD5。
func HashIDCard(idCard string) string {
	id := strings.TrimSpace(idCard)
	if isHexDigest(id, 32) || isHexDigest(id, 64) {
		return strings.ToLower(id)
	}
	// 末位校验码 X 统一大写后再摘要，与授权侧常见落库一致
	sum := md5.Sum([]byte(strings.ToUpper(id)))
	return hex.EncodeToString(sum[:])
}

func isHexDigest(s string, length int) bool {
	if len(s) != length {
		return false
	}
	for _, r := range s {
		if !unicode.Is(unicode.ASCII_Hex_Digit, r) {
			return false
		}
	}
	return true
}

// SignHeaders 按 OpenAPI 规范生成签名请求头
// canonical:
//
//	clientId={id}\ntimestamp={ms}\nnonce={hex}\nmethod={METHOD}\npath={path}\nbodySha256={sha256}
func SignHeaders(clientID, clientSecret, method, path string, body []byte) (map[string]string, error) {
	timestamp := strconv.FormatInt(time.Now().UnixMilli(), 10)
	nonce, err := randomNonce(16)
	if err != nil {
		return nil, fmt.Errorf("生成 nonce 失败: %w", err)
	}

	sum := sha256.Sum256(body)
	bodySHA256 := hex.EncodeToString(sum[:])

	canonical := "clientId=" + clientID +
		"\ntimestamp=" + timestamp +
		"\nnonce=" + nonce +
		"\nmethod=" + method +
		"\npath=" + path +
		"\nbodySha256=" + bodySHA256

	mac := hmac.New(sha256.New, []byte(clientSecret))
	mac.Write([]byte(canonical))
	signature := hex.EncodeToString(mac.Sum(nil))

	return map[string]string{
		"clientId":  clientID,
		"timestamp": timestamp,
		"nonce":     nonce,
		"signature": signature,
	}, nil
}

func randomNonce(nBytes int) (string, error) {
	buf := make([]byte, nBytes)
	if _, err := rand.Read(buf); err != nil {
		return "", err
	}
	return hex.EncodeToString(buf), nil
}