package middleware

import (
	"bytes"
	"crypto/hmac"
	"io"
	"strconv"
	"strings"
	"sync"
	"time"

	"affiliate_dash/internal/pkg/openlog"
	"affiliate_dash/internal/pkg/response"

	"github.com/gin-gonic/gin"
)

// SourceOpenAuthConfig 是原上游发货接口鉴权配置，保持 X-Api-Key 兼容。
type SourceOpenAuthConfig struct {
	APIKey      string
	APISecret   string
	SkewSeconds int64
	Debug       bool
}

type sourceNonceStore struct {
	mu   sync.Mutex
	data map[string]int64
}

func newSourceNonceStore() *sourceNonceStore {
	return &sourceNonceStore{data: make(map[string]int64)}
}

func (s *sourceNonceStore) seen(nonce string, now, ttl int64) bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	for key, expiresAt := range s.data {
		if expiresAt < now {
			delete(s.data, key)
		}
	}
	if expiresAt, ok := s.data[nonce]; ok && expiresAt >= now {
		return true
	}
	s.data[nonce] = now + ttl
	return false
}

// SourceOpenAuth 保持现有上游对接签名算法不变：X-Api-Key + 字典序 HMAC。
func SourceOpenAuth(cfg SourceOpenAuthConfig) gin.HandlerFunc {
	if cfg.SkewSeconds <= 0 {
		cfg.SkewSeconds = 300
	}
	store := newSourceNonceStore()
	return func(c *gin.Context) {
		reqID := openlog.EnsureReqID(c)
		c.Set(openlog.CtxDebug, cfg.Debug)
		c.Set(openlog.CtxStart, time.Now())
		c.Header("X-Request-Id", reqID)

		if cfg.APIKey == "" || cfg.APISecret == "" {
			response.ServerError(c, "服务端未配置 OPEN_API_KEY / OPEN_API_SECRET")
			c.Abort()
			return
		}
		apiKey := c.GetHeader("X-Api-Key")
		timestamp := c.GetHeader("X-Timestamp")
		nonce := c.GetHeader("X-Nonce")
		sign := c.GetHeader("X-Sign")
		if apiKey == "" || timestamp == "" || nonce == "" || sign == "" {
			response.Unauthorized(c, "缺少鉴权头：需要 X-Api-Key、X-Timestamp、X-Nonce、X-Sign")
			c.Abort()
			return
		}
		if apiKey != cfg.APIKey {
			response.Unauthorized(c, "无效的 API Key")
			c.Abort()
			return
		}
		if len(nonce) < 8 || len(nonce) > 64 {
			response.Unauthorized(c, "X-Nonce 长度需在 8~64 之间")
			c.Abort()
			return
		}
		ts, err := strconv.ParseInt(timestamp, 10, 64)
		if err != nil || abs64(time.Now().Unix()-ts) > cfg.SkewSeconds {
			response.Unauthorized(c, "请求已过期或 X-Timestamp 格式错误")
			c.Abort()
			return
		}

		bodyBytes, err := io.ReadAll(c.Request.Body)
		if err != nil {
			response.BadRequest(c, "读取请求体失败")
			c.Abort()
			return
		}
		c.Request.Body = io.NopCloser(bytes.NewBuffer(bodyBytes))

		if store.seen(apiKey+":"+nonce, time.Now().Unix(), cfg.SkewSeconds) {
			response.Unauthorized(c, "重复的 X-Nonce（请勿重放请求）")
			c.Abort()
			return
		}
		expected := BuildOpenSign(apiKey, cfg.APISecret, timestamp, nonce, c.Request.Method, c.Request.URL.Path, string(bodyBytes))
		if !hmac.Equal([]byte(strings.ToLower(sign)), []byte(expected)) {
			response.Unauthorized(c, "签名校验失败")
			c.Abort()
			return
		}
		c.Next()
	}
}