package middleware

import (
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"strings"
	"sync/atomic"
	"time"

	"hfb_sys/backend/internal/logging"

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

var requestIDFallbackCounter atomic.Uint64

const (
	RequestIDHeader  = "X-Request-ID"
	ContextRequestID = "request_id"
)

func RequestID() gin.HandlerFunc {
	return func(c *gin.Context) {
		requestID := c.GetHeader(RequestIDHeader)
		if !validRequestID(requestID) {
			requestID = newRequestID()
		}
		c.Set(ContextRequestID, requestID)
		c.Writer.Header().Set(RequestIDHeader, requestID)
		c.Request = c.Request.WithContext(logging.WithRequestID(c.Request.Context(), requestID))
		c.Next()
	}
}

func GetRequestID(c *gin.Context) string {
	value, ok := c.Get(ContextRequestID)
	if !ok {
		return ""
	}
	requestID, ok := value.(string)
	if !ok {
		return ""
	}
	return requestID
}

func newRequestID() string {
	buf := make([]byte, 16)
	if _, err := rand.Read(buf); err != nil {
		return fmt.Sprintf("%x-%x", time.Now().UnixNano(), requestIDFallbackCounter.Add(1))
	}
	return hex.EncodeToString(buf)
}

func validRequestID(value string) bool {
	if value == "" || len(value) > 64 {
		return false
	}
	return strings.IndexFunc(value, func(char rune) bool {
		return !((char >= 'a' && char <= 'z') ||
			(char >= 'A' && char <= 'Z') ||
			(char >= '0' && char <= '9') ||
			char == '-' || char == '_' || char == '.')
	}) == -1
}