package service

import (
	"crypto/md5"
	"crypto/sha256"
	"encoding/hex"
	"regexp"
	"strings"
)

var (
	reUUID      = regexp.MustCompile(`[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}`)
	reISOTime   = regexp.MustCompile(`\d{4}-\d{2}-\d{2}[T ]\d{2}:\d{2}:\d{2}(\.\d+)?(Z|[+-]\d{2}:?\d{2})?`)
	reUnixMs    = regexp.MustCompile(`\b1[4-9]\d{12}\b`)                     // unix 毫秒级时间戳
	reRequestID = regexp.MustCompile(`\b(req[-_]?|request[-_]?|rid[-_:]?)[-_:]?[0-9a-zA-Z-]{4,}\b`)
	reLongNum   = regexp.MustCompile(`\b\d{4,}\b`)                           // 连续≥4位数字
)

// normalizeErrorMsg 归一化错误消息：剔除易变片段（UUID/时间戳/请求ID/连续数字），
// 使同因不同实例的错误命中同一记忆键。
func normalizeErrorMsg(msg string) string {
	m := msg
	m = reUUID.ReplaceAllString(m, "{uuid}")
	m = reISOTime.ReplaceAllString(m, "{time}")
	m = reUnixMs.ReplaceAllString(m, "{ts}")
	m = reRequestID.ReplaceAllString(m, "{reqid}")
	m = reLongNum.ReplaceAllString(m, "{num}")
	return strings.TrimSpace(m)
}

// buildMemoryKey 构造记忆键 = SHA-256(upstream|error_code|归一化消息)。
// 含失败上游维度：不同上游的同类错误互不串扰。
func buildMemoryKey(upstream, code, msg string) string {
	raw := strings.Join([]string{upstream, code, normalizeErrorMsg(msg)}, "|")
	sum := sha256.Sum256([]byte(raw))
	return hex.EncodeToString(sum[:])
}

// msgFingerprint 归一化消息的 md5（观测/展示用）。
func msgFingerprint(msg string) string {
	sum := md5.Sum([]byte(normalizeErrorMsg(msg)))
	return hex.EncodeToString(sum[:])
}