package ingest

import (
	"encoding/json"
	"fmt"
	"net"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"git.apinb.com/ops/logs/internal/config"
	"git.apinb.com/ops/logs/internal/impl"
	"git.apinb.com/ops/logs/internal/models"
	"github.com/gosnmp/gosnmp"
)

type Engine struct {
	mu sync.RWMutex

	trapDict    []models.TrapDictionaryEntry
	syslogRules []models.SyslogRule
	trapRules   []models.TrapRule
	shields     []models.TrapShield
}

var Global = &Engine{}

func (e *Engine) Refresh() error {
	var dict []models.TrapDictionaryEntry
	var syslog []models.SyslogRule
	var trap []models.TrapRule
	var shield []models.TrapShield

	if err := impl.DBService.Where("enabled = ?", true).Find(&dict).Error; err != nil {
		return err
	}
	sort.Slice(dict, func(i, j int) bool {
		return len(dict[i].OIDPrefix) > len(dict[j].OIDPrefix)
	})

	if err := impl.DBService.Where("enabled = ?", true).Find(&syslog).Error; err != nil {
		return err
	}
	sort.Slice(syslog, func(i, j int) bool { return syslog[i].Priority > syslog[j].Priority })

	if err := impl.DBService.Where("enabled = ?", true).Find(&trap).Error; err != nil {
		return err
	}
	sort.Slice(trap, func(i, j int) bool { return trap[i].Priority > trap[j].Priority })

	if err := impl.DBService.Where("enabled = ?", true).Find(&shield).Error; err != nil {
		return err
	}

	e.mu.Lock()
	e.trapDict = dict
	e.syslogRules = syslog
	e.trapRules = trap
	e.shields = shield
	e.mu.Unlock()
	return nil
}

func StartRefresher() {
	interval := config.Spec.Ingest.RuleRefreshSecs
	if interval <= 0 {
		interval = 30
	}
	_ = Global.Refresh()
	go func() {
		t := time.NewTicker(time.Duration(interval) * time.Second)
		defer t.Stop()
		for range t.C {
			_ = Global.Refresh()
		}
	}()
}

func normOID(s string) string {
	s = strings.TrimSpace(s)
	return strings.TrimPrefix(s, ".")
}

func (e *Engine) HandleSyslog(addr *net.UDPAddr, payload []byte) {
	parsed := parseSyslogPayload(payload)
	device := parsed.Hostname
	if device == "" {
		device = addr.IP.String()
	}
	detailObj := map[string]interface{}{
		"priority": parsed.Priority,
		"hostname": parsed.Hostname,
		"tag":      parsed.Tag,
		"message":  parsed.Message,
	}
	detailBytes, _ := json.Marshal(detailObj)
	summary := formatSyslogSummary(parsed)
	sev := syslogPriorityToSeverity(parsed.Priority)

	ev := models.LogEvent{
		SourceKind:        "syslog",
		RemoteAddr:        addr.String(),
		RawPayload:        string(payload),
		NormalizedSummary: summary,
		NormalizedDetail:  string(detailBytes),
		DeviceName:        device,
		SeverityCode:      sev,
	}

	e.mu.RLock()
	rules := e.syslogRules
	e.mu.RUnlock()

	var matched *models.SyslogRule
	for i := range rules {
		if syslogRuleMatches(&rules[i], device, parsed.Message, parsed.RawLine) {
			matched = &rules[i]
			break
		}
	}

	if err := impl.DBService.Create(&ev).Error; err != nil {
		return
	}

	if matched == nil {
		return
	}
	labels := map[string]string{
		"source":      "syslog",
		"device":      device,
		"rule_id":     strconv.FormatUint(uint64(matched.ID), 10),
		"rule_name":   matched.Name,
		"remote_addr": addr.String(),
	}
	rawObj := map[string]interface{}{
		"source":       "syslog",
		"received_at":  time.Now().UTC().Format(time.RFC3339),
		"source_ip":    addr.IP.String(),
		"rule_id":      matched.ID,
		"log_entry_id": ev.ID,
		"raw_packet":   string(payload),
		"parsed":       detailObj,
	}
	rawBytes, mErr := json.Marshal(rawObj)
	if mErr != nil {
		return
	}
	body := AlertReceiveBody{
		AlertName:    matched.AlertName,
		Summary:      summary,
		Description:  summary,
		SeverityCode: firstNonEmpty(matched.SeverityCode, sev),
		Value:        parsed.Message,
		Labels:       labels,
		Agent:        "logs-syslog",
		PolicyID:     matched.PolicyID,
		RawData:      rawBytes,
	}
	if err := forwardAlert(body); err == nil {
		_ = impl.DBService.Model(&ev).Update("alert_sent", true).Error
	}
}

func syslogRuleMatches(rule *models.SyslogRule, device, message, rawLine string) bool {
	if strings.TrimSpace(rule.DeviceNameContains) == "" && strings.TrimSpace(rule.KeywordRegex) == "" {
		return false
	}
	deviceName := strings.ToLower(device)
	contains := strings.ToLower(rule.DeviceNameContains)
	if contains != "" && !strings.Contains(deviceName, contains) {
		return false
	}
	if rule.KeywordRegex != "" {
		re, err := regexp.Compile(rule.KeywordRegex)
		if err != nil {
			return false
		}
		if !re.MatchString(message) && !re.MatchString(rawLine) {
			return false
		}
	}
	return true
}

func trapShielded(e *Engine, addr *net.UDPAddr, trapOID string, pkt *gosnmp.SnmpPacket) bool {
	ip := addr.IP
	fp := varbindFingerprint(pkt)
	now := time.Now()
	e.mu.RLock()
	shields := e.shields
	e.mu.RUnlock()
	for i := range shields {
		s := &shields[i]
		if !s.Enabled {
			continue
		}
		if strings.TrimSpace(s.SourceIPCIDR) == "" {
			continue
		}
		if !ipMatchesCIDR(ip, s.SourceIPCIDR) {
			continue
		}
		if p := strings.TrimSpace(s.OIDPrefix); p != "" && !strings.HasPrefix(normOID(trapOID), normOID(p)) {
			continue
		}
		if h := strings.TrimSpace(s.InterfaceHint); h != "" && !strings.Contains(fp, h) {
			continue
		}
		if !inTimeWindows(now, s.TimeWindowsJSON) {
			continue
		}
		return true
	}
	return false
}

func lookupTrapDict(e *Engine, trapOID string) *models.TrapDictionaryEntry {
	t := normOID(trapOID)
	e.mu.RLock()
	dict := e.trapDict
	e.mu.RUnlock()
	for i := range dict {
		if strings.HasPrefix(t, normOID(dict[i].OIDPrefix)) {
			return &dict[i]
		}
	}
	return nil
}

func (e *Engine) HandleTrap(addr *net.UDPAddr, pkt *gosnmp.SnmpPacket) {
	trapOID := extractTrapOID(pkt)
	if trapShielded(e, addr, trapOID, pkt) {
		return
	}

	dict := lookupTrapDict(e, trapOID)
	fp := varbindFingerprint(pkt)
	vbJSON, _ := json.Marshal(trapVarbinds(pkt))

	readable := buildTrapReadable(trapOID, dict, fp)
	detailObj := map[string]interface{}{
		"trap_oid":         trapOID,
		"varbinds":         trapVarbinds(pkt),
		"dict_title":       "",
		"dict_description": "",
		"recovery":         "",
	}
	sev := "warning"
	if dict != nil {
		detailObj["dict_title"] = dict.Title
		detailObj["dict_description"] = dict.Description
		detailObj["recovery"] = dict.RecoveryMessage
		if dict.SeverityCode != "" {
			sev = dict.SeverityCode
		}
	}
	detailBytes, _ := json.Marshal(detailObj)

	ev := models.LogEvent{
		SourceKind:        "snmp_trap",
		RemoteAddr:        addr.String(),
		RawPayload:        fp,
		NormalizedSummary: readable,
		NormalizedDetail:  string(detailBytes),
		DeviceName:        addr.IP.String(),
		SeverityCode:      sev,
		TrapOID:           trapOID,
	}
	if err := impl.DBService.Create(&ev).Error; err != nil {
		return
	}

	e.mu.RLock()
	rules := e.trapRules
	e.mu.RUnlock()

	var matched *models.TrapRule
	for i := range rules {
		if trapRuleMatches(&rules[i], trapOID, fp) {
			matched = &rules[i]
			break
		}
	}

	if matched == nil && dict != nil && strings.TrimSpace(dict.SeverityCode) != "" {
		matched = &models.TrapRule{
			AlertName:    firstNonEmpty(dict.Title, "SNMP Trap"),
			SeverityCode: dict.SeverityCode,
			PolicyID:     0,
		}
	}
	if matched == nil {
		return
	}

	desc := readable
	if dict != nil && dict.RecoveryMessage != "" {
		desc = readable + "\n恢复建议: " + dict.RecoveryMessage
	}
	labels := map[string]string{
		"source":      "snmp_trap",
		"trap_oid":    trapOID,
		"remote_addr": addr.String(),
	}
	if matched.ID != 0 {
		labels["rule_id"] = strconv.FormatUint(uint64(matched.ID), 10)
		labels["rule_name"] = matched.Name
	}
	resolved := map[string]interface{}{}
	if dict != nil {
		resolved["title"] = dict.Title
		resolved["description"] = dict.Description
		resolved["recovery"] = dict.RecoveryMessage
	}
	rawObj := map[string]interface{}{
		"source":       "snmp_trap",
		"received_at":  time.Now().UTC().Format(time.RFC3339),
		"source_ip":    addr.IP.String(),
		"log_entry_id": ev.ID,
		"trap_oid":     trapOID,
		"varbinds":     trapVarbinds(pkt),
		"resolved":     resolved,
		"pdu_summary":  fp,
	}
	if matched.ID != 0 {
		rawObj["rule_id"] = matched.ID
	}
	rawBytes, mErr := json.Marshal(rawObj)
	if mErr != nil {
		return
	}
	body := AlertReceiveBody{
		AlertName:    firstNonEmpty(matched.AlertName, "SNMP Trap"),
		Summary:      readable,
		Description:  desc,
		SeverityCode: firstNonEmpty(matched.SeverityCode, sev),
		Value:        string(vbJSON),
		Labels:       labels,
		Agent:        "logs-trap",
		PolicyID:     matched.PolicyID,
		RawData:      rawBytes,
	}
	if err := forwardAlert(body); err == nil {
		_ = impl.DBService.Model(&ev).Update("alert_sent", true).Error
	}
}

func extractTrapOID(pkt *gosnmp.SnmpPacket) string {
	const snmpTrapOID = "1.3.6.1.6.3.1.1.4.1.0"
	for _, v := range pkt.Variables {
		if v.Name == snmpTrapOID || strings.HasSuffix(v.Name, ".1.3.6.1.6.3.1.1.4.1.0") {
			return oidToString(v.Value)
		}
	}
	for _, v := range pkt.Variables {
		if strings.Contains(v.Name, "1.3.6.1.6.3.1.1.4.1") {
			return oidToString(v.Value)
		}
	}
	return ""
}

func oidToString(val interface{}) string {
	switch x := val.(type) {
	case string:
		return x
	case []byte:
		return string(x)
	default:
		return fmt.Sprintf("%v", x)
	}
}

func trapVarbinds(pkt *gosnmp.SnmpPacket) []map[string]string {
	out := make([]map[string]string, 0, len(pkt.Variables))
	for _, v := range pkt.Variables {
		out = append(out, map[string]string{
			"oid":   v.Name,
			"type":  fmt.Sprintf("%v", v.Type),
			"value": fmtVarbindValue(v),
		})
	}
	return out
}

func buildTrapReadable(trapOID string, dict *models.TrapDictionaryEntry, varbindSummary string) string {
	if dict != nil && dict.Title != "" {
		return dict.Title + " (" + trapOID + ")"
	}
	if trapOID != "" {
		return "Trap " + trapOID
	}
	return truncate(varbindSummary, 256)
}

func trapRuleMatches(rule *models.TrapRule, trapOID, varbindFP string) bool {
	hasOID := strings.TrimSpace(rule.OIDPrefix) != ""
	hasRE := strings.TrimSpace(rule.VarbindMatchRegex) != ""
	if !hasOID && !hasRE {
		return false
	}
	if hasOID && !strings.HasPrefix(normOID(trapOID), normOID(rule.OIDPrefix)) {
		return false
	}
	if rule.VarbindMatchRegex != "" {
		re, err := regexp.Compile(rule.VarbindMatchRegex)
		if err != nil {
			return false
		}
		if !re.MatchString(varbindFP) {
			return false
		}
	}
	return true
}

func firstNonEmpty(a, b string) string {
	if strings.TrimSpace(a) != "" {
		return a
	}
	return b
}