package monitor

import (
	"context"
	"crypto/tls"
	"fmt"
	"go-upkeep/internal/alert"
	"go-upkeep/internal/models"
	"go-upkeep/internal/store"
	"net"
	"net/http"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/miekg/dns"
	probing "github.com/prometheus-community/pro-bing"
)

// --- LOGGING ---
var (
	LogStore []string
	LogMutex sync.RWMutex
)

func AddLog(msg string) {
	LogMutex.Lock()
	defer LogMutex.Unlock()
	ts := time.Now().Format("15:04:05")
	entry := fmt.Sprintf("[%s] %s", ts, msg)
	LogStore = append([]string{entry}, LogStore...)
	if len(LogStore) > 100 {
		LogStore = LogStore[:100]
	}
}

func GetLogs() []string {
	LogMutex.RLock()
	defer LogMutex.RUnlock()
	logs := make([]string, len(LogStore))
	copy(logs, LogStore)
	return logs
}

// --- ENGINE ---

var (
	LiveState = make(map[int]models.Site)
	Mutex     sync.RWMutex

	// Global Switch for HA
	isActive    = true
	activeMutex sync.RWMutex

	insecureSkipVerify bool

	db store.Store

	strictClient = &http.Client{
		Transport: &http.Transport{TLSClientConfig: &tls.Config{InsecureSkipVerify: false}},
	}
	insecureClient = &http.Client{
		Transport: &http.Transport{TLSClientConfig: &tls.Config{InsecureSkipVerify: true}},
	}
)

func SetInsecureSkipVerify(skip bool) {
	insecureSkipVerify = skip
}

func SetEngineActive(active bool) {
	activeMutex.Lock()
	defer activeMutex.Unlock()
	if isActive != active {
		isActive = active
		status := "RESUMED (Active)"
		if !active {
			status = "PAUSED (Passive)"
		}
		AddLog(fmt.Sprintf("Engine %s", status))
	}
}

func IsEngineActive() bool {
	activeMutex.RLock()
	defer activeMutex.RUnlock()
	return isActive
}

func RecordHeartbeat(token string) bool {
	if !IsEngineActive() {
		return false
	} // Only Leader accepts Push

	Mutex.Lock()
	defer Mutex.Unlock()
	var targetID int = -1
	for id, s := range LiveState {
		if s.Type == "push" && s.Token == token {
			targetID = id
			break
		}
	}
	if targetID == -1 {
		return false
	}

	site := LiveState[targetID]
	site.LastCheck = time.Now()
	wasDown := site.Status == "DOWN"
	site.Status = "UP"
	site.FailureCount = 0
	site.Latency = 0
	LiveState[targetID] = site

	if wasDown {
		AddLog(fmt.Sprintf("Push Monitor '%s' recovered", site.Name))
		triggerAlert(site.AlertID, "✅ RECOVERY", fmt.Sprintf("Push Monitor '%s' is receiving heartbeats.", site.Name))
	}
	return true
}

func StartEngine(s store.Store) {
	db = s
	go func() {
		for {
			sites, err := db.GetSites()
			if err != nil {
				AddLog(fmt.Sprintf("Failed to load sites: %v", err))
				time.Sleep(5 * time.Second)
				continue
			}
			for _, s := range sites {
				Mutex.RLock()
				_, exists := LiveState[s.ID]
				Mutex.RUnlock()
				if !exists {
					Mutex.Lock()
					s.Status = "PENDING"
					if s.Type == "push" {
						s.LastCheck = time.Now()
					}
					LiveState[s.ID] = s
					Mutex.Unlock()
					go monitorRoutine(s.ID)
				}
			}
			time.Sleep(5 * time.Second)
		}
	}()
}

func UpdateSiteConfig(site models.Site) {
	Mutex.Lock()
	defer Mutex.Unlock()
	if s, ok := LiveState[site.ID]; ok {
		s.Name = site.Name
		s.URL = site.URL
		s.Type = site.Type
		s.Interval = site.Interval
		s.AlertID = site.AlertID
		s.CheckSSL = site.CheckSSL
		s.ExpiryThreshold = site.ExpiryThreshold
		s.MaxRetries = site.MaxRetries
		s.Hostname = site.Hostname
		s.Port = site.Port
		s.Timeout = site.Timeout
		s.Method = site.Method
		s.Description = site.Description
		s.ParentID = site.ParentID
		s.AcceptedCodes = site.AcceptedCodes
		s.DNSResolveType = site.DNSResolveType
		s.DNSServer = site.DNSServer
		s.IgnoreTLS = site.IgnoreTLS
		s.Paused = site.Paused
		LiveState[site.ID] = s
	}
}

func RemoveSite(id int) {
	Mutex.Lock()
	delete(LiveState, id)
	Mutex.Unlock()
	RemoveHistory(id)
}

func ToggleSitePause(id int) bool {
	Mutex.Lock()
	defer Mutex.Unlock()
	site, ok := LiveState[id]
	if !ok {
		return false
	}
	site.Paused = !site.Paused
	LiveState[id] = site
	if site.Paused {
		AddLog(fmt.Sprintf("Monitor '%s' paused", site.Name))
	} else {
		AddLog(fmt.Sprintf("Monitor '%s' resumed", site.Name))
	}
	return site.Paused
}

func monitorRoutine(id int) {
	checkByID(id)
	for {
		if !IsEngineActive() {
			time.Sleep(5 * time.Second)
			continue
		}

		Mutex.RLock()
		site, exists := LiveState[id]
		Mutex.RUnlock()
		if !exists {
			return
		}

		if site.Paused {
			time.Sleep(5 * time.Second)
			continue
		}

		interval := site.Interval
		if interval < 5 {
			interval = 5
		}
		time.Sleep(time.Duration(interval) * time.Second)
		checkByID(id)
	}
}

func checkByID(id int) {
	if !IsEngineActive() {
		return
	}

	Mutex.RLock()
	site, exists := LiveState[id]
	Mutex.RUnlock()
	if !exists || site.Paused {
		return
	}
	switch site.Type {
	case "http":
		checkHTTP(site)
	case "push":
		checkPush(site)
	case "ping":
		checkPing(site)
	case "port":
		checkPort(site)
	case "dns":
		checkDNS(site)
	case "group":
		checkGroup(site)
	}
}

func checkPush(site models.Site) {
	deadline := site.LastCheck.Add(time.Duration(site.Interval) * time.Second).Add(5 * time.Second)
	if time.Now().After(deadline) {
		handleStatusChange(site, "DOWN", 0, 0)
	} else {
		if site.Status != "UP" {
			handleStatusChange(site, "UP", 200, 0)
		}
	}
}

func isCodeAccepted(code int, accepted string) bool {
	if accepted == "" {
		return code >= 200 && code < 300
	}
	for _, part := range strings.Split(accepted, ",") {
		part = strings.TrimSpace(part)
		if strings.Contains(part, "-") {
			bounds := strings.SplitN(part, "-", 2)
			lo, err1 := strconv.Atoi(strings.TrimSpace(bounds[0]))
			hi, err2 := strconv.Atoi(strings.TrimSpace(bounds[1]))
			if err1 == nil && err2 == nil && code >= lo && code <= hi {
				return true
			}
		} else {
			if v, err := strconv.Atoi(part); err == nil && code == v {
				return true
			}
		}
	}
	return false
}

func checkHTTP(site models.Site) {
	method := site.Method
	if method == "" {
		method = "GET"
	}

	timeout := siteTimeout(site)
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, method, site.URL, nil)
	if err != nil {
		handleStatusChange(site, "DOWN", 0, 0)
		return
	}

	client := strictClient
	if insecureSkipVerify || site.IgnoreTLS {
		client = insecureClient
	}

	start := time.Now()
	resp, err := client.Do(req)
	latency := time.Since(start)

	rawStatus := "UP"
	rawCode := 0
	var certExpiry time.Time
	hasSSL := false

	if err != nil {
		rawStatus = "DOWN"
	} else {
		defer resp.Body.Close()
		rawCode = resp.StatusCode
		if !isCodeAccepted(rawCode, site.AcceptedCodes) {
			rawStatus = "DOWN"
		}
		if site.CheckSSL && resp.TLS != nil && len(resp.TLS.PeerCertificates) > 0 {
			hasSSL = true
			cert := resp.TLS.PeerCertificates[0]
			certExpiry = cert.NotAfter
			if time.Now().After(cert.NotAfter) {
				rawStatus = "SSL EXP"
			}
		}
	}
	updatedSite := site
	updatedSite.HasSSL = hasSSL
	updatedSite.CertExpiry = certExpiry
	updatedSite.Latency = latency
	updatedSite.LastCheck = time.Now()
	handleStatusChange(updatedSite, rawStatus, rawCode, latency)
}

func handleStatusChange(site models.Site, rawStatus string, code int, latency time.Duration) {
	// Double check we are still leader before alerting
	if !IsEngineActive() {
		return
	}

	newState := site
	newState.StatusCode = code

	if site.Status == "UP" && rawStatus != "UP" {
		newState.FailureCount++
		if newState.FailureCount > site.MaxRetries {
			newState.Status = rawStatus
			newState.FailureCount = site.MaxRetries + 1
			AddLog(fmt.Sprintf("Monitor '%s' confirmed DOWN", site.Name))
		} else {
			AddLog(fmt.Sprintf("Monitor '%s' failed check %d/%d", site.Name, newState.FailureCount, site.MaxRetries))
		}
	} else if rawStatus == "UP" {
		newState.FailureCount = 0
		newState.Status = "UP"
	} else {
		newState.Status = rawStatus
		newState.FailureCount = site.MaxRetries + 1
	}

	if site.Type == "http" && site.CheckSSL && site.HasSSL {
		daysLeft := int(time.Until(site.CertExpiry).Hours() / 24)
		if daysLeft <= site.ExpiryThreshold && !site.SentSSLWarning && rawStatus != "SSL EXP" {
			triggerAlert(site.AlertID, "SSL WARNING", fmt.Sprintf("SSL for '%s' expires in %d days", site.Name, daysLeft))
			newState.SentSSLWarning = true
		} else if daysLeft > site.ExpiryThreshold {
			newState.SentSSLWarning = false
		}
	}

	Mutex.Lock()
	if _, ok := LiveState[site.ID]; ok {
		LiveState[site.ID] = newState
	}
	Mutex.Unlock()

	RecordCheck(site.ID, latency, rawStatus == "UP")

	isBroken := func(s string) bool { return s == "DOWN" || s == "SSL EXP" }
	if !isBroken(site.Status) && isBroken(newState.Status) && newState.Status != "PENDING" {
		msg := fmt.Sprintf("Monitor '%s' is DOWN (%s)", site.Name, rawStatus)
		if site.Type == "push" {
			msg = fmt.Sprintf("Push Monitor '%s' missed heartbeat.", site.Name)
		}
		triggerAlert(site.AlertID, "🚨 ALERT", msg)
	}
	if isBroken(site.Status) && newState.Status == "UP" {
		triggerAlert(site.AlertID, "✅ RECOVERY", fmt.Sprintf("Monitor '%s' is UP", site.Name))
	}
}

func triggerAlert(alertID int, title, message string) {
	if db == nil {
		return
	}
	cfg, err := db.GetAlert(alertID)
	if err != nil {
		return
	}
	provider := alert.GetProvider(cfg)
	if provider != nil {
		go func() { provider.Send(title, message) }()
	}
}

func siteTimeout(site models.Site) time.Duration {
	if site.Timeout > 0 {
		return time.Duration(site.Timeout) * time.Second
	}
	return 5 * time.Second
}

func checkPing(site models.Site) {
	host := site.Hostname
	if host == "" {
		host = site.URL
	}

	pinger, err := probing.NewPinger(host)
	if err != nil {
		handleStatusChange(site, "DOWN", 0, 0)
		AddLog(fmt.Sprintf("Ping '%s' resolve failed: %v", site.Name, err))
		return
	}
	pinger.Count = 1
	pinger.Timeout = siteTimeout(site)
	pinger.SetPrivileged(false)

	start := time.Now()
	err = pinger.Run()
	latency := time.Since(start)

	if err != nil || pinger.Statistics().PacketsRecv == 0 {
		updatedSite := site
		updatedSite.Latency = latency
		updatedSite.LastCheck = time.Now()
		handleStatusChange(updatedSite, "DOWN", 0, latency)
		return
	}

	stats := pinger.Statistics()
	updatedSite := site
	updatedSite.Latency = stats.AvgRtt
	updatedSite.LastCheck = time.Now()
	handleStatusChange(updatedSite, "UP", 0, stats.AvgRtt)
}

func checkPort(site models.Site) {
	host := site.Hostname
	if host == "" {
		host = site.URL
	}
	addr := net.JoinHostPort(host, strconv.Itoa(site.Port))
	timeout := siteTimeout(site)

	start := time.Now()
	conn, err := net.DialTimeout("tcp", addr, timeout)
	latency := time.Since(start)

	updatedSite := site
	updatedSite.Latency = latency
	updatedSite.LastCheck = time.Now()

	if err != nil {
		handleStatusChange(updatedSite, "DOWN", 0, latency)
		return
	}
	conn.Close()
	handleStatusChange(updatedSite, "UP", 0, latency)
}

func checkGroup(site models.Site) {
	Mutex.RLock()
	status := "UP"
	hasChildren := false
	allPaused := true
	for _, child := range LiveState {
		if child.ParentID != site.ID || child.Type == "group" {
			continue
		}
		hasChildren = true
		if !child.Paused {
			allPaused = false
		}
		if child.Paused {
			continue
		}
		if child.Status == "DOWN" || child.Status == "SSL EXP" {
			status = "DOWN"
		} else if child.Status == "PENDING" && status != "DOWN" {
			status = "PENDING"
		}
	}
	Mutex.RUnlock()

	if !hasChildren {
		status = "PENDING"
	}

	Mutex.Lock()
	s := LiveState[site.ID]
	s.Status = status
	if hasChildren && allPaused {
		s.Paused = true
	}
	LiveState[site.ID] = s
	Mutex.Unlock()
}

func checkDNS(site models.Site) {
	host := site.Hostname
	if host == "" {
		host = site.URL
	}

	server := site.DNSServer
	if server == "" {
		server = "1.1.1.1"
	}
	if _, _, err := net.SplitHostPort(server); err != nil {
		server = net.JoinHostPort(server, "53")
	}

	qtype := dns.TypeA
	switch site.DNSResolveType {
	case "AAAA":
		qtype = dns.TypeAAAA
	case "MX":
		qtype = dns.TypeMX
	case "CNAME":
		qtype = dns.TypeCNAME
	case "TXT":
		qtype = dns.TypeTXT
	case "NS":
		qtype = dns.TypeNS
	case "SOA":
		qtype = dns.TypeSOA
	case "SRV":
		qtype = dns.TypeSRV
	case "PTR":
		qtype = dns.TypePTR
	}

	m := new(dns.Msg)
	m.SetQuestion(dns.Fqdn(host), qtype)

	c := new(dns.Client)
	c.Timeout = siteTimeout(site)

	start := time.Now()
	r, rtt, err := c.Exchange(m, server)
	_ = rtt
	latency := time.Since(start)

	updatedSite := site
	updatedSite.Latency = latency
	updatedSite.LastCheck = time.Now()

	if err != nil {
		handleStatusChange(updatedSite, "DOWN", 0, latency)
		return
	}

	if r.Rcode != dns.RcodeSuccess {
		handleStatusChange(updatedSite, "DOWN", r.Rcode, latency)
		return
	}

	handleStatusChange(updatedSite, "UP", 0, latency)
}