package web

import (
	"fmt"
	"hash/crc32"
	"log"
	"strings"
	"sync"
	"time"

	"gitea.dooplex.hu/admin/felhom-controller/internal/backup"
	"gitea.dooplex.hu/admin/felhom-controller/internal/config"
	"gitea.dooplex.hu/admin/felhom-controller/internal/monitor"
	"gitea.dooplex.hu/admin/felhom-controller/internal/settings"
)

// Alert represents a persistent dashboard alert banner.
type Alert struct {
	ID       string   // unique identifier for filtering
	Level    string   // "error", "warning", "info"
	Message  string   // Hungarian display text
	Link     string   // optional link to relevant page
	LinkText string   // link display text
	PageOnly []string // if non-empty, only show on these pages (e.g., ["dashboard", "monitoring"])
	Inline   bool     // if true, rendered by page template inline, not in layout banner
}

// AlertManager generates and stores dashboard alerts from health check results.
// Alerts are state-based (not event-based) — they reflect current system state
// and are regenerated after each health check cycle.
type AlertManager struct {
	mu              sync.RWMutex
	alerts          []Alert
	logger          *log.Logger
	hubPushStatusFn func() HubPushStatusData
	// agentChannelAlert is set/cleared by the channel-health checker (out-of-band from Refresh, which
	// is health-report-driven). nil = channel up. It is prepended in GetAlerts so a dead controller→
	// agent link (disk/storage UI broken) is always visible regardless of the health-report cycle.
	agentChannelAlert *Alert
	// deadAppAlerts (fix-3, CAMPAIGN-3) is set each cycle by the health loop from the deployed-app
	// running-state view (which is NOT in the health report — it comes from the stack manager). Same
	// out-of-band, state-based, self-clearing model as agentChannelAlert: passing an empty slice when
	// every deployed app is running clears the banner with no manual dismissal.
	deadAppAlerts []Alert
	// endpointDriftAlert (R-77) is set/cleared at startup by the local_api drift check. Separate from
	// agentChannelAlert on purpose: drift is usually the CAUSE and "agent unreachable" the SYMPTOM,
	// and during the 2026-07-25 outage only the symptom was visible.
	endpointDriftAlert *Alert
}

// NewAlertManager creates a new AlertManager.
func NewAlertManager(logger *log.Logger) *AlertManager {
	return &AlertManager{
		logger: logger,
	}
}

// SetHubPushStatus sets the hub push status callback for generating hub alerts.
func (am *AlertManager) SetHubPushStatus(fn func() HubPushStatusData) {
	am.mu.Lock()
	am.hubPushStatusFn = fn
	am.mu.Unlock()
}

// SetAgentChannelAlert sets (down=true) or clears (down=false) the controller→agent channel-down
// dashboard banner. Called by the channel-health checker each probe (idempotent). msg is the short
// Hungarian display line.
func (am *AlertManager) SetAgentChannelAlert(down bool, msg string) {
	am.mu.Lock()
	defer am.mu.Unlock()
	if !down {
		am.agentChannelAlert = nil
		return
	}
	am.agentChannelAlert = &Alert{
		ID:       "agent-channel-down",
		Level:    "error",
		Message:  msg,
		Link:     "/settings",
		LinkText: "Beállítások",
	}
}

// SetEndpointDriftAlert sets (drift=true) or clears the local_api endpoint-drift banner (R-77).
//
// It is deliberately a SEPARATE alert from SetAgentChannelAlert: during the 2026-07-25 outage the
// generic "agent unreachable" banner was the ONLY signal, and it looked like a dead agent. The two
// can also be true at once — a drifted endpoint usually CAUSES the channel to be down — so folding
// them together would hide the actionable one behind the symptom.
func (am *AlertManager) SetEndpointDriftAlert(drift bool, msg string) {
	am.mu.Lock()
	defer am.mu.Unlock()
	if !drift {
		am.endpointDriftAlert = nil
		return
	}
	am.endpointDriftAlert = &Alert{
		ID:       "local-api-endpoint-drift",
		Level:    "error",
		Message:  msg,
		Link:     "/settings",
		LinkText: "Beállítások",
	}
}

// DeadApp is a deployed app the health loop found not-running (fix-3). State is the container-state
// string for the display (e.g. "stopped"/"exited").
type DeadApp struct {
	Name        string
	DisplayName string
	State       string
}

// deadAppGroupThreshold: above this many dead apps, collapse to ONE grouped alert (a reboot storm
// with many NAS apps down should not paper the dashboard with a wall of banners — fix-3).
const deadAppGroupThreshold = 3

// buildDeadAppAlerts turns the dead-app list into dashboard alerts (WARN). ≤ threshold → one per app;
// more → a single grouped alert. Pure → unit-tested. Empty list → nil (clears the banner).
func buildDeadAppAlerts(dead []DeadApp) []Alert {
	if len(dead) == 0 {
		return nil
	}
	if len(dead) > deadAppGroupThreshold {
		return []Alert{{
			ID:       "deadapp-group",
			Level:    "warning",
			Message:  fmt.Sprintf("%d telepített alkalmazás nem fut — nézze meg a rendszermonitort", len(dead)),
			Link:     "/monitoring",
			LinkText: "Rendszermonitor",
		}}
	}
	alerts := make([]Alert, 0, len(dead))
	for _, d := range dead {
		name := d.DisplayName
		if name == "" {
			name = d.Name
		}
		msg := "Telepített alkalmazás nem fut: " + name
		if d.State != "" {
			msg += " (" + d.State + ")"
		}
		alerts = append(alerts, Alert{
			ID:       "deadapp-" + simpleHash(d.Name),
			Level:    "warning",
			Message:  msg,
			Link:     "/monitoring",
			LinkText: "Rendszermonitor",
		})
	}
	return alerts
}

// SetDeadAppAlerts stores the current deployed-not-running banner set (fix-3). State-based: called
// each health cycle with the live dead-app list (empty clears it). Included in GetAlerts.
func (am *AlertManager) SetDeadAppAlerts(dead []DeadApp) {
	alerts := buildDeadAppAlerts(dead)
	am.mu.Lock()
	am.deadAppAlerts = alerts
	am.mu.Unlock()
}

// Refresh regenerates alerts from the latest health check report and config state.
// Called after each health check cycle (every 5 minutes) and on storage state changes.
func (am *AlertManager) Refresh(report *monitor.HealthReport, cfg *config.Config, backupMgr *backup.Manager, updateAvailable bool, latestVersion string, storagePaths ...[]settings.StoragePath) {
	var alerts []Alert

	// Disconnected storage alerts (top-level error banners on all pages)
	if len(storagePaths) > 0 {
		for _, sp := range storagePaths[0] {
			if sp.Disconnected {
				label := sp.Label
				if label == "" {
					label = sp.Path
				}
				alerts = append(alerts, Alert{
					ID:       "storage-disconnected-" + simpleHash(sp.Path),
					Level:    "error",
					Message:  fmt.Sprintf("Meghajtó leválasztva: %s (%s)", label, sp.Path),
					Link:     "/settings",
					LinkText: "Beállítások",
				})
			}
		}
	}

	// From health check issues (critical)
	for _, issue := range report.Issues {
		alerts = append(alerts, Alert{
			ID:       "health-" + simpleHash(issue),
			Level:    "error",
			Message:  issue,
			Link:     "/monitoring",
			LinkText: "Rendszermonitor",
		})
	}

	// From health check warnings
	for _, w := range report.Warnings {
		alert := Alert{
			ID:       "health-" + simpleHash(w),
			Level:    "warning",
			Message:  w,
			Link:     "/monitoring",
			LinkText: "Rendszermonitor",
		}
		// Disk-related warnings rendered inline under storage bars, not in top banner
		if strings.Contains(w, "meghajtón") || strings.Contains(w, "adattároló") || strings.Contains(w, "meghajtó") {
			alert.ID = "disk-not-separate"
			alert.PageOnly = []string{"dashboard", "monitoring"}
			alert.Inline = true
		}
		alerts = append(alerts, alert)
	}

	// Hub connection status
	if !cfg.Hub.Enabled || cfg.Hub.URL == "" {
		alerts = append(alerts, Alert{
			ID:       "hub-disabled",
			Level:    "warning",
			Message:  "Hub kapcsolat kikapcsolva — a központi monitoring nem aktív",
			Link:     "/monitoring",
			LinkText: "Rendszermonitor",
		})
	} else if am.hubPushStatusFn != nil {
		ps := am.hubPushStatusFn()
		if ps.LastError != "" && (ps.LastSuccess.IsZero() || time.Since(ps.LastSuccess) > 30*time.Minute) {
			alerts = append(alerts, Alert{
				ID:       "hub-unreachable",
				Level:    "error",
				Message:  fmt.Sprintf("Hub nem elérhető — utolsó hiba: %s", ps.LastError),
				Link:     "/monitoring",
				LinkText: "Rendszermonitor",
			})
		}
	}

	// Backup disabled
	if !cfg.Backup.Enabled {
		alerts = append(alerts, Alert{
			ID:       "backup-disabled",
			Level:    "warning",
			Message:  "A biztonsági mentés nincs bekapcsolva",
			Link:     "/settings",
			LinkText: "Beállítások",
		})
	}

	// Update available
	if updateAvailable && latestVersion != "" {
		alerts = append(alerts, Alert{
			ID:       "update-available",
			Level:    "info",
			Message:  fmt.Sprintf("Új controller verzió elérhető: %s", latestVersion),
			Link:     "/settings",
			LinkText: "Frissítés",
		})
	}

	// Sort: errors first, then warnings, then info
	sortAlerts(alerts)

	am.mu.Lock()
	am.alerts = alerts
	am.mu.Unlock()
}

// GetAlerts returns a copy of the current alerts, optionally excluding specific IDs.
func (am *AlertManager) GetAlerts(excludeIDs ...string) []Alert {
	am.mu.RLock()
	defer am.mu.RUnlock()

	if len(am.alerts) == 0 && am.agentChannelAlert == nil && am.endpointDriftAlert == nil && len(am.deadAppAlerts) == 0 {
		return nil
	}

	exclude := make(map[string]bool, len(excludeIDs))
	for _, id := range excludeIDs {
		exclude[id] = true
	}

	var result []Alert
	// Endpoint drift first: it is the actionable CAUSE, and the channel-down banner below is usually
	// just its symptom. Showing the symptom above the cause is what made the 2026-07-25 outage read
	// as an infrastructure blip for 17.5 h.
	if am.endpointDriftAlert != nil && !exclude[am.endpointDriftAlert.ID] {
		result = append(result, *am.endpointDriftAlert)
	}
	// Channel-down is prepended (highest priority — the agent link being dead breaks disk/storage UI).
	if am.agentChannelAlert != nil && !exclude[am.agentChannelAlert.ID] {
		result = append(result, *am.agentChannelAlert)
	}
	// Dead-app banners (fix-3) — prepended after the channel alert: a deployed app being down is a
	// high-signal state the operator/customer must see immediately.
	for _, a := range am.deadAppAlerts {
		if !exclude[a.ID] {
			result = append(result, a)
		}
	}
	for _, a := range am.alerts {
		if exclude[a.ID] {
			continue
		}
		result = append(result, a)
	}

	// Cap at 5 visible alerts
	if len(result) > 5 {
		overflow := len(result) - 5
		result = result[:5]
		result = append(result, Alert{
			ID:      "overflow",
			Level:   "info",
			Message: fmt.Sprintf("+ %d további figyelmeztetés", overflow),
			Link:    "/monitoring",
		})
	}

	return result
}

// GetInlineAlerts returns alerts marked as Inline for a specific page.
func (am *AlertManager) GetInlineAlerts(page string) []Alert {
	am.mu.RLock()
	defer am.mu.RUnlock()

	var result []Alert
	for _, a := range am.alerts {
		if !a.Inline {
			continue
		}
		if len(a.PageOnly) == 0 {
			result = append(result, a)
			continue
		}
		for _, p := range a.PageOnly {
			if p == page {
				result = append(result, a)
				break
			}
		}
	}
	return result
}

// simpleHash returns a short deterministic hash for deduplication.
func simpleHash(s string) string {
	return fmt.Sprintf("%08x", crc32.ChecksumIEEE([]byte(s)))
}

// sortAlerts sorts alerts by severity: error > warning > info.
func sortAlerts(alerts []Alert) {
	levelOrder := map[string]int{"error": 0, "warning": 1, "info": 2}
	for i := 1; i < len(alerts); i++ {
		for j := i; j > 0 && levelOrder[alerts[j].Level] < levelOrder[alerts[j-1].Level]; j-- {
			alerts[j], alerts[j-1] = alerts[j-1], alerts[j]
		}
	}
}

func countLevel(alerts []Alert, level string) int {
	n := 0
	for _, a := range alerts {
		if a.Level == level {
			n++
		}
	}
	return n
}