package alerts

import (
	"sync"
	"time"

	"github.com/pocketbase/dbx"
	"github.com/pocketbase/pocketbase/core"
	"github.com/pocketbase/pocketbase/tools/store"
)

// CachedAlertData represents the relevant fields of an alert record for status checking and updates.
type CachedAlertData struct {
	Id           string
	SystemID     string
	UserID       string
	Name         string
	Value        float64
	Triggered    bool
	Min          uint8
	PendingSince time.Time
	// Immutable after publication; decoded only when the alert record changes.
	MonitorStates      map[string]string
	MonitorStatesValid bool
	// Created   types.DateTime
}

func (a *CachedAlertData) PopulateFromRecord(record *core.Record) {
	a.Id = record.Id
	a.SystemID = record.GetString("system")
	a.UserID = record.GetString("user")
	a.Name = record.GetString("name")
	a.Value = record.GetFloat("value")
	a.Triggered = record.GetBool("triggered")
	a.Min = uint8(record.GetInt("min"))
	a.PendingSince = record.GetDateTime("pending_since").Time()
	if a.Name == alertNameNetworkMonitorLoss {
		var state networkMonitorAlertState
		a.MonitorStatesValid = record.UnmarshalJSONField("state", &state) == nil
		a.MonitorStates = state.Monitors
	}
	// a.Created = record.GetDateTime("created")
}

// AlertsCache provides an in-memory cache for system alerts.
type AlertsCache struct {
	// Serialize lazy loads with updates so a late load cannot replace newer state.
	loadMu    sync.Mutex
	app       core.App
	store     *store.Store[string, *store.Store[string, CachedAlertData]]
	populated bool
}

// NewAlertsCache creates a new instance of SystemAlertsCache.
func NewAlertsCache(app core.App) *AlertsCache {
	c := AlertsCache{
		app:   app,
		store: store.New(map[string]*store.Store[string, CachedAlertData]{}),
	}
	return c.bindEvents()
}

// bindEvents sets up event listeners to keep the cache in sync with database changes.
func (c *AlertsCache) bindEvents() *AlertsCache {
	c.app.OnRecordAfterUpdateSuccess("alerts").BindFunc(func(e *core.RecordEvent) error {
		// Remove the previous binding if the system changed (only possible through superuser or internal saves).
		if original := e.Record.Original(); original.GetString("system") != e.Record.GetString("system") {
			c.Delete(original)
		}
		c.Update(e.Record)
		return e.Next()
	})
	c.app.OnRecordAfterDeleteSuccess("alerts").BindFunc(func(e *core.RecordEvent) error {
		c.Delete(e.Record)
		return e.Next()
	})
	c.app.OnRecordAfterCreateSuccess("alerts").BindFunc(func(e *core.RecordEvent) error {
		c.Update(e.Record)
		return e.Next()
	})
	return c
}

// PopulateFromDB clears current entries and loads all alerts from the database into the cache.
func (c *AlertsCache) PopulateFromDB(force bool) error {
	c.loadMu.Lock()
	defer c.loadMu.Unlock()
	if !force && c.populated {
		return nil
	}
	records, err := c.app.FindAllRecords("alerts")
	if err != nil {
		return err
	}
	c.store.RemoveAll()
	for _, record := range records {
		c.update(record)
	}
	c.populated = true
	return nil
}

// Update adds or updates an alert record in the cache.
func (c *AlertsCache) Update(record *core.Record) {
	c.loadMu.Lock()
	defer c.loadMu.Unlock()
	c.update(record)
}

func (c *AlertsCache) update(record *core.Record) {
	systemID := record.GetString("system")
	if systemID == "" {
		return
	}
	systemStore, ok := c.store.GetOk(systemID)
	if !ok {
		systemStore = store.New(map[string]CachedAlertData{})
		c.store.Set(systemID, systemStore)
	}
	var ca CachedAlertData
	ca.PopulateFromRecord(record)
	systemStore.Set(record.Id, ca)
}

// Delete removes an alert record from the cache.
func (c *AlertsCache) Delete(record *core.Record) {
	c.loadMu.Lock()
	defer c.loadMu.Unlock()
	systemID := record.GetString("system")
	if systemID == "" {
		return
	}
	if systemStore, ok := c.store.GetOk(systemID); ok {
		systemStore.Remove(record.Id)
	}
}

// GetSystemAlerts returns all alerts for the specified system, lazy-loading if necessary.
func (c *AlertsCache) GetSystemAlerts(systemID string) []CachedAlertData {
	systemStore, ok := c.store.GetOk(systemID)
	if !ok {
		c.loadMu.Lock()
		defer c.loadMu.Unlock()
		systemStore, ok = c.store.GetOk(systemID)
		if !ok {
			// Populate cache for this system
			records, err := c.app.FindAllRecords("alerts", dbx.NewExp("system={:system}", dbx.Params{"system": systemID}))
			if err != nil {
				return nil
			}
			systemStore = store.New(map[string]CachedAlertData{})
			for _, record := range records {
				var ca CachedAlertData
				ca.PopulateFromRecord(record)
				systemStore.Set(record.Id, ca)
			}
			c.store.Set(systemID, systemStore)
		}
	}
	all := systemStore.GetAll()
	alerts := make([]CachedAlertData, 0, len(all))
	for _, alert := range all {
		alerts = append(alerts, alert)
	}
	return alerts
}

// GetAlert returns a specific alert by its ID from the cache.
func (c *AlertsCache) GetAlert(systemID, alertID string) (CachedAlertData, bool) {
	if systemStore, ok := c.store.GetOk(systemID); ok {
		return systemStore.GetOk(alertID)
	}
	return CachedAlertData{}, false
}

// GetAlertsByName returns all alerts of a specific type for the specified system.
func (c *AlertsCache) GetAlertsByName(systemID, alertName string) []CachedAlertData {
	allAlerts := c.GetSystemAlerts(systemID)
	var alerts []CachedAlertData
	for _, record := range allAlerts {
		if record.Name == alertName {
			alerts = append(alerts, record)
		}
	}
	return alerts
}

// GetAlertsExcludingNames returns all alerts for the specified system excluding the given types.
func (c *AlertsCache) GetAlertsExcludingNames(systemID string, excludedNames ...string) []CachedAlertData {
	excludeMap := make(map[string]struct{})
	for _, name := range excludedNames {
		excludeMap[name] = struct{}{}
	}
	allAlerts := c.GetSystemAlerts(systemID)
	var alerts []CachedAlertData
	for _, record := range allAlerts {
		if _, excluded := excludeMap[record.Name]; !excluded {
			alerts = append(alerts, record)
		}
	}
	return alerts
}

// Refresh returns the latest cached copy for an alert snapshot if it still exists.
func (c *AlertsCache) Refresh(alert CachedAlertData) (CachedAlertData, bool) {
	if alert.Id == "" {
		return CachedAlertData{}, false
	}
	return c.GetAlert(alert.SystemID, alert.Id)
}