gitcitadel-online/internal/nostr/client.go

package nostr

import (
	"context"
	"fmt"
	"sync"
	"time"

	"gitcitadel-online/internal/logger"

	"github.com/nbd-wtf/go-nostr"
)

// Client handles connections to Nostr relays with failover support using go-nostr's SimplePool
type Client struct {
	pool          *nostr.SimplePool
	relays        []string
	mu            sync.RWMutex
	ctx           context.Context
	requestSem    chan struct{} // Semaphore to limit concurrent requests
	maxConcurrent int           // Maximum concurrent requests
}

// NewClient creates a new Nostr client with primary, fallback, and additional fallback relays
// Uses go-nostr's SimplePool for connection management and parallel queries
// Limits concurrent requests to prevent overwhelming relays (default: 5 concurrent requests)
func NewClient(primaryRelay, fallbackRelay, additionalFallback string) *Client {
	ctx := context.Background()
	pool := nostr.NewSimplePool(ctx)

	relays := []string{}
	if primaryRelay != "" {
		relays = append(relays, primaryRelay)
	}
	if fallbackRelay != "" {
		relays = append(relays, fallbackRelay)
	}
	if additionalFallback != "" {
		relays = append(relays, additionalFallback)
	}

	maxConcurrent := 5 // Limit to 5 concurrent requests to avoid overwhelming relays
	return &Client{
		pool:          pool,
		relays:        relays,
		ctx:           ctx,
		requestSem:    make(chan struct{}, maxConcurrent),
		maxConcurrent: maxConcurrent,
	}
}

// Connect connects to the relays (no-op, SimplePool handles connections lazily)
func (c *Client) Connect(ctx context.Context) error {
	// SimplePool handles connections lazily when querying
	return nil
}

// ConnectToRelay connects to a single relay using SimplePool (exported for use by services)
func (c *Client) ConnectToRelay(ctx context.Context, url string) (*nostr.Relay, error) {
	// Use SimplePool's EnsureRelay which handles connection pooling and reuse
	return c.pool.EnsureRelay(url)
}

// FetchEvent fetches a single event by querying all relays in parallel using SimplePool
// Returns the newest event (highest created_at) if multiple events are found
// Rate-limited to prevent overwhelming relays
func (c *Client) FetchEvent(ctx context.Context, filter nostr.Filter) (*nostr.Event, error) {
	return c.FetchEventFromRelays(ctx, filter, c.relays)
}

// FetchEventFromRelays fetches a single event from specific relays
func (c *Client) FetchEventFromRelays(ctx context.Context, filter nostr.Filter, relays []string) (*nostr.Event, error) {
	// Acquire semaphore to limit concurrent requests
	c.requestSem <- struct{}{}
	defer func() { <-c.requestSem }()

	// Create context with 30-second timeout
	queryCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	logger.WithFields(map[string]interface{}{
		"relays":  relays,
		"kinds":   filter.Kinds,
		"authors": filter.Authors,
		"ids":     filter.IDs,
		"tags":    filter.Tags,
	}).Debug("Querying relays using SimplePool")

	// Use SimplePool's SubManyEose to query specified relays in parallel
	// It automatically handles connection pooling, failover, and deduplication
	eventChan := c.pool.SubManyEose(queryCtx, relays, nostr.Filters{filter})

	// Collect all events from all relays
	var allEvents []*nostr.Event
	for incomingEvent := range eventChan {
		if incomingEvent.Event != nil {
			allEvents = append(allEvents, incomingEvent.Event)
			logger.WithFields(map[string]interface{}{
				"relay":      incomingEvent.Relay.URL,
				"event_id":   incomingEvent.Event.ID,
				"created_at": incomingEvent.Event.CreatedAt,
			}).Debug("Received event from relay")
		}
	}

	if len(allEvents) == 0 {
		return nil, fmt.Errorf("event not found from any relay")
	}

	// Find the newest event (highest created_at)
	newest := allEvents[0]
	for _, event := range allEvents[1:] {
		if event.CreatedAt > newest.CreatedAt {
			newest = event
		}
	}

	logger.WithFields(map[string]interface{}{
		"created_at": newest.CreatedAt,
		"total":      len(allEvents),
	}).Debug("Selected newest event from all relays")
	return newest, nil
}

// FetchEvents fetches multiple events by querying all relays in parallel using SimplePool
// Returns deduplicated events, keeping the newest version of each event
// Rate-limited to prevent overwhelming relays
func (c *Client) FetchEvents(ctx context.Context, filter nostr.Filter) ([]*nostr.Event, error) {
	return c.FetchEventsFromRelays(ctx, filter, c.relays)
}

// FetchEventsFromRelays fetches multiple events from specific relays
func (c *Client) FetchEventsFromRelays(ctx context.Context, filter nostr.Filter, relays []string) ([]*nostr.Event, error) {
	return c.FetchEventsBatchFromRelays(ctx, []nostr.Filter{filter}, relays)
}

// FetchEventsBatch fetches multiple events using multiple filters in a single batched query
// This is more efficient than calling FetchEvents multiple times
// Returns deduplicated events, keeping the newest version of each event
// Rate-limited to prevent overwhelming relays
func (c *Client) FetchEventsBatch(ctx context.Context, filters []nostr.Filter) ([]*nostr.Event, error) {
	return c.FetchEventsBatchFromRelays(ctx, filters, c.relays)
}

// FetchEventsBatchFromRelays fetches multiple events from specific relays using multiple filters
func (c *Client) FetchEventsBatchFromRelays(ctx context.Context, filters []nostr.Filter, relays []string) ([]*nostr.Event, error) {
	if len(filters) == 0 {
		return nil, fmt.Errorf("no filters provided")
	}

	// Acquire semaphore to limit concurrent requests
	c.requestSem <- struct{}{}
	defer func() { <-c.requestSem }()

	// Create context with 30-second timeout
	queryCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	logger.WithFields(map[string]interface{}{
		"relays":  relays,
		"filters": len(filters),
	}).Debug("Querying relays using SimplePool with batched filters")

	// Use SimplePool's SubManyEose to query specified relays in parallel with all filters
	// It automatically handles connection pooling, failover, and deduplication
	eventChan := c.pool.SubManyEose(queryCtx, relays, nostr.Filters(filters))

	// Collect all events from all relays, deduplicating by ID and keeping newest
	eventMap := make(map[string]*nostr.Event)
	for incomingEvent := range eventChan {
		if incomingEvent.Event != nil {
			existing, exists := eventMap[incomingEvent.Event.ID]
			if !exists || incomingEvent.Event.CreatedAt > existing.CreatedAt {
				eventMap[incomingEvent.Event.ID] = incomingEvent.Event
				logger.WithFields(map[string]interface{}{
					"relay":      incomingEvent.Relay.URL,
					"event_id":   incomingEvent.Event.ID,
					"created_at": incomingEvent.Event.CreatedAt,
				}).Debug("Received event from relay")
			}
		}
	}

	if len(eventMap) == 0 {
		return nil, fmt.Errorf("no events found from any relay")
	}

	// Convert map to slice
	events := make([]*nostr.Event, 0, len(eventMap))
	for _, event := range eventMap {
		events = append(events, event)
	}

	logger.WithField("events", len(events)).Debug("Returning unique events from all relays")
	return events, nil
}

// FetchEventByID fetches an event by its ID
func (c *Client) FetchEventByID(ctx context.Context, eventID string) (*nostr.Event, error) {
	filter := nostr.Filter{
		IDs: []string{eventID},
	}
	return c.FetchEvent(ctx, filter)
}

// FetchEventsByKind fetches events of a specific kind
func (c *Client) FetchEventsByKind(ctx context.Context, kind int, limit int) ([]*nostr.Event, error) {
	filter := nostr.Filter{
		Kinds: []int{kind},
		Limit: limit,
	}
	return c.FetchEvents(ctx, filter)
}

// Close closes all relay connections in the pool
func (c *Client) Close() {
	// SimplePool manages connections, but we can close individual relays if needed
	// The pool will handle cleanup when context is cancelled
}

// GetRelays returns all configured relay URLs
func (c *Client) GetRelays() []string {
	return c.relays
}

// GetPrimaryRelay returns the primary relay (theforest) for main event fetching
func (c *Client) GetPrimaryRelay() string {
	if len(c.relays) > 0 {
		return c.relays[0]
	}
	return ""
}

// GetProfileRelays returns fallback relays for profile fetching (excludes primary/theforest)
func (c *Client) GetProfileRelays() []string {
	profileRelays := []string{}
	// Skip the first relay (primary/theforest) and use fallback relays
	if len(c.relays) > 1 {
		profileRelays = append(profileRelays, c.relays[1:]...)
	}
	// If no fallback relays, return empty (shouldn't happen, but handle gracefully)
	return profileRelays
}

// GetPool returns the underlying SimplePool (for services that need direct access)
func (c *Client) GetPool() *nostr.SimplePool {
	return c.pool
}

// HealthCheck performs a health check on the relays
func (c *Client) HealthCheck(ctx context.Context, timeout time.Duration) error {
	ctx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()

	// Try to fetch a recent event to test connectivity
	// Note: Using kind 1 for health check (this is a standard kind, not configurable)
	filter := nostr.Filter{
		Kinds: []int{KindNote}, // kind 1 (notes) for testing
		Limit: 1,
	}

	_, err := c.FetchEvents(ctx, filter)
	return err
}

// FetchDeletionEvents fetches kind 5 deletion events for the given authors
// Returns a map of deleted event IDs (event ID -> deletion event)
func (c *Client) FetchDeletionEvents(ctx context.Context, authors []string) (map[string]*nostr.Event, error) {
	if len(authors) == 0 {
		return make(map[string]*nostr.Event), nil
	}

	// Deduplicate authors
	authorSet := make(map[string]bool)
	uniqueAuthors := make([]string, 0, len(authors))
	for _, author := range authors {
		if author != "" && !authorSet[author] {
			authorSet[author] = true
			uniqueAuthors = append(uniqueAuthors, author)
		}
	}

	if len(uniqueAuthors) == 0 {
		return make(map[string]*nostr.Event), nil
	}

	// Fetch kind 5 deletion events from theforest only (primary relay)
	primaryRelay := c.GetPrimaryRelay()
	if primaryRelay == "" {
		return nil, fmt.Errorf("primary relay not configured")
	}

	filter := nostr.Filter{
		Kinds:   []int{KindDelete},
		Authors: uniqueAuthors,
		// No limit - fetch all deletion events
	}

	logger.WithFields(map[string]interface{}{
		"authors": len(uniqueAuthors),
	}).Debug("Fetching deletion events")

	deletionEvents, err := c.FetchEventsFromRelays(ctx, filter, []string{primaryRelay})
	if err != nil {
		return nil, fmt.Errorf("failed to fetch deletion events: %w", err)
	}

	// Parse deletion events - extract event IDs from "e" tags
	deletedEventIDs := make(map[string]*nostr.Event)
	for _, deletionEvent := range deletionEvents {
		// Kind 5 events have "e" tags with the event IDs they're deleting
		for _, tag := range deletionEvent.Tags {
			if len(tag) > 0 && tag[0] == "e" && len(tag) > 1 {
				eventID := tag[1]
				// Keep the newest deletion event if multiple deletions exist
				existing, exists := deletedEventIDs[eventID]
				if !exists || deletionEvent.CreatedAt > existing.CreatedAt {
					deletedEventIDs[eventID] = deletionEvent
				}
			}
		}
	}

	logger.WithFields(map[string]interface{}{
		"deletion_events": len(deletionEvents),
		"deleted_ids":     len(deletedEventIDs),
	}).Debug("Parsed deletion events")

	return deletedEventIDs, nil
}

// FilterDeletedEvents removes events that have been deleted (kind 5)
// Returns the filtered list of events
func FilterDeletedEvents(events []*nostr.Event, deletedEventIDs map[string]*nostr.Event) []*nostr.Event {
	if len(deletedEventIDs) == 0 {
		return events
	}

	filtered := make([]*nostr.Event, 0, len(events))
	for _, event := range events {
		if _, deleted := deletedEventIDs[event.ID]; !deleted {
			filtered = append(filtered, event)
		} else {
			logger.WithFields(map[string]interface{}{
				"event_id": event.ID,
				"kind":     event.Kind,
			}).Debug("Filtering out deleted event")
		}
	}

	logger.WithFields(map[string]interface{}{
		"original": len(events),
		"filtered": len(filtered),
		"removed":  len(events) - len(filtered),
	}).Debug("Filtered deleted events")

	return filtered
}

// ProcessEventsWithCacheResult contains the processed events and their profiles
type ProcessEventsWithCacheResult struct {
	Events   []*nostr.Event
	Profiles map[string]*Profile
}

// ProcessEventsWithCache is the standard process for fetching and processing events
// for kinds 1, 30023, 30040, 30041, 30818. It:
// 1. If indexEventID is provided, fetches the index event and only queries for events referenced in it
// 2. Fetches 2x the display limit (or all index-referenced events if indexEventID is provided)
// 3. Merges with existing cache map
// 4. Deduplicates (keeping newest)
// 5. Fetches deletion events
// 6. Removes deleted events
// 7. Sorts newest-first
// 8. Applies display limit
// 9. Fetches profiles for displayed events
// 10. Returns final events and profiles ready for display
func (c *Client) ProcessEventsWithCache(
	ctx context.Context,
	kind int,
	displayLimit int,
	existingEvents map[string]*nostr.Event, // Existing cache map (event ID -> event)
	relayURL string, // Relay to fetch from (empty = use primary relay)
	indexEventID string, // Optional: index event ID to fetch and filter by
	indexKind int, // Optional: kind of the index event (required if indexEventID is provided)
) (*ProcessEventsWithCacheResult, error) {
	// Calculate fetch limit (2x display limit, minimum 50)
	fetchLimit := displayLimit * 2
	if fetchLimit < 50 {
		fetchLimit = 50
	}

	// Determine which relay to use
	relays := []string{}
	if relayURL != "" {
		relays = []string{relayURL}
	} else {
		primaryRelay := c.GetPrimaryRelay()
		if primaryRelay == "" {
			return nil, fmt.Errorf("primary relay not configured")
		}
		relays = []string{primaryRelay}
	}

	var fetchedEvents []*nostr.Event
	var err error
	var indexItems []IndexItem

	// Step 1: If indexEventID is provided, fetch the index event and extract referenced items
	if indexEventID != "" {
		// Fetch the index event
		indexFilter := nostr.Filter{
			IDs: []string{indexEventID},
		}
		indexEvents, err := c.FetchEventsFromRelays(ctx, indexFilter, relays)
		if err != nil {
			return nil, fmt.Errorf("failed to fetch index event: %w", err)
		}
		if len(indexEvents) == 0 {
			return nil, fmt.Errorf("index event not found: %s", indexEventID)
		}

		// Parse the index event
		index, err := ParseIndexEvent(indexEvents[0], indexKind)
		if err != nil {
			return nil, fmt.Errorf("failed to parse index event: %w", err)
		}

		// Extract items of the target kind from the index
		indexItems = make([]IndexItem, 0)
		for _, item := range index.Items {
			if item.Kind == kind {
				indexItems = append(indexItems, item)
			}
		}

		if len(indexItems) == 0 {
			// No items of this kind in the index, return empty result
			return &ProcessEventsWithCacheResult{
				Events:   []*nostr.Event{},
				Profiles: make(map[string]*Profile),
			}, nil
		}

		logger.WithFields(map[string]interface{}{
			"kind":           kind,
			"index_items":    len(indexItems),
			"index_event_id": indexEventID,
		}).Debug("Fetched index event, querying referenced events")

		// Build filters for events referenced in the index
		// Group by author to create efficient filters
		authorDTags := make(map[string][]string) // author -> list of d tags
		for _, item := range indexItems {
			if item.Pubkey != "" && item.DTag != "" {
				authorDTags[item.Pubkey] = append(authorDTags[item.Pubkey], item.DTag)
			}
		}

		// Fetch events for each author (query by kind, author, and d tags)
		allFetchedEvents := make([]*nostr.Event, 0)
		for author, dTags := range authorDTags {
			// Query for events by this author with any of the d tags
			// Note: Nostr filters don't support OR for d tags, so we query each d tag separately
			// or query all events by author and filter locally
			filter := nostr.Filter{
				Kinds:   []int{kind},
				Authors: []string{author},
				// We'll filter by d tags locally after fetching
			}
			authorEvents, err := c.FetchEventsFromRelays(ctx, filter, relays)
			if err != nil {
				logger.WithFields(map[string]interface{}{
					"author": author,
					"error":  err,
				}).Warn("Failed to fetch events for author, continuing")
				continue
			}

			// Filter by d tags locally
			dTagSet := make(map[string]bool)
			for _, dTag := range dTags {
				dTagSet[dTag] = true
			}

			for _, event := range authorEvents {
				// Extract d tag from event
				var eventDTag string
				for _, tag := range event.Tags {
					if len(tag) > 0 && tag[0] == "d" && len(tag) > 1 {
						eventDTag = tag[1]
						break
					}
				}
				if eventDTag != "" && dTagSet[eventDTag] {
					allFetchedEvents = append(allFetchedEvents, event)
				}
			}
		}

		fetchedEvents = allFetchedEvents

		logger.WithFields(map[string]interface{}{
			"kind":           kind,
			"fetched":        len(fetchedEvents),
			"index_items":    len(indexItems),
			"index_event_id": indexEventID,
		}).Debug("Fetched events from index")
	} else {
		// Step 1: Fetch 2x display limit (standard process)
		filter := nostr.Filter{
			Kinds: []int{kind},
			Limit: fetchLimit,
		}

		logger.WithFields(map[string]interface{}{
			"kind":          kind,
			"fetch_limit":   fetchLimit,
			"display_limit": displayLimit,
			"relay":         relays[0],
		}).Debug("Fetching events for processing")

		// Use client's FetchEventsFromRelays (works with both specific relay and primary)
		fetchedEvents, err = c.FetchEventsFromRelays(ctx, filter, relays)
		if err != nil {
			return nil, fmt.Errorf("failed to fetch events: %w", err)
		}
	}

	logger.WithFields(map[string]interface{}{
		"kind":    kind,
		"fetched": len(fetchedEvents),
	}).Debug("Fetched events from relay")

	// Step 2: Merge with existing cache map (existing takes precedence if same ID)
	eventMap := make(map[string]*nostr.Event)

	// Add existing events first
	for id, event := range existingEvents {
		eventMap[id] = event
	}

	// Add/update with fetched events (keep newest if duplicate)
	for _, event := range fetchedEvents {
		existing, exists := eventMap[event.ID]
		if !exists || event.CreatedAt > existing.CreatedAt {
			eventMap[event.ID] = event
		}
	}

	logger.WithFields(map[string]interface{}{
		"existing": len(existingEvents),
		"fetched":  len(fetchedEvents),
		"merged":   len(eventMap),
	}).Debug("Merged events with cache")

	// Step 3: Convert map to slice (already deduplicated)
	allEvents := make([]*nostr.Event, 0, len(eventMap))
	for _, event := range eventMap {
		allEvents = append(allEvents, event)
	}

	// Step 4: Fetch deletion events for all authors
	authors := make([]string, 0, len(allEvents))
	authorSet := make(map[string]bool)
	for _, event := range allEvents {
		if !authorSet[event.PubKey] {
			authors = append(authors, event.PubKey)
			authorSet[event.PubKey] = true
		}
	}

	deletedEventIDs, err := c.FetchDeletionEvents(ctx, authors)
	if err != nil {
		logger.WithField("error", err).Warn("Failed to fetch deletion events, continuing without filtering")
		deletedEventIDs = make(map[string]*nostr.Event)
	}

	// Step 5: Remove deleted events
	allEvents = FilterDeletedEvents(allEvents, deletedEventIDs)

	// Step 6: Sort newest-first (by created_at descending)
	for i := 0; i < len(allEvents)-1; i++ {
		for j := i + 1; j < len(allEvents); j++ {
			if allEvents[i].CreatedAt < allEvents[j].CreatedAt {
				allEvents[i], allEvents[j] = allEvents[j], allEvents[i]
			}
		}
	}

	logger.WithFields(map[string]interface{}{
		"after_deletion": len(allEvents),
		"sorted":         true,
	}).Debug("Removed deletions and sorted events")

	// Step 7: Apply display limit
	if displayLimit > 0 && len(allEvents) > displayLimit {
		allEvents = allEvents[:displayLimit]
		logger.WithFields(map[string]interface{}{
			"limited": displayLimit,
		}).Debug("Applied display limit")
	}

	// Ensure we always show the display limit if we have enough events
	if len(allEvents) < displayLimit && len(allEvents) > 0 {
		logger.WithFields(map[string]interface{}{
			"available": len(allEvents),
			"requested": displayLimit,
		}).Debug("Fewer events available than display limit")
	}

	logger.WithFields(map[string]interface{}{
		"kind":          kind,
		"final_count":   len(allEvents),
		"display_limit": displayLimit,
	}).Info("Processed events with cache")

	// Step 8: Fetch profiles for displayed events
	profileAuthors := make([]string, 0, len(allEvents))
	profileAuthorSet := make(map[string]bool)
	for _, event := range allEvents {
		if !profileAuthorSet[event.PubKey] {
			profileAuthors = append(profileAuthors, event.PubKey)
			profileAuthorSet[event.PubKey] = true
		}
	}

	profiles, err := c.FetchProfilesBatch(ctx, profileAuthors)
	if err != nil {
		logger.WithField("error", err).Warn("Failed to fetch profiles, continuing without profiles")
		profiles = make(map[string]*Profile)
	}

	logger.WithFields(map[string]interface{}{
		"profiles_fetched": len(profiles),
		"authors":          len(authors),
	}).Debug("Fetched profiles for displayed events")

	return &ProcessEventsWithCacheResult{
		Events:   allEvents,
		Profiles: profiles,
	}, nil
}