gitcitadel-online/internal/nostr/ebooks.go

package nostr

import (
	"context"
	"fmt"
	"log"

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

// EBooksService handles fetching top-level 30040 events
type EBooksService struct {
	client    *Client
	indexKind int
	relayURL  string
}

// NewEBooksService creates a new e-books service
func NewEBooksService(client *Client, indexKind int, relayURL string) *EBooksService {
	return &EBooksService{
		client:    client,
		indexKind: indexKind,
		relayURL:  relayURL,
	}
}

// EBookInfo represents information about a top-level index event
type EBookInfo struct {
	EventID   string
	Title     string
	DTag      string
	Author    string
	Summary   string
	Type      string
	CreatedAt int64
	Naddr     string
}

// FetchTopLevelIndexEvents fetches all top-level 30040 events from the specified relay
// Top-level means the event is not referenced in any other 30040 event's 'a' tags
func (es *EBooksService) FetchTopLevelIndexEvents(ctx context.Context) ([]EBookInfo, error) {
	// Connect to the specific relay
	relay, err := es.client.ConnectToRelay(ctx, es.relayURL)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to relay %s: %w", es.relayURL, err)
	}
	defer relay.Close()

	// Fetch all 30040 events (limit 10k)
	filter := nostr.Filter{
		Kinds: []int{es.indexKind},
		Limit: 10000,
	}
	logFilter(filter, fmt.Sprintf("all index events (kind %d) from %s", es.indexKind, es.relayURL))

	events, err := relay.QuerySync(ctx, filter)
	if err != nil {
		return nil, fmt.Errorf("failed to query events: %w", err)
	}

	log.Printf("Fetched %d index events from %s", len(events), es.relayURL)

	// Build a set of all referenced kind:pubkey:dtag from 'a' tags
	referencedSet := make(map[string]bool)
	for _, event := range events {
		for _, tag := range event.Tags {
			if len(tag) > 0 && tag[0] == "a" && len(tag) > 1 {
				// tag[1] is the kind:pubkey:dtag reference
				referencedSet[tag[1]] = true
			}
		}
	}

	log.Printf("Found %d referenced index events", len(referencedSet))

	// Filter to only top-level events (not referenced in any other event)
	var topLevelEvents []*nostr.Event
	for _, event := range events {
		// Build the kind:pubkey:dtag identifier for this event
		var dTag string
		for _, tag := range event.Tags {
			if len(tag) > 0 && tag[0] == "d" && len(tag) > 1 {
				dTag = tag[1]
				break
			}
		}

		if dTag == "" {
			continue // Skip events without d tag
		}

		// Check if this event is referenced by any other event
		eventRef := fmt.Sprintf("%d:%s:%s", es.indexKind, event.PubKey, dTag)
		if !referencedSet[eventRef] {
			topLevelEvents = append(topLevelEvents, event)
		}
	}

	log.Printf("Found %d top-level index events", len(topLevelEvents))

	// Convert to EBookInfo
	ebooks := make([]EBookInfo, 0, len(topLevelEvents))
	for _, event := range topLevelEvents {
		ebook := EBookInfo{
			EventID:   event.ID,
			Author:    event.PubKey,
			CreatedAt: int64(event.CreatedAt),
		}

		// Extract d tag
		for _, tag := range event.Tags {
			if len(tag) > 0 && tag[0] == "d" && len(tag) > 1 {
				ebook.DTag = tag[1]
				break
			}
		}

		// Extract title
		for _, tag := range event.Tags {
			if len(tag) > 0 && tag[0] == "title" && len(tag) > 1 {
				ebook.Title = tag[1]
				break
			}
		}
		if ebook.Title == "" {
			ebook.Title = ebook.DTag // Fallback to d tag
		}

		// Extract summary
		for _, tag := range event.Tags {
			if len(tag) > 0 && tag[0] == "summary" && len(tag) > 1 {
				ebook.Summary = tag[1]
				break
			}
		}

		// Extract type
		for _, tag := range event.Tags {
			if len(tag) > 0 && tag[0] == "type" && len(tag) > 1 {
				ebook.Type = tag[1]
				break
			}
		}

		// Build naddr - create proper bech32-encoded naddr
		// Extract relay hints from event tags if available
		var relays []string
		for _, tag := range event.Tags {
			if len(tag) > 0 && tag[0] == "relays" {
				relays = append(relays, tag[1:]...)
			}
		}
		// If no relays in tags, use the relay we fetched from
		if len(relays) == 0 {
			relays = []string{es.relayURL}
		}

		naddr, err := CreateNaddr(es.indexKind, ebook.Author, ebook.DTag, relays)
		if err != nil {
			log.Printf("Failed to create naddr for ebook %s: %v", ebook.DTag, err)
			// Fallback to kind:pubkey:dtag format
			ebook.Naddr = fmt.Sprintf("%d:%s:%s", es.indexKind, ebook.Author, ebook.DTag)
		} else {
			ebook.Naddr = naddr
		}

		ebooks = append(ebooks, ebook)
	}

	return ebooks, nil
}