package nostr

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

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

// Client handles connections to Nostr relays with failover support
type Client struct {
	primaryRelay  string
	fallbackRelay string
	mu            sync.RWMutex
	lastError     error
}

// NewClient creates a new Nostr client with primary and fallback relays
func NewClient(primaryRelay, fallbackRelay string) *Client {
	return &Client{
		primaryRelay:  primaryRelay,
		fallbackRelay: fallbackRelay,
	}
}

// Connect connects to the relays (no-op for now, connections happen on query)
func (c *Client) Connect(ctx context.Context) error {
	// Connections are established lazily when querying
	return nil
}

// ConnectToRelay connects to a single relay (exported for use by services)
func (c *Client) ConnectToRelay(ctx context.Context, url string) (*nostr.Relay, error) {
	relay, err := nostr.RelayConnect(ctx, url)
	if err != nil {
		return nil, err
	}
	return relay, nil
}

// connectToRelay connects to a single relay (deprecated, use ConnectToRelay)
func (c *Client) connectToRelay(ctx context.Context, url string) (*nostr.Relay, error) {
	return c.ConnectToRelay(ctx, url)
}

// FetchEvent fetches a single event by filter, trying primary relay first, then fallback
func (c *Client) FetchEvent(ctx context.Context, filter nostr.Filter) (*nostr.Event, error) {
	// Try primary relay first
	relay, err := c.connectToRelay(ctx, c.primaryRelay)
	if err == nil {
		events, err := relay.QuerySync(ctx, filter)
		relay.Close()
		if err == nil && len(events) > 0 {
			return events[0], nil
		}
	}

	// Try fallback relay
	relay, err = c.connectToRelay(ctx, c.fallbackRelay)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to both relays: %w", err)
	}
	defer relay.Close()

	events, err := relay.QuerySync(ctx, filter)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch event: %w", err)
	}
	if len(events) == 0 {
		return nil, fmt.Errorf("event not found")
	}

	return events[0], nil
}

// FetchEvents fetches multiple events by filter, trying primary relay first, then fallback
func (c *Client) FetchEvents(ctx context.Context, filter nostr.Filter) ([]*nostr.Event, error) {
	// Try primary relay first
	relay, err := c.connectToRelay(ctx, c.primaryRelay)
	if err == nil {
		events, err := relay.QuerySync(ctx, filter)
		relay.Close()
		if err == nil {
			return events, nil
		}
	}

	// Try fallback relay
	relay, err = c.connectToRelay(ctx, c.fallbackRelay)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to both relays: %w", err)
	}
	defer relay.Close()

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

	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 (no-op for lazy connections)
func (c *Client) Close() {
	// Connections are closed after each query, so nothing to do here
}

// GetLastError returns the last error encountered
func (c *Client) GetLastError() error {
	c.mu.RLock()
	defer c.mu.RUnlock()
	return c.lastError
}

// IsConnected checks if at least one relay is connected (always true for lazy connections)
func (c *Client) IsConnected() bool {
	return true // We connect on-demand
}

// 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
	filter := nostr.Filter{
		Kinds: []int{1}, // kind 1 (notes) for testing
		Limit: 1,
	}

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