package auth

import (
	"context"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"time"

	"northwest.io/muxstr/internal/nostr"
)

// NostrCredentials implements credentials.PerRPCCredentials for NIP-98 authentication.
// It automatically signs each gRPC request with a Nostr event (kind 27235) and
// attaches it to the Authorization header.
type NostrCredentials struct {
	key            *nostr.Key
	includePayload bool
}

// NewNostrCredentials creates credentials using the provided key.
// Each RPC call will be authenticated with a freshly signed NIP-98 event.
// The key must have a private key (CanSign() must return true).
func NewNostrCredentials(key *nostr.Key) *NostrCredentials {
	return &NostrCredentials{
		key:            key,
		includePayload: false,
	}
}

// NewNostrCredentialsWithPayload creates credentials that include payload hashes.
// When enabled, a SHA256 hash of the request body is included in the auth event.
func NewNostrCredentialsWithPayload(key *nostr.Key) *NostrCredentials {
	return &NostrCredentials{
		key:            key,
		includePayload: true,
	}
}

// GetRequestMetadata implements credentials.PerRPCCredentials.
// It creates and signs a NIP-98 auth event for each request.
func (n *NostrCredentials) GetRequestMetadata(ctx context.Context, uri ...string) (map[string]string, error) {
	if len(uri) == 0 {
		return nil, fmt.Errorf("no URI provided")
	}

	// Create kind 27235 event (NIP-98 HTTP Auth)
	event := &nostr.Event{
		PubKey:    n.key.Public(),
		CreatedAt: time.Now().Unix(),
		Kind:      27235, // NIP-98 HTTP Auth
		Tags:      nostr.Tags{},
		Content:   "",
	}

	// Add URL tag
	event.Tags = append(event.Tags, nostr.Tag{"u", uri[0]})

	// Add method tag - default to POST for gRPC
	// The URI contains the method name, e.g., /nostr.v1.NostrRelay/PublishEvent
	event.Tags = append(event.Tags, nostr.Tag{"method", "POST"})

	// TODO: Add payload hash if includePayload is true
	// This requires access to the request body, which isn't available in GetRequestMetadata
	// We could use a context key to pass the payload hash from the application

	// Sign the event
	if err := n.key.Sign(event); err != nil {
		return nil, fmt.Errorf("failed to sign auth event: %w", err)
	}

	// Encode event as base64 JSON
	eventJSON, err := json.Marshal(event)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal auth event: %w", err)
	}

	authHeader := "Nostr " + base64.StdEncoding.EncodeToString(eventJSON)

	return map[string]string{
		"authorization": authHeader,
	}, nil
}

// RequireTransportSecurity implements credentials.PerRPCCredentials.
// Returns false to allow usage over insecure connections (for development).
// In production, use TLS and set this to true.
func (n *NostrCredentials) RequireTransportSecurity() bool {
	return false
}

// SetRequireTLS configures whether TLS is required.
// When true, the credentials will only work over TLS connections.
type NostrCredentialsWithTLS struct {
	*NostrCredentials
}

// NewNostrCredentialsWithTLS creates credentials that require TLS.
func NewNostrCredentialsWithTLS(key *nostr.Key) *NostrCredentialsWithTLS {
	return &NostrCredentialsWithTLS{
		NostrCredentials: NewNostrCredentials(key),
	}
}

// RequireTransportSecurity returns true to enforce TLS.
func (n *NostrCredentialsWithTLS) RequireTransportSecurity() bool {
	return true
}

// HashPayload creates a SHA256 hash of the payload for inclusion in auth events.
// This can be used to verify request integrity.
func HashPayload(payload []byte) string {
	hash := sha256.Sum256(payload)
	return fmt.Sprintf("%x", hash)
}