package nostr

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
)

// Event represents a Nostr event as defined in NIP-01.
type Event struct {
	ID        string `json:"id"`
	PubKey    string `json:"pubkey"`
	CreatedAt int64  `json:"created_at"`
	Kind      int    `json:"kind"`
	Tags      Tags   `json:"tags"`
	Content   string `json:"content"`
	Sig       string `json:"sig"`
}

// Serialize returns the canonical JSON serialization of the event for ID computation.
// Format: [0, "pubkey", created_at, kind, tags, "content"]
func (e *Event) Serialize() []byte {
	// Use json.Marshal for proper escaping of content and tags
	arr := []interface{}{
		0,
		e.PubKey,
		e.CreatedAt,
		e.Kind,
		e.Tags,
		e.Content,
	}
	data, _ := json.Marshal(arr)
	return data
}

// ComputeID calculates the SHA256 hash of the serialized event.
// Returns the 64-character hex-encoded ID.
func (e *Event) ComputeID() string {
	serialized := e.Serialize()
	hash := sha256.Sum256(serialized)
	return hex.EncodeToString(hash[:])
}

// SetID computes and sets the event ID.
func (e *Event) SetID() {
	e.ID = e.ComputeID()
}

// CheckID verifies that the event ID matches the computed ID.
func (e *Event) CheckID() bool {
	return e.ID == e.ComputeID()
}

// MarshalJSON implements json.Marshaler with empty tags as [] instead of null.
func (e Event) MarshalJSON() ([]byte, error) {
	type eventAlias Event
	ea := eventAlias(e)
	if ea.Tags == nil {
		ea.Tags = Tags{}
	}
	return json.Marshal(ea)
}

// String returns a JSON representation of the event for debugging.
func (e *Event) String() string {
	data, err := json.MarshalIndent(e, "", "  ")
	if err != nil {
		return fmt.Sprintf("<Event error: %v>", err)
	}
	return string(data)
}