askexperts/dist/stream/metadata.js

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/**
 * Functions for creating and parsing stream metadata events for NIP-173
 */
import { createEvent, validateNostrEvent } from '../common/crypto.js';
import { STREAM_METADATA_KIND } from './types.js';
/**
 * Creates a stream metadata event (kind:173) from a StreamMetadata object
 *
 * @param metadata - Stream metadata
 * @param senderPrivkey - Private key to sign the event
 * @returns Signed stream metadata event
 */
export function createStreamMetadataEvent(metadata, senderPrivkey) {
    // Create tags for the stream metadata event
    const tags = [
        ["version", metadata.version || "1"],
        ["encryption", metadata.encryption],
        ["compression", metadata.compression],
        ["binary", (!!metadata.binary).toString()]
    ];
    // Add relay tags
    for (const relay of metadata.relays) {
        tags.push(["relay", relay]);
    }
    // If encryption is enabled, add the receiver_pubkey tag
    if (metadata.encryption !== "none" && metadata.receiver_pubkey) {
        tags.push(["receiver_pubkey", metadata.receiver_pubkey]);
    }
    // Create and sign the stream metadata event
    return createEvent(STREAM_METADATA_KIND, "", tags, senderPrivkey);
}
/**
 * Parses a stream metadata event (kind:173) into a StreamMetadata object
 *
 * @param event - Stream metadata event
 * @returns StreamMetadata object
 * @throws Error if the event is invalid
 */
export function parseStreamMetadataEvent(event) {
    // Validate that it's a proper Nostr event
    if (!validateNostrEvent(event)) {
        throw new Error("Invalid Nostr event: signature verification failed");
    }
    // Validate that it's a stream metadata event
    if (event.kind !== STREAM_METADATA_KIND) {
        throw new Error(`Invalid event kind: ${event.kind}. Expected kind:${STREAM_METADATA_KIND} for stream metadata.`);
    }
    // Extract metadata from the event
    const streamId = event.pubkey;
    // Extract tags
    const versionTag = event.tags.find((tag) => tag[0] === "version");
    const encryptionTag = event.tags.find((tag) => tag[0] === "encryption");
    const compressionTag = event.tags.find((tag) => tag[0] === "compression");
    const binaryTag = event.tags.find((tag) => tag[0] === "binary");
    const receiverPubkeyTag = event.tags.find((tag) => tag[0] === "receiver_pubkey");
    const relayTags = event.tags.filter((tag) => tag[0] === "relay");
    // Validate required tags
    if (!versionTag) {
        throw new Error("Missing 'version' tag in metadata event");
    }
    if (!encryptionTag) {
        throw new Error("Missing 'encryption' tag in metadata event");
    }
    if (!compressionTag) {
        throw new Error("Missing 'compression' tag in metadata event");
    }
    if (!binaryTag) {
        throw new Error("Missing 'binary' tag in metadata event");
    }
    if (relayTags.length === 0) {
        throw new Error("Missing 'relay' tags in metadata event");
    }
    // Create metadata object
    const metadata = {
        streamId,
        version: versionTag[1],
        encryption: encryptionTag[1],
        compression: compressionTag[1],
        binary: binaryTag[1] === "true",
        relays: relayTags.map((tag) => tag[1]),
        event: event
    };
    // Add receiver_pubkey if encryption is used
    if (encryptionTag[1] !== "none" && receiverPubkeyTag) {
        metadata.receiver_pubkey = receiverPubkeyTag[1];
    }
    return metadata;
}
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