All files / storage attachment-storage.ts

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/**
 * Content-addressable attachment storage.
 *
 * Each unique file is stored exactly once in attachment_blobs, keyed by its
 * SHA-256 hash. Attachment rows carry a content_hash FK instead of inline data,
 * so duplicate files (same bytes across many messages) are stored only once.
 */
 
import { createHash } from "node:crypto";
import type Database from "better-sqlite3-multiple-ciphers";
import { compressBuffer } from "./compression.js";
 
/**
 * Inserts attachment content into attachment_blobs if not already present,
 * and returns the SHA-256 hex hash for use as the content_hash FK.
 */
export function upsertAttachmentBlob(db: Database.Database, data: Buffer): string {
	const hash = createHash("sha256").update(data).digest("hex");
	const compressed = compressBuffer(data) ?? data;
	db.prepare("INSERT OR IGNORE INTO blobs.attachment_blobs (content_hash, data) VALUES (?, ?)").run(
		hash,
		compressed,
	);
	return hash;
}