gristlabs_grist-core/app/common/DocSnapshot.ts

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/**
* Core metadata about a single document version.
*/
export interface ObjSnapshot {
lastModified: string;
snapshotId: string;
}
/**
* Extended Grist metadata about a single document version. Names of fields are kept
* short since there is a tight limit on total metadata size in S3.
*/
export interface ObjMetadata {
t?: string; // timestamp
tz?: string; // timezone
h?: string; // actionHash
n?: number; // actionNum
label?: string;
}
export interface ObjSnapshotWithMetadata extends ObjSnapshot {
metadata?: ObjMetadata;
}
/**
* Information about a single document snapshot in S3, including a Grist docId.
*/
export interface DocSnapshot extends ObjSnapshotWithMetadata {
docId: string;
}
/**
* A collection of document snapshots. Most recent snapshots first.
*/
export interface DocSnapshots {
snapshots: DocSnapshot[];
}
/**
* Metadata format for external storage like S3 and Azure.
* The only difference is that external metadata values must be strings.
*
* For S3, there are restrictions on total length of metadata (2 KB).
* See: https://docs.aws.amazon.com/AmazonS3/latest/dev/UsingMetadata.html#UserMetadata
*/
type ExternalMetadata = Record<string, string>;
/**
* Convert metadata from internal Grist format to external storage format (string values).
*/
export function toExternalMetadata(metadata: ObjMetadata): ExternalMetadata {
const result: ExternalMetadata = {};
for (const [key, val] of Object.entries(metadata)) {
if (val !== undefined) { result[key] = String(val); }
}
return result;
}
/**
* Select metadata controlled by Grist, and convert to expected formats.
*/
export function toGristMetadata(metadata: ExternalMetadata): ObjMetadata {
const result: ObjMetadata = {};
for (const key of ['t', 'tz', 'h', 'label'] as const) {
if (metadata[key]) { result[key] = metadata[key]; }
}
if (metadata.n) { result.n = parseInt(metadata.n, 10); }
return result;
}