deno.land / x / replicache@v10.0.0-beta.0 / db / transformer.ts
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type OldHash = Hash;type NewHash = Hash;
export abstract class BaseTransformer { private readonly _transforming: Map<OldHash, Promise<NewHash>> = new Map(); private readonly _writtenMappings = new Map<OldHash, NewHash>();
// no constructor as the base class doesn't take a dag.Read or dag.Write
/** * This is a mapping from the old hash to the new hash for all the chunks that * were written. */ get mappings(): ReadonlyMap<OldHash, NewHash> { return this._writtenMappings; }
private _withTransformingCache( oldHash: OldHash, f: () => Promise<Hash>, ): Promise<NewHash> { const newHash = this._transforming.get(oldHash); if (newHash !== undefined) { return newHash; }
const p = f(); this._transforming.set(oldHash, p); return p; }
private _transformCommitWithCache( oldHash: OldHash, hashRefType = HashRefType.RequireStrong, ): Promise<NewHash> { return this._withTransformingCache(oldHash, () => this.transformCommit(oldHash, hashRefType), ); }
async transformCommit( oldHash: OldHash, hashRefType = HashRefType.RequireStrong, ): Promise<NewHash> { if (this.shouldSkip(oldHash)) { return oldHash; }
const chunk = await this.getChunk(oldHash); if (!chunk) { if (hashRefType === HashRefType.AllowWeak) { return oldHash; } throw new Error(`Chunk ${oldHash} not found`); } const {data} = chunk; assertCommitData(data);
const newCommitData = await this._transformCommitData(data); return this._maybeWriteChunk( oldHash, newCommitData, data, getRefsFromCommitData, ); }
protected shouldSkip(_oldHash: OldHash): boolean { return false; }
protected shouldForceWrite(_oldHash: OldHash): boolean { return false; }
abstract getChunk(oldHash: OldHash): Promise<dag.Chunk | undefined>;
async mustGetChunk(oldHash: OldHash): Promise<dag.Chunk> { return mustGetChunk(this, oldHash); }
private async _maybeWriteChunk<D extends Value>( oldHash: OldHash, newData: D, oldData: D, getRefs: (data: D) => readonly NewHash[], ): Promise<NewHash> { if (newData !== oldData || this.shouldForceWrite(oldHash)) { const newHash = await this.writeChunk(oldHash, newData, getRefs); this._writtenMappings.set(oldHash, newHash); return newHash; } return oldHash; }
protected abstract writeChunk<D extends Value>( oldHash: OldHash, newData: D, getRefs: (data: D) => readonly NewHash[], ): Promise<NewHash>;
private async _transformCommitData<M extends Meta>( data: CommitData<M>, ): Promise<CommitData<Meta>> { const [meta, valueHash, indexes] = await Promise.all([ this._transformCommitMeta(data.meta), this._transformCommitValue(data.valueHash), this._transformIndexRecords(data.indexes), ]);
if ( meta === data.meta && valueHash === data.valueHash && indexes === data.indexes ) { return data; } return { meta, valueHash, indexes, }; }
private _transformCommitMeta<M extends Meta>(meta: M): Promise<Meta> { switch (meta.type) { case MetaTyped.IndexChange: return this._transformIndexChangeMeta(meta);
case MetaTyped.Local: return this._transformLocalMeta(meta);
case MetaTyped.Snapshot: return this._transformSnapshot(meta); } }
private _transformBasisHash( basisHash: OldHash | null, hashRefType: HashRefType, ): Promise<NewHash> | null { if (basisHash !== null) { return this._transformCommitWithCache(basisHash, hashRefType); } return null; }
private async _transformSnapshot(meta: SnapshotMeta): Promise<SnapshotMeta> { // basisHash is weak for Snapshot Commits const basisHash = await this._transformBasisHash( meta.basisHash, HashRefType.AllowWeak, ); if (basisHash === meta.basisHash) { return meta; } return { basisHash, type: meta.type, lastMutationID: meta.lastMutationID, cookieJSON: meta.cookieJSON, }; }
private async _transformLocalMeta(meta: LocalMeta): Promise<LocalMeta> { const basisHashP = this._transformBasisHash( meta.basisHash, HashRefType.RequireStrong, ); // originalHash is weak for Local Commits const originalHashP = meta.originalHash && this._transformCommitWithCache(meta.originalHash, HashRefType.AllowWeak);
const basisHash = await basisHashP; const originalHash = await originalHashP;
if (basisHash === meta.basisHash && originalHash === meta.originalHash) { return meta; } return { basisHash, type: meta.type, mutationID: meta.mutationID, mutatorName: meta.mutatorName, mutatorArgsJSON: meta.mutatorArgsJSON, originalHash, timestamp: meta.timestamp, }; }
private async _transformIndexChangeMeta( meta: IndexChangeMeta, ): Promise<IndexChangeMeta> { const basisHash = await this._transformBasisHash( meta.basisHash, HashRefType.RequireStrong, ); if (basisHash === meta.basisHash) { return meta; } return { basisHash, type: meta.type, lastMutationID: meta.lastMutationID, }; }
private _transformCommitValue(valueHash: OldHash): Promise<NewHash> { return this._transformBTreeNodeWithCache(valueHash); }
private _transformBTreeNodeWithCache(h: OldHash): Promise<NewHash> { return this._withTransformingCache(h, () => this.transformBTreeNode(h)); }
async transformBTreeNode(oldHash: OldHash): Promise<NewHash> { if (this.shouldSkip(oldHash)) { return oldHash; }
const {data} = await this.mustGetChunk(oldHash); assertBTreeNode(data);
const newData = await this.transformBTreeNodeData(data); return this._maybeWriteChunk(oldHash, newData, data, btree.getRefs); }
transformBTreeNodeData(data: btree.DataNode): Promise<btree.DataNode>; transformBTreeNodeData(data: btree.InternalNode): Promise<btree.InternalNode>; async transformBTreeNodeData(data: btree.Node): Promise<btree.Node> { const level = data[0]; const entries = data[1]; let newEntries: btree.Node[1]; if (isInternalNode(data)) { newEntries = await this._transformBTreeInternalEntries( entries as btree.InternalNode[1], ); } else { newEntries = await this._transformBTreeDataEntries(entries); } if (newEntries === entries) { return data; }
// Changed. Need to create a new chunk. return [level, newEntries]; }
async transformBTreeDataEntry( entry: btree.Entry<ReadonlyJSONValue>, ): Promise<btree.Entry<ReadonlyJSONValue>> { return entry; }
private async _transformBTreeDataEntries( entries: readonly btree.Entry<ReadonlyJSONValue>[], ): Promise<readonly btree.Entry<ReadonlyJSONValue>[]> { return this._transformArray(entries, e => this.transformBTreeDataEntry(e)); }
async transformBTreeInternalEntry( entry: btree.Entry<OldHash>, ): Promise<btree.Entry<NewHash>> { const hash = await this._transformBTreeNodeWithCache(entry[1]); if (hash === entry[1]) { return entry; } return [entry[0], hash]; }
private async _transformBTreeInternalEntries( entries: readonly btree.Entry<OldHash>[], ): Promise<readonly btree.Entry<NewHash>[]> { return this._transformArray(entries, e => this.transformBTreeInternalEntry(e), ); }
private async _transformArray<T>( values: readonly T[], itemTransform: (item: T) => Promise<T>, ): Promise<readonly T[]> { const newValues = await Promise.all(values.map(itemTransform)); for (let i = 0; i < newValues.length; i++) { if (values[i] !== newValues[i]) { return newValues; } } return values; }
private _transformIndexRecords( indexes: readonly IndexRecord[], ): Promise<readonly IndexRecord[]> { return this._transformArray(indexes, i => this.transformIndexRecord(i)); }
async transformIndexRecord(index: IndexRecord): Promise<IndexRecord> { const valueHash = await this._transformBTreeNodeWithCache(index.valueHash); if (valueHash === index.valueHash) { return index; } return { definition: index.definition, valueHash, }; }}
export class Transformer extends BaseTransformer { protected readonly dagWrite: dag.Write;
constructor(dagWrite: dag.Write) { super(); this.dagWrite = dagWrite; }
override getChunk(oldHash: OldHash): Promise<dag.Chunk | undefined> { return this.dagWrite.getChunk(oldHash); }
protected override async writeChunk<D extends Value>( _oldHash: OldHash, newData: D, getRefs: (data: D) => readonly NewHash[], ): Promise<NewHash> { const {dagWrite} = this; const newChunk = dagWrite.createChunk(newData, getRefs(newData)); await dagWrite.putChunk(newChunk); return newChunk.hash; }}
replicache
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2 years ago
