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Claude
57a05bbee0
Concurrent edits to shared notes (e.g., one user checks a shopping list item while another adds an item) were lost because the sync system used whole-document Last-Write-Wins. This replaces it with a 3-way line-level content merge using node-diff3, so changes to different lines are preserved from both users. Key changes: - Add node-diff3 for 3-way line-level content merging - Remove the timestamp gate in processSyncPush that rejected entire offline sync pushes when another user had updated the note - Add content merge to both the sync push path and the PATCH endpoint, using version snapshots as the merge base - Send baseVersion from the client so the server can find the correct common ancestor for 3-way merge - Protect pending local fields during client pull merge by reading the sync queue and preserving queued-but-unpushed changes - Add comprehensive tests for content merge, server sync, and CRDT merge https://claude.ai/code/session_01FNpVBBjM6vKzfR8y9NM9Ci
89 lines
2.7 KiB
TypeScript
89 lines
2.7 KiB
TypeScript
import { diff3Merge } from 'node-diff3';
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/**
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* Resolve a conflict region by comparing each line against the base.
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* If only one side changed a line, take that change.
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* If both sides changed the same line, prefer remote (LWW).
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* Handles different-length regions by appending extra lines.
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*/
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function resolveConflict(
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aLines: string[],
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oLines: string[],
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bLines: string[]
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): string[] {
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const maxLen = Math.max(aLines.length, bLines.length, oLines.length);
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const result: string[] = [];
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for (let i = 0; i < maxLen; i++) {
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const a = i < aLines.length ? aLines[i] : undefined;
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const o = i < oLines.length ? oLines[i] : undefined;
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const b = i < bLines.length ? bLines[i] : undefined;
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const aChanged = a !== o;
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const bChanged = b !== o;
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if (aChanged && !bChanged && a !== undefined) {
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// Only local changed this line — take local
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result.push(a);
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} else if (bChanged && !aChanged && b !== undefined) {
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// Only remote changed this line — take remote
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result.push(b);
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} else if (aChanged && bChanged) {
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// Both changed — LWW: prefer remote
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if (b !== undefined) result.push(b);
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// If remote deleted (undefined) but local has it, skip (remote wins)
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} else {
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// Neither changed, or both are the same as base
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if (o !== undefined) result.push(o);
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else if (b !== undefined) result.push(b);
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else if (a !== undefined) result.push(a);
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}
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}
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return result;
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}
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/**
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* 3-way line-level merge for note content.
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* Takes a base (common ancestor), local (incoming), and remote (server current).
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* For conflict regions, resolves line-by-line: if only one side changed a line,
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* take that change. If both changed the same line, prefer remote (LWW).
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*/
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export function mergeContent(base: string, local: string, remote: string): string {
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// If any two are identical, short-circuit
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if (local === remote) return remote;
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if (local === base) return remote;
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if (remote === base) return local;
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const baseLines = base.split('\n');
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const localLines = local.split('\n');
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const remoteLines = remote.split('\n');
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const regions = diff3Merge(localLines, baseLines, remoteLines);
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const merged: string[] = [];
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for (const region of regions) {
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if (region.ok) {
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merged.push(...region.ok);
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} else if (region.conflict) {
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merged.push(...resolveConflict(
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region.conflict.a,
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region.conflict.o,
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region.conflict.b
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));
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}
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}
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return merged.join('\n');
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}
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/**
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* 2-way merge fallback when no base is available.
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* Uses an empty string as the base, so all lines from both sides appear
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* as additions. For conflicts (same region), prefers remote.
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*/
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export function mergeContentTwoWay(local: string, remote: string): string {
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if (local === remote) return remote;
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return mergeContent('', local, remote);
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}
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