@ifc-lite/merge

Three-way merge engine for IFCX layers.

Built on two runs of the two-way comparison joined on entity identity, it plans merges at (entity, componentKey) granularity: an architect editing a wall's placement and an agent editing Pset_FireSafety on the same wall is not a conflict.

import {
  planThreeWayMerge,
  applyResolutions,
  buildMergeLayer,
} from '@ifc-lite/merge';

// A = the candidate layer's base, O = the target ref's state,
// T = the candidate applied to A (all ordered weakest-first).
const plan = planThreeWayMerge({ ancestor, ours, theirs });
// plan.autoOps   — apply cleanly on top of `ours`
// plan.conflicts — explicit records: concurrent-edit, delete-vs-modify,
//                  modify-vs-delete, hierarchy

const { ops, resolutions } = applyResolutions(plan, [
  { path: 'wall-1', componentKey: 'pset:Pset_FireSafety', choice: 'theirs' },
]);

const { file, layerId } = buildMergeLayer({
  ops: [...plan.autoOps, ...ops],
  author: { kind: 'human', principal: '[email protected]' },
  intent: 'Merge fire-safety reclassification into main',
  base: { kind: 'stack', id: stackHash },
  merge: { candidate, into: 'main', resolutions, resolver: '[email protected]' },
});

Also included:

• extractStackState — the "semantic reading" of a layer stack as per-entity component states (tombstones kept visible)
• buildRevertLayer — inverse-op layers ([base, L, revert(L)] composes back to base)
• planRebase — re-run the plan against a moved ref; prior resolutions replay automatically
• opsToNodes — serialize ops as ordinary IFCX node opinions

Spec: docs/architecture/layer-prs/05-merge.md. Part of the ifc-lite toolchain, MPL-2.0.