@atproto/repo/tests/commit-proofs.test.ts

atproto repo and MST implementation

import { CID } from 'multiformats'
import { BlockMap } from '../src'
import { MST } from '../src/mst'
import { MemoryBlockstore } from '../src/storage'
import fixtures from './commit-proof-fixtures.json'

describe('commit proofs', () => {
  for (const fixture of fixtures) {
    it(fixture.comment, async () => {
      const { leafValue, keys, adds, dels } = fixture
      const leaf = CID.parse(leafValue)

      const storage = new MemoryBlockstore()
      let mst = await MST.create(storage)
      for (const key of keys) {
        mst = await mst.add(key, leaf)
      }

      const rootBeforeCommit = await mst.getPointer()
      expect(rootBeforeCommit.toString()).toEqual(fixture.rootBeforeCommit)

      for (const key of adds) {
        mst = await mst.add(key, leaf)
      }
      for (const key of dels) {
        mst = await mst.delete(key)
      }
      const rootAfterCommit = await mst.getPointer()
      expect(rootAfterCommit.toString()).toEqual(fixture.rootAfterCommit)
      const proofs = await Promise.all(
        [...adds, ...dels].map((key) => mst.getCoveringProof(key)),
      )
      const proof = proofs.reduce((acc, cur) => acc.addMap(cur), new BlockMap())
      const blocksInProof = fixture.blocksInProof.map((cid) => CID.parse(cid))
      for (const cid of blocksInProof) {
        expect(proof.has(cid)).toBe(true)
      }

      const invertAdds = adds.map((k) => (mst: MST) => mst.delete(k))
      const invertDels = dels.map((k) => (mst: MST) => mst.add(k, leaf))
      const invertOrders = permutations([...invertAdds, ...invertDels])

      const proofStorage = new MemoryBlockstore(proof)
      for (const order of invertOrders) {
        let proofMst = await MST.load(proofStorage, rootAfterCommit)
        for (const fn of order) {
          proofMst = await fn(proofMst)
        }
        const rootAfterInvert = await proofMst.getPointer()
        expect(rootAfterInvert.toString()).toEqual(fixture.rootBeforeCommit)
      }
    })
  }
})

function permutations<T>(arr: T[]): T[][] {
  if (arr.length <= 1) return [arr]

  return arr.reduce((perms: T[][], item: T, i: number) => {
    const rest = [...arr.slice(0, i), ...arr.slice(i + 1)]
    return perms.concat(permutations(rest).map((p) => [item, ...p]))
  }, [])
}