/**
 * @module tests/unit/transaction/vectorIndexOperations-rename
 * @description Coverage for the backend-neutral vector-index transaction
 * operations (formerly `AddToHNSWOperation` / `RemoveFromHNSWOperation`).
 * These op-name strings surface directly in consumer-visible transaction
 * journals and timings — a fossil "HNSW" name misdirects an operator running
 * a native (non-HNSW) vector provider. Verifies:
 *   1. rollback wiring stayed byte-identical under the rename,
 *   2. the emitted `name` stamps the active backend — `'js-hnsw'` for
 *      Brainy's own JS index, a provider's own `providerId` when it
 *      self-identifies, and the honest `'unknown-provider'` literal when
 *      neither applies (never a silently-wrong guess).
 */
import { describe, it, expect } from 'vitest'
import {
  AddToVectorIndexOperation,
  RemoveFromVectorIndexOperation,
  BatchAddToVectorIndexOperation
} from '../../../src/transaction/operations/IndexOperations.js'
import type { VectorIndexProvider } from '../../../src/plugin.js'
import type { VectorDocument, Vector } from '../../../src/coreTypes.js'
import { JsHnswVectorIndex } from '../../../src/hnsw/hnswIndex.js'

/**
 * A minimal, real (not mocked) VectorIndexProvider implementation backed by
 * a plain Map — exercises the exact contract the operations call through,
 * without any Brainy internals.
 */
class FakeVectorProvider implements VectorIndexProvider {
  readonly items = new Map<string, Vector>()
  constructor(readonly providerId?: string) {}

  async addItem(item: VectorDocument): Promise<string> {
    this.items.set(item.id, item.vector)
    return item.id
  }
  async removeItem(id: string): Promise<boolean> {
    return this.items.delete(id)
  }
  async getItem(id: string): Promise<VectorDocument | undefined> {
    const vector = this.items.get(id)
    return vector ? { id, vector } : undefined
  }
  async search(): Promise<Array<[string, number]>> {
    return []
  }
  size(): number {
    return this.items.size
  }
  clear(): void {
    this.items.clear()
  }
  async rebuild(): Promise<void> {}
  async flush(): Promise<number> {
    return 0
  }
  getPersistMode(): 'immediate' | 'deferred' {
    return 'immediate'
  }
}

describe('Vector index transaction operations — backend-neutral rename', () => {
  describe('rollback wiring (byte-identical behavior under the rename)', () => {
    it('AddToVectorIndexOperation rollback removes a newly-added item', async () => {
      const provider = new FakeVectorProvider('fake-provider')
      const op = new AddToVectorIndexOperation(provider, 'id-1', [1, 2, 3])

      const rollback = await op.execute()
      expect(provider.items.has('id-1')).toBe(true)

      await rollback()
      expect(provider.items.has('id-1')).toBe(false)
    })

    it('AddToVectorIndexOperation rollback is a no-op when the item pre-existed (update semantics)', async () => {
      const provider = new FakeVectorProvider('fake-provider')
      await provider.addItem({ id: 'id-1', vector: [9, 9, 9] })

      const op = new AddToVectorIndexOperation(provider, 'id-1', [1, 2, 3])
      const rollback = await op.execute()
      expect(provider.items.get('id-1')).toEqual([1, 2, 3])

      await rollback()
      // Pre-existing item is NOT removed by rollback — it stays (the update
      // itself is not undone by this op; that's RemoveFromVectorIndexOperation's job).
      expect(provider.items.has('id-1')).toBe(true)
    })

    it('RemoveFromVectorIndexOperation rollback re-adds the item with its original vector', async () => {
      const provider = new FakeVectorProvider('fake-provider')
      await provider.addItem({ id: 'id-1', vector: [4, 5, 6] })

      const op = new RemoveFromVectorIndexOperation(provider, 'id-1', [4, 5, 6])
      const rollback = await op.execute()
      expect(provider.items.has('id-1')).toBe(false)

      await rollback()
      expect(provider.items.get('id-1')).toEqual([4, 5, 6])
    })

    it('BatchAddToVectorIndexOperation rolls back every item in reverse order on undo', async () => {
      const provider = new FakeVectorProvider('fake-provider')
      const op = new BatchAddToVectorIndexOperation(provider, [
        { id: 'a', vector: [1] },
        { id: 'b', vector: [2] },
        { id: 'c', vector: [3] }
      ])

      const rollback = await op.execute()
      expect([...provider.items.keys()].sort()).toEqual(['a', 'b', 'c'])

      await rollback()
      expect(provider.items.size).toBe(0)
    })
  })

  describe('backend stamping in the emitted op name', () => {
    it('stamps the real JS HNSW index as js-hnsw (self-identifying providerId)', () => {
      const index = new JsHnswVectorIndex()
      const addOp = new AddToVectorIndexOperation(index, 'id-1', [1, 2, 3])
      const removeOp = new RemoveFromVectorIndexOperation(index, 'id-1', [1, 2, 3])

      expect(addOp.name).toBe('AddToVectorIndex(js-hnsw)')
      expect(removeOp.name).toBe('RemoveFromVectorIndex(js-hnsw)')
    })

    it('stamps a self-identifying provider\'s own providerId, never "HNSW"', () => {
      const provider = new FakeVectorProvider('acme-diskann')
      const addOp = new AddToVectorIndexOperation(provider, 'id-1', [1, 2, 3])
      const removeOp = new RemoveFromVectorIndexOperation(provider, 'id-1', [1, 2, 3])
      const batchOp = new BatchAddToVectorIndexOperation(provider, [{ id: 'a', vector: [1] }])

      expect(addOp.name).toBe('AddToVectorIndex(acme-diskann)')
      expect(removeOp.name).toBe('RemoveFromVectorIndex(acme-diskann)')
      expect(batchOp.name).toBe('BatchAddToVectorIndex(acme-diskann)')
      expect(addOp.name).not.toContain('HNSW')
      expect(removeOp.name).not.toContain('HNSW')
    })

    it('honestly reports "unknown-provider" rather than guessing when a provider omits providerId', () => {
      const provider = new FakeVectorProvider(undefined)
      const addOp = new AddToVectorIndexOperation(provider, 'id-1', [1, 2, 3])
      const removeOp = new RemoveFromVectorIndexOperation(provider, 'id-1', [1, 2, 3])

      expect(addOp.name).toBe('AddToVectorIndex(unknown-provider)')
      expect(removeOp.name).toBe('RemoveFromVectorIndex(unknown-provider)')
      // Never silently falls back to the JS engine's name for a provider it
      // knows nothing about — that's the exact fossil-naming bug being fixed.
      expect(addOp.name).not.toContain('js-hnsw')
    })
  })
})