/**
 * @module tests/unit/brainy/graph-adjacency-cold-load
 * @description 7.33.2 — the graph-adjacency cold-load consistency guard. A native
 * graph provider can load its relationship COUNT (manifest) on a cold open but fail
 * to load the source→target adjacency (observed with cor 2.7.5's NativeGraphAdjacencyIndex
 * on mmap-filesystem: the SSTable-segment load is swallowed). The result is
 * `find({ connected })` / `neighbors()` / `related()` silently returning `[]` despite
 * persisted edges. Brainy now probes one known persisted edge on the first graph read;
 * if the index claims edges but the source resolves to none, it forces a rebuild from
 * storage, and only if even that fails does it throw a loud, catchable error instead of
 * serving `[]` as truth. These exercise the guard against a stubbed graph index.
 */

import { describe, it, expect } from 'vitest'
import { Brainy } from '../../../src/index.js'
import { GraphIndexNotReadyError } from '../../../src/errors/brainyError.js'
import { createTestConfig } from '../../helpers/test-factory.js'

/** Replace the brain's graph index with a stub that models a (possibly broken) cold load. */
function stubGraphIndex(
  brain: any,
  opts: { size: number; neighborsBeforeRebuild: string[]; neighborsAfterRebuild?: string[] }
) {
  let rebuilt = false
  const calls = { rebuild: 0, getNeighbors: 0 }
  brain.graphIndex = {
    size: () => opts.size,
    getNeighbors: async () => {
      calls.getNeighbors++
      return rebuilt ? opts.neighborsAfterRebuild ?? [] : opts.neighborsBeforeRebuild
    },
    rebuild: async () => {
      calls.rebuild++
      rebuilt = true
    },
    flush: async () => {},
    close: async () => {}
  }
  return calls
}

async function freshBrain(): Promise<any> {
  const brain: any = new Brainy(createTestConfig())
  await brain.init()
  brain._graphAdjacencyVerified = false
  return brain
}

describe('7.33.2 graph-adjacency cold-load consistency guard', () => {
  it('is a no-op when the adjacency is live (a persisted edge resolves to neighbors)', async () => {
    const brain = await freshBrain()
    const calls = stubGraphIndex(brain, { size: 12, neighborsBeforeRebuild: ['n1'] })
    brain.storage.getVerbs = async () => ({ items: [{ id: 'v1', sourceId: 's1', targetId: 't1' }], hasMore: false })

    await brain.verifyGraphAdjacencyLive()
    expect(calls.rebuild).toBe(0)
    await brain.close()
  })

  it('force-rebuilds when the index reports edges but the source probes empty', async () => {
    const brain = await freshBrain()
    const calls = stubGraphIndex(brain, { size: 12, neighborsBeforeRebuild: [], neighborsAfterRebuild: ['n1'] })
    brain.storage.getVerbs = async () => ({ items: [{ id: 'v1', sourceId: 's1', targetId: 't1' }], hasMore: false })

    await brain.verifyGraphAdjacencyLive()
    expect(calls.rebuild).toBe(1) // detected the empty adjacency + rebuilt it

    // Cached: a second call does not re-probe or re-rebuild.
    await brain.verifyGraphAdjacencyLive()
    expect(calls.rebuild).toBe(1)
    await brain.close()
  })

  it('throws GraphIndexNotReadyError when even a rebuild cannot load the adjacency', async () => {
    const brain = await freshBrain()
    stubGraphIndex(brain, { size: 12, neighborsBeforeRebuild: [], neighborsAfterRebuild: [] }) // never loads
    brain.storage.getVerbs = async () => ({ items: [{ id: 'v1', sourceId: 's1', targetId: 't1' }], hasMore: false })

    await expect(brain.verifyGraphAdjacencyLive()).rejects.toBeInstanceOf(GraphIndexNotReadyError)
    await brain.close()
  })

  it('no-op when no edges are claimed (size 0) — never even probes storage', async () => {
    const brain = await freshBrain()
    const calls = stubGraphIndex(brain, { size: 0, neighborsBeforeRebuild: [] })
    let probedStorage = false
    brain.storage.getVerbs = async () => {
      probedStorage = true
      return { items: [], hasMore: false }
    }

    await brain.verifyGraphAdjacencyLive()
    expect(calls.rebuild).toBe(0)
    expect(probedStorage).toBe(false)
    await brain.close()
  })

  it('no-op when storage has no edges (stale count) — does not rebuild or throw', async () => {
    const brain = await freshBrain()
    const calls = stubGraphIndex(brain, { size: 12, neighborsBeforeRebuild: [] })
    brain.storage.getVerbs = async () => ({ items: [], hasMore: false })

    await brain.verifyGraphAdjacencyLive()
    expect(calls.rebuild).toBe(0)
    await brain.close()
  })

  it('does not loop or break the query on a transient probe failure (re-checks next time)', async () => {
    const brain = await freshBrain()
    const calls = stubGraphIndex(brain, { size: 12, neighborsBeforeRebuild: [], neighborsAfterRebuild: ['n1'] })
    let firstCall = true
    brain.storage.getVerbs = async () => {
      if (firstCall) {
        firstCall = false
        throw new Error('transient storage hiccup')
      }
      return { items: [{ id: 'v1', sourceId: 's1', targetId: 't1' }], hasMore: false }
    }

    // First call: probe throws transiently → swallowed (no GraphIndexNotReadyError), flag reset.
    await brain.verifyGraphAdjacencyLive()
    expect(calls.rebuild).toBe(0)
    expect(brain._graphAdjacencyVerified).toBe(false) // re-check allowed

    // Second call: storage works → detects the empty adjacency + rebuilds.
    await brain.verifyGraphAdjacencyLive()
    expect(calls.rebuild).toBe(1)
    await brain.close()
  })
})