/**
 * @module tests/integration/cold-graph-connected-8.0
 * @description BRAINY-COLD-GRAPH-CONNECTED (8.0) — regression coverage for the silent-empty
 * graph-traversal bug, gated on the converged 8.0 contract: a sync `graphIndex.isReady()` that
 * is true ONLY when the source→target EDGES are loaded (NOT the membership/manifest count).
 *
 * On the FIRST `find({ connected })` after a cold process start of a LARGE brain (≥10k nouns,
 * which skips the eager index rebuild), a native graph adjacency can reload its relationship
 * COUNT (so `size() > 0`) but NOT its edges — so `getNeighbors()` returns `[]` for EVERY source
 * and brainy would serve that `[]` as if the anchor were genuinely edgeless.
 *
 * The 8.0 guard (`verifyGraphAdjacencyLive`) prefers the honest `isReady()` signal:
 *  - `isReady() === false` → hydrate the id-mapper, rebuild from storage, re-check; a still-false
 *    `isReady()` throws {@link GraphIndexNotReadyError} instead of returning `[]` ('rebuilt' when
 *    the rebuild heals it);
 *  - a genuinely edgeless anchor with `isReady() === true` verifies 'live' and the empty result
 *    stands — no spurious rebuild, no throw;
 *  - a provider WITHOUT `isReady()` falls back to the shipped 7.x known-edge-sample probe.
 *
 * These exercise REAL `find({ connected })` against an in-memory brain whose graph index is
 * instrumented with a test-double `isReady()` (and, for the fallback case, an empty-then-healed
 * `getNeighbors`). Only the readiness/edge surface is wrapped; the underlying real adjacency
 * (built by `relate()`) is unmasked once a rebuild "heals" it.
 */

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

/**
 * Build a real in-memory brain. Always seeds an UNRELATED edge (`E -> F`) so a GLOBAL known-edge
 * sample exists for the fallback probe even when the queried anchor is genuinely edgeless. When
 * `anchorEdges` is set, the anchor links out to three target nouns via `Knows`. Ids are
 * brainy-generated and returned for assertions.
 */
async function buildBrain(
  opts: { anchorEdges: boolean }
): Promise<{ brain: any; anchorId: string; targetIds: string[] }> {
  const brain: any = new Brainy(createTestConfig({ silent: true }))
  await brain.init()

  // Unrelated edge — guarantees storage.getVerbs() always yields a known-edge source.
  const eId = await brain.add({ data: 'node E', type: NounType.Person })
  const fId = await brain.add({ data: 'node F', type: NounType.Person })
  await brain.relate({ from: eId, to: fId, type: VerbType.Knows })

  const anchorId = await brain.add({ data: 'anchor', type: NounType.Person })

  const targetIds: string[] = []
  if (opts.anchorEdges) {
    for (const label of ['B', 'C', 'D']) {
      const tId = await brain.add({ data: `node ${label}`, type: NounType.Person })
      await brain.relate({ from: anchorId, to: tId, type: VerbType.Knows })
      targetIds.push(tId)
    }
  }

  // Fresh cold-start state: nothing verified yet.
  brain._graphAdjacencyVerified = false
  return { brain, anchorId, targetIds }
}

/**
 * Instrument the brain's real graph index with a test-double `isReady()` (the 8.0 contract) plus
 * an edge surface that goes empty while NOT ready. `getNeighbors` returns `[]` while `!ready`
 * (modelling the cold-unloaded adjacency) and delegates to the REAL index once a rebuild flips
 * `ready` on. `rebuild` is counted; it heals (`ready = true`) only when `healsOnRebuild` is set.
 * Pass `failFirstRebuild` to make the FIRST rebuild throw a transient error (without healing) so
 * the empty-result re-collect path in executeGraphSearch is exercised.
 */
function instrumentIsReady(
  brain: any,
  opts: { ready: boolean; healsOnRebuild: boolean; failFirstRebuild?: boolean }
): { rebuildCalls: number } {
  const gi = brain.graphIndex
  const origGetNeighbors = gi.getNeighbors.bind(gi)
  const state = { ready: opts.ready, rebuildCalls: 0 }

  gi.isReady = (): boolean => state.ready

  gi.getNeighbors = async (id: bigint, options?: any): Promise<bigint[]> =>
    state.ready ? origGetNeighbors(id, options) : []

  gi.rebuild = async (): Promise<void> => {
    state.rebuildCalls++
    if (opts.failFirstRebuild && state.rebuildCalls === 1) {
      throw new Error('transient rebuild hiccup')
    }
    if (opts.healsOnRebuild) state.ready = true // unmask the real (already-populated) adjacency
  }

  return state
}

/**
 * Fallback instrumentation — a provider WITHOUT `isReady()` (older cortex / JS baseline). Wraps
 * `getNeighbors` to return `[]` while `broken` and delegates to the REAL index once a rebuild
 * heals it. This is the shipped 7.x known-edge-sample probe path on 8.0.
 */
function instrumentNoIsReady(
  brain: any,
  opts: { broken: boolean; healsOnRebuild: boolean }
): { rebuildCalls: number } {
  const gi = brain.graphIndex
  // Ensure the provider does NOT expose isReady() — the default JS provider doesn't.
  expect(typeof gi.isReady).toBe('undefined')
  const origGetNeighbors = gi.getNeighbors.bind(gi)
  const state = { broken: opts.broken, rebuildCalls: 0 }

  gi.getNeighbors = async (id: bigint, options?: any): Promise<bigint[]> =>
    state.broken ? [] : origGetNeighbors(id, options)

  gi.rebuild = async (): Promise<void> => {
    state.rebuildCalls++
    if (opts.healsOnRebuild) state.broken = false
  }

  return state
}

describe('BRAINY-COLD-GRAPH-CONNECTED 8.0 — isReady()-gated, never serves a silent []', () => {
  let brains: any[] = []
  afterEach(async () => {
    for (const b of brains) {
      try {
        await b.close()
      } catch {
        /* best-effort cleanup */
      }
    }
    brains = []
  })

  it('(a) isReady() false → rebuild heals it true → find({ connected }) returns correct N (rebuilt)', async () => {
    const { brain, anchorId, targetIds } = await buildBrain({ anchorEdges: true })
    brains.push(brain)
    const state = instrumentIsReady(brain, { ready: false, healsOnRebuild: true })

    const results = await brain.find({ connected: { from: anchorId, direction: 'out' }, limit: 10 })

    expect(state.rebuildCalls).toBeGreaterThanOrEqual(1) // detected not-ready + healed it
    const ids = results.map((r: any) => r.id).sort()
    expect(ids).toEqual(targetIds.sort()) // B, C, D — the real edges, served after the heal
  })

  it('(b) isReady() stays false after rebuild → throws GraphIndexNotReadyError (NOT a silent [])', async () => {
    const { brain, anchorId } = await buildBrain({ anchorEdges: true })
    brains.push(brain)
    instrumentIsReady(brain, { ready: false, healsOnRebuild: false }) // rebuild never makes it ready

    await expect(
      brain.find({ connected: { from: anchorId, direction: 'out' }, limit: 10 })
    ).rejects.toBeInstanceOf(GraphIndexNotReadyError)
  })

  it('(c) edgeless anchor + isReady() true → returns [] with NO rebuild and NO throw', async () => {
    // The anchor has no edges, but E -> F does — the adjacency is genuinely loaded (ready).
    const { brain, anchorId } = await buildBrain({ anchorEdges: false })
    brains.push(brain)
    const state = instrumentIsReady(brain, { ready: true, healsOnRebuild: false })

    const results = await brain.find({ connected: { from: anchorId, direction: 'out' }, limit: 10 })

    expect(results).toEqual([]) // genuinely edgeless — empty is the truth
    expect(state.rebuildCalls).toBe(0) // ready adjacency → no spurious rebuild
  })

  it('(d) healthy isReady() true → correct results, NO rebuild', async () => {
    const { brain, anchorId, targetIds } = await buildBrain({ anchorEdges: true })
    brains.push(brain)
    const state = instrumentIsReady(brain, { ready: true, healsOnRebuild: false })

    const results = await brain.find({ connected: { from: anchorId, direction: 'out' }, limit: 10 })

    expect(state.rebuildCalls).toBe(0)
    const ids = results.map((r: any) => r.id).sort()
    expect(ids).toEqual(targetIds.sort())
  })

  it('(e) provider WITHOUT isReady() → falls back to the known-edge-sample probe (self-heals)', async () => {
    const { brain, anchorId, targetIds } = await buildBrain({ anchorEdges: true })
    brains.push(brain)
    const state = instrumentNoIsReady(brain, { broken: true, healsOnRebuild: true })

    const results = await brain.find({ connected: { from: anchorId, direction: 'out' }, limit: 10 })

    expect(state.rebuildCalls).toBeGreaterThanOrEqual(1) // detected the empty adjacency + healed it
    const ids = results.map((r: any) => r.id).sort()
    expect(ids).toEqual(targetIds.sort()) // B, C, D — served after the heal
  })

  it('(f) executeGraphSearch re-collect: a transient first rebuild leaves connectedIds empty; the empty-result guard then heals + re-collects', async () => {
    // First verify (inside neighbors()) hits a transient rebuild failure → returns 'live' without
    // healing, so getNeighbors stays empty and connectedIds is empty. The empty connectedIds set
    // then drives executeGraphSearch's own verify, whose rebuild now heals → 'rebuilt' → re-collect.
    const { brain, anchorId, targetIds } = await buildBrain({ anchorEdges: true })
    brains.push(brain)
    const state = instrumentIsReady(brain, { ready: false, healsOnRebuild: true, failFirstRebuild: true })

    const results = await brain.find({ connected: { from: anchorId, direction: 'out' }, limit: 10 })

    expect(state.rebuildCalls).toBeGreaterThanOrEqual(2) // first transient, second heals
    const ids = results.map((r: any) => r.id).sort()
    expect(ids).toEqual(targetIds.sort()) // re-collected after the heal
  })
})
