/**
 * Repro + behavioral pin for the chat-switch projection retention contract:
 * a session's projection store (openRouterCost is the canonical example) must
 * survive a selection change and remain readable through the same value face
 * when the session becomes current again.
 *
 * Server frames exercised:
 * - session.list rows carrying a projections block (the cold seed path)
 * - session/projection push frames to a live session
 * - host/session-removed (transient host teardown) + host/session-added
 * - session/subscribed (durable-replay baseline) + a re-pulled history tail
 *
 * The manager's per-session ProjectionValueStore is retained across select();
 * this suite pins the retention contract so a regression in the
 * retention/seeding discipline shows up as a red test here.
 */
import { describe, expect, it } from 'vitest'
import type { SessionId } from '@deepseek-ai/dsh-api-remotes/client'
import { SessionManager } from '../src/client/sessions/manager.ts'
import { FakeApiClient, fakeRemote, ok } from './fake-api.client.ts'

const S1 = 'fk-s1' as SessionId
const S2 = 'fk-s2' as SessionId

const COST = { totalUsd: 1.23, pricedSteps: 1, unknownModelSteps: 0, currency: 'USD' as const }

function summary(sessionId: SessionId, projections?: { asOfSeq: number; values: Record<string, unknown> }) {
  return {
    sessionId,
    updatedAt: 100,
    running: false,
    blank: false,
    ...(projections === undefined ? {} : { projections }),
  } as never
}

describe('projection retention across chat switches (repro)', () => {
  it('retains the projection store for a session that was opened, seeded, and switched away from and back', async () => {
    const api = new FakeApiClient()
    api.onList = () => Promise.resolve(ok({ items: [summary(S1), summary(S2)] }))
    const manager = new SessionManager(api, fakeRemote())
    await manager.refreshList()

    // A live push frame lands the cost in S1's resident store.
    manager.handleMuxEnvelope({
      rpcId: 'seed' as never,
      payload: { type: 'session/projection', sessionId: S1, key: 'openRouterCost', value: COST, seq: 5 } as never,
    })
    expect(manager.getListSnapshot().items[0]?.projectionValues?.openRouterCost).toEqual(COST)

    // The conversation switches to another chat and back; nothing removes S1.
    manager.select(S2)
    manager.select(S1)
    expect(manager.getListSnapshot().items[0]?.projectionValues?.openRouterCost).toEqual(COST)
  })

  it('a host/session-removed disposal followed by a re-add re-seeds the cost from the list row block', async () => {
    const api = new FakeApiClient()
    api.onList = () => Promise.resolve(ok({
      items: [
        summary(S1, { asOfSeq: 6, values: { openRouterCost: COST } }),
        summary(S2),
      ],
    }))
    const manager = new SessionManager(api, fakeRemote())
    await manager.refreshList()
    expect(manager.getListSnapshot().items.find(item => item.sessionId === S1)?.projectionValues?.openRouterCost)
      .toEqual(COST)

    // Transient host teardown: the chat leaves the list; its projection store
    // is retained (the Session instance survives removal), and the durable
    // chat still exists host-side, so a list refresh re-adds it.
    manager.handleHostEnvelope({
      rpcId: 'rm' as never,
      payload: { type: 'host/session-removed', sessionId: S1 } as never,
    })
    expect(manager.getListSnapshot().items.find(item => item.sessionId === S1)).toBeUndefined()

    await manager.refreshList()
    expect(manager.getListSnapshot().items.find(item => item.sessionId === S1)?.projectionValues?.openRouterCost)
      .toEqual(COST)
  })

  it('lifts the removed tombstone when a disposed session is re-listed by the host', async () => {
    const api = new FakeApiClient()
    api.onList = () => Promise.resolve(ok({ items: [summary(S1), summary(S2)] }))
    const manager = new SessionManager(api, fakeRemote())
    await manager.refreshList()

    const session = manager.get(S1)
    manager.handleHostEnvelope({
      rpcId: 'rm' as never,
      payload: { type: 'host/session-removed', sessionId: S1 } as never,
    })
    expect(session.getSnapshot().removed).toBe(true)
    // The same instance survives (resident-instance rule).
    expect(manager.get(S1)).toBe(session)

    // The durable chat comes back: the re-listing revives the surviving
    // instance rather than leaving the conversation tombstoned forever.
    manager.handleHostEnvelope({
      rpcId: 'add' as never,
      payload: { type: 'host/session-added', blank: false, sessionId: S1 } as never,
    })
    expect(session.getSnapshot().removed).toBe(false)
  })

  it('revives through a list refresh when the host re-lists a previously disposed session', async () => {
    const api = new FakeApiClient()
    const listed = [summary(S1), summary(S2)]
    api.onList = () => Promise.resolve(ok({ items: listed }))
    const manager = new SessionManager(api, fakeRemote())
    await manager.refreshList()

    const session = manager.get(S1)
    manager.handleHostEnvelope({
      rpcId: 'rm' as never,
      payload: { type: 'host/session-removed', sessionId: S1 } as never,
    })
    expect(session.getSnapshot().removed).toBe(true)

    // The host never re-emits host/session-added for an existing id; the
    // durable session simply appears again on the next list pull.
    await manager.refreshList()
    expect(session.getSnapshot().removed).toBe(false)
    expect(manager.getListSnapshot().items.find(item => item.sessionId === S1)).toBeDefined()
  })

  it('survives a subscribed durable-replay baseline when the value is at or before the baseline', async () => {
    const api = new FakeApiClient()
    api.onList = () => Promise.resolve(ok({ items: [summary(S1)] }))
    const manager = new SessionManager(api, fakeRemote())
    await manager.refreshList()

    manager.handleMuxEnvelope({
      rpcId: 'push' as never,
      payload: { type: 'session/projection', sessionId: S1, key: 'openRouterCost', value: COST, seq: 3 } as never,
    })

    // The durable baseline is at seq 3, so the row is not phantom: it survives.
    manager.handleMuxEnvelope({
      rpcId: 'sub' as never,
      payload: { type: 'session/subscribed', sessionId: S1, lastSeq: 3 } as never,
    })
    expect(manager.getListSnapshot().items[0]?.projectionValues?.openRouterCost).toEqual(COST)
  })
})