/**
 * Projection carrier paths of the host ApiProxy: history tail pages snapshot
 * attached state or fold one cold inspected prefix, loadOlder omits the block,
 * and live unit changes push session/projection frames.
 */

import { describe, expect, it } from 'vitest'
import { Context } from 'cordis'
import { z } from 'zod'
import AgentRegistry from '@deepseek-ai/dsh-agent'
import { createUserMessage } from '@deepseek-ai/dsh-llm'
import SessionStore, { SessionId } from '@deepseek-ai/dsh-session'
import type { Session, SessionEvent, SessionHeader } from '@deepseek-ai/dsh-session'
import SessionProjectionRegistry from '@deepseek-ai/dsh-session-projection'
import type { ProjectionDefinition } from '@deepseek-ai/dsh-session-projection'
import UserInteractionService from '@deepseek-ai/dsh-user-interaction'
import type { MuxFrame, RpcRequest } from '@deepseek-ai/dsh-host-apiproxy/api'
import { RpcId } from '@deepseek-ai/dsh-host-apiproxy/api/rpc'
import { createApiProxy } from '@deepseek-ai/dsh-host-apiproxy'

declare module '@deepseek-ai/dsh-session-projection/types' {
  interface SessionProjectionMap {
    'test/last-user': { text: string } | null
  }
}

let nextRpc = 1
function request<P>(payload: P): RpcRequest<P> {
  return { rpcId: RpcId(`proj-${String(nextRpc++)}`), payload }
}

/** Whole-value unit folding the latest user/message text; null before the first. */
type LastUserState = { text: string } | null
const lastUserUnit = (): ProjectionDefinition<'test/last-user', LastUserState> => ({
  key: 'test/last-user',
  schema: z.union([z.object({ text: z.string() }), z.null()]),
  init: () => null,
  apply: (state, event) => (event.type === 'user/message'
    ? { text: (event.data.content[0] as { text?: string }).text ?? '' }
    : state),
  view: state => state,
  stateVersion: 1,
})

async function harness(withRegistry: boolean): Promise<{ ctx: Context; session: Session }> {
  const ctx = new Context()
  await ctx.plugin(SessionStore)
  await ctx.plugin(UserInteractionService)
  await ctx.plugin(AgentRegistry)
  if (withRegistry) await ctx.plugin(SessionProjectionRegistry)
  const session = ctx.sessions.create()
  return { ctx, session }
}

/** Append `count` user messages so the log has paginable message boundaries. */
function seedMessages(session: Session, count: number): void {
  for (let i = 0; i < count; i++) {
    session.append('user/message', createUserMessage({
      content: [{ type: 'text', text: `m${i}` }],
      source: { kind: 'user' },
    }), { surfaceOp: 'append' })
  }
}

const api = (ctx: Context) => createApiProxy(ctx, { provider: 'p', model: 'm', cwd: '/tmp', workspaceRoot: '/tmp' })

describe('session.history projections block', () => {
  it('serves the unit value on the tail page with asOfSeq = last event seq', async () => {
    const { ctx, session } = await harness(true)
    ctx.sessionProjections.register(lastUserUnit())
    seedMessages(session, 3)
    const response = await api(ctx).sessions.history(request({ sessionId: session.id }))
    expect(response.result.ok).toBe(true)
    if (!response.result.ok) throw new Error('unreachable')
    const { events, projections } = response.result.value
    expect(projections).toBeDefined()
    expect(projections?.asOfSeq).toBe(session.seq - 1)
    expect(projections?.values['test/last-user']).toEqual({ text: 'm2' })
    // asOfSeq IS the window tail: the last served event carries it.
    expect(events.at(-1)?.event.seq).toBe(projections?.asOfSeq)
  })

  it('folds a cold inspected prefix without publishing an Agent', async () => {
    const ctx = new Context()
    await ctx.plugin(SessionStore)
    await ctx.plugin(UserInteractionService)
    await ctx.plugin(AgentRegistry)
    await ctx.plugin(SessionProjectionRegistry)
    ctx.sessionProjections.register(lastUserUnit())
    const sessionId = SessionId('session-cold-history')
    const meta: SessionHeader = { version: 0, id: sessionId, createdAt: 1, cwd: '/tmp' }
    const events = [{
      type: 'user/message',
      seq: 0,
      time: 2,
      data: createUserMessage({
        content: [{ type: 'text', text: 'persisted' }],
        source: { kind: 'user' },
      }),
      surfaceOp: 'append',
    }] as SessionEvent[]
    ctx.provide('sessionPersistence', {
      list: () => Promise.resolve([meta]),
      inspect: () => Promise.resolve({ meta, events }),
    } as never)

    const response = await api(ctx).sessions.history(request({ sessionId }))
    expect(response.result.ok).toBe(true)
    if (!response.result.ok) throw new Error('unreachable')
    expect(response.result.value.projections).toEqual({
      asOfSeq: 0,
      values: { 'test/last-user': { text: 'persisted' } },
    })
    expect(ctx.agents.get(sessionId)).toBeUndefined()
  })

  it('never carries the block on loadOlder pages (beforeSeq present)', async () => {
    const { ctx, session } = await harness(true)
    ctx.sessionProjections.register(lastUserUnit())
    seedMessages(session, 5)
    const older = await api(ctx).sessions.history(request({ sessionId: session.id, beforeSeq: 3, maxMessages: 2 }))
    expect(older.result.ok).toBe(true)
    if (!older.result.ok) throw new Error('unreachable')
    expect('projections' in older.result.value).toBe(false)
  })

  it('serves no block when the composition has no projection registry', async () => {
    const { ctx, session } = await harness(false)
    seedMessages(session, 2)
    const response = await api(ctx).sessions.history(request({ sessionId: session.id }))
    expect(response.result.ok).toBe(true)
    if (!response.result.ok) throw new Error('unreachable')
    expect('projections' in response.result.value).toBe(false)
  })

  it('drops a disposed registration from subsequent tail pages (empty block, key absent)', async () => {
    const { ctx, session } = await harness(true)
    const dispose = ctx.sessionProjections.register(lastUserUnit())
    seedMessages(session, 1)
    const proxy = api(ctx)
    const before = await proxy.sessions.history(request({ sessionId: session.id }))
    if (!before.result.ok) throw new Error('unreachable')
    expect(before.result.value.projections?.values['test/last-user']).toEqual({ text: 'm0' })

    dispose()
    const after = await proxy.sessions.history(request({ sessionId: session.id }))
    if (!after.result.ok) throw new Error('unreachable')
    // The registry is still mounted, so the block itself stays (asOfSeq cut
    // with zero keys); the disposed key reads as capability absence.
    expect(after.result.value.projections?.asOfSeq).toBe(session.seq - 1)
    expect(after.result.value.projections?.values).toEqual({})
  })
})

describe('session.list projections column', () => {
  it('serves attached rows from the live registry cut, watermarked for client seeding', async () => {
    const { ctx, session } = await harness(true)
    ctx.sessionProjections.register(lastUserUnit())
    seedMessages(session, 1)
    const response = await api(ctx).sessions.list(request({}))
    if (!response.result.ok) throw new Error('unreachable')
    const row = response.result.value.items.find(item => item.sessionId === session.id)
    expect(row?.projections?.values['test/last-user']).toEqual({ text: 'm0' })
    expect(row?.projections?.asOfSeq).toBe(session.seq - 1)
  })

  it('omits the column entirely when no registry is mounted', async () => {
    const { ctx, session } = await harness(false)
    seedMessages(session, 1)
    const response = await api(ctx).sessions.list(request({}))
    if (!response.result.ok) throw new Error('unreachable')
    const row = response.result.value.items.find(item => item.sessionId === session.id)
    expect(row).toBeDefined()
    expect(row !== undefined && 'projections' in row).toBe(false)
  })

  it('serves cold rows from the persisted projection cache with zero log loads', async () => {
    const { ctx } = await harness(true)
    const coldId = SessionId('session-cold-listing')
    const load = () => { throw new Error('list must not load event logs') }
    ctx.provide('sessionPersistence', {
      list: async () => [{ version: 0, id: coldId, createdAt: 5, cwd: '/tmp' }],
      locate: () => undefined,
      load,
      inspect: load,
      readFrom: load,
    } as never)
    ctx.provide('sessionProjectionCache', {
      // The carrier hands the listed header through as the identity witness.
      cachedSnapshot: (meta: { id: unknown; createdAt: number }) =>
        (meta.id === coldId && meta.createdAt === 5
          ? { asOfSeq: 7, values: { 'test/last-user': { text: 'cached' } } }
          : undefined),
    } as never)
    const response = await api(ctx).sessions.list(request({}))
    if (!response.result.ok) throw new Error('unreachable')
    const row = response.result.value.items.find(item => item.sessionId === coldId)
    expect(row?.running).toBe(false)
    expect(row?.projections).toEqual({ asOfSeq: 7, values: { 'test/last-user': { text: 'cached' } } })
  })

  it('cold rows without a cache plugin (or without a stored row) just lack the column', async () => {
    const { ctx } = await harness(true)
    const coldId = SessionId('session-cold-uncached')
    ctx.provide('sessionPersistence', {
      list: async () => [{ version: 0, id: coldId, createdAt: 5, cwd: '/tmp' }],
      locate: () => undefined,
    } as never)
    const response = await api(ctx).sessions.list(request({}))
    if (!response.result.ok) throw new Error('unreachable')
    const row = response.result.value.items.find(item => item.sessionId === coldId)
    expect(row).toBeDefined()
    expect(row !== undefined && 'projections' in row).toBe(false)
  })

  it('a throwing column read degrades that row, never the listing', async () => {
    const { ctx, session } = await harness(true)
    ctx.sessionProjections.register({
      ...lastUserUnit(),
      view: () => { throw new Error('unit exploded') },
    })
    seedMessages(session, 1)
    const response = await api(ctx).sessions.list(request({}))
    if (!response.result.ok) throw new Error('unreachable')
    const row = response.result.value.items.find(item => item.sessionId === session.id)
    expect(row).toBeDefined()
    expect(row !== undefined && 'projections' in row).toBe(false)
  })
})

describe('session/projection push frame', () => {
  /** Drain frames until `count` session/projection frames arrived. */
  async function collect(iterable: AsyncIterable<RpcRequest<MuxFrame>>, count: number, abort: AbortController): Promise<MuxFrame[]> {
    const frames: MuxFrame[] = []
    for await (const envelope of iterable) {
      frames.push(envelope.payload)
      if (frames.filter(f => f.type === 'session/projection').length >= count) abort.abort()
    }
    return frames
  }

  it('broadcasts a frame per changed unit with the causing seq, and none for same-reference applies', async () => {
    const { ctx, session } = await harness(true)
    ctx.sessionProjections.register(lastUserUnit())
    const proxy = api(ctx)
    // The gateway's onChanged subscription lives in an inject child whose
    // fiber activates asynchronously; yield until it lands before appending.
    await new Promise(resolve => setTimeout(resolve, 0))
    const abort = new AbortController()
    const stream = proxy.events.mux({ rpcId: RpcId('t-proj-mux'), payload: {} }, abort.signal)
    const collected = collect(stream, 2, abort)

    seedMessages(session, 1)
    // Same-reference apply: turn/start does not concern the unit — no frame.
    session.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })
    seedMessages(session, 1)

    const frames = await collected
    const pushes = frames.filter(
      (f): f is Extract<MuxFrame, { type: 'session/projection' }> => f.type === 'session/projection',
    )
    expect(pushes).toEqual([
      { type: 'session/projection', sessionId: session.id, key: 'test/last-user', value: { text: 'm0' }, seq: 0 },
      { type: 'session/projection', sessionId: session.id, key: 'test/last-user', value: { text: 'm0' }, seq: 2 },
    ])
    // Frame seq aligns with the tail block's asOfSeq vocabulary (higher-seq-wins compatible).
    const tail = await proxy.sessions.history(request({ sessionId: session.id }))
    if (!tail.result.ok) throw new Error('unreachable')
    expect(tail.result.value.projections?.asOfSeq).toBe(pushes.at(-1)?.seq)
  })

  it('emits no projection frames when the composition has no registry', async () => {
    const { ctx, session } = await harness(false)
    const proxy = api(ctx)
    const abort = new AbortController()
    const stream = proxy.events.mux({ rpcId: RpcId('t-noproj-mux'), payload: {} }, abort.signal)
    const frames: MuxFrame[] = []
    const drained = (async () => {
      for await (const envelope of stream) {
        frames.push(envelope.payload)
        if (frames.filter(f => f.type === 'session/event').length >= 2) abort.abort()
      }
    })()
    seedMessages(session, 2)
    await drained
    expect(frames.some(f => f.type === 'session/projection')).toBe(false)
  })
})