// @vitest-environment jsdom
import { beforeEach, describe, expect, it, vi } from 'vitest'
import { mount } from '@vue/test-utils'
import { createPinia, setActivePinia } from 'pinia'
import { defineComponent, nextTick } from 'vue'

const mockScrollToBottom = vi.hoisted(() => vi.fn())
const mockScrollToMessage = vi.hoisted(() => vi.fn())
const mockScrollToAnchor = vi.hoisted(() => vi.fn())
const mockCaptureViewportPosition = vi.hoisted(() => vi.fn())
const mockRestoreViewportPosition = vi.hoisted(() => vi.fn())
const mockCaptureScrollPosition = vi.hoisted(() => vi.fn())
const mockRestoreScrollPosition = vi.hoisted(() => vi.fn())
const mockIsNearBottom = vi.hoisted(() => vi.fn(() => true))

vi.mock('vue-i18n', () => ({
  useI18n: () => ({
    t: (key: string) => key,
  }),
}))

vi.mock('@/composables/useTheme', () => ({
  useTheme: () => ({ isDark: false }),
}))

vi.mock('@/components/hermes/chat/VirtualMessageList.vue', () => ({
  default: defineComponent({
    name: 'VirtualMessageList',
    props: {
      messages: { type: Array, default: () => [] },
    },
    emits: ['top-reach'],
    setup(_props, { expose }) {
      expose({
        isNearBottom: mockIsNearBottom,
        scrollToBottom: mockScrollToBottom,
        scrollToMessage: mockScrollToMessage,
        scrollToAnchor: mockScrollToAnchor,
        captureScrollPosition: mockCaptureScrollPosition,
        restoreScrollPosition: mockRestoreScrollPosition,
        captureViewportPosition: mockCaptureViewportPosition,
        restoreViewportPosition: mockRestoreViewportPosition,
      })
    },
    template: `
      <div class="virtual-message-list-stub">
        <slot name="item" v-for="message in messages" :key="message.id" :message="message" />
      </div>
    `,
  }),
}))

vi.mock('@/components/hermes/chat/MessageItem.vue', () => ({
  default: defineComponent({
    name: 'MessageItem',
    props: { message: { type: Object, required: true } },
    template: '<div class="stub-message" :data-id="message.id">{{ message.content }}</div>',
  }),
}))

import MessageList from '@/components/hermes/chat/MessageList.vue'
import { useChatStore, type Message, type Session } from '@/stores/hermes/chat'

function makeMessage(id: string): Message {
  return { id, role: 'user', content: id, timestamp: Date.now() }
}

function makeSession(id: string): Session {
  return {
    id,
    title: id,
    messages: [makeMessage(`${id}-message`)],
    createdAt: Date.now(),
    updatedAt: Date.now(),
  }
}

async function flushSessionScroll() {
  await nextTick()
  await nextTick()
}

describe('MessageList session scroll position', () => {
  beforeEach(() => {
    setActivePinia(createPinia())
    vi.clearAllMocks()
    mockIsNearBottom.mockReturnValue(true)
  })

  it('restores a previous session scroll position instead of forcing the bottom', async () => {
    const chatStore = useChatStore()
    chatStore.activeSessionId = 'scroll-session-a'
    chatStore.activeSession = makeSession('scroll-session-a')

    mount(MessageList, {
      global: {
        stubs: { Transition: false },
      },
    })
    await flushSessionScroll()
    vi.clearAllMocks()

    const sessionASnapshot = {
      scrollTop: 320,
      scrollHeight: 1200,
      clientHeight: 500,
      wasNearBottom: false,
    }
    mockCaptureViewportPosition.mockReturnValue(sessionASnapshot)

    chatStore.activeSessionId = 'scroll-session-b'
    chatStore.activeSession = makeSession('scroll-session-b')
    await flushSessionScroll()
    expect(mockCaptureViewportPosition).toHaveBeenCalled()

    vi.clearAllMocks()
    mockCaptureViewportPosition.mockReturnValue({
      scrollTop: 40,
      scrollHeight: 1000,
      clientHeight: 500,
      wasNearBottom: false,
    })

    chatStore.activeSessionId = 'scroll-session-a'
    chatStore.activeSession = makeSession('scroll-session-a')
    await flushSessionScroll()

    expect(mockRestoreViewportPosition).toHaveBeenCalledWith(sessionASnapshot)
    expect(mockScrollToBottom).not.toHaveBeenCalled()
  })
})