// @vitest-environment jsdom
import { describe, expect, it, vi } from 'vitest'
import {
  CENTER_COLUMN_REVALIDATE_MS,
  resolveCenterColumn,
} from '../src/client/center-column.ts'

interface Fixture {
  doc: Document
  col: HTMLDivElement
  slot: HTMLDivElement
}

function connectedColumn(doc = document.implementation.createHTMLDocument()): Fixture {
  const col = doc.createElement('div')
  const slot = doc.createElement('div')
  slot.dataset.slot = 'conversation'
  col.append(slot)
  doc.body.append(col)
  return { doc, col, slot }
}

describe('center-column locator (issue #403)', () => {
  it('reuses a connected cached column without querying during the hot-path window', () => {
    const { doc, col, slot } = connectedColumn()
    let now = 0
    const query = vi.fn<() => Element | null>(() => slot)
    const options = { document: doc, query, now: () => now }

    expect(resolveCenterColumn(col, options)).toBe(col)
    now = CENTER_COLUMN_REVALIDATE_MS - 1
    expect(resolveCenterColumn(col, options)).toBe(col)
    expect(query).not.toHaveBeenCalled()
  })

  it('fully revalidates a connected cache at the 1.5s safety-net boundary', () => {
    const { doc, col, slot } = connectedColumn()
    let now = 0
    const query = vi.fn<() => Element | null>(() => slot)
    const options = { document: doc, query, now: () => now }

    expect(resolveCenterColumn(col, options)).toBe(col)
    expect(query).not.toHaveBeenCalled()

    now = CENTER_COLUMN_REVALIDATE_MS
    expect(resolveCenterColumn(col, options)).toBe(col)
    expect(query).toHaveBeenCalledTimes(1)
  })

  it('revalidates immediately when the html style signal changes', () => {
    const { doc, col, slot } = connectedColumn()
    let now = 0
    const query = vi.fn<() => Element | null>(() => slot)
    const options = { document: doc, query, now: () => now }

    expect(resolveCenterColumn(col, options)).toBe(col)
    expect(query).not.toHaveBeenCalled()

    doc.documentElement.style.setProperty('--dsh-sidebar-width', '320px')
    now = 1
    expect(resolveCenterColumn(col, options)).toBe(col)
    expect(query).toHaveBeenCalledTimes(1)

    // The same fingerprint is cheap again; one style change causes one full
    // validation instead of turning later streaming mutations into queries.
    now = 2
    expect(resolveCenterColumn(col, options)).toBe(col)
    expect(query).toHaveBeenCalledTimes(1)
  })

  it('queries and adopts the replacement as soon as the cached column detaches', () => {
    const first = connectedColumn()
    const stale = first.col
    stale.remove()
    const { col: replacement, slot } = connectedColumn(first.doc)
    const query = vi.fn<() => Element | null>(() => slot)

    expect(resolveCenterColumn(stale, { document: first.doc, query, now: () => 1 })).toBe(replacement)
    expect(query).toHaveBeenCalledTimes(1)
  })

  it('queries when no column has been cached yet', () => {
    const { doc, col, slot } = connectedColumn()
    const query = vi.fn<() => Element | null>(() => slot)

    expect(resolveCenterColumn(null, { document: doc, query, now: () => 0 })).toBe(col)
    expect(query).toHaveBeenCalledTimes(1)
  })

  it('rejects a missing or detached query result', () => {
    const doc = document.implementation.createHTMLDocument()
    expect(resolveCenterColumn(null, { document: doc, query: () => null, now: () => 0 })).toBeUndefined()

    const detachedCol = doc.createElement('div')
    const detachedSlot = doc.createElement('div')
    detachedCol.append(detachedSlot)
    expect(resolveCenterColumn(null, {
      document: doc,
      query: () => detachedSlot,
      now: () => 1,
    })).toBeUndefined()
  })
})