피파는 창 안에 남고, 죽은 페이지는 돌아와

    /// Puts `surface` in front. Pippa herself, while she is open, stays in
    /// the window under the page in front rather than leaving it: WebKit holds
    /// a page out of the window to a lower memory limit after about eight
    /// minutes and slows its timers (ENGINE-EVALUATION W10), and her
    /// conversation is the heaviest page Dad keeps. She sits at the bottom, so
    /// the page shown over her is simply added on top and taken away again.
    private func show(_ shown: NSView?) {
        let surface = shown ?? emptyPage
        guard surface !== shownSurface else { return }
        if shownSurface !== pippaSurfaceView || !pippaSurface.isOpen { shownSurface?.removeFromSuperview() }
        shownSurface = surface
        if pippaSurface.isOpen, surface !== pippaSurfaceView, pippaSurfaceView.superview !== pageContainer {
            pippaSurfaceView.frame = pageContainer.bounds
            pippaSurfaceView.autoresizingMask = [.width, .height]
            pageContainer.addSubview(pippaSurfaceView, positioned: .below, relativeTo: nil)
        }
        if surface.superview !== pageContainer {
            surface.frame = pageContainer.bounds
            surface.autoresizingMask = [.width, .height]
            pageContainer.addSubview(surface)
        }
        // The page takes the keys unless Dad is in the address field.
        if !toolbar.hasFocus { focusPage() }
    }

    public func pageProcessDidEnd(_ page: any EnginePage) {
        processEnded = true
        status.isLoading = false
        status.progress = 0
        status.isAudible = false
        window?.pageProcessEnded(self)
    }

    /// Loads the page again after its process ended, as Safari does, unless
    /// it did so less than a minute ago. True when it did.
    func recoverFromProcessEnd(now: Date = Date()) -> Bool {
        guard processEnded, page != nil else { return false }
        if let lastRecovery, now.timeIntervalSince(lastRecovery) < 60 { return false }
        lastRecovery = now
        reload()
        return true
    }

@MainActor
@Suite struct TabStateTests {
    /// A page in front whose process ends loads again by itself, as Safari
    /// does; one that ends again within the minute stays ended and says so.
    @Test func aPageInFrontComesBackOnceAMinute() {
        let bench = Bench()
        var recovered: [TabID] = []
        bench.window.onPageRecovered = { recovered.append($0.id) }
        let tab = bench.window.openTab(url: url("https://a.example/"))
        let page = bench.page(of: tab)!
        tab.pageProcessDidEnd(page)
        #expect(!tab.processEnded)
        #expect(page.reloads == 1)
        #expect(recovered == [tab.id])

        tab.pageProcessDidEnd(page)
        #expect(tab.processEnded)
        #expect(!tab.status.isLoading)
        #expect(page.reloads == 1)
        page.load(url("https://a.example/"))
        #expect(!tab.processEnded)
    }

    /// Behind, an ended page waits; it loads as Dad comes back to it.
    @Test func aPageBehindComesBackWhenChosen() {
        let bench = Bench()
        let behind = bench.window.openTab(url: url("https://a.example/"))
        bench.window.openTab(url: url("https://b.example/"))
        let page = bench.page(of: behind)!
        behind.pageProcessDidEnd(page)
        #expect(behind.processEnded)
        #expect(page.reloads == 0)
        bench.window.select(behind.id)
        #expect(!behind.processEnded)
        #expect(page.reloads == 1)
    }