"""Bốn màn chính và cách chuyển giữa chúng — R08-T10.

Dashboard và Lịch chỉ được dựng ở lần mở đầu tiên (dựng lười) — mở app không
phải trả giá cho hai màn có thể cả phiên không ai vào. ``_ensure_page`` là chỗ
duy nhất biết điều đó, nên mọi đường tới một trang đều phải đi qua ``_goto``.

Cùng kiểu mixin, xem ghi chú ở đầu ``nav_rail.py``.
"""
from __future__ import annotations

from PySide6.QtCore import Qt
from ...i18n import tr
from ..dashboard.dashboard_tab import DashboardTab
from ...ui.monitoring_tab import MonitoringTab
from ..scheduling.schedule_task_tab import ScheduleTaskTab



class PageRegistryMixin:
    def _page_index(self, widget) -> int:
        return self.pages.indexOf(widget)
    def _build_dashboard(self):
        d = DashboardTab(self.ctx)
        d.status_message.connect(self.statusBar().showMessage)
        self.dashboard = d
        return d
    def _build_schedule(self):
        s = ScheduleTaskTab(self.ctx, self.task_scheduler)
        s.status_message.connect(self.statusBar().showMessage)
        self.schedule = s
        return s
    def _build_monitoring(self):
        m = MonitoringTab(self.ctx, cowork=self.cowork, structure=self.structure,
                          task_scheduler=self.task_scheduler)
        m.status_message.connect(self.statusBar().showMessage)
        self.monitoring = m
        return m
    def _ensure_page(self, row: int) -> None:
        """Build a lazy nav page on first visit and swap it in for its placeholder."""
        if not (0 <= row < len(self._built)) or self._built[row]:
            return
        builder = self._nav_defs[row][2]
        if builder is None:
            return
        real = builder()
        placeholder = self._page_widgets[row]
        self.pages.insertWidget(row, real)     # placeholder shifts to row+1
        self.pages.removeWidget(placeholder)
        placeholder.deleteLater()
        self._page_widgets[row] = real
        self._built[row] = True
    def _page_index(self, widget) -> int:
        if widget is self.workspace:
            return self._ROW_WORKSPACE
        if self.dashboard is not None and widget is self.dashboard:
            return self._ROW_DASHBOARD
        if self.schedule is not None and widget is self.schedule:
            return self._ROW_SCHEDULE
        if self.monitoring is not None and widget is self.monitoring:
            return self._ROW_MONITORING
        return self.pages.indexOf(widget)
    def _goto(self, page: int, sub) -> None:
        self._ensure_page(page)                # build lazy page on first visit
        self.pages.setCurrentIndex(page)
        if page == self._ROW_WORKSPACE:
            self.workspace.refresh()           # re-list projects + threads on entry
        widget = self._page_widgets[page]
        if sub is not None and hasattr(widget, "select_subtab"):
            # Enforce the project gate here rather than at each entry point. A
            # greyed rail row cannot be clicked, but _goto is also reached from
            # RECENTS and from startup restore, and it used to open a sub-tab
            # the gate was holding shut — page shown, tab strip still hiding it.
            if hasattr(widget, "subtab_available") and not widget.subtab_available(sub):
                self.statusBar().showMessage(tr("app.nav.needs_project"), 4000)
            else:
                widget.select_subtab(sub)
        # Move the highlight with the content, however navigation was triggered —
        # a programmatic _goto used to leave it on whatever was clicked last.
        if not self._nav_building:
            self._select_nav_row(page, sub)
        self._update_dock_guard()
        # Switching pages updates which conversation is "current".
        self._refresh_history()