import importlib
import time
import traceback

from gui.v2.infrastructure.page_registry import PAGE_REGISTRY


class Navigator:
    def __init__(self, page_stack, custom_window):
        self.page_stack = page_stack
        self.custom_window = custom_window
        self._instances = {}

    def navigate(self, name):
        page = self._instances.get(name)
        if page is None:
            if name not in PAGE_REGISTRY:
                self._warn_not_migrated(name)
                return
            module_path, class_name = PAGE_REGISTRY[name]
            module = importlib.import_module(module_path)
            cls = getattr(module, class_name)
            page = cls(self.page_stack, self.custom_window)
            self.page_stack.addWidget(page)
            self._instances[name] = page
        self.page_stack.setCurrentIndex(self.page_stack.indexOf(page))

    def preload(self, name):
        if name in self._instances:
            print(f"[preload] {name:30s} SKIP   (already cached)", flush=True)
            return False
        if name not in PAGE_REGISTRY:
            print(f"[preload] {name:30s} SKIP   (not in registry)", flush=True)
            return False
        module_path, class_name = PAGE_REGISTRY[name]
        print(f"[preload] {name:30s} LOAD   {module_path}.{class_name}", flush=True)
        t0 = time.perf_counter()
        try:
            module = importlib.import_module(module_path)
            cls = getattr(module, class_name)
            page = cls(self.page_stack, self.custom_window)
            self.page_stack.addWidget(page)
            self._instances[name] = page
            dt_ms = (time.perf_counter() - t0) * 1000.0
            print(f"[preload] {name:30s} OK     ({dt_ms:6.1f} ms, "
                  f"cached={len(self._instances)}, stack_size={self.page_stack.count()})",
                  flush=True)
            return True
        except Exception as e:
            dt_ms = (time.perf_counter() - t0) * 1000.0
            print(f"[preload] {name:30s} FAIL   ({dt_ms:6.1f} ms) "
                  f"{type(e).__name__}: {e}", flush=True)
            traceback.print_exc()
            from core.errors.logger import logger as core_logger
            core_logger.warning(f"Background preload failed for '{name}': "
                                f"{type(e).__name__}: {e}")
            return False

    def get_cached(self, name):
        return self._instances.get(name)

    def _warn_not_migrated(self, name):
        try:
            self.custom_window.update_status(f"Page '{name}' not migrated yet.")
        except Exception:
            pass