"""
Regression test for backward navigation onto the cover page.

Going forward off the cover and then back again must return to block_index=0.

Previously it left current_position at the first content block (1) while flagging
the cover as displayed, so the cover had two different internal representations.
Since current_position is what gets persisted, saving while on the cover reopened
the book past it. Fixed in pyWebLayout's EreaderLayoutManager.previous_page().
"""

import unittest
import tempfile
import shutil
from pathlib import Path

from dreader.application import EbookReader


class TestBackwardNavigationBug(unittest.TestCase):
    """Minimal reproduction of backward navigation bug"""

    def setUp(self):
        """Set up test environment"""
        self.temp_dir = tempfile.mkdtemp()
        self.epub_path = "tests/data/test.epub"

        if not Path(self.epub_path).exists():
            self.skipTest(f"Test EPUB not found at {self.epub_path}")

    def tearDown(self):
        """Clean up test environment"""
        shutil.rmtree(self.temp_dir, ignore_errors=True)

    def test_minimal_backward_navigation_bug(self):
        """
        MINIMAL CASE:

        1. Start at block_index=0
        2. Go forward once (to block_index=1)
        3. Go backward once
        4. Should land back at block_index=0
        """
        reader = EbookReader(
            page_size=(800, 1000),
            bookmarks_dir=self.temp_dir,
            buffer_size=0
        )

        reader.load_epub(self.epub_path)

        # Starting position
        pos_start = reader.manager.current_position.copy()
        print(f"\n1. Starting at block_index={pos_start.block_index}")
        self.assertEqual(pos_start.block_index, 0, "Should start at block 0")

        # Go forward
        reader.next_page()
        pos_forward = reader.manager.current_position.copy()
        print(f"2. After next_page(): block_index={pos_forward.block_index}")
        self.assertEqual(pos_forward.block_index, 1, "Should be at block 1")

        # Go backward
        reader.previous_page()
        pos_final = reader.manager.current_position.copy()
        print(f"3. After previous_page(): block_index={pos_final.block_index}")

        print(f"\nEXPECTED: block_index=0")
        print(f"ACTUAL:   block_index={pos_final.block_index}")

        self.assertEqual(
            pos_final.block_index,
            0,
            "Backward navigation from block 1 should return to block 0"
        )

        reader.close()


if __name__ == '__main__':
    unittest.main()