"""Tests for :class:`IsoTreeModel` root-handling and lazy fetch.

The model root's children are the entries of the ISO ``/`` directory,
surfaced directly so the view displays them without manual expansion.
rowCount() returns 0 for an unloaded root and lets Qt drive
canFetchMore()/fetchMore(); index_from_path('/') yields the invalid
model-root index; refresh_parent('/') drops and re-fetches the virtual
root without crashing.
"""

from __future__ import annotations

import os
import sys
from io import BytesIO
from pathlib import Path

import pytest

PySide6 = pytest.importorskip("PySide6")
pycdlib = pytest.importorskip("pycdlib")

from PySide6.QtCore import QModelIndex
from PySide6.QtWidgets import QApplication

ROOT = Path(__file__).resolve().parent.parent
sys.path.insert(0, str(ROOT))


@pytest.fixture(scope="module")
def qapp():
    os.environ.setdefault("QT_QPA_PLATFORM", "offscreen")
    app = QApplication.instance() or QApplication([])
    yield app


@pytest.fixture
def tiny_iso_path(tmp_path):
    """Create a small ISO with two files and one subdirectory at /."""
    iso_path = tmp_path / "tiny.iso"
    iso = pycdlib.PyCdlib()
    iso.new()
    iso.add_fp(BytesIO(b"hello"), 5, "/HELLO.TXT;1")
    iso.add_fp(BytesIO(b"world"), 5, "/WORLD.TXT;1")
    iso.add_directory("/SUBDIR")
    iso.add_fp(BytesIO(b"sub"), 3, "/SUBDIR/INSIDE.TXT;1")
    iso.write(str(iso_path))
    iso.close()
    return str(iso_path)


@pytest.fixture
def open_handler(tiny_iso_path):
    from iso_scalpel.iso_handler import IsoHandler
    h = IsoHandler()
    h.open(tiny_iso_path)
    yield h
    h.close()


# ==========================================================================
# IsoTreeModel: rowCount(QModelIndex()) must reflect / contents directly
# ==========================================================================
class TestModelRootShowsDirectoryContents:
    """The model root's children are the entries of the ISO ``/`` directory.

    rowCount(QModelIndex()) reflects the count of root entries directly --
    there is no virtual ``"/"`` placeholder row that the user must expand.
    """

    def test_rowCount_of_model_root_is_zero_before_fetch(self, open_handler, qapp):
        from iso_scalpel.iso_model import IsoTreeModel
        m = IsoTreeModel(open_handler)
        # Before fetchMore is called, the root isn't loaded -- rowCount
        # must return 0 (not 1) so the view triggers canFetchMore/fetchMore.
        assert m.rowCount(QModelIndex()) == 0

    def test_canFetchMore_returns_true_for_unloaded_root(self, open_handler, qapp):
        from iso_scalpel.iso_model import IsoTreeModel
        m = IsoTreeModel(open_handler)
        assert m.canFetchMore(QModelIndex()) is True

    def test_fetchMore_populates_root_children(self, open_handler, qapp):
        from iso_scalpel.iso_model import IsoTreeModel
        m = IsoTreeModel(open_handler)
        m.fetchMore(QModelIndex())
        # The ISO has 3 entries at /: HELLO.TXT, WORLD.TXT, SUBDIR
        assert m.rowCount(QModelIndex()) == 3

    def test_root_children_names_are_correct(self, open_handler, qapp):
        from iso_scalpel.iso_model import IsoTreeModel
        m = IsoTreeModel(open_handler)
        m.fetchMore(QModelIndex())
        names = [m.index(r, 0, QModelIndex()).data() for r in range(m.rowCount(QModelIndex()))]
        assert set(names) == {"HELLO.TXT", "WORLD.TXT", "SUBDIR"}

    def test_no_infinite_recursion_in_rowCount(self, open_handler, qapp):
        """rowCount() must never call fetchMore().

        Calling fetchMore() from inside rowCount() recurses through
        beginInsertRows and blows the stack.  The contract is: rowCount()
        returns 0 for an unloaded root; Qt then calls canFetchMore() /
        fetchMore() on its own schedule.
        """
        from iso_scalpel.iso_model import IsoTreeModel
        m = IsoTreeModel(open_handler)
        # Calling rowCount on an unloaded root must return immediately
        # without recursing.
        result = m.rowCount(QModelIndex())
        assert isinstance(result, int)


# ==========================================================================
# index_from_path: "/" maps to the model root (invalid QModelIndex)
# ==========================================================================
class TestIndexFromPath:
    """``index_from_path("/")`` must return the model root (an invalid
    :class:`QModelIndex`) -- not ``createIndex(0, 0, self._root)`` -- so
    that the view's default root index correctly shows "/" contents.
    """

    def test_root_path_returns_invalid_index(self, open_handler, qapp):
        from iso_scalpel.iso_model import IsoTreeModel
        m = IsoTreeModel(open_handler)
        idx = m.index_from_path("/")
        assert not idx.isValid(), (
            "index_from_path('/') should return the model root "
            "(invalid QModelIndex), not a createIndex"
        )

    def test_subdir_path_returns_valid_index(self, open_handler, qapp):
        from iso_scalpel.iso_model import IsoTreeModel
        m = IsoTreeModel(open_handler)
        m.fetchMore(QModelIndex())
        idx = m.index_from_path("/SUBDIR")
        assert idx.isValid()
        assert idx.data() == "SUBDIR"

    def test_nonexistent_path_returns_invalid_index(self, open_handler, qapp):
        from iso_scalpel.iso_model import IsoTreeModel
        m = IsoTreeModel(open_handler)
        m.fetchMore(QModelIndex())
        idx = m.index_from_path("/DOES_NOT_EXIST")
        assert not idx.isValid()


# ==========================================================================
# refresh_parent: handles the root path correctly
# ==========================================================================
class TestRefreshParent:
    """``refresh_parent("/")`` must not crash when the model's
    ``index_from_path("/")`` returns an invalid index.
    """

    def test_refresh_parent_root_does_not_crash(self, open_handler, qapp):
        from iso_scalpel.iso_model import IsoTreeModel
        m = IsoTreeModel(open_handler)
        m.fetchMore(QModelIndex())
        # Should not raise.
        m.refresh_parent("/")
        # After refresh, root should be unloaded again.
        assert m.rowCount(QModelIndex()) == 0
        # Re-fetching should still work.
        m.fetchMore(QModelIndex())
        assert m.rowCount(QModelIndex()) == 3

    def test_refresh_parent_subdir(self, open_handler, qapp):
        from iso_scalpel.iso_model import IsoTreeModel
        m = IsoTreeModel(open_handler)
        m.fetchMore(QModelIndex())
        subdir_idx = m.index_from_path("/SUBDIR")
        assert subdir_idx.isValid()
        m.fetchMore(subdir_idx)
        assert m.rowCount(subdir_idx) == 1  # INSIDE.TXT
        m.refresh_parent("/SUBDIR")
        # After refresh, subdir is unloaded.
        assert m.rowCount(subdir_idx) == 0


# ==========================================================================
# End-to-end: IsoPane displays entries after open
# ==========================================================================
class TestIsoPaneShowsEntriesAfterOpen:
    """End-to-end regression: after ``handler.open()`` and
    ``pane.refresh()``, the ISO pane's view must report a non-zero
    row count for the model root.
    """

    def test_pane_shows_entries_after_refresh(self, open_handler, qapp):
        from iso_scalpel.config import Settings
        from iso_scalpel.widgets.iso_pane import IsoPane
        s = Settings()
        pane = IsoPane(open_handler, s)
        pane.refresh()
        # Force the view's model to fetch the root children.
        pane.view.model().fetchMore(pane.view.rootIndex())
        qapp.processEvents()
        # The view's root index is the model root (invalid QModelIndex);
        # its row count must be 3 (HELLO.TXT, WORLD.TXT, SUBDIR).
        rc = pane.view.model().rowCount(pane.view.rootIndex())
        assert rc == 3, f"ISO pane should show 3 entries, got {rc}"

    def test_pane_breadcrumb_shows_iso_filename_after_open(self, open_handler, qapp):
        """The breadcrumb bar at the top of the ISO pane shows the ISO
        filename after opening.  The pane must reach the
        ``_rebuild_breadcrumbs`` call path on refresh.
        """
        from iso_scalpel.config import Settings
        from iso_scalpel.widgets.iso_pane import IsoPane
        s = Settings()
        pane = IsoPane(open_handler, s)
        pane.refresh()
        # The breadcrumb frame must have at least one child widget (the
        # root button showing the ISO filename).
        assert pane._crumb_layout.count() > 0