"""
Edge case tests for calculate_duration() in web/models/database.py.

These tests target the dateutil.parser fallback paths and timezone
handling that are NOT covered by the existing test_database.py.
"""

from unittest.mock import patch
from datetime import datetime, timezone, timedelta


class TestDateutilFallbackPaths:
    """Tests for the dateutil.parser.parse fallback code paths."""

    def test_completed_at_dateutil_fallback(self):
        """Weird completed_at format that fails fromisoformat but dateutil can parse."""
        from local_deep_research.web.models.database import calculate_duration

        created_at = "2025-01-01T10:00:00+00:00"
        # Month name format — fromisoformat fails, dateutil parses it
        completed_at = "Jan 1, 2025 10:05:00 UTC"

        result = calculate_duration(created_at, completed_at)
        assert result is not None
        assert result == 300  # 5 minutes

    def test_created_at_dateutil_fallback(self):
        """Weird created_at format that fails standard parsing but dateutil can handle."""
        from local_deep_research.web.models.database import calculate_duration

        created_at = "Jan 1, 2025 10:00:00 UTC"
        completed_at = "2025-01-01T10:02:00+00:00"

        result = calculate_duration(created_at, completed_at)
        assert result is not None
        assert result == 120  # 2 minutes

    def test_created_at_completely_unparseable_returns_none(self):
        """Completely unparseable created_at → returns None."""
        from local_deep_research.web.models.database import calculate_duration

        result = calculate_duration(
            "not-a-date-at-all", "2025-01-01T10:00:00+00:00"
        )
        assert result is None

    def test_completed_at_unparseable_falls_back_to_now(self):
        """Completely unparseable completed_at → falls back to current time."""
        from local_deep_research.web.models.database import calculate_duration

        now = datetime.now(timezone.utc)
        created_at = (now - timedelta(seconds=60)).isoformat()

        # Patch dateutil.parser.parse to fail when called for the completed_at
        with patch(
            "dateutil.parser.parse", side_effect=Exception("Cannot parse")
        ):
            result = calculate_duration(created_at, "completely-invalid-!!!")
            # Falls back to datetime.now(UTC), so duration ≈ 60s
            assert result is not None
            assert 55 <= result <= 70


class TestTimezoneHandling:
    """Tests for timezone-aware vs timezone-naive mixing."""

    def test_timezone_offset_format(self):
        """Timestamps with +HH:MM offset are handled."""
        from local_deep_research.web.models.database import calculate_duration

        created_at = "2025-01-01T10:00:00+05:30"
        completed_at = "2025-01-01T10:30:00+05:30"

        result = calculate_duration(created_at, completed_at)
        assert result == 1800  # 30 minutes

    def test_different_timezone_offsets(self):
        """Timestamps with different timezone offsets are normalized."""
        from local_deep_research.web.models.database import calculate_duration

        # Same absolute moment, different offsets
        created_at = "2025-01-01T10:00:00+00:00"
        completed_at = "2025-01-01T12:00:00+02:00"  # Same as 10:00 UTC

        result = calculate_duration(created_at, completed_at)
        assert result == 0  # Same instant

    def test_negative_timezone_offset(self):
        """Negative timezone offset works correctly."""
        from local_deep_research.web.models.database import calculate_duration

        created_at = "2025-01-01T10:00:00-05:00"  # UTC 15:00
        completed_at = "2025-01-01T16:00:00+00:00"  # UTC 16:00

        result = calculate_duration(created_at, completed_at)
        assert result == 3600  # 1 hour difference


class TestSpaceSeparatedFormats:
    """Tests for space-separated timestamp formats."""

    def test_space_separated_with_microseconds_and_tz(self):
        """Space-separated format with microseconds and timezone."""
        from local_deep_research.web.models.database import calculate_duration

        # Include timezone to avoid naive datetime issues with astimezone
        created_at = "2025-01-01 10:00:00.123456+00:00"
        completed_at = "2025-01-01 10:01:00.654321+00:00"

        result = calculate_duration(created_at, completed_at)
        assert result is not None
        assert result == 60 or result == 61

    def test_space_separated_without_microseconds_and_tz(self):
        """Space-separated format without microseconds, with timezone."""
        from local_deep_research.web.models.database import calculate_duration

        created_at = "2025-01-01 10:00:00+00:00"
        completed_at = "2025-01-01 10:05:00+00:00"

        result = calculate_duration(created_at, completed_at)
        assert result == 300  # 5 minutes

    def test_space_to_t_replacement_fallback(self):
        """Space-separated with timezone falls back to replace(' ', 'T')."""
        from local_deep_research.web.models.database import calculate_duration

        # This has timezone info but no T separator — triggers the replace fallback
        created_at = "2025-01-01 10:00:00+00:00"
        completed_at = "2025-01-01 10:03:00+00:00"

        result = calculate_duration(created_at, completed_at)
        assert result == 180  # 3 minutes

    def test_iso_with_explicit_utc_offset(self):
        """ISO format with explicit UTC offset."""
        from local_deep_research.web.models.database import calculate_duration

        created_at = "2025-01-01T10:00:00+00:00"
        completed_at = "2025-01-01T10:10:00+00:00"

        result = calculate_duration(created_at, completed_at)
        assert result == 600  # 10 minutes