"""Config snapshot unified diff (GetConfig history)."""

from __future__ import annotations

from datetime import UTC, datetime, timedelta

from shelly_manager.core.config_snapshot_diff import (
    pick_older_newer,
    settings_unified_diff_text,
    sort_snapshots_chronologically,
)
from shelly_manager.core.models import ConfigSnapshot


def _snap(
    *,
    sid: str,
    created: datetime,
    label: str,
    settings: dict,
) -> ConfigSnapshot:
    return ConfigSnapshot(
        id=sid,
        device_id="DEV",
        created_at=created,
        label=label,
        settings=settings,
    )


def test_sort_snapshots_chronologically_oldest_first() -> None:
    t0 = datetime(2026, 3, 20, 0, 37, tzinfo=UTC)
    t1 = datetime(2026, 3, 20, 0, 42, tzinfo=UTC)
    a = _snap(sid="a", created=t1, label="newer", settings={})
    b = _snap(sid="b", created=t0, label="older", settings={})
    out = sort_snapshots_chronologically([a, b])
    assert [x.label for x in out] == ["older", "newer"]


def test_pick_older_newer_swaps_when_user_picks_newer_as_a() -> None:
    """Oldest-first list: index 0 older, index 1 newer — if user picks A=1 B=0, still get older→newer."""
    t0 = datetime(2026, 3, 20, 0, 37, tzinfo=UTC)
    t1 = datetime(2026, 3, 20, 0, 42, tzinfo=UTC)
    snaps = [
        _snap(sid="b", created=t0, label="older", settings={"x": 1}),
        _snap(sid="a", created=t1, label="newer", settings={"x": 2}),
    ]
    older, newer = pick_older_newer(snaps, 1, 0)
    assert older.label == "older"
    assert newer.label == "newer"


def test_settings_unified_diff_text_has_line_separated_structure() -> None:
    """Regression: diff must contain newlines so each +/- line is separate (not one wrapped blob)."""
    old = {"ble": {"enable": True}}
    new = {"ble": {"enable": False}}
    text = settings_unified_diff_text(old, new, fromfile="older/settings.json", tofile="newer/settings.json")
    assert text.count("\n") >= 4
    lines = text.splitlines()
    assert lines[0].startswith("--- ")
    assert lines[1].startswith("+++ ")
    assert any(line.startswith("@@") for line in lines)
    # Every content/hunk line must be its own line (no embedded @@ mid-line)
    for line in lines:
        assert "\n" not in line
    minus_lines = [ln for ln in lines if ln.startswith("-") and not ln.startswith("---")]
    plus_lines = [ln for ln in lines if ln.startswith("+") and not ln.startswith("+++")]
    assert minus_lines
    assert plus_lines


def test_settings_unified_diff_identical_empty() -> None:
    cfg = {"a": 1}
    assert settings_unified_diff_text(cfg, cfg) == ""


def test_pick_older_newer_same_timestamp_tie_break() -> None:
    t = datetime(2026, 3, 20, 12, 0, tzinfo=UTC)
    s1 = _snap(sid="aaa", created=t, label="first", settings={})
    s2 = _snap(sid="zzz", created=t, label="second", settings={})
    snaps = sort_snapshots_chronologically([s2, s1])
    older, newer = pick_older_newer(snaps, 0, 1)
    assert older.id == "aaa"
    assert newer.id == "zzz"