"""Tests for hameter.cost_state persistence."""

import json

from hameter.cost_state import load_cost_state, save_cost_state


class TestCostStatePersistence:
    """Tests for load/save of cost state."""

    def test_save_and_load(self, tmp_path):
        path = str(tmp_path / "cost_state.json")
        states = {
            "123": {
                "cumulative_cost": 156.78,
                "last_calibrated_reading": 59830.5,
                "billing_period_start": "2026-03-01T00:00:00Z",
                "last_updated": "2026-03-05T14:30:00Z",
                "fixed_charges_applied": 9.65,
            }
        }
        save_cost_state(states, path)
        loaded = load_cost_state(path)
        assert loaded["123"]["cumulative_cost"] == 156.78
        assert loaded["123"]["last_calibrated_reading"] == 59830.5
        assert loaded["123"]["fixed_charges_applied"] == 9.65

    def test_load_nonexistent_returns_empty(self, tmp_path):
        path = str(tmp_path / "nonexistent.json")
        result = load_cost_state(path)
        assert result == {}

    def test_load_corrupt_returns_empty(self, tmp_path):
        path = str(tmp_path / "cost_state.json")
        with open(path, "w") as f:
            f.write("not json")
        result = load_cost_state(path)
        assert result == {}

    def test_creates_parent_directory(self, tmp_path):
        path = str(tmp_path / "subdir" / "cost_state.json")
        save_cost_state({"1": {"cumulative_cost": 0}}, path)
        loaded = load_cost_state(path)
        assert "1" in loaded

    def test_no_temp_file_left(self, tmp_path):
        path = str(tmp_path / "cost_state.json")
        save_cost_state({"1": {"cumulative_cost": 10.0}}, path)
        files = list(tmp_path.iterdir())
        assert len(files) == 1
        assert files[0].name == "cost_state.json"

    def test_multiple_meters(self, tmp_path):
        path = str(tmp_path / "cost_state.json")
        states = {
            "111": {"cumulative_cost": 50.0, "last_calibrated_reading": 1000.0},
            "222": {"cumulative_cost": 25.0, "last_calibrated_reading": 500.0},
        }
        save_cost_state(states, path)
        loaded = load_cost_state(path)
        assert len(loaded) == 2
        assert loaded["111"]["cumulative_cost"] == 50.0
        assert loaded["222"]["cumulative_cost"] == 25.0

    def test_atomic_write_format(self, tmp_path):
        path = str(tmp_path / "cost_state.json")
        states = {"123": {"cumulative_cost": 42.0}}
        save_cost_state(states, path)
        with open(path) as f:
            raw = f.read()
        # Should be pretty-printed JSON with trailing newline
        assert raw.endswith("\n")
        parsed = json.loads(raw)
        assert parsed == states