"""Tests for the data extraction module."""

import pytest
import pandas as pd
from pathlib import Path

from disk_checker.core.extractor import load_latency_csv


class TestLoadLatencyCsv:
    """Tests for load_latency_csv function."""

    def test_load_valid_csv(self, sample_csv_path):
        """Test loading a valid fio CSV file."""
        df = load_latency_csv(str(sample_csv_path))
        assert not df.empty
        assert "metric" in df.columns
        assert "latency_ns" in df.columns
        assert "count" in df.columns

    def test_returns_long_format(self, sample_csv_path):
        """Test that output is in long format with metric column."""
        df = load_latency_csv(str(sample_csv_path))
        metrics = df["metric"].unique()
        assert "read_clat" in metrics

    def test_empty_csv_raises(self, empty_csv_path):
        """Test that empty CSV raises ValueError."""
        with pytest.raises(ValueError, match="no metric had any numeric count data"):
            load_latency_csv(str(empty_csv_path))

    def test_invalid_format_raises(self, invalid_csv_path):
        """Test that invalid CSV format raises ValueError."""
        with pytest.raises(ValueError):
            load_latency_csv(str(invalid_csv_path))

    def test_missing_nsec_column_raises(self, tmp_path):
        """Test that missing nsec column raises ValueError."""
        csv_content = "col1,col2\n1,2\n"
        path = tmp_path / "invalid.csv"
        path.write_text(csv_content)
        with pytest.raises(ValueError, match="expected first column to be 'nsec'"):
            load_latency_csv(str(path))


@pytest.fixture
def sample_csv_path(tmp_path):
    """Create a sample CSV file for testing."""
    csv_content = """nsec,read_clat_ns_count,read_clat_ns_cumulative,read_clat_ns_percentile
19791872,1,1,0.00016775708773695687
22413312,4,5,0.0008387854386847844
22675456,9,14,0.0023485992283173965
"""
    path = tmp_path / "test.csv"
    path.write_text(csv_content)
    return path


@pytest.fixture
def empty_csv_path(tmp_path):
    """Create an empty CSV file for testing."""
    path = tmp_path / "empty.csv"
    path.write_text("nsec\n")
    return path


@pytest.fixture
def invalid_csv_path(tmp_path):
    """Create an invalid CSV file for testing."""
    path = tmp_path / "invalid.csv"
    path.write_text("col1,col2\n1,2\n")
    return path