"""Unit tests for src/tools/generate_splits.py"""
import pytest
from pathlib import Path

from src.tools.generate_splits import generate_splits_txt, SPLITS


@pytest.fixture
def splits_dir(tmp_path):
    """Create a minimal splits directory with label files."""
    for split in ["train", "val"]:
        label_dir = tmp_path / split / "labels"
        label_dir.mkdir(parents=True)
        for i in range(3):
            (label_dir / f"img_{split}_{i:03d}.txt").write_text("0 0.5 0.5 0.1 0.1\n")
    # leave "test" absent intentionally
    return tmp_path


class TestGenerateSplitsTxt:
    def test_creates_output_file(self, splits_dir, tmp_path):
        out = tmp_path / "output" / "split.txt"
        out.parent.mkdir()
        generate_splits_txt(splits_dir, out)
        assert out.exists()

    def test_entries_have_correct_format(self, splits_dir, tmp_path):
        out = tmp_path / "split.txt"
        generate_splits_txt(splits_dir, out)
        lines = [l for l in out.read_text().splitlines() if l]
        for line in lines:
            parts = line.split("/")
            assert parts[0] in SPLITS, f"unexpected split name in: {line}"
            assert parts[1] == "labels"
            assert parts[2].endswith(".txt")

    def test_entry_count_matches_label_files(self, splits_dir, tmp_path):
        out = tmp_path / "split.txt"
        generate_splits_txt(splits_dir, out)
        lines = [l for l in out.read_text().splitlines() if l]
        # 3 train + 3 val = 6; test was absent
        assert len(lines) == 6

    def test_train_entries_come_before_val(self, splits_dir, tmp_path):
        out = tmp_path / "split.txt"
        generate_splits_txt(splits_dir, out)
        lines = [l for l in out.read_text().splitlines() if l]
        splits_seen = [l.split("/")[0] for l in lines]
        train_indices = [i for i, s in enumerate(splits_seen) if s == "train"]
        val_indices   = [i for i, s in enumerate(splits_seen) if s == "val"]
        assert max(train_indices) < min(val_indices)

    def test_missing_split_dir_is_skipped_gracefully(self, tmp_path):
        # empty directory — no split sub-dirs at all
        out = tmp_path / "split.txt"
        generate_splits_txt(tmp_path, out)
        lines = [l for l in out.read_text().splitlines() if l]
        assert lines == []

    def test_entries_are_sorted_within_split(self, splits_dir, tmp_path):
        out = tmp_path / "split.txt"
        generate_splits_txt(splits_dir, out)
        lines = [l for l in out.read_text().splitlines() if l]
        train_lines = [l for l in lines if l.startswith("train/")]
        assert train_lines == sorted(train_lines)