import sqlite3
from pathlib import Path

import pytest

from corpus_mcp.database import (
    CorpusError,
    build_database,
    iter_chunks,
    read_corpus_info,
)


def test_indexes_supported_files_recursively(tmp_path: Path) -> None:
    source = tmp_path / "documents"
    nested = source / "nested"
    nested.mkdir(parents=True)
    (source / "root.TXT").write_text("Root text", encoding="utf-8-sig")
    (nested / "page.Md").write_text("Nested markdown", encoding="utf-8")
    (nested / "ignored.rst").write_text("Not indexed", encoding="utf-8")
    database = tmp_path / "output" / "corpus.sqlite"

    count = build_database(source, database, description="  Example corpus  ")

    assert count == 2
    info = read_corpus_info(database)
    assert info["description"] == "Example corpus"
    assert info["document_count"] == 2
    with sqlite3.connect(database) as connection:
        paths = [
            row[0]
            for row in connection.execute("SELECT path FROM documents ORDER BY path")
        ]
    assert paths == ["nested/page.Md", "root.TXT"]


def test_empty_file_is_recorded(tmp_path: Path) -> None:
    source = tmp_path / "documents"
    source.mkdir()
    (source / "empty.txt").write_text("", encoding="utf-8")
    database = tmp_path / "corpus.sqlite"

    assert build_database(source, database) == 1
    with sqlite3.connect(database) as connection:
        assert connection.execute("SELECT count(*) FROM documents").fetchone()[0] == 1
        assert connection.execute("SELECT count(*) FROM chunks").fetchone()[0] == 0


def test_rebuild_is_atomic_when_a_source_cannot_be_decoded(tmp_path: Path) -> None:
    source = tmp_path / "documents"
    source.mkdir()
    (source / "valid.txt").write_text("original", encoding="utf-8")
    database = tmp_path / "corpus.sqlite"
    build_database(source, database, description="Original")
    original_bytes = database.read_bytes()
    (source / "invalid.txt").write_bytes(b"\xff\xfe\xfa")

    with pytest.raises(CorpusError, match="invalid.txt"):
        build_database(source, database)

    assert database.read_bytes() == original_bytes
    assert read_corpus_info(database)["description"] == "Original"


def test_chunks_overlap_and_reconstruct_offsets() -> None:
    text = "paragraph one\n\n" + ("word " * 1_200) + "the end"
    chunks = list(iter_chunks(text))

    assert len(chunks) >= 2
    assert chunks[0][0] == 0
    assert chunks[-1][1] == len(text)
    for previous, current in zip(chunks, chunks[1:]):
        assert current[0] < previous[1]
        assert text[current[0] : current[1]] == current[2]


def test_rejects_non_directory_source(tmp_path: Path) -> None:
    source = tmp_path / "file.txt"
    source.write_text("text", encoding="utf-8")

    with pytest.raises(CorpusError, match="not a directory"):
        build_database(source, tmp_path / "corpus.sqlite")