"""
Unit-Tests für mailmerge.services.preview.

LibreOffice wird gemockt – die Tests prüfen nur die Logik:
CSV-Parsing, Header-Validierung, Fehlerpfade, Result-Aufbau.
"""
from __future__ import annotations

import io
from pathlib import Path
from unittest.mock import patch

import pytest

from mailmerge.services.preview import (
    PreviewError,
    PreviewResult,
    _read_first_row,
    build_preview,
)
from mailmerge.tests.conftest import (
    CSV_EXTRA_COLUMN,
    CSV_MISSING_COLUMN,
    CSV_NO_DATA,
    CSV_NO_HEADER,
    CSV_VALID,
)


# ---------------------------------------------------------------------------
# _read_first_row
# ---------------------------------------------------------------------------

class TestReadFirstRow:
    def test_reads_header_and_first_row(self):
        f = io.BytesIO(CSV_VALID.encode("utf-8"))
        columns, row = _read_first_row(f)

        assert columns == ["anrede_brief", "nachname", "vorname", "ort"]
        assert row["nachname"] == "Huber"
        assert row["vorname"] == "Andrea"
        assert row["ort"] == "Eisenstadt"

    def test_strips_utf8_bom(self):
        """CSV mit BOM darf nicht zu '\\ufeffanrede_brief' als erstem Header führen."""
        f = io.BytesIO(("\ufeff" + CSV_VALID).encode("utf-8"))
        columns, _ = _read_first_row(f)
        assert columns[0] == "anrede_brief"

    def test_accepts_path(self, tmp_path):
        p = tmp_path / "r.csv"
        p.write_text(CSV_VALID, encoding="utf-8")
        columns, row = _read_first_row(p)
        assert row["nachname"] == "Huber"
        assert "ort" in columns

    def test_no_header_raises(self):
        f = io.BytesIO(CSV_NO_HEADER.encode("utf-8"))
        with pytest.raises(PreviewError, match="keine Header"):
            _read_first_row(f)

    def test_no_data_row_raises(self):
        f = io.BytesIO(CSV_NO_DATA.encode("utf-8"))
        with pytest.raises(PreviewError, match="keine Datenzeile"):
            _read_first_row(f)


# ---------------------------------------------------------------------------
# build_preview – Header-Validierung
# ---------------------------------------------------------------------------

class TestBuildPreviewValidation:
    def test_missing_column_is_reported(self, docx_file_on_disk):
        csv_buf = io.BytesIO(CSV_MISSING_COLUMN.encode("utf-8"))
        with pytest.raises(PreviewError, match="fehlen aber als Spalte"):
            build_preview(docx_file_on_disk, csv_buf)

    def test_missing_column_lists_specific_name(self, docx_file_on_disk):
        csv_buf = io.BytesIO(CSV_MISSING_COLUMN.encode("utf-8"))
        with pytest.raises(PreviewError) as excinfo:
            build_preview(docx_file_on_disk, csv_buf)
        assert "ort" in str(excinfo.value)


# ---------------------------------------------------------------------------
# build_preview – Happy Path (mit gemocktem LibreOffice)
# ---------------------------------------------------------------------------

FAKE_PDF_BYTES = b"%PDF-1.4 fake test pdf"


@pytest.fixture
def patched_libreoffice(monkeypatch, tmp_path):
    """Ersetzt docx_to_pdf durch eine Funktion, die eine Dummy-PDF-Datei
    in das Out-Dir legt und deren Pfad zurückgibt."""
    def fake_docx_to_pdf(docx_path: Path, out_dir: Path) -> Path:
        out_dir.mkdir(parents=True, exist_ok=True)
        pdf_path = out_dir / (docx_path.stem + ".pdf")
        pdf_path.write_bytes(FAKE_PDF_BYTES)
        return pdf_path

    monkeypatch.setattr(
        "mailmerge.services.preview.docx_to_pdf", fake_docx_to_pdf
    )


class TestBuildPreviewHappyPath:
    def test_returns_preview_result(self, docx_file_on_disk, patched_libreoffice):
        csv_buf = io.BytesIO(CSV_VALID.encode("utf-8"))
        result = build_preview(docx_file_on_disk, csv_buf)

        assert isinstance(result, PreviewResult)
        assert result.pdf_bytes == FAKE_PDF_BYTES

    def test_first_row_is_used(self, docx_file_on_disk, patched_libreoffice):
        csv_buf = io.BytesIO(CSV_VALID.encode("utf-8"))
        result = build_preview(docx_file_on_disk, csv_buf)

        assert result.used_row["nachname"] == "Huber"
        assert result.used_row["vorname"] == "Andrea"

    def test_placeholders_are_listed(
        self, docx_file_on_disk, patched_libreoffice, template_placeholders
    ):
        csv_buf = io.BytesIO(CSV_VALID.encode("utf-8"))
        result = build_preview(docx_file_on_disk, csv_buf)
        assert set(result.placeholders) == set(template_placeholders)

    def test_extra_columns_are_reported(self, docx_file_on_disk, patched_libreoffice):
        csv_buf = io.BytesIO(CSV_EXTRA_COLUMN.encode("utf-8"))
        result = build_preview(docx_file_on_disk, csv_buf)

        assert "personalnr" in result.extra_columns
        assert result.missing_columns == []

    def test_calls_libreoffice_exactly_once(
        self, docx_file_on_disk, monkeypatch, tmp_path
    ):
        """Sicherstellen, dass auch wirklich nur EIN Render-Vorgang läuft."""
        calls = []

        def fake_docx_to_pdf(docx_path: Path, out_dir: Path) -> Path:
            calls.append(docx_path)
            out_dir.mkdir(parents=True, exist_ok=True)
            pdf_path = out_dir / (docx_path.stem + ".pdf")
            pdf_path.write_bytes(FAKE_PDF_BYTES)
            return pdf_path

        monkeypatch.setattr(
            "mailmerge.services.preview.docx_to_pdf", fake_docx_to_pdf
        )

        csv_buf = io.BytesIO(CSV_VALID.encode("utf-8"))
        build_preview(docx_file_on_disk, csv_buf)
        assert len(calls) == 1


# ---------------------------------------------------------------------------
# build_preview – LibreOffice-Fehler propagieren
# ---------------------------------------------------------------------------

class TestBuildPreviewLibreOfficeFailure:
    def test_runtime_error_bubbles_up(self, docx_file_on_disk, monkeypatch):
        def fake_docx_to_pdf(docx_path, out_dir):
            raise RuntimeError("LibreOffice ist abgestürzt")

        monkeypatch.setattr(
            "mailmerge.services.preview.docx_to_pdf", fake_docx_to_pdf
        )

        csv_buf = io.BytesIO(CSV_VALID.encode("utf-8"))
        with pytest.raises(RuntimeError, match="LibreOffice"):
            build_preview(docx_file_on_disk, csv_buf)