"""
Shared pytest fixtures for doc-service tests.

Uses an in-memory SQLite database so tests run without a real PostgreSQL.
The DATA_DIR is overridden to a tmp directory per test session.
The AI provider is mocked so tests never hit a real endpoint.
"""
import io
import struct
import zlib
from pathlib import Path
from typing import AsyncGenerator
from unittest.mock import AsyncMock, patch

import pytest
import pytest_asyncio
from httpx import ASGITransport, AsyncClient
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine

import app.models  # noqa: F401 — registers all ORM classes
from app.database import Base, get_db
from app.main import app

# ── Test database ──────────────────────────────────────────────────────────────

TEST_DB_URL = "sqlite+aiosqlite:///:memory:"

_engine = create_async_engine(TEST_DB_URL, connect_args={"check_same_thread": False})
_TestSessionLocal = async_sessionmaker(_engine, expire_on_commit=False)


@pytest_asyncio.fixture(scope="session", autouse=True)
async def create_tables():
    """Create all tables once per test session."""
    async with _engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
    yield
    async with _engine.begin() as conn:
        await conn.run_sync(Base.metadata.drop_all)


@pytest_asyncio.fixture
async def db_session() -> AsyncGenerator[AsyncSession, None]:
    """Provide a transactional test DB session that is rolled back after each test."""
    async with _engine.begin() as conn:
        async with AsyncSession(conn) as session:
            yield session
            await conn.rollback()


# ── Override get_db ────────────────────────────────────────────────────────────

async def _override_get_db():
    async with _TestSessionLocal() as session:
        yield session


# ── Mock AI provider ───────────────────────────────────────────────────────────

MOCK_AI_RESULT = {
    "document_type": "invoice",
    "total_amount": "99.00",
    "currency": "EUR",
    "vendor_name": "ACME Corp",
    "customer_name": "Test Customer",
    "billing_address": "1 Main St",
    "customer_address": "2 Other St",
    "invoice_number": "INV-001",
    "invoice_date": "2026-04-14",
    "due_date": "2026-05-14",
    "tags": ["invoice", "acme"],
    "line_items": [{"description": "Widget", "amount": "99.00"}],
    "suggested_categories": ["Suppliers", "Operating Expenses"],
}


@pytest.fixture
def mock_ai_service():
    """Patch classify_document to return MOCK_AI_RESULT without hitting ai-service."""
    with patch(
        "app.services.ai_client.classify_document",
        new=AsyncMock(return_value=MOCK_AI_RESULT),
    ) as mock:
        yield mock


# ── HTTP client ────────────────────────────────────────────────────────────────

TEST_USER_ID = "test-user-1"
OTHER_USER_ID = "test-user-2"


@pytest_asyncio.fixture
async def client(tmp_path) -> AsyncGenerator[AsyncClient, None]:
    """
    AsyncClient wired to the FastAPI app with:
    - get_db overridden to use test SQLite DB
    - DATA_DIR pointed to a tmp directory
    - Default X-User-Id header set to TEST_USER_ID
    """
    app.dependency_overrides[get_db] = _override_get_db

    with patch("app.services.storage.settings") as mock_settings:
        mock_settings.DATA_DIR = str(tmp_path)
        async with AsyncClient(
            transport=ASGITransport(app=app),
            base_url="http://test",
            headers={"x-user-id": TEST_USER_ID},
        ) as ac:
            yield ac

    app.dependency_overrides.clear()


@pytest_asyncio.fixture
async def other_client(tmp_path) -> AsyncGenerator[AsyncClient, None]:
    """Client acting as a different user — used to test ownership isolation."""
    app.dependency_overrides[get_db] = _override_get_db

    with patch("app.services.storage.settings") as mock_settings:
        mock_settings.DATA_DIR = str(tmp_path)
        async with AsyncClient(
            transport=ASGITransport(app=app),
            base_url="http://test",
            headers={"x-user-id": OTHER_USER_ID},
        ) as ac:
            yield ac

    app.dependency_overrides.clear()


# ── Minimal PDF bytes ──────────────────────────────────────────────────────────

def _make_minimal_pdf(text: str = "Test invoice. Total: EUR 99.00. Vendor: ACME Corp.") -> bytes:
    """
    Build a minimal but valid single-page PDF that pdfplumber can open and
    extract text from.  No external libraries needed — hand-crafted byte structure.
    """
    # We embed the text as a PDF content stream using a built-in font.
    content_stream = (
        f"BT /F1 12 Tf 50 750 Td ({text}) Tj ET"
    ).encode()
    compressed = zlib.compress(content_stream)

    objects: list[bytes] = []

    def obj(n: int, body: bytes) -> bytes:
        return f"{n} 0 obj\n".encode() + body + b"\nendobj\n"

    # 1: Catalog
    objects.append(obj(1, b"<< /Type /Catalog /Pages 2 0 R >>"))
    # 2: Pages
    objects.append(obj(2, b"<< /Type /Pages /Kids [3 0 R] /Count 1 >>"))
    # 3: Page
    objects.append(obj(3, (
        b"<< /Type /Page /Parent 2 0 R "
        b"/MediaBox [0 0 612 792] "
        b"/Contents 4 0 R "
        b"/Resources << /Font << /F1 5 0 R >> >> >>"
    )))
    # 4: Content stream
    objects.append(obj(4, (
        f"<< /Filter /FlateDecode /Length {len(compressed)} >>\n".encode()
        + b"stream\n" + compressed + b"\nendstream"
    )))
    # 5: Font
    objects.append(obj(5, (
        b"<< /Type /Font /Subtype /Type1 "
        b"/BaseFont /Helvetica "
        b"/Encoding /WinAnsiEncoding >>"
    )))

    # Build xref
    header = b"%PDF-1.4\n"
    body = b""
    offsets = []
    for o in objects:
        offsets.append(len(header) + len(body))
        body += o

    xref_offset = len(header) + len(body)
    xref = f"xref\n0 {len(objects) + 1}\n0000000000 65535 f \n".encode()
    for off in offsets:
        xref += f"{off:010d} 00000 n \n".encode()

    trailer = (
        f"trailer\n<< /Size {len(objects) + 1} /Root 1 0 R >>\n"
        f"startxref\n{xref_offset}\n%%EOF\n"
    ).encode()

    return header + body + xref + trailer


@pytest.fixture
def minimal_pdf() -> bytes:
    return _make_minimal_pdf()


@pytest.fixture
def invoice_pdf() -> bytes:
    return _make_minimal_pdf(
        "Invoice INV-001. Date: 2026-04-14. Due: 2026-05-14. "
        "Vendor: ACME Corp, 1 Main St. Customer: Test Customer, 2 Other St. "
        "Widget x1: EUR 99.00. Total: EUR 99.00."
    )


# ── Real PDF fixture (optional) ────────────────────────────────────────────────

def _pdf_fixtures_dir() -> Path:
    return Path(__file__).parent / "pdfs"


def pytest_collect_file(parent, file_path):
    """Not used — just a marker so pytest knows about the pdfs/ directory."""
    return None


@pytest.fixture
def real_pdfs() -> list[Path]:
    """
    Returns a list of PDF paths from tests/pdfs/.
    Tests that use this fixture are skipped if the directory is empty.
    Drop any PDF into features/doc-service/tests/pdfs/ to run live tests.
    """
    pdfs = list(_pdf_fixtures_dir().glob("*.pdf"))
    if not pdfs:
        pytest.skip("No PDFs in tests/pdfs/ — add a PDF file to run live upload tests")
    return pdfs