"""
Manual invoice upload: save file, optionally run AI vision to extract amount/date.
"""
import io
from datetime import date, datetime
from pathlib import Path
from typing import Any, Dict, Tuple

from fastapi import UploadFile

from backend.app.services.ai_service import extract_invoice_metadata

FINANCE_BASE = Path("data/finance")
ALLOWED_IMAGE = {".jpg", ".jpeg", ".png", ".webp"}
ALLOWED_PDF = {".pdf"}


def _current_month() -> str:
    return datetime.utcnow().strftime("%Y-%m")


def _pdf_first_page_to_image(pdf_bytes: bytes) -> Tuple[bytes, str] | None:
    """Render first page of PDF to PNG bytes. Returns (bytes, 'image/png') or None on error."""
    try:
        import fitz
        doc = fitz.open(stream=pdf_bytes, filetype="pdf")
        if doc.page_count == 0:
            doc.close()
            return None
        page = doc[0]
        pix = page.get_pixmap(dpi=150)
        png_bytes = pix.tobytes("png")
        doc.close()
        return (png_bytes, "image/png")
    except Exception:
        return None


async def process_invoice_upload(
    file: UploadFile,
) -> Tuple[str, str, str, float | None, date | None]:
    """
    Save uploaded file to data/finance/{YYYY-MM}/manual/, run OCR for amount/date.
    Returns (file_name, file_path, month_str, amount, billing_date).
    """
    month_str = _current_month()
    manual_dir = FINANCE_BASE / month_str / "manual"
    manual_dir.mkdir(parents=True, exist_ok=True)

    raw = await file.read()
    filename = file.filename or "upload"
    suf = Path(filename).suffix.lower()

    if suf in ALLOWED_IMAGE:
        image_bytes, mime = raw, (file.content_type or "image/jpeg")
        if "png" in (suf or ""):
            mime = "image/png"
        amount, date_str = await extract_invoice_metadata(image_bytes, mime)
    elif suf in ALLOWED_PDF:
        image_result = _pdf_first_page_to_image(raw)
        if image_result:
            image_bytes, mime = image_result
            amount, date_str = await extract_invoice_metadata(image_bytes, mime)
        else:
            amount, date_str = None, None
        # Save original PDF
    else:
        amount, date_str = None, None

    # Unique filename
    dest = manual_dir / filename
    counter = 1
    while dest.exists():
        dest = manual_dir / f"{dest.stem}_{counter}{dest.suffix}"
        counter += 1

    dest.write_bytes(raw)
    file_path = str(dest)
    file_name = dest.name

    billing_date = None
    if date_str:
        try:
            billing_date = date.fromisoformat(date_str)
        except ValueError:
            pass
    if billing_date is None:
        billing_date = date.today()

    return (file_name, file_path, month_str, amount, billing_date)