app/api/convert.py

"""POST /convert — PDF in, reconciled statement data out (JSON or .xlsx).

Stateless: the uploaded PDF is read into memory, processed in an isolated temp
dir, and deleted before the response is built. Nothing is persisted.
"""
from __future__ import annotations

import io
import logging

from fastapi import APIRouter, File, Header, HTTPException, Query, UploadFile
from fastapi.responses import JSONResponse, StreamingResponse
from openpyxl import Workbook

from app.core.config import API_KEY, MAX_UPLOAD_BYTES
from app.core.files import temp_pdf
from app.engine.converter import BankStatementConverter, ExtractedStatement

router = APIRouter()
logger = logging.getLogger("ebs.convert")

XLSX_MEDIA = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"


def _is_pdf(file: UploadFile) -> bool:
    if (file.content_type or "").lower() in {"application/pdf", "application/x-pdf"}:
        return True
    return (file.filename or "").lower().endswith(".pdf")


def _statement_dict(st: ExtractedStatement) -> dict:
    return {
        "account": st.account,
        "accountHolder": st.account_holder,
        "period": st.period,
        "openingBalance": st.opening_balance,
        "closingBalance": st.closing_balance,
        "reconciles": st.reconciles,
        "reconcileStatus": st.reconcile_status,
        "runningBalanceOk": st.running_balance_ok,
        "statedSummaryOk": st.stated_summary_ok,
        "reconciliationDetail": st.reconciliation_detail,
        "transactions": [
            {
                "date": t.date,
                "description": t.description,
                "debit": t.debit,
                "credit": t.credit,
                "balance": t.balance,
            }
            for t in st.transactions
        ],
    }


def _xlsx_bytes(statements: list[ExtractedStatement]) -> io.BytesIO:
    wb = Workbook()
    wb.remove(wb.active)
    for n, st in enumerate(statements, 1):
        ws = wb.create_sheet(f"Account{n}")
        ws.append(["Date", "Description", "Debit", "Credit", "Balance"])
        for t in st.transactions:
            ws.append([t.date, t.description, t.debit, t.credit, t.balance])
    buf = io.BytesIO()
    wb.save(buf)
    buf.seek(0)
    return buf


@router.post("/convert")
async def convert(
    file: UploadFile = File(...),
    format: str = Query("json", pattern="^(json|xlsx)$"),
    x_api_key: str | None = Header(default=None),
):
    if API_KEY and x_api_key != API_KEY:
        raise HTTPException(status_code=401, detail="Unauthorized.")
    if not _is_pdf(file):
        raise HTTPException(status_code=415, detail="Only PDF files are accepted.")

    data = await file.read()
    if not data:
        raise HTTPException(status_code=400, detail="Empty file.")
    if len(data) > MAX_UPLOAD_BYTES:
        mb = MAX_UPLOAD_BYTES // (1024 * 1024)
        raise HTTPException(status_code=413, detail=f"File too large (max {mb} MB).")

    try:
        with temp_pdf(data) as pdf_path:
            statements = BankStatementConverter(pdf_path).extract()
    except Exception:
        # Bad user input (corrupt / password-protected / not a real PDF) must
        # surface as 4xx, never a 500. Logged for observability.
        logger.exception("extraction failed for upload %r", file.filename)
        raise HTTPException(
            status_code=422,
            detail="Couldn't read this PDF. It may be corrupt, password-protected, or not a valid PDF.",
        )

    if not statements or all(not s.transactions for s in statements):
        raise HTTPException(
            status_code=422,
            detail="Couldn't read any transactions. If this is a scanned image, a clearer scan may help.",
        )

    if format == "xlsx":
        return StreamingResponse(
            _xlsx_bytes(statements),
            media_type=XLSX_MEDIA,
            headers={"Content-Disposition": 'attachment; filename="statement.xlsx"'},
        )

    return JSONResponse(
        {
            "count": sum(len(s.transactions) for s in statements),
            "statements": [_statement_dict(s) for s in statements],
        }
    )