Vorschau erstellt

app/mailmerge/services/preview.py

@@ -0,0 +1,95 @@
+"""
+Single-Letter-Preview: rendert ausschließlich die erste CSV-Zeile gegen das
+Template und gibt das resultierende PDF als Bytes zurück. Synchroner Pfad,
+keine Celery-Beteiligung – die View ruft das direkt im Request-Kontext auf.
+"""
+from __future__ import annotations
+
+import csv
+import io
+import logging
+import tempfile
+from dataclasses import dataclass
+from pathlib import Path
+
+from .docx_renderer import docx_to_pdf, extract_placeholders, render_docx
+
+logger = logging.getLogger(__name__)
+
+
+class PreviewError(Exception):
+    """Erwartete Fehler beim Preview – werden dem User angezeigt."""
+
+
+@dataclass
+class PreviewResult:
+    pdf_bytes: bytes
+    used_row: dict[str, str]
+    placeholders: list[str]
+    csv_columns: list[str]
+    missing_columns: list[str]
+    extra_columns: list[str]
+
+
+def _read_first_row(csv_file) -> tuple[list[str], dict[str, str]]:
+    """Liest CSV-Header + erste Datenzeile.
+
+    Akzeptiert UploadedFile oder Path-ähnliches. UTF-8, Komma-getrennt.
+    """
+    if hasattr(csv_file, "read"):
+        raw = csv_file.read()
+        if isinstance(raw, bytes):
+            text = raw.decode("utf-8-sig")
+        else:
+            text = raw
+    else:
+        text = Path(csv_file).read_text(encoding="utf-8-sig")
+
+    reader = csv.DictReader(io.StringIO(text))
+    if not reader.fieldnames:
+        raise PreviewError("CSV-Datei enthält keine Header-Zeile.")
+    try:
+        row = next(reader)
+    except StopIteration as exc:
+        raise PreviewError(
+            "CSV-Datei enthält außer dem Header keine Datenzeile."
+        ) from exc
+    return list(reader.fieldnames), row
+
+
+def build_preview(template_path: Path, csv_file) -> PreviewResult:
+    """Rendert die erste CSV-Zeile gegen das Template und liefert ein PDF.
+
+    Validiert vorab Header gegen die Template-Platzhalter und meldet
+    fehlende / überflüssige Spalten.
+    """
+    placeholders = extract_placeholders(template_path)
+    columns, first_row = _read_first_row(csv_file)
+
+    placeholder_set = set(placeholders)
+    column_set = set(columns)
+    missing = sorted(placeholder_set - column_set)
+    extra = sorted(column_set - placeholder_set)
+
+    if missing:
+        raise PreviewError(
+            "Folgende Platzhalter sind im Template enthalten, "
+            "fehlen aber als Spalte in der CSV: "
+            + ", ".join(missing)
+        )
+
+    with tempfile.TemporaryDirectory(prefix="serienbrief-preview-") as tmp:
+        tmpdir = Path(tmp)
+        docx_out = tmpdir / "preview.docx"
+        render_docx(template_path, first_row, docx_out)
+        pdf_path = docx_to_pdf(docx_out, tmpdir)
+        pdf_bytes = pdf_path.read_bytes()
+
+    return PreviewResult(
+        pdf_bytes=pdf_bytes,
+        used_row=first_row,
+        placeholders=placeholders,
+        csv_columns=columns,
+        missing_columns=missing,
+        extra_columns=extra,
+    )

app/mailmerge/urls.py

@@ -7,6 +7,7 @@ urlpatterns = [
     path("templates/new/", views.template_upload, name="template-upload"),
     path("templates/<uuid:pk>/", views.template_detail, name="template-detail"),
     path("jobs/new/", views.job_create, name="job-create"),
+    path("jobs/preview/", views.job_preview, name="job-preview"),
     path("jobs/<uuid:pk>/", views.job_detail, name="job-detail"),
     path("jobs/<uuid:pk>/download/", views.job_download, name="job-download"),
 ]

app/mailmerge/views.py

@@ -1,16 +1,21 @@
+import logging
 from pathlib import Path
 
+from django.contrib import messages
 from django.contrib.auth.decorators import login_required
 from django.http import FileResponse, Http404, HttpResponse
 from django.shortcuts import get_object_or_404, redirect, render
 from django.urls import reverse
-from django.views.decorators.http import require_http_methods
+from django.views.decorators.http import require_http_methods, require_POST
 
 from .forms import LetterTemplateForm, MailMergeJobForm
 from .models import LetterTemplate, MailMergeJob
 from .services.docx_renderer import extract_placeholders
+from .services.preview import PreviewError, build_preview
 from .tasks import run_mailmerge
 
+logger = logging.getLogger(__name__)
+
 
 @login_required
 def dashboard(request):
@@ -54,6 +59,45 @@ def job_create(request):
     return render(request, "mailmerge/job_form.html", {"form": form})
 
 
+@login_required
+@require_POST
+def job_preview(request):
+    """Rendert nur die erste CSV-Zeile gegen das gewählte Template und
+    liefert das PDF inline aus. Persistiert nichts."""
+    form = MailMergeJobForm(request.POST, request.FILES)
+    if not form.is_valid():
+        # Form-Errors zurück ins Hauptformular leiten
+        return render(request, "mailmerge/job_form.html",
+                      {"form": form, "preview_error": None})
+
+    template = form.cleaned_data["template"]
+    csv_upload = form.cleaned_data["recipients_csv"]
+
+    try:
+        result = build_preview(
+            template_path=Path(template.file.path),
+            csv_file=csv_upload,
+        )
+    except PreviewError as exc:
+        messages.error(request, str(exc))
+        return render(request, "mailmerge/job_form.html",
+                      {"form": form, "preview_error": str(exc)})
+    except Exception as exc:  # noqa: BLE001 – defensiv, breite Fehlerklasse von LibreOffice
+        logger.exception("Preview-Render fehlgeschlagen")
+        messages.error(
+            request,
+            "Vorschau konnte nicht erstellt werden: " + str(exc),
+        )
+        return render(request, "mailmerge/job_form.html",
+                      {"form": form, "preview_error": str(exc)})
+
+    response = HttpResponse(result.pdf_bytes, content_type="application/pdf")
+    response["Content-Disposition"] = 'inline; filename="vorschau.pdf"'
+    response["X-Preview-Placeholders"] = ",".join(result.placeholders)
+    response["X-Preview-Extra-Columns"] = ",".join(result.extra_columns)
+    return response
+
+
 @login_required
 def job_detail(request, pk):
     job = get_object_or_404(