Fuchs_Intranet/Fuchs/Docs/Concepts/live-draft-editing.md

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Active	2026-07-10	Fuchs/Services/InvoiceDraft* Fuchs/Services/IInvoiceDraft* Fuchs/Services/ReminderDraft* Fuchs/Services/IReminderDraft* Fuchs/code/InvoiceDraftSession.cs Fuchs/code/InvoiceDraftCalculator.cs Fuchs/code/ReminderDraftSession.cs Fuchs/code/ReminderDraftCalculator.cs Fuchs/Notifications/DraftPreviewHub.cs Fuchs/Notifications/*DraftNotifier* Fuchs/Controllers/IntranetController.InvoiceDraft.cs Fuchs/Controllers/IntranetController.ReminderDraft.cs Fuchs/js/intranet/**	0006-backend-authoritative-draft-editing.md 0007-targeted-draft-signalr-groups.md

Live draft editing (backend-authoritative invoice previews)

Summary

While a back-office user edits an invoice draft, the authoritative state is held in server memory, not in the browser. The browser posts single edits, the server mutates the cached record, recomputes totals/VAT and re-validates, then pushes a "state changed" signal so the browser re-fetches and re-renders. This makes the backend the single source of truth (server-computed sums, consistency checks, in-place PDF preview, change history, explicit discard), reversing the earlier stateless editor. Invoices were the pilot; reminders now mirror the same design (see "Reminders" below).

How it works

Open:     Browser --POST inv/dopen {id | payload}--> server builds InvoiceDraftSession, caches it
          Browser --SignalR JoinDraft(token)--> joins the draft's group; spinner while loading
          Browser --POST inv/dstate {token}--> renders admin/new/req + server sums + validation

Edit:     Browser --POST inv/dpatch {token, delta}--> mutate + recompute + validate + version++
          Server  --SignalR draftReady{token,version}--> Browser re-fetches inv/dstate, re-renders

Preview:  Browser --POST inv/dpreview {token}--> PDF rendered straight from the cache (no upload)
Save:     Browser --POST inv/dsave {token}--> flush cache->DB (RegisterInvoiceAsync) + EventService toast
History:  Browser --POST inv/dhistory {token}--> change list -> "Änderungshistorie" dialog
Discard:  Browser --POST inv/ddiscard {token}--> reload session from DB draft -> draftReady
Close:    Browser --POST inv/dclose {token}--> session removed (+ LeaveDraft)

Expiry:   Server (timer) --SignalR draftExpiring{token,secondsLeft}--> warn "bitte zwischenspeichern"
          Server (evict) --SignalR draftClosed{token,reason}--> close the editor with a reason

• Session (InvoiceDraftSession) is a pure data holder: the editable payload as the exact editor JSON (admin / new / req blocks with items), plus server-computed Sums, ValidationMessages, History, Version, Token, InvId, LastAccessUtc.
• Calculation (InvoiceDraftCalculator, static/pure) ports the former client math: RecomputeLineValues (net/VAT/service-net/service-VAT per line from raw quantity × price × VAT rate, the quantChange/setVat port), RecomputeTotals (the invSumUpdate/csms aggregation + §13b reverse-charge), RecomputePositions (numbers every line except heading/free-text lines continuously across the whole invoice — mirroring the editor's invSumUpdate, so the editor and the PDF show identical Pos. numbers, including after a reorder), and Validate (email/address/items/VAT-rate/negative-total checks). Being pure, it is exhaustively unit-tested. The online editor performs no arithmetic of any kind — not header, footer, sums, totals, taxes, nor a single line's own net/VAT value: $inv.quantChange and $inv.setVat only post the raw field the user changed (qty/price/vat rate), and $inv.invSumUpdate only reassembles the row-contract array needed to post req — it computes no totals, no VAT breakdown, and no service-refund note figures. All of those are rendered exclusively from dstate.sums via $inv.d.footer.
• Sanitisation & reorder. Scalar text deltas (title/email/address/provisionperiod/ provisionlocation) and the section heading (block.replace) are stripped of the editor's TinyMCE HTML (<p>…</p>, <br>) to plain text in ApplyDelta (HtmlToPlain) — the backend is the single source of truth, so no HTML reaches the DB, the PDF or a reloaded draft. Section drags post a block.order delta (["id",…]) that reorders Req; positions are then renumbered and pushed back via the view state (applyState/applyPositions). The change history records the changed field (e.g. the new heading text), never the whole block JSON. The PDF (FuchsPdf) renders a heading row per block (FdsInvoiceData.InvoiceBlocks) and shows every position's price (set members are priced like standalone lines; only setonly collapses them), so the PDF preview mirrors the online editor.
• Orchestration (InvoiceDraftEditService, scoped) opens sessions (from a fresh payload or by reloading a DB draft via fds__getInvoice, reshaped like BuildInvoiceRequestList), applies deltas (ApplyDelta), builds the view-state DTO, flushes to the DB by reusing IInvoiceService.RegisterInvoiceAsync (no new persistence path), renders previews from a synthesised registration, and discards by reloading.
• Cache (InvoiceDraftCache, singleton) stores sessions by token with an idle sliding TTL; InvoiceDraftExpiryService (a BackgroundService) warns before, and evicts after, the TTL. TTL/warn-lead are configurable under Fuchs:DraftEditing.
• Signals (DraftPreviewHub at /draftpreview + IDraftNotifier) are targeted at the editing browser via a group named after the session token: draftReady, draftExpiring, draftClosed. Business success/failure still flows through IEventService/NotificationHub.
• Frontend ($fis.draft in fis_main.js, editor in fis.inv_shared.js) opens/joins, posts one delta per change, shows a loading state whenever awaiting a signal, and offers "Änderungen verwerfen" and "Änderungshistorie" menu actions. It computes nothing — no header, footer, sums, totals, taxes, or per-line values.

Key files

• Fuchs/code/InvoiceDraftSession.cs — session + ChangeHistoryEntry + InvoiceDraftSums.
• Fuchs/code/InvoiceDraftCalculator.cs — pure recompute + validate.
• Fuchs/Services/InvoiceDraftCache.cs / IInvoiceDraftCache.cs — in-memory store + TTL.
• Fuchs/Services/InvoiceDraftEditService.cs / IInvoiceDraftService.cs — orchestration + delta contract.
• Fuchs/Services/InvoiceDraftExpiryService.cs — idle warn/evict monitor.
• Fuchs/Notifications/DraftPreviewHub.cs, DraftNotifier.cs, IDraftNotifier.cs — targeted signals.
• Fuchs/Controllers/IntranetController.InvoiceDraft.cs — inv/d* endpoints.
• Fuchs/js/intranet/fis_main.js, Fuchs/js/intranet/modules/fis.inv_shared.js — client.

Reminders (Zahlungserinnerung)

Reminders mirror the same backend-authoritative model with a reminder-shaped session. A reminder chases a single invoiced amount, so the machinery is simpler than an invoice's: there are no line-item blocks, VAT grouping or reordering — just recipient fields and the amount pair.

• Endpoints are rem/d* (dopen/dstate/dpatch/dpreview/dsave/dhistory/dclose), dispatched from Do_Process_Reminder. Finalise + email still runs through the existing rem/conf (HandleReminderConf), exactly as invoices finalise through req/sconf.
• Session (ReminderDraftSession) holds the editor's new (subject / invoiceaddress / invoiceemail / text / amount / amount_payed / CustomValues) and rem (invid / type / invoiceid / invoicedate) blocks, plus server-computed Sums (AmountTotal, AmountPayed, AmountOpen). It reuses the shared ChangeHistoryEntry; validation uses ReminderDraftValidationMessage.
• Calculation (ReminderDraftCalculator, static/pure): AmountOpen = AmountTotal − AmountPayed, plus email/address/subject/open-amount plausibility checks. Exhaustively unit-tested.
• Deltas (ReminderDraftDelta): scalar email/address/subject/text (HTML-sanitised via the shared InvoiceDraftEditService.HtmlToPlain), the numeric amount/amount_payed (normalised to an invariant decimal string), and contact (→ CustomValues).
• Orchestration (ReminderDraftEditService, scoped) flushes to the DB by reusing IReminderService.RegisterReminderAsync, and renders previews from a synthesised ReminderRegistration (including the single-invoice invoices row the reminder PDF table renders) so a preview needs no DB round-trip. Note: RegisterReminderAsync is create-only (there is no fds__setReminder update proc), so a re-saved reminder draft does not update the prior DB row — the primary flow (preview → confirm) flushes once immediately before finalising.
• Cache/expiry (ReminderDraftCache singleton + ReminderDraftExpiryService) mirror the invoice ones and share the same Fuchs:DraftEditing TTL config.
• Signals reuse the shared DraftPreviewHub + IDraftNotifier unchanged — the token-keyed groups serve invoice and reminder drafts alike.
• Frontend ($inv.rd in fis.inv_shared.js) opens/joins on rem/dopen, posts one delta per inline edit and per item-row amount change, renders the open-amount footer + validation from the server state, and previews/finalises through rem/dpreview → rem/dsave → rem/conf. It shares the invoice editor DOM; $inv.d and $inv.rd each key off their own token, so the shared inline editor safely no-ops for whichever mode is inactive.

Reminder key files

• Fuchs/code/ReminderDraftSession.cs — session + ReminderDraftSums + ReminderDraftValidationMessage.
• Fuchs/code/ReminderDraftCalculator.cs — pure open-amount recompute + validate.
• Fuchs/Services/ReminderDraftCache.cs / IReminderDraftCache.cs — in-memory store + TTL.
• Fuchs/Services/ReminderDraftEditService.cs / IReminderDraftService.cs — orchestration + delta contract.
• Fuchs/Services/ReminderDraftExpiryService.cs — idle warn/evict monitor.
• Fuchs/Controllers/IntranetController.ReminderDraft.cs — rem/d* endpoints.

Related decisions

• 0006 — Backend-authoritative draft editing
• 0007 — Targeted draft SignalR groups