backbone_pos/application/service/

pos_sync.rs

//! The offline reconciliation verb (`sync_from_ui`) (hand-authored, user-owned).
//!
//! An `impl PosWriteService` chunk over the vocabulary in [`super::pos_write_service`]. An offline
//! client (register app that sold without connectivity) replays a ticket here; the server is the
//! book of record and TRUSTS THE REPLAY FOR IDENTITY ONLY:
//!
//! - **Identity** is the payload's `client_uuid` — a replay whose uuid already names a live ticket
//!   UPDATES that ticket (while it is still draft) instead of creating a second one. A finalized
//!   ticket short-circuits as [`SyncAction::ReplayFinalized`] — the server's state wins, nothing is
//!   rewritten.
//! - **Money** is ALWAYS re-derived: the replay's lines + tenders run through the SAME compute core
//!   as `ring_sale` ([`super::pos_compute`]: register templates → document-grade tax →
//!   register-config cash rounding), and the tender sum implies paid/change. Any client-claimed
//!   total was discarded at the DTO boundary — this verb never sees one.
//! - **Partner + session are validated, not trusted**: a replay cannot re-assign a ticket's
//!   customer, and it cannot ring under a session that has since closed unless it names an open
//!   RESCUE session (the typed refusal [`PosError::SessionClosedRescueRequired`] is the
//!   rescue-or-refuse contract: the client either re-attributes the ticket to the new shift or
//!   surfaces the mismatch to a human).
//! - **Refund lineage is single-parent**: one refund names one parent (`refund_of_client_uuid`);
//!   re-pointing a refund at a DIFFERENT parent than it was first recorded against is refused
//!   ([`PosError::RefundLineageConflict`]), and a parent that does not resolve refuses
//!   ([`PosError::RefundParentNotFound`]). A refund replay is a privileged mutation — the manager
//!   PIN is verified first.
//!
//! Per the module's 4-layer rule this file holds no SQL — the statements live on
//! `PosInvoiceRepository` / `PosInvoiceItemRepository` / `PosPaymentRepository` /
//! `PosOpeningEntryRepository` / `PosProfileRepository`.
//!
//! Tenancy is composition-installed (ADR-0029): the identity pre-read rides the ambient org scope,
//! and each write half opens its OWN transaction, re-binds the ambient scope onto it, and runs every
//! validation read + the compute's register-config read on that same connection — so a replay sees
//! through exactly the fence it writes under.

use rust_decimal::Decimal;
use uuid::Uuid;

use crate::infrastructure::persistence::{NewDraftInvoiceRow, NewInvoiceItemRow, NewTenderRow};

use super::pos_compute::ComputeLineIn;
use super::pos_events::{PosEvent, PosTenderCompleted};
use super::pos_ports::{BillingPort, PaymentPort, PosTaxComputePort, PosTaxDocumentType};
use super::pos_write_service::{
    legacy_company_echo, map_invoice_dup, money, relay_ambient_scope, NewSyncSale, PosError,
    PosWriteService, SyncAction, SyncOutcome, TicketTotals,
};

impl PosWriteService {
    /// Replay one offline ticket. See the module doc for the identity/trust contract.
    /// `tax` resolves the document-grade compute (as on `ring_sale`); `billing`/`payment` are only
    /// touched when the replay is a REFUND (they drive the same reversal pair `return_sale` does).
    pub async fn sync_from_ui(
        &self,
        s: NewSyncSale,
        tax: &dyn PosTaxComputePort,
        billing: &dyn BillingPort,
        payment: &dyn PaymentPort,
    ) -> Result<SyncOutcome, PosError> {
        // Identity first (ambient scope): does a live ticket already carry this client uuid?
        // A uuid only namespaces inside the caller's scope — another unit's ticket carrying the
        // same uuid is simply not found.
        if let Some(existing) = self.invoices.find_by_client_uuid(&self.rpool(), s.client_uuid).await? {
            // Finalized server-side (paid/returned): the replay changes nothing. The server's
            // persisted money is the answer.
            if existing.status != "draft" {
                return Ok(finalized(&existing));
            }
            return self.sync_update_draft(s, existing, tax).await;
        }

        // No live ticket carries the uuid. A refund replay never creates a draft — it drives the
        // (privileged, idempotent) full-return flow against its parent.
        if let Some(parent_uuid) = s.refund_of_client_uuid {
            // Privileged: the manager PIN is verified BEFORE anything is read or written.
            let manager = s.manager.as_ref().ok_or(PosError::ManagerAuthRequired)?;
            self.verify_manager_internal(manager, s.source_ip.as_deref()).await?;
            let parent = self.invoices
                .find_by_client_uuid(&self.rpool(), parent_uuid)
                .await?
                .ok_or(PosError::RefundParentNotFound(parent_uuid))?;
            // The replay's own totals are discarded by contract: a full refund reverses the
            // parent's persisted money, whatever the client says it handed back.
            let out = self
                .return_sale(parent.id, billing, payment, None)
                .await?;
            // return_sale is idempotent on the parent's paid→returned flip; whether THIS call
            // recorded the return ticket or replayed an existing one is observable from the
            // parent's state we already read.
            let action = if parent.status == "paid" { SyncAction::Created } else { SyncAction::ReplayFinalized };
            return Ok(SyncOutcome {
                pos_invoice_id: out.return_ticket_id,
                action,
                totals: TicketTotals {
                    net_total: parent.net_total,
                    tax_total: parent.tax_total,
                    grand_total: parent.grand_total,
                    rounding_adjustment: Decimal::ZERO,
                    rounded_total: parent.rounded_total,
                    paid_total: parent.rounded_total,
                    change_due: Decimal::ZERO,
                },
            });
        }

        self.sync_create_draft(s, tax).await
    }

    /// The CREATE half: a fresh offline ticket, rung through the shared compute core into a draft
    /// carrying the sync identity. One scope-relayed transaction carries every read and write.
    async fn sync_create_draft(&self, s: NewSyncSale, tax: &dyn PosTaxComputePort) -> Result<SyncOutcome, PosError> {
        let mut tx = self.rpool().begin().await?;
        relay_ambient_scope(&mut tx).await?;
        // Session validation (rescue-or-refuse): the session the client rang under must be open, or
        // the replay must name an open rescue session to attribute the ticket to.
        let session = self.resolve_session_for_create(&mut *tx, &s).await?;
        // Tender methods are validated against the enum up front — a typo'd method is a typed 422,
        // not a DB cast failure mid-transaction.
        self.validate_tender_methods(&mut *tx, &s).await?;
        // Restaurant lane — seating, same contract as the online ring: the named table must exist
        // and hold no other draft (the DB partial unique is the race backstop).
        if let Some(table) = s.pos_table_id {
            if self.tables.fetch_table(&mut *tx, table).await?.is_none() {
                return Err(PosError::TableNotFound(table));
            }
            if let Some(occupant) = self
                .invoices
                .find_draft_on_table(&mut *tx, table, None)
                .await?
            {
                return Err(PosError::TableOccupied { pos_table_id: table, draft_invoice_id: occupant });
            }
        }
        // Order-level discount: rate resolved from the master, folded before the compute.
        let order_discount = self
            .resolve_order_discount(&mut tx, s.pos_profile_id, s.discount_id)
            .await?;

        let mut compute_lines: Vec<ComputeLineIn> = s
            .lines
            .iter()
            .map(|l| ComputeLineIn {
                item_id: l.item_id,
                revenue_account_id: l.revenue_account_id,
                description: l.description.clone(),
                course: l.course,
                quantity: l.quantity,
                unit_price: l.unit_price,
                discount_amount: l.discount_amount,
            })
            .collect();
        if let Some(d) = &order_discount {
            Self::fold_order_discount(&mut compute_lines, d.percentage)?;
        }
        let computed = self
            .compute_ticket(
                &mut *tx,
                s.pos_profile_id,
                s.posting_at.date(),
                PosTaxDocumentType::Invoice,
                compute_lines,
                tax,
            )
            .await?;
        let paid = s.tenders.iter().map(|t| t.amount).sum::<Decimal>();
        let totals = Self::totals_with_tenders(&computed, paid);

        // The server mints the receipt number, deterministically from the sync identity (scope
        // fragment + uuid fragment): a retried create collides on it (and on the uuid) instead of
        // double-ringing, while two tenants replaying the same device uuid never collide — the
        // receipt-number unique index is global. The scope fragment is the ambient scope's legacy
        // company echo (the acting unit; nil only when undecorated).
        let receipt_number = format!(
            "SYNC-{}-{}",
            &legacy_company_echo().simple().to_string()[..4],
            &s.client_uuid.simple().to_string()[..12]
        );
        let id = Uuid::new_v4();
        let r = self.invoices.insert_draft(&mut tx, &NewDraftInvoiceRow {
            id,
            client_uuid: Some(s.client_uuid),
            pos_profile_id: s.pos_profile_id,
            opening_entry_id: session,
            branch_id: s.branch_id,
            customer_id: s.customer_id,
            pos_table_id: s.pos_table_id,
            receipt_number: &receipt_number,
            posting_at: s.posting_at,
            net_total: computed.net_total,
            tax_total: computed.tax_total,
            grand_total: computed.grand_total,
            rounding_adjustment: computed.rounding_adjustment,
            rounded_total: computed.rounded_total,
        }).await;
        if let Err(e) = r {
            return Err(map_invoice_dup(
                e, &receipt_number, Some(s.client_uuid), s.pos_table_id,
                &self.invoices, &self.rpool(), None,
            ).await);
        }
        check_replay_change_is_cash(&s, computed.rounded_total)?;
        self.sync_write_children(&mut tx, id, &computed, &s).await?;
        // The replay can carry tenders from the first moment (the offline client already took
        // payment). Re-sum what was just written onto the header so paid/change can never disagree
        // with the tender rows — same contract `add_tender` holds on the online path.
        let paid_total = self.payments.sum_paid_total_on(&mut tx, id).await?;
        let change_due = if paid_total > computed.rounded_total {
            paid_total - computed.rounded_total
        } else {
            Decimal::ZERO
        };
        self.invoices.update_tender_totals(&mut tx, id, paid_total, change_due).await?;
        // Durable recognition event, staged INSIDE this (scope-relayed) transaction — atomic with
        // the ticket, the same contract the online `add_tender` path holds. A staging failure
        // fails the replay: a silently lost event would leave the ticket draft forever with no
        // trace of why.
        // A fresh ticket was paid nothing before this replay.
        let crossed = crosses_full_payment(false, computed.rounded_total, paid_total);
        if crossed {
            self.stage_tender_completed_in_tx(&mut tx, id).await?;
        }
        tx.commit().await?;
        if crossed {
            self.emit_tender_completed(id);
        }
        Ok(SyncOutcome {
            pos_invoice_id: id,
            action: SyncAction::Created,
            totals: TicketTotals { paid_total, change_due, ..totals },
        })
    }

    /// The UPDATE half: rewrite a live DRAFT ticket from its replay (full-snapshot semantics — the
    /// replay carries the complete basket + tender set). Partner, session, and refund lineage are
    /// validated before anything is written. One scope-relayed transaction carries every read and
    /// write.
    async fn sync_update_draft(
        &self,
        s: NewSyncSale,
        existing: crate::infrastructure::persistence::SyncLookupRow,
        tax: &dyn PosTaxComputePort,
    ) -> Result<SyncOutcome, PosError> {
        let mut tx = self.rpool().begin().await?;
        relay_ambient_scope(&mut tx).await?;
        // Lock the ticket before anything else: recognition cannot flip it to paid between this
        // check and the rewrite below. A ticket that left draft since the identity read is
        // finalized, and the replay changes nothing.
        let held = self.invoices
            .lock_for_sync_on(&mut tx, existing.id).await?
            .ok_or(PosError::InvoiceNotFound(existing.id))?;
        if held.status != "draft" {
            drop(tx);
            let now = self.invoices
                .find_by_client_uuid(&self.rpool(), s.client_uuid).await?
                .ok_or(PosError::InvoiceNotFound(existing.id))?;
            return Ok(finalized(&now));
        }
        let was_full = held.rounded_total > Decimal::ZERO && held.paid_total >= held.rounded_total;
        // Partner is validated, never re-assigned silently.
        if existing.customer_id != s.customer_id {
            return Err(PosError::SyncPartnerMismatch);
        }
        // Refund lineage: a ticket that was never a refund cannot become one on replay (the refund
        // path is the privileged full-return flow, not a draft rewrite), and a refund ticket cannot
        // be re-pointed at a different parent.
        if existing.is_return || existing.return_against.is_some() || s.refund_of_client_uuid.is_some() {
            return Err(PosError::RefundLineageConflict);
        }
        // Session: equal names must both be open; a different name is only honored when the
        // ORIGINAL session closed and the payload's session (or named rescue) is open — and the
        // target must be the same register's session.
        let session = self.resolve_session_for_update(&mut *tx, &s, &existing).await?;
        self.validate_tender_methods(&mut *tx, &s).await?;
        // Restaurant lane — table TRANSFER: the replay's table is honored as the ticket's new seat
        // (diners move; a draft is not pinned to its birth table the way it is to its register).
        // The named table must exist, and if it differs from the current seat it must hold no
        // OTHER draft — the occupancy check excludes THIS ticket.
        if let Some(table) = s.pos_table_id {
            if self.tables.fetch_table(&mut *tx, table).await?.is_none() {
                return Err(PosError::TableNotFound(table));
            }
            if Some(table) != existing.pos_table_id {
                if let Some(occupant) = self
                    .invoices
                    .find_draft_on_table(&mut *tx, table, Some(existing.id))
                    .await?
                {
                    return Err(PosError::TableOccupied { pos_table_id: table, draft_invoice_id: occupant });
                }
            }
        }
        // Order-level discount: rate resolved from the master, folded before the compute.
        let order_discount = self
            .resolve_order_discount(&mut tx, existing.pos_profile_id, s.discount_id)
            .await?;

        // The ticket keeps the register it was born on — its tax + rounding config — even when the
        // session is rescued to a new shift of that same register.
        let mut compute_lines: Vec<ComputeLineIn> = s
            .lines
            .iter()
            .map(|l| ComputeLineIn {
                item_id: l.item_id,
                revenue_account_id: l.revenue_account_id,
                description: l.description.clone(),
                course: l.course,
                quantity: l.quantity,
                unit_price: l.unit_price,
                discount_amount: l.discount_amount,
            })
            .collect();
        if let Some(d) = &order_discount {
            Self::fold_order_discount(&mut compute_lines, d.percentage)?;
        }
        let computed = self
            .compute_ticket(
                &mut *tx,
                existing.pos_profile_id,
                s.posting_at.date(),
                PosTaxDocumentType::Invoice,
                compute_lines,
                tax,
            )
            .await?;
        let paid = s.tenders.iter().map(|t| t.amount).sum::<Decimal>();
        let totals = Self::totals_with_tenders(&computed, paid);
        check_replay_change_is_cash(&s, computed.rounded_total)?;

        let id = existing.id;
        let now = chrono::Utc::now();
        // Full snapshot: retire the prior lines + tenders (soft delete — audit trail kept, sync
        // uuid uniqueness freed), then write the replay's.
        self.items.soft_delete_lines_for_ticket(&mut tx, id, now).await?;
        self.payments.soft_delete_tenders_for_ticket(&mut tx, id, now).await?;
        let r = self.invoices
            .update_draft_from_sync(
                &mut tx, id, session, s.branch_id, s.customer_id, s.pos_table_id,
                computed.net_total, computed.tax_total, computed.grand_total,
                computed.rounding_adjustment, computed.rounded_total,
                totals.paid_total, totals.change_due,
            )
            .await;
        match r {
            Ok(1) => {}
            // Unreachable under the row lock taken above; refused rather than writing children
            // onto a ticket the header update did not take.
            Ok(_) => return Err(PosError::NotDraft),
            Err(e) => {
                // A unique violation here is the table partial unique racing the occupancy
                // pre-check (a transfer onto a table another draft just claimed) — map it to the
                // typed 409.
                return Err(map_invoice_dup(
                    e, "", Some(s.client_uuid), s.pos_table_id,
                    &self.invoices, &self.rpool(), Some(id),
                ).await);
            }
        }
        self.sync_write_children(&mut tx, id, &computed, &s).await?;
        // Durable recognition event, staged INSIDE this (scope-relayed) transaction — atomic with
        // the rewrite, the same contract the online `add_tender` path holds. A staging failure
        // fails the replay: a silently lost event would leave the ticket draft forever with no
        // trace of why.
        // Only the replay that completes the payment triggers recognition; a replay of a ticket
        // that was already paid up re-emits nothing.
        let crossed = crosses_full_payment(was_full, computed.rounded_total, totals.paid_total);
        if crossed {
            self.stage_tender_completed_in_tx(&mut tx, id).await?;
        }
        tx.commit().await?;
        if crossed {
            self.emit_tender_completed(id);
        }
        Ok(SyncOutcome { pos_invoice_id: id, action: SyncAction::Updated, totals })
    }

    /// Write the replay's lines + tenders onto a ticket inside the caller's transaction. The tenders
    /// re-sum to the header's paid/change (they were computed from the same sum), so the header and
    /// its tender lines can never disagree.
    async fn sync_write_children(
        &self,
        tx: &mut sqlx::PgConnection,
        pos_invoice_id: Uuid,
        computed: &super::pos_compute::ComputedTicket,
        s: &NewSyncSale,
    ) -> Result<(), PosError> {
        for (l, src) in computed.lines.iter().zip(&s.lines) {
            self.items.insert_line(tx, &NewInvoiceItemRow {
                id: Uuid::new_v4(),
                pos_invoice_id,
                client_uuid: Some(src.client_uuid),
                item_id: l.item_id,
                description: l.description.as_deref(),
                course: l.course,
                quantity: l.quantity,
                unit_price: l.unit_price,
                discount_amount: l.discount_amount,
                net_amount: l.net_amount,
                revenue_account_id: l.revenue_account_id,
            }).await?;
        }
        for t in &s.tenders {
            if t.amount <= Decimal::ZERO {
                return Err(PosError::NegativeAmount);
            }
            self.payments.insert_tender(tx, &NewTenderRow {
                id: Uuid::new_v4(),
                pos_invoice_id,
                client_uuid: Some(t.client_uuid),
                payment_method: &t.method,
                amount: money(t.amount),
                reference_no: t.reference_no.as_deref(),
            }).await?;
        }
        Ok(())
    }

    /// Durable staging half of a replay's recognition triggers: when the replay crosses full
    /// payment AND an outbox schema is configured, stage `PosTenderCompleted` INSIDE the replay's
    /// own transaction — atomic with the ticket, the same contract the online `add_tender` path
    /// holds. The caller's transaction is scope-relayed, so the fenced outbox INSERT passes the
    /// row-level-security WITH CHECK under a restricted app role; a second, unbound transaction is
    /// exactly what the fence rejects (and what this staging must never revert to). A staging
    /// failure propagates and fails the whole replay — the durable event must never be lost
    /// silently behind a reported sync success. The fence column carries the ambient scope's
    /// legacy company echo (the acting unit; ADR-0029).
    async fn stage_tender_completed_in_tx(
        &self,
        tx: &mut sqlx::PgConnection,
        pos_invoice_id: Uuid,
    ) -> Result<(), PosError> {
        if let Some(schema) = &self.outbox_schema {
            let rec = super::pos_tender::tender_completed_outbox_record(pos_invoice_id, legacy_company_echo(), chrono::Utc::now());
            backbone_outbox::outbox::stage(&mut *tx, schema, &rec)
                .await
                .map_err(|e| PosError::Db(sqlx::Error::Protocol(e.to_string())))?;
        }
        Ok(())
    }

    /// Fire-and-forget recognition trigger for a replay that (now) crosses full payment — the
    /// in-process half of the SAME contract as `add_tender`: durable outbox staging first (inside
    /// the replay's transaction, before its commit — see [`Self::stage_tender_completed_in_tx`]),
    /// fire-and-forget sink second. Double delivery is safe: recognition is replay-safe end to end.
    /// The `company_id` field is the documented legacy twin (ADR-0029).
    fn emit_tender_completed(&self, pos_invoice_id: Uuid) {
        self.sink.publish(PosEvent::PosTenderCompleted(PosTenderCompleted {
            pos_invoice_id, company_id: legacy_company_echo(),
        }));
    }

    /// CREATE-session resolution: the named session must be open, or closed WITH an open rescue.
    /// Refuses with the typed rescue-refusal otherwise. Reads ride the caller's scope-relayed
    /// connection.
    async fn resolve_session_for_create(&self, conn: &mut sqlx::PgConnection, s: &NewSyncSale) -> Result<Uuid, PosError> {
        let named = self.openings
            .fetch_status_on(&mut *conn, s.opening_entry_id)
            .await?
            .ok_or(PosError::SessionNotFound(s.opening_entry_id))?;
        if named == "open" {
            // Open, but still the ticket's OWN register: the plain-open path owes the same
            // register pairing the rescue arms enforce — no mixing configs and drawers.
            return self.same_register_open_session(&mut *conn, s.opening_entry_id, s.pos_profile_id).await;
        }
        // Closed: honor the rescue only when it is an OPEN session on the SAME register the ticket
        // names — a rescue onto another register's drawer would move money between tills.
        if let Some(rescue) = s.rescue_opening_entry_id {
            return self.same_register_open_session(&mut *conn, rescue, s.pos_profile_id).await;
        }
        Err(PosError::SessionClosedRescueRequired(s.opening_entry_id))
    }

    /// UPDATE-session resolution: an unchanged name must be open; a changed name is honored only
    /// when the ORIGINAL closed and the new session is open on the SAME register as the ticket.
    /// Reads ride the caller's scope-relayed connection.
    async fn resolve_session_for_update(
        &self,
        conn: &mut sqlx::PgConnection,
        s: &NewSyncSale,
        existing: &crate::infrastructure::persistence::SyncLookupRow,
    ) -> Result<Uuid, PosError> {
        if s.opening_entry_id == existing.opening_entry_id {
            let st = self.openings
                .fetch_status_on(&mut *conn, existing.opening_entry_id)
                .await?
                .ok_or(PosError::SessionNotFound(existing.opening_entry_id))?;
            if st != "open" {
                // The original closed between the create replay and this one: fall through to the
                // rescue rules below using the payload's rescue, not a silent re-attribution.
                if let Some(rescue) = s.rescue_opening_entry_id {
                    return self.same_register_open_session(&mut *conn, rescue, existing.pos_profile_id).await;
                }
                return Err(PosError::SessionClosedRescueRequired(existing.opening_entry_id));
            }
            return Ok(existing.opening_entry_id);
        }
        // Different session name: only a CLOSED original + an OPEN target on the ticket's register.
        let orig = self.openings
            .fetch_status_on(&mut *conn, existing.opening_entry_id)
            .await?
            .ok_or(PosError::SessionNotFound(existing.opening_entry_id))?;
        if orig == "open" {
            return Err(PosError::SyncSessionMismatch);
        }
        let target = s.rescue_opening_entry_id.unwrap_or(s.opening_entry_id);
        self.same_register_open_session(&mut *conn, target, existing.pos_profile_id).await
    }

    /// The rescue must be an OPEN session on the ticket's own register — a rescue onto another
    /// register's drawer would move money between tills. Reads ride the caller's scope-relayed
    /// connection.
    async fn same_register_open_session(
        &self,
        conn: &mut sqlx::PgConnection,
        session: Uuid,
        pos_profile_id: Uuid,
    ) -> Result<Uuid, PosError> {
        let st = self.openings
            .fetch_status_on(&mut *conn, session)
            .await?
            .ok_or(PosError::SessionNotFound(session))?;
        if st != "open" {
            return Err(PosError::SessionClosedRescueRequired(session));
        }
        let profile = self.openings
            .fetch_profile_id_on(&mut *conn, session)
            .await?
            .ok_or(PosError::SessionNotFound(session))?;
        if profile != pos_profile_id {
            return Err(PosError::SessionRegisterMismatch);
        }
        Ok(session)
    }

    /// Every replayed tender method must be a live enum variant. Reads ride the caller's
    /// scope-relayed connection.
    async fn validate_tender_methods(&self, conn: &mut sqlx::PgConnection, s: &NewSyncSale) -> Result<(), PosError> {
        let valid = self.payments.valid_methods(&mut *conn).await?;
        for t in &s.tenders {
            if !valid.iter().any(|m| m == &t.method) {
                return Err(PosError::InvalidTenderMethod(t.method.clone()));
            }
        }
        Ok(())
    }
}

/// The answer to a replay of a ticket the server already finalized: its persisted money.
fn finalized(t: &crate::infrastructure::persistence::SyncLookupRow) -> SyncOutcome {
    SyncOutcome {
        pos_invoice_id: t.id,
        action: SyncAction::ReplayFinalized,
        totals: TicketTotals {
            net_total: t.net_total,
            tax_total: t.tax_total,
            grand_total: t.grand_total,
            rounding_adjustment: t.rounding_adjustment,
            rounded_total: t.rounded_total,
            paid_total: t.paid_total,
            change_due: t.change_due,
        },
    }
}

/// Whether a replay is the one that completes the payment: the ticket was not paid up before it
/// and is now. Only that replay triggers recognition.
fn crosses_full_payment(was_full: bool, rounded_total: Decimal, paid_total: Decimal) -> bool {
    !was_full && rounded_total > Decimal::ZERO && paid_total >= rounded_total
}

/// A replay's tenders may overpay only in cash: the change the drawer hands back must be cash it
/// took. Equivalently, the tenders other than cash cover at most the rounded total.
fn check_replay_change_is_cash(s: &NewSyncSale, rounded_total: Decimal) -> Result<(), PosError> {
    let non_cash = s.tenders.iter().filter(|t| t.method != "cash").map(|t| money(t.amount)).sum::<Decimal>();
    if non_cash > rounded_total.max(Decimal::ZERO) {
        let method = s.tenders.iter().find(|t| t.method != "cash").map(|t| t.method.clone()).unwrap_or_default();
        return Err(PosError::NonCashOverpayment { method, remaining: rounded_total.max(Decimal::ZERO) });
    }
    Ok(())
}

#[cfg(test)]
mod crossing_tests {
    use super::crosses_full_payment;
    use rust_decimal::Decimal;

    #[test]
    fn only_the_replay_that_completes_payment_triggers_recognition() {
        let d = |s: &str| s.parse::<Decimal>().unwrap();
        assert!(crosses_full_payment(false, d("100"), d("100")));
        assert!(!crosses_full_payment(true, d("100"), d("120")), "already paid up: no re-trigger");
        assert!(!crosses_full_payment(false, d("100"), d("99.99")));
        assert!(!crosses_full_payment(false, d("0"), d("0")), "a zero ticket is not a sale to recognise");
    }
}