merge: P4b S6, paying on terms (branch S6, 6c4480cd)

The third of the paused branches: Ledger::settle with discounts and the
processor's fee (kernel::settle, Kani settle_is_exact, Lean
settle_posts_a_document_step), books.receive_payment and books.pay_bill
with applications, books.bills_due, the agings' detail and tie-out, the
aging exports and the CPA package's aging CSVs, the handlers in
tools/settlements.rs. Twelve files conflicted with the S4.4 and S5
merges, resolved as plan 8.0.2 says: both routers; both test appends
(the shared match arm in arap_standing.rs spliced into both tests; the
shared `.unwrap()` in store.rs); the scope table at 124; one
invoices-and-bills handbook (S5's send step 1 with S6's steps 2, 3, 5
and procedures) registered once; docs/mcp-interface.md with S4.4's
create docs and S6's payment docs; S5's law renumbered 35 and S6's 36
(S1's is 34); the parity rows and sections of both. S6's wire tests
create their bills as S4.4's contract now requires (confirmed, the
vendor's number, a line account, the vendor's invoice uploaded) and live
in their own module beside S4.4's tests.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HS8WZziDnyxunC23MUxrLp

crates/ledger-package/src/aging.rs

@@ -0,0 +1,216 @@
+//! The receivables and payables agings as files (plan P4b S6, 8.3.10;
+//! rules.md B-18, B-23): one row per open document, and a tie-out line
+//! against the control account. The server's `books.export` and the CPA
+//! package build the same CSV from this, and its XLSX/PDF from
+//! [`aging_statement`], so a CPA's two copies can't differ.
+
+use ledger_core::{DocRef, Ledger};
+use rust_decimal::Decimal;
+
+use crate::text::{csv_escape, money};
+
+/// The CSV's header: one row per open document (8.3.10).
+pub const AGING_CSV_HEADER: &str =
+    "number,party,date,due_date,terms,total,paid,discounted,outstanding,bucket,days_overdue";
+
+/// One aging's rows and tie-out as CSV: the header, one row per open
+/// invoice (`invoices` true) or bill, then `TOTAL,,,,,,,,<Σ
+/// outstanding>,GL <account> <balance>,difference <difference>`.
+pub fn aging_csv(
+    ledger: &Ledger,
+    invoices: bool,
+    as_of: chrono::NaiveDate,
+) -> Result<String, String> {
+    let docs = ledger
+        .aging_documents(as_of, invoices)
+        .map_err(|e| e.to_string())?;
+    let mut out = String::from(AGING_CSV_HEADER);
+    out.push('\n');
+    let mut total = Decimal::ZERO;
+    for d in &docs {
+        total += d.outstanding;
+        out.push_str(&format!(
+            "{},{},{},{},{},{},{},{},{},{},{}\n",
+            csv_escape(&number(ledger, d.doc)),
+            csv_escape(&d.party),
+            d.date,
+            d.due_date,
+            csv_escape(d.terms.as_deref().unwrap_or("")),
+            money(d.total),
+            money(d.paid),
+            money(d.discounted),
+            money(d.outstanding),
+            d.bucket,
+            d.days_overdue,
+        ));
+    }
+    let (code, balance, difference) = tie_out(ledger, invoices, as_of)?;
+    let account = if code.is_empty() {
+        "GL —".to_string()
+    } else {
+        format!("GL {code}")
+    };
+    out.push_str(&format!(
+        "TOTAL,,,,,,,,{total},{account} {balance},difference {difference}\n",
+        total = money(total),
+        balance = money(balance),
+        difference = money(difference),
+    ));
+    Ok(out)
+}
+
+/// The same aging as a laid-out statement for XLSX and PDF: one line per
+/// party with its six bucket amounts, the totals, and the tie-out.
+pub fn aging_statement(
+    ledger: &Ledger,
+    invoices: bool,
+    as_of: chrono::NaiveDate,
+) -> Result<ledger_import::Statement, String> {
+    use ledger_import::report::{Row, RowKind, Statement};
+    let party_rows = if invoices {
+        ledger.ar_aging(as_of)
+    } else {
+        ledger.ap_aging(as_of)
+    }
+    .map_err(|e| e.to_string())?;
+    let (code, balance, difference) = tie_out(ledger, invoices, as_of)?;
+    let columns: Vec<String> = ["Current", "1-30", "31-60", "61-90", "90+", "Total"]
+        .into_iter()
+        .map(str::to_string)
+        .collect();
+    let mut out_rows: Vec<Row> = vec![Row {
+        kind: RowKind::Section,
+        label: if invoices {
+            "Receivables".into()
+        } else {
+            "Payables".into()
+        },
+        amounts: vec![],
+        currency: false,
+        rule_above: false,
+    }];
+    let (mut current, mut d30, mut d60, mut d90, mut d90p) = (
+        Decimal::ZERO,
+        Decimal::ZERO,
+        Decimal::ZERO,
+        Decimal::ZERO,
+        Decimal::ZERO,
+    );
+    for r in &party_rows {
+        let total = r.total().map_err(|e| e.to_string())?;
+        current += r.current;
+        d30 += r.days_30;
+        d60 += r.days_60;
+        d90 += r.days_90;
+        d90p += r.days_90_plus;
+        out_rows.push(Row {
+            kind: RowKind::Line,
+            label: r.name.clone(),
+            amounts: vec![
+                Some(r.current),
+                Some(r.days_30),
+                Some(r.days_60),
+                Some(r.days_90),
+                Some(r.days_90_plus),
+                Some(total),
+            ],
+            currency: false,
+            rule_above: false,
+        });
+    }
+    let total = current + d30 + d60 + d90 + d90p;
+    out_rows.push(Row {
+        kind: RowKind::Total,
+        label: "Total".into(),
+        amounts: vec![
+            Some(current),
+            Some(d30),
+            Some(d60),
+            Some(d90),
+            Some(d90p),
+            Some(total),
+        ],
+        currency: true,
+        rule_above: true,
+    });
+    out_rows.push(Row {
+        kind: RowKind::Spacer,
+        label: String::new(),
+        amounts: vec![],
+        currency: false,
+        rule_above: false,
+    });
+    out_rows.push(Row {
+        kind: RowKind::Section,
+        label: "Tie-out".into(),
+        amounts: vec![],
+        currency: false,
+        rule_above: false,
+    });
+    out_rows.push(Row {
+        kind: RowKind::Line,
+        label: if code.is_empty() {
+            "GL balance".to_string()
+        } else {
+            format!("GL {code} balance")
+        },
+        amounts: vec![None, None, None, None, None, Some(balance)],
+        currency: false,
+        rule_above: false,
+    });
+    out_rows.push(Row {
+        kind: RowKind::Total,
+        label: "Difference".into(),
+        amounts: vec![None, None, None, None, None, Some(difference)],
+        currency: true,
+        rule_above: true,
+    });
+    Ok(Statement {
+        // Excel sheet names take no slash; the statement's title is the
+        // one both XLSX and PDF draw.
+        title: if invoices {
+            "AR Aging".into()
+        } else {
+            "AP Aging".into()
+        },
+        period: format!("As of {}", as_of.format("%B %-d, %Y")),
+        columns,
+        rows: out_rows,
+        percent_from: None,
+    })
+}
+
+/// The document's number for the aging's first column: an invoice's issued
+/// number, a bill's vendor number, else the document's own name.
+fn number(ledger: &Ledger, doc: DocRef) -> String {
+    match doc {
+        DocRef::Invoice(id) => ledger
+            .get_invoice(id)
+            .and_then(|i| i.number.clone())
+            .unwrap_or_else(|| format!("Invoice {id}")),
+        DocRef::Bill(id) => ledger
+            .get_bill(id)
+            .and_then(|b| b.vendor_ref.clone())
+            .unwrap_or_else(|| format!("Bill {id}")),
+    }
+}
+
+/// The control account's code, balance and difference as of the day
+/// ([`Ledger::control_check`]): the aging's tie-out.
+fn tie_out(
+    ledger: &Ledger,
+    invoices: bool,
+    as_of: chrono::NaiveDate,
+) -> Result<(String, Decimal, Decimal), String> {
+    let role = if invoices { "receivables" } else { "payables" };
+    let checks = ledger.control_check(as_of).map_err(|e| e.to_string())?;
+    let Some(check) = checks.iter().find(|c| c.role == role) else {
+        return Ok((String::new(), Decimal::ZERO, Decimal::ZERO));
+    };
+    let code = ledger
+        .chart()
+        .get(check.account)
+        .map(|a| a.code.clone())
+        .unwrap_or_default();
+    Ok((code, check.balance, check.difference))
+}

crates/ledger-package/src/lib.rs

@@ -23,6 +23,7 @@
 //!      whichever [`PackageBooks`] they are read through.
 //! ```
 
+mod aging;
 mod attention;
 mod books;
 mod iif;
@@ -34,6 +35,7 @@ mod text;
 mod tins;
 mod vendor_1099;
 
+pub use aging::{AGING_CSV_HEADER, aging_csv, aging_statement};
 pub use attention::{
     Attention, Integrity, Report, Severity, Target, files_1099, find, find_with, reconcile_prompt,
     w9_missing, w9_prompt,

crates/ledger-package/src/package.rs

@@ -372,6 +372,17 @@ pub fn build_package<B: PackageBooks + ?Sized>(
         files.push((format!("{name}.pdf"), pdf(st)?));
         files.push((format!("{name}.xlsx"), xlsx(XlsxReport::Statement(st))?));
     }
+    // The receivables and payables agings, each with its tie-out line to
+    // the control account (B-23, 8.3.10): the same CSV books.export and
+    // the viewer make.
+    files.push((
+        "ar_aging.csv".into(),
+        crate::aging::aging_csv(ledger, true, as_of)?.into_bytes(),
+    ));
+    files.push((
+        "ap_aging.csv".into(),
+        crate::aging::aging_csv(ledger, false, as_of)?.into_bytes(),
+    ));
     // The fixed asset register, when an asset was acquired by as_of (one
     // acquired later is not in it, so neither is an empty register).
     if ledger
@@ -566,7 +577,7 @@ pub fn build_package<B: PackageBooks + ?Sized>(
     let year_end = NaiveDate::from_ymd_opt(year, 12, 31) == Some(as_of);
     let include_tins = tins.is_some();
     let readme = format!(
-        "{name} — books package for the CPA\n\nFiscal year to date: {fy_start} through {as_of_s}. {basis} basis.\nKept in wanderbooks: double-entry books from an append-only, hash-chained journal ({seq} events, verified).\n\nStatements (PDF and XLSX): profit and loss, balance sheet, cash flow, {members}tax summary, trial balance.\nLedgers (XLSX): general ledger by account; general journal entry by entry.\n{iif}{worksheet}{k1}{receipts}{tins}\nThe tax summary maps accounts to return categories; it's a worksheet, not a filing. Questions go to the owners, who can ask their bookkeeping agent to trace any number to its entries and receipts.\n",
+        "{name} — books package for the CPA\n\nFiscal year to date: {fy_start} through {as_of_s}. {basis} basis.\nKept in wanderbooks: double-entry books from an append-only, hash-chained journal ({seq} events, verified).\n\nStatements (PDF and XLSX): profit and loss, balance sheet, cash flow, {members}tax summary, trial balance.\nLedgers (XLSX): general ledger by account; general journal entry by entry.\nAgings (CSV): ar_aging.csv and ap_aging.csv, one row per open invoice or bill, each ending with a TOTAL line that ties to its control account (B-23). Early-payment discounts are taken by the gross method (A-8); bad debts are written off directly (A-5).\n{iif}{worksheet}{k1}{receipts}{tins}\nThe tax summary maps accounts to return categories; it's a worksheet, not a filing. Questions go to the owners, who can ask their bookkeeping agent to trace any number to its entries and receipts.\n",
         name = company.name,
         basis = company.basis,
         members = if company.members.is_empty() {