PR S: Machine-form obligation layer (terms-as-data) (#23)

orchestrator/src/services/obligations/index.ts

@@ -0,0 +1,320 @@
+/**
+ * Machine-form obligation layer — entry point.
+ *
+ * See ./types.ts for the architectural shape; this module exposes:
+ *   - canonicalize / hashObligationTerms (deterministic identity)
+ *   - validateObligationTerms            (shape check)
+ *   - evaluateObligationTerms            (run commit/abort/unwind
+ *                                          clauses against a context
+ *                                          via the PR P rules engine)
+ *   - buildIssueInstrumentObligation     (helper that derives a
+ *                                          sensible default obligation
+ *                                          shape from a plan's
+ *                                          instrument terms)
+ */
+
+import { createHash } from "crypto";
+import { evaluateCondition } from "./evaluator";
+import type { InstrumentTerms } from "../../types/plan";
+import type {
+  AuthorizedParticipant,
+  Consideration,
+  EvaluationResult,
+  GoverningDocument,
+  ObligationClause,
+  ObligationEvaluation,
+  ObligationTerms,
+} from "./types";
+
+export * from "./types";
+
+/**
+ * Deterministic canonical JSON encoding: object keys sorted
+ * lexicographically at every depth, arrays preserved, no whitespace.
+ *
+ * This is what `hashObligationTerms()` hashes, so two obligations
+ * with identical semantic content always hash to the same value
+ * regardless of key insertion order.
+ */
+export function canonicalize(value: unknown): string {
+  return JSON.stringify(sortValue(value));
+}
+
+function sortValue(v: unknown): unknown {
+  if (v === null || typeof v !== "object") return v;
+  if (Array.isArray(v)) return v.map((x) => sortValue(x));
+  const out: Record<string, unknown> = {};
+  for (const k of Object.keys(v as Record<string, unknown>).sort()) {
+    out[k] = sortValue((v as Record<string, unknown>)[k]);
+  }
+  return out;
+}
+
+/**
+ * SHA-256 of the canonical obligation terms, hex-encoded without
+ * 0x prefix. Matches the formatting convention used by
+ * `InstrumentTerms.templateHash`.
+ */
+export function hashObligationTerms(terms: ObligationTerms): string {
+  return createHash("sha256").update(canonicalize(terms)).digest("hex");
+}
+
+/**
+ * Shape validation. Returns a list of human-readable problems; empty
+ * list means the object conforms to `ObligationTerms`.
+ *
+ * Intentionally cheap (no JSON-Schema runtime) — the TypeScript type
+ * plus these assertions catch the bulk of real-world mistakes.
+ */
+export function validateObligationTerms(
+  input: unknown,
+): { ok: boolean; errors: string[] } {
+  const errors: string[] = [];
+  if (!input || typeof input !== "object") {
+    return { ok: false, errors: ["obligation terms must be an object"] };
+  }
+  const t = input as Partial<ObligationTerms>;
+
+  if (t.version !== "1.0") errors.push("version must be \"1.0\"");
+
+  if (!t.consideration || typeof t.consideration !== "object") {
+    errors.push("consideration missing");
+  } else {
+    const c = t.consideration as Partial<Consideration>;
+    if (!c.payor) errors.push("consideration.payor required");
+    if (!c.payee) errors.push("consideration.payee required");
+    if (!c.currency || !/^[A-Z]{3}$/.test(c.currency))
+      errors.push("consideration.currency must be ISO-4217 (3 uppercase letters)");
+    if (typeof c.amount !== "number" || !(c.amount > 0))
+      errors.push("consideration.amount must be a positive number");
+  }
+
+  for (const arrKey of [
+    "validIssuance",
+    "validPayment",
+    "commit",
+    "abort",
+    "unwind",
+  ] as const) {
+    const arr = t[arrKey];
+    if (!Array.isArray(arr)) {
+      errors.push(`${arrKey} must be an array`);
+      continue;
+    }
+    arr.forEach((clause, i) => {
+      if (!clause || typeof clause !== "object") {
+        errors.push(`${arrKey}[${i}] must be an object`);
+        return;
+      }
+      const c = clause as Partial<ObligationClause>;
+      if (!c.id) errors.push(`${arrKey}[${i}].id required`);
+      if (!c.description) errors.push(`${arrKey}[${i}].description required`);
+      if (!c.assert) errors.push(`${arrKey}[${i}].assert required`);
+      if (c.binds && !["instrument", "payment", "both"].includes(c.binds))
+        errors.push(`${arrKey}[${i}].binds must be instrument|payment|both`);
+    });
+  }
+
+  if (!Array.isArray(t.authorizedParticipants)) {
+    errors.push("authorizedParticipants must be an array");
+  } else {
+    t.authorizedParticipants.forEach((p, i) => {
+      const pp = p as Partial<AuthorizedParticipant>;
+      if (!pp.role) errors.push(`authorizedParticipants[${i}].role required`);
+      if (!pp.actorId)
+        errors.push(`authorizedParticipants[${i}].actorId required`);
+    });
+  }
+
+  if (!Array.isArray(t.governingDocuments) || t.governingDocuments.length === 0) {
+    errors.push("governingDocuments must be a non-empty array");
+  } else {
+    t.governingDocuments.forEach((d, i) => {
+      const dd = d as Partial<GoverningDocument>;
+      if (!dd.templateRef)
+        errors.push(`governingDocuments[${i}].templateRef required`);
+      if (!dd.templateHash || !/^[0-9a-fA-F]{64}$/.test(dd.templateHash))
+        errors.push(`governingDocuments[${i}].templateHash must be hex SHA-256`);
+    });
+  }
+
+  return { ok: errors.length === 0, errors };
+}
+
+/**
+ * Evaluate a set of obligation clauses against a live context.
+ *
+ * `context` typically contains the plan, execution state, event chain,
+ * and bank/DLT dispatch evidence — whatever the clauses assert against.
+ *
+ * A failure short-circuits nothing; all clauses are evaluated so the
+ * caller can surface the full list of unmet conditions (arch §12.2).
+ */
+export function evaluateClauses(
+  clauses: ObligationClause[],
+  context: Record<string, unknown>,
+): ObligationEvaluation {
+  const results: EvaluationResult[] = clauses.map((clause) => {
+    let ok = false;
+    let failureReason: string | undefined;
+    try {
+      ok = evaluateCondition(clause.assert, context);
+      if (!ok) failureReason = "assert condition returned false";
+    } catch (err) {
+      ok = false;
+      failureReason =
+        err instanceof Error ? err.message : "unknown evaluator error";
+    }
+    return {
+      clauseId: clause.id,
+      description: clause.description,
+      ok,
+      ...(failureReason ? { failureReason } : {}),
+    };
+  });
+  return { ok: results.every((r) => r.ok), results };
+}
+
+/**
+ * Evaluate specifically the commit clauses. Convenience for the
+ * transition coordinator (arch §9.2).
+ */
+export function evaluateCommit(
+  terms: ObligationTerms,
+  context: Record<string, unknown>,
+): ObligationEvaluation {
+  return evaluateClauses(terms.commit, context);
+}
+
+/**
+ * Evaluate specifically the abort clauses (arch §9.3). A true result
+ * here means the transaction MUST abort.
+ */
+export function evaluateAbort(
+  terms: ObligationTerms,
+  context: Record<string, unknown>,
+): ObligationEvaluation {
+  const ev = evaluateClauses(terms.abort, context);
+  // Semantically an abort clause that *asserts true* means the abort
+  // condition has been hit, so `ok=true` in the evaluation result ==
+  // "abort required". Callers consume this as a boolean trigger.
+  return ev;
+}
+
+/**
+ * Derive a default obligation-terms object from an issueInstrument
+ * step's instrument terms. Useful for plans that haven't supplied an
+ * explicit obligation block — gives them a reasonable starting point
+ * that matches the template's commit/abort semantics.
+ */
+export function buildIssueInstrumentObligation(input: {
+  instrument: InstrumentTerms;
+  payor: string;
+  payee: string;
+  authorizedParticipants: AuthorizedParticipant[];
+  governingDocumentTitle?: string;
+}): ObligationTerms {
+  const { instrument, payor, payee, authorizedParticipants } = input;
+
+  const commit: ObligationClause[] = [
+    {
+      id: "commit.dlt_tx_hash",
+      description: "DLT anchor transaction hash is present and valid",
+      binds: "both",
+      assert: {
+        path: "dlt.tx_hash",
+        op: "matches",
+        value: "^0x[0-9a-fA-F]{64}$",
+      },
+    },
+    {
+      id: "commit.bank_iso_message_id",
+      description: "Bank leg has produced an ISO-20022 message id",
+      binds: "instrument",
+      assert: { path: "bank.iso_message_id", op: "exists" },
+    },
+    {
+      id: "commit.state_is_validating",
+      description: "Transaction must be in VALIDATING when commit fires",
+      binds: "both",
+      assert: { path: "state", op: "eq", value: "VALIDATING" },
+    },
+  ];
+
+  const abort: ObligationClause[] = [
+    {
+      id: "abort.exception_raised",
+      description: "At least one active exception blocks commit",
+      binds: "both",
+      assert: { path: "exceptions.active", op: "length_gte", value: 1 },
+    },
+  ];
+
+  const unwind: ObligationClause[] = [
+    {
+      id: "unwind.payment_failed_only",
+      description:
+        "Unwind applies only when the payment leg failed AFTER the "
+        + "instrument was dispatched (MT760 is irrevocable under UCP 600).",
+      binds: "payment",
+      assert: {
+        all: [
+          { path: "instrument.dispatched", op: "eq", value: true },
+          { path: "payment.failed", op: "eq", value: true },
+        ],
+      },
+    },
+  ];
+
+  const validIssuance: ObligationClause[] = [
+    {
+      id: "issuance.template_hash_matches",
+      description: "Dispatched instrument text hashes to the agreed template",
+      binds: "instrument",
+      assert: {
+        path: "instrument.template_hash",
+        op: "eq",
+        value: instrument.templateHash,
+      },
+    },
+  ];
+
+  const validPayment: ObligationClause[] = [
+    {
+      id: "payment.amount_matches",
+      description: "Payment amount equals the instrument face value",
+      binds: "payment",
+      assert: { path: "payment.amount", op: "eq", value: instrument.amount },
+    },
+    {
+      id: "payment.currency_matches",
+      description: "Payment currency equals the instrument currency",
+      binds: "payment",
+      assert: { path: "payment.currency", op: "eq", value: instrument.currency },
+    },
+  ];
+
+  return {
+    version: "1.0",
+    consideration: {
+      payor,
+      payee,
+      currency: instrument.currency,
+      amount: instrument.amount,
+    },
+    validIssuance,
+    validPayment,
+    commit,
+    abort,
+    unwind,
+    authorizedParticipants,
+    governingDocuments: [
+      {
+        templateRef: instrument.templateRef,
+        templateHash: instrument.templateHash,
+        title: input.governingDocumentTitle,
+        governingLaw: instrument.governingLaw,
+      },
+    ],
+  };
+}