evidence-dsl/tests/EvidenceComposition.test.js

/**
 * tests/EvidenceComposition.test.js — referencing a derived evidence as a
 * sub-rule of another evidence (WHEN can_read(user, doc) where can_read is
 * itself an evidence).
 *
 * Composition is resolved at COMPILE time: the generator inlines each
 * evidence reference with the referenced evidence's own config (a linker
 * pass that handles forward references and rejects cycles), so the engine
 * evaluates a fully-resolved, acyclic config tree.
 */
import { describe, it } from 'node:test';
import assert from 'node:assert/strict';
import { Arbiter } from '@arbiter/core';
import { DSLCompiler } from '../src/DSLCompiler.js';
import { DSLRuntime } from '../src/runtime/DSLRuntime.js';
import { DSLValueGraph } from '../src/value-graph/DSLValueGraph.js';

const DEFS = `
  definition Employee { id: string }
  definition Group { id: string }
  definition Doc { id: string }
  fact owns(user: Employee, doc: Doc)
  fact *trusted(user: Employee)
  fact member_of(user: Employee, group: Group)
  fact can_access(group: Group, doc: Doc)
`;

function compile(dsl, name = 'compose') {
  const arb = new Arbiter();
  const compiler = new DSLCompiler(arb);
  const result = compiler.compile(dsl, name);
  return { arb, result };
}

describe('Evidence composition', () => {
  it('composes a direct evidence into another evidence', () => {
    const { arb, result } = compile(`
      ${DEFS}
      evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }
      evidence can_browse(user: Employee, doc: Doc) { can_read(user, doc) }
    `);
    assert.ok(result.success, JSON.stringify(result.errors));
    arb.addNode('u:1', 'Employee'); arb.addNode('doc:9', 'Doc');
    arb.addRelation('u:1', 'owns', 'doc:9', { possibility: 0.8 });
    const res = arb.check('u:1', 'can_browse', 'doc:9');
    assert.equal(res.possibility, 0.8);
    // The reference is inlined to the underlying fact config.
    assert.equal(arb.relationConfigs.get('can_browse').type, 'direct');
    assert.equal(arb.relationConfigs.get('can_browse').relation, 'owns');
  });

  it('composes an evidence inside a defeasible WHEN/UNLESS', () => {
    const { arb, result } = compile(`
      ${DEFS}
      evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }
      evidence can_open(user: Employee, doc: Doc) { WHEN can_read(user, doc) UNLESS trusted(user) }
    `);
    assert.ok(result.success, JSON.stringify(result.errors));
    arb.addNode('u:1', 'Employee'); arb.addNode('doc:9', 'Doc');
    arb.addRelation('u:1', 'owns', 'doc:9', { possibility: 0.9 });
    assert.equal(arb.check('u:1', 'can_open', 'doc:9').possibility, 0.9);
    arb.addRelation('u:1', 'trusted', 'u:1', { possibility: 1.0 });
    const denied = arb.check('u:1', 'can_open', 'doc:9');
    assert.equal(denied.possibility, 0);
    assert.equal(denied.reason, 'defeated_by_unless');
  });

  it('composes a chain evidence into another evidence', () => {
    const { arb, result } = compile(`
      ${DEFS}
      evidence can_enter(user: Employee, doc: Doc) { member_of(user, *g) { can_access(g, doc) } }
      evidence can_work(user: Employee, doc: Doc) { can_enter(user, doc) }
    `);
    assert.ok(result.success, JSON.stringify(result.errors));
    arb.addNode('u:1', 'Employee'); arb.addNode('g:1', 'Group'); arb.addNode('doc:9', 'Doc');
    arb.addRelation('u:1', 'member_of', 'g:1', { possibility: 1.0 });
    arb.addRelation('g:1', 'can_access', 'doc:9', { possibility: 0.7 });
    const res = arb.check('u:1', 'can_work', 'doc:9');
    assert.equal(res.possibility, 0.7);
    assert.equal(arb.relationConfigs.get('can_work').type, 'chain');
  });

  it('composes transitively (A → B → fact) and re-derives dependencies', () => {
    const { arb, result } = compile(`
      ${DEFS}
      evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }
      evidence can_browse(user: Employee, doc: Doc) { can_read(user, doc) }
      evidence can_open(user: Employee, doc: Doc) { can_browse(user, doc) }
    `);
    assert.ok(result.success, JSON.stringify(result.errors));
    arb.addNode('u:1', 'Employee'); arb.addNode('doc:9', 'Doc');
    arb.addRelation('u:1', 'owns', 'doc:9', { possibility: 0.6 });
    assert.equal(arb.check('u:1', 'can_open', 'doc:9').possibility, 0.6);
    assert.deepEqual(arb.relationConfigs.get('can_open').dependsOn, ['owns']);
  });

  it('composes a value-carrying evidence and preserves subject-as-object scope', () => {
    const { arb, result } = compile(`
      ${DEFS}
      fact *user_risk(user: Employee, value: number)
      evidence risk_ok(user: Employee, doc: Doc) { user_risk(user, 1) }
      evidence can_proceed(user: Employee, doc: Doc) { risk_ok(user, doc) }
    `);
    assert.ok(result.success, JSON.stringify(result.errors));
    arb.addNode('u:1', 'Employee'); arb.addNode('doc:9', 'Doc');
    arb.addRelation('u:1', 'user_risk', 'u:1', { possibility: 1.0, value: 1 });
    const res = arb.check('u:1', 'can_proceed', 'doc:9');
    assert.equal(res.possibility, 1);
  });

  it('composes evidence inside a comparator operand', () => {
    const { arb, result } = compile(`
      ${DEFS}
      fact *user_risk(user: Employee, value: number)
      fact *risk_limit(doc: Doc, value: number)
      evidence user_risk_ok(user: Employee, doc: Doc) { user_risk(user, 1) }
      evidence can_proceed(user: Employee, doc: Doc) { user_risk_ok(user, doc) }
    `);
    assert.ok(result.success, JSON.stringify(result.errors));
    arb.addNode('u:1', 'Employee'); arb.addNode('doc:9', 'Doc');
    arb.addRelation('u:1', 'user_risk', 'u:1', { possibility: 1.0, value: 1 });
    assert.equal(arb.check('u:1', 'can_proceed', 'doc:9').possibility, 1);
  });

  it('rejects cyclic evidence references at compile time', () => {
    const { result } = compile(`
      ${DEFS}
      evidence a(user: Employee, doc: Doc) { b(user, doc) }
      evidence b(user: Employee, doc: Doc) { a(user, doc) }
    `);
    assert.equal(result.success, false);
    assert.ok(result.errors.some(e => /[Cc]yclic/.test(e)), JSON.stringify(result.errors));
  });

  it('rejects self-referencing evidence at compile time', () => {
    const { result } = compile(`
      ${DEFS}
      evidence a(user: Employee, doc: Doc) { a(user, doc) }
    `);
    assert.equal(result.success, false);
    assert.ok(result.errors.some(e => /[Cc]yclic/.test(e)), JSON.stringify(result.errors));
  });

  it('keeps the referenced evidence checkable in its own right', () => {
    const { arb, result } = compile(`
      ${DEFS}
      evidence can_read(user: Employee, doc: Doc) { owns(user, doc) }
      evidence can_browse(user: Employee, doc: Doc) { can_read(user, doc) }
    `);
    assert.ok(result.success);
    arb.addNode('u:1', 'Employee'); arb.addNode('doc:9', 'Doc');
    arb.addRelation('u:1', 'owns', 'doc:9', { possibility: 0.5 });
    assert.equal(arb.check('u:1', 'can_read', 'doc:9').possibility, 0.5);
    assert.equal(arb.check('u:1', 'can_browse', 'doc:9').possibility, 0.5);
  });

  describe('measure + evidence composition', () => {
    const M_DEFS = `
      definition Employee { id: string }
      measure budget_used(user: Employee) { } PROVIDES number
      measure budget_limit(user: Employee) { } PROVIDES number
      evidence can_use(user: Employee, doc: string) { budget_used(user) <= budget_limit(user) }
    `;

    it('compiles an evidence comparator over measure valueRelations', () => {
      const { arb, result } = compile(M_DEFS, 'm+e-compile');
      assert.ok(result.success, JSON.stringify(result.errors));
      const cfg = arb.relationConfigs.get('can_use');
      assert.equal(cfg.type, 'relational_comparator');
      assert.equal(cfg.left.valueRelation, 'budget_used');
      assert.equal(cfg.right.valueRelation, 'budget_limit');
      assert.deepEqual(cfg.dependsOn, ['budget_used', 'budget_limit']);
      assert.equal(cfg._needsValues, true);
    });

    it('evaluates with measure values from registered providers (measure → evidence)', async () => {
      const rt = new DSLRuntime(new Arbiter()).compile(M_DEFS, 'm+e-provider');
      const dvg = new DSLValueGraph(rt);
      dvg.attach(); // wires runtime.measure through the value-graph
      rt.registerMeasure('budget_used', async () => ({ value: 900 }));
      rt.registerMeasure('budget_limit', async () => ({ value: 1000 }));
      rt.arbiter.addNode('u:1', 'Employee');

      // Both systems live: the measure resolves standalone...
      assert.equal((await rt.measure('budget_used', { user: 'u:1' })).value, 900);
      // ...and composes into the evidence comparator.
      const allow = await rt.check('u:1', 'can_use', 'doc:9');
      assert.equal(allow.possibility, 1);
      assert.equal(allow.reason, 'allow_rule_matched');
      assert.ok(allow.providedFacts.includes('budget_used'), 'measure injected as a partial-graph edge');
    });

    it('evaluates with measure values stored in the value-graph (setValue)', async () => {
      const rt = new DSLRuntime(new Arbiter()).compile(M_DEFS, 'm+e-vg');
      const dvg = new DSLValueGraph(rt);
      dvg.attach();
      dvg.setValue('budget_used', { __subject: 'u:1', user: 'u:1' }, 900);
      dvg.setValue('budget_limit', { __subject: 'u:1', user: 'u:1' }, 1000);
      rt.arbiter.addNode('u:1', 'Employee');

      const allow = await rt.check('u:1', 'can_use', 'doc:9');
      assert.equal(allow.possibility, 1, 'in-budget evidence allowed from graph-sourced measures');

      // Over budget → the comparator denies.
      const rt2 = new DSLRuntime(new Arbiter()).compile(M_DEFS, 'm+e-vg2');
      const dvg2 = new DSLValueGraph(rt2);
      dvg2.attach();
      dvg2.setValue('budget_used', { __subject: 'u:1', user: 'u:1' }, 1200);
      dvg2.setValue('budget_limit', { __subject: 'u:1', user: 'u:1' }, 1000);
      rt2.arbiter.addNode('u:1', 'Employee');
      const deny = await rt2.check('u:1', 'can_use', 'doc:9');
      assert.equal(deny.possibility, 0);
      assert.equal(deny.reason, 'values_compared_comparison_false');
    });
  });
});