/**
 * G6 — Conflict resolution ordering
 *
 * Pararules origin: tests/test2.nim "recursion limit" (rule1/rule2/rule3 cascade)
 * and SPEC.md §Conflict Resolution which defines salience → specificity → addedAt.
 *
 * Pararules uses salience in rule declarations to control firing order.
 * Our engine implements the same three-key sort via orderActivations():
 *   1. Salience descending
 *   2. Specificity (# conditions) descending
 *   3. Insertion order ascending
 *
 * This golden test verifies the pure ordering function, which is the
 * conflict-resolution kernel that the future agenda will call.
 */
import { describe, it, expect } from "vitest";
import { orderActivations } from "../../src/conflict.js";
import { Token } from "../../src/beta.js";
import { Session } from "../../src/session.js";
import { HandlerRegistry } from "../../src/registry.js";
import { defineRule, v } from "../../src/builder.js";
import type { Activation, OrderableRule } from "../../src/conflict.js";
import type { EntityId } from "../../src/schema.js";
import type { TokenFact } from "../../src/beta.js";

const ROOT_FACT: TokenFact = { id: 0 as EntityId, attr: "__root", value: null };
const dummyToken = new Token(null, ROOT_FACT, {});

function mkActivation(
  name: string,
  salience: number,
  conditionCount: number,
  addedAt: number,
): Activation {
  const rule: OrderableRule = {
    name,
    salience,
    conditions: Array.from({ length: conditionCount }, () => ({})),
    handler: "noop",
    addedAt,
  };
  return { rule, token: dummyToken };
}

describe("G6 — conflict resolution ordering", () => {
  it("higher salience fires first", () => {
    const activations = [
      mkActivation("low", 0, 1, 0),
      mkActivation("high", 10, 1, 1),
      mkActivation("mid", 5, 1, 2),
    ];

    const ordered = orderActivations(activations);
    expect(ordered[0]?.rule.name).toBe("high");
    expect(ordered[1]?.rule.name).toBe("mid");
    expect(ordered[2]?.rule.name).toBe("low");
  });

  it("salience ties broken by specificity (more conditions wins)", () => {
    const activations = [
      mkActivation("oneCondition", 10, 1, 0),
      mkActivation("twoConditions", 10, 2, 1),
      mkActivation("threeConditions", 10, 3, 2),
    ];

    const ordered = orderActivations(activations);
    expect(ordered[0]?.rule.name).toBe("threeConditions");
    expect(ordered[1]?.rule.name).toBe("twoConditions");
    expect(ordered[2]?.rule.name).toBe("oneCondition");
  });

  it("salience and specificity ties broken by insertion order ascending", () => {
    const activations = [
      mkActivation("added2", 5, 2, 2),
      mkActivation("added0", 5, 2, 0),
      mkActivation("added1", 5, 2, 1),
    ];

    const ordered = orderActivations(activations);
    expect(ordered[0]?.rule.name).toBe("added0");
    expect(ordered[1]?.rule.name).toBe("added1");
    expect(ordered[2]?.rule.name).toBe("added2");
  });

  it("mixed case: salience, then specificity, then addedAt", () => {
    const activations = [
      mkActivation("ruleC", 5, 3, 2),   // low salience, many conditions
      mkActivation("ruleA", 10, 1, 0),  // high salience, 1 condition
      mkActivation("ruleB", 10, 2, 1),  // high salience, 2 conditions
    ];

    const ordered = orderActivations(activations);
    // B > A (same salience, B has more conditions)
    // A > C (higher salience)
    expect(ordered[0]?.rule.name).toBe("ruleB");
    expect(ordered[1]?.rule.name).toBe("ruleA");
    expect(ordered[2]?.rule.name).toBe("ruleC");
  });

  it("empty activations list → empty result", () => {
    expect(orderActivations([])).toHaveLength(0);
  });

  it("single activation → unchanged", () => {
    const single = [mkActivation("only", 10, 2, 0)];
    const ordered = orderActivations(single);
    expect(ordered).toHaveLength(1);
    expect(ordered[0]?.rule.name).toBe("only");
  });

  it("orderActivations does not mutate the input array", () => {
    const activations = [
      mkActivation("b", 5, 1, 0),
      mkActivation("a", 10, 1, 1),
    ];
    const original = [...activations];
    orderActivations(activations);
    expect(activations[0]?.rule.name).toBe(original[0]?.rule.name);
    expect(activations[1]?.rule.name).toBe(original[1]?.rule.name);
  });

  it("Session._getOrderableRules returns rules in addedAt order with correct salience", () => {
    const registry = new HandlerRegistry();
    registry.register("noop", () => {});

    const session = new Session({ autoFire: false });

    const r1 = defineRule({
      name: "rule1",
      salience: 0,
      what: [{ id: null, attr: "X", binding: v("x") }],
      handler: "noop",
      registry,
    });
    const r2 = defineRule({
      name: "rule2",
      salience: 10,
      what: [{ id: null, attr: "Y", binding: v("y") }],
      handler: "noop",
      registry,
    });
    session.add(r1);
    session.add(r2);

    const orderable = session._getOrderableRules();
    expect(orderable).toHaveLength(2);
    expect(orderable[0]?.name).toBe("rule1");
    expect(orderable[0]?.salience).toBe(0);
    expect(orderable[0]?.addedAt).toBe(0);
    expect(orderable[1]?.name).toBe("rule2");
    expect(orderable[1]?.salience).toBe(10);
    expect(orderable[1]?.addedAt).toBe(1);
  });
});