import { describe, it, expect } from "vitest";
import { countTokens, allocateBudget, DEFAULT_BUDGET } from "./tokens.js";

describe("tokens", () => {
  it("countTokens returns 0 for empty input", async () => {
    expect(await countTokens("")).toBe(0);
  });

  it("counts tokens for a known string (approx)", async () => {
    // ~4 chars per token is the rough heuristic; this asserts a sane range.
    const n = await countTokens("The quick brown fox jumps over the lazy dog.");
    expect(n).toBeGreaterThan(0);
    expect(n).toBeLessThan(40);
  });

  it("allocateBudget respects percentages of total", () => {
    const b = allocateBudget(DEFAULT_BUDGET);
    expect(b.total).toBe(200_000);
    // 10% system ≈ 20000, 40% context ≈ 80000, etc. (floor, so allow small slack).
    expect(b.system).toBeCloseTo(20_000, -2);
    expect(b.context).toBeCloseTo(80_000, -2);
    expect(b.history).toBeCloseTo(60_000, -2);
    expect(b.output).toBeCloseTo(40_000, -2);
  });

  it("budget slots sum approximately to total", () => {
    const b = allocateBudget({ system: 25, context: 25, history: 25, output: 25 });
    expect(b.system + b.context + b.history + b.output).toBeGreaterThan(199_990);
    expect(b.total).toBe(200_000);
  });

  it("throws when percentages sum to zero", () => {
    expect(() => allocateBudget({ system: 0, context: 0, history: 0, output: 0 })).toThrow(
      /positive/,
    );
  });
});