/**
 * KHAELOR
 * File: tests/context/budget.test.ts
 * Description: ContextBudget tests — real-usage accounting, thresholds, config-driven windows.
 *
 * Author: Simon-Pierre Boucher
 * Contact: contact@spboucher.ai
 */

import { describe, expect, it } from "vitest";
import {
  ContextBudget,
  DEFAULT_CONTEXT_WINDOW,
  resolveContextWindow,
} from "../../src/context/index.js";

describe("resolveContextWindow", () => {
  it("falls back to the default window when nothing is configured", () => {
    expect(resolveContextWindow("any-model")).toBe(DEFAULT_CONTEXT_WINDOW);
  });

  it("uses a configured default window", () => {
    expect(resolveContextWindow("any-model", { defaultWindow: 500_000 })).toBe(500_000);
  });

  it("prefers an exact per-model override from config", () => {
    const config = { defaultWindow: 200_000, byModel: { "big-model": 1_000_000 } };
    expect(resolveContextWindow("big-model", config)).toBe(1_000_000);
    expect(resolveContextWindow("other-model", config)).toBe(200_000);
  });

  it("ignores invalid overrides", () => {
    expect(resolveContextWindow("m", { byModel: { m: -5 }, defaultWindow: 0 })).toBe(
      DEFAULT_CONTEXT_WINDOW,
    );
  });
});

describe("ContextBudget", () => {
  const budget = () =>
    new ContextBudget({
      model: "m",
      reservedOutputTokens: 1_000,
      contextWindow: { defaultWindow: 10_000 },
      compactionBufferTokens: 1_000,
      pruneThresholdRatio: 0.5,
    });

  it("computes usableWindow = window − reservedOutput − compactionBuffer", () => {
    expect(budget().usableWindow).toBe(8_000);
  });

  it("starts with no observed usage and zero pressure", () => {
    const b = budget();
    expect(b.hasObservedUsage).toBe(false);
    expect(b.lastTotalTokens).toBe(0);
    expect(b.pressure()).toBe(0);
    expect(b.level()).toBe("ok");
  });

  it("records real usage including cache reads and writes", () => {
    const b = budget();
    b.onUsage({ inputTokens: 1_000, outputTokens: 500, cacheReadTokens: 6_000, cacheWriteTokens: 1_000 });
    expect(b.lastTotalTokens).toBe(8_500);
    expect(b.hasObservedUsage).toBe(true);
  });

  it("levels: ok → prune → compact as fake usage crosses thresholds", () => {
    const b = budget();
    b.onUsage({ inputTokens: 3_000, outputTokens: 0, cacheReadTokens: 0, cacheWriteTokens: 0 });
    expect(b.level()).toBe("ok");
    expect(b.shouldCompact()).toBe(false);

    b.onUsage({ inputTokens: 4_500, outputTokens: 0, cacheReadTokens: 0, cacheWriteTokens: 0 });
    expect(b.level()).toBe("prune"); // ≥ 50% of 8000
    expect(b.shouldCompact()).toBe(false);

    b.onUsage({ inputTokens: 8_000, outputTokens: 100, cacheReadTokens: 0, cacheWriteTokens: 0 });
    expect(b.level()).toBe("compact");
    expect(b.shouldCompact()).toBe(true);
    expect(b.pressure()).toBeGreaterThanOrEqual(1);
  });

  it("tracks only the LAST turn's usage (context footprint, not a running sum)", () => {
    const b = budget();
    b.onUsage({ inputTokens: 7_900, outputTokens: 200, cacheReadTokens: 0, cacheWriteTokens: 0 });
    expect(b.level()).toBe("compact");
    b.onUsage({ inputTokens: 100, outputTokens: 10, cacheReadTokens: 0, cacheWriteTokens: 0 });
    expect(b.level()).toBe("ok");
  });
});