import { describe, expect, it } from "vite-plus/test";

import {
  decideThreadResume,
  threadReplayEncodedBytes,
  THREAD_RESUME_MAX_REPLAY_ENCODED_BYTES,
  THREAD_RESUME_MAX_REPLAY_EVENTS,
} from "./ThreadStream.ts";

describe("decideThreadResume", () => {
  it("replays when the gap is zero", () => {
    expect(
      decideThreadResume({
        afterSequence: 10,
        highWater: 10,
        replayEventCount: 0,
        replayEncodedBytes: 0,
      }),
    ).toEqual({ mode: "replay", afterSequence: 10, throughSequence: 10 });
  });

  it("replays when the event count is within the bound", () => {
    expect(
      decideThreadResume({
        afterSequence: 10,
        highWater: 20_000,
        replayEventCount: THREAD_RESUME_MAX_REPLAY_EVENTS,
        replayEncodedBytes: THREAD_RESUME_MAX_REPLAY_ENCODED_BYTES,
      }),
    ).toEqual({
      mode: "replay",
      afterSequence: 10,
      throughSequence: 20_000,
    });
  });

  it("falls back to a snapshot when the event count exceeds the bound", () => {
    expect(
      decideThreadResume({
        afterSequence: 10,
        highWater: 20_000,
        replayEventCount: THREAD_RESUME_MAX_REPLAY_EVENTS + 1,
        replayEncodedBytes: 1,
      }),
    ).toEqual({ mode: "snapshot" });
  });

  it("falls back to a snapshot when encoded replay bytes exceed the bound", () => {
    expect(
      decideThreadResume({
        afterSequence: 10,
        highWater: 11,
        replayEventCount: 1,
        replayEncodedBytes: THREAD_RESUME_MAX_REPLAY_ENCODED_BYTES + 1,
      }),
    ).toEqual({ mode: "snapshot" });
  });

  it("falls back to a snapshot when the client cursor is ahead of the store", () => {
    expect(
      decideThreadResume({
        afterSequence: 50,
        highWater: 40,
        replayEventCount: 0,
        replayEncodedBytes: 0,
      }),
    ).toEqual({ mode: "snapshot" });
  });

  it("counts UTF-8 bytes across projected stream items", () => {
    expect(threadReplayEncodedBytes([{ value: "a" }, { value: "🦊" }])).toBe(
      Buffer.byteLength('{"value":"a"}', "utf8") + Buffer.byteLength('{"value":"🦊"}', "utf8"),
    );
  });
});