// PCH-02-008 regression tests — BinaryReader must bound every read and fail
// with the decoder's existing PAYLOAD_TOO_SHORT code on truncated input.

import { describe, expect, it } from "vitest";
import { BinaryReader } from "./peachPayload";

describe("PCH-02-008 — BinaryReader bounds checks", () => {
  it("u8 past end of buffer throws PAYLOAD_TOO_SHORT", () => {
    const r = new BinaryReader(Uint8Array.of(0xaa), 0);
    expect(r.u8()).toBe(0xaa);
    expect(() => r.u8()).toThrow("PAYLOAD_TOO_SHORT");
  });

  it("u16 with only one byte remaining throws PAYLOAD_TOO_SHORT", () => {
    const r = new BinaryReader(Uint8Array.of(0x01), 0);
    expect(() => r.u16()).toThrow("PAYLOAD_TOO_SHORT");
  });

  it("u32 with three bytes remaining throws PAYLOAD_TOO_SHORT", () => {
    const r = new BinaryReader(Uint8Array.of(0x01, 0x02, 0x03), 0);
    expect(() => r.u32()).toThrow("PAYLOAD_TOO_SHORT");
  });

  it("read(n) past end throws instead of clamping short", () => {
    const r = new BinaryReader(Uint8Array.of(1, 2, 3, 4), 0);
    expect(() => r.read(5)).toThrow("PAYLOAD_TOO_SHORT");
  });

  it("lpString whose declared length overruns the buffer throws", () => {
    const r = new BinaryReader(Uint8Array.of(200, 0x61, 0x62), 0);
    expect(() => r.lpString(1)).toThrow("PAYLOAD_TOO_SHORT");
  });

  it("valid reads at exact buffer boundaries still work (regression)", () => {
    const buf = new Uint8Array(11);
    const view = new DataView(buf.buffer);
    buf[0] = 0x7f;
    view.setUint16(1, 0xbeef, true);
    view.setUint32(3, 0xdeadbeef, true);
    buf.set([0x70, 0x65, 0x61, 0x63], 7);

    const r = new BinaryReader(buf, 0);
    expect(r.u8()).toBe(0x7f);
    expect(r.u16()).toBe(0xbeef);
    expect(r.u32()).toBe(0xdeadbeef);
    expect(Array.from(r.read(4))).toEqual([0x70, 0x65, 0x61, 0x63]);
    expect(() => r.u8()).toThrow("PAYLOAD_TOO_SHORT");
  });

  it("lpString round-trips a valid length-prefixed string (regression)", () => {
    const text = new TextEncoder().encode("peach");
    const buf = new Uint8Array(1 + text.length);
    buf[0] = text.length;
    buf.set(text, 1);

    const r = new BinaryReader(buf, 0);
    expect(r.lpString(1)).toBe("peach");
    expect(r.cursor).toBe(buf.length);
  });

  it("respects a non-zero start offset and bounds from it", () => {
    const buf = Uint8Array.of(0xff, 0xff, 0x2a);
    const r = new BinaryReader(buf, 2);
    expect(r.u8()).toBe(0x2a);
    expect(() => r.u8()).toThrow("PAYLOAD_TOO_SHORT");
  });
});