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import { assert, test } from "vitest";
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import { encodeOfsDeltaDistance } from "@/worker/git";
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const toHex = (u8: Uint8Array) =>
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  Array.from(u8)
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    .map((b) => b.toString(16).padStart(2, "0"))
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    .join("");
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// Mirror of the decoder in src/worker/git/pack/assembler.ts for verification
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function decodeOfsDeltaDistance(bytes: Uint8Array): number {
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  let p = 0;
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  let b = bytes[p++];
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  let x = b & 0x7f;
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  while (b & 0x80) {
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    b = bytes[p++];
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    x = ((x + 1) << 7) | (b & 0x7f);
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  }
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  return x >>> 0;
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}
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const known: { n: number; hex: string }[] = [
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  { n: 0x01, hex: "01" },
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  { n: 0x7f, hex: "7f" },
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  { n: 0x80, hex: "8000" },
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  { n: 0x81, hex: "8001" },
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  { n: 0x100, hex: "8100" },
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  { n: 0x3fff, hex: "fe7f" },
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  { n: 0x4000, hex: "ff00" },
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  { n: 0x1ffff, hex: "86fe7f" },
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  { n: 0x20000, hex: "86ff00" },
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];
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test("ofs-delta encoder encodes known values to expected bytes", () => {
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  for (const { n, hex } of known) {
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    const enc = encodeOfsDeltaDistance(n);
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    assert.strictEqual(toHex(enc), hex, `encoding mismatch for ${n}`);
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  }
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});
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test("ofs-delta encoder round-trips a range of values", () => {
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  const values = [
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    1, 2, 3, 10, 0x7e, 0x7f, 0x80, 0x81, 0xff, 0x100, 0x1234, 0x3fff, 0x4000, 0x1ffff, 0x20000,
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    0x1fffff, 0x200000,
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  ];
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  for (const n of values) {
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    const enc = encodeOfsDeltaDistance(n);
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    const dec = decodeOfsDeltaDistance(enc);
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    assert.strictEqual(dec, n, `round-trip failed for ${n} (enc=${toHex(enc)})`);
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  }
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});