import { describe, it, expect } from "vitest";
import { execSync } from "node:child_process";
import { readFileSync } from "node:fs";
import { mkdtemp, readFile, writeFile } from "node:fs/promises";
import { tmpdir } from "node:os";
import { join, resolve } from "node:path";
import {
  compressAttachment,
  compressFile,
  compressBuffer,
  compressPdf,
  compressImage,
  shouldCompress,
  __test,
} from "./attachment-compressor";

// Real PB-derived PDF fixtures (copies of operator quote PDFs on
// disk — full corpus sees ~85% reduction with `gs /ebook`). Kept
// in the repo as docs/ so the test stays self-contained without
// needing network or PB access.
const REAL_PDF_PATH = resolve(
  __dirname,
  "../../../docs/example-quotes/sample-cnl.pdf",
);
const SMALL_PDF_PATH = resolve(
  __dirname,
  "../../../docs/example-quotes/live-charmaine-cnl.pdf",
);

// Synchronous binary detection — `describe.skipIf` runs at file
// load time, so we can't use the async `beforeAll` for that
// decision. `execSync` with `stdio: "ignore"` + a tiny exit-code
// capture gives us "is it on PATH?" in one round trip. A missing
// binary throws ENOENT, which we convert to false.
function binAvailable(cmd: string): boolean {
  try {
    execSync(`${cmd} --version`, { stdio: "ignore" });
    return true;
  } catch {
    return false;
  }
}
const HAS_GS = binAvailable("gs");
const HAS_SIPS = binAvailable("sips");

// ── Pure routing logic (no binaries) ───────────────────────────

describe("shouldCompress", () => {
  it("returns kind:'pdf' for .pdf filenames", () => {
    expect(shouldCompress("invoice.pdf", 100 * 1024)).toEqual({
      kind: "pdf",
      reason: null,
    });
  });

  it("returns kind:'image' for JPG/PNG filenames", () => {
    expect(shouldCompress("photo.jpg", 200 * 1024).kind).toBe("image");
    expect(shouldCompress("photo.jpeg", 200 * 1024).kind).toBe("image");
    expect(shouldCompress("photo.png", 200 * 1024).kind).toBe("image");
  });

  it("is case-insensitive on the extension (PB filenames can be)", () => {
    expect(shouldCompress("Invoice.PDF", 100 * 1024).kind).toBe("pdf");
    expect(shouldCompress("Photo.JPG", 200 * 1024).kind).toBe("image");
  });

  it("flags unsupported extensions (.docx, .txt, .csv, etc.)", () => {
    for (const ext of ["docx", "txt", "csv", "zip", "xlsx", "html"]) {
      expect(shouldCompress(`file.${ext}`, 200 * 1024)).toEqual({
        kind: null,
        reason: "unsupported_type",
      });
    }
  });

  it("flags filenames with no extension as unsupported", () => {
    expect(shouldCompress("noextension", 200 * 1024)).toEqual({
      kind: null,
      reason: "unsupported_type",
    });
  });

  it("flags PDFs under SKIP_MIN_BYTES as already_small", () => {
    expect(shouldCompress("tiny.pdf", 1024)).toEqual({
      kind: null,
      reason: "already_small",
    });
    expect(shouldCompress("tiny.jpg", 1024).reason).toBe("already_small");
    // Boundary: exactly 50 KB (50 * 1024) should NOT be already_small —
    // the strict `<` check means 50 KB is processed. Verified by
    // guarding the math here so future tuning doesn't drift silently.
    expect(shouldCompress("edge.pdf", 50 * 1024).reason).toBeNull();
    expect(shouldCompress("edge-minus-one.pdf", 50 * 1024 - 1).reason).toBe(
      "already_small",
    );
  });

  it("flags files above SKIP_MAX_BYTES (PB hard cap is 25 MB) as too_large", () => {
    expect(shouldCompress("huge.pdf", 25 * 1024 * 1024).reason).toBe("too_large");
    expect(shouldCompress("huge.pdf", 24 * 1024 * 1024).reason).toBeNull();
    expect(shouldCompress("huge.pdf", 24 * 1024 * 1024 + 1).reason).toBe("too_large");
  });

  it("size bounds are checked before extension (cheap check first)", () => {
    // 1 KB .docx — would normally fail on extension, but a tiny
    // .docx is `already_small` first. Confirms ordering matches the
    // implementation (`compressAttachment` checks size before
    // extension).
    expect(shouldCompress("doc.docx", 1024).reason).toBe("already_small");
  });
});

// ── Tunable bounds are exported for ops sanity-checking ────────

describe("__test internal constants", () => {
  it("SKIP_MIN_BYTES matches the bulk-pass script's filter", () => {
    // scripts/compress-attachments-once.mjs uses:
    //   const SKIP_MIN_BYTES = 50 * 1024;
    //   const SKIP_MAX_BYTES = 24 * 1024 * 1024;
    // Drift between the two would let the on-upload hook and the
    // bulk-pass script disagree on which files to touch.
    expect(__test.SKIP_MIN_BYTES).toBe(50 * 1024);
    expect(__test.SKIP_MAX_BYTES).toBe(24 * 1024 * 1024);
  });
});

// ── compressAttachment: shape contract (no binaries) ───────────

describe("compressAttachment — shape contract", () => {
  it("throws on non-Buffer input (programmer error, not data error)", async () => {
    await expect(
      compressAttachment({
        buffer: "not-a-buffer" as unknown as Buffer,
        filename: "x.pdf",
      }),
    ).rejects.toThrow(/buffer must be a Buffer/);
  });

  it("throws on missing filename", async () => {
    await expect(
      compressAttachment({ buffer: Buffer.from("%PDF-1.3"), filename: "" }),
    ).rejects.toThrow(/filename is required/);
  });

  it("returns the original buffer with reason:already_small for tiny files", async () => {
    const tiny = Buffer.from("%PDF-1.3\n%EOF\n");
    const result = await compressAttachment({ buffer: tiny, filename: "tiny.pdf" });
    expect(result.skipped).toBe(true);
    expect(result.reason).toBe("already_small");
    expect(result.originalBytes).toBe(tiny.byteLength);
    expect(result.compressedBytes).toBe(tiny.byteLength);
    expect(result.buffer).toBe(tiny); // identity check — same object, no copy
    expect(result.mimeType).toBe("application/pdf");
  });

  it("returns the original buffer with reason:unsupported_type for non-image/PDF", async () => {
    const buf = Buffer.alloc(100 * 1024, "x"); // 100 KB of 'x'
    const result = await compressAttachment({
      buffer: buf,
      filename: "spreadsheet.xlsx",
    });
    expect(result.skipped).toBe(true);
    expect(result.reason).toBe("unsupported_type");
    expect(result.buffer).toBe(buf);
    // mimeType is left as octet-stream when unrecognised
    expect(result.mimeType).toBe("application/octet-stream");
  });
});

// ── compressAttachment — real-binary tests (skip if no gs/sips) ─

describe.skipIf(!HAS_GS)("compressAttachment — PDF (real Ghostscript)", () => {
  it("compresses a real quote PDF measurably smaller", async () => {
    const original = readFileSync(REAL_PDF_PATH);
    expect(original.byteLength).toBeGreaterThan(50 * 1024); // sanity: ≥50 KB

    const result = await compressAttachment({
      buffer: original,
      filename: "sample-cnl.pdf",
    });

    expect(result.reason).toBe("compressed");
    expect(result.skipped).toBe(false);
    expect(result.compressedBytes).toBeLessThan(original.byteLength);
    // Confirm the magnitude: the dry-run measured ~85% reduction on
    // the corpus. We assert a soft floor (>40% reduction) so the
    // test stays meaningful across preset / Ghostscript version
    // changes without being fragile on the upper bound.
    const ratio = result.compressedBytes / result.originalBytes;
    expect(ratio).toBeLessThan(0.6);
    // Output must still be a valid PDF magic header.
    expect(result.buffer.slice(0, 5).toString("ascii")).toBe("%PDF-");
  }, 30_000);

  it("contract: returned buffer's byteLength matches compressedBytes regardless of reason", async () => {
    // Drive the same data through three calls that take different
    // paths through the code, then assert that for each call
    //   result.buffer.byteLength === result.compressedBytes
    // holds even when the skip guard fires. (Earlier revisions of
    // `no_meaningful_savings` had a 1-byte contract leak that this
    // test pins down.)
    const original = readFileSync(REAL_PDF_PATH);
    const firstPass = await compressAttachment({
      buffer: original,
      filename: "sample-cnl.pdf",
    });
    expect(firstPass.buffer.byteLength).toBe(firstPass.compressedBytes);

    // Run the first pass output through again. Expect either
    //   - reason:"compressed"            (rare — gs found more to drop)
    //   - reason:"no_meaningful_savings" (typical — gs was already optimal)
    const secondPass = await compressAttachment({
      buffer: firstPass.buffer,
      filename: "sample-cnl.pdf",
    });
    expect(["compressed", "no_meaningful_savings"]).toContain(secondPass.reason);
    expect(secondPass.buffer.byteLength).toBe(secondPass.compressedBytes);

    // The second pass must NEVER make the file larger — if it did
    // the no-savings guard didn't fire and we'd silently bump PB
    // URLs for no reason on every duplicate pass.
    expect(secondPass.compressedBytes).toBeLessThanOrEqual(
      firstPass.compressedBytes,
    );
  }, 60_000);

  it("returns the original with reason:already_small for a <50 KB PDF", async () => {
    // The "live-charmaine-cnl" fixture is ~22 KB.
    const small = readFileSync(SMALL_PDF_PATH);
    const result = await compressAttachment({
      buffer: small,
      filename: "small.pdf",
    });
    expect(result.reason).toBe("already_small");
    expect(result.buffer).toBe(small);
  });
});

describe("compressAttachment — image (sips not exercised here)", () => {
  // Image compression needs a fixture of sufficient size (>50 KB)
  // for the routing logic to let it through. The repo doesn't ship
  // one without bloating the diff, and sips binary paths vary by
  // platform. The routing-logic tests above prove the image branch
  // is reached; a follow-up can wire an image fixture when one is
  // needed. The compressPdf primitive is tested separately below.
  it("still documents the gap so future fixtures have a hook", () => {
    expect(HAS_SIPS).toBeDefined();
  });
});

// ── Bare-command helpers are exposed for potential mocking ─────

describe("bare helpers re-exported", () => {
  it("exports compressPdf and compressImage as standalone functions", () => {
    expect(typeof compressPdf).toBe("function");
    expect(typeof compressImage).toBe("function");
  });

  it.skipIf(!HAS_GS)("compressPdf primitive actually shrinks a real PDF", async () => {
    const dir = await mkdtemp(join(tmpdir(), "wfdash-compress-test-"));
    const src = join(dir, "in.pdf");
    const dst = join(dir, "out.pdf");
    await writeFile(src, readFileSync(REAL_PDF_PATH));
    const r = await compressPdf(src, dst);
    expect(r.ok).toBe(true);
    const out = await readFile(dst);
    const srcSize = (await readFile(src)).byteLength;
    expect(out.byteLength).toBeLessThan(srcSize);
  }, 30_000);
});

// ── Caller-facing wrappers ──────────────────────────────────────
//
// The wrappers exist so route handlers / services can compress
// without manually converting File/Buffer to the (Buffer, filename,
// mimeType) triple that `compressAttachment` requires. They also
// rebuild a `File` or pass back a `{ buffer, filename }` shaped
// for direct use with `fd.append(field, ...)` /
// `new Blob([...], { type })`.

describe("compressFile — wraps a File for multipart FormData", () => {
  it("preserves a too-small File untouched and rebuilds a File with the same bytes", async () => {
    const original = new File(["%PDF-tiny"], "tiny.pdf", {
      type: "application/pdf",
    });
    const originalBytes = new Uint8Array(await original.arrayBuffer());
    const { file, result } = await compressFile(original);
    expect(result.reason).toBe("already_small");
    expect(result.skipped).toBe(true);
    // The returned File is a new instance — the input is not mutated.
    expect(file).not.toBe(original);
    expect(file.name).toBe("tiny.pdf");
    expect(file.type).toBe("application/pdf");
    // Bytes must match the input exactly — round-tripping through
    // Buffer → File must not lose or transform a single byte.
    const bytes = new Uint8Array(await file.arrayBuffer());
    expect(bytes).toEqual(originalBytes);
    // Sanity: input has its expected shape (guards against File
    // constructor string encoding turning "%PDF-tiny" into something
    // weird).
    expect(originalBytes.byteLength).toBeGreaterThan(0);
    const head = new TextDecoder().decode(originalBytes.slice(0, 5));
    expect(head).toBe("%PDF-");
  });

  it.skipIf(!HAS_GS)(
    "actually shrinks a real PDF and returns a new File with reduced bytes",
    async () => {
      const pdfBytes = readFileSync(REAL_PDF_PATH);
      const original = new File([pdfBytes], "real.pdf", {
        type: "application/pdf",
      });
      const { file, result } = await compressFile(original);
      expect(result.reason).toBe("compressed");
      expect(result.skipped).toBe(false);
      expect(result.compressedBytes).toBeLessThan(result.originalBytes);
      const recompressedBytes = new Uint8Array(await file.arrayBuffer());
      // The new File carries exactly the recompressed bytes —
      // PB will store those (smaller) bytes on disk.
      expect(recompressedBytes.byteLength).toBe(result.compressedBytes);
      // And it preserves the %PDF- header PB / the proxy rely on.
      const head = new TextDecoder().decode(recompressedBytes.slice(0, 5));
      expect(head).toBe("%PDF-");
    },
    30_000,
  );

  it("preserves an unsupported extension untouched", async () => {
    const original = new File(
      [new Uint8Array(100 * 1024)], // 100 KB, well above the 50 KB floor
      "data.zip",
      { type: "application/zip" },
    );
    const { file, result } = await compressFile(original);
    expect(result.reason).toBe("unsupported_type");
    expect(result.skipped).toBe(true);
    expect(file.name).toBe("data.zip");
  });

  it("does not mutate the original File's bytes", async () => {
    const bytes = new Uint8Array(80 * 1024);
    bytes.fill(0xff);
    const original = new File([bytes], "blanks.bin", {
      type: "application/octet-stream",
    });
    const before = new Uint8Array(await original.arrayBuffer());
    await compressFile(original);
    const after = new Uint8Array(await original.arrayBuffer());
    expect(after).toEqual(before);
  });
});

describe("compressBuffer — wraps generated bytes (PDF render path)", () => {
  it("preserves a too-small Buffer untouched", async () => {
    const tiny = Buffer.from("%PDF-small");
    const { buffer, filename, mimeType, result } = await compressBuffer(
      tiny,
      "small.pdf",
      "application/pdf",
    );
    expect(result.reason).toBe("already_small");
    expect(buffer).toBe(tiny); // identity — same Buffer instance
    expect(filename).toBe("small.pdf");
    expect(mimeType).toBe("application/pdf");
  });

  it("accepts a Uint8Array and returns a Buffer", async () => {
    const u8 = new Uint8Array(1024);
    u8.fill(0xab);
    const { buffer } = await compressBuffer(u8, "raw.bin", "application/pdf");
    expect(Buffer.isBuffer(buffer)).toBe(true);
    expect(buffer.byteLength).toBe(1024);
  });

  it.skipIf(!HAS_GS)(
    "actually shrinks a real PDF generated in-memory",
    async () => {
      const pdfBytes = readFileSync(REAL_PDF_PATH);
      const { buffer, filename, mimeType, result } = await compressBuffer(
        pdfBytes,
        "rendered.pdf",
        "application/pdf",
      );
      expect(result.reason).toBe("compressed");
      expect(result.compressedBytes).toBeLessThan(result.originalBytes);
      expect(buffer.byteLength).toBe(result.compressedBytes);
      expect(filename).toBe("rendered.pdf");
      expect(mimeType).toBe("application/pdf");
      // The Buffer is suitable for `new Blob([new Uint8Array(buffer)], { type: mimeType })`
      // without further transformation.
      const blob = new Blob([new Uint8Array(buffer)], { type: mimeType });
      expect(blob.size).toBe(buffer.byteLength);
    },
    30_000,
  );
});