import { describe, expect, it } from "vitest";
import {
  attachments,
  decodeHeaderValue,
  parseHeaders,
  parseMessage,
  walkParts,
} from "../../src/core/mime";

const MULTIPART = `From: =?UTF-8?Q?Ada_=E2=9C=93?= <ada@example.test>\r
Subject: folded\r
 value\r
MIME-Version: 1.0\r
Content-Type: multipart/mixed; boundary="b"\r
\r
--b\r
Content-Type: text/plain; charset=utf-8\r
Content-Transfer-Encoding: quoted-printable\r
\r
hello=20world\r
--b\r
Content-Type: application/octet-stream\r
Content-Disposition: attachment; filename*=UTF-8''report%20one.txt\r
Content-Transfer-Encoding: base64\r
\r
YWJj\r
--b--`;

describe("MIME parser", () => {
  it("unfolds fields and decodes RFC 2047 words", () => {
    const headers = parseHeaders(
      "Subject: =?UTF-8?Q?Hello_=E2=9C=93?=\r\n\tworld",
    );
    expect(headers[0]?.value).toBe("Hello ✓ world");
    expect(decodeHeaderValue("=?ISO-8859-1?Q?Andr=E9?=")).toBe("André");
    expect(decodeHeaderValue("=?UTF-8?Q?joined?=   =?UTF-8?Q?_words?=")).toBe(
      "joined words",
    );
  });

  it("builds nested parts and decodes transfer encodings", () => {
    const parsed = parseMessage(MULTIPART);
    expect(walkParts(parsed.root).map((part) => part.mediaType)).toEqual([
      "multipart/mixed",
      "text/plain",
      "application/octet-stream",
    ]);
    expect(parsed.root.children[0]?.text).toBe("hello world");
    expect([...parsed.root.children[1]!.bytes]).toEqual([97, 98, 99]);
    expect(attachments(parsed.root)[0]).toMatchObject({
      filename: "report one.txt",
      size: 3,
    });
  });

  it("preserves arbitrary source octets and exact multipart byte ranges", () => {
    const prefix = new TextEncoder().encode(
      "From: a@example.test\r\nContent-Type: multipart/mixed; boundary=x\r\n\r\n--x\r\nContent-Type: application/octet-stream\r\n\r\n",
    );
    const suffix = new TextEncoder().encode("\r\n--x--\r\n");
    const bytes = new Uint8Array(prefix.length + 4 + suffix.length);
    bytes.set(prefix);
    bytes.set([0x80, 0x81, 0xfe, 0xff], prefix.length);
    bytes.set(suffix, prefix.length + 4);
    const parsed = parseMessage(bytes);
    expect([...parsed.root.children[0]!.bytes]).toEqual([
      0x80, 0x81, 0xfe, 0xff,
    ]);
    expect([...parsed.rawBytes]).toEqual([...bytes]);
    const range = parsed.root.children[0]!.sourceRange!;
    expect([...parsed.rawBytes.slice(range.bodyStart, range.end)]).toEqual([
      0x80, 0x81, 0xfe, 0xff,
    ]);
  });

  it("assembles RFC 2231 parameter continuations", () => {
    const parsed = parseMessage(
      "From: a@example.test\r\nContent-Type: application/octet-stream\r\nContent-Disposition: attachment; filename*0*=UTF-8''long%20; filename*1*=name%E2%9C%93.bin\r\n\r\ndata",
    );
    expect(attachments(parsed.root)[0]?.filename).toBe("long name✓.bin");
  });

  it("parses nested message/rfc822 entities", () => {
    const parsed = parseMessage(
      "From: a@example.test\nContent-Type: message/rfc822\n\nFrom: b@example.test\nContent-Type: text/plain\n\nnested",
    );
    expect(parsed.root.children[0]?.text).toBe("nested");
  });

  it("decodes and exposes transferred message attachments", () => {
    const nested = btoa(
      "From: b@example.test\r\nContent-Type: text/plain\r\n\r\nnested",
    );
    const parsed = parseMessage(
      `From: a@example.test\nContent-Type: message/rfc822; name="forwarded.eml"\nContent-Disposition: attachment; filename="forwarded.eml"\nContent-Transfer-Encoding: base64\n\n${nested}`,
    );
    expect(parsed.root.children[0]?.text).toBe("nested");
    expect(attachments(parsed.root)[0]).toMatchObject({
      filename: "forwarded.eml",
    });
    expect(attachments(parsed.root)[0]?.size).toBeGreaterThan(0);
  });

  it("fails closed for malformed and excessive structures", () => {
    expect(() => parseMessage("Bad header\n\nbody")).toThrow(
      /malformed header/iu,
    );
    expect(() =>
      parseMessage("Content-Type: multipart/mixed; boundary=x\n\nnone"),
    ).toThrow(/boundary/iu);
    expect(() =>
      parseMessage("From: a@example.test\n\n12345", {
        maxChars: 4,
        maxHeaders: 2,
        maxParts: 2,
        maxDepth: 2,
        maxDecodedBytes: 8,
      }),
    ).toThrow(/limit/iu);
  });
});