// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.

/**
 * Extensions to the
 * {@link https://developer.mozilla.org/en-US/docs/Web/API/Web_Crypto_API | Web Crypto API}
 * supporting additional encryption APIs, but also delegating to the built-in
 * APIs when possible.
 *
 * Provides additional digest algorithms that are not part of the WebCrypto
 * standard as well as a `subtle.digest` and `subtle.digestSync` methods.
 *
 * The {@linkcode KeyStack} export implements the {@linkcode KeyRing} interface
 * for managing rotatable keys for signing data to prevent tampering, like with
 * HTTP cookies.
 *
 * ## Supported algorithms
 *
 * Here is a list of supported algorithms. If the algorithm name in WebCrypto
 * and Wasm/Rust is the same, this library prefers to use the implementation
 * provided by WebCrypto.
 *
 * Length-adjustable algorithms support the
 * {@linkcode DigestAlgorithmObject.length} option.
 *
 * WebCrypto:
 * - `SHA-384`
 * - `SHA-256` (length-extendable)
 * - `SHA-512` (length-extendable)
 *
 * Wasm/Rust:
 * - `BLAKE2B`
 * - `BLAKE2B-128`
 * - `BLAKE2B-160`
 * - `BLAKE2B-224`
 * - `BLAKE2B-256`
 * - `BLAKE2B-384`
 * - `BLAKE2S`
 * - `BLAKE3` (length-adjustable)
 * - `KECCAK-224`
 * - `KECCAK-256`
 * - `KECCAK-384`
 * - `KECCAK-512`
 * - `SHA-384`
 * - `SHA3-224`
 * - `SHA3-256`
 * - `SHA3-384`
 * - `SHA3-512`
 * - `SHAKE128` (length-adjustable)
 * - `SHAKE256` (length-adjustable)
 * - `TIGER`
 * - `RIPEMD-160` (length-extendable)
 * - `SHA-224` (length-extendable)
 * - `SHA-256` (length-extendable)
 * - `SHA-512` (length-extendable)
 * - `MD4` (length-extendable and collidable)
 * - `MD5` (length-extendable and collidable)
 * - `SHA-1` (length-extendable and collidable)
 * - `FNV32` (non-cryptographic)
 * - `FNV32A` (non-cryptographic)
 * - `FNV64` (non-cryptographic)
 * - `FNV64A` (non-cryptographic)
 *
 * @example
 * ```ts
 * import { crypto } from "@std/crypto";
 *
 * // This will delegate to the runtime's WebCrypto implementation.
 * console.log(
 *   new Uint8Array(
 *     await crypto.subtle.digest(
 *       "SHA-384",
 *       new TextEncoder().encode("hello world"),
 *     ),
 *   ),
 * );
 *
 * // This will use a bundled Wasm/Rust implementation.
 * console.log(
 *   new Uint8Array(
 *     await crypto.subtle.digest(
 *       "BLAKE3",
 *       new TextEncoder().encode("hello world"),
 *     ),
 *   ),
 * );
 * ```
 *
 * @example Convert hash to a string
 *
 * ```ts
 * import {
 *   crypto,
 * } from "@std/crypto";
 * import { encodeHex } from "@std/encoding/hex"
 * import { encodeBase64 } from "@std/encoding/base64"
 *
 * const hash = await crypto.subtle.digest(
 *   "SHA-384",
 *   new TextEncoder().encode("You hear that Mr. Anderson?"),
 * );
 *
 * // Hex encoding
 * console.log(encodeHex(hash));
 *
 * // Or with base64 encoding
 * console.log(encodeBase64(hash));
 * ```
 *
 * @module
 */
import {
  DIGEST_ALGORITHM_NAMES,
  type DigestAlgorithmName,
  instantiateWasm,
} from "./_wasm/mod.ts";

export { DIGEST_ALGORITHM_NAMES, type DigestAlgorithmName };

/** Digest algorithms supported by WebCrypto. */
const WEB_CRYPTO_DIGEST_ALGORITHM_NAMES = [
  "SHA-384",
  "SHA-256",
  "SHA-512",
  // insecure (length-extendable and collidable):
  "SHA-1",
] as const;

/**
 * A copy of the global WebCrypto interface, with methods bound so they're
 * safe to re-export.
 */
const webCrypto = ((crypto) => ({
  getRandomValues: crypto.getRandomValues?.bind(crypto),
  randomUUID: crypto.randomUUID?.bind(crypto),
  subtle: {
    decrypt: crypto.subtle?.decrypt?.bind(crypto.subtle),
    deriveBits: crypto.subtle?.deriveBits?.bind(crypto.subtle),
    deriveKey: crypto.subtle?.deriveKey?.bind(crypto.subtle),
    digest: crypto.subtle?.digest?.bind(crypto.subtle),
    encrypt: crypto.subtle?.encrypt?.bind(crypto.subtle),
    exportKey: crypto.subtle?.exportKey?.bind(crypto.subtle),
    generateKey: crypto.subtle?.generateKey?.bind(crypto.subtle),
    importKey: crypto.subtle?.importKey?.bind(crypto.subtle),
    sign: crypto.subtle?.sign?.bind(crypto.subtle),
    unwrapKey: crypto.subtle?.unwrapKey?.bind(crypto.subtle),
    verify: crypto.subtle?.verify?.bind(crypto.subtle),
    wrapKey: crypto.subtle?.wrapKey?.bind(crypto.subtle),
  },
}))(globalThis.crypto);

function toUint8Array(data: unknown): Uint8Array | undefined {
  if (data instanceof Uint8Array) {
    return data;
  } else if (ArrayBuffer.isView(data)) {
    return new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
  } else if (data instanceof ArrayBuffer) {
    return new Uint8Array(data);
  }
  return undefined;
}

/** Extensions to the web standard `SubtleCrypto` interface. */
export interface StdSubtleCrypto extends SubtleCrypto {
  /**
   * Returns a new `Promise` object that will digest `data` using the specified
   * `AlgorithmIdentifier`.
   */
  digest(
    algorithm: DigestAlgorithm,
    data: BufferSource | AsyncIterable<BufferSource> | Iterable<BufferSource>,
  ): Promise<ArrayBuffer>;

  /**
   * Returns a ArrayBuffer with the result of digesting `data` using the
   * specified `AlgorithmIdentifier`.
   */
  digestSync(
    algorithm: DigestAlgorithm,
    data: BufferSource | Iterable<BufferSource>,
  ): ArrayBuffer;
}

/** Extensions to the Web {@linkcode Crypto} interface. */
export interface StdCrypto extends Crypto {
  /** Extension to the {@linkcode crypto.SubtleCrypto} interface. */
  readonly subtle: StdSubtleCrypto;
}

/**
 * An wrapper for WebCrypto adding support for additional non-standard
 * algorithms, but delegating to the runtime WebCrypto implementation whenever
 * possible.
 */
const stdCrypto: StdCrypto = ((x) => x)({
  ...webCrypto,
  subtle: {
    ...webCrypto.subtle,

    /**
     * Polyfills stream support until the Web Crypto API does so:
     * @see {@link https://github.com/wintercg/proposal-webcrypto-streams}
     */
    async digest(
      algorithm: DigestAlgorithm,
      data: BufferSource | AsyncIterable<BufferSource> | Iterable<BufferSource>,
    ): Promise<ArrayBuffer> {
      const { name, length } = normalizeAlgorithm(algorithm);

      assertValidDigestLength(length);

      // We delegate to WebCrypto whenever possible,
      if (
        // if the algorithm is supported by the WebCrypto standard,
        (WEB_CRYPTO_DIGEST_ALGORITHM_NAMES as readonly string[]).includes(
          name,
        ) &&
        // and the data is a single buffer,
        isBufferSource(data)
      ) {
        return await webCrypto.subtle.digest(algorithm, data);
      } else if (DIGEST_ALGORITHM_NAMES.includes(name as DigestAlgorithmName)) {
        if (isBufferSource(data)) {
          // Otherwise, we use our bundled Wasm implementation via digestSync
          // if it supports the algorithm.
          return stdCrypto.subtle.digestSync(algorithm, data);
        } else if (isIterable(data)) {
          return stdCrypto.subtle.digestSync(
            algorithm,
            data as Iterable<BufferSource>,
          );
        } else if (isAsyncIterable(data)) {
          const wasmCrypto = instantiateWasm();
          const context = new wasmCrypto.DigestContext(name);
          for await (const chunk of data as AsyncIterable<BufferSource>) {
            const chunkBytes = toUint8Array(chunk);
            if (!chunkBytes) {
              throw new TypeError(
                "Cannot digest the data: A chunk is not ArrayBuffer nor ArrayBufferView",
              );
            }
            context.update(chunkBytes);
          }
          return context.digestAndDrop(length).buffer;
        } else {
          throw new TypeError(
            "data must be a BufferSource or [Async]Iterable<BufferSource>",
          );
        }
      }
      // (TypeScript type definitions prohibit this case.) If they're trying
      // to call an algorithm we don't recognize, pass it along to WebCrypto
      // in case it's a non-standard algorithm supported by the the runtime
      // they're using.
      return await webCrypto.subtle.digest(algorithm, data as BufferSource);
    },

    digestSync(
      algorithm: DigestAlgorithm,
      data: BufferSource | Iterable<BufferSource>,
    ): ArrayBuffer {
      const { name, length } = normalizeAlgorithm(algorithm);
      assertValidDigestLength(length);

      const wasmCrypto = instantiateWasm();
      if (isBufferSource(data)) {
        const bytes = toUint8Array(data)!;
        return wasmCrypto.digest(name, bytes, length).buffer;
      }
      if (isIterable(data)) {
        const context = new wasmCrypto.DigestContext(name);
        for (const chunk of data) {
          const chunkBytes = toUint8Array(chunk);
          if (!chunkBytes) {
            throw new TypeError(
              "Cannot digest the data: A chunk is not ArrayBuffer nor ArrayBufferView",
            );
          }
          context.update(chunkBytes);
        }
        return context.digestAndDrop(length).buffer;
      }
      throw new TypeError(
        "data must be a BufferSource or Iterable<BufferSource>",
      );
    },
  },
});

/*
 * The largest digest length the current Wasm implementation can support. This
 * is the value of `isize::MAX` on 32-bit platforms like Wasm, which is the
 * maximum allowed capacity of a Rust `Vec<u8>`.
 */
const MAX_DIGEST_LENGTH = 0x7FFF_FFFF;

/**
 * Asserts that a number is a valid length for a digest, which must be an
 * integer that fits in a Rust `Vec<u8>`, or be undefined.
 */
function assertValidDigestLength(value?: number) {
  if (
    value !== undefined &&
    (value < 0 || value > MAX_DIGEST_LENGTH ||
      !Number.isInteger(value))
  ) {
    throw new RangeError(
      `length must be an integer between 0 and ${MAX_DIGEST_LENGTH}, inclusive`,
    );
  }
}

/** Extended digest algorithm objects. */
export type DigestAlgorithmObject = {
  name: DigestAlgorithmName;
  length?: number;
};

/**
 * Extended digest algorithms accepted by {@linkcode stdCrypto.subtle.digest}.
 *
 * The `length` option will be ignored for
 * {@link https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/digest#algorithm | Web Standard algorithms}.
 */
export type DigestAlgorithm = DigestAlgorithmName | DigestAlgorithmObject;

function normalizeAlgorithm(algorithm: DigestAlgorithm) {
  return ((typeof algorithm === "string")
    ? { name: algorithm.toUpperCase() }
    : {
      ...algorithm,
      name: algorithm.name.toUpperCase(),
    }) as DigestAlgorithmObject;
}

function isBufferSource(obj: unknown): obj is BufferSource {
  return obj instanceof ArrayBuffer || ArrayBuffer.isView(obj);
}

function isIterable<T>(obj: unknown): obj is Iterable<T> {
  return typeof (obj as Iterable<T>)[Symbol.iterator] === "function";
}

function isAsyncIterable<T>(obj: unknown): obj is AsyncIterable<T> {
  return typeof (obj as AsyncIterable<T>)[Symbol.asyncIterator] === "function";
}

export { stdCrypto as crypto };
