// 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 algorithms that are
 * supported by WebCrypto.
 *
 * WebCrypto:
 * - `SHA-384`
 * - `SHA-256`
 * - `SHA-512` (length-extendable and collidable)
 *
 * Wasm/Rust:
 * - `BLAKE2B-128`
 * - `BLAKE2B-160`
 * - `BLAKE2B-224`
 * - `BLAKE2B-256`
 * - `BLAKE2B-384`
 * - `BLAKE2B`
 * - `BLAKE2S`
 * - `BLAKE3`
 * - `FNV32` (length-extendable)
 * - `FNV32A` (length-extendable)
 * - `FNV64` (length-extendable)
 * - `FNV64A` (length-extendable)
 * - `KECCAK-224`
 * - `KECCAK-256`
 * - `KECCAK-384`
 * - `KECCAK-512`
 * - `SHA-384`
 * - `SHA3-224`
 * - `SHA3-256`
 * - `SHA3-384`
 * - `SHA3-512`
 * - `SHAKE128`
 * - `SHAKE256`
 * - `TIGER`
 * - `RIPEMD-160` (length-extendable)
 * - `SHA-224` (length-extendable)
 * - `SHA-256` (length-extendable)
 * - `SHA-512` (length-extendable)
 * - `MD4` (collidable and length-extendable)
 * - `MD5` (collidable and length-extendable)
 * - `SHA-1` (collidable and length-extendable)
 * ```
 *
 * @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 {
  DigestAlgorithm as WasmDigestAlgorithm,
  digestAlgorithms as wasmDigestAlgorithms,
  instantiateWasm,
} from "./_wasm/mod.ts";
import { fnv } from "./_fnv/mod.ts";

export { type WasmDigestAlgorithm, wasmDigestAlgorithms };

/**
 * 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);

const bufferSourceBytes = (data: BufferSource | unknown) => {
  let bytes: Uint8Array | undefined;
  if (data instanceof Uint8Array) {
    bytes = data;
  } else if (ArrayBuffer.isView(data)) {
    bytes = new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
  } else if (data instanceof ArrayBuffer) {
    bytes = new Uint8Array(data);
  }
  return bytes;
};

/** 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);

      const bytes = bufferSourceBytes(data);

      if (FNV_ALGORITHMS.includes(name)) {
        return fnv(name, bytes);
      }

      // We delegate to WebCrypto whenever possible,
      if (
        // if the algorithm is supported by the WebCrypto standard,
        (webCryptoDigestAlgorithms as readonly string[]).includes(name) &&
        // and the data is a single buffer,
        bytes
      ) {
        return webCrypto.subtle.digest(algorithm, bytes);
      } else if (wasmDigestAlgorithms.includes(name as WasmDigestAlgorithm)) {
        if (bytes) {
          // Otherwise, we use our bundled Wasm implementation via digestSync
          // if it supports the algorithm.
          return stdCrypto.subtle.digestSync(algorithm, bytes);
        } else if ((data as Iterable<BufferSource>)[Symbol.iterator]) {
          return stdCrypto.subtle.digestSync(
            algorithm,
            data as Iterable<BufferSource>,
          );
        } else if (
          (data as AsyncIterable<BufferSource>)[Symbol.asyncIterator]
        ) {
          const wasmCrypto = instantiateWasm();
          const context = new wasmCrypto.DigestContext(name);
          for await (const chunk of data as AsyncIterable<BufferSource>) {
            const chunkBytes = bufferSourceBytes(chunk);
            if (!chunkBytes) {
              throw new TypeError("data contained chunk of the wrong type");
            }
            context.update(chunkBytes);
          }
          return context.digestAndDrop(length).buffer;
        } else {
          throw new TypeError(
            "data must be a BufferSource or [Async]Iterable<BufferSource>",
          );
        }
      } else if (webCrypto.subtle?.digest) {
        // (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 webCrypto.subtle.digest(
          algorithm,
          (data as unknown) as Uint8Array,
        );
      } else {
        throw new TypeError(`unsupported digest algorithm: ${algorithm}`);
      }
    },

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

      assertValidDigestLength(length);

      const bytes = bufferSourceBytes(data);

      if (FNV_ALGORITHMS.includes(name)) {
        return fnv(name, bytes);
      }

      const wasmCrypto = instantiateWasm();
      if (bytes) {
        return wasmCrypto.digest(name, bytes, length)
          .buffer;
      } else if ((data as Iterable<BufferSource>)[Symbol.iterator]) {
        const context = new wasmCrypto.DigestContext(name);
        for (const chunk of data as Iterable<BufferSource>) {
          const chunkBytes = bufferSourceBytes(chunk);
          if (!chunkBytes) {
            throw new TypeError("data contained chunk of the wrong type");
          }
          context.update(chunkBytes);
        }
        return context.digestAndDrop(length).buffer;
      } else {
        throw new TypeError(
          "data must be a BufferSource or Iterable<BufferSource>",
        );
      }
    },
  },
});

const FNV_ALGORITHMS = ["FNV32", "FNV32A", "FNV64", "FNV64A"];

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

/** FNV (Fowler/Noll/Vo) algorithms names. */
export type FNVAlgorithms = "FNV32" | "FNV32A" | "FNV64" | "FNV64A";

/** Extended digest algorithm names. */
export type DigestAlgorithmName = WasmDigestAlgorithm | FNVAlgorithms;

/*
 * 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}.
 */
export type DigestAlgorithm = DigestAlgorithmName | DigestAlgorithmObject;

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

export { stdCrypto as crypto };