// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
/**
 * Provides the {@linkcode KeyStack} class which implements the
 * {@linkcode KeyRing} interface for managing rotatable keys.
 *
 * @module
 */ import { timingSafeEqual } from "./timing_safe_equal.ts";
import * as base64url from "../encoding/base64url.ts";
const encoder = new TextEncoder();
function importKey(key) {
    if (typeof key === "string") {
        key = encoder.encode(key);
    } else if (Array.isArray(key)) {
        key = new Uint8Array(key);
    }
    return crypto.subtle.importKey("raw", key, {
        name: "HMAC",
        hash: {
            name: "SHA-256"
        }
    }, true, [
        "sign",
        "verify"
    ]);
}
function sign(data, key) {
    if (typeof data === "string") {
        data = encoder.encode(data);
    } else if (Array.isArray(data)) {
        data = Uint8Array.from(data);
    }
    return crypto.subtle.sign("HMAC", key, data);
}
/** Compare two strings, Uint8Arrays, ArrayBuffers, or arrays of numbers in a
 * way that avoids timing based attacks on the comparisons on the values.
 *
 * The function will return `true` if the values match, or `false`, if they
 * do not match.
 *
 * This was inspired by https://github.com/suryagh/tsscmp which provides a
 * timing safe string comparison to avoid timing attacks as described in
 * https://codahale.com/a-lesson-in-timing-attacks/.
 */ async function compare(a, b) {
    const key = new Uint8Array(32);
    globalThis.crypto.getRandomValues(key);
    const cryptoKey = await importKey(key);
    const ah = await sign(a, cryptoKey);
    const bh = await sign(b, cryptoKey);
    return timingSafeEqual(ah, bh);
}
/** A cryptographic key chain which allows signing of data to prevent tampering,
 * but also allows for easy key rotation without needing to re-sign the data.
 *
 * Data is signed as SHA256 HMAC.
 *
 * This was inspired by [keygrip](https://github.com/crypto-utils/keygrip/).
 *
 * ### Example
 *
 * ```ts
 * import { KeyStack } from "https://deno.land/std@$STD_VERSION/crypto/keystack.ts";
 *
 * const keyStack = new KeyStack(["hello", "world"]);
 * const digest = await keyStack.sign("some data");
 *
 * const rotatedStack = new KeyStack(["deno", "says", "hello", "world"]);
 * await rotatedStack.verify("some data", digest); // true
 * ```
 */ export class KeyStack {
    #cryptoKeys = new Map();
    #keys;
    async #toCryptoKey(key) {
        if (!this.#cryptoKeys.has(key)) {
            this.#cryptoKeys.set(key, await importKey(key));
        }
        return this.#cryptoKeys.get(key);
    }
    get length() {
        return this.#keys.length;
    }
    /** A class which accepts an array of keys that are used to sign and verify
   * data and allows easy key rotation without invalidation of previously signed
   * data.
   *
   * @param keys An iterable of keys, of which the index 0 will be used to sign
   *             data, but verification can happen against any key.
   */ constructor(keys){
        const values = Array.isArray(keys) ? keys : [
            ...keys
        ];
        if (!values.length) {
            throw new TypeError("keys must contain at least one value");
        }
        this.#keys = values;
    }
    /** Take `data` and return a SHA256 HMAC digest that uses the current 0 index
   * of the `keys` passed to the constructor.  This digest is in the form of a
   * URL safe base64 encoded string. */ async sign(data) {
        const key = await this.#toCryptoKey(this.#keys[0]);
        return base64url.encode(await sign(data, key));
    }
    /** Given `data` and a `digest`, verify that one of the `keys` provided the
   * constructor was used to generate the `digest`.  Returns `true` if one of
   * the keys was used, otherwise `false`. */ async verify(data, digest) {
        return await this.indexOf(data, digest) > -1;
    }
    /** Given `data` and a `digest`, return the current index of the key in the
   * `keys` passed the constructor that was used to generate the digest.  If no
   * key can be found, the method returns `-1`. */ async indexOf(data, digest) {
        for(let i = 0; i < this.#keys.length; i++){
            const cryptoKey = await this.#toCryptoKey(this.#keys[i]);
            if (await compare(digest, base64url.encode(await sign(data, cryptoKey)))) {
                return i;
            }
        }
        return -1;
    }
    [Symbol.for("Deno.customInspect")](inspect) {
        const { length  } = this;
        return `${this.constructor.name} ${inspect({
            length
        })}`;
    }
    [Symbol.for("nodejs.util.inspect.custom")](depth, // deno-lint-ignore no-explicit-any
    options, inspect) {
        if (depth < 0) {
            return options.stylize(`[${this.constructor.name}]`, "special");
        }
        const newOptions = Object.assign({}, options, {
            depth: options.depth === null ? null : options.depth - 1
        });
        const { length  } = this;
        return `${options.stylize(this.constructor.name, "special")} ${inspect({
            length
        }, newOptions)}`;
    }
}
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