import logger from 'log'
const log = logger('crypto:kdf')

export enum Usage {
    sign,
    wrap,
}
export async function hkdf(key: Uint8Array, usage: Usage) : Promise<CryptoKey | Uint8Array> {
    log.trace("HKDF")
    log.trace(`usage : ${usage === Usage.sign ? 'sign' : 'wrap'}`)

    const material = await crypto.subtle.importKey(
        "raw",
        key,
        "HKDF",
        false,
        ["deriveKey", "deriveBits"],
    )

    if (usage === Usage.wrap) {
        return crypto.subtle.deriveKey(
            {
                name: "HKDF",
                hash: "SHA-512",
                salt: new Uint8Array(32),
                info: new TextEncoder().encode("wrap"),
            },
            material,
            {name: "AES-GCM", length: 256},
            false,
            ["wrapKey", "unwrapKey"],
        )
    } else if (usage === Usage.sign) {
        const buffer = await crypto.subtle.deriveBits(
            {
                name: "HKDF",
                hash: "SHA-512",
                salt: new Uint8Array(32),
                info: new TextEncoder().encode("sign"),
            },
            material,
            512
        )
        return new Uint8Array(buffer)
    } else {
        log.warn(`Called HKDF with unknown enum value : ${usage}`)
        throw "I don't even know what to say."
    }
}

export async function pbkdf(salt: Uint8Array, password: string) : Promise<Uint8Array> {
    log.trace("PBKDF")
    const material = await crypto.subtle.importKey(
        "raw",
        new TextEncoder().encode(password),
        "PBKDF2",
        false,
        ["deriveBits"],
    )

    const buffer = await crypto.subtle.deriveBits(
        {
            name: "PBKDF2",
            salt,
            iterations: 250_000,
            hash: "SHA-512",
        },
        material,
        256,
    )

    return new Uint8Array(buffer)
}

export function ecdh(privkey: CryptoKey, pubkey: CryptoKey) : Promise<CryptoKey> {
    log.trace("ECDH")
    return crypto.subtle.deriveKey(
        {
            name: "ECDH",
            public: pubkey,
        },
        privkey,
        {
            name: "AES-GCM",
            length: 256,
        },
        false,
        ["wrapKey", "unwrapKey"],
    )
}