import {Result} from 'result'
import * as misc from 'misc'

export type Key = CryptoKey

export class SecretBox<T> {
    private readonly cipher: Uint8Array
    private readonly iv: Uint8Array
    private readonly phantom!: T

    private constructor(iv: Uint8Array, cipher: Uint8Array) {
        this.iv = iv
        this.cipher = cipher
    }

    public static async gen_key(extractable: boolean = false): Promise<Key> {
        return window.crypto.subtle.generateKey(
            {
                name: "AES-GCM",
                length: 256,
            },
            extractable,
            ["encrypt", "decrypt"]
        )
    }

    public static async encrypt<T>(key: Key, data: Uint8Array): Promise<Result<SecretBox<T>>> {
        const iv = window.crypto.getRandomValues(new Uint8Array(12))
        const algorithm = {name: "AES-GCM", iv}

        try {
            const cipher = await window.crypto.subtle.encrypt(algorithm, key, data)
            return Result.ok(new SecretBox(iv, new Uint8Array(cipher)))
        } catch (_) {}

        return Result.error([])
    }
    public async decrypt(key: Key): Promise<Result<Uint8Array>> {
        const algorithm = {name: "AES-GCM", iv: this.iv}

        try {
            const cipher = await window.crypto.subtle.decrypt(algorithm, key, this.cipher)
            const buffer = new Uint8Array(cipher)
            return Result.ok(buffer)
        } catch (_) {}

        return Result.error([])
    }

    public toString() : string {
        const iv = misc.a2b64(this.iv)
        const cipher = misc.a2b64(this.cipher)
        return `${iv}.${cipher}`
    }
    public static fromString<T>(data: string) : Result<SecretBox<T>> {
        const parts = data.split(".")
        if (parts.length !== 2) return Result.error([])

        const iv = misc.b642a(parts[0])
        const cipher = misc.b642a(parts[1])

        if (iv.error()) return Result.error([])
        if (cipher.error()) return Result.error([])

        return Result.ok(new SecretBox(iv.unwrap(), cipher.unwrap()))
    }
}