// Taken from https://github.com/ehn-dcc-development/ehn-sign-verify-javascript-trivial/blob/main/cose_verify.js
// and https://github.com/ehn-dcc-development/dgc-check-mobile-app/blob/2c2ebf4e9b7650ceef44f7e1fb05a57572830c5b/src/app/cose-js/sign.js

const base45 = require('base45-js')
const zlib = require('pako')
const cbor = require('cbor-js')

export function typedArrayToBufferSliced(array) {
    return array.buffer.slice(array.byteOffset, array.byteLength + array.byteOffset)
}

export function typedArrayToBuffer(array) {
    var buffer = new ArrayBuffer(array.length)

    array.map(function (value, i) {
        buffer[i] = value
    })
    return array.buffer
}

export function decodeData(data) {
    data = data.toString('ASCII')

    if (data.startsWith('HC1')) {
        data = data.substring(3)
        if (data.startsWith(':')) {
            data = data.substring(1)
        } else {
            console.log("Warning: unsafe HC1: header - update to v0.0.4")
        }
    } else {
        console.log("Warning: no HC1: header - update to v0.0.4")
    }

    data = base45.decode(data)

    if (data[0] == 0x78) {
        data = zlib.inflate(data)
    }

    data = cbor.decode(typedArrayToBuffer(data))

    if (!Array.isArray(data)) {
        throw new Error('Expecting Array')
    }

    if (data.length !== 4) {
        throw new Error('Expecting Array of length 4')
    }

    let plaintext = data[2]
    let decoded = cbor.decode(typedArrayToBufferSliced(plaintext))

    return decoded
}