zcash-android-wallet-sdk/demo-app/src/main/java/cash/z/ecc/android/sdk/demoapp/demos/getprivatekey/GetPrivateKeyFragment.kt

package cash.z.ecc.android.sdk.demoapp.demos.getprivatekey

import android.os.Bundle
import android.view.LayoutInflater
import cash.z.ecc.android.bip39.Mnemonics
import cash.z.ecc.android.bip39.toSeed
import cash.z.ecc.android.sdk.demoapp.BaseDemoFragment
import cash.z.ecc.android.sdk.demoapp.databinding.FragmentGetPrivateKeyBinding
import cash.z.ecc.android.sdk.tool.DerivationTool

/**
 * Displays the viewing key and spending key associated with the seed used during the demo. The
 * seedPhrase defaults to the value of`DemoConfig.seedWords` but can be set by the user on the
 * HomeFragment.
 */
class GetPrivateKeyFragment : BaseDemoFragment<FragmentGetPrivateKeyBinding>() {

    private lateinit var seedPhrase: String
    private lateinit var seed: ByteArray

    /**
     * Initialize the required values that would normally live outside the demo but are repeated
     * here for completeness so that each demo file can serve as a standalone example.
     */
    private fun setup() {
        // defaults to the value of `DemoConfig.seedWords` but can also be set by the user
        seedPhrase = sharedViewModel.seedPhrase.value

        // Use a BIP-39 library to convert a seed phrase into a byte array. Most wallets already
        // have the seed stored
        seed = Mnemonics.MnemonicCode(seedPhrase).toSeed()
    }

    private fun displayKeys() {
        // derive the keys from the seed:
        // demonstrate deriving spending keys for five accounts but only take the first one
        val spendingKey = DerivationTool.deriveSpendingKeys(seed, 5).first()

        // derive the key that allows you to view but not spend transactions
        val viewingKey = DerivationTool.deriveViewingKey(spendingKey)

        // display the keys in the UI
        binding.textInfo.setText("Spending Key:\n$spendingKey\n\nViewing Key:\n$viewingKey")
    }


    //
    // Android Lifecycle overrides
    //

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        setup()
    }

    override fun onResume() {
        super.onResume()
        displayKeys()
    }


    //
    // Base Fragment overrides
    //

    override fun onActionButtonClicked() {
        copyToClipboard(
            DerivationTool.deriveViewingKeys(seed, 1).first(),
            "ViewingKey copied to clipboard!"
        )
    }

    override fun inflateBinding(layoutInflater: LayoutInflater): FragmentGetPrivateKeyBinding =
        FragmentGetPrivateKeyBinding.inflate(layoutInflater)

}