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Architecture

LocalStore

LocalStore is your one and only interface with the sharedPreferences on the device, accessed through WalletApplication instance. From here you have access to:

• encryptedPhrase The RSA encrypted mnemonic. If isPassphraseUsed is true, then the passphrase is appended to this mnemonic with a space seperating it.
• publicKey Public key for the Stellar account.
• balances An array of AccountResponse.Balance that either is empty on initialization or filled with the horizon server response.
• availableBalance A string of the available balance on the account.
• isRecoveryPhrase Boolean that indicates whether account was recovered with a recovery phrase (true) or with a secret seed (false)
• showPinOnSend Boolean that indicates whether to show PIN on sending payment
• isPassphraseUsed Boolean that indicates whether a passphrase was used to recover the account in addition to the mnemonic phrase.

UserSession

The UserSession object, accessed through WalletApplication instance, stores information about the current selected and displayed asset for the wallet.

Variables:

• currAssetCode String that is the current asset code (Examples: XLM, BTC, CAD, PTS)
• currAssetName String that is the current asset name (Examples: Stellar Lumens, Bitcoin, Canadian Dollar, Blockpoints)
• currAssetIssuer String that is the public address of the issuer of the current asset (Example: none for XLM, , )
• minimumBalance MinimumBalance object calculated from number of trustlines, signers, and offers.
• pin String that is the login PIN (this is required for making account operations that require PIN but we have chosen to cache it so we don't need to request it again: specifically for ChangeTrustline and JoinInflation)

Methods:

• fun getFormattedCurrentAssetCode() : String Returns a formatted current asset code "BTC"
• fun getAvailableBalance(): String Returns unformatted available balance "1.2000"
• fun getFormattedCurrentAvailableBalance(): String Returns a formatted current available balance. "Available: 1.2000 BTC"

AccountUtils

AccountUtils is a class that provides static methods for getting important Stellar account data.

Methods:

• fun getSecretSeed() : CharArray Returns the secret seed for the Stellar account, used for network calls and showing the secret seed
• fun getDecryptedMnemonicPhrasePair(encryptedPhrase: String, masterKey: java.security.KeyPair) : Pair<String, String?> Returns a Pair where the first String is the decrypted mnemonic phrase and the second String is the passphrase (if the account was not recovered with a passphrase, then this value is null)
• fun getTotalBalance(type : String) : String Returns the total balance of Stellar Lumens of the account
• fun getPinMasterKey(pin: String) : java.security.KeyPair? Returns the RSA KeyPair used to decrypt the mnemonic phrase
• fun getKeyPair(recoveryString: String, passphrase: String?) : KeyPair Returns the Stellar KeyPair
• fun calculateAvailableBalance(): String Calculates the available balance of the account by substracting minimum balance from the total balance

NetworkUtils

NetworkUtils provides methods for checking network status and displaying network errors to the user.

Methods:

• fun isNetworkAvailable(): Boolean Returns true if the network is available, else false
• fun displayNoNetwork() Displays a toast explaining a no network error

StringFormat

StringFormat provides static formatting functions.

Methods:

• fun getFormattedDate(str: String): String Consumes a UTC-Instant string date and returns a formatted MMM dd, uuuu string
• fun truncateDecimalPlaces(string: String?): String Rounds the input string number to 4 decimal places
• fun getNumDecimals(num: String): Int Calculate the number of decimals of a string
• fun hasDecimalPoint(text: String): Boolean Checks whether a string has a comma or not
• fun formatAssetCode(assetCode: String): String Converts native to xlm, otherwise returns the same asset code

Horizon

Horizon provides all the network calls to the Horizon Stellar api.

Methods:

• LoadAccountTask Gets account info, including balance
• LoadEffectsTask Gets the account effects list (account transactional/activity history)
• SendTask Sends a payment to a destination address
• JoinInflationDestination Sets the inflation destination address
• ChangeTrust Changes the trustline for an asset

How PinActivity works

How to launch: Call BaseActivity.launchPINView() specifying the type of PIN situation to use

PinTypes and what logic is applied after PIN is validated:

• CREATE: Creates a new stellar keypair from mnemonic phrase
• LOGIN: Launches the MainActivity
• VIEW_PHRASE: Launches ShowMnemonicActivity
• VIEW_SEED: Launches ViewSecretSeedActivity
• CLEAR_WALLET: Wipes all shared preferences and returns to LoginActivity
• CHECK: Returns secret seed to the calling activity

Refactoring suggestion

Create a Pin listener callback when launching the PinActivity and returns the secret seed that can be used for Horizon calls

Networking Architecture

• Right now using Volley for 1 network request to our own BlockEQ api that is outside of the Horizon SDK calls
  • AssetsActivity.kt > loadSupportedAssets()
  • This can be refactored to use Retrofit2, and remove Volley from the project

Additional notes

Things to add for app:

• Dependency injection (dagger)
• Kotlin coroutines instead of Asynctasks
• Retrofit2 as mentioned in networking