feat: add allowances for automatic paykit payments

app/build.gradle.kts

@@ -80,6 +80,7 @@ val e2eLocalHostEnv = providers.environmentVariable("E2E_LOCAL_HOST").orElse("10
 val e2eHomegateUrlEnv = providers.environmentVariable("E2E_HOMEGATE_URL")
     .orElse(e2eLocalHostEnv.map { "http://$it:6288" })
 val e2eHomeserverPubkyEnv = providers.environmentVariable("E2E_HOMESERVER_PUBKY").orElse("")
+val e2eHomegateOverrideEnv = providers.environmentVariable("E2E_HOMEGATE_URL").orElse("")
 val geoEnv = envFlag("GEO", default = true)
 val paykitUiDisabledEnv = envFlag("PAYKIT_UI_DISABLED", default = false)
 val trezorBridgeEnv = localProp("TREZOR_BRIDGE").map { it.toBoolean().toString() }.orElse("false")
@@ -325,6 +326,7 @@ androidComponents {
         buildConfigFields.put("E2E_LOCAL_HOST", e2eLocalHostEnv.stringField())
         buildConfigFields.put("E2E_HOMEGATE_URL", e2eHomegateUrlEnv.stringField())
         buildConfigFields.put("E2E_HOMESERVER_PUBKY", e2eHomeserverPubkyEnv.stringField())
+        buildConfigFields.put("E2E_HOMEGATE_OVERRIDE", e2eHomegateOverrideEnv.stringField())
         buildConfigFields.put("TREZOR_BRIDGE", trezorBridgeEnv.booleanField())
         buildConfigFields.put("TREZOR_BRIDGE_URL", trezorBridgeUrlEnv.stringField())
         buildConfigFields.put("GEO", geoEnv.booleanField())

app/src/main/java/to/bitkit/data/keychain/Keychain.kt

@@ -236,6 +236,7 @@ class Keychain @Inject constructor(
         PAYKIT_SDK_STATE,
         PAYKIT_PENDING_PAYMENT_PROOFS,
         PAYKIT_PRESENTED_PAYMENT_REQUESTS,
+        PAYKIT_ALLOWANCE_STATE,
         PUBKY_SECRET_KEY,
     }
 }

app/src/main/java/to/bitkit/env/Env.kt

@@ -169,6 +169,10 @@ internal object Env {
 
     val homegateUrl: String
         get() {
+            // An explicit E2E_HOMEGATE_URL wins on every backend, as on iOS: demos run their own homegate.
+            if (isE2eTest && BuildConfig.E2E_HOMEGATE_OVERRIDE.isNotBlank()) {
+                return BuildConfig.E2E_HOMEGATE_OVERRIDE
+            }
             if (isLocalE2eBackend) {
                 return e2eHomegateUrl
             }

app/src/main/java/to/bitkit/repositories/PaykitAllowance.kt

@@ -0,0 +1,276 @@
+package to.bitkit.repositories
+
+import androidx.compose.runtime.Immutable
+import com.synonym.paykit.AllowanceAccountingHistory
+import com.synonym.paykit.AllowanceAmountRange
+import com.synonym.paykit.AllowanceLifecycleState
+import com.synonym.paykit.AllowanceLocalRole
+import com.synonym.paykit.AllowancePeriod
+import com.synonym.paykit.AllowancePeriodLimit
+import com.synonym.paykit.AllowanceRecord
+import com.synonym.paykit.AllowanceTerms
+import com.synonym.paykit.PaymentExecutionMode
+import com.synonym.paykit.PaymentExecutionStatus
+import kotlinx.serialization.Serializable
+import to.bitkit.models.safe
+import to.bitkit.services.PaykitReceiverPaths
+import java.math.BigDecimal
+import java.time.ZoneOffset
+import java.time.ZonedDateTime
+import java.time.format.DateTimeFormatter
+import java.time.temporal.ChronoUnit
+import kotlin.time.Instant
+import kotlin.time.toJavaInstant
+import kotlin.time.toKotlinInstant
+
+/**
+ * An Allowance between this wallet and one contact link, built from the SDK record.
+ * Eligibility always runs on real time.
+ */
+@Immutable
+data class PaykitAllowance(
+    val id: Id,
+    val role: Role,
+    val lifecycleState: AllowanceLifecycleState,
+    val isProposedByMe: Boolean,
+    val perPaymentMaxSats: ULong?,
+    val monthlyLimitSats: ULong?,
+    val monthlyAnchor: Instant?,
+    val activeFrom: Instant? = null,
+    val expiresAt: Instant? = null,
+    val allowedPaymentEndpointIdentifiers: List<String>? = null,
+    val lastEventAt: Instant? = null,
+) {
+    @Serializable
+    data class Id(
+        val counterparty: String,
+        val counterpartyReceiverPath: String,
+        val allowanceId: String,
+    )
+
+    @Serializable
+    enum class Role { ALLOWER, ALLOWEE }
+
+    enum class Status {
+        /** Sent by this wallet; the other side has not answered yet. */
+        AWAITING_ANSWER,
+
+        /** Received; this wallet must accept or decline. */
+        AWAITING_MY_ANSWER,
+        ACTIVE,
+        NOT_YET_ACTIVE,
+        EXPIRED,
+        DECLINED,
+        ENDED,
+        CONFLICTED,
+    }
+
+    val counterparty: String get() = id.counterparty
+    val counterpartyReceiverPath: String get() = id.counterpartyReceiverPath
+    val allowanceId: String get() = id.allowanceId
+
+    /** The payer side: this wallet pays the counterparty's requests automatically. */
+    val isAllower: Boolean get() = role == Role.ALLOWER
+
+    val canEnd: Boolean
+        get() = when (lifecycleState) {
+            AllowanceLifecycleState.ACCEPTED -> true
+            AllowanceLifecycleState.PROPOSED -> isProposedByMe
+            else -> false
+        }
+
+    val isAnswerable: Boolean get() = lifecycleState == AllowanceLifecycleState.PROPOSED && !isProposedByMe
+
+    fun status(now: Instant): Status = when (lifecycleState) {
+        AllowanceLifecycleState.PROPOSED -> if (isProposedByMe) Status.AWAITING_ANSWER else Status.AWAITING_MY_ANSWER
+        AllowanceLifecycleState.ACCEPTED -> when {
+            expiresAt != null && now >= expiresAt -> Status.EXPIRED
+            activeFrom != null && now < activeFrom -> Status.NOT_YET_ACTIVE
+            else -> Status.ACTIVE
+        }
+        AllowanceLifecycleState.REJECTED -> Status.DECLINED
+        AllowanceLifecycleState.ENDED -> Status.ENDED
+        AllowanceLifecycleState.CONFLICTED, AllowanceLifecycleState.UNKNOWN -> Status.CONFLICTED
+    }
+
+    companion object {
+        fun from(record: AllowanceRecord): PaykitAllowance? {
+            val role = when (record.localRole) {
+                AllowanceLocalRole.ALLOWER -> Role.ALLOWER
+                AllowanceLocalRole.ALLOWEE -> Role.ALLOWEE
+                else -> return null
+            }
+            val terms = record.terms ?: return null
+            if (terms.asset() != PaykitIssuerInterop.BITCOIN_ASSET) return null
+            val monthly = terms.periodLimits().firstOrNull { isMonthly(it.period()) }
+            return PaykitAllowance(
+                id = Id(record.counterparty, record.counterpartyReceiverPath, record.allowanceId),
+                role = role,
+                lifecycleState = record.state,
+                isProposedByMe = record.proposalOutboundMessageId != null,
+                perPaymentMaxSats = terms.perPaymentAmount()?.let { satsFromBitcoinAmount(it.maximum()) },
+                monthlyLimitSats = monthly?.amountLimit()?.let(::satsFromBitcoinAmount),
+                monthlyAnchor = monthly?.period()?.anchor()?.let(PaykitAllowanceTime::parse),
+                activeFrom = terms.activeFrom()?.let(PaykitAllowanceTime::parse),
+                expiresAt = terms.expiresAt()?.let(PaykitAllowanceTime::parse),
+                allowedPaymentEndpointIdentifiers = terms.allowedPaymentEndpointIdentifiers(),
+                lastEventAt = record.lastEventAt?.let(PaykitAllowanceTime::parse),
+            )
+        }
+
+        fun isMonthly(period: AllowancePeriod): Boolean =
+            period.kind() == "anchored" && period.every() == 1uL && period.unit() == "month"
+
+        /** BTC decimal string to sats; unlike [toPaykitSats] a zero amount is valid here. */
+        fun satsFromBitcoinAmount(amount: String): ULong? {
+            if (amount.split('.').all { part -> part.all { it == '0' } }) return 0uL
+            return amount.toPaykitSats()
+        }
+    }
+}
+
+/** One grant as the user sees it: the same limits proposed on each of a contact's supported links. */
+@Immutable
+data class PaykitAllowanceEntry(
+    val id: String,
+    val allowances: List<PaykitAllowance>,
+    val limits: PaykitAllowanceLimits?,
+) {
+    /** An accepted link before any other, and the contact's wallet link before their server link. */
+    val primary: PaykitAllowance
+        get() = allowances.minBy {
+            val acceptedRank = if (it.lifecycleState == AllowanceLifecycleState.ACCEPTED) 0 else 2
+            val walletRank = if (it.counterpartyReceiverPath == PaykitReceiverPaths.WALLET) 0 else 1
+            acceptedRank + walletRank
+        }
+    val counterparty: String get() = primary.counterparty
+    val role: PaykitAllowance.Role get() = primary.role
+    val perPaymentMaxSats: ULong? get() = primary.perPaymentMaxSats
+    val monthlyLimitSats: ULong? get() = primary.monthlyLimitSats
+    val canEnd: Boolean get() = allowances.any { it.canEnd }
+    val isAnswerable: Boolean get() = allowances.any { it.isAnswerable }
+
+    fun status(now: Instant): PaykitAllowance.Status = primary.status(now)
+}
+
+/** Limits picked in USD on the Set Allowance sheet, converted once to whole-sat BTC terms. */
+@Serializable
+@Immutable
+data class PaykitAllowanceLimits(
+    val perPaymentUsd: Int,
+    val monthlyUsd: Int,
+    val perPaymentSats: ULong,
+    val monthlySats: ULong,
+) {
+    /**
+     * Terms Bitkit proposes: per-payment range 0...max, an anchored UTC calendar month, and the endpoints Bitkit pays.
+     */
+    fun terms(monthAnchor: Instant, allowedPaymentEndpointIdentifiers: List<String>): AllowanceTerms {
+        val perPayment = AllowanceAmountRange(minimum = "0", maximum = perPaymentSats.toBitcoinDecimal())
+        val month = AllowancePeriod(
+            kind = "anchored",
+            every = 1uL,
+            unit = "month",
+            anchor = PaykitAllowanceTime.format(monthAnchor),
+        )
+        val monthly = AllowancePeriodLimit(
+            amountLimit = monthlySats.toBitcoinDecimal(),
+            paymentCountLimit = null,
+            period = month,
+        )
+        return AllowanceTerms(
+            asset = PaykitIssuerInterop.BITCOIN_ASSET,
+            perPaymentAmount = perPayment,
+            periodLimits = listOf(monthly),
+            lifetimeAmountLimit = null,
+            activeFrom = null,
+            expiresAt = null,
+            allowedPaymentEndpointIdentifiers = allowedPaymentEndpointIdentifiers,
+        )
+    }
+
+    companion object {
+        /** Slider stops on the Set Allowance sheet, in whole US dollars. */
+        val PER_PAYMENT_STOPS_USD = listOf(1, 5, 10, 20, 50)
+
+        /** Slider stops on the Set Allowance sheet, in whole US dollars. */
+        val MONTHLY_STOPS_USD = listOf(10, 50, 100, 200, 500)
+    }
+}
+
+internal fun ULong.toBitcoinDecimal(): String =
+    BigDecimal(toString()).movePointLeft(8).stripTrailingZeros().toPlainString()
+
+object PaykitAllowanceTime {
+    private val utc = ZoneOffset.UTC
+
+    fun format(instant: Instant): String =
+        DateTimeFormatter.ISO_INSTANT.format(instant.toJavaInstant().truncatedTo(ChronoUnit.MILLIS))
+
+    fun parse(value: String): Instant? = runCatching { Instant.parse(value) }.getOrNull()
+
+    /** First instant of the UTC calendar month that contains [instant]. */
+    fun monthStart(containing: Instant): Instant = ZonedDateTime.ofInstant(containing.toJavaInstant(), utc)
+        .withDayOfMonth(1)
+        .truncatedTo(ChronoUnit.DAYS)
+        .toInstant()
+        .toKotlinInstant()
+
+    /**
+     * The anchored monthly window `[start, end)` that contains [instant]. Anchors on a day that a short month lacks
+     * clamp to that month's last day, as the spec's anchored-period arithmetic does.
+     */
+    fun monthlyWindow(anchor: Instant, containing: Instant): Pair<Instant, Instant> {
+        val anchorTime = ZonedDateTime.ofInstant(anchor.toJavaInstant(), utc)
+        val dateTime = ZonedDateTime.ofInstant(containing.toJavaInstant(), utc)
+        // Every boundary counts from the original anchor, so a clamped February never shortens later months.
+        val boundary = { index: Long -> anchorTime.plusMonths(index).toInstant().toKotlinInstant() }
+        var index = (dateTime.year - anchorTime.year) * 12L + dateTime.monthValue - anchorTime.monthValue
+        while (boundary(index) > containing) index--
+        while (boundary(index + 1) <= containing) index++
+        return boundary(index) to boundary(index + 1)
+    }
+}
+
+/**
+ * Wallet-side capacity preflight. The SDK checks capacity only after automatic Acceptance, so Bitkit sums this
+ * Allowance's live automatic attempts in the current month first and keeps an over-cap request on the manual flow.
+ */
+object PaykitAllowanceCapacity {
+    data class Attempt(
+        val allowanceId: String,
+        val amountSats: ULong,
+        val admittedAt: Instant,
+        val isLive: Boolean,
+    )
+
+    fun usedSats(allowanceId: String, attempts: List<Attempt>, anchor: Instant, now: Instant): ULong {
+        val (start, end) = PaykitAllowanceTime.monthlyWindow(anchor, now)
+        return attempts
+            .filter { it.allowanceId == allowanceId && it.isLive && it.admittedAt >= start && it.admittedAt < end }
+            .fold(0uL) { total, attempt -> total.safe() + attempt.amountSats.safe() }
+    }
+
+    fun fits(amountSats: ULong, allowance: PaykitAllowance, attempts: List<Attempt>, now: Instant): Boolean {
+        val perPaymentMax = allowance.perPaymentMaxSats
+        if (perPaymentMax != null && amountSats > perPaymentMax) return false
+        val monthlyLimit = allowance.monthlyLimitSats ?: return true
+        val anchor = allowance.monthlyAnchor ?: return true
+        return usedSats(allowance.allowanceId, attempts, anchor, now).safe() + amountSats.safe() <= monthlyLimit
+    }
+
+    fun attempts(history: AllowanceAccountingHistory): List<Attempt> = history.occurrences
+        .flatMap { it.attempts }
+        .mapNotNull { attempt ->
+            if (attempt.mode != PaymentExecutionMode.AUTOMATIC) return@mapNotNull null
+            val allowanceId = attempt.allowanceId ?: return@mapNotNull null
+            val admittedAt = PaykitAllowanceTime.parse(attempt.admittedAt) ?: return@mapNotNull null
+            val amountSats = PaykitAllowance.satsFromBitcoinAmount(attempt.amount.value()) ?: return@mapNotNull null
+            Attempt(
+                allowanceId = allowanceId,
+                amountSats = amountSats,
+                admittedAt = admittedAt,
+                isLive = attempt.status != PaymentExecutionStatus.FAILED,
+            )
+        }
+}