refactor(zap): merge on-chain amount presets into the single zap-amount list

The on-chain rail no longer has its own editable preset list. There is now one zap-amount list used by every rail; on-chain simply filters it by the shared MIN_ONCHAIN_ZAP_SATS floor (1000 sat), and the unified chip already gates each logo per amount. - Settings: drop the public onchainZapAmountChoices StateFlow and its editor section in the Update Zap Amount dialog. The serialized field is kept for backward/cross-client (NIP-78) compatibility and migration: on load the two saved lists are unioned into zapAmountChoices (mergeZapAmounts), and on save the on-chain-eligible subset is written back so older clients still get sensible on-chain presets. The round-trip is idempotent. - updateZapAmounts / changeOnchainZapAmounts lose the separate on-chain parameter throughout (Account, AccountViewModel, UpdateZapAmountViewModel). - OnchainZapSendDialog draws its quick presets from the single list filtered by the minimum. - MIN_ONCHAIN_ZAP_SATS is now a single shared constant in the model, replacing the copies previously private to OnchainZapSendDialog and ReactionsRow. - Remove the now-unused on-chain amount strings; clarify the zap-amounts explainer to note amounts apply to all rails. Adds ZapAmountMergeTest covering the union/dedup/idempotent-round-trip. https://claude.ai/code/session_01HNE2z7CSYZ2G8KwC5fziJn
2026-08-11 00:37:41 +00:00 · 2026-05-29 18:28:48 +00:00
parent c1c1a69148
commit 6f7cacf84b
13 changed files with 120 additions and 173 deletions
@@ -652,14 +652,12 @@ class Account(

    suspend fun updateZapAmounts(
        amountSet: List<Long>,
-        onchainAmountSet: List<Long>,
        selectedZapType: LnZapEvent.ZapType,
        nip47Update: Nip47WalletConnect.Nip47URINorm?,
    ) {
        var changed = false

        if (settings.changeZapAmounts(amountSet)) changed = true
-        if (settings.changeOnchainZapAmounts(onchainAmountSet)) changed = true
        if (settings.changeDefaultZapType(selectedZapType)) changed = true
        if (settings.changeZapPaymentRequest(nip47Update)) changed = true

@@ -291,15 +291,6 @@ class AccountSettings(
        return false
    }

-    fun changeOnchainZapAmounts(newAmounts: List<Long>): Boolean {
-        if (syncedSettings.zaps.onchainZapAmountChoices.value != newAmounts) {
-            syncedSettings.zaps.onchainZapAmountChoices.tryEmit(newAmounts.toImmutableList())
-            saveAccountSettings()
-            return true
-        }
-        return false
-    }
-
    fun changeReactionTypes(newTypes: List<String>): Boolean {
        if (syncedSettings.reactions.reactionChoices.value != newTypes) {
            syncedSettings.reactions.reactionChoices.tryEmit(newTypes.toImmutableList())
@@ -39,8 +39,7 @@ class AccountSyncedSettings(
        )
    val zaps =
        AccountZapPreferences(
-            MutableStateFlow(internalSettings.zaps.zapAmountChoices.toImmutableList()),
-            MutableStateFlow(internalSettings.zaps.onchainZapAmountChoices.toImmutableList()),
+            MutableStateFlow(mergeZapAmounts(internalSettings.zaps).toImmutableList()),
            MutableStateFlow(internalSettings.zaps.defaultZapType),
        )
    val languages =
@@ -70,7 +69,10 @@ class AccountSyncedSettings(
            zaps =
                AccountZapPreferencesInternal(
                    zaps.zapAmountChoices.value,
-                    zaps.onchainZapAmountChoices.value,
+                    // Write the on-chain-eligible subset into the legacy field so
+                    // older clients still get sensible on-chain presets. Unioning
+                    // it back on load is idempotent (subset ⊆ full list).
+                    zaps.zapAmountChoices.value.filter { it >= MIN_ONCHAIN_ZAP_SATS },
                    zaps.defaultZapType.value,
                ),
            languages =
@@ -104,16 +106,11 @@ class AccountSyncedSettings(
            reactions.reactionRowItems.tryEmit(newReactionRowItems)
        }

-        val newZapChoices = syncedSettingsInternal.zaps.zapAmountChoices.toImmutableList()
+        val newZapChoices = mergeZapAmounts(syncedSettingsInternal.zaps).toImmutableList()
        if (!equalImmutableLists(zaps.zapAmountChoices.value, newZapChoices)) {
            zaps.zapAmountChoices.tryEmit(newZapChoices)
        }

-        val newOnchainZapChoices = syncedSettingsInternal.zaps.onchainZapAmountChoices.toImmutableList()
-        if (!equalImmutableLists(zaps.onchainZapAmountChoices.value, newOnchainZapChoices)) {
-            zaps.onchainZapAmountChoices.tryEmit(newOnchainZapChoices)
-        }
-
        if (zaps.defaultZapType.value != syncedSettingsInternal.zaps.defaultZapType) {
            zaps.defaultZapType.tryEmit(syncedSettingsInternal.zaps.defaultZapType)
        }
@@ -182,10 +179,18 @@ class AccountVideoPlayerPreferences(
@Stable
 class AccountZapPreferences(
    var zapAmountChoices: MutableStateFlow<ImmutableList<Long>>,
-    var onchainZapAmountChoices: MutableStateFlow<ImmutableList<Long>>,
    val defaultZapType: MutableStateFlow<LnZapEvent.ZapType>,
 )

+/**
+ * Union the (historically separate) zap and on-chain preset lists into the
+ * single sorted set the app now uses everywhere. Preserves amounts customized
+ * on either side and amounts synced from an older client that still writes the
+ * legacy `onchainZapAmountChoices`. Idempotent: [AccountSyncedSettings.toInternal]
+ * re-derives the on-chain field as a subset of this list.
+ */
+internal fun mergeZapAmounts(zaps: AccountZapPreferencesInternal): List<Long> = (zaps.zapAmountChoices + zaps.onchainZapAmountChoices).distinct().sorted()
+
@Stable
 class AccountLanguagePreferences(
    var dontTranslateFrom: MutableStateFlow<Set<String>>,
@@ -41,6 +41,16 @@ val DefaultZapAmounts = listOf(21L, 50L, 100L)
 val DefaultOnchainZapAmounts = listOf(5_000L)
 val DefaultReportWarningThreshold = 5

+/**
+ * Product floor for the on-chain rail — stricter than the protocol-level
+ * dust threshold (OnchainZapBuilder.DUST_THRESHOLD_SATS). The unified zap
+ * picker offers the on-chain logo only for amounts at or above this, and the
+ * on-chain send dialog draws its presets from the single zap-amount list
+ * filtered by it. Single source of truth for everywhere that gates on-chain
+ * by amount.
+ */
+const val MIN_ONCHAIN_ZAP_SATS = 1_000L
+
@Serializable
 enum class ReactionRowAction {
    Reply,
@@ -154,6 +164,11 @@ class AccountReactionPreferencesInternal(
@Serializable
 class AccountZapPreferencesInternal(
    var zapAmountChoices: List<Long> = DefaultZapAmounts,
+    // Legacy field: the on-chain rail no longer has its own editable preset
+    // list — amounts live in [zapAmountChoices] and on-chain just filters by
+    // [MIN_ONCHAIN_ZAP_SATS]. Kept (de)serialized so older clients still sync
+    // and so the on-chain-eligible subset round-trips back for them; on load it
+    // is unioned into [zapAmountChoices]. See AccountSyncedSettings.
    var onchainZapAmountChoices: List<Long> = DefaultOnchainZapAmounts,
    val defaultZapType: LnZapEvent.ZapType = LnZapEvent.ZapType.PUBLIC,
 )
@@ -99,8 +99,8 @@ object RailCapabilityResolver {
     *    derives the Taproot address from the recipient pubkey, so any nostr
     *    pubkey is payable; lnAddress-only recipients are not (they have no
     *    pubkey to tweak). The sender's onchain wallet availability is a
-     *    *sender* concern — handled elsewhere by the popup gating the chip
-     *    on `onchainZapAmountChoices` and the dialog on `LocalCache.onchainBackend`.
+     *    *sender* concern — handled elsewhere by the chip gating on-chain by
+     *    `MIN_ONCHAIN_ZAP_SATS` and the dialog on `LocalCache.onchainBackend`.
     */
    fun peek(
        baseNote: Note,
@@ -44,7 +44,6 @@ import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
-import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.model.Note
 import com.vitorpamplona.amethyst.model.User
@@ -110,10 +109,6 @@ fun ReusableZapButton(
    var onchainZapAmount by remember { mutableStateOf<Long?>(null) }
    var showOnchainDialog by remember { mutableStateOf(false) }

-    val onchainZapAmountChoices by
-        accountViewModel.account.settings.syncedSettings.zaps.onchainZapAmountChoices
-            .collectAsStateWithLifecycle()
-
    // Makes sure the user is loaded to get his ln address ahead of time (for DVM buttons)
    if (config.showUserFinderSubscription) {
        baseNote.author?.let { author ->
@@ -201,7 +196,6 @@ fun ReusableZapButton(
                        nav.nav(Route.ManualZapSplitPayment(uid))
                    }
                },
-                onchainZapAmountChoices = onchainZapAmountChoices,
                onOnchainAmount = { amount ->
                    wantsToZap = null
                    onchainZapAmount = amount
@@ -110,6 +110,7 @@ import com.vitorpamplona.amethyst.commons.hashtags.Cashu
 import com.vitorpamplona.amethyst.commons.hashtags.CustomHashTagIcons
 import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+import com.vitorpamplona.amethyst.model.MIN_ONCHAIN_ZAP_SATS
 import com.vitorpamplona.amethyst.model.Note
 import com.vitorpamplona.amethyst.model.ReactionRowAction
 import com.vitorpamplona.amethyst.model.ReactionRowItem
@@ -1888,9 +1889,6 @@ fun ZapAmountChoicePopup(
    val zapAmountChoices by
        accountViewModel.account.settings.syncedSettings.zaps.zapAmountChoices
            .collectAsStateWithLifecycle()
-    val onchainZapAmountChoices by
-        accountViewModel.account.settings.syncedSettings.zaps.onchainZapAmountChoices
-            .collectAsStateWithLifecycle()

    ZapAmountChoicePopup(
        baseNote = baseNote,
@@ -1903,7 +1901,6 @@ fun ZapAmountChoicePopup(
        onError = onError,
        onProgress = onProgress,
        onPayViaIntent = onPayViaIntent,
-        onchainZapAmountChoices = onchainZapAmountChoices,
        onOnchainAmount = onOnchainAmount ?: {},
        onchainSupported = onOnchainAmount != null,
    )
@@ -1921,15 +1918,14 @@ fun ZapAmountChoicePopup(
    onError: (title: String, text: String, user: User?) -> Unit,
    onProgress: (percent: Float) -> Unit,
    onPayViaIntent: (ImmutableList<ZapPaymentHandler.Payable>) -> Unit,
-    onchainZapAmountChoices: ImmutableList<Long> = persistentListOf(),
    onOnchainAmount: (Long?) -> Unit = {},
    onchainSupported: Boolean = true,
 ) {
-    // One chip per amount; the chip itself shows which rails can pay it. Merge
-    // the (historically separate) Lightning and on-chain amount presets into a
-    // single sorted set of choices. Rail availability per amount is decided in
-    // [UnifiedZapAmountChip] from [railCapability], so the lists no longer need
-    // to be pre-emptied per rail.
+    // One chip per amount; the chip itself shows which rails can pay it.
+    // [zapAmountChoices] is already the single merged+sorted preset list (the
+    // on-chain amounts were folded in at the settings layer), so rail
+    // availability per amount is decided in [UnifiedZapAmountChip] from
+    // [railCapability] rather than by keeping separate per-rail lists.
    //
    // [railCapability] gates which rails the recipient can receive on (plus the
    // sender's cashu balance, which is free to read). It's recomputed only when
@@ -1942,8 +1938,8 @@ fun ZapAmountChoicePopup(
            if (onchainSupported) rc else rc.copy(hasOnchain = false)
        }
    val amountChoices =
-        remember(zapAmountChoices, onchainZapAmountChoices) {
-            (zapAmountChoices + onchainZapAmountChoices).distinct().sorted().toImmutableList()
+        remember(zapAmountChoices) {
+            zapAmountChoices.distinct().sorted().toImmutableList()
        }
    val visibilityState = rememberVisibilityState(onDismiss)
    ZapAmountChoicePopup(
@@ -2087,14 +2083,6 @@ fun ZapAmountChoicePopupContent(
    }
 }

-/**
- * Floor for the on-chain rail. Mirrors `MIN_ONCHAIN_ZAP_SATS` in
- * `OnchainZapSendDialog` (stricter than the protocol dust threshold); kept in
- * sync by hand because that one is private to the dialog. Below this the
- * on-chain logo is not offered for an amount.
- */
-private const val MIN_ONCHAIN_ZAP_SATS = 1_000L
-
 /**
 * One pill per amount, showing a tappable logo for every rail that can pay it:
 *  - **Cashu** only when a single shared mint is already funded for the amount
@@ -339,96 +339,7 @@ fun UpdateZapAmountContent(
            )
        }

-        // ── Section 3: Quick On-chain Zap Amounts ─────────────────────────────
-
-        Text(
-            text = stringRes(R.string.quick_zap_amounts_onchain),
-            color = MaterialTheme.colorScheme.primary,
-            style = MaterialTheme.typography.titleSmall,
-            modifier = SettingsCategorySpacingModifier,
-        )
-        Text(
-            text = stringRes(R.string.quick_zap_amounts_onchain_explainer),
-            style = MaterialTheme.typography.bodySmall,
-            color = MaterialTheme.colorScheme.placeholderText,
-            modifier = Modifier.padding(bottom = 6.dp),
-        )
-
-        FlowRow(
-            modifier =
-                Modifier
-                    .fillMaxWidth()
-                    .animateContentSize(animationSpec = spring(stiffness = Spring.StiffnessMediumLow)),
-            horizontalArrangement = Arrangement.spacedBy(6.dp),
-            verticalArrangement = Arrangement.spacedBy(6.dp),
-        ) {
-            postViewModel.onchainAmountSet.forEach { amountInSats ->
-                InputChip(
-                    selected = false,
-                    onClick = { postViewModel.removeOnchainAmount(amountInSats) },
-                    label = {
-                        Text(
-                            text = "₿ ${showAmount(amountInSats.toBigDecimal().setScale(1))}",
-                        )
-                    },
-                    trailingIcon = {
-                        Icon(
-                            symbol = MaterialSymbols.Close,
-                            contentDescription = stringRes(R.string.remove),
-                            modifier = Modifier.size(InputChipDefaults.AvatarSize),
-                        )
-                    },
-                    colors =
-                        InputChipDefaults.inputChipColors(
-                            containerColor = MaterialTheme.colorScheme.primary.copy(alpha = 0.12f),
-                            labelColor = MaterialTheme.colorScheme.primary,
-                            trailingIconColor = MaterialTheme.colorScheme.primary,
-                        ),
-                )
-            }
-        }
-
-        Spacer(modifier = Modifier.height(6.dp))
-
-        Row(
-            modifier = Modifier.fillMaxWidth(),
-            verticalAlignment = Alignment.CenterVertically,
-            horizontalArrangement = Arrangement.spacedBy(8.dp),
-        ) {
-            OutlinedTextField(
-                label = { Text(text = stringRes(R.string.new_amount_in_sats_onchain)) },
-                value = postViewModel.nextOnchainAmount,
-                onValueChange = { postViewModel.nextOnchainAmount = it },
-                keyboardOptions =
-                    KeyboardOptions.Default.copy(
-                        capitalization = KeyboardCapitalization.None,
-                        keyboardType = KeyboardType.Number,
-                    ),
-                placeholder = {
-                    Text(
-                        text = "5000, 25000, 100000",
-                        color = MaterialTheme.colorScheme.placeholderText,
-                    )
-                },
-                trailingIcon = {
-                    IconButton(
-                        onClick = postViewModel::addOnchainAmount,
-                        shape = ButtonBorder,
-                        enabled = postViewModel.nextOnchainAmount.text.isNotBlank(),
-                    ) {
-                        Icon(
-                            symbol = MaterialSymbols.AddCircle,
-                            contentDescription = stringRes(R.string.add),
-                            modifier = Size20Modifier,
-                        )
-                    }
-                },
-                singleLine = true,
-                modifier = Modifier.weight(1f),
-            )
-        }
-
-        // ── Section 4: Nostr Wallet Connect ───────────────────────────────────
+        // ── Section 3: Nostr Wallet Connect ───────────────────────────────────

        HorizontalDivider(
            modifier = Modifier.padding(vertical = 16.dp),
@@ -41,8 +41,6 @@ class UpdateZapAmountViewModel : ViewModel() {

    var nextAmount by mutableStateOf(TextFieldValue(""))
    var amountSet by mutableStateOf(listOf<Long>())
-    var nextOnchainAmount by mutableStateOf(TextFieldValue(""))
-    var onchainAmountSet by mutableStateOf(listOf<Long>())
    var walletConnectRelay by mutableStateOf(TextFieldValue(""))
    var walletConnectPubkey by mutableStateOf(TextFieldValue(""))
    var walletConnectSecret by mutableStateOf(TextFieldValue(""))
@@ -61,7 +59,6 @@ class UpdateZapAmountViewModel : ViewModel() {

    fun load() {
        this.amountSet = accountViewModel.account.settings.syncedSettings.zaps.zapAmountChoices.value
-        this.onchainAmountSet = accountViewModel.account.settings.syncedSettings.zaps.onchainZapAmountChoices.value
        this.selectedZapType = accountViewModel.account.settings.syncedSettings.zaps.defaultZapType.value

        val nip47 = accountViewModel.account.settings.defaultZapPaymentRequest()
@@ -86,19 +83,6 @@ class UpdateZapAmountViewModel : ViewModel() {
        amountSet = amountSet - amount
    }

-    fun addOnchainAmount() {
-        val newValue = nextOnchainAmount.text.trim().toLongOrNull()
-        if (newValue != null) {
-            onchainAmountSet = onchainAmountSet + newValue
-        }
-
-        nextOnchainAmount = TextFieldValue("")
-    }
-
-    fun removeOnchainAmount(amount: Long) {
-        onchainAmountSet = onchainAmountSet - amount
-    }
-
    fun sendPost() {
        accountViewModel.launchSigner {
            sendPostSuspend()
@@ -132,15 +116,13 @@ class UpdateZapAmountViewModel : ViewModel() {
                null
            }

-        accountViewModel.account.updateZapAmounts(amountSet, onchainAmountSet, selectedZapType, nip47Update)
+        accountViewModel.account.updateZapAmounts(amountSet, selectedZapType, nip47Update)

        nextAmount = TextFieldValue("")
-        nextOnchainAmount = TextFieldValue("")
    }

    fun cancel() {
        nextAmount = TextFieldValue("")
-        nextOnchainAmount = TextFieldValue("")
    }

    fun hasChanged(): Boolean {
@@ -148,7 +130,6 @@ class UpdateZapAmountViewModel : ViewModel() {
        return (
            selectedZapType != accountViewModel.account.settings.syncedSettings.zaps.defaultZapType.value ||
                amountSet != accountViewModel.account.settings.syncedSettings.zaps.zapAmountChoices.value ||
-                onchainAmountSet != accountViewModel.account.settings.syncedSettings.zaps.onchainZapAmountChoices.value ||
                walletConnectPubkey.text != (defaultUri?.pubKeyHex ?: "") ||
                walletConnectRelay.text != (defaultUri?.relayUri?.url ?: "") ||
                walletConnectSecret.text != (defaultUri?.secret ?: "")
@@ -1297,10 +1297,9 @@ class AccountViewModel(

    fun updateZapAmounts(
        amountSet: List<Long>,
-        onchainAmountSet: List<Long>,
        selectedZapType: LnZapEvent.ZapType,
        nip47Update: Nip47WalletConnect.Nip47URINorm?,
-    ) = launchSigner { account.updateZapAmounts(amountSet, onchainAmountSet, selectedZapType, nip47Update) }
+    ) = launchSigner { account.updateZapAmounts(amountSet, selectedZapType, nip47Update) }

    fun toggleDontTranslateFrom(languageCode: String) = launchSigner { account.toggleDontTranslateFrom(languageCode) }

@@ -74,6 +74,7 @@ import com.vitorpamplona.amethyst.commons.onchain.OnchainZapSendStage
 import com.vitorpamplona.amethyst.commons.onchain.OnchainZapShare
 import com.vitorpamplona.amethyst.commons.onchain.OnchainZapSplitter
 import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.model.MIN_ONCHAIN_ZAP_SATS
 import com.vitorpamplona.amethyst.model.User
 import com.vitorpamplona.amethyst.ui.components.namecoin.NamecoinResolutionRow
 import com.vitorpamplona.amethyst.ui.navigation.navs.EmptyNav
@@ -99,13 +100,6 @@ import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import java.text.NumberFormat

-// UX floor for onchain zaps. Below this any on-chain transaction is dominated
-// by miner fees — the recipient nets close to nothing even at low fee rates,
-// so quietly funneling the user to a Lightning zap is the friendlier outcome.
-// This is stricter than the protocol-level [OnchainZapBuilder.DUST_THRESHOLD_SATS]
-// (330 sats), which only guards against creating outputs the network rejects.
-private const val MIN_ONCHAIN_ZAP_SATS = 1_000L
-
 private enum class FeeTier(
    val label: String,
    val etaLabel: String,
@@ -213,8 +207,11 @@ fun OnchainZapSendDialog(
        }
    }

-    val presetAmounts by accountViewModel.account.settings.syncedSettings.zaps.onchainZapAmountChoices
+    // On-chain shares the single zap-amount list now; show only the entries
+    // that clear the on-chain minimum as quick presets.
+    val zapAmountChoices by accountViewModel.account.settings.syncedSettings.zaps.zapAmountChoices
        .collectAsStateWithLifecycle()
+    val presetAmounts = remember(zapAmountChoices) { zapAmountChoices.filter { it >= MIN_ONCHAIN_ZAP_SATS } }

    // Mirror the dropdown's NIP-05 / Namecoin (.bit) resolution so Send can
    // enable as soon as the typed name resolves, without forcing the user to
@@ -869,10 +869,7 @@
    <string name="wallet_connect_status_not_connected">Not connected</string>
    <string name="wallet_connect_manual_config">Advanced: enter connection details manually</string>
    <string name="quick_zap_amounts">Quick Zap Amounts</string>
-    <string name="quick_zap_amounts_explainer">Shown when pressing the zap button. Tap an amount to remove it. If you leave it empty, it will open the dialog to insert an amount every time.</string>
-    <string name="quick_zap_amounts_onchain">Quick On-chain Zap Amounts</string>
-    <string name="quick_zap_amounts_onchain_explainer">On-chain zaps pay miner fees, so amounts are usually larger than Lightning. Tap an amount to remove it.</string>
-    <string name="new_amount_in_sats_onchain">New on-chain amount in sats</string>
+    <string name="quick_zap_amounts_explainer">Shown when pressing the zap button. Each amount can be paid by any rail the recipient supports — Lightning, Cashu, or on-chain (on-chain only for larger amounts). Tap an amount to remove it. If you leave it empty, it will open the dialog to insert an amount every time.</string>
    <string name="send_onchain_instead">Send on-chain instead</string>
    <string name="zap_privacy_section">Zap Privacy</string>
    <string name="zap_type_section_explainer">Controls how your identity is shown when you send a zap.</string>
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.model
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+/**
+ * The on-chain rail's separate amount-preset list was folded into the single
+ * [AccountZapPreferencesInternal.zapAmountChoices]. These lock in that the
+ * migration union preserves amounts from both the legacy lists and round-trips
+ * idempotently (write the on-chain subset back, union it again → same set).
+ */
+class ZapAmountMergeTest {
+    private fun zaps(
+        zap: List<Long>,
+        onchain: List<Long>,
+    ) = AccountZapPreferencesInternal(zapAmountChoices = zap, onchainZapAmountChoices = onchain)
+
+    @Test
+    fun unionsDefaultsSortedAndDeduped() {
+        assertEquals(
+            listOf(21L, 50L, 100L, 5_000L),
+            mergeZapAmounts(zaps(DefaultZapAmounts, DefaultOnchainZapAmounts)),
+        )
+    }
+
+    @Test
+    fun preservesCustomAmountsFromBothLists() {
+        // Simulates a sync from an older client that still split the two lists.
+        assertEquals(
+            listOf(10L, 21L, 100L, 1_000L, 7_777L),
+            mergeZapAmounts(zaps(zap = listOf(21L, 100L, 10L), onchain = listOf(7_777L, 1_000L))),
+        )
+    }
+
+    @Test
+    fun dedupesAcrossLists() {
+        assertEquals(
+            listOf(100L, 5_000L),
+            mergeZapAmounts(zaps(zap = listOf(100L, 5_000L), onchain = listOf(5_000L))),
+        )
+    }
+
+    @Test
+    fun roundTripIsIdempotent() {
+        val merged = mergeZapAmounts(zaps(DefaultZapAmounts, DefaultOnchainZapAmounts))
+        // toInternal() writes the full list as zap and the on-chain-eligible
+        // subset as the legacy field; merging those again must not drift.
+        val onchainSubset = merged.filter { it >= MIN_ONCHAIN_ZAP_SATS }
+        assertEquals(merged, mergeZapAmounts(zaps(zap = merged, onchain = onchainSubset)))
+    }
+}