feat: implement NIP-87 ecash mint discoverability

Add protocol support and UI rendering for NIP-87 which defines ecash
mint discovery via three event kinds: MintRecommendationEvent (38000),
CashuMintEvent (38172), and FedimintEvent (38173).

https://claude.ai/code/session_01JR2nFVPjPGG9jTV4Qq2PUW

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/MintUrlTag.kt

@@ -0,0 +1,41 @@
+/*
+ * 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.quartz.nip87Ecash
+
+import com.vitorpamplona.quartz.nip01Core.core.has
+import com.vitorpamplona.quartz.utils.ensure
+
+class MintUrlTag {
+    companion object {
+        const val TAG_NAME = "u"
+
+        fun parse(tag: Array<String>): String? {
+            ensure(tag.has(1)) { return null }
+            ensure(tag[0] == TAG_NAME) { return null }
+            ensure(tag[1].isNotEmpty()) { return null }
+            return tag[1]
+        }
+
+        fun assemble(url: String) = arrayOf(TAG_NAME, url)
+
+        fun assemble(urls: List<String>) = urls.map { assemble(it) }
+    }
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/NetworkTag.kt

@@ -0,0 +1,53 @@
+/*
+ * 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.quartz.nip87Ecash
+
+import com.vitorpamplona.quartz.nip01Core.core.has
+import com.vitorpamplona.quartz.utils.ensure
+
+enum class NetworkType(
+    val code: String,
+) {
+    MAINNET("mainnet"),
+    TESTNET("testnet"),
+    SIGNET("signet"),
+    REGTEST("regtest"),
+    ;
+
+    companion object {
+        fun fromCode(code: String) = entries.firstOrNull { it.code == code }
+    }
+}
+
+class NetworkTag {
+    companion object {
+        const val TAG_NAME = "n"
+
+        fun parse(tag: Array<String>): NetworkType? {
+            ensure(tag.has(1)) { return null }
+            ensure(tag[0] == TAG_NAME) { return null }
+            ensure(tag[1].isNotEmpty()) { return null }
+            return NetworkType.fromCode(tag[1])
+        }
+
+        fun assemble(network: NetworkType) = arrayOf(TAG_NAME, network.code)
+    }
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/cashu/CashuMintEvent.kt

@@ -0,0 +1,70 @@
+/*
+ * 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.quartz.nip87Ecash.cashu
+
+import androidx.compose.runtime.Immutable
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.core.TagArrayBuilder
+import com.vitorpamplona.quartz.nip01Core.signers.eventTemplate
+import com.vitorpamplona.quartz.nip31Alts.alt
+import com.vitorpamplona.quartz.nip87Ecash.NetworkType
+import com.vitorpamplona.quartz.utils.TimeUtils
+
+@Immutable
+class CashuMintEvent(
+    id: HexKey,
+    pubKey: HexKey,
+    createdAt: Long,
+    tags: Array<Array<String>>,
+    content: String,
+    sig: HexKey,
+) : Event(id, pubKey, createdAt, KIND, tags, content, sig) {
+    fun mintUrl() = tags.mintUrl()
+
+    fun nuts() = tags.nuts()
+
+    fun network() = tags.network()
+
+    fun dTag() = tags.dTag()
+
+    companion object {
+        const val KIND = 38172
+        const val ALT_DESCRIPTION = "Cashu Mint Announcement"
+
+        fun build(
+            mintPubKey: String,
+            mintUrl: String,
+            nuts: List<String>,
+            network: NetworkType = NetworkType.MAINNET,
+            metadata: String = "",
+            createdAt: Long = TimeUtils.now(),
+            initializer: TagArrayBuilder<CashuMintEvent>.() -> Unit = {},
+        ) = eventTemplate(KIND, metadata, createdAt) {
+            alt(ALT_DESCRIPTION)
+            dTag(mintPubKey)
+            mintUrl(mintUrl)
+            nuts(nuts)
+            network(network)
+            initializer()
+        }
+    }
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/cashu/TagArrayBuilderExt.kt

@@ -0,0 +1,35 @@
+/*
+ * 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.quartz.nip87Ecash.cashu
+
+import com.vitorpamplona.quartz.nip01Core.core.TagArrayBuilder
+import com.vitorpamplona.quartz.nip87Ecash.MintUrlTag
+import com.vitorpamplona.quartz.nip87Ecash.NetworkTag
+import com.vitorpamplona.quartz.nip87Ecash.NetworkType
+import com.vitorpamplona.quartz.nip87Ecash.cashu.tags.NutsTag
+
+fun TagArrayBuilder<CashuMintEvent>.dTag(mintPubKey: String) = addUnique(arrayOf("d", mintPubKey))
+
+fun TagArrayBuilder<CashuMintEvent>.mintUrl(url: String) = addUnique(MintUrlTag.assemble(url))
+
+fun TagArrayBuilder<CashuMintEvent>.nuts(nuts: List<String>) = add(NutsTag.assemble(nuts))
+
+fun TagArrayBuilder<CashuMintEvent>.network(network: NetworkType) = addUnique(NetworkTag.assemble(network))

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/cashu/TagArrayExt.kt

@@ -0,0 +1,35 @@
+/*
+ * 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.quartz.nip87Ecash.cashu
+
+import com.vitorpamplona.quartz.nip01Core.core.TagArray
+import com.vitorpamplona.quartz.nip87Ecash.MintUrlTag
+import com.vitorpamplona.quartz.nip87Ecash.NetworkTag
+import com.vitorpamplona.quartz.nip87Ecash.NetworkType
+import com.vitorpamplona.quartz.nip87Ecash.cashu.tags.NutsTag
+
+fun TagArray.mintUrl(): String? = firstNotNullOfOrNull(MintUrlTag::parse)
+
+fun TagArray.nuts(): List<String> = firstNotNullOfOrNull(NutsTag::parse) ?: emptyList()
+
+fun TagArray.network(): NetworkType = firstNotNullOfOrNull(NetworkTag::parse) ?: NetworkType.MAINNET
+
+fun TagArray.dTag(): String? = firstOrNull { it.size >= 2 && it[0] == "d" }?.get(1)

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/cashu/tags/NutsTag.kt

@@ -0,0 +1,39 @@
+/*
+ * 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.quartz.nip87Ecash.cashu.tags
+
+import com.vitorpamplona.quartz.nip01Core.core.has
+import com.vitorpamplona.quartz.utils.ensure
+
+class NutsTag {
+    companion object {
+        const val TAG_NAME = "nuts"
+
+        fun parse(tag: Array<String>): List<String>? {
+            ensure(tag.has(1)) { return null }
+            ensure(tag[0] == TAG_NAME) { return null }
+            ensure(tag[1].isNotEmpty()) { return null }
+            return tag.drop(1)
+        }
+
+        fun assemble(nuts: List<String>) = arrayOf(TAG_NAME, *nuts.toTypedArray())
+    }
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/fedimint/FedimintEvent.kt

@@ -0,0 +1,70 @@
+/*
+ * 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.quartz.nip87Ecash.fedimint
+
+import androidx.compose.runtime.Immutable
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.core.TagArrayBuilder
+import com.vitorpamplona.quartz.nip01Core.signers.eventTemplate
+import com.vitorpamplona.quartz.nip31Alts.alt
+import com.vitorpamplona.quartz.nip87Ecash.NetworkType
+import com.vitorpamplona.quartz.utils.TimeUtils
+
+@Immutable
+class FedimintEvent(
+    id: HexKey,
+    pubKey: HexKey,
+    createdAt: Long,
+    tags: Array<Array<String>>,
+    content: String,
+    sig: HexKey,
+) : Event(id, pubKey, createdAt, KIND, tags, content, sig) {
+    fun inviteCodes() = tags.inviteCodes()
+
+    fun modules() = tags.modules()
+
+    fun network() = tags.network()
+
+    fun dTag() = tags.dTag()
+
+    companion object {
+        const val KIND = 38173
+        const val ALT_DESCRIPTION = "Fedimint Announcement"
+
+        fun build(
+            federationId: String,
+            inviteCodes: List<String>,
+            modules: List<String>,
+            network: NetworkType = NetworkType.MAINNET,
+            metadata: String = "",
+            createdAt: Long = TimeUtils.now(),
+            initializer: TagArrayBuilder<FedimintEvent>.() -> Unit = {},
+        ) = eventTemplate(KIND, metadata, createdAt) {
+            alt(ALT_DESCRIPTION)
+            dTag(federationId)
+            inviteCodes(inviteCodes)
+            modules(modules)
+            network(network)
+            initializer()
+        }
+    }
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/fedimint/TagArrayBuilderExt.kt

@@ -0,0 +1,35 @@
+/*
+ * 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.quartz.nip87Ecash.fedimint
+
+import com.vitorpamplona.quartz.nip01Core.core.TagArrayBuilder
+import com.vitorpamplona.quartz.nip87Ecash.MintUrlTag
+import com.vitorpamplona.quartz.nip87Ecash.NetworkTag
+import com.vitorpamplona.quartz.nip87Ecash.NetworkType
+import com.vitorpamplona.quartz.nip87Ecash.fedimint.tags.ModulesTag
+
+fun TagArrayBuilder<FedimintEvent>.dTag(federationId: String) = addUnique(arrayOf("d", federationId))
+
+fun TagArrayBuilder<FedimintEvent>.inviteCodes(codes: List<String>) = addAll(MintUrlTag.assemble(codes))
+
+fun TagArrayBuilder<FedimintEvent>.modules(modules: List<String>) = add(ModulesTag.assemble(modules))
+
+fun TagArrayBuilder<FedimintEvent>.network(network: NetworkType) = addUnique(NetworkTag.assemble(network))

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/fedimint/TagArrayExt.kt

@@ -0,0 +1,35 @@
+/*
+ * 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.quartz.nip87Ecash.fedimint
+
+import com.vitorpamplona.quartz.nip01Core.core.TagArray
+import com.vitorpamplona.quartz.nip87Ecash.MintUrlTag
+import com.vitorpamplona.quartz.nip87Ecash.NetworkTag
+import com.vitorpamplona.quartz.nip87Ecash.NetworkType
+import com.vitorpamplona.quartz.nip87Ecash.fedimint.tags.ModulesTag
+
+fun TagArray.inviteCodes(): List<String> = mapNotNull(MintUrlTag::parse)
+
+fun TagArray.modules(): List<String> = firstNotNullOfOrNull(ModulesTag::parse) ?: emptyList()
+
+fun TagArray.network(): NetworkType = firstNotNullOfOrNull(NetworkTag::parse) ?: NetworkType.MAINNET
+
+fun TagArray.dTag(): String? = firstOrNull { it.size >= 2 && it[0] == "d" }?.get(1)

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/fedimint/tags/ModulesTag.kt

@@ -0,0 +1,39 @@
+/*
+ * 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.quartz.nip87Ecash.fedimint.tags
+
+import com.vitorpamplona.quartz.nip01Core.core.has
+import com.vitorpamplona.quartz.utils.ensure
+
+class ModulesTag {
+    companion object {
+        const val TAG_NAME = "modules"
+
+        fun parse(tag: Array<String>): List<String>? {
+            ensure(tag.has(1)) { return null }
+            ensure(tag[0] == TAG_NAME) { return null }
+            ensure(tag[1].isNotEmpty()) { return null }
+            return tag.drop(1)
+        }
+
+        fun assemble(modules: List<String>) = arrayOf(TAG_NAME, *modules.toTypedArray())
+    }
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/recommendation/MintRecommendationEvent.kt

@@ -0,0 +1,78 @@
+/*
+ * 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.quartz.nip87Ecash.recommendation
+
+import androidx.compose.runtime.Immutable
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.core.TagArrayBuilder
+import com.vitorpamplona.quartz.nip01Core.signers.eventTemplate
+import com.vitorpamplona.quartz.nip31Alts.alt
+import com.vitorpamplona.quartz.nip87Ecash.cashu.CashuMintEvent
+import com.vitorpamplona.quartz.nip87Ecash.fedimint.FedimintEvent
+import com.vitorpamplona.quartz.utils.TimeUtils
+
+@Immutable
+class MintRecommendationEvent(
+    id: HexKey,
+    pubKey: HexKey,
+    createdAt: Long,
+    tags: Array<Array<String>>,
+    content: String,
+    sig: HexKey,
+) : Event(id, pubKey, createdAt, KIND, tags, content, sig) {
+    fun mintUrls() = tags.mintUrls()
+
+    fun mintEventKind() = tags.mintEventKind()
+
+    fun dTag() = tags.dTag()
+
+    fun mintEventAddresses() = tags.mintEventAddresses()
+
+    fun isCashuRecommendation() = mintEventKind() == CashuMintEvent.KIND
+
+    fun isFedimintRecommendation() = mintEventKind() == FedimintEvent.KIND
+
+    companion object {
+        const val KIND = 38000
+        const val ALT_DESCRIPTION = "Mint Recommendation"
+
+        fun build(
+            mintIdentifier: String,
+            mintKind: Int,
+            review: String = "",
+            mintUrls: List<String> = emptyList(),
+            mintEventAddress: String? = null,
+            mintEventRelay: String? = null,
+            createdAt: Long = TimeUtils.now(),
+            initializer: TagArrayBuilder<MintRecommendationEvent>.() -> Unit = {},
+        ) = eventTemplate(KIND, review, createdAt) {
+            alt(ALT_DESCRIPTION)
+            dTag(mintIdentifier)
+            kTag(mintKind)
+            mintUrls.forEach { mintUrl(it) }
+            if (mintEventAddress != null) {
+                aTag(mintEventAddress, mintEventRelay)
+            }
+            initializer()
+        }
+    }
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/recommendation/TagArrayBuilderExt.kt

@@ -0,0 +1,39 @@
+/*
+ * 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.quartz.nip87Ecash.recommendation
+
+import com.vitorpamplona.quartz.nip01Core.core.TagArrayBuilder
+import com.vitorpamplona.quartz.nip87Ecash.MintUrlTag
+
+fun TagArrayBuilder<MintRecommendationEvent>.dTag(mintIdentifier: String) = addUnique(arrayOf("d", mintIdentifier))
+
+fun TagArrayBuilder<MintRecommendationEvent>.kTag(kind: Int) = addUnique(arrayOf("k", kind.toString()))
+
+fun TagArrayBuilder<MintRecommendationEvent>.mintUrl(url: String) = add(MintUrlTag.assemble(url))
+
+fun TagArrayBuilder<MintRecommendationEvent>.aTag(
+    address: String,
+    relay: String? = null,
+) = if (relay != null) {
+    add(arrayOf("a", address, relay))
+} else {
+    add(arrayOf("a", address))
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip87Ecash/recommendation/TagArrayExt.kt

@@ -0,0 +1,32 @@
+/*
+ * 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.quartz.nip87Ecash.recommendation
+
+import com.vitorpamplona.quartz.nip01Core.core.TagArray
+import com.vitorpamplona.quartz.nip87Ecash.MintUrlTag
+
+fun TagArray.mintUrls(): List<String> = mapNotNull(MintUrlTag::parse)
+
+fun TagArray.mintEventKind(): Int? = firstOrNull { it.size >= 2 && it[0] == "k" }?.get(1)?.toIntOrNull()
+
+fun TagArray.dTag(): String? = firstOrNull { it.size >= 2 && it[0] == "d" }?.get(1)
+
+fun TagArray.mintEventAddresses(): List<String> = filter { it.size >= 2 && it[0] == "a" }.map { it[1] }

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/utils/EventFactory.kt

@@ -160,6 +160,9 @@ import com.vitorpamplona.quartz.nip85TrustedAssertions.events.EventAssertionEven
 import com.vitorpamplona.quartz.nip85TrustedAssertions.externalIds.ExternalIdAssertionEvent
 import com.vitorpamplona.quartz.nip85TrustedAssertions.list.TrustProviderListEvent
 import com.vitorpamplona.quartz.nip85TrustedAssertions.users.ContactCardEvent
+import com.vitorpamplona.quartz.nip87Ecash.cashu.CashuMintEvent
+import com.vitorpamplona.quartz.nip87Ecash.fedimint.FedimintEvent
+import com.vitorpamplona.quartz.nip87Ecash.recommendation.MintRecommendationEvent
 import com.vitorpamplona.quartz.nip88Polls.poll.PollEvent
 import com.vitorpamplona.quartz.nip88Polls.response.PollResponseEvent
 import com.vitorpamplona.quartz.nip89AppHandlers.definition.AppDefinitionEvent
@@ -228,6 +231,7 @@ class EventFactory {
                 CalendarEvent.KIND -> CalendarEvent(id, pubKey, createdAt, tags, content, sig)
                 CalendarTimeSlotEvent.KIND -> CalendarTimeSlotEvent(id, pubKey, createdAt, tags, content, sig)
                 CalendarRSVPEvent.KIND -> CalendarRSVPEvent(id, pubKey, createdAt, tags, content, sig)
+                CashuMintEvent.KIND -> CashuMintEvent(id, pubKey, createdAt, tags, content, sig)
                 CashuMintQuoteEvent.KIND -> CashuMintQuoteEvent(id, pubKey, createdAt, tags, content, sig)
                 CashuTokenEvent.KIND -> CashuTokenEvent(id, pubKey, createdAt, tags, content, sig)
                 CashuSpendingHistoryEvent.KIND -> CashuSpendingHistoryEvent(id, pubKey, createdAt, tags, content, sig)
@@ -263,6 +267,7 @@ class EventFactory {
                 EphemeralChatEvent.KIND -> EphemeralChatEvent(id, pubKey, createdAt, tags, content, sig)
                 EphemeralChatListEvent.KIND -> EphemeralChatListEvent(id, pubKey, createdAt, tags, content, sig)
                 ExternalIdentitiesEvent.KIND -> ExternalIdentitiesEvent(id, pubKey, createdAt, tags, content, sig)
+                FedimintEvent.KIND -> FedimintEvent(id, pubKey, createdAt, tags, content, sig)
                 FileHeaderEvent.KIND -> FileHeaderEvent(id, pubKey, createdAt, tags, content, sig)
                 ProfileGalleryEntryEvent.KIND -> ProfileGalleryEntryEvent(id, pubKey, createdAt, tags, content, sig)
                 FileServersEvent.KIND -> FileServersEvent(id, pubKey, createdAt, tags, content, sig)
@@ -301,6 +306,7 @@ class EventFactory {
                 MeetingRoomEvent.KIND -> MeetingRoomEvent(id, pubKey, createdAt, tags, content, sig)
                 MeetingRoomPresenceEvent.KIND -> MeetingRoomPresenceEvent(id, pubKey, createdAt, tags, content, sig)
                 MeetingSpaceEvent.KIND -> MeetingSpaceEvent(id, pubKey, createdAt, tags, content, sig)
+                MintRecommendationEvent.KIND -> MintRecommendationEvent(id, pubKey, createdAt, tags, content, sig)
                 MetadataEvent.KIND -> MetadataEvent(id, pubKey, createdAt, tags, content, sig)
                 MuteListEvent.KIND -> MuteListEvent(id, pubKey, createdAt, tags, content, sig)
                 NNSEvent.KIND -> NNSEvent(id, pubKey, createdAt, tags, content, sig)