diff --git a/libquassel-protocol/src/main/kotlin/de/justjanne/libquassel/protocol/util/ParsingContext.kt b/libquassel-protocol/src/main/kotlin/de/justjanne/libquassel/protocol/util/ParsingContext.kt
new file mode 100644
index 0000000000000000000000000000000000000000..9531f839ded60be5c494b379c39abe357703c1a4
--- /dev/null
+++ b/libquassel-protocol/src/main/kotlin/de/justjanne/libquassel/protocol/util/ParsingContext.kt
@@ -0,0 +1,66 @@
+/*
+ * libquassel
+ * Copyright (c) 2021 Janne Mareike Koschinski
+ * Copyright (c) 2021 The Quassel Project
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public License,
+ * v. 2.0. If a copy of the MPL was not distributed with this file, You can
+ * obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package de.justjanne.libquassel.protocol.util
+
+import de.justjanne.libquassel.annotations.Generated
+import de.justjanne.libquassel.protocol.util.expansion.Expansion
+import java.util.function.Supplier
+
+internal abstract class ParsingContext<T>(
+ internal val text: String
+) {
+ protected abstract val matchers: List<Supplier<T?>>
+
+ internal var position = 0
+
+ fun parse(): List<T> {
+ val result = mutableListOf<T>()
+ while (position < text.length) {
+ for (matcher in matchers) {
+ val match = matcher.get()
+ if (match != null) {
+ result.add(match)
+ continue
+ }
+ }
+ }
+ return result
+ }
+
+ @Generated
+ protected inline fun match(
+ vararg patterns: String,
+ crossinline function: () -> Expansion
+ ) = Supplier {
+ for (pattern in patterns) {
+ if (text.startsWith(pattern, startIndex = position)) {
+ position += pattern.length
+ return@Supplier function()
+ }
+ }
+ return@Supplier null
+ }
+
+ @Generated
+ protected inline fun match(
+ vararg patterns: Regex,
+ crossinline function: (List<String>) -> Expansion
+ ) = Supplier {
+ for (pattern in patterns) {
+ val match = pattern.find(text, startIndex = position)
+ if (match != null && match.range.first == position) {
+ position = match.range.last + 1
+ return@Supplier function(match.groupValues)
+ }
+ }
+ return@Supplier null
+ }
+}
diff --git a/libquassel-protocol/src/main/kotlin/de/justjanne/libquassel/protocol/util/expansion/Expansion.kt b/libquassel-protocol/src/main/kotlin/de/justjanne/libquassel/protocol/util/expansion/Expansion.kt
new file mode 100644
index 0000000000000000000000000000000000000000..93da3d9035c2afa957823ee5f8a09dbb65974474
--- /dev/null
+++ b/libquassel-protocol/src/main/kotlin/de/justjanne/libquassel/protocol/util/expansion/Expansion.kt
@@ -0,0 +1,36 @@
+/*
+ * libquassel
+ * Copyright (c) 2021 Janne Mareike Koschinski
+ * Copyright (c) 2021 The Quassel Project
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public License,
+ * v. 2.0. If a copy of the MPL was not distributed with this file, You can
+ * obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package de.justjanne.libquassel.protocol.util.expansion
+
+sealed class Expansion {
+ data class Text(val value: String) : Expansion()
+ data class ParameterRange(val from: Int, val to: Int?) : Expansion()
+ data class Parameter(val index: Int, val field: ParameterField?) : Expansion()
+ data class Constant(val field: ConstantField) : Expansion()
+
+ enum class ParameterField {
+ HOSTNAME,
+ VERIFIED_IDENT,
+ IDENT,
+ ACCOUNT
+ }
+
+ enum class ConstantField {
+ CHANNEL,
+ NICK,
+ NETWORK
+ }
+
+ companion object {
+ fun parse(text: String): List<Expansion> =
+ ExpansionParsingContext(text).parse()
+ }
+}
diff --git a/libquassel-protocol/src/main/kotlin/de/justjanne/libquassel/protocol/util/expansion/ExpansionParsingContext.kt b/libquassel-protocol/src/main/kotlin/de/justjanne/libquassel/protocol/util/expansion/ExpansionParsingContext.kt
new file mode 100644
index 0000000000000000000000000000000000000000..566e2df1362548c2bd5f08d4432456b13d73bc87
--- /dev/null
+++ b/libquassel-protocol/src/main/kotlin/de/justjanne/libquassel/protocol/util/expansion/ExpansionParsingContext.kt
@@ -0,0 +1,67 @@
+/*
+ * libquassel
+ * Copyright (c) 2021 Janne Mareike Koschinski
+ * Copyright (c) 2021 The Quassel Project
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public License,
+ * v. 2.0. If a copy of the MPL was not distributed with this file, You can
+ * obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package de.justjanne.libquassel.protocol.util.expansion
+
+import de.justjanne.libquassel.protocol.util.ParsingContext
+import java.util.function.Supplier
+
+internal class ExpansionParsingContext(
+ text: String
+) : ParsingContext<Expansion>(text) {
+ override val matchers: List<Supplier<Expansion?>> = listOf(
+ match("\$channelname", "\$channel") {
+ Expansion.Constant(Expansion.ConstantField.CHANNEL)
+ },
+ match("\$currentnick", "\$nick") {
+ Expansion.Constant(Expansion.ConstantField.NICK)
+ },
+ match("\$network") {
+ Expansion.Constant(Expansion.ConstantField.NETWORK)
+ },
+ match("\$0") {
+ Expansion.Parameter(0, null)
+ },
+ match("""\$(\d+)\.\.(\d+)""".toRegex()) { (_, from, to) ->
+ Expansion.ParameterRange(from.toInt(), to.toInt())
+ },
+ match("""\$(\d+)\.\.""".toRegex()) { (_, from) ->
+ Expansion.ParameterRange(from.toInt(), null)
+ },
+ match("""\$(\d+):hostname""".toRegex()) { (_, value) ->
+ Expansion.Parameter(value.toInt(), Expansion.ParameterField.HOSTNAME)
+ },
+ match("""\$(\d+):identd""".toRegex()) { (_, value) ->
+ Expansion.Parameter(value.toInt(), Expansion.ParameterField.VERIFIED_IDENT)
+ },
+ match("""\$(\d+):ident""".toRegex()) { (_, value) ->
+ Expansion.Parameter(value.toInt(), Expansion.ParameterField.IDENT)
+ },
+ match("""\$(\d+):account""".toRegex()) { (_, value) ->
+ Expansion.Parameter(value.toInt(), Expansion.ParameterField.ACCOUNT)
+ },
+ match("""\$(\d+)""".toRegex()) { (_, value) ->
+ Expansion.Parameter(value.toInt(), null)
+ },
+ Supplier {
+ val end = text.indexOf('$', startIndex = position).let {
+ if (it >= 0) it
+ else text.length
+ }
+ if (position < end) {
+ val start = position
+ position = end
+ val value = text.substring(start, end)
+ return@Supplier Expansion.Text(value)
+ }
+ return@Supplier null
+ }
+ )
+}
diff --git a/libquassel-protocol/src/test/kotlin/de/justjanne/libquassel/protocol/util/expansion/ExpansionTest.kt b/libquassel-protocol/src/test/kotlin/de/justjanne/libquassel/protocol/util/expansion/ExpansionTest.kt
new file mode 100644
index 0000000000000000000000000000000000000000..02290613c6e94d40d9ec754934e4b81e4363504d
--- /dev/null
+++ b/libquassel-protocol/src/test/kotlin/de/justjanne/libquassel/protocol/util/expansion/ExpansionTest.kt
@@ -0,0 +1,106 @@
+/*
+ * libquassel
+ * Copyright (c) 2021 Janne Mareike Koschinski
+ * Copyright (c) 2021 The Quassel Project
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public License,
+ * v. 2.0. If a copy of the MPL was not distributed with this file, You can
+ * obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package de.justjanne.libquassel.protocol.util.expansion
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+
+class ExpansionTest {
+ @Test
+ fun testDefaults() {
+ assertEquals(
+ listOf(
+ Expansion.Text("/join "),
+ Expansion.Parameter(0, null)
+ ),
+ Expansion.parse("/join $0")
+ )
+
+ assertEquals(
+ listOf(
+ Expansion.Text("/whois "),
+ Expansion.Parameter(0, null),
+ Expansion.Text(" "),
+ Expansion.Parameter(0, null)
+ ),
+ Expansion.parse("/whois $0 $0")
+ )
+ }
+
+ @Test
+ fun testParameters() {
+ assertEquals(
+ listOf(
+ Expansion.Text("/say Welcome to the support channel for the IRC client Quassel, "),
+ Expansion.Parameter(1, null)
+ ),
+ Expansion.parse("/say Welcome to the support channel for the IRC client Quassel, \$1")
+ )
+ assertEquals(
+ listOf(
+ Expansion.Parameter(1, null),
+ Expansion.Text(" "),
+ Expansion.Parameter(1, Expansion.ParameterField.ACCOUNT),
+ Expansion.Text(" "),
+ Expansion.Parameter(1, Expansion.ParameterField.HOSTNAME),
+ Expansion.Text(" "),
+ Expansion.Parameter(1, Expansion.ParameterField.VERIFIED_IDENT),
+ Expansion.Text(" "),
+ Expansion.Parameter(1, Expansion.ParameterField.IDENT),
+ ),
+ Expansion.parse("\$1 \$1:account \$1:hostname \$1:identd \$1:ident")
+ )
+ }
+
+ @Test
+ fun testConstants() {
+ assertEquals(
+ listOf(
+ Expansion.Text("/say I am "),
+ Expansion.Constant(Expansion.ConstantField.NICK),
+ Expansion.Text(", welcoming you to our channel "),
+ Expansion.Constant(Expansion.ConstantField.CHANNEL),
+ Expansion.Text(" on "),
+ Expansion.Constant(Expansion.ConstantField.NETWORK),
+ Expansion.Text(".")
+ ),
+ Expansion.parse("/say I am \$nick, welcoming you to our channel \$channelname on \$network.")
+ )
+ assertEquals(
+ listOf(
+ Expansion.Text("/say That’s right, I’m /the/ "),
+ Expansion.Constant(Expansion.ConstantField.NICK),
+ Expansion.Text(" from "),
+ Expansion.Constant(Expansion.ConstantField.CHANNEL),
+ Expansion.Text(".")
+ ),
+ Expansion.parse("/say That’s right, I’m /the/ \$nick from \$channel.")
+ )
+ }
+
+ @Test
+ fun testRanges() {
+ assertEquals(
+ listOf(
+ Expansion.Text("1 \""),
+ Expansion.Parameter(1, null),
+ Expansion.Text("\" 2 \""),
+ Expansion.Parameter(2, null),
+ Expansion.Text("\" 3..4 \""),
+ Expansion.ParameterRange(3, 4),
+ Expansion.Text("\" 3.. \""),
+ Expansion.ParameterRange(3, null),
+ Expansion.Text("\""),
+ ),
+ Expansion.parse("1 \"\$1\" 2 \"\$2\" 3..4 \"\$3..4\" 3.. \"\$3..\"")
+ )
+ }
+}