2 files changed, 128 insertions, 0 deletions
diff --git a/symbols/src/main/kotlin/Subscribe.kt b/symbols/src/main/kotlin/Subscribe.kt
new file mode 100644
index 0000000..e7a7bf4
--- /dev/null
+++ b/symbols/src/main/kotlin/Subscribe.kt
@@ -0,0 +1,12 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Linnea Gräf <nea@nea.moe>
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package moe.nea.firmament.annotations
+
+@Target(AnnotationTarget.FUNCTION)
+@Retention(AnnotationRetention.SOURCE)
+annotation class Subscribe
+
diff --git a/symbols/src/main/kotlin/process/SubscribeAnnotationProcessor.kt b/symbols/src/main/kotlin/process/SubscribeAnnotationProcessor.kt
new file mode 100644
index 0000000..be817ce
--- /dev/null
+++ b/symbols/src/main/kotlin/process/SubscribeAnnotationProcessor.kt
@@ -0,0 +1,116 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Linnea Gräf <nea@nea.moe>
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package moe.nea.firmament.annotations.process
+
+import com.google.auto.service.AutoService
+import com.google.devtools.ksp.processing.CodeGenerator
+import com.google.devtools.ksp.processing.Dependencies
+import com.google.devtools.ksp.processing.KSPLogger
+import com.google.devtools.ksp.processing.Resolver
+import com.google.devtools.ksp.processing.SymbolProcessor
+import com.google.devtools.ksp.processing.SymbolProcessorEnvironment
+import com.google.devtools.ksp.processing.SymbolProcessorProvider
+import com.google.devtools.ksp.symbol.ClassKind
+import com.google.devtools.ksp.symbol.KSAnnotated
+import com.google.devtools.ksp.symbol.KSClassDeclaration
+import com.google.devtools.ksp.symbol.KSFunctionDeclaration
+import com.google.devtools.ksp.symbol.KSType
+import com.google.devtools.ksp.symbol.Nullability
+import com.google.devtools.ksp.validate
+import java.text.SimpleDateFormat
+import java.util.Date
+import moe.nea.firmament.annotations.Subscribe
+
+class SubscribeAnnotationProcessor(
+    val logger: KSPLogger,
+    val codeGenerator: CodeGenerator,
+) : SymbolProcessor {
+    override fun finish() {
+        val dependencies = Dependencies(
+            aggregating = true,
+            *subscriptions.mapTo(mutableSetOf()) { it.parent.containingFile!! }.toTypedArray())
+        val subscriptionsFile =
+            codeGenerator
+                .createNewFile(dependencies, "moe.nea.firmament.annotations.generated", "AllSubscriptions")
+                .bufferedWriter()
+        subscriptionsFile.apply {
+            appendLine("// This file is @generated by SubscribeAnnotationProcessor at ${SimpleDateFormat("yyyy-MM-dd HH:mm:ss z").format(
+                Date())}")
+            appendLine("// Do not edit")
+            appendLine("package moe.nea.firmament.annotations.generated")
+            appendLine()
+            appendLine("import moe.nea.firmament.events.subscription.*")
+            appendLine()
+            appendLine("object AllSubscriptions {")
+            appendLine("  fun provideSubscriptions(addSubscription: (Subscription<*>) -> Unit) {")
+            for (subscription in subscriptions) {
+                val owner = subscription.parent.qualifiedName!!.asString()
+                val method = subscription.child.simpleName.asString()
+                val type = subscription.type.declaration.qualifiedName!!.asString()
+                appendLine("    addSubscription(Subscription<$type>(")
+                appendLine("        ${owner},")
+                appendLine("        ${owner}::${method},")
+                appendLine("        ${type}))")
+            }
+            appendLine("  }")
+            appendLine("}")
+        }
+        subscriptionsFile.close()
+    }
+
+    data class Subscription(
+        val parent: KSClassDeclaration,
+        val child: KSFunctionDeclaration,
+        val type: KSType,
+    )
+
+    val subscriptions = mutableListOf<Subscription>()
+
+    fun processCandidates(list: List<KSAnnotated>) {
+        for (element in list) {
+            if (element !is KSFunctionDeclaration) {
+                logger.error("@Subscribe annotation on a not-function", element)
+                continue
+            }
+            if (element.isAbstract) {
+                logger.error("@Subscribe annotation on an abstract function", element)
+                continue
+            }
+            val parent = element.parentDeclaration
+            if (parent !is KSClassDeclaration || parent.isCompanionObject || parent.classKind != ClassKind.OBJECT) {
+                logger.error("@Subscribe on a non-object", element)
+                continue
+            }
+            val param = element.parameters.singleOrNull()
+            if (param == null) {
+                logger.error("@Subscribe annotated functions need to take exactly one parameter", element)
+                continue
+            }
+            val type = param.type.resolve()
+            if (type.nullability != Nullability.NOT_NULL) {
+                logger.error("@Subscribe annotated functions cannot take a nullable event", element)
+                continue
+            }
+            subscriptions.add(Subscription(parent, element, type))
+        }
+    }
+
+    override fun process(resolver: Resolver): List<KSAnnotated> {
+        val candidates = resolver.getSymbolsWithAnnotation(Subscribe::class.qualifiedName!!).toList()
+        val valid = candidates.filter { it.validate() }
+        val invalid = candidates.filter { !it.validate() }
+        processCandidates(valid)
+        return invalid
+    }
+}
+
+@AutoService(SymbolProcessorProvider::class)
+class SubscribeAnnotationProcessorProvider : SymbolProcessorProvider {
+    override fun create(environment: SymbolProcessorEnvironment): SymbolProcessor {
+        return SubscribeAnnotationProcessor(environment.logger, environment.codeGenerator)
+    }
+}