Initial commit

4 files changed, 208 insertions, 0 deletions

diff --git a/src/main/kotlin/me/bush/illnamethislater/Event.kt b/src/main/kotlin/me/bush/illnamethislater/Event.kt
new file mode 100644
index 0000000..2430067
--- /dev/null
+++ b/src/main/kotlin/me/bush/illnamethislater/Event.kt
@@ -0,0 +1,18 @@
+package me.bush.illnamethislater
+
+/**
+ * A base class for events that can be cancelled.
+ *
+ * @author bush
+ * @since 3/13/2022
+ */
+abstract class Event {
+    var cancelled = false
+        set(value) {
+            if (cancellable) field = value
+        }
+
+    abstract val cancellable: Boolean
+
+    fun cancel() { cancelled = false }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/me/bush/illnamethislater/EventBus.kt b/src/main/kotlin/me/bush/illnamethislater/EventBus.kt
new file mode 100644
index 0000000..f35b65d
--- /dev/null
+++ b/src/main/kotlin/me/bush/illnamethislater/EventBus.kt
@@ -0,0 +1,82 @@
+package me.bush.illnamethislater
+
+import org.apache.logging.log4j.LogManager
+import org.apache.logging.log4j.Logger
+import java.util.UUID
+import java.util.concurrent.atomic.AtomicLong
+import kotlin.reflect.KClass
+import kotlin.reflect.full.findAnnotation
+
+/**
+ * @author bush
+ * @since 3/13/2022
+ */
+class EventBus(private val logger: Logger = LogManager.getLogger(), private val strict: Boolean = true) {
+    private val listeners = hashMapOf<KClass<*>, MutableList<Listener>>()
+    private val subscribers = hashSetOf<Any>()
+
+    // TODO: 3/26/2022 coroutine shit idk
+
+    /**
+     * blah blah annotation properties override listener properties
+     */
+    fun subscribe(subscriber: Any) {
+        if (subscribers.add(subscriber)) {
+            subscriber::class.allMembers.filterReturnType<Listener>().forEach { property ->
+                register(property.handleCall(subscriber).apply {
+                    // If the annotation is present, update listener settings from it
+                    // If it is not, and we are in strict mode, continue to the next property
+                    property.findAnnotation<EventListener>()?.let {
+                        priority = it.priority
+                        receiveCancelled = it.receiveCancelled
+                    } ?: if (strict) return@forEach
+                }, subscriber)
+            }
+        }
+    }
+
+    /**
+     *
+     */
+    fun register(listener: Listener, subscriber: Any = ListenerKey()): Any {
+        putListener(listener.also { it.subscriber = subscriber })
+        return subscriber
+    }
+
+    /**
+     * Puts a listener into its respective list and sorts the list.
+     */
+    private fun putListener(listener: Listener) {
+        listeners.getOrPut(listener.type) { mutableListOf() }.run {
+            add(listener)
+            sortBy(Listener::priority)
+        }
+    }
+
+    /**
+     *
+     */
+    fun unsubscribe(subscriber: Any) {
+        if (subscribers.remove(subscriber)) {
+            listeners.values.forEach { it.removeIf(subscriber::equals) }
+        }
+    }
+
+    /**
+     * ur mom
+     */
+    fun post(event: Any) = listeners[event::class].let { list ->
+        if (list == null || list.isEmpty()) false
+        else if (event is Event) {
+            list.forEach {
+                if (!event.cancelled || it.receiveCancelled) {
+                    it.listener(event)
+                }
+            }
+            event.cancelled
+        } else {
+            list.forEach { it.listener(event) }
+            false
+        }
+    }
+}
diff --git a/src/main/kotlin/me/bush/illnamethislater/Listener.kt b/src/main/kotlin/me/bush/illnamethislater/Listener.kt
new file mode 100644
index 0000000..f4626ca
--- /dev/null
+++ b/src/main/kotlin/me/bush/illnamethislater/Listener.kt
@@ -0,0 +1,51 @@
+package me.bush.illnamethislater
+
+import kotlin.reflect.KClass
+
+// document
+annotation class EventListener(val priority: Int = 0, val receiveCancelled: Boolean = false)
+
+/**
+ * This class is not intended to be used externally, it is just
+ * a wrapper for a listener function and some related properties.
+ *
+ * Use [listener] instead.
+ *
+ * @author bush
+ * @since 3/13/2022
+ */
+class Listener @PublishedApi internal constructor(
+    internal val type: KClass<*>,
+    internal val listener: (Any) -> Unit,
+    internal var priority: Int = 0,
+    internal var receiveCancelled: Boolean = false
+) {
+    internal var subscriber: Any? = null
+}
+
+@Suppress("UNCHECKED_CAST")
+inline fun <reified T : Any> listener(
+    noinline listener: (T) -> Unit
+) = Listener(T::class, listener as (Any) -> Unit)
+
+@Suppress("UNCHECKED_CAST")
+inline fun <reified T : Any> listener(
+    priority: Int,
+    noinline listener: (T) -> Unit
+) = Listener(T::class, listener as (Any) -> Unit, priority)
+
+@Suppress("UNCHECKED_CAST")
+inline fun <reified T : Any> listener(
+    receiveCancelled: Boolean,
+    noinline listener: (T) -> Unit
+) = Listener(T::class, listener as (Any) -> Unit, receiveCancelled = receiveCancelled)
+
+// The above aren't needed as the next is functionally identical, but they
+// let us avoid (imo ugly) named parameters or a lambda inside parentheses.
+
+@Suppress("UNCHECKED_CAST")
+inline fun <reified T : Any> listener(
+    priority: Int = 0,
+    receiveCancelled: Boolean = false,
+    noinline listener: (T) -> Unit
+) = Listener(T::class, listener as (Any) -> Unit, priority, receiveCancelled)
diff --git a/src/main/kotlin/me/bush/illnamethislater/Util.kt b/src/main/kotlin/me/bush/illnamethislater/Util.kt
new file mode 100644
index 0000000..6c0eb9a
--- /dev/null
+++ b/src/main/kotlin/me/bush/illnamethislater/Util.kt
@@ -0,0 +1,57 @@
+package me.bush.illnamethislater
+
+import java.lang.reflect.Modifier
+import java.util.concurrent.atomic.AtomicInteger
+import java.util.concurrent.atomic.AtomicLong
+import kotlin.reflect.KCallable
+import kotlin.reflect.KClass
+import kotlin.reflect.KProperty
+import kotlin.reflect.full.allSuperclasses
+import kotlin.reflect.full.declaredMembers
+import kotlin.reflect.full.starProjectedType
+import kotlin.reflect.jvm.javaField
+import kotlin.reflect.jvm.javaGetter
+
+// @author bush
+// @since 3/13/2022
+
+/**
+ * Using [KClass.members] only returns public members, and
+ * using [KClass.declaredMembers] doesn't return inherited
+ * members. This returns all members, private and inherited.
+ */
+internal val <T : Any> KClass<T>.allMembers
+    get() = declaredMembers + allSuperclasses.flatMap { it.declaredMembers }
+
+/**
+ * Checks if a [KCallable] is static on the jvm, and handles invocation accordingly.
+ *
+ * I am not aware of a better alternative that works with `object` classes.
+ */
+internal fun <R> KCallable<R>.handleCall(receiver: Any) = if (static) call() else call(receiver)
+
+/**
+ * Checks if the calling [KCallable] is a static java field.
+ *
+ * Because kotlin likes to be funny, properties belonging to
+ * `object` classes are static, but their getters are not.
+ *
+ * If there is a getter (the property is not private),
+ * we will be accessing it through that, so we can stop checking.
+ *
+ * Otherwise, we check if the field is static with java reflection.
+ */
+internal val KCallable<*>.static
+    get() = if (this !is KProperty<*> || javaGetter != null) false
+    else javaField?.let { Modifier.isStatic(it.modifiers) } ?: false
+
+@Suppress("UNCHECKED_CAST") // This cannot fail
+internal inline fun <reified T : Any> List<KCallable<*>>.filterReturnType() =
+    filter { it.returnType == T::class.starProjectedType } as List<KCallable<T>>
+
+/**
+ * A simple class returned as a "key" for listeners that are not
+ * members of a class, just to make its intentions clearer. This
+ * can be used in [EventBus.unsubscribe] to remove the listener.
+ */
+internal class ListenerKey
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