Rewrite attack and damage events

Author: Yeregorix

src/main/java/org/spongepowered/api/event/cause/entity/damage/DamageFunction.java

@@ -24,255 +24,18 @@
  */
 package org.spongepowered.api.event.cause.entity.damage;
 
-import org.checkerframework.checker.nullness.qual.Nullable;
-import org.spongepowered.api.entity.Entity;
-import org.spongepowered.api.event.Cause;
-import org.spongepowered.api.item.ItemTypes;
-import org.spongepowered.api.item.enchantment.Enchantment;
-import org.spongepowered.api.item.inventory.ItemStack;
-import org.spongepowered.api.item.inventory.ItemStackLike;
-import org.spongepowered.api.item.inventory.ItemStackSnapshot;
-import org.spongepowered.api.util.CopyableBuilder;
-
-import java.util.Objects;
-import java.util.Optional;
-import java.util.StringJoiner;
-import java.util.function.DoubleUnaryOperator;
-import java.util.function.Supplier;
-
 /**
- * Represents a modifier that will apply a function on a damage value to deal
- * towards an entity such that the raw damage is the input of a
- * {@link DoubleUnaryOperator} such that the output will be the final damage
- * applied to the {@link Entity}.
+ * A damage modifier that will be applied before or after a {@link DamageStep}.
  */
+@FunctionalInterface
 public interface DamageModifier {
 
     /**
-     * Creates a new {@link Builder} for constructing a {@link DamageModifier}.
-     *
-     * @return A new builder
-     */
-    static Builder builder() {
-        return new Builder();
-    }
-
-    /**
-     * Gets the {@link DamageModifierType} for this {@link DamageModifier}.
+     * Modifies the damage.
      *
-     * @return The damage modifier type
+     * @param step The damage step this modifier is associated with.
+     * @param damage The current damage value.
+     * @return The next damage value
      */
-    DamageModifierType type();
-
-    /**
-     * Returns the damage modifier group.
-     * <p>Grouped modifiers calculate their damage independently from each other</p>
-     *
-     * @return The damage modifier group
-     */
-    String group();
-
-    /**
-     * Gets the cause of this {@link DamageModifier}.
-     *
-     * @return The cause of this damage modifier
-     */
-    Cause cause();
-
-    /**
-     * Gets the contributing {@link ItemStackSnapshot} that provided the
-     * "reason" for this {@link DamageModifier} to exist. An example of a
-     * contributing {@link ItemStack} is if an {@link ItemTypes#DIAMOND_SWORD}
-     * provided an {@link Enchantment} that provided a
-     * {@link DamageModifierTypes#WEAPON_ENCHANTMENT}, this modifier would have
-     * the {@link ItemStackSnapshot} for the weapon used. Some modifiers however,
-     * do not require an {@link ItemStack} to be the contributing factor for
-     * this modifier to exist.
-     *
-     * @return The contributing item, if available
-     */
-    Optional<ItemStackSnapshot> contributingItem();
-
-    /**
-     * A builder that creates {@link DamageModifier}s, for use in both plugin and
-     * implementation requirements.
-     */
-    final class Builder implements org.spongepowered.api.util.Builder<DamageModifier, Builder>, CopyableBuilder<DamageModifier, Builder> {
-
-        @Nullable DamageModifierType type;
-        @Nullable Cause cause;
-        @Nullable String group;
-        @Nullable ItemStackSnapshot snapshot;
-
-        Builder() {
-        }
-
-
-        /**
-         * Sets the {@link DamageModifierType} for the {@link DamageModifier} to
-         * build.
-         *
-         * @param damageModifierType The damage modifier type
-         * @return This builder, for chaining
-         */
-        public Builder type(final Supplier<? extends DamageModifierType> damageModifierType) {
-            return this.type(damageModifierType.get());
-        }
-
-        /**
-         * Sets the {@link DamageModifierType} for the {@link DamageModifier} to
-         * build.
-         *
-         * @param damageModifierType The damage modifier type
-         * @return This builder, for chaining
-         */
-        public Builder type(final DamageModifierType damageModifierType) {
-            this.type = java.util.Objects.requireNonNull(damageModifierType);
-            return this;
-        }
-
-        /**
-         * The main attack damage calculated for an {@link org.spongepowered.api.event.entity.AttackEntityEvent}
-         *
-         * @return This builder, for chaining
-         */
-        public Builder attackDamageGroup() {
-            return this.group("minecraft:attack_damage");
-        }
-
-        /**
-         * The enchantment attack damage calculated for an {@link org.spongepowered.api.event.entity.AttackEntityEvent}
-         *
-         * @return This builder, for chaining
-         */
-        public Builder attackEnchantmentGroup() {
-            return this.group("minecraft:attack_enchantment");
-        }
-
-        /**
-         * The damage calculated for an {@link org.spongepowered.api.event.entity.DamageEntityEvent}
-         *
-         * @return This builder, for chaining
-         */
-        public Builder damageReductionGroup() {
-            return this.group("minecraft:damage_reduction");
-        }
-
-        public Builder group(final String group) {
-            this.group = group;
-            return this;
-        }
-
-        public Builder item(final ItemStackLike item) {
-            this.snapshot = java.util.Objects.requireNonNull(item, "item").asImmutable();
-            return this;
-        }
-
-        /**
-         * Sets the {@link Cause} for the {@link DamageModifier} to build.
-         *
-         * @param cause The cause for the damage modifier
-         * @return This builder, for chaining
-         */
-        public Builder cause(final Cause cause) {
-            this.cause = java.util.Objects.requireNonNull(cause);
-            return this;
-        }
-
-        /**
-         * Creates a new {@link DamageModifier} with this builder's provided
-         * {@link Cause} and {@link DamageModifierType}.
-         *
-         * @return The newly created damage modifier
-         */
-        @Override
-        public DamageModifier build() {
-            if (this.type == null) {
-                throw new IllegalStateException("The DamageModifierType must not be null!");
-            }
-            if (this.cause == null) {
-                throw new IllegalStateException("The cause for the DamageModifier must not be null!");
-            }
-            return new ImplementedDamageModifier(this);
-        }
-
-        @Override
-        public Builder from(final DamageModifier value) {
-            this.type = value.type();
-            this.cause = value.cause();
-            this.snapshot = value.contributingItem().orElse(null);
-            return this;
-        }
-
-        @Override
-        public Builder reset() {
-            this.type = null;
-            this.cause = null;
-            return this;
-        }
-
-
-        private static class ImplementedDamageModifier implements DamageModifier {
-            private final DamageModifierType type;
-            private final Cause cause;
-            @Nullable private final ItemStackSnapshot snapshot;
-            private final String group;
-
-            ImplementedDamageModifier(final Builder builder) {
-                this.type = java.util.Objects.requireNonNull(builder.type, "DamageType is null!");
-                this.cause = java.util.Objects.requireNonNull(builder.cause, "Cause is null!");
-                this.group = java.util.Objects.requireNonNull(builder.group, "Group is null!");
-                this.snapshot = builder.snapshot;
-            }
-
-            @Override
-            public DamageModifierType type() {
-                return this.type;
-            }
-
-            @Override
-            public Cause cause() {
-                return this.cause;
-            }
-
-            @Override
-            public Optional<ItemStackSnapshot> contributingItem() {
-                return Optional.ofNullable(this.snapshot);
-            }
-
-            @Override
-            public String group() {
-                return group;
-            }
-
-            @Override
-            public int hashCode() {
-                return Objects.hash(this.type, this.cause);
-            }
-
-            @Override
-            public boolean equals(final Object obj) {
-                if (this == obj) {
-                    return true;
-                }
-                if (obj == null || this.getClass() != obj.getClass()) {
-                    return false;
-                }
-                final ImplementedDamageModifier other = (ImplementedDamageModifier) obj;
-                return Objects.equals(this.type, other.type)
-                       && Objects.equals(this.cause, other.cause)
-                       && Objects.equals(this.snapshot, other.snapshot);
-            }
-
-            @Override
-            public String toString() {
-                return new StringJoiner(", ", "DamageModifier[", "]")
-                    .add("type=" + this.type)
-                    .add("cause=" + this.cause)
-                    .add("snapshot=" + this.snapshot)
-                    .toString();
-            }
-        }
-
-    }
+    double modify(DamageStep step, double damage);
 }