From a202c47c65d130b5f32c9ed0a5483d67eebda45b Mon Sep 17 00:00:00 2001
From: Andrea Cavalli <andrea@cavallium.it>
Date: Wed, 9 Feb 2022 21:06:02 +0100
Subject: [PATCH] Optimize entities cache

---
 .../meta/MemoizedUTF16String.java             | 38 +++++++++++++++++++
 .../meta/MemoizedUTF16Substring.java          | 35 +++++++++++++++++
 .../meta/api/objects/MessageEntity.java       | 25 +++++++-----
 3 files changed, 88 insertions(+), 10 deletions(-)
 create mode 100644 telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/MemoizedUTF16String.java
 create mode 100644 telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/MemoizedUTF16Substring.java

diff --git a/telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/MemoizedUTF16String.java b/telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/MemoizedUTF16String.java
new file mode 100644
index 00000000..291807f5
--- /dev/null
+++ b/telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/MemoizedUTF16String.java
@@ -0,0 +1,38 @@
+package org.telegram.telegrambots.meta;
+
+import java.nio.charset.StandardCharsets;
+
+public class MemoizedUTF16String {
+
+    private final String original;
+
+    private byte[] cache;
+
+    public MemoizedUTF16String(String string) {
+        this.original = string;
+    }
+
+    public MemoizedUTF16String(byte[] utf16Data) {
+        this.original = null;
+        this.cache = utf16Data;
+    }
+
+    public byte[] getBytes() {
+        if (original != null && cache == null) {
+            byte[] newCache = original.getBytes(StandardCharsets.UTF_16LE);
+            this.cache = newCache;
+            return newCache;
+        } else {
+            return cache;
+        }
+    }
+
+    public String substring(int offsetUtf16, int lengthUtf16) {
+        byte[] bytes = getBytes();
+        if (bytes != null) {
+            return new String(bytes, offsetUtf16, lengthUtf16, StandardCharsets.UTF_16LE);
+        } else {
+            return "";
+        }
+    }
+}
diff --git a/telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/MemoizedUTF16Substring.java b/telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/MemoizedUTF16Substring.java
new file mode 100644
index 00000000..22214f28
--- /dev/null
+++ b/telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/MemoizedUTF16Substring.java
@@ -0,0 +1,35 @@
+package org.telegram.telegrambots.meta;
+
+import java.nio.charset.StandardCharsets;
+
+public class MemoizedUTF16Substring {
+
+    private final MemoizedUTF16String parentString;
+    private final int offsetUtf16;
+    private final int lengthUtf16;
+
+    private String cache;
+
+    public MemoizedUTF16Substring(MemoizedUTF16String parentString, int offsetUtf16, int lengthUtf16) {
+        this.parentString = parentString;
+        this.offsetUtf16 = offsetUtf16;
+        this.lengthUtf16 = lengthUtf16;
+    }
+
+    public String getString() {
+        if (parentString != null && cache == null) {
+            String newString = parentString.substring(offsetUtf16, lengthUtf16);
+            if (newString == null) {
+                this.cache = "";
+                return "";
+            } else {
+                this.cache = newString;
+                return newString;
+            }
+        } else if (cache != null) {
+            return cache;
+        } else {
+            return "";
+        }
+    }
+}
diff --git a/telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/api/objects/MessageEntity.java b/telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/api/objects/MessageEntity.java
index 362f7376..a0c16d9a 100644
--- a/telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/api/objects/MessageEntity.java
+++ b/telegrambots-meta/src/main/java/org/telegram/telegrambots/meta/api/objects/MessageEntity.java
@@ -5,6 +5,8 @@ import com.fasterxml.jackson.annotation.JsonProperty;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
+import java.util.function.Supplier;
+import lombok.AccessLevel;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.EqualsAndHashCode;
@@ -14,6 +16,8 @@ import lombok.NonNull;
 import lombok.RequiredArgsConstructor;
 import lombok.Setter;
 import lombok.ToString;
+import org.telegram.telegrambots.meta.MemoizedUTF16String;
+import org.telegram.telegrambots.meta.MemoizedUTF16Substring;
 import org.telegram.telegrambots.meta.api.interfaces.BotApiObject;
 
 /**
@@ -73,18 +77,19 @@ public class MessageEntity implements BotApiObject {
     private User user; ///< Optional. For “text_mention” only, the mentioned user
     @JsonProperty(LANGUAGE_FIELD)
     private String language; ///< Optional. For “pre” only, the programming language of the entity text
+    @Setter(AccessLevel.NONE)
     @JsonIgnore
-    private String text; ///< Text present in the entity. Computed from offset and length
+    private MemoizedUTF16Substring text; ///< Text present in the entity. Computed from offset and length
 
-    public void computeText(String message) {
-        if (message != null) {
-            byte[] bytes = message.getBytes(StandardCharsets.UTF_16LE);
-            if (bytes.length >= offset && offset >= 0 && length >= 0) {
-                text = new String(Arrays.copyOfRange(bytes, offset, offset + length),
-                    StandardCharsets.UTF_16LE);
-            } else {
-                text = "";
-            }
+    public String getText() {
+        if (text == null) {
+            return "";
+        } else {
+            return text.getString();
         }
     }
+
+    public void computeText(String message) {
+        text = new MemoizedUTF16Substring(new MemoizedUTF16String(message), offset, length);
+    }
 }