[Add] Framework-API 补充一个字符序列 Message 实现;

[Add] CharSequenceMessage 添加一个单调的实现(用于装 String, StringBuilder 或 StringBuffer 之类的);

ContentGrabbingJi-framework-api/src/main/java/net/lamgc/cgj/bot/framework/message/CharSequenceMessage.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2020  LamGC
+ *
+ * ContentGrabbingJi is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * ContentGrabbingJi is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package net.lamgc.cgj.bot.framework.message;
+
+/**
+ * 字符序列消息对象.
+ * <p> 仅包含了一段字符串.
+ * @author LamGC
+ */
+public final class CharSequenceMessage implements Message {
+
+    private final CharSequence content;
+
+    public CharSequenceMessage(CharSequence content) {
+        if (content instanceof Message) {
+            this.content = ((Message) content).contentToString();
+        } else {
+            this.content = content;
+        }
+    }
+
+    @Override
+    public String contentToString() {
+        return content.toString();
+    }
+
+    @Override
+    public int length() {
+        return content.length();
+    }
+
+    @Override
+    public char charAt(int index) {
+        return content.charAt(index);
+    }
+
+    @Override
+    public CharSequence subSequence(int start, int end) {
+        return content.subSequence(start, end);
+    }
+
+    @Override
+    public String toString() {
+        return "CharSequenceMessage{" +
+                "content='" + content + '\'' +
+                '}';
+    }
+}