add getContext

index.ts

-import { Adapter, Bot } from 'koishi';
+import { Adapter, Bot, Context, Filter, s } from 'koishi';
 import _ from 'lodash';
 import { RegisterSchema, SchemaProperty } from 'schemastery-gen';
 
@@ -12,6 +12,18 @@ export class ChannelTarget {
   toDesc(): string | [string, string] {
     return this.guildId ? [this.channelId, this.guildId] : this.channelId;
   }
+
+  toFilter(): Filter {
+    return (s) => {
+      if (this.channelId !== s.channelId) {
+        return false;
+      }
+      if (this.guildId && this.guildId !== s.guildId) { 
+        return false;
+      }
+      return true;
+    };
+  }
 }
 
 @RegisterSchema()
@@ -51,6 +63,25 @@ export class SendTarget {
     );
   }
 
+  getContext(ctx: Context) {
+    if (this.bot) {
+      const [platform, id] = this.bot.split(':');
+      ctx = ctx.platform(platform).self(id);
+    }
+    let filters: Filter[] = [];
+    if (this.users?.length) {
+      const userSet = new Set(this.users);
+      filters.push((s) => s.type === 'private' && userSet.has(s.userId));
+    }
+    if (this.channels?.length) {
+      filters = filters.concat(this.channels.map((c) => c.toFilter()));
+    }
+    if (filters.length) {
+      ctx = ctx.intersect((s) => filters.some((f) => f(s)));
+    }
+    return ctx;
+  }
+
   async send(bots: Adapter.BotList, content: string) {
     const bot = this.getBot(bots);
     if (!bot) {