add plugin factory

index.ts

@@ -4,5 +4,6 @@ export * from './src/decorators';
 export * from './src/cosmotype-exports';
 export * from './src/base-plugin';
 export * from './src/multi-plugin';
+export * from './src/plugin-factory';
 export * from './src/def/interfaces';
 export * from 'schemastery-gen';

src/plugin-factory.ts

+import { Context } from 'koishi';
+import { ClassType, Mixin, SchemaProperty } from 'schemastery-gen';
+import { PluginSchema } from './decorators';
+import { BasePlugin } from './base-plugin';
+
+export function CreatePluginFactory<C, P>(
+  basePlugin: new (ctx: Context, config: C) => P,
+  baseConfig: ClassType<C>,
+): <S>(specificConfig?: ClassType<S>) => new (ctx: Context, config: S & C) => P;
+export function CreatePluginFactory<C, P>(
+  basePlugin: new (ctx: Context, config: C) => any,
+  baseConfig: ClassType<C>,
+): <S>(
+  specificConfig?: ClassType<S>,
+) => new (ctx: Context, config: S & C) => P {
+  return (specificConfig) => {
+    const plugin = class specificPlugin extends basePlugin {};
+    const config = specificConfig
+      ? Mixin(specificConfig, baseConfig)
+      : baseConfig;
+    PluginSchema(config)(plugin);
+    return plugin;
+  };
+}
+
+class TestConfig {
+  @SchemaProperty()
+  foo: string;
+}