feat(dandi/mvc-view): support content-negotiated views

- use multiple `@View` decorators to configure multiple view options differentiated by MIME type or other request header

closes #66

packages/dandi/mvc-view/index.ts

@@ -9,4 +9,5 @@ export * from './src/view-metadata'
 export * from './src/view-result'
 export * from './src/view-result-factory'
 export * from './src/view-result-factory.error'
-export * from './src/view.route-transformer'
+export * from './src/view-route'
+export * from './src/view-route-transformer'

packages/dandi/mvc-view/src/mvc-view.module.ts

@@ -12,7 +12,7 @@ import {
 } from './view-engine-config'
 import { ViewEngineResolver } from './view-engine-resolver'
 import { VIEW_RESULT_FACTORY } from './view-result-factory'
-import { ViewRouteTransformer } from './view.route-transformer'
+import { ViewRouteTransformer } from './view-route-transformer'
 
 export interface MvcViewModule extends Array<any> {
   engine(extension: string, engine: Constructor<ViewEngine>): this

packages/dandi/mvc-view/src/view-metadata.ts

@@ -1,14 +1,32 @@
+import { HttpRequestHeaders, MimeType } from '@dandi/http'
 import { ControllerMethodMetadata } from '@dandi/mvc'
 
 import { RenderOptions } from './render-options'
 
+export type HttpRequestHeaderFunctionComparer<THeaderName extends keyof HttpRequestHeaders> =
+  (value: HttpRequestHeaders[THeaderName]) => boolean
+
+export type HttpRequestHeaderComparer<THeaderName extends keyof HttpRequestHeaders> =
+  HttpRequestHeaderFunctionComparer<THeaderName> | HttpRequestHeaders[THeaderName]
+
+export type HttpRequestHeaderComparers = {
+  [THeaderName in keyof HttpRequestHeaders]?:
+    HttpRequestHeaders[THeaderName] extends string ?
+      // allow regexps for headers with plain string values
+      RegExp | HttpRequestHeaderComparer<THeaderName> :
+        HttpRequestHeaderComparer<THeaderName>
+}
+
+export type ViewFilter = MimeType | HttpRequestHeaderComparers
+
 export interface ViewMetadata {
   name: string
   path?: string
   context: string
   options?: RenderOptions
+  filter?: ViewFilter[]
 }
 
 export interface ControllerViewMethodMetadata extends ControllerMethodMetadata {
-  view?: ViewMetadata
+  views?: ViewMetadata[]
 }