More work on modelProviders

I think everything that's OpenAI-specific is inside modelProviders at this point, so we can get started adding more providers.

src/modelProviders/types.ts

@@ -1,14 +1,48 @@
 import { type JSONSchema4 } from "json-schema";
+import { type JsonValue } from "type-fest";
 
-export type ModelProviderModel = {
+type ModelProviderModel = {
   name: string;
   learnMore: string;
 };
 
-export type ModelProvider<SupportedModels extends string, InputSchema> = {
+export type CompletionResponse<T> =
+  | { type: "error"; message: string; autoRetry: boolean; statusCode?: number }
+  | {
+      type: "success";
+      value: T;
+      timeToComplete: number;
+      statusCode: number;
+      promptTokens?: number;
+      completionTokens?: number;
+      cost?: number;
+    };
+
+export type ModelProvider<SupportedModels extends string, InputSchema, OutputSchema> = {
   name: string;
   models: Record<SupportedModels, ModelProviderModel>;
   getModel: (input: InputSchema) => SupportedModels | null;
   shouldStream: (input: InputSchema) => boolean;
   inputSchema: JSONSchema4;
+  getCompletion: (
+    input: InputSchema,
+    onStream: ((partialOutput: OutputSchema) => void) | null,
+  ) => Promise<CompletionResponse<OutputSchema>>;
+
+  // This is just a convenience for type inference, don't use it at runtime
+  _outputSchema?: OutputSchema | null;
+};
+
+export type NormalizedOutput =
+  | {
+      type: "text";
+      value: string;
+    }
+  | {
+      type: "json";
+      value: JsonValue;
+    };
+
+export type ModelProviderFrontend<ModelProviderT extends ModelProvider<any, any, any>> = {
+  normalizeOutput: (output: NonNullable<ModelProviderT["_outputSchema"]>) => NormalizedOutput;
 };