feat(research): Introduce research API with provider implementations, docs and tests

ts/provider.perplexity.ts

@@ -1,7 +1,7 @@
 import * as plugins from './plugins.js';
 import * as paths from './paths.js';
 import { MultiModalModel } from './abstract.classes.multimodal.js';
-import type { ChatOptions, ChatResponse, ChatMessage } from './abstract.classes.multimodal.js';
+import type { ChatOptions, ChatResponse, ChatMessage, ResearchOptions, ResearchResponse } from './abstract.classes.multimodal.js';
 
 export interface IPerplexityProviderOptions {
   perplexityToken: string;
@@ -168,4 +168,69 @@ export class PerplexityProvider extends MultiModalModel {
   }): Promise<{ message: any }> {
     throw new Error('Document processing is not supported by Perplexity.');
   }
+
+  public async research(optionsArg: ResearchOptions): Promise<ResearchResponse> {
+    // Perplexity has Sonar models that are optimized for search
+    // sonar models: sonar, sonar-pro
+    const model = optionsArg.searchDepth === 'deep' ? 'sonar-pro' : 'sonar';
+
+    try {
+      const response = await fetch('https://api.perplexity.ai/chat/completions', {
+        method: 'POST',
+        headers: {
+          'Authorization': `Bearer ${this.options.perplexityToken}`,
+          'Content-Type': 'application/json',
+        },
+        body: JSON.stringify({
+          model,
+          messages: [
+            {
+              role: 'system',
+              content: 'You are a helpful research assistant. Provide accurate information with sources.'
+            },
+            {
+              role: 'user',
+              content: optionsArg.query
+            }
+          ],
+          temperature: 0.7,
+          max_tokens: 4000
+        }),
+      });
+
+      if (!response.ok) {
+        throw new Error(`Perplexity API error: ${response.statusText}`);
+      }
+
+      const result = await response.json();
+      const answer = result.choices[0].message.content;
+
+      // Parse citations from the response
+      const sources: Array<{ url: string; title: string; snippet: string }> = [];
+
+      // Perplexity includes citations in the format [1], [2], etc. with sources listed
+      // This is a simplified parser - could be enhanced based on actual Perplexity response format
+      if (result.citations) {
+        for (const citation of result.citations) {
+          sources.push({
+            url: citation.url || '',
+            title: citation.title || '',
+            snippet: citation.snippet || ''
+          });
+        }
+      }
+
+      return {
+        answer,
+        sources,
+        metadata: {
+          model,
+          searchDepth: optionsArg.searchDepth || 'basic'
+        }
+      };
+    } catch (error) {
+      console.error('Perplexity research error:', error);
+      throw new Error(`Failed to perform research: ${error.message}`);
+    }
+  }
 }