[FEAT] PerplexityAI Support (#778)

* add LLM support for perplexity

* update README & example env

* fix ENV keys in example env files

* slight changes for QA of perplexity support

* Update Perplexity AI name

---------

Co-authored-by: timothycarambat <rambat1010@gmail.com>

server/utils/AiProviders/perplexity/scripts/parse.mjs

@@ -0,0 +1,44 @@
+// Perplexity does not provide a simple REST API to get models,
+// so we have a table which we copy from their documentation
+// https://docs.perplexity.ai/edit/model-cards that we can
+// then parse and get all models from in a format that makes sense
+// Why this does not exist is so bizarre, but whatever.
+
+// To run, cd into this directory and run `node parse.mjs`
+// copy outputs into the export in ../models.js
+
+// Update the date below if you run this again because Perplexity added new models.
+// Last Collected: Feb 22, 2024
+
+import fs from "fs";
+
+function parseChatModels() {
+  const models = {};
+  const tableString = fs.readFileSync("chat_models.txt", { encoding: "utf-8" });
+  const rows = tableString.split("\n").slice(2);
+
+  rows.forEach((row) => {
+    let [model, contextLength] = row
+      .split("|")
+      .slice(1, -1)
+      .map((text) => text.trim());
+    model = model.replace(/`|\s*\[\d+\]\s*/g, "");
+    const maxLength = Number(contextLength.replace(/\s*\[\d+\]\s*/g, ""));
+    if (model && maxLength) {
+      models[model] = {
+        id: model,
+        name: model,
+        maxLength: maxLength,
+      };
+    }
+  });
+
+  fs.writeFileSync(
+    "chat_models.json",
+    JSON.stringify(models, null, 2),
+    "utf-8"
+  );
+  return models;
+}
+
+parseChatModels();