FEATURE: support upload.getUrl in custom tools (#1384)

* FEATURE: support upload.getUrl in custom tools

Some tools need to share images with an API. A common pattern
is for APIs to expect a URL.

This allows converting upload://123123 to a proper CDN friendly
URL from within a custom tool

* no support for secure uploads, so be explicit about it.

app/models/ai_tool.rb

@@ -142,6 +142,7 @@ class AiTool < ActiveRecord::Base
      *      base_64_content (string): Base64 encoded content of the file.
      *    Returns: { id: number, url: string, short_url: string } - Details of the created upload record.
      *
+     *    upload.getUrl(shortUrl): Given a short URL, eg upload://12345, returns the full CDN friendly URL of the upload.
      * 5. chain
      *    Controls the execution flow.
      *

lib/personas/tool_runner.rb

@@ -72,6 +72,7 @@ module DiscourseAi
 
         const upload = {
           create: _upload_create,
+          getUrl: _upload_get_url,
         }
 
         const chain = {
@@ -570,6 +571,24 @@ module DiscourseAi
       end
 
       def attach_upload(mini_racer_context)
+        mini_racer_context.attach(
+          "_upload_get_url",
+          ->(short_url) do
+            in_attached_function do
+              return nil if short_url.blank?
+
+              sha1 = Upload.sha1_from_short_url(short_url)
+              return nil if sha1.blank?
+
+              upload = Upload.find_by(sha1: sha1)
+              return nil if upload.nil?
+              # TODO we may need to introduce an API to unsecure, secure uploads
+              return nil if upload.secure?
+
+              GlobalPath.full_cdn_url(upload.url)
+            end
+          end,
+        )
         mini_racer_context.attach(
           "_upload_create",
           ->(filename, base_64_content) do

spec/models/ai_tool_spec.rb

@@ -675,4 +675,64 @@ RSpec.describe AiTool do
       expect(ai_persona.temperature).to eq(0.5)
     end
   end
+
+  describe "upload URL resolution" do
+    it "can resolve upload short URLs to public URLs" do
+      upload =
+        Fabricate(
+          :upload,
+          sha1: "abcdef1234567890abcdef1234567890abcdef12",
+          url: "/uploads/default/original/1X/test.jpg",
+          original_filename: "test.jpg",
+        )
+
+      script = <<~JS
+      function invoke(params) {
+        return upload.getUrl(params.short_url);
+      }
+    JS
+
+      tool = create_tool(script: script)
+      runner = tool.runner({ "short_url" => upload.short_url }, llm: nil, bot_user: nil)
+
+      result = runner.invoke
+
+      expect(result).to eq(GlobalPath.full_cdn_url(upload.url))
+    end
+
+    it "returns null for invalid upload short URLs" do
+      script = <<~JS
+      function invoke(params) {
+        return upload.getUrl(params.short_url);
+      }
+    JS
+
+      tool = create_tool(script: script)
+      runner = tool.runner({ "short_url" => "upload://invalid" }, llm: nil, bot_user: nil)
+
+      result = runner.invoke
+
+      expect(result).to be_nil
+    end
+
+    it "returns null for non-existent uploads" do
+      script = <<~JS
+      function invoke(params) {
+        return upload.getUrl(params.short_url);
+      }
+    JS
+
+      tool = create_tool(script: script)
+      runner =
+        tool.runner(
+          { "short_url" => "upload://hwmUkTAL9mwhQuRMLsXw6tvDi5C.jpeg" },
+          llm: nil,
+          bot_user: nil,
+        )
+
+      result = runner.invoke
+
+      expect(result).to be_nil
+    end
+  end
 end