/**
 * Prompt runner — executes a PromptTemplate against note content via @bytelyst/llm.
 */

import { llm } from '../../lib/llm.js';
import { config } from '../../lib/config.js';
import {
  buildVisionMessage,
  hasVisionContent,
  type ChatMessage,
} from '@bytelyst/llm';
import type { PromptTemplateDoc, RunPromptInput, RunPromptOutput } from './types.js';

/**
 * Interpolate {{variable}} placeholders in a template string.
 */
function interpolate(template: string, vars: Record<string, string>): string {
  return template.replace(/\{\{(\w+)\}\}/g, (_, key) => vars[key] ?? `{{${key}}}`);
}

/**
 * Run a prompt template against provided input.
 * Handles text-only, image-only, and text+image inputs.
 */
export async function executePrompt(
  template: PromptTemplateDoc,
  input: RunPromptInput,
  noteBody: string,
): Promise<RunPromptOutput> {
  const provider = llm();

  // Build variables map
  const vars: Record<string, string> = {
    ...input.variables,
    noteBody,
    noteId: input.noteId,
    workspaceId: input.workspaceId,
  };
  if (input.inputText) vars.inputText = input.inputText;

  const userPrompt = interpolate(template.userPromptTemplate, vars);

  // Build messages
  const messages: ChatMessage[] = [
    { role: 'system', content: template.systemPrompt },
  ];

  if (input.imageUrl && (template.inputType === 'image' || template.inputType === 'text+image')) {
    messages.push(buildVisionMessage(userPrompt, input.imageUrl));
  } else {
    messages.push({ role: 'user', content: userPrompt });
  }

  // Select model: vision model for image content, custom model, or default
  const req = { messages };
  let model = template.model || config.LLM_DEFAULT_MODEL;
  if (hasVisionContent(req)) {
    model = config.LLM_VISION_MODEL;
  }

  const result = await provider.chatCompletion({
    messages,
    model,
    temperature: template.temperature ?? 0.7,
    maxTokens: template.maxTokens ?? 4096,
  });

  return {
    content: result.content,
    model: result.model,
    usage: result.usage,
    templateSlug: template.slug,
    outputType: template.outputType,
  };
}