import { readFileSync, existsSync } from 'node:fs';
import { extname } from 'node:path';

type OcrConfig = {
  url: string;
  model: string;
  api_key?: string;
};

function getOcrConfig(): OcrConfig | null {
  try {
    const raw = process.env.OFFICER_RESOURCES;
    if (!raw) return null;
    const resources = JSON.parse(raw) as Record<string, Record<string, string>>;
    const ocr = resources['optical-character-recognition'];
    if (!ocr?.url) return null;
    return { url: ocr.url, model: ocr.model ?? '', api_key: ocr.api_key };
  } catch {
    return null;
  }
}

const DEFAULT_PROMPT = [
  'You are an OCR assistant. Extract meaningful text content from images.',
  'Rules:',
  '- Output ONLY the extracted text, no commentary or explanations.',
  '- For documents, articles, books: preserve the original text, paragraphs, and structure as markdown.',
  '- For tables: use markdown table format.',
  '- For code/terminal screenshots: use fenced code blocks.',
  '- For handwritten text: do your best to transcribe accurately.',
  '- For mixed content: use appropriate formatting for each section.',
].join('\n');

export async function execute(
  _toolCallId: string,
  params: { file_path: string; prompt?: string },
) {
  const config = getOcrConfig();
  if (!config) {
    return {
      content: [{ type: 'text', text: 'OCR is not configured. Set it up in Settings → Resources → Optical Character Recognition.' }],
      isError: true,
    };
  }

  const { file_path, prompt } = params;

  if (!existsSync(file_path)) {
    return {
      content: [{ type: 'text', text: `File not found: ${file_path}` }],
      isError: true,
    };
  }

  const imageBytes = readFileSync(file_path);
  const base64 = imageBytes.toString('base64');
  const ext = extname(file_path).replace('.', '').toLowerCase();
  const mime = ext === 'jpg' || ext === 'jpeg' ? 'image/jpeg' : ext === 'webp' ? 'image/webp' : ext === 'gif' ? 'image/gif' : `image/${ext || 'png'}`;

  const headers: Record<string, string> = { 'Content-Type': 'application/json' };
  if (config.api_key) headers['Authorization'] = `Bearer ${config.api_key}`;

  const systemPrompt = prompt ? `${DEFAULT_PROMPT}\n\nAdditional instructions: ${prompt}` : DEFAULT_PROMPT;

  try {
    const res = await fetch(`${config.url.replace(/\/+$/, '')}/v1/chat/completions`, {
      method: 'POST',
      headers,
      body: JSON.stringify({
        model: config.model,
        messages: [
          { role: 'system', content: systemPrompt },
          {
            role: 'user',
            content: [
              { type: 'image_url', image_url: { url: `data:${mime};base64,${base64}` } },
            ],
          },
        ],
        max_tokens: 4096,
      }),
    });

    if (!res.ok) {
      const errorText = await res.text().catch(() => '');
      return {
        content: [{ type: 'text', text: `OCR API error (${res.status}): ${errorText}` }],
        isError: true,
      };
    }

    const json = await res.json() as { choices?: Array<{ message?: { content?: string } }> };
    const text = json.choices?.[0]?.message?.content ?? '';

    if (!text) {
      return {
        content: [{ type: 'text', text: 'OCR returned empty result — the image may not contain readable text.' }],
        isError: false,
      };
    }

    return {
      content: [{ type: 'text', text }],
    };
  } catch (err) {
    const message = err instanceof Error ? err.message : String(err);
    return {
      content: [{ type: 'text', text: `OCR request failed: ${message}` }],
      isError: true,
    };
  }
}