<?php

namespace App\FileTools\VideoDescriptor;

use App\AIPrompt\IAIPrompt;
use App\AIPrompt\OpenAPIPrompt;
use App\FileTools\OCR\IImageOCR;
use App\FileTools\OCR\TesseractImageOCR;
use Log;

class OCRLLMVideoDescriptor implements IVideoDescriptor
{
    private IImageOCR $ocr;
    private IAIPrompt $llm; // LLM That can visualize images and generate descriptions

    public const DESCRIPTION_PROMPT = "Describe the video based on the screenshots. Each screenshot has a timestamp of when in the video the screenshot was taken, an OCR result and a description of the screenshot by an LLM. Do not specify that it is a video, just describe the video. The description must have a maximum of 500 words.\n";

    public function __construct() {
        $this->ocr = new TesseractImageOCR();
        $this->llm = new OpenAPIPrompt();
    }

    public function getDescription(string $filePath): ?string
    {
        /*
            1. Cut videos in screenshots
            2. Use OCR to extract text from screenshots
            3. Use LLM to generate a description of the screenshot
            4. Combine the descriptions of all screenshots into a single description
            5. Ask an LLM to describe the video
        */

        // Step 1: Cut video into screenshots
        $screenshots = $this->cutVideoIntoScreenshots($filePath);

        if (empty($screenshots)) {
            throw new \Exception("No screenshots were generated from the video {$filePath}.");
        }

        // Step 2 & 3: Use OCR to extract text and LLM to get description from screenshots
        $descriptions = [];
        foreach ($screenshots as $screenshot) {
            $descriptions[$screenshot] = [];

            $ocrDescription = $this->ocr->performOCR($screenshot);
            $ocrDescription = empty($ocrDescription) ? 'No text found' : $ocrDescription;
            $descriptions[$screenshot]['ocr'] = $ocrDescription;

            $llmDescription = $this->llm->generate(
                config('llm.models.vision.name'),
                "Describe the content of this screenshot from a video. Do not specify that it is a screenshot, just describe the content.",
                images: [$screenshot],
                outputFormat: '{"type": "object", "properties": {"answer": {"type": "string"}}, "required": ["answer"]}',
                systemMessage: "The user will ask something. Give your direct answer to that.",
                keepAlive: $screenshot != end($screenshots), // Keep alive for all but the last screenshot
                shouldThink: config('llm.models.vision.shouldThink')
            );
            $descriptions[$screenshot]['text'] = json_decode($llmDescription, true)['answer'] ?? 'No description generated';
        }

        // HERE COULD BE SOME INTERMEDIATE PROCESSING OF DESCRIPTIONS

        // Step 4: Combine the descriptions of all screenshots into a single description
        $combinedDescription = '';
        $screenshotCount = 0;
        foreach ($descriptions as $screenshot => $description) {
            $screenshotCount++;
            $combinedDescription .= "Screenshot: {$screenshotCount}\n";
            $combinedDescription .= "Timestamp: {$screenshotCount}s\n"; // TODO Cut the video in smaller parts when the video is short
            $combinedDescription .= "OCR: {$description['ocr']}\n";
            $combinedDescription .= "LLM Description: {$description['text']}\n\n";
        }
        $combinedDescription = trim($combinedDescription);

        // Step 5: Ask an LLM to describe the video based on the combined descriptions
        $llmDescription = $this->llm->generate(
            config('llm.models.chat.name'),
            self::DESCRIPTION_PROMPT . $combinedDescription,
            outputFormat: '{"type": "object", "properties": {"answer": {"type": "string"}}, "required": ["answer"]}',
            systemMessage: "The user will ask something. Give your direct answer to that.",
            keepAlive: true,
            shouldThink: config('llm.models.chat.shouldThink')
        );

        $llmDescription = json_decode($llmDescription, true)['answer'] ?? null;
        if (empty($llmDescription)) {
            $llmDescription = null;
        }

        return $llmDescription;
    }

    /**
     * Cut the video into screenshots.
     * Using ffmpeg to cut the video into screenshots at regular intervals.
     * The screenshots will be saved in a temporary directory.
     * @param string $filePath
     * @return void
     */
    private function cutVideoIntoScreenshots(string $filePath): array
    {
        $tempDir = sys_get_temp_dir() . '/video_screenshots';
        if (!is_dir($tempDir)) {
            mkdir($tempDir, 0777, true);
        }

        Log::info("Cutting video into screenshots: $filePath");

        $outputPattern = $tempDir . '/screenshot_%d.png';
        $command = "ffmpeg -i " . escapeshellarg($filePath) . " -vf fps=1 " . escapeshellarg($outputPattern);
        exec($command);

        // Collect all screenshots
        $screenshots = glob($tempDir . '/screenshot_*.png');
        return $screenshots;
    }
}