<?php

namespace App\Services\Documenti;

use App\Models\Documento;
use Illuminate\Support\Facades\Schema;
use Illuminate\Support\Facades\Storage;
use Smalot\PdfParser\Parser;

class PdfTextExtractionService
{
    /**
     * Estrae il testo da un PDF e lo salva su `documenti.contenuto_ocr` (se presente).
     *
     * @return array{status: 'ok'|'skipped'|'error', message?: string, chars?: int, engine?: string}
     */
    public function extractAndStore(Documento $documento, bool $force = false): array
    {
        $relativePath = $this->resolvePdfPath($documento);
        if ($relativePath === null) {
            return ['status' => 'skipped', 'message' => 'PDF non disponibile'];
        }

        if (! Storage::disk('local')->exists($relativePath)) {
            return ['status' => 'error', 'message' => 'File PDF non trovato su storage'];
        }

        if (! $force) {
            $existing = null;
            if (Schema::hasColumn('documenti', 'contenuto_ocr')) {
                $existing = $documento->contenuto_ocr;
            } elseif (Schema::hasColumn('documenti', 'testo_estratto_ocr')) {
                $existing = $documento->testo_estratto_ocr;
            }

            if (is_string($existing) && trim($existing) !== '') {
                return ['status' => 'skipped', 'message' => 'Testo già presente'];
            }
        }

        $absolutePath = Storage::disk('local')->path($relativePath);

        try {
            [$text, $engine] = $this->extractText($absolutePath);
        } catch (\Throwable $e) {
            return ['status' => 'error', 'message' => $e->getMessage()];
        }

        $text = $this->normalizeText($text);
        $chars = mb_strlen($text);

        if ($chars <= 0) {
            return ['status' => 'error', 'message' => 'Testo PDF vuoto (forse è una scansione)'];
        }

        $update = [];
        if (Schema::hasColumn('documenti', 'contenuto_ocr')) {
            $update['contenuto_ocr'] = $text;
        }
        if (Schema::hasColumn('documenti', 'testo_estratto_ocr')) {
            $update['testo_estratto_ocr'] = mb_substr($text, 0, 20000);
        }

        if (empty($update)) {
            return ['status' => 'error', 'message' => 'Schema documenti senza colonne OCR/testo'];
        }

        $documento->forceFill($update)->save();

        return ['status' => 'ok', 'chars' => $chars, 'engine' => $engine];
    }

    private function resolvePdfPath(Documento $documento): ?string
    {
        $candidate = null;

        if (isset($documento->percorso_file) && is_string($documento->percorso_file) && $documento->percorso_file !== '') {
            $candidate = $documento->percorso_file;
        } elseif (isset($documento->path_file) && is_string($documento->path_file) && $documento->path_file !== '') {
            $candidate = $documento->path_file;
        }

        if (! is_string($candidate) || trim($candidate) === '') {
            return null;
        }

        $candidate = trim($candidate);
        $lower = strtolower($candidate);
        if (! str_ends_with($lower, '.pdf')) {
            return null;
        }

        return $candidate;
    }

    /**
     * @return array{0:string,1:string} [text, engine]
     */
    private function extractText(string $absolutePath): array
    {
        // Prefer pdftotext if available: è più robusto su tanti PDF “reali”.
        $pdftotext = $this->findBinary('pdftotext');
        if ($pdftotext !== null) {
            $cmd = escapeshellcmd($pdftotext) . ' -layout -nopgbrk ' . escapeshellarg($absolutePath) . ' -';
            $output = shell_exec($cmd);
            $output = is_string($output) ? $output : '';
            if (trim($output) !== '') {
                return [$output, 'pdftotext'];
            }
        }

        // Fallback PHP parser (no system deps).
        $parser = new Parser();
        $pdf = $parser->parseFile($absolutePath);
        return [$pdf->getText(), 'smalot/pdfparser'];
    }

    private function findBinary(string $name): ?string
    {
        $path = shell_exec('command -v ' . escapeshellarg($name) . ' 2>/dev/null');
        $path = is_string($path) ? trim($path) : '';
        return $path !== '' ? $path : null;
    }

    private function normalizeText(string $text): string
    {
        // Normalize line endings and strip null bytes.
        $text = str_replace("\r\n", "\n", $text);
        $text = str_replace("\r", "\n", $text);
        $text = str_replace("\0", '', $text);

        // Best-effort encoding normalization.
        if (! mb_check_encoding($text, 'UTF-8')) {
            $text = mb_convert_encoding($text, 'UTF-8');
        }

        return trim($text);
    }
}