<?php

class FileUploader {

    private $target_dir;
    private $allowed_mimes = ['image/jpeg', 'image/png', 'image/gif', 'image/webp', 'application/pdf'];
    private $allowed_extensions = ['jpg', 'jpeg', 'png', 'gif', 'webp', 'pdf'];
    private $max_size = 5 * 1024 * 1024; // 5MB
    private $uploaded_files = [];   // newly uploaded filenames
    private $deleted_files = [];    // files we deleted from disk

    public function __construct($target_dir) {
        $this->target_dir = rtrim($target_dir, '/') . '/';
        $this->ensureDirectory();
    }

    private function ensureDirectory() {
        if (!is_dir($this->target_dir)) {
            if (!mkdir($this->target_dir, 0755, true)) {
                throw new Exception("Failed to create directory: " . $this->target_dir);
            }
        }
        if (!is_writable($this->target_dir)) {
            throw new Exception("Target directory is not writable: " . $this->target_dir);
        }
    }

    /**
     * Remove files that user deleted in the UI
     */
    public function cleanup($existing_csv, $keep_csv) {
        if (empty($existing_csv)) return;

        $existing = array_filter(array_map('trim', explode(',', $existing_csv)));
        $keep = !empty($keep_csv) ? array_filter(array_map('trim', explode(',', $keep_csv))) : [];

        foreach ($existing as $file) {
            if (!in_array($file, $keep)) {
                $path = $this->target_dir . $file;
                if (file_exists($path)) {
                    unlink($path);
                    $this->deleted_files[] = $file;
                }
            }
        }
    }

    /**
     * Upload new files from $_FILES
     * Returns array of errors (empty = success)
     */
    public function upload($field_name) {
        if (!isset($_FILES[$field_name])) return [];

        $errors = [];

        // Normalize single file to array structure
        $files = $_FILES[$field_name];
        if (!is_array($files['name'])) {
            $files['name']     = [$files['name']];
            $files['tmp_name'] = [$files['tmp_name']];
            $files['error']    = [$files['error']];
            $files['size']     = [$files['size']];
        }

        foreach ($files['name'] as $key => $name) {
            $error_code = $files['error'][$key];

            if ($error_code !== UPLOAD_ERR_OK) {
                $errors[] = "{$name}: " . $this->getUploadError($error_code);
                continue;
            }

            $tmp_name  = $files['tmp_name'][$key];
            $file_size = $files['size'][$key];
            $extension = strtolower(pathinfo($name, PATHINFO_EXTENSION));

            if ($file_size > $this->max_size) {
                $errors[] = "{$name}: exceeds " . ($this->max_size / 1024 / 1024) . "MB limit";
                continue;
            }

            if (!in_array($extension, $this->allowed_extensions)) {
                $errors[] = "{$name}: .{$extension} is not allowed";
                continue;
            }

            $finfo = finfo_open(FILEINFO_MIME_TYPE);
            $mime  = finfo_file($finfo, $tmp_name);
            finfo_close($finfo);

            if (!in_array($mime, $this->allowed_mimes)) {
                $errors[] = "{$name}: content type ({$mime}) is not allowed";
                continue;
            }

            // FILE NAME SANITIZATION + UNIQUE ID
            $original = pathinfo($name, PATHINFO_FILENAME);
            $original = preg_replace('/[^a-zA-Z0-9_-]/', '_', $original); // sanitize
            $file_id  = $original . "_" . uniqid() . "." . $extension;

            $destination = $this->target_dir . $file_id;

            if (move_uploaded_file($tmp_name, $destination)) {
                $this->uploaded_files[] = $file_id;
                chmod($destination, 0644);
            } else {
                $errors[] = "{$name}: failed to save";
            }
        }

        return $errors;
    }

    /**
     * Build final CSV string for DB
     */
    public function buildFileString($keep_csv) {
        $keep = !empty($keep_csv) ? array_filter(array_map('trim', explode(',', $keep_csv))) : [];
        $final = array_merge($keep, $this->uploaded_files);
        return implode(",", array_filter($final));
    }
    
    /**
     * Build final CSV string for DB as single file
     */
    public function getUploadedFiles() {
        return $this->uploaded_files;
    }

    /**
     * Rollback uploaded files if DB fails
     */
    public function rollbackUploads() {
        foreach ($this->uploaded_files as $file) {
            $path = $this->target_dir . $file;
            if (file_exists($path)) {
                unlink($path);
            }
        }
        $this->uploaded_files = [];
    }

    private function getUploadError($code) {
        $messages = [
            UPLOAD_ERR_INI_SIZE   => "exceeds server max upload size (" . ini_get('upload_max_filesize') . ")",
            UPLOAD_ERR_FORM_SIZE  => "exceeds form max size",
            UPLOAD_ERR_PARTIAL    => "was only partially uploaded",
            UPLOAD_ERR_NO_FILE    => "no file was sent",
            UPLOAD_ERR_NO_TMP_DIR => "server missing temp folder",
            UPLOAD_ERR_CANT_WRITE => "server failed to write to disk",
            UPLOAD_ERR_EXTENSION  => "blocked by server extension",
        ];
        return $messages[$code] ?? "unknown error (code {$code})";
    }
}


?>