core/app/Http/Controllers/Admin/EditTemplate.php

<?php

namespace App\Http\Controllers\Admin;

use App\Http\Controllers\Controller;
use App\Http\Requests;
use App\Http\Requests\EditTemplateRequest;
use App\Models\Template;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\File;

class EditTemplate extends Controller
{
    /**
     * Render form for editing template
     *
     * @param $template
     *
     * @return \Illuminate\Contracts\View\Factory|\Illuminate\View\View
     */
    public function getEdit($template)
    {
        $template = Template::findOrFail($template);
        $path = $template->getPath();

        // load template content
        $absolutePath = $template->getPathToTemplate();
        $content = file_get_contents($absolutePath);

        return view('admin.templates.edit', [
            'template'        => $template,
            'templateContent' => $content,
            'isWritable'      => is_writable(dirname($absolutePath)),
            'path'            => $path,
        ]);
    }

    /**
     * Save meta information about template and edited content
     *
     * @param EditTemplateRequest $request
     * @param                     $templateId
     *
     * @return \Illuminate\Http\RedirectResponse
     */
    public function postEdit(EditTemplateRequest $request, $templateId)
    {
        // find template
        $template = Template::findOrFail($templateId);

        // setup meta information
        $template->name = $request->name;

        if ($request->description) {
            $template->description = $request->description;
        }

        // save meta information into database
        $template->save();

        // try to save content
        return $this->saveContent($template, $request);
    }

    /**
     * Save physical content of given template
     *
     * @param Template            $template
     * @param EditTemplateRequest $request
     *
     * @return \Illuminate\Http\RedirectResponse
     */
    private function saveContent(Template $template, EditTemplateRequest $request)
    {
        // get templates with paths
        $originalTemplate = $template->getPathToTemplate();
        $customTemplate = $template->getPathToTemplate(Template::CUSTOM_EDIT_DIRECTORY);

        // get paths
        $originalDir = dirname($originalTemplate);
        $customDir = dirname($customTemplate);

        // try to save content
        if (!is_writable($customDir) && !is_writable($originalDir)) {
            return redirect()
                ->route('templates.edit', ['id' => $request->id])
                ->withInput()
                ->with('error', trans('admin/templates.cannotWriteContent'));
        }

        // save new content only if something was changed
        if ($this->isContentDifferent($originalTemplate, $customTemplate, $request->templateContent)) {

            // create directory for custom updates
            if (!is_dir($customDir)) {
                File::makeDirectory($customDir);
            }

            // make copy of existing template (if exists)
            $this->backupTemplates($customTemplate);

            // save content
            File::put($customTemplate, $request->templateContent);
        }

        return redirect()
            ->route('templates.overview', ['id' => $template->path])
            ->with('success', trans('admin/templates.editSuccessfull'));
    }

    /**
     * Get last "revision" of edited template.
     *
     * Template changes are not discarded, however new file is created. Last template is renamed to
     * <template>.blade.php.<num>, where <num> is result of this method.
     *
     * @param $template
     *
     * @return int
     */
    private function getNewRevisionNumber($template)
    {
        $number = 0;
        while (File::exists($template . '.' . $number)) {
            $number++;
        }

        return $number;
    }

    /**
     * If exists previously edited template, rename it to <template>.blade.php.<number>
     *
     * @param $template
     */
    private function backupTemplates($template)
    {
        // get last sequence number
        $number = $this->getNewRevisionNumber($template);

        // nothing to backup
        if ($number == 0) {
            return;
        }

        // rename template
        File::move($template, $template . '.' . $number);
    }

    /**
     * Compare data from previous/original template
     *
     * @param $originalTemplate
     * @param $customTemplate
     * @param $currentContent
     *
     * @return bool
     */
    private function isContentDifferent($originalTemplate, $customTemplate, $currentContent)
    {
        /**
         * get last revision of template - we need to substract 1 from result from getNewRevisionNumber(),
         * because this method returns number of first non-existing template
         */
        $lastRevision = $this->getNewRevisionNumber($customTemplate) - 1;

        // select compared file
        if ($lastRevision < 0) {
            $diffFile = $originalTemplate;
        } else {
            $diffFile = $customTemplate . '.' . $lastRevision;
        }

        // get content
        $originalContent = file_get_contents($diffFile);

        return $originalContent != $currentContent;
    }
}