<?php

namespace SilverStripe\Assets;

use SilverStripe\Assets\Storage\AssetStore;
use SilverStripe\Core\Object;
use SilverStripe\ORM\DataList;
use SilverStripe\ORM\DB;
use SilverStripe\ORM\Versioning\Versioned;

/**
 * Service to help migrate File dataobjects to the new APL.
 *
 * This service does not alter these records in such a way that prevents downgrading back to 3.x
 */
class FileMigrationHelper extends Object
{

    /**
     * Perform migration
     *
     * @param string $base Absolute base path (parent of assets folder). Will default to BASE_PATH
     * @return int Number of files successfully migrated
     */
    public function run($base = null)
    {
        if (empty($base)) {
            $base = BASE_PATH;
        }
        // Check if the File dataobject has a "Filename" field.
        // If not, cannot migrate
        /** @skipUpgrade */
        if (!DB::get_schema()->hasField('File', 'Filename')) {
            return 0;
        }

        // Set max time and memory limit
        increase_time_limit_to();
        increase_memory_limit_to();

        // Loop over all files
        $count = 0;
        $originalState = Versioned::get_reading_mode();
        Versioned::set_stage(Versioned::DRAFT);
        $filenameMap = $this->getFilenameArray();
        foreach ($this->getFileQuery() as $file) {
            // Get the name of the file to import
            $filename = $filenameMap[$file->ID];
            $success = $this->migrateFile($base, $file, $filename);
            if ($success) {
                $count++;
            }
        }
        Versioned::set_reading_mode($originalState);
        return $count;
    }

    /**
     * Migrate a single file
     *
     * @param string $base Absolute base path (parent of assets folder)
     * @param File $file
     * @param string $legacyFilename
     * @return bool True if this file is imported successfully
     */
    protected function migrateFile($base, File $file, $legacyFilename)
    {
        // Make sure this legacy file actually exists
        $path = $base . '/' . $legacyFilename;
        if (!file_exists($path)) {
            return false;
        }


        // Copy local file into this filesystem
        $filename = $file->generateFilename();
        $result = $file->setFromLocalFile(
            $path,
            $filename,
            null,
            null,
            array('conflict' => AssetStore::CONFLICT_OVERWRITE)
        );

        // Move file if the APL changes filename value
        if ($result['Filename'] !== $filename) {
            $file->setFilename($result['Filename']);
        }

        // Save and publish
        $file->write();
        $file->copyVersionToStage(Versioned::DRAFT, Versioned::LIVE);
        return true;
    }

    /**
     * Get list of File dataobjects to import
     *
     * @return DataList
     */
    protected function getFileQuery()
    {
        // Select all records which have a Filename value, but not FileFilename.
        /** @skipUpgrade */
        return File::get()
            ->exclude('ClassName', ['SilverStripe\\Assets\\Folder', 'Folder'])
            ->filter('FileFilename', array('', null))
            ->where('"File"."Filename" IS NOT NULL AND "File"."Filename" != \'\''); // Non-orm field
    }

    /**
     * Get map of File IDs to legacy filenames
     *
     * @return array
     */
    protected function getFilenameArray()
    {
        // Convert original query, ensuring the legacy "Filename" is included in the result
        /** @skipUpgrade */
        return $this
            ->getFileQuery()
            ->dataQuery()
            ->selectFromTable('File', array('ID', 'Filename'))
            ->execute()
            ->map(); // map ID to Filename
    }
}