<?php

namespace App\Console\Commands;

use Illuminate\Console\Command;
use Illuminate\Support\Facades\Artisan;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Schema;
use RuntimeException;

class ImportSqliteDatabase extends Command
{
    protected $signature = 'db:import-sqlite
                            {path=database/database.sqlite : Path to the legacy SQLite database}
                            {--chunk=500 : Rows copied per batch}';

    protected $description = 'Import all compatible data from the legacy SQLite database into an empty MySQL database';

    public function handle(): int
    {
        if (DB::getDefaultConnection() !== 'mysql') {
            $this->error('The default DB_CONNECTION must be mysql.');

            return self::FAILURE;
        }

        $path = $this->absolutePath((string) $this->argument('path'));

        if (! is_file($path)) {
            $this->error("SQLite database not found: {$path}");

            return self::FAILURE;
        }

        $chunkSize = max(1, (int) $this->option('chunk'));
        config(['database.connections.sqlite_import.database' => $path]);
        DB::purge('sqlite_import');

        $migrationExitCode = Artisan::call('migrate', ['--force' => true]);
        $this->output->write(Artisan::output());

        if ($migrationExitCode !== self::SUCCESS) {
            $this->error('MySQL migrations failed; no SQLite data was copied.');

            return self::FAILURE;
        }

        $sourceTables = array_map(
            static fn (object $table): string => $table->name,
            DB::connection('sqlite_import')->select(
                "SELECT name FROM sqlite_master WHERE type = 'table' AND name NOT LIKE 'sqlite_%'"
            )
        );
        $targetTables = array_map(
            static fn (object $table): string => $table->name,
            DB::connection('mysql')->select(
                "SELECT table_name AS name FROM information_schema.tables WHERE table_schema = DATABASE() AND table_type = 'BASE TABLE'"
            )
        );
        $tables = array_values(array_intersect($sourceTables, $targetTables));
        $tables = array_values(array_diff($tables, ['migrations', 'sqlite_sequence']));

        $this->assertTargetIsEmpty($tables);
        DB::connection('mysql')->statement('SET FOREIGN_KEY_CHECKS=0');

        try {
            foreach ($tables as $table) {
                $copied = $this->copyTable($table, $chunkSize);
                $this->line("{$table}: {$copied} rows");
            }
        } finally {
            DB::connection('mysql')->statement('SET FOREIGN_KEY_CHECKS=1');
        }

        $this->newLine();
        $this->info('SQLite data imported into MySQL successfully. The SQLite file was left unchanged.');

        return self::SUCCESS;
    }

    private function assertTargetIsEmpty(array $tables): void
    {
        foreach ($tables as $table) {
            if (DB::connection('mysql')->table($table)->exists()) {
                throw new RuntimeException(
                    "MySQL table [{$table}] is not empty. Import into a new database to prevent duplicate or overwritten data."
                );
            }
        }
    }

    private function copyTable(string $table, int $chunkSize): int
    {
        $sourceColumns = Schema::connection('sqlite_import')->getColumnListing($table);
        $targetColumns = Schema::connection('mysql')->getColumnListing($table);
        $columns = array_values(array_intersect($sourceColumns, $targetColumns));

        if ($columns === []) {
            $this->warn("{$table}: skipped because it has no compatible columns");

            return 0;
        }

        $copied = 0;
        DB::connection('sqlite_import')->table($table)->select($columns)->orderBy($columns[0])->chunk(
            $chunkSize,
            function ($rows) use ($table, $columns, &$copied): void {
                $payload = $rows->map(static function ($row) use ($columns): array {
                    $values = (array) $row;

                    return array_intersect_key($values, array_flip($columns));
                })->all();

                if ($payload !== []) {
                    DB::connection('mysql')->table($table)->insert($payload);
                    $copied += count($payload);
                }
            }
        );

        return $copied;
    }

    private function absolutePath(string $path): string
    {
        if (preg_match('/^(?:[A-Za-z]:[\\\\\/]|\/)/', $path) === 1) {
            return $path;
        }

        return base_path($path);
    }
}