<?php
namespace Relay\Database;

use Relay\Support\RelayError;

final class CreateTable
{
    /** @return array{create: string, constraints: ?string} */
    public static function build(Db $db, string $table, string $as, string $final): array
    {
        $rows = $db->results('SHOW CREATE TABLE ' . Db::ident($table), ARRAY_N);
        $sql = (string) ($rows[0][1] ?? '');
        $head = 'CREATE TABLE ' . Db::ident($table);
        if (strpos($sql, $head) !== 0) {
            /* translators: %s: table name */
            throw new RelayError('db.show_create_failed', esc_html(sprintf(__('Could not read the structure of table %s.', 'siterelay'), $table)));
        }
        $sql = 'CREATE TABLE ' . Db::ident($as) . substr($sql, strlen($head));
        return self::split_constraints($sql, $final);
    }

    // Ported from WP Migrate 2.7.11 (GPL) Table::process_sql_constraint, simplified to line filtering.
    /** @return array{create: string, constraints: ?string} */
    public static function split_constraints(string $create, string $final): array
    {
        if (!preg_match('/\bCONSTRAINT\b|\bFOREIGN\s+KEY\b/i', $create)) {
            return ['create' => $create, 'constraints' => null];
        }
        $keep = [];
        $adds = [];
        foreach (explode("\n", $create) as $line) {
            if (preg_match('/^\s*(CONSTRAINT|FOREIGN\s+KEY)\b/i', $line)) {
                $adds[] = 'ADD ' . rtrim(trim($line), ',');
            } else {
                $keep[] = $line;
            }
        }
        if ($adds === []) {
            return ['create' => $create, 'constraints' => null];
        }
        for ($i = count($keep) - 1; $i > 0; $i--) {
            if (strpos(ltrim($keep[$i]), ')') === 0) {
                $keep[$i - 1] = rtrim($keep[$i - 1], ',');
                break;
            }
        }
        return [
            'create' => implode("\n", $keep),
            'constraints' => 'ALTER TABLE ' . Db::ident($final) . ' ' . implode(', ', $adds),
        ];
    }

    /** @return string[] names of FOREIGN KEY constraints added by an ALTER statement */
    public static function constraint_names(string $alter): array
    {
        preg_match_all('/ADD CONSTRAINT `((?:[^`]|``)+)` FOREIGN KEY/i', $alter, $m);
        return array_map(fn ($n) => str_replace('``', '`', $n), $m[1]);
    }
}