app/api/includes/Validator.php

<?php

/**
 * Validacni helper pro API vstupy.
 *
 * Pouziti:
 *   $v = new Validator($input);
 *   $v->required('name')->string('name', 1, 255);
 *   $v->required('email')->email('email');
 *   $v->int('amount', 0, 1000000);
 *   $v->in('status', ['active', 'inactive']);
 *   if ($v->fails()) errorResponse($v->firstError());
 */

declare(strict_types=1);

class Validator
{
    /** @var array<string, mixed> */
    private array $data;

    /** @var array<string, string> */
    private array $errors = [];

    /** @param array<string, mixed> $data */
    public function __construct(array $data)
    {
        $this->data = $data;
    }

    public function required(string $field, string $label = ''): self
    {
        $value = $this->data[$field] ?? null;
        if ($value === null || $value === '') {
            $this->errors[$field] = ($label ?: $field) . ' je povinné pole';
        }
        return $this;
    }

    public function string(string $field, int $min = 0, int $max = 0, string $label = ''): self
    {
        $value = $this->data[$field] ?? null;
        if ($value === null || $value === '') {
            return $this;
        }
        if (!is_string($value)) {
            $this->errors[$field] = ($label ?: $field) . ' musí být text';
            return $this;
        }
        $len = mb_strlen($value);
        if ($min > 0 && $len < $min) {
            $this->errors[$field] = ($label ?: $field) . " musí mít alespoň {$min} znaků";
        } elseif ($max > 0 && $len > $max) {
            $this->errors[$field] = ($label ?: $field) . " nesmí překročit {$max} znaků";
        }
        return $this;
    }

    public function int(string $field, ?int $min = null, ?int $max = null, string $label = ''): self
    {
        $value = $this->data[$field] ?? null;
        if ($value === null || $value === '') {
            return $this;
        }
        if (!is_numeric($value)) {
            $this->errors[$field] = ($label ?: $field) . ' musí být číslo';
            return $this;
        }
        $intVal = (int) $value;
        if ($min !== null && $intVal < $min) {
            $this->errors[$field] = ($label ?: $field) . " musí být alespoň {$min}";
        } elseif ($max !== null && $intVal > $max) {
            $this->errors[$field] = ($label ?: $field) . " nesmí překročit {$max}";
        }
        return $this;
    }

    public function email(string $field, string $label = ''): self
    {
        $value = $this->data[$field] ?? null;
        if ($value === null || $value === '') {
            return $this;
        }
        if (!is_string($value) || !filter_var($value, FILTER_VALIDATE_EMAIL)) {
            $this->errors[$field] = ($label ?: $field) . ' musí být platný e-mail';
        }
        return $this;
    }

    /**
     * @param list<string> $allowed
     */
    public function in(string $field, array $allowed, string $label = ''): self
    {
        $value = $this->data[$field] ?? null;
        if ($value === null || $value === '') {
            return $this;
        }
        if (!in_array($value, $allowed, true)) {
            $this->errors[$field] = ($label ?: $field) . ' má neplatnou hodnotu';
        }
        return $this;
    }

    public function numeric(string $field, ?float $min = null, ?float $max = null, string $label = ''): self
    {
        $value = $this->data[$field] ?? null;
        if ($value === null || $value === '') {
            return $this;
        }
        if (!is_numeric($value)) {
            $this->errors[$field] = ($label ?: $field) . ' musí být číslo';
            return $this;
        }
        $numVal = (float) $value;
        if ($min !== null && $numVal < $min) {
            $this->errors[$field] = ($label ?: $field) . " musí být alespoň {$min}";
        } elseif ($max !== null && $numVal > $max) {
            $this->errors[$field] = ($label ?: $field) . " nesmí překročit {$max}";
        }
        return $this;
    }

    public function fails(): bool
    {
        return count($this->errors) > 0;
    }

    public function firstError(): string
    {
        return reset($this->errors) ?: '';
    }

    /** @return array<string, string> */
    public function errors(): array
    {
        return $this->errors;
    }
}