<?php

/**
 * Validator provides input validation with chainable rules
 */
class Validator
{
    private array $errors = [];
    private array $data = [];
    private array $rules = [];
    private array $messages = [];

    /**
     * Custom validation rules registry
     */
    private static array $customRules = [];

    /**
     * validate performs validation on data with given rules
     */
    public function validate(array $data, array $rules, array $messages = []): bool
    {
        $this->data = $data;
        $this->rules = $rules;
        $this->messages = $messages;
        $this->errors = [];

        foreach ($rules as $field => $fieldRules) {
            $this->validateField($field, $fieldRules);
        }

        return empty($this->errors);
    }

    /**
     * validateField validates a single field against its rules
     */
    private function validateField(string $field, string|array $rules): void
    {
        $rules = is_string($rules) ? explode('|', $rules) : $rules;
        $value = $this->getValue($field);

        foreach ($rules as $rule) {
            $this->applyRule($field, $value, $rule);
        }
    }

    /**
     * getValue gets a value from data using dot notation
     */
    private function getValue(string $field): mixed
    {
        $keys = explode('.', $field);
        $value = $this->data;

        foreach ($keys as $key) {
            if (!is_array($value) || !array_key_exists($key, $value)) {
                return null;
            }
            $value = $value[$key];
        }

        return $value;
    }

    /**
     * applyRule applies a single validation rule
     */
    private function applyRule(string $field, mixed $value, string $rule): void
    {
        $parts = explode(':', $rule, 2);
        $ruleName = $parts[0];
        $parameters = isset($parts[1]) ? explode(',', $parts[1]) : [];

        $passes = match($ruleName) {
            'required' => $this->validateRequired($value),
            'email' => $this->validateEmail($value),
            'url' => $this->validateUrl($value),
            'alpha' => $this->validateAlpha($value),
            'alphaNum' => $this->validateAlphaNum($value),
            'numeric' => $this->validateNumeric($value),
            'integer' => $this->validateInteger($value),
            'float' => $this->validateFloat($value),
            'boolean' => $this->validateBoolean($value),
            'array' => $this->validateArray($value),
            'json' => $this->validateJson($value),
            'date' => $this->validateDate($value),
            'min' => $this->validateMin($value, $parameters[0] ?? 0),
            'max' => $this->validateMax($value, $parameters[0] ?? 0),
            'between' => $this->validateBetween($value, $parameters[0] ?? 0, $parameters[1] ?? 0),
            'length' => $this->validateLength($value, $parameters[0] ?? 0),
            'in' => $this->validateIn($value, $parameters),
            'notIn' => $this->validateNotIn($value, $parameters),
            'regex' => $this->validateRegex($value, $parameters[0] ?? ''),
            'confirmed' => $this->validateConfirmed($field, $value),
            'unique' => $this->validateUnique($value, $parameters),
            'exists' => $this->validateExists($value, $parameters),
            default => $this->applyCustomRule($ruleName, $value, $parameters)
        };

        if (!$passes) {
            $this->addError($field, $ruleName, $parameters);
        }
    }

    /**
     * Validation rule methods
     */
    private function validateRequired(mixed $value): bool
    {
        if ($value === null) return false;
        if (is_string($value) && trim($value) === '') return false;
        if (is_array($value) && empty($value)) return false;
        return true;
    }

    private function validateEmail(mixed $value): bool
    {
        if (!is_string($value)) return false;
        return filter_var($value, FILTER_VALIDATE_EMAIL) !== false;
    }

    private function validateUrl(mixed $value): bool
    {
        if (!is_string($value)) return false;
        return filter_var($value, FILTER_VALIDATE_URL) !== false;
    }

    private function validateAlpha(mixed $value): bool
    {
        if (!is_string($value)) return false;
        return ctype_alpha($value);
    }

    private function validateAlphaNum(mixed $value): bool
    {
        if (!is_string($value)) return false;
        return ctype_alnum($value);
    }

    private function validateNumeric(mixed $value): bool
    {
        return is_numeric($value);
    }

    private function validateInteger(mixed $value): bool
    {
        return filter_var($value, FILTER_VALIDATE_INT) !== false;
    }

    private function validateFloat(mixed $value): bool
    {
        return filter_var($value, FILTER_VALIDATE_FLOAT) !== false;
    }

    private function validateBoolean(mixed $value): bool
    {
        return in_array($value, [true, false, 0, 1, '0', '1', 'true', 'false'], true);
    }

    private function validateArray(mixed $value): bool
    {
        return is_array($value);
    }

    private function validateJson(mixed $value): bool
    {
        if (!is_string($value)) return false;
        json_decode($value);
        return json_last_error() === JSON_ERROR_NONE;
    }

    private function validateDate(mixed $value): bool
    {
        if (!is_string($value)) return false;
        $date = date_parse($value);
        return $date['error_count'] === 0 && $date['warning_count'] === 0;
    }

    private function validateMin(mixed $value, mixed $min): bool
    {
        if (is_numeric($value)) return $value >= $min;
        if (is_string($value)) return strlen($value) >= $min;
        if (is_array($value)) return count($value) >= $min;
        return false;
    }

    private function validateMax(mixed $value, mixed $max): bool
    {
        if (is_numeric($value)) return $value <= $max;
        if (is_string($value)) return strlen($value) <= $max;
        if (is_array($value)) return count($value) <= $max;
        return false;
    }

    private function validateBetween(mixed $value, mixed $min, mixed $max): bool
    {
        return $this->validateMin($value, $min) && $this->validateMax($value, $max);
    }

    private function validateLength(mixed $value, mixed $length): bool
    {
        if (is_string($value)) return strlen($value) == $length;
        if (is_array($value)) return count($value) == $length;
        return false;
    }

    private function validateIn(mixed $value, array $values): bool
    {
        return in_array($value, $values, true);
    }

    private function validateNotIn(mixed $value, array $values): bool
    {
        return !in_array($value, $values, true);
    }

    private function validateRegex(mixed $value, string $pattern): bool
    {
        if (!is_string($value)) return false;
        return preg_match($pattern, $value) === 1;
    }

    private function validateConfirmed(string $field, mixed $value): bool
    {
        $confirmField = $field . '_confirmation';
        return $value === $this->getValue($confirmField);
    }

    private function validateUnique(mixed $value, array $parameters): bool
    {
        // Placeholder for database uniqueness check
        // Would require database connection in real implementation
        return true;
    }

    private function validateExists(mixed $value, array $parameters): bool
    {
        // Placeholder for database existence check
        // Would require database connection in real implementation
        return true;
    }

    /**
     * applyCustomRule applies a custom validation rule
     */
    private function applyCustomRule(string $ruleName, mixed $value, array $parameters): bool
    {
        if (!isset(self::$customRules[$ruleName])) {
            return true; // Unknown rules pass by default
        }

        return call_user_func(self::$customRules[$ruleName], $value, $parameters, $this->data);
    }

    /**
     * addError adds a validation error
     */
    private function addError(string $field, string $rule, array $parameters = []): void
    {
        $message = $this->messages["$field.$rule"]
            ?? $this->messages[$rule]
            ?? $this->getDefaultMessage($field, $rule, $parameters);

        if (!isset($this->errors[$field])) {
            $this->errors[$field] = [];
        }

        $this->errors[$field][] = $message;
    }

    /**
     * getDefaultMessage gets a default error message
     */
    private function getDefaultMessage(string $field, string $rule, array $parameters): string
    {
        $fieldName = str_replace('_', ' ', $field);

        return match($rule) {
            'required' => "The {$fieldName} field is required.",
            'email' => "The {$fieldName} must be a valid email address.",
            'url' => "The {$fieldName} must be a valid URL.",
            'alpha' => "The {$fieldName} may only contain letters.",
            'alphaNum' => "The {$fieldName} may only contain letters and numbers.",
            'numeric' => "The {$fieldName} must be a number.",
            'integer' => "The {$fieldName} must be an integer.",
            'float' => "The {$fieldName} must be a float.",
            'boolean' => "The {$fieldName} must be a boolean.",
            'array' => "The {$fieldName} must be an array.",
            'json' => "The {$fieldName} must be valid JSON.",
            'date' => "The {$fieldName} must be a valid date.",
            'min' => "The {$fieldName} must be at least {$parameters[0]}.",
            'max' => "The {$fieldName} must not be greater than {$parameters[0]}.",
            'between' => "The {$fieldName} must be between {$parameters[0]} and {$parameters[1]}.",
            'length' => "The {$fieldName} must be exactly {$parameters[0]} characters.",
            'in' => "The selected {$fieldName} is invalid.",
            'notIn' => "The selected {$fieldName} is invalid.",
            'regex' => "The {$fieldName} format is invalid.",
            'confirmed' => "The {$fieldName} confirmation does not match.",
            'unique' => "The {$fieldName} has already been taken.",
            'exists' => "The selected {$fieldName} is invalid.",
            default => "The {$fieldName} is invalid."
        };
    }

    /**
     * errors returns all validation errors
     */
    public function errors(): array
    {
        return $this->errors;
    }

    /**
     * failed checks if validation failed
     */
    public function failed(): bool
    {
        return !empty($this->errors);
    }

    /**
     * passed checks if validation passed
     */
    public function passed(): bool
    {
        return empty($this->errors);
    }

    /**
     * firstError gets the first error message
     */
    public function firstError(string $field = null): ?string
    {
        if ($field) {
            return $this->errors[$field][0] ?? null;
        }

        foreach ($this->errors as $errors) {
            if (!empty($errors)) {
                return $errors[0];
            }
        }

        return null;
    }

    /**
     * extend adds a custom validation rule
     */
    public static function extend(string $name, callable $callback): void
    {
        self::$customRules[$name] = $callback;
    }
}