import { Logger } from '../../core/logger.js';

export class FormValidator {
    constructor(form) {
        this.form = form;
        this.errors = new Map();
    }

    static create(form) {
        return new FormValidator(form);
    }

    validate() {
        this.errors.clear();
        const fields = this.form.querySelectorAll('input, textarea, select');
        
        for (const field of fields) {
            if (field.type === 'hidden' || field.disabled) continue;
            
            this.validateField(field);
        }
        
        return this.errors.size === 0;
    }

    validateField(field) {
        const value = field.value;
        const fieldName = field.name;
        
        // HTML5 required attribute
        if (field.hasAttribute('required') && (!value || value.trim() === '')) {
            this.errors.set(fieldName, this.getErrorMessage(field, 'valueMissing') || `${this.getFieldLabel(field)} ist erforderlich`);
            return;
        }
        
        // Skip further validation if field is empty and not required
        if (!value || value.trim() === '') return;
        
        // HTML5 type validation
        if (field.type === 'email' && !this.isValidEmail(value)) {
            this.errors.set(fieldName, this.getErrorMessage(field, 'typeMismatch') || 'Bitte geben Sie eine gültige E-Mail-Adresse ein');
            return;
        }
        
        if (field.type === 'url' && !this.isValidUrl(value)) {
            this.errors.set(fieldName, this.getErrorMessage(field, 'typeMismatch') || 'Bitte geben Sie eine gültige URL ein');
            return;
        }
        
        // HTML5 minlength attribute
        const minLength = field.getAttribute('minlength');
        if (minLength && value.length < parseInt(minLength)) {
            this.errors.set(fieldName, this.getErrorMessage(field, 'tooShort') || `Mindestens ${minLength} Zeichen erforderlich`);
            return;
        }
        
        // HTML5 maxlength attribute (usually enforced by browser, but for safety)
        const maxLength = field.getAttribute('maxlength');
        if (maxLength && value.length > parseInt(maxLength)) {
            this.errors.set(fieldName, this.getErrorMessage(field, 'tooLong') || `Maximal ${maxLength} Zeichen erlaubt`);
            return;
        }
        
        // HTML5 min/max for number inputs
        if (field.type === 'number') {
            const min = field.getAttribute('min');
            const max = field.getAttribute('max');
            const numValue = parseFloat(value);
            
            if (min && numValue < parseFloat(min)) {
                this.errors.set(fieldName, this.getErrorMessage(field, 'rangeUnderflow') || `Wert muss mindestens ${min} sein`);
                return;
            }
            
            if (max && numValue > parseFloat(max)) {
                this.errors.set(fieldName, this.getErrorMessage(field, 'rangeOverflow') || `Wert darf maximal ${max} sein`);
                return;
            }
        }
        
        // HTML5 pattern attribute
        const pattern = field.getAttribute('pattern');
        if (pattern) {
            const regex = new RegExp(pattern);
            if (!regex.test(value)) {
                this.errors.set(fieldName, this.getErrorMessage(field, 'patternMismatch') || 'Ungültiges Format');
                return;
            }
        }
        
        // Custom validation via data-validate attribute
        const customValidation = field.getAttribute('data-validate');
        if (customValidation) {
            const result = this.runCustomValidation(customValidation, value, field);
            if (!result.valid) {
                this.errors.set(fieldName, result.message);
                return;
            }
        }
    }

    runCustomValidation(validationType, value, field) {
        switch (validationType) {
            case 'phone':
                const phoneRegex = /^[\+]?[0-9\s\-\(\)]{10,}$/;
                return {
                    valid: phoneRegex.test(value),
                    message: 'Bitte geben Sie eine gültige Telefonnummer ein'
                };
                
            case 'postal-code-de':
                const postalRegex = /^[0-9]{5}$/;
                return {
                    valid: postalRegex.test(value),
                    message: 'Bitte geben Sie eine gültige Postleitzahl ein'
                };
                
            case 'no-html':
                const hasHtml = /<[^>]*>/g.test(value);
                return {
                    valid: !hasHtml,
                    message: 'HTML-Code ist nicht erlaubt'
                };
                
            default:
                Logger.warn(`Unknown custom validation: ${validationType}`);
                return { valid: true, message: '' };
        }
    }

    isValidEmail(email) {
        return /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email);
    }

    isValidUrl(url) {
        try {
            new URL(url);
            return true;
        } catch {
            return false;
        }
    }

    getFieldLabel(field) {
        const label = this.form.querySelector(`label[for="${field.id}"]`) || 
                     this.form.querySelector(`label:has([name="${field.name}"])`);
        
        return label ? label.textContent.trim().replace(':', '') : field.name;
    }

    getErrorMessage(field, validityType) {
        // Check for custom error messages via data-error-* attributes
        const customMessage = field.getAttribute(`data-error-${validityType}`) || 
                             field.getAttribute('data-error');
        
        return customMessage;
    }

    getErrors() {
        return Object.fromEntries(this.errors);
    }

    getFieldError(fieldName) {
        return this.errors.get(fieldName);
    }

    hasErrors() {
        return this.errors.size > 0;
    }

    clearErrors() {
        this.errors.clear();
    }

    // Check HTML5 validity API as fallback
    validateWithHTML5() {
        const isValid = this.form.checkValidity();
        
        if (!isValid) {
            const fields = this.form.querySelectorAll('input, textarea, select');
            for (const field of fields) {
                if (!field.validity.valid) {
                    this.errors.set(field.name, field.validationMessage);
                }
            }
        }
        
        return isValid;
    }
}