class PixQRGenerator {
    constructor() {
        this.initializePixInterface();
    }

    initializePixInterface() {
        // Listeners for realtime preview
        const fieldsToWatch = [
            'pix-key', 
            'pix-key-type',
            'pix-name', 
            'pix-city', 
            'pix-amount', 
            'pix-description', 
            'pix-txid'
        ];

        fieldsToWatch.forEach(fieldId => {
            const element = document.getElementById(fieldId);
            if (element) {
                element.addEventListener('input', () => this.updatePreview());
                element.addEventListener('change', () => this.updatePreview());
            }
        });
        
        // Add currency mask to amount field
        const amountInput = document.getElementById('pix-amount');
        if (amountInput) {
            amountInput.addEventListener('input', (e) => {
                let value = e.target.value.replace(/\D/g, '');
                if (value) {
                    value = (parseInt(value) / 100).toFixed(2) + '';
                    value = value.replace('.', ',');
                    value = value.replace(/(\d)(?=(\d{3})+(?!\d))/g, '$1.');
                    e.target.value = value;
                }
                this.updatePreview();
            });
        }
    }

    updatePreview() {
        const data = this.collectPixData();
        const previewElement = document.getElementById('pix-preview-text');
        
        if (previewElement) {
            if (!data.key || !data.name || !data.city) {
                previewElement.textContent = "Preencha os campos obrigatórios (Chave, Nome, Cidade) para ver o preview.";
                return;
            }
            
            try {
                const payload = this.generatePixPayload();
                previewElement.textContent = payload;
            } catch (e) {
                previewElement.textContent = "Erro ao gerar payload: " + e.message;
            }
        }
    }

    collectPixData() {
        return {
            keyType: document.getElementById('pix-key-type')?.value || 'cpf',
            key: document.getElementById('pix-key')?.value || '',
            name: document.getElementById('pix-name')?.value || '',
            city: document.getElementById('pix-city')?.value || '',
            amount: document.getElementById('pix-amount')?.value || '',
            description: document.getElementById('pix-description')?.value || '',
            txid: document.getElementById('pix-txid')?.value || ''
        };
    }

    validatePixData() {
        const data = this.collectPixData();
        const errors = [];

        if (!data.key.trim()) errors.push('Chave PIX é obrigatória');
        if (!data.name.trim()) errors.push('Nome do beneficiário é obrigatório');
        if (!data.city.trim()) errors.push('Cidade do beneficiário é obrigatória');
        
        if (data.name.length > 25) errors.push('Nome deve ter no máximo 25 caracteres');
        if (data.city.length > 15) errors.push('Cidade deve ter no máximo 15 caracteres (Regra do Banco Central)');

        if (data.amount) {
            // Remove thousands separators (.) and replace decimal comma (,) with dot (.)
            const amount = parseFloat(data.amount.replace(/\./g, '').replace(',', '.'));
            if (isNaN(amount) || amount <= 0) {
                errors.push('Valor deve ser um número maior que zero');
            }
        }

        return errors;
    }

    generateCRC16(payload) {
        let crc = 0xFFFF;
        const polynomial = 0x1021;

        for (let i = 0; i < payload.length; i++) {
            crc ^= payload.charCodeAt(i) << 8;
            for (let j = 0; j < 8; j++) {
                if ((crc & 0x8000) !== 0) {
                    crc = ((crc << 1) ^ polynomial) & 0xFFFF;
                } else {
                    crc = (crc << 1) & 0xFFFF;
                }
            }
        }
        
        return crc.toString(16).toUpperCase().padStart(4, '0');
    }

    formatField(id, value) {
        const valStr = value.toString();
        const len = valStr.length.toString().padStart(2, '0');
        return `${id}${len}${valStr}`;
    }
    
    formatKey(type, key) {
        if (!key) return '';
        const cleanKey = key.trim();
        
        switch(type) {
            case 'phone':
                // Remove non-digits
                let nums = cleanKey.replace(/\D/g, '');
                // If it starts with 55 and is long enough, keep it
                // If 10 or 11 digits (DDD+Number), add +55
                if ((nums.length === 10 || nums.length === 11) && !nums.startsWith('55')) {
                    return `+55${nums}`;
                }
                // If user typed 55..., ensure +
                if (nums.startsWith('55') && !cleanKey.startsWith('+')) {
                    return `+${nums}`;
                }
                // If user typed +..., keep it
                if (cleanKey.startsWith('+')) {
                    return cleanKey; // Assume correct
                }
                return `+${nums}`; // Fallback
                
            case 'cpf':
            case 'cnpj':
                // Numbers only
                return cleanKey.replace(/\D/g, '');
                
            case 'email':
                return cleanKey.toLowerCase();
                
            case 'random':
            default:
                return cleanKey;
        }
    }

    generatePixPayload() {
        const data = this.collectPixData();
        
        // Format key based on type
        const key = this.formatKey(data.keyType, data.key);
        
        const name = this.removeAccents(data.name.trim()).substring(0, 25);
        const city = this.removeAccents(data.city.trim()).substring(0, 15); // Standard limit 15 chars
        const amount = data.amount ? parseFloat(data.amount.replace(/\./g, '').replace(',', '.')).toFixed(2) : null;
        const description = this.removeAccents(data.description.trim()) || '';
        const txid = this.removeAccents(data.txid.trim()) || '***';

        let payload = this.formatField('00', '01');

        const gui = this.formatField('00', 'br.gov.bcb.pix');
        const keyField = this.formatField('01', key);
        
        // Field 26: Merchant Account Information
        // Subfields: 00 (GUI), 01 (Key), 02 (Description - optional/standard varies)
        // Standard EMVCo for PIX puts Description in field 02 of ID 26?
        // Actually, BR Code standard puts "InfoAdicional" in Field 26, ID 02.
        
        let merchantAccountInfo = gui + keyField;
        if (description) {
             merchantAccountInfo += this.formatField('02', description);
        }
        payload += this.formatField('26', merchantAccountInfo);

        payload += this.formatField('52', '0000'); // Merchant Category Code
        payload += this.formatField('53', '986');  // Transaction Currency (BRL)

        if (amount) {
            payload += this.formatField('54', amount); // Transaction Amount
        }

        payload += this.formatField('58', 'BR'); // Country Code
        payload += this.formatField('59', name); // Merchant Name
        payload += this.formatField('60', city); // Merchant City

        // Field 62: Additional Data Field Template
        // Subfields: 05 (Reference Label / TxID)
        const txidField = this.formatField('05', txid);
        payload += this.formatField('62', txidField);

        payload += '6304'; // CRC16 ID + Length

        const crc = this.generateCRC16(payload);
        
        return payload + crc;
    }

    removeAccents(str) {
        return str.normalize("NFD").replace(/[\u0300-\u036f]/g, "");
    }
}