implement chat

js/components/chat-widget.js

@@ -0,0 +1,287 @@
+/**
+ * Chat Widget Component
+ * Embedded chat for buyer-seller communication
+ */
+
+import { t, i18n } from '../i18n.js';
+import { chatService } from '../services/chat.js';
+import { cryptoService } from '../services/crypto.js';
+
+class ChatWidget extends HTMLElement {
+    static get observedAttributes() {
+        return ['listing-id', 'recipient-id', 'recipient-key', 'recipient-name'];
+    }
+
+    constructor() {
+        super();
+        this.chat = null;
+        this.messages = [];
+        this.unsubscribe = null;
+    }
+
+    async connectedCallback() {
+        await cryptoService.ready;
+        
+        this.listingId = this.getAttribute('listing-id');
+        this.recipientId = this.getAttribute('recipient-id');
+        this.recipientKey = this.getAttribute('recipient-key');
+        this.recipientName = this.getAttribute('recipient-name') || 'Seller';
+        
+        if (this.listingId && this.recipientId && this.recipientKey) {
+            this.chat = chatService.getOrCreateChat(
+                this.recipientId,
+                this.recipientKey,
+                this.listingId
+            );
+            await this.loadMessages();
+        }
+        
+        this.render();
+        this.setupEventListeners();
+        
+        this.unsubscribe = chatService.subscribe(() => this.refreshMessages());
+        this.i18nUnsubscribe = i18n.subscribe(() => this.render());
+    }
+
+    disconnectedCallback() {
+        if (this.unsubscribe) this.unsubscribe();
+        if (this.i18nUnsubscribe) this.i18nUnsubscribe();
+    }
+
+    async loadMessages() {
+        if (!this.chat) return;
+        this.messages = await chatService.getMessages(this.chat.id, this.recipientKey);
+    }
+
+    async refreshMessages() {
+        await this.loadMessages();
+        this.renderMessages();
+        this.scrollToBottom();
+    }
+
+    render() {
+        this.innerHTML = /* html */`
+            <div class="chat-widget">
+                <div class="chat-header">
+                    <span class="chat-recipient">${this.escapeHtml(this.recipientName)}</span>
+                    <span class="chat-encrypted" title="${t('chat.encrypted')}">🔒</span>
+                </div>
+                
+                <div class="chat-messages" id="chat-messages">
+                    ${this.renderMessagesHtml()}
+                </div>
+                
+                <form class="chat-input" id="chat-form">
+                    <input 
+                        type="text" 
+                        id="message-input" 
+                        placeholder="${t('chat.placeholder')}"
+                        autocomplete="off"
+                    >
+                    <button type="submit" class="btn btn-primary">
+                        <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+                            <line x1="22" y1="2" x2="11" y2="13"></line>
+                            <polygon points="22 2 15 22 11 13 2 9 22 2"></polygon>
+                        </svg>
+                    </button>
+                </form>
+            </div>
+        `;
+        
+        this.setupEventListeners();
+        this.scrollToBottom();
+    }
+
+    renderMessagesHtml() {
+        if (this.messages.length === 0) {
+            return /* html */`
+                <div class="chat-empty">
+                    <p>${t('chat.startConversation')}</p>
+                </div>
+            `;
+        }
+        
+        return this.messages.map(msg => /* html */`
+            <div class="chat-message ${msg.isOwn ? 'own' : 'other'}">
+                <div class="message-bubble">
+                    <p>${this.escapeHtml(msg.text)}</p>
+                    <span class="message-time">${this.formatTime(msg.timestamp)}</span>
+                </div>
+            </div>
+        `).join('');
+    }
+
+    renderMessages() {
+        const container = this.querySelector('#chat-messages');
+        if (container) {
+            container.innerHTML = this.renderMessagesHtml();
+        }
+    }
+
+    setupEventListeners() {
+        const form = this.querySelector('#chat-form');
+        form?.addEventListener('submit', (e) => this.handleSubmit(e));
+    }
+
+    async handleSubmit(e) {
+        e.preventDefault();
+        
+        const input = this.querySelector('#message-input');
+        const text = input?.value.trim();
+        
+        if (!text || !this.chat) return;
+        
+        input.value = '';
+        
+        await chatService.sendMessage(
+            this.chat.id,
+            this.recipientKey,
+            text
+        );
+    }
+
+    scrollToBottom() {
+        const container = this.querySelector('#chat-messages');
+        if (container) {
+            container.scrollTop = container.scrollHeight;
+        }
+    }
+
+    formatTime(timestamp) {
+        const date = new Date(timestamp);
+        return date.toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' });
+    }
+
+    escapeHtml(text) {
+        const div = document.createElement('div');
+        div.textContent = text;
+        return div.innerHTML;
+    }
+}
+
+customElements.define('chat-widget', ChatWidget);
+
+const style = document.createElement('style');
+style.textContent = /* css */`
+    chat-widget {
+        display: block;
+    }
+    
+    chat-widget .chat-widget {
+        display: flex;
+        flex-direction: column;
+        height: 400px;
+        border: 1px solid var(--color-border);
+        border-radius: var(--radius-lg);
+        overflow: hidden;
+        background: var(--color-bg);
+    }
+    
+    chat-widget .chat-header {
+        display: flex;
+        align-items: center;
+        justify-content: space-between;
+        padding: var(--space-md);
+        background: var(--color-bg-secondary);
+        border-bottom: 1px solid var(--color-border);
+    }
+    
+    chat-widget .chat-recipient {
+        font-weight: var(--font-weight-medium);
+    }
+    
+    chat-widget .chat-encrypted {
+        font-size: var(--font-size-sm);
+        cursor: help;
+    }
+    
+    chat-widget .chat-messages {
+        flex: 1;
+        overflow-y: auto;
+        padding: var(--space-md);
+        display: flex;
+        flex-direction: column;
+        gap: var(--space-sm);
+    }
+    
+    chat-widget .chat-empty {
+        flex: 1;
+        display: flex;
+        align-items: center;
+        justify-content: center;
+        color: var(--color-text-muted);
+        text-align: center;
+    }
+    
+    chat-widget .chat-message {
+        display: flex;
+        max-width: 80%;
+    }
+    
+    chat-widget .chat-message.own {
+        align-self: flex-end;
+    }
+    
+    chat-widget .chat-message.other {
+        align-self: flex-start;
+    }
+    
+    chat-widget .message-bubble {
+        padding: var(--space-sm) var(--space-md);
+        border-radius: var(--radius-lg);
+        position: relative;
+    }
+    
+    chat-widget .chat-message.own .message-bubble {
+        background: var(--color-primary);
+        color: white;
+        border-bottom-right-radius: var(--radius-sm);
+    }
+    
+    chat-widget .chat-message.other .message-bubble {
+        background: var(--color-bg-secondary);
+        border-bottom-left-radius: var(--radius-sm);
+    }
+    
+    chat-widget .message-bubble p {
+        margin: 0;
+        word-break: break-word;
+    }
+    
+    chat-widget .message-time {
+        display: block;
+        font-size: var(--font-size-xs);
+        opacity: 0.7;
+        margin-top: var(--space-xs);
+    }
+    
+    chat-widget .chat-input {
+        display: flex;
+        gap: var(--space-sm);
+        padding: var(--space-md);
+        border-top: 1px solid var(--color-border);
+        background: var(--color-bg-secondary);
+    }
+    
+    chat-widget .chat-input input {
+        flex: 1;
+        padding: var(--space-sm) var(--space-md);
+        border: 1px solid var(--color-border);
+        border-radius: var(--radius-md);
+        background: var(--color-bg);
+        font-size: var(--font-size-base);
+    }
+    
+    chat-widget .chat-input input:focus {
+        outline: none;
+        border-color: var(--color-primary);
+    }
+    
+    chat-widget .chat-input button {
+        padding: var(--space-sm);
+        border-radius: var(--radius-md);
+    }
+`;
+document.head.appendChild(style);
+
+export { ChatWidget };

js/components/pages/page-listing.js

@@ -1,5 +1,6 @@
 import { t, i18n } from '../../i18n.js';
 import { getListingById } from '../../data/mock-listings.js';
+import '../chat-widget.js';
 
 class PageListing extends HTMLElement {
     constructor() {
@@ -106,23 +107,39 @@ class PageListing extends HTMLElement {
                         <line x1="6" y1="6" x2="18" y2="18"></line>
                     </svg>
                 </button>
-                <h2>${t('listing.contactSeller')}</h2>
-                <p class="dialog-subtitle">${t('listing.paymentInfo')}</p>
                 
-                <div class="monero-section">
-                    <label>${t('listing.moneroAddress')}</label>
-                    <div class="monero-address">
-                        <code id="monero-addr">${this.listing.seller.moneroAddress || '888tNkZrPN6JsEgekjMnABU4TBzc2Dt29EPAvkRxbANsAnjyPbb3iQ1YBRk1UXcdRsiKc9dhwMVgN5S9cQUiyoogDavup3H'}</code>
-                        <button class="btn btn-outline btn-copy" id="copy-btn" title="${t('listing.copyAddress')}">
-                            <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
-                                <rect x="9" y="9" width="13" height="13" rx="2" ry="2"></rect>
-                                <path d="M5 15H4a2 2 0 0 1-2-2V4a2 2 0 0 1 2-2h9a2 2 0 0 1 2 2v1"></path>
-                            </svg>
-                        </button>
-                    </div>
+                <div class="dialog-tabs">
+                    <button class="tab-btn active" data-tab="chat">${t('chat.title')}</button>
+                    <button class="tab-btn" data-tab="payment">${t('listing.moneroAddress')}</button>
                 </div>
                 
-                <p class="dialog-hint">${t('listing.contactHint')}</p>
+                <div class="tab-content" id="tab-chat">
+                    <chat-widget
+                        listing-id="${this.listing.id}"
+                        recipient-id="${this.listing.seller.name}"
+                        recipient-key="${this.listing.seller.publicKey || 'demo-key-' + this.listing.id}"
+                        recipient-name="${this.escapeHtml(this.listing.seller.name)}"
+                    ></chat-widget>
+                </div>
+                
+                <div class="tab-content hidden" id="tab-payment">
+                    <p class="dialog-subtitle">${t('listing.paymentInfo')}</p>
+                    
+                    <div class="monero-section">
+                        <label>${t('listing.moneroAddress')}</label>
+                        <div class="monero-address">
+                            <code id="monero-addr">${this.listing.seller.moneroAddress || '888tNkZrPN6JsEgekjMnABU4TBzc2Dt29EPAvkRxbANsAnjyPbb3iQ1YBRk1UXcdRsiKc9dhwMVgN5S9cQUiyoogDavup3H'}</code>
+                            <button class="btn btn-outline btn-copy" id="copy-btn" title="${t('listing.copyAddress')}">
+                                <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+                                    <rect x="9" y="9" width="13" height="13" rx="2" ry="2"></rect>
+                                    <path d="M5 15H4a2 2 0 0 1-2-2V4a2 2 0 0 1 2-2h9a2 2 0 0 1 2 2v1"></path>
+                                </svg>
+                            </button>
+                        </div>
+                    </div>
+                    
+                    <p class="dialog-hint">${t('listing.contactHint')}</p>
+                </div>
             </dialog>
         `;
         
@@ -134,6 +151,7 @@ class PageListing extends HTMLElement {
         const dialog = this.querySelector('#contact-dialog');
         const closeBtn = this.querySelector('#dialog-close');
         const copyBtn = this.querySelector('#copy-btn');
+        const tabBtns = this.querySelectorAll('.tab-btn');
         
         contactBtn?.addEventListener('click', () => {
             dialog?.showModal();
@@ -157,6 +175,19 @@ class PageListing extends HTMLElement {
                 setTimeout(() => copyBtn.classList.remove('copied'), 2000);
             }
         });
+        
+        tabBtns.forEach(btn => {
+            btn.addEventListener('click', () => {
+                const tab = btn.dataset.tab;
+                
+                tabBtns.forEach(b => b.classList.remove('active'));
+                btn.classList.add('active');
+                
+                this.querySelectorAll('.tab-content').forEach(content => {
+                    content.classList.toggle('hidden', content.id !== `tab-${tab}`);
+                });
+            });
+        });
     }
 
     escapeHtml(text) {
@@ -292,6 +323,37 @@ style.textContent = /* css */`
         background: var(--color-overlay);
     }
     
+    page-listing .dialog-tabs {
+        display: flex;
+        gap: var(--space-sm);
+        margin-bottom: var(--space-lg);
+        border-bottom: 1px solid var(--color-border);
+        padding-bottom: var(--space-sm);
+    }
+    
+    page-listing .tab-btn {
+        padding: var(--space-sm) var(--space-md);
+        font-size: var(--font-size-sm);
+        font-weight: var(--font-weight-medium);
+        color: var(--color-text-muted);
+        border-radius: var(--radius-md);
+        transition: all var(--transition-fast);
+    }
+    
+    page-listing .tab-btn:hover {
+        color: var(--color-text);
+        background: var(--color-bg-secondary);
+    }
+    
+    page-listing .tab-btn.active {
+        color: var(--color-primary);
+        background: var(--color-primary-light);
+    }
+    
+    page-listing .tab-content.hidden {
+        display: none;
+    }
+    
     page-listing .dialog-close {
         position: absolute;
         top: var(--space-md);

js/data/mock-listings.js

@@ -11,7 +11,8 @@ export const mockListings = [
         seller: {
             name: 'Max M.',
             memberSince: '2023',
-            moneroAddress: '888tNkZrPN6JsEgekjMnABU4TBzc2Dt29EPAvkRxbANsAnjyPbb3iQ1YBRk1UXcdRsiKc9dhwMVgN5S9cQUiyoogDavup3H'
+            moneroAddress: '888tNkZrPN6JsEgekjMnABU4TBzc2Dt29EPAvkRxbANsAnjyPbb3iQ1YBRk1UXcdRsiKc9dhwMVgN5S9cQUiyoogDavup3H',
+            publicKey: 'dGVzdC1wdWJsaWMta2V5LW1heC1tLTEyMzQ1Njc4OTA='
         }
     },
     {
@@ -26,7 +27,8 @@ export const mockListings = [
         seller: {
             name: 'Anna K.',
             memberSince: '2024',
-            moneroAddress: '47sghzufGhJJDQEbScMCwVBimTuq6L5JiRixD8VeGbpjCTA12GwZVPWzjmpfLDJNDAWvuNDAWvuNDAWvuNDAWvuN'
+            moneroAddress: '47sghzufGhJJDQEbScMCwVBimTuq6L5JiRixD8VeGbpjCTA12GwZVPWzjmpfLDJNDAWvuNDAWvuNDAWvuNDAWvuN',
+            publicKey: 'dGVzdC1wdWJsaWMta2V5LWFubmEtay0xMjM0NTY3ODkw'
         }
     },
     {
@@ -41,7 +43,8 @@ export const mockListings = [
         seller: {
             name: 'Thomas B.',
             memberSince: '2022',
-            moneroAddress: '44AFFq5kSiGBoZ4NMDwYtN18obc8AemS33DBLWs3H7otXft3XjrpDtQGv7SqSsaBYBb98uNbr2VBBEt7f2wfn3RVGQBEP3A'
+            moneroAddress: '44AFFq5kSiGBoZ4NMDwYtN18obc8AemS33DBLWs3H7otXft3XjrpDtQGv7SqSsaBYBb98uNbr2VBBEt7f2wfn3RVGQBEP3A',
+            publicKey: 'dGVzdC1wdWJsaWMta2V5LXRob21hcy1iLTEyMzQ1Njc='
         }
     },
     {
@@ -56,7 +59,8 @@ export const mockListings = [
         seller: {
             name: 'Felix R.',
             memberSince: '2023',
-            moneroAddress: '48iWMy1PH6VGBJVvHDg9mY7mJ6vBDWVHpGgXEtCGp99kT4Xk5QfN3v7nqMrqGpvU'
+            moneroAddress: '48iWMy1PH6VGBJVvHDg9mY7mJ6vBDWVHpGgXEtCGp99kT4Xk5QfN3v7nqMrqGpvU',
+            publicKey: 'dGVzdC1wdWJsaWMta2V5LWZlbGl4LXItMTIzNDU2Nzg='
         }
     },
     {
@@ -71,7 +75,8 @@ export const mockListings = [
         seller: {
             name: 'Lisa S.',
             memberSince: '2025',
-            moneroAddress: '45dEQp8dFKrMXKvFWJFmZKCZhH3ARYMW4MJYM9FJcPuNT5Kek9R'
+            moneroAddress: '45dEQp8dFKrMXKvFWJFmZKCZhH3ARYMW4MJYM9FJcPuNT5Kek9R',
+            publicKey: 'dGVzdC1wdWJsaWMta2V5LWxpc2Etcy0xMjM0NTY3ODkw'
         }
     },
     {
@@ -86,7 +91,8 @@ export const mockListings = [
         seller: {
             name: 'Jan P.',
             memberSince: '2024',
-            moneroAddress: '42nTNQp8dFKrMXKvFWJFmZKCZhH3ARYMW4MJYM9FJcPuNT5Kek9R'
+            moneroAddress: '42nTNQp8dFKrMXKvFWJFmZKCZhH3ARYMW4MJYM9FJcPuNT5Kek9R',
+            publicKey: 'dGVzdC1wdWJsaWMta2V5LWphbi1wLTEyMzQ1Njc4OTA='
         }
     },
     {
@@ -101,7 +107,8 @@ export const mockListings = [
         seller: {
             name: 'Sarah M.',
             memberSince: '2021',
-            moneroAddress: '46BeWrHpwXmHDpDEUmZBWZfoQpdc6HaERCNmx1pEYL2rAcuwufPN9rXHHtyUA4QVy24G3euoGWpzR7T3'
+            moneroAddress: '46BeWrHpwXmHDpDEUmZBWZfoQpdc6HaERCNmx1pEYL2rAcuwufPN9rXHHtyUA4QVy24G3euoGWpzR7T3',
+            publicKey: 'dGVzdC1wdWJsaWMta2V5LXNhcmFoLW0tMTIzNDU2Nzg='
         }
     },
     {
@@ -116,7 +123,8 @@ export const mockListings = [
         seller: {
             name: 'Michael W.',
             memberSince: '2022',
-            moneroAddress: '43gFrHpwXmHDpDEUmZBWZfoQpdc6HaERCNmx1pEYL2rAcuwufPN9rXHHtyUA4QVy24G3euoGWpzR7T3'
+            moneroAddress: '43gFrHpwXmHDpDEUmZBWZfoQpdc6HaERCNmx1pEYL2rAcuwufPN9rXHHtyUA4QVy24G3euoGWpzR7T3',
+            publicKey: 'dGVzdC1wdWJsaWMta2V5LW1pY2hhZWwtdy0xMjM0NTY='
         }
     },
     {
@@ -131,7 +139,8 @@ export const mockListings = [
         seller: {
             name: 'Klaus H.',
             memberSince: '2023',
-            moneroAddress: '47sghzufGhJJDQEbScMCwVBimTuq6L5JiRixD8VeGbpjCTA12GwZVPWzjmpfLDJNDAWvuNDAWvuNDAWvuNDAWvuN'
+            moneroAddress: '47sghzufGhJJDQEbScMCwVBimTuq6L5JiRixD8VeGbpjCTA12GwZVPWzjmpfLDJNDAWvuNDAWvuNDAWvuNDAWvuN',
+            publicKey: 'dGVzdC1wdWJsaWMta2V5LWtsYXVzLWgtMTIzNDU2Nzg='
         }
     },
     {
@@ -146,7 +155,8 @@ export const mockListings = [
         seller: {
             name: 'Nina L.',
             memberSince: '2024',
-            moneroAddress: '44AFFq5kSiGBoZ4NMDwYtN18obc8AemS33DBLWs3H7otXft3XjrpDtQGv7SqSsaBYBb98uNbr2VBBEt7f2wfn3RVGQBEP3A'
+            moneroAddress: '44AFFq5kSiGBoZ4NMDwYtN18obc8AemS33DBLWs3H7otXft3XjrpDtQGv7SqSsaBYBb98uNbr2VBBEt7f2wfn3RVGQBEP3A',
+            publicKey: 'dGVzdC1wdWJsaWMta2V5LW5pbmEtbC0xMjM0NTY3ODkw'
         }
     }
 ];

js/services/chat.js

@@ -0,0 +1,217 @@
+/**
+ * Chat Service - Handles message storage and retrieval
+ * Uses LocalStorage as mock backend until Directus is ready
+ */
+
+import { cryptoService } from './crypto.js';
+
+const CHATS_STORAGE_KEY = 'dgray_chats';
+const MESSAGES_STORAGE_KEY = 'dgray_messages';
+
+class ChatService {
+    constructor() {
+        this.subscribers = new Set();
+    }
+
+    /**
+     * Get or create a chat between current user and another user
+     * @param {string} recipientId - The other user's ID
+     * @param {string} recipientPublicKey - The other user's public key
+     * @param {string} listingId - The listing this chat is about
+     * @returns {object} - Chat object
+     */
+    getOrCreateChat(recipientId, recipientPublicKey, listingId) {
+        const chats = this.getAllChats();
+        const myPublicKey = cryptoService.getPublicKey();
+        
+        // Find existing chat for this listing + recipient
+        let chat = chats.find(c => 
+            c.listingId === listingId && 
+            c.recipientId === recipientId
+        );
+        
+        if (!chat) {
+            chat = {
+                id: this.generateId(),
+                listingId,
+                recipientId,
+                recipientPublicKey,
+                myPublicKey,
+                createdAt: new Date().toISOString(),
+                lastMessageAt: null
+            };
+            chats.push(chat);
+            this.saveChats(chats);
+        }
+        
+        return chat;
+    }
+
+    getAllChats() {
+        try {
+            return JSON.parse(localStorage.getItem(CHATS_STORAGE_KEY) || '[]');
+        } catch {
+            return [];
+        }
+    }
+
+    saveChats(chats) {
+        localStorage.setItem(CHATS_STORAGE_KEY, JSON.stringify(chats));
+    }
+
+    /**
+     * Send an encrypted message
+     * @param {string} chatId - Chat ID
+     * @param {string} recipientPublicKey - Recipient's public key
+     * @param {string} plainText - Message content
+     * @returns {object} - The saved message
+     */
+    async sendMessage(chatId, recipientPublicKey, plainText) {
+        await cryptoService.ready;
+        
+        const { nonce, ciphertext } = cryptoService.encrypt(plainText, recipientPublicKey);
+        
+        const message = {
+            id: this.generateId(),
+            chatId,
+            senderPublicKey: cryptoService.getPublicKey(),
+            nonce,
+            ciphertext,
+            timestamp: new Date().toISOString(),
+            // Store plain text for own messages (we can't decrypt our own box messages)
+            _plainText: plainText
+        };
+        
+        const messages = this.getAllMessages();
+        messages.push(message);
+        this.saveMessages(messages);
+        
+        // Update chat's lastMessageAt
+        const chats = this.getAllChats();
+        const chat = chats.find(c => c.id === chatId);
+        if (chat) {
+            chat.lastMessageAt = message.timestamp;
+            this.saveChats(chats);
+        }
+        
+        this.notifySubscribers();
+        
+        return message;
+    }
+
+    /**
+     * Get all messages for a chat, decrypted
+     * @param {string} chatId - Chat ID
+     * @param {string} otherPublicKey - The other party's public key
+     * @returns {Array} - Decrypted messages
+     */
+    async getMessages(chatId, otherPublicKey) {
+        await cryptoService.ready;
+        
+        const messages = this.getAllMessages().filter(m => m.chatId === chatId);
+        const myPublicKey = cryptoService.getPublicKey();
+        
+        return messages.map(msg => {
+            const isOwn = msg.senderPublicKey === myPublicKey;
+            
+            let text;
+            if (isOwn) {
+                // Use stored plain text for own messages
+                text = msg._plainText || '[Encrypted]';
+            } else {
+                // Decrypt messages from others
+                text = cryptoService.decrypt(msg.ciphertext, msg.nonce, msg.senderPublicKey);
+                if (!text) text = '[Decryption failed]';
+            }
+            
+            return {
+                id: msg.id,
+                text,
+                isOwn,
+                timestamp: msg.timestamp
+            };
+        });
+    }
+
+    getAllMessages() {
+        try {
+            return JSON.parse(localStorage.getItem(MESSAGES_STORAGE_KEY) || '[]');
+        } catch {
+            return [];
+        }
+    }
+
+    saveMessages(messages) {
+        localStorage.setItem(MESSAGES_STORAGE_KEY, JSON.stringify(messages));
+    }
+
+    generateId() {
+        return 'msg_' + Date.now() + '_' + Math.random().toString(36).substr(2, 9);
+    }
+
+    subscribe(callback) {
+        this.subscribers.add(callback);
+        return () => this.subscribers.delete(callback);
+    }
+
+    notifySubscribers() {
+        this.subscribers.forEach(cb => cb());
+    }
+
+    /**
+     * Simulate receiving a message (for demo purposes)
+     * In production, this would come from Directus/WebSocket
+     */
+    async simulateIncomingMessage(chatId, senderPublicKey, plainText) {
+        await cryptoService.ready;
+        
+        const myPublicKey = cryptoService.getPublicKey();
+        const { nonce, ciphertext } = this.encryptForRecipient(plainText, myPublicKey, senderPublicKey);
+        
+        const message = {
+            id: this.generateId(),
+            chatId,
+            senderPublicKey,
+            nonce,
+            ciphertext,
+            timestamp: new Date().toISOString()
+        };
+        
+        const messages = this.getAllMessages();
+        messages.push(message);
+        this.saveMessages(messages);
+        
+        this.notifySubscribers();
+        
+        return message;
+    }
+
+    // Helper for simulation - encrypt as if from another user
+    encryptForRecipient(message, recipientPublicKey, senderSecretKey) {
+        // This is a simplified simulation - in reality the sender would have their own keypair
+        const nacl = window.nacl;
+        const naclUtil = window.nacl.util;
+        
+        const nonce = nacl.randomBytes(nacl.box.nonceLength);
+        const messageUint8 = naclUtil.decodeUTF8(message);
+        
+        // For simulation, we create a temporary keypair for the "sender"
+        const senderKeyPair = nacl.box.keyPair.fromSecretKey(
+            naclUtil.decodeBase64(senderSecretKey || naclUtil.encodeBase64(nacl.randomBytes(32)))
+        );
+        
+        const encrypted = nacl.box(
+            messageUint8,
+            nonce,
+            naclUtil.decodeBase64(recipientPublicKey),
+            senderKeyPair.secretKey
+        );
+        
+        return {
+            nonce: naclUtil.encodeBase64(nonce),
+            ciphertext: naclUtil.encodeBase64(encrypted)
+        };
+    }
+}
+
+export const chatService = new ChatService();

js/services/crypto.js

@@ -0,0 +1,127 @@
+/**
+ * E2E Encryption Service using TweetNaCl
+ * https://tweetnacl.js.org/
+ */
+
+const STORAGE_KEY = 'dgray_keypair';
+
+class CryptoService {
+    constructor() {
+        this.nacl = null;
+        this.naclUtil = null;
+        this.keyPair = null;
+        this.ready = this.init();
+    }
+
+    async init() {
+        // Dynamically import TweetNaCl from CDN
+        if (!window.nacl) {
+            await this.loadScript('https://cdn.jsdelivr.net/npm/tweetnacl@1.0.3/nacl-fast.min.js');
+            await this.loadScript('https://cdn.jsdelivr.net/npm/tweetnacl-util@0.15.1/nacl-util.min.js');
+        }
+        
+        this.nacl = window.nacl;
+        this.naclUtil = window.nacl.util;
+        
+        this.loadOrCreateKeyPair();
+    }
+
+    loadScript(src) {
+        return new Promise((resolve, reject) => {
+            if (document.querySelector(`script[src="${src}"]`)) {
+                resolve();
+                return;
+            }
+            const script = document.createElement('script');
+            script.src = src;
+            script.onload = resolve;
+            script.onerror = reject;
+            document.head.appendChild(script);
+        });
+    }
+
+    loadOrCreateKeyPair() {
+        const stored = localStorage.getItem(STORAGE_KEY);
+        
+        if (stored) {
+            try {
+                const parsed = JSON.parse(stored);
+                this.keyPair = {
+                    publicKey: this.naclUtil.decodeBase64(parsed.publicKey),
+                    secretKey: this.naclUtil.decodeBase64(parsed.secretKey)
+                };
+                return;
+            } catch (e) {
+                console.warn('Failed to load keypair, generating new one');
+            }
+        }
+        
+        this.generateKeyPair();
+    }
+
+    generateKeyPair() {
+        this.keyPair = this.nacl.box.keyPair();
+        
+        const toStore = {
+            publicKey: this.naclUtil.encodeBase64(this.keyPair.publicKey),
+            secretKey: this.naclUtil.encodeBase64(this.keyPair.secretKey)
+        };
+        
+        localStorage.setItem(STORAGE_KEY, JSON.stringify(toStore));
+    }
+
+    getPublicKey() {
+        if (!this.keyPair) return null;
+        return this.naclUtil.encodeBase64(this.keyPair.publicKey);
+    }
+
+    /**
+     * Encrypt a message for a recipient
+     * @param {string} message - Plain text message
+     * @param {string} recipientPublicKey - Base64 encoded public key
+     * @returns {object} - { nonce, ciphertext } both base64 encoded
+     */
+    encrypt(message, recipientPublicKey) {
+        const nonce = this.nacl.randomBytes(this.nacl.box.nonceLength);
+        const messageUint8 = this.naclUtil.decodeUTF8(message);
+        const recipientKey = this.naclUtil.decodeBase64(recipientPublicKey);
+        
+        const encrypted = this.nacl.box(
+            messageUint8,
+            nonce,
+            recipientKey,
+            this.keyPair.secretKey
+        );
+        
+        return {
+            nonce: this.naclUtil.encodeBase64(nonce),
+            ciphertext: this.naclUtil.encodeBase64(encrypted)
+        };
+    }
+
+    /**
+     * Decrypt a message from a sender
+     * @param {string} ciphertext - Base64 encoded ciphertext
+     * @param {string} nonce - Base64 encoded nonce
+     * @param {string} senderPublicKey - Base64 encoded public key
+     * @returns {string|null} - Decrypted message or null if failed
+     */
+    decrypt(ciphertext, nonce, senderPublicKey) {
+        try {
+            const decrypted = this.nacl.box.open(
+                this.naclUtil.decodeBase64(ciphertext),
+                this.naclUtil.decodeBase64(nonce),
+                this.naclUtil.decodeBase64(senderPublicKey),
+                this.keyPair.secretKey
+            );
+            
+            if (!decrypted) return null;
+            return this.naclUtil.encodeUTF8(decrypted);
+        } catch (e) {
+            console.error('Decryption failed:', e);
+            return null;
+        }
+    }
+}
+
+export const cryptoService = new CryptoService();

locales/de.json

@@ -105,6 +105,13 @@
     "copyAddress": "Adresse kopieren",
     "contactHint": "Kopiere die Adresse und sende den Betrag über dein Monero-Wallet."
   },
+  "chat": {
+    "title": "Nachricht senden",
+    "placeholder": "Nachricht schreiben...",
+    "encrypted": "Ende-zu-Ende verschlüsselt",
+    "startConversation": "Starte eine Unterhaltung mit dem Anbieter.",
+    "send": "Senden"
+  },
   "create": {
     "title": "Anzeige erstellen",
     "listingTitle": "Titel",

locales/en.json

@@ -105,6 +105,13 @@
     "copyAddress": "Copy address",
     "contactHint": "Copy the address and send the amount using your Monero wallet."
   },
+  "chat": {
+    "title": "Send Message",
+    "placeholder": "Write a message...",
+    "encrypted": "End-to-end encrypted",
+    "startConversation": "Start a conversation with the seller.",
+    "send": "Send"
+  },
   "create": {
     "title": "Create Listing",
     "listingTitle": "Title",

locales/fr.json

@@ -105,6 +105,13 @@
     "copyAddress": "Copier l'adresse",
     "contactHint": "Copiez l'adresse et envoyez le montant via votre portefeuille Monero."
   },
+  "chat": {
+    "title": "Envoyer un message",
+    "placeholder": "Écrire un message...",
+    "encrypted": "Chiffré de bout en bout",
+    "startConversation": "Démarrez une conversation avec le vendeur.",
+    "send": "Envoyer"
+  },
   "create": {
     "title": "Créer une annonce",
     "listingTitle": "Titre",