let conversations = [];
let currentConv = null;
let currentMessages = [];
let selfName = "";
let searchTerm = "";
let searchTimer = null;
let matchIndices = [];
let currentMatchPos = -1;

// Color palette for group chat senders
const senderColors = [
    "#075e54", "#25d366", "#128c7e", "#00a884",
    "#6b3fa0", "#d4653f", "#1f97c7", "#c74375",
    "#e68a2e", "#7b5ea7", "#3d8c5c", "#c44d58"
];
const senderColorMap = {};
let colorIdx = 0;

function getSenderColor(name) {
    if (!senderColorMap[name]) {
        senderColorMap[name] = senderColors[colorIdx % senderColors.length];
        colorIdx++;
    }
    return senderColorMap[name];
}

async function init() {
    await fetchConversations();
    renderConversationList();

    document.getElementById("search-input").addEventListener("input", onSearch);
    document.getElementById("self-name").addEventListener("change", onSelfChange);
}

async function fetchConversations(query) {
    const url = query ? `/api/conversations?q=${encodeURIComponent(query)}` : "/api/conversations";
    const resp = await fetch(url);
    conversations = await resp.json() || [];
}

function renderConversationList() {
    const list = document.getElementById("conversation-list");
    list.innerHTML = "";
    for (const c of conversations) {
        const div = document.createElement("div");
        div.className = "conv-item";
        if (currentConv && c.id === currentConv.id) div.className += " active";
        div.dataset.id = c.id;
        const date = c.lastMessageDate ? formatDate(new Date(c.lastMessageDate)) : "";
        div.innerHTML = `
            <div class="conv-name">${esc(c.name)}</div>
            <div class="conv-meta">${c.messageCount} messages &middot; ${date}</div>
        `;
        div.onclick = () => loadConversation(c.id);
        list.appendChild(div);
    }
}

async function loadConversation(id) {
    // Update active state
    document.querySelectorAll(".conv-item").forEach(el => {
        el.classList.toggle("active", el.dataset.id === id);
    });

    const resp = await fetch(`/api/conversation/${id}`);
    currentConv = await resp.json();
    currentMessages = currentConv.messages || [];

    document.getElementById("chat-name").textContent = currentConv.name;

    // Detect participants and set up self selector
    const participants = new Set();
    for (const m of currentMessages) {
        if (m.sender) participants.add(m.sender);
    }

    const sel = document.getElementById("self-name");
    sel.innerHTML = "";
    for (const p of participants) {
        const opt = document.createElement("option");
        opt.value = p;
        opt.textContent = p;
        sel.appendChild(opt);
    }

    // Auto-detect: first sender is likely "self"
    if (participants.size > 0) {
        const firstSender = currentMessages.find(m => m.sender)?.sender || "";
        selfName = firstSender;
        sel.value = selfName;
    }

    document.getElementById("self-selector").style.display = participants.size > 1 ? "" : "none";

    renderMessages();
}

function onSelfChange() {
    selfName = document.getElementById("self-name").value;
    renderMessages();
}

function onSearch() {
    clearTimeout(searchTimer);
    searchTimer = setTimeout(async () => {
        searchTerm = document.getElementById("search-input").value.toLowerCase().trim();
        await fetchConversations(searchTerm);
        renderConversationList();
        if (currentConv) {
            renderMessages();
        }
    }, 200);
}

function renderMessages() {
    const container = document.getElementById("chat-messages");

    let msgs = currentMessages;
    let firstMatchIdx = -1;

    // Detect if group chat (>2 participants)
    const participants = new Set();
    for (const m of currentMessages) {
        if (m.sender) participants.add(m.sender);
    }
    const isGroup = participants.size > 2;

    let html = "";
    let lastDate = "";
    let msgIdx = 0;

    for (const m of msgs) {
        const d = new Date(m.timestamp);
        const dateStr = d.toLocaleDateString("en-US", { weekday: "long", year: "numeric", month: "long", day: "numeric" });

        if (dateStr !== lastDate) {
            html += `<div class="date-header"><span>${dateStr}</span></div>`;
            lastDate = dateStr;
        }

        const isMatch = searchTerm && (m.text || "").toLowerCase().includes(searchTerm);
        if (isMatch && firstMatchIdx === -1) firstMatchIdx = msgIdx;

        if (m.isSystem) {
            html += `<div class="message system" data-idx="${msgIdx}"><div class="msg-text">${highlight(esc(m.text), searchTerm)}</div></div>`;
            msgIdx++;
            continue;
        }

        const isSelf = m.sender === selfName;
        const cls = isSelf ? "self" : "other";
        const timeStr = d.toLocaleTimeString("en-US", { hour: "numeric", minute: "2-digit" });

        let senderHtml = "";
        if (!isSelf && isGroup) {
            const color = getSenderColor(m.sender);
            senderHtml = `<div class="sender-name" style="color:${color}">${esc(m.sender)}</div>`;
        }

        let attachHtml = "";
        if (m.attachments) {
            for (const a of m.attachments) {
                const url = `/api/media/${currentConv.id}/${encodeURIComponent(a.filename)}`;
                switch (a.type) {
                    case "image":
                        attachHtml += `<img class="msg-image" src="${url}" alt="${esc(a.filename)}" loading="lazy" onclick="openLightbox(event, '${url}')">`;
                        break;
                    case "sticker":
                        attachHtml += `<img class="msg-sticker" src="${url}" alt="sticker" loading="lazy">`;
                        break;
                    case "video":
                        attachHtml += `<video class="msg-video" controls preload="none"><source src="${url}"></video>`;
                        break;
                    case "audio":
                        attachHtml += `<audio class="msg-audio" controls preload="none"><source src="${url}"></audio>`;
                        break;
                    default:
                        attachHtml += `<a class="msg-document" href="${url}" download="${esc(a.filename)}">${esc(a.filename)}</a>`;
                }
            }
        }

        // Remove attachment filenames from displayed text
        let displayText = m.text || "";
        if (m.attachments) {
            for (const a of m.attachments) {
                displayText = displayText.replace(a.filename, "").trim();
            }
        }

        let textHtml = "";
        if (displayText) {
            textHtml = `<div class="msg-text">${highlight(esc(displayText), searchTerm)}</div>`;
        }

        html += `<div class="message ${cls}${isMatch ? " search-match" : ""}" data-idx="${msgIdx}">
            ${senderHtml}${attachHtml}${textHtml}
            <div class="msg-time">${timeStr}</div>
        </div>`;
        msgIdx++;
    }

    container.innerHTML = html;

    // Build match index list
    matchIndices = [];
    container.querySelectorAll(".search-match").forEach(el => {
        matchIndices.push(parseInt(el.dataset.idx));
    });

    const nav = document.getElementById("search-nav");
    if (searchTerm && matchIndices.length > 0) {
        nav.classList.remove("hidden");
        currentMatchPos = 0;
        updateSearchNav();
        scrollToMatch(currentMatchPos);
    } else if (searchTerm) {
        nav.classList.remove("hidden");
        currentMatchPos = -1;
        document.getElementById("search-pos").textContent = "0/0";
    } else {
        nav.classList.add("hidden");
        currentMatchPos = -1;
        container.scrollTop = container.scrollHeight;
    }
}

function updateSearchNav() {
    document.getElementById("search-pos").textContent =
        `${currentMatchPos + 1}/${matchIndices.length}`;
    // Remove highlight from all, add to current
    document.querySelectorAll(".search-current").forEach(el => el.classList.remove("search-current"));
    if (currentMatchPos >= 0) {
        const el = document.querySelector(`[data-idx="${matchIndices[currentMatchPos]}"]`);
        if (el) el.classList.add("search-current");
    }
}

function scrollToMatch(pos) {
    if (pos < 0 || pos >= matchIndices.length) return;
    const el = document.querySelector(`[data-idx="${matchIndices[pos]}"]`);
    if (el) el.scrollIntoView({ block: "center", behavior: "smooth" });
}

function searchNext() {
    if (matchIndices.length === 0) return;
    currentMatchPos = (currentMatchPos + 1) % matchIndices.length;
    updateSearchNav();
    scrollToMatch(currentMatchPos);
}

function searchPrev() {
    if (matchIndices.length === 0) return;
    currentMatchPos = (currentMatchPos - 1 + matchIndices.length) % matchIndices.length;
    updateSearchNav();
    scrollToMatch(currentMatchPos);
}

function esc(s) {
    if (!s) return "";
    const div = document.createElement("div");
    div.textContent = s;
    return div.innerHTML;
}

function highlight(html, term) {
    if (!term) return html;
    const re = new RegExp(`(${term.replace(/[.*+?^${}()|[\]\\]/g, "\\$&")})`, "gi");
    return html.replace(re, "<mark>$1</mark>");
}

function formatDate(d) {
    return d.toLocaleDateString("en-US", { month: "short", day: "numeric", year: "numeric" });
}

function openLightbox(e, url) {
    e.stopPropagation();
    const lb = document.getElementById("lightbox");
    document.getElementById("lightbox-img").src = url;
    lb.classList.remove("hidden");
}

function closeLightbox() {
    document.getElementById("lightbox").classList.add("hidden");
    document.getElementById("lightbox-img").src = "";
}

document.addEventListener("keydown", e => {
    if (e.key === "Escape") closeLightbox();
});

init();