let goals = [];
let tasks = [];
let finishedTasks = [];
let selectedGoalId = null;
let selectedTaskId = null;
let sortableInstance = null;

async function loadGoals() {
    try {
        goals = await get("/api/goals");
        const selector = document.getElementById("goal-selector");
        const activatedGoals = goals.filter(g => g.activated);
        
        selector.innerHTML = activatedGoals.map(goal => 
            `<option value="${goal.id}">${escapeHtml(goal.title)}</option>`
        ).join("");
        
        if (activatedGoals.length > 0) {
            selectedGoalId = activatedGoals[0].id;
            selector.value = selectedGoalId;
            await loadTasks();
        }
    } catch (error) {
        console.error("Failed to load goals:", error);
    }
}

async function loadTasks() {
    if (!selectedGoalId) return;
    
    try {
        const allTasks = await get(`/api/tasks?goal_id=${selectedGoalId}`);
        tasks = allTasks.filter(t => t.status !== "done");
        finishedTasks = allTasks.filter(t => t.status === "done");
        
        renderTasks();
        renderFinishedTasks();
        initSortable();
        initScrollFocus();
        
        const doingTask = tasks.find(t => t.status === "doing");
        if (doingTask) {
            scrollToTask(doingTask.id);
        }
    } catch (error) {
        console.error("Failed to load tasks:", error);
    }
}

function renderTasks() {
    const container = document.getElementById("tasks-list");
    
    if (tasks.length === 0) {
        container.innerHTML = `
            <div class="empty-state">
                <h3>No tasks yet</h3>
                <p>Create your first task for this goal!</p>
            </div>
        `;
        return;
    }

    container.innerHTML = tasks.map(task => `
        <div class="task-item ${task.status}" data-task-id="${task.id}" onclick="selectTask(${task.id})">
            <div class="task-title">${escapeHtml(task.title)}</div>
            <span class="task-status-badge ${task.status}">${task.status}</span>
        </div>
    `).join("");
}

function renderFinishedTasks() {
    const container = document.getElementById("finished-list");
    
    if (finishedTasks.length === 0) {
        container.innerHTML = '<p style="color: #7f8c8d;">No completed tasks yet</p>';
        return;
    }

    container.innerHTML = finishedTasks.map(task => `
        <div class="finished-item" onclick="selectTask(${task.id})">
            <div class="finished-item-title">${escapeHtml(task.title)}</div>
            <div class="finished-item-time">Completed: ${formatTime(task.finished_time)}</div>
        </div>
    `).join("");
}

function initSortable() {
    const container = document.getElementById("tasks-list");
    
    if (sortableInstance) {
        sortableInstance.destroy();
    }
    
    sortableInstance = Sortable.create(container, {
        animation: 150,
        ghostClass: "sortable-ghost",
        chosenClass: "sortable-chosen",
        filter: ".task-item.done",
        onEnd: async function(evt) {
            const taskId = evt.item.dataset.taskId;
            const newIndex = evt.newIndex;
            
            const prevTask = tasks[newIndex - 1];
            const nextTask = tasks[newIndex + 1];
            
            let prevOrder = prevTask ? prevTask.order : 0;
            let nextOrder = nextTask ? nextTask.order : prevOrder + 2;
            
            const newOrder = (prevOrder + nextOrder) / 2;
            
            try {
                await patch(`/api/tasks/${taskId}/order`, { order: newOrder });
                await loadTasks();
            } catch (error) {
                console.error("Failed to update order:", error);
                await loadTasks();
            }
        }
    });
}

function scrollToTask(taskId) {
    const taskElement = document.querySelector(`[data-task-id="${taskId}"]`);
    if (taskElement) {
        const scrollView = document.getElementById("scroll-view");
        const taskTop = taskElement.offsetTop;
        const scrollViewHeight = scrollView.clientHeight;
        const taskHeight = taskElement.offsetHeight;
        scrollView.scrollTop = taskTop - (scrollViewHeight / 2) + (taskHeight / 2);
    }
}

function initScrollFocus() {
    const scrollView = document.getElementById("scroll-view");
    
    scrollView.removeEventListener("scroll", handleScrollFocus);
    scrollView.addEventListener("scroll", handleScrollFocus);
    
    handleScrollFocus();
}

function handleScrollFocus() {
    const scrollView = document.getElementById("scroll-view");
    const taskItems = document.querySelectorAll(".task-item");
    
    const scrollViewRect = scrollView.getBoundingClientRect();
    const focusCenter = scrollViewRect.top + scrollViewRect.height / 2;
    
    let closestItem = null;
    let closestDistance = Infinity;
    
    taskItems.forEach(item => {
        const itemRect = item.getBoundingClientRect();
        const itemCenter = itemRect.top + itemRect.height / 2;
        const distance = Math.abs(itemCenter - focusCenter);
        
        item.classList.remove("in-focus");
        
        if (distance < closestDistance) {
            closestDistance = distance;
            closestItem = item;
        }
    });
    
    if (closestItem) {
        closestItem.classList.add("in-focus");
    }
}

function selectTask(taskId) {
    selectedTaskId = taskId;
    const task = [...tasks, ...finishedTasks].find(t => t.id === taskId);
    
    if (!task) return;
    
    document.getElementById("edit-task-title").value = task.title;
    document.getElementById("edit-task-desc").value = task.desc || "";
    document.getElementById("edit-task-status").value = task.status;
    document.getElementById("side-panel-error").textContent = "";
    
    document.getElementById("side-panel").classList.add("active");
}

function closeSidePanel() {
    document.getElementById("side-panel").classList.remove("active");
    selectedTaskId = null;
}

async function saveTask() {
    if (!selectedTaskId) return;
    
    const error = document.getElementById("side-panel-error");
    error.textContent = "";
    
    const title = document.getElementById("edit-task-title").value.trim();
    const desc = document.getElementById("edit-task-desc").value;
    const status = document.getElementById("edit-task-status").value;
    
    if (!title) {
        error.textContent = "Title is required";
        return;
    }
    
    try {
        await put(`/api/tasks/${selectedTaskId}`, { title, desc });
        
        const currentTask = [...tasks, ...finishedTasks].find(t => t.id === selectedTaskId);
        if (status !== currentTask?.status) {
            await patch(`/api/tasks/${selectedTaskId}/status`, { status });
        }
        
        await loadTasks();
    } catch (err) {
        error.textContent = err.message;
    }
}

async function deleteTask() {
    if (!selectedTaskId) return;
    
    if (!confirm("Are you sure you want to delete this task?")) return;
    
    try {
        await del(`/api/tasks/${selectedTaskId}`);
        closeSidePanel();
        await loadTasks();
    } catch (error) {
        console.error("Failed to delete task:", error);
    }
}

function openTaskModal() {
    document.getElementById("task-id").value = "";
    document.getElementById("task-title").value = "";
    document.getElementById("task-desc").value = "";
    document.getElementById("task-error").textContent = "";
    document.getElementById("task-modal-title").textContent = "Create Task";
    document.getElementById("task-modal").classList.add("active");
}

function closeTaskModal() {
    document.getElementById("task-modal").classList.remove("active");
}

async function handleTaskSubmit(event) {
    event.preventDefault();
    const error = document.getElementById("task-error");
    error.textContent = "";
    
    const title = document.getElementById("task-title").value.trim();
    const desc = document.getElementById("task-desc").value;
    
    if (!title) {
        error.textContent = "Title is required";
        return;
    }
    
    const goalId = parseInt(document.getElementById("goal-selector").value);
    if (!goalId) {
        error.textContent = "Please select a goal first";
        return;
    }
    
    try {
        await post("/api/tasks", { goal_id: goalId, title, desc });
        closeTaskModal();
        await loadTasks();
    } catch (err) {
        error.textContent = err.message;
    }
}

function escapeHtml(text) {
    const div = document.createElement('div');
    div.textContent = text;
    return div.innerHTML;
}

function formatTime(isoString) {
    if (!isoString) return "";
    const date = new Date(isoString);
    return date.toLocaleString();
}

document.addEventListener("DOMContentLoaded", () => {
    document.getElementById("goal-selector").addEventListener("change", (e) => {
        selectedGoalId = parseInt(e.target.value);
        loadTasks();
    });
    
    document.getElementById("create-task-btn").addEventListener("click", openTaskModal);
    document.getElementById("task-modal-close").addEventListener("click", closeTaskModal);
    document.getElementById("task-modal-cancel").addEventListener("click", closeTaskModal);
    document.getElementById("task-form").addEventListener("submit", handleTaskSubmit);
    
    document.getElementById("side-panel-close").addEventListener("click", closeSidePanel);
    document.getElementById("save-task-btn").addEventListener("click", saveTask);
    document.getElementById("delete-task-btn").addEventListener("click", deleteTask);
    
    loadGoals();
});