let goals = [];
let tasks = [];
let selectedGoalId = null;
let selectedTaskId = null;
let sortableInstance = null;
let persistTimer = null;
let currentUser = null;

async function loadGoals() {
    try {
        goals = await get("/api/goals");
        currentUser = await get("/api/auth/me");
        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("");

        const savedGoalId = currentUser.selected_goal_id;
        const savedGoalExists = savedGoalId && activatedGoals.some(g => g.id === savedGoalId);

        if (savedGoalExists) {
            selectedGoalId = savedGoalId;
            selector.value = savedGoalId;
        } else 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 {
        tasks = await get(`/api/tasks?goal_id=${selectedGoalId}`);

        renderTasks();
        initSortable();

        const currentGoal = goals.find(g => g.id === selectedGoalId);
        const savedTaskId = currentGoal ? currentGoal.selected_task_id : null;
        const savedTaskExists = savedTaskId && tasks.some(t => t.id === savedTaskId);

        let focusTaskId = null;

        if (savedTaskExists) {
            focusTaskId = savedTaskId;
            scrollToTask(savedTaskId);
            selectedTaskId = savedTaskId;
            if (isLandscapeMode()) {
                selectTask(savedTaskId);
            }
        } else {
            const doingTask = tasks.find(t => t.status === "doing");
            if (doingTask) {
                focusTaskId = doingTask.id;
                scrollToTask(doingTask.id);
                if (isLandscapeMode()) {
                    selectTask(doingTask.id);
                }
            } else if (isLandscapeMode() && tasks.length > 0) {
                selectTask(tasks[0].id);
            }
        }

        // Wait one frame so the async scroll event from scrollToTask fires first,
        // then set in-focus and bind handlers after it has been consumed.
        requestAnimationFrame(() => {
            if (focusTaskId) {
                document.querySelectorAll(".task-item.in-focus").forEach(el => el.classList.remove("in-focus"));
                const focusEl = document.querySelector(`[data-task-id="${focusTaskId}"]`);
                if (focusEl) {
                    focusEl.classList.add("in-focus");
                }
            }
            initScrollFocus();
        });
    } catch (error) {
        console.error("Failed to load tasks:", error);
    }
}

async function persistSelectedTask(taskId) {
    if (!selectedGoalId) return;
    try {
        await patch(`/api/goals/${selectedGoalId}/selected-task`, { task_id: taskId });
        const goal = goals.find(g => g.id === selectedGoalId);
        if (goal) {
            goal.selected_task_id = taskId;
        }
        console.log("Saved selected task:", taskId);
    } catch (error) {
        console.error("Failed to persist selected task:", 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 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.removeEventListener("scroll", handleScrollSave);
    scrollView.addEventListener("scroll", handleScrollFocus);
    scrollView.addEventListener("scroll", handleScrollSave);
}

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");

        const taskId = parseInt(closestItem.dataset.taskId);

        if (isLandscapeMode()) {
            if (taskId !== selectedTaskId) {
                selectTask(taskId);
            }
        }
    }
}

function handleScrollSave() {
    const inFocusTask = document.querySelector(".task-item.in-focus");

    if (inFocusTask) {
        const taskId = parseInt(inFocusTask.dataset.taskId);
        clearTimeout(persistTimer);
        persistTimer = setTimeout(() => persistSelectedTask(taskId), 400);
    }
}

function isLandscapeMode() {
    return window.innerWidth > window.innerHeight && window.innerWidth >= 1024;
}

function selectTask(taskId) {
    selectedTaskId = taskId;
    const task = tasks.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("side-panel-error").textContent = "";
    updateSaveButton();

    document.querySelectorAll(".status-btn").forEach(btn => {
        btn.classList.toggle("active", btn.dataset.status === task.status);
    });

    const sidePanel = document.getElementById("side-panel");
    if (!sidePanel.classList.contains("active")) {
        sidePanel.classList.add("active");
    }
}

function updateSaveButton() {
    const task = tasks.find(t => t.id === selectedTaskId);
    if (!task) return;

    const title = document.getElementById("edit-task-title").value.trim();
    const desc = document.getElementById("edit-task-desc").value;

    const changed = title !== task.title || desc !== (task.desc || "");
    document.getElementById("save-task-btn").disabled = !changed;
}

function closeSidePanel() {
    if (isLandscapeMode()) return;
    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;

    if (!title) {
        error.textContent = "Title is required";
        return;
    }

    try {
        await put(`/api/tasks/${selectedTaskId}`, { title, desc });
        await loadTasks();
    } catch (err) {
        error.textContent = err.message;
    }
}

async function setTaskStatus(status) {
    if (!selectedTaskId) return;

    const error = document.getElementById("side-panel-error");
    error.textContent = "";

    document.querySelectorAll(".status-btn").forEach(btn => {
        btn.classList.toggle("active", btn.dataset.status === status);
    });

    try {
        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();
}

function initWheelScroll() {
    const scrollView = document.getElementById("scroll-view");

    scrollView.addEventListener("wheel", (e) => {
        e.preventDefault();

        const taskItem = scrollView.querySelector(".task-item");
        if (!taskItem) return;

        const taskHeight = taskItem.offsetHeight + 8;
        const direction = e.deltaY > 0 ? 1 : -1;

        scrollView.scrollBy({
            top: taskHeight * direction,
            behavior: "smooth"
        });
    }, { passive: false });
}

document.addEventListener("DOMContentLoaded", () => {
    document.getElementById("goal-selector").addEventListener("change", async (e) => {
        selectedGoalId = parseInt(e.target.value);
        await patch("/api/user/selected-goal", { goal_id: selectedGoalId });
        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("save-task-btn").disabled = true;
    document.getElementById("delete-task-btn").addEventListener("click", deleteTask);

    document.getElementById("edit-task-title").addEventListener("input", updateSaveButton);
    document.getElementById("edit-task-desc").addEventListener("input", updateSaveButton);

    initWheelScroll();
    loadGoals();
});