"use client";

import { useEffect, useState, useCallback, useMemo } from "react";
import { useRouter } from "next/navigation";
import { useAuth } from "@/lib/auth";
import { getTasks, getGroups, createTask, updateTask, Task, Group } from "@/lib/api";
import { useTranslation } from "@/lib/i18n";
import TaskCard from "@/components/TaskCard";
import TaskModal from "@/components/TaskModal";
import { useSwipeable } from "react-swipeable";

const STATUS_VALUES = ["pending", "in_progress", "done", "cancelled"] as const;
type StatusValue = (typeof STATUS_VALUES)[number];

function statusColor(s: StatusValue | null): string {
  switch (s) {
    case "pending": return "#FBBF24";
    case "in_progress": return "#60A5FA";
    case "done": return "#34D399";
    case "cancelled": return "#9CA3AF";
    default: return "#7A7A9A";
  }
}

export default function TasksPage() {
  const { token, user } = useAuth();
  const { t } = useTranslation();
  const router = useRouter();
  const [tasks, setTasks] = useState<Task[]>([]);
  const [groups, setGroups] = useState<Group[]>([]);
  const [loading, setLoading] = useState(true);
  const [selectedGroup, setSelectedGroup] = useState<string | null>(null);
  const [selectedStatus, setSelectedStatus] = useState<StatusValue | null>(null);
  const [groupOpen, setGroupOpen] = useState(false);
  
  const [showForm, setShowForm] = useState(false);
  const [swipeDirection, setSwipeDirection] = useState<"left" | "right" | null>(null);
  const [swipeOverlay, setSwipeOverlay] = useState<{ name: string; icon: string | null } | null>(null);

  // Build group order: [null (all), group1.id, group2.id, ...]
  const groupOrder = useMemo(() => {
    return [null, ...groups.map((g) => g.id)];
  }, [groups]);

  const currentGroupIndex = useMemo(() => {
    return groupOrder.indexOf(selectedGroup);
  }, [groupOrder, selectedGroup]);

  const selectedGroupObj = useMemo(
    () => (selectedGroup ? groups.find((g) => g.id === selectedGroup) ?? null : null),
    [selectedGroup, groups]
  );

  const loadData = useCallback(async () => {
    if (!token) return;
    setLoading(true);
    try {
      const params: Record<string, string> = {};
      if (selectedGroup) params.group_id = selectedGroup;
      if (selectedStatus) params.status = selectedStatus;

      const [tasksRes, groupsRes] = await Promise.all([
        getTasks(token, Object.keys(params).length > 0 ? params : undefined),
        getGroups(token),
      ]);
      setTasks(tasksRes.data || []);
      setGroups(groupsRes.data || []);
    } catch (err) {
      console.error("Load error:", err);
    } finally {
      setLoading(false);
    }
  }, [token, selectedGroup, selectedStatus]);

  useEffect(() => {
    if (!token) {
      router.replace("/login");
      return;
    }
    loadData();
  }, [token, router, loadData]);

  // Navigate to next/previous group via swipe
  const navigateGroup = useCallback(
    (direction: "left" | "right") => {
      if (groupOrder.length <= 1) return;
      const newIndex =
        direction === "left"
          ? (currentGroupIndex + 1) % groupOrder.length
          : (currentGroupIndex - 1 + groupOrder.length) % groupOrder.length;
      const newGroupId = groupOrder[newIndex];

      if (newGroupId === null) {
        setSwipeOverlay({ name: t("tasks.all"), icon: null });
      } else {
        const group = groups.find((g) => g.id === newGroupId);
        setSwipeOverlay({ name: group?.name || "", icon: group?.icon || null });
      }
      setSwipeDirection(direction);
      setSelectedGroup(newGroupId);

      setTimeout(() => {
        setSwipeOverlay(null);
        setSwipeDirection(null);
      }, 600);
    },
    [groupOrder, currentGroupIndex, groups, t]
  );

  // Swipe handlers for cycling groups
  const swipeHandlers = useSwipeable({
    onSwipedLeft: () => navigateGroup("left"),
    onSwipedRight: () => navigateGroup("right"),
    trackMouse: false,
    trackTouch: true,
    preventScrollOnSwipe: false,
    delta: 50,
    swipeDuration: 500,
  });

  async function handleCreateTask(data: Partial<Task>) {
    if (!token) return;
    await createTask(token, data);
    setShowForm(false);
    loadData();
  }

  async function handleCompleteTask(taskId: string) {
    if (!token) return;
    try {
      await updateTask(token, taskId, { status: "done" });
      loadData();
    } catch (err) {
      console.error("Complete error:", err);
    }
  }

  if (!token) return null;

  const userInitial = (user?.name || user?.email || "?").charAt(0).toUpperCase();

  return (
    <div className="pb-24 sm:pb-8">
      {/* Single-row sticky filter header — group dropdown left, status pills right */}
      <div style={{
        display: "flex", alignItems: "center",
        padding: "0 8px",
        position: "sticky", top: 44, zIndex: 40,
        height: 40, maxHeight: 40,
        background: "var(--background, #fff)",
        borderBottom: "1px solid var(--border, #e5e7eb)",
        flexWrap: "nowrap", overflow: "hidden",
      }}>

        {/* Groups dropdown — compact, left side */}
        <div style={{ position: "relative", flexShrink: 0 }}>
          <button
            onClick={() => { setGroupOpen(o => !o); }}
            style={{
              display: "flex", alignItems: "center", gap: 4,
              padding: "4px 10px", borderRadius: 16, height: 32,
              border: `1.5px solid ${selectedGroupObj?.color || "var(--border, #3A3A4A)"}`,
              background: selectedGroupObj ? selectedGroupObj.color + "18" : "transparent",
              color: selectedGroupObj?.color || "var(--foreground, #374151)",
              fontSize: 12, fontWeight: 600, cursor: "pointer", whiteSpace: "nowrap",
            }}
          >
            {selectedGroupObj
              ? `${selectedGroupObj.icon ?? ""} ${(selectedGroupObj as any).name}`
              : t("tasks.all")}
            <span style={{ fontSize: 8, opacity: 0.5, marginLeft: 1 }}>{groupOpen ? "\u25b2" : "\u25bc"}</span>
          </button>
          {groupOpen && (
            <>
              <div onClick={() => setGroupOpen(false)} style={{ position: "fixed", inset: 0, zIndex: 150 }} />
              <div style={{
                position: "absolute", top: "110%", left: 0, zIndex: 200,
                background: "var(--popover, #fff)", border: "1px solid var(--border, #e5e7eb)",
                borderRadius: 12, padding: "4px 0", minWidth: 180,
                boxShadow: "0 8px 24px rgba(0,0,0,0.15)",
              }}>
                <button
                  onClick={() => { setSelectedGroup(null); setGroupOpen(false); }}
                  style={{
                    width: "100%", padding: "9px 14px",
                    background: !selectedGroup ? "rgba(29,78,216,0.08)" : "transparent",
                    border: "none", borderLeft: `3px solid ${!selectedGroup ? "#1D4ED8" : "transparent"}`,
                    color: !selectedGroup ? "#2563EB" : "var(--foreground, #374151)",
                    textAlign: "left", fontSize: 13, cursor: "pointer",
                  }}
                >
                  {t("tasks.all")}
                </button>
                {groups.map(g => (
                  <button
                    key={g.id}
                    onClick={() => { setSelectedGroup(g.id); setGroupOpen(false); }}
                    style={{
                      width: "100%", padding: "9px 14px",
                      background: selectedGroup === g.id ? g.color + "18" : "transparent",
                      border: "none", borderLeft: `3px solid ${selectedGroup === g.id ? g.color : "transparent"}`,
                      color: selectedGroup === g.id ? g.color : "var(--foreground, #374151)",
                      textAlign: "left", fontSize: 13, cursor: "pointer",
                      display: "flex", alignItems: "center", gap: 8,
                    }}
                  >
                    <span>{g.icon}</span>
                    {g.name}
                  </button>
                ))}
              </div>
            </>
          )}
        </div>

        {/* Status pills — horizontal scroll, right side */}
        <div style={{
          display: "flex", alignItems: "center", gap: 4,
          flex: 1, overflow: "hidden", marginLeft: 0,
          justifyContent: "flex-end",
        }}
          className="scrollbar-hide"
        >
          <div style={{
            display: "flex", alignItems: "center", gap: 3,
            overflowX: "auto", flexShrink: 1,
          }}
            className="scrollbar-hide"
          >
            {/* "All" pill */}
            <button
              onClick={() => setSelectedStatus(null)}
              style={{
                padding: "3px 10px", borderRadius: 14, height: 28,
                border: "none", cursor: "pointer", whiteSpace: "nowrap",
                fontSize: 11, fontWeight: selectedStatus === null ? 700 : 500,
                background: selectedStatus === null ? "rgba(29,78,216,0.12)" : "transparent",
                color: selectedStatus === null ? "#2563EB" : "var(--muted, #6B7280)",
                transition: "all 0.15s ease",
                flexShrink: 0,
              }}
            >
              {t("tasks.all")}
            </button>
            {STATUS_VALUES.map(s => (
              <button
                key={s}
                onClick={() => setSelectedStatus(selectedStatus === s ? null : s)}
                style={{
                  display: "flex", alignItems: "center", gap: 4,
                  padding: "3px 10px", borderRadius: 14, height: 28,
                  border: "none", cursor: "pointer", whiteSpace: "nowrap",
                  fontSize: 11, fontWeight: selectedStatus === s ? 700 : 500,
                  background: selectedStatus === s ? statusColor(s) + "20" : "transparent",
                  color: selectedStatus === s ? statusColor(s) : "var(--muted, #6B7280)",
                  transition: "all 0.15s ease",
                  flexShrink: 0,
                }}
              >
                <span style={{
                  width: 6, height: 6, borderRadius: "50%",
                  background: statusColor(s), flexShrink: 0,
                }} />
                {t(`tasks.status.${s}`)}
              </button>
            ))}
          </div>
        </div>
      </div>

      {/* Swipeable task list area */}
      <div {...swipeHandlers} className="relative min-h-[200px] px-4 sm:px-0 pt-2">
        {/* Swipe overlay */}
        {swipeOverlay && (
          <div className="absolute inset-0 z-30 flex items-center justify-center pointer-events-none">
            <div
              className={`bg-black/70 dark:bg-white/20 backdrop-blur-md text-white px-6 py-3 rounded-2xl flex items-center gap-3 shadow-2xl ${
                swipeDirection === "left" ? "animate-slideOverlayLeft" : "animate-slideOverlayRight"
              }`}
            >
              {swipeOverlay.icon && (
                <span className="text-2xl">{swipeOverlay.icon}</span>
              )}
              <span className="text-lg font-semibold">{swipeOverlay.name}</span>
            </div>
          </div>
        )}

        {/* Task list */}
        <div
          className={`transition-all duration-300 ease-out ${
            swipeDirection === "left"
              ? "animate-slideContentLeft"
              : swipeDirection === "right"
              ? "animate-slideContentRight"
              : ""
          }`}
        >
          {loading ? (
            <div className="flex justify-center py-8">
              <div className="animate-spin rounded-full h-7 w-7 border-b-2 border-blue-600" />
            </div>
          ) : tasks.length === 0 ? (
            <div className="text-center py-12">
              <div className="text-4xl mb-3 opacity-50">&#9744;</div>
              <p className="text-muted text-base font-medium">{t("tasks.noTasks")}</p>
              <p className="text-muted text-sm mt-1">
                {t("tasks.createFirst")}
              </p>
            </div>
          ) : (
            <div className="space-y-1">
              {tasks.map((task) => (
                <TaskCard
                  key={task.id}
                  task={task}
                  onComplete={handleCompleteTask}
                />
              ))}
            </div>
          )}
        </div>
      </div>

      {/* Floating action button */}
      <button
        onClick={() => setShowForm(true)}
        className="fixed bottom-20 sm:bottom-6 right-4 sm:right-6 w-14 h-14 bg-blue-600 hover:bg-blue-700 active:bg-blue-800 text-white rounded-full shadow-lg hover:shadow-xl active:shadow-md transition-all duration-200 flex items-center justify-center z-40 hover:scale-105 active:scale-95"
        aria-label={t("tasks.add")}
      >
        <svg
          className="w-7 h-7"
          fill="none"
          viewBox="0 0 24 24"
          stroke="currentColor"
          strokeWidth={2.5}
        >
          <path
            strokeLinecap="round"
            strokeLinejoin="round"
            d="M12 4v16m8-8H4"
          />
        </svg>
      </button>

      {/* Add task modal */}
      {showForm && (
        <TaskModal
          groups={groups}
          onSubmit={handleCreateTask}
          onClose={() => setShowForm(false)}
        />
      )}
    </div>
  );
}