"use client";

import { useDroppable, useDraggable } from "@dnd-kit/core";
import { format, parseISO, formatDistanceToNow } from "date-fns";
import { cn } from "@/lib/utils";
import {
  CalendarDays,
  Clock,
  GripVertical,
  Layers,
  ChevronDown,
} from "lucide-react";
import { Badge } from "@/components/ui/badge";
import { ScrollArea } from "@/components/ui/scroll-area";
import { TaskStatus, TaskType } from "@prisma/client";
import {
  ScheduleTask,
  ActiveDragData,
} from "@/app/(dashboard)/schedule/SchedulePageClient";
import { TASK_STATUS_CONFIG, TASK_TYPE_LABELS } from "@/components/tasks/TaskCard";

const PRIORITY_DOT: Record<string, string> = {
  LOW: "bg-zinc-500",
  NORMAL: "bg-blue-500",
  HIGH: "bg-amber-500",
  URGENT: "bg-red-500",
};

function toDate(val: string | null | undefined): Date | null {
  if (!val) return null;
  try {
    return parseISO(val);
  } catch {
    return new Date(val);
  }
}

function BacklogItem({
  task,
  canEdit,
}: {
  task: ScheduleTask;
  canEdit: boolean;
}) {
  const { attributes, listeners, setNodeRef, transform, isDragging } =
    useDraggable({
      id: task.id,
      disabled: !canEdit,
      data: {
        type: "backlog",
        taskId: task.id,
        estimatedHours: task.estimatedHours,
      } as ActiveDragData,
    });

  const cfg = TASK_STATUS_CONFIG[task.status];
  const StatusIcon = cfg.icon;
  const contextCode = task.shot?.shotCode ?? task.asset?.assetCode;
  const dueDate = toDate(task.dueDate);
  const isOverdue =
    dueDate && dueDate < new Date() && task.status !== "DONE";

  const style = transform
    ? {
        transform: `translate3d(${transform.x}px, ${transform.y}px, 0)`,
        zIndex: 50,
      }
    : undefined;

  return (
    <div
      ref={setNodeRef}
      style={style}
      className={cn(
        "group flex items-start gap-2 px-3 py-2.5 rounded-lg border transition-colors",
        "border-zinc-800 bg-zinc-900 hover:border-zinc-700 hover:bg-zinc-800/80",
        isDragging && "opacity-30 border-amber-500/40",
        canEdit && "cursor-grab active:cursor-grabbing"
      )}
      {...listeners}
      {...attributes}
    >
      {/* Grip */}
      {canEdit && (
        <GripVertical className="h-3.5 w-3.5 text-zinc-600 shrink-0 mt-0.5 group-hover:text-zinc-400" />
      )}

      {/* Priority dot */}
      <div
        className={cn(
          "w-1.5 h-1.5 rounded-full shrink-0 mt-1.5",
          PRIORITY_DOT[task.priority] ?? "bg-zinc-500"
        )}
      />

      {/* Content */}
      <div className="flex-1 min-w-0 space-y-0.5">
        <div className="flex items-center gap-1.5">
          {contextCode && (
            <span className="text-[10px] font-mono bg-zinc-800 text-zinc-400 px-1.5 py-0.5 rounded shrink-0">
              {contextCode}
            </span>
          )}
          <span className="text-xs font-medium text-zinc-200 truncate">
            {task.title}
          </span>
        </div>
        <div className="flex items-center gap-2 flex-wrap">
          <span className="text-[10px] text-zinc-500">
            {TASK_TYPE_LABELS[task.type as TaskType]} · {task.project.code}
          </span>
          {task.estimatedHours && (
            <span className="flex items-center gap-0.5 text-[10px] text-zinc-600">
              <Clock className="h-2.5 w-2.5" />
              {task.estimatedHours}h
            </span>
          )}
        </div>
        <div className="flex items-center gap-2">
          <Badge
            className={cn(
              "text-[9px] border px-1 py-0 h-3.5 gap-0.5 shrink-0",
              cfg.color
            )}
          >
            <StatusIcon className="h-2 w-2" />
            {cfg.label}
          </Badge>
          {dueDate && (
            <span
              className={cn(
                "flex items-center gap-0.5 text-[10px]",
                isOverdue ? "text-red-400" : "text-zinc-600"
              )}
            >
              <CalendarDays className="h-2.5 w-2.5" />
              {formatDistanceToNow(dueDate, { addSuffix: true })}
            </span>
          )}
        </div>
      </div>
    </div>
  );
}

interface BacklogPanelProps {
  tasks: ScheduleTask[];
  canEdit: boolean;
}

export function BacklogPanel({ tasks, canEdit }: BacklogPanelProps) {
  const { setNodeRef, isOver } = useDroppable({
    id: "backlog-drop-zone",
  });

  return (
    <div
      className={cn(
        "flex flex-col border-l border-zinc-800 bg-zinc-900 transition-colors",
        "w-72 shrink-0"
      )}
    >
      {/* Header */}
      <div className="flex items-center justify-between px-3 py-2.5 border-b border-zinc-800 shrink-0">
        <div className="flex items-center gap-2">
          <Layers className="h-4 w-4 text-zinc-400" />
          <span className="text-sm font-medium text-zinc-200">Backlog</span>
          <span className="text-xs text-zinc-500 bg-zinc-800 px-1.5 py-0.5 rounded-full">
            {tasks.length}
          </span>
        </div>
        {canEdit && (
          <span className="text-[10px] text-zinc-600">
            Drag onto timeline
          </span>
        )}
      </div>

      {/* Drop zone + list */}
      <div
        ref={setNodeRef}
        className={cn(
          "flex-1 transition-colors",
          isOver && "bg-amber-500/5 ring-1 ring-inset ring-amber-500/20"
        )}
      >
        {tasks.length === 0 ? (
          <div className="flex flex-col items-center justify-center py-12 text-zinc-600">
            <Layers className="h-8 w-8 mb-2 opacity-30" />
            <p className="text-xs">All tasks scheduled</p>
            {canEdit && (
              <p className="text-[10px] mt-1 text-zinc-700">
                Drop here to unschedule
              </p>
            )}
          </div>
        ) : (
          <ScrollArea className="h-full">
            <div className="p-2 space-y-1.5">
              {canEdit && isOver && (
                <div className="flex items-center justify-center py-3 rounded-lg border border-dashed border-amber-500/40 text-amber-400 text-xs">
                  Drop to unschedule
                </div>
              )}
              {tasks.map((task) => (
                <BacklogItem key={task.id} task={task} canEdit={canEdit} />
              ))}
            </div>
          </ScrollArea>
        )}
      </div>
    </div>
  );
}