"use client";

import { useMemo, useState } from "react";
import {
  DndContext,
  DragOverlay,
  KeyboardSensor,
  PointerSensor,
  useSensor,
  useSensors,
} from "@dnd-kit/core";
import type { DragEndEvent, DragStartEvent, UniqueIdentifier } from "@dnd-kit/core";
import { useRouter } from "next/navigation";
import { toast } from "sonner";
import { FilterIcon } from "lucide-react";
import { updateTicketStatus } from "@/app/(frontend)/helpdesk/actions";
import { TICKET_STATUSES, type TicketStatus } from "@/lib/tickets/ticketMeta";
import { KanbanColumn } from "./KanbanColumn";
import { KanbanFilters } from "./KanbanFilters";
import { KanbanTicketOverlay } from "./KanbanTicketCard";

export interface KanbanTicket {
  readonly id: number;
  readonly title: string;
  readonly status: string;
  readonly priority: string;
  readonly type: string;
  readonly storyPoints?: number | null;
  readonly sprintId?: number | null;
  readonly sprint?: { readonly id: number } | number | null;
  readonly labels: readonly { id: number; name: string; color: string }[];
  readonly assignee: { id: number; displayName: string } | null;
  readonly reporter: { id: number; displayName: string } | null;
}

export interface KanbanColumn {
  readonly status: string;
  readonly label: string;
  readonly tickets: readonly KanbanTicket[];
}

export type SprintFilter = "all" | number;

export interface KanbanFiltersProps {
  readonly sprints: readonly { id: number; name: string; status: string; startDate?: string; endDate?: string }[];
  readonly labels: readonly { id: number; name: string; color: string; project?: number | null }[];
  readonly sprintFilter: SprintFilter;
  readonly selectedLabelIds: readonly number[];
  readonly onSprintFilterChange: (value: SprintFilter) => void;
  readonly onLabelToggle: (labelId: number) => void;
}

export interface KanbanBoardProps {
  readonly project: { id: number; name: string; key: string };
  readonly columns: readonly KanbanColumn[];
  readonly sprints: readonly { id: number; name: string; status: string; startDate?: string; endDate?: string }[];
  readonly labels: readonly { id: number; name: string; color: string; project?: number | null }[];
  readonly currentUserId: number;
  readonly isAdmin: boolean;
  readonly showFilters?: boolean;
  readonly sprintFilter?: SprintFilter;
  readonly selectedLabelIds?: readonly number[];
  readonly onSprintFilterChange?: (value: SprintFilter) => void;
  readonly onLabelToggle?: (labelId: number) => void;
}

function toNumber(value: UniqueIdentifier): number | null {
  if (typeof value === "number") return Number.isInteger(value) ? value : null;
  const parsed = Number(value);
  return Number.isInteger(parsed) ? parsed : null;
}

function toTicketStatus(value: UniqueIdentifier): TicketStatus | null {
  const status = String(value);
  return TICKET_STATUSES.some((option) => option.value === status)
    ? TICKET_STATUSES.find((option) => option.value === status)?.value ?? null
    : null;
}

function ticketSprintId(ticket: KanbanTicket): number | null {
  if (ticket.sprintId != null) return ticket.sprintId;
  if (typeof ticket.sprint === "number") return ticket.sprint;
  return ticket.sprint?.id ?? null;
}

export function KanbanBoard({
  project,
  columns,
  sprints,
  labels,
  currentUserId: _currentUserId,
  isAdmin: _isAdmin,
  showFilters = true,
  sprintFilter: controlledSprintFilter,
  selectedLabelIds: controlledLabelIds,
  onSprintFilterChange,
  onLabelToggle,
}: KanbanBoardProps) {
  const router = useRouter();
  const [internalSprintFilter, setInternalSprintFilter] = useState<SprintFilter>("all");
  const [internalLabelIds, setInternalLabelIds] = useState<readonly number[]>([]);
  const [activeTicket, setActiveTicket] = useState<KanbanTicket | null>(null);
  const sprintFilter = controlledSprintFilter ?? internalSprintFilter;
  const selectedLabelIds = controlledLabelIds ?? internalLabelIds;
  const sensors = useSensors(
    useSensor(PointerSensor, { activationConstraint: { distance: 6 } }),
    useSensor(KeyboardSensor),
  );

  const allTickets = useMemo(() => columns.flatMap((column) => column.tickets), [columns]);
  const ticketsById = useMemo(() => new Map(allTickets.map((ticket) => [ticket.id, ticket])), [allTickets]);
  const filteredTicketsByColumn = useMemo(
    () =>
      new Map(
        columns.map((column) => [
          column.status,
          column.tickets.filter((ticket) => {
            const matchesSprint = sprintFilter === "all" || ticketSprintId(ticket) === sprintFilter;
            const matchesLabels =
              selectedLabelIds.length === 0 || ticket.labels.some((label) => selectedLabelIds.includes(label.id));
            return matchesSprint && matchesLabels;
          }),
        ]),
      ),
    [columns, selectedLabelIds, sprintFilter],
  );

  function setSprintFilter(value: SprintFilter) {
    onSprintFilterChange?.(value);
    if (!onSprintFilterChange) setInternalSprintFilter(value);
  }

  function toggleLabel(labelId: number) {
    onLabelToggle?.(labelId);
    if (!onLabelToggle) {
      setInternalLabelIds((current) =>
        current.includes(labelId) ? current.filter((id) => id !== labelId) : [...current, labelId],
      );
    }
  }

  function handleDragStart(event: DragStartEvent) {
    const ticketId = toNumber(event.active.id);
    setActiveTicket(ticketId === null ? null : (ticketsById.get(ticketId) ?? null));
  }

  async function handleDragEnd(event: DragEndEvent) {
    const ticketId = toNumber(event.active.id);
    const nextStatus = event.over ? toTicketStatus(event.over.id) : null;
    setActiveTicket(null);
    if (ticketId === null || nextStatus === null) return;

    const ticket = ticketsById.get(ticketId);
    if (!ticket || ticket.status === nextStatus) return;

    try {
      const result = await updateTicketStatus(ticketId, nextStatus);
      if (!result.success) {
        toast.error(result.error ?? "Could not update the ticket status.");
        return;
      }
      toast.success(`Ticket moved to ${nextStatus.replaceAll("_", " ")}`);
      router.refresh();
    } catch (error) {
      toast.error(error instanceof Error ? error.message : "Could not update the ticket status.");
    }
  }

  return (
    <div className="flex min-w-0 flex-col gap-4" aria-label={`${project.name} Kanban board`}>
      {showFilters && (
        <div className="flex flex-wrap items-center justify-between gap-3">
          <div className="flex items-center gap-2 text-sm text-muted-foreground">
            <FilterIcon className="size-4" data-icon="inline-start" />
            <span>Board filters</span>
          </div>
          <KanbanFilters
            sprints={sprints}
            labels={labels}
            sprintFilter={sprintFilter}
            selectedLabelIds={selectedLabelIds}
            onSprintFilterChange={setSprintFilter}
            onLabelToggle={toggleLabel}
          />
        </div>
      )}

      <DndContext sensors={sensors} onDragStart={handleDragStart} onDragEnd={(event) => void handleDragEnd(event)} onDragCancel={() => setActiveTicket(null)}>
        <div className="flex min-w-0 gap-4 overflow-x-auto pb-2" role="region" aria-label="Kanban columns" tabIndex={0}>
          {columns.map((column) => (
            <KanbanColumn key={column.status} column={column} tickets={filteredTicketsByColumn.get(column.status) ?? []} />
          ))}
        </div>
        <DragOverlay>{activeTicket ? <KanbanTicketOverlay ticket={activeTicket} /> : null}</DragOverlay>
      </DndContext>
    </div>
  );
}