import {
  useEffect,
  useLayoutEffect,
  useRef,
  useState,
  type CSSProperties,
  type HTMLAttributes,
  type DragEvent as ReactDragEvent,
  type ReactNode
} from "react";
import {
  GripVertical,
  Settings2,
  Trash2
} from "lucide-react";
import {
  Card,
  DocumentationHelpLink,
  IconButton,
  type ApiSettings,
  type AuthInfo,
  type DashboardWidgetContribution,
  type EffectiveViewProjection,
  type PlatformWebModule
} from "@govoplan/core-webui";
import {
  dashboardMasonryRowSpan,
  dashboardWidgetColumnSpan,
  defaultWidgetSize,
  widgetIsConfigurable,
  type DashboardWidgetPlacement
} from "./dashboardLayout";
import {
  dashboardGridPreview,
  type DashboardDragItem,
  type DashboardDropTarget
} from "./dashboardEditorTypes";

type DashboardGridProps = {
  placements: DashboardWidgetPlacement[];
  widgetById: Map<string, DashboardWidgetContribution>;
  settings: ApiSettings;
  auth: AuthInfo;
  modules: PlatformWebModule[];
  effectiveView: EffectiveViewProjection | null;
  refreshKey: number;
  configuring: boolean;
  dragItem: DashboardDragItem | null;
  dropTarget: DashboardDropTarget | null;
  onDragStart: (event: ReactDragEvent, item: DashboardDragItem) => void;
  onDragEnd: () => void;
  onDragOver: (event: ReactDragEvent<HTMLElement>, instanceId: string) => void;
  onDragOverEnd: (event: ReactDragEvent<HTMLElement>) => void;
  onDrop: (
    event: ReactDragEvent<HTMLElement>,
    placement: DashboardWidgetPlacement
  ) => void;
  onDropPreview: (event: ReactDragEvent<HTMLElement>) => void;
  onDropAtEnd: (event: ReactDragEvent<HTMLElement>) => void;
  onRemove: (instanceId: string) => void;
  onConfigure: (instanceId: string) => void;
};

export default function DashboardGrid({
  placements,
  widgetById,
  settings,
  auth,
  modules,
  effectiveView,
  refreshKey,
  configuring,
  dragItem,
  dropTarget,
  onDragStart,
  onDragEnd,
  onDragOver,
  onDragOverEnd,
  onDrop,
  onDropPreview,
  onDropAtEnd,
  onRemove,
  onConfigure
}: DashboardGridProps) {
  const showingEmptyPreview =
    configuring
    && dragItem?.kind === "catalogue"
    && dropTarget !== null;
  if (!placements.length && !showingEmptyPreview) {
    return (
      <div
        className={`dashboard-empty-state${configuring ? " is-drop-target" : ""}`}
        onDragOver={(event) => {
          if (!configuring) return;
          onDragOverEnd(event);
        }}
        onDrop={configuring ? onDropAtEnd : undefined}
      >
        <h2>No widgets on this Dashboard</h2>
        <p className="muted">
          {configuring
            ? "Drag a widget here from the library."
            : "Open Configure to add widgets provided by active modules."}
        </p>
      </div>
    );
  }

  const catalogueWidget =
    dragItem?.kind === "catalogue"
      ? widgetById.get(dragItem.widgetId)
      : null;
  const previewItems = dashboardGridPreview(
    placements,
    configuring ? dragItem : null,
    configuring ? dropTarget : null,
    catalogueWidget ? defaultWidgetSize(catalogueWidget) : "medium"
  );

  return (
    <div
      className={`dashboard-widget-grid${configuring ? " is-configuring" : ""}`}
      data-dashboard-grid
      onDragOver={(event) => {
        if (!configuring || event.target !== event.currentTarget) return;
        onDragOverEnd(event);
      }}
      onDrop={configuring ? onDropAtEnd : undefined}
    >
      {previewItems.map((item) => {
        if (item.kind === "catalogue") {
          const widget = widgetById.get(item.widgetId);
          return (
            <DashboardDropPlaceholder
              key={`catalogue-placeholder:${item.widgetId}`}
              title={widget?.title ?? "New widget"}
              size={item.size}
              columnStart={item.columnStart}
              onDragOver={(event) => event.preventDefault()}
              onDrop={onDropPreview}
            />
          );
        }
        const placement = item.placement;
        const widget = widgetById.get(placement.widgetId);
        if (!widget) return null;
        if (item.placeholder) {
          return (
            <DashboardDropPlaceholder
              key={placement.instanceId}
              title={widget.title}
              size={placement.size}
              columnStart={placement.columnStart}
              preserveHeight
              onDragOver={(event) => event.preventDefault()}
              onDrop={onDropPreview}
            >
              <Card title={widget.title} titleHelp={widget.documentation && <DocumentationHelpLink reference={widget.documentation} />}>
                <DashboardWidgetContent
                  widget={widget}
                  placement={placement}
                  settings={settings}
                  auth={auth}
                  modules={modules}
                  effectiveView={effectiveView}
                  refreshKey={refreshKey}
                />
              </Card>
            </DashboardDropPlaceholder>
          );
        }
        return (
          <DashboardMasonryItem
            key={placement.instanceId}
            className={`dashboard-widget dashboard-widget-${placement.size}`}
            style={dashboardColumnStyle(placement.columnStart)}
            onDragOver={
              configuring
                ? (event) => onDragOver(event, placement.instanceId)
                : undefined
            }
            onDrop={
              configuring
                ? (event) => onDrop(event, placement)
                : undefined
            }
          >
            <Card
              title={widget.title}
              titleHelp={widget.documentation && <DocumentationHelpLink reference={widget.documentation} />}
              collapsible={!configuring}
              collapseKey={`dashboard-widget:${placement.instanceId}`}
              actions={
                configuring ? (
                  <div className="dashboard-widget-actions">
                    <IconButton
                      label={`Drag ${widget.title}`}
                      icon={<GripVertical size={16} />}
                      variant="ghost"
                      className="dashboard-widget-drag-handle"
                      draggable
                      onDragStart={(event) =>
                        onDragStart(event, {
                          kind: "placement",
                          instanceId: placement.instanceId
                        })
                      }
                      onDragEnd={onDragEnd}
                    />
                    {widgetIsConfigurable(widget) && (
                      <IconButton
                        label={`Configure ${widget.title}`}
                        icon={<Settings2 size={16} />}
                        variant="ghost"
                        onClick={() => onConfigure(placement.instanceId)}
                      />
                    )}
                    <IconButton
                      label={`Remove ${widget.title}`}
                      icon={<Trash2 size={16} />}
                      variant="ghost"
                      onClick={() => onRemove(placement.instanceId)}
                    />
                  </div>
                ) : undefined
              }
            >
              <DashboardWidgetContent
                widget={widget}
                placement={placement}
                settings={settings}
                auth={auth}
                modules={modules}
                effectiveView={effectiveView}
                refreshKey={refreshKey}
              />
            </Card>
          </DashboardMasonryItem>
        );
      })}
      {configuring && (
        <div
          className="dashboard-grid-end-drop-target"
          onDragOver={onDragOverEnd}
          onDrop={onDropAtEnd}
        >
          Drop here to place the widget last
        </div>
      )}
    </div>
  );
}

function DashboardDropPlaceholder({
  title,
  size,
  columnStart,
  preserveHeight = false,
  onDragOver,
  onDrop,
  children
}: {
  title: string;
  size: DashboardWidgetPlacement["size"];
  columnStart: number;
  preserveHeight?: boolean;
  onDragOver: (event: ReactDragEvent<HTMLElement>) => void;
  onDrop: (event: ReactDragEvent<HTMLElement>) => void;
  children?: ReactNode;
}) {
  return (
    <DashboardMasonryItem
      className={[
        "dashboard-widget",
        `dashboard-widget-${size}`,
        "dashboard-widget-drop-placeholder",
        preserveHeight ? "preserves-widget-height" : ""
      ]
        .filter(Boolean)
        .join(" ")}
      style={dashboardColumnStyle(columnStart)}
      onDragOver={onDragOver}
      onDrop={onDrop}
      aria-label={
        `Place ${title} in column ${columnStart}, spanning `
        + `${dashboardWidgetColumnSpan(size)} columns`
      }
    >
      {children && (
        <div className="dashboard-widget-placeholder-content">
          {children}
        </div>
      )}
      <div className="dashboard-widget-placeholder-surface">
        <GripVertical size={18} aria-hidden="true" />
        <strong>{title}</strong>
      </div>
    </DashboardMasonryItem>
  );
}

function dashboardColumnStyle(columnStart: number): CSSProperties {
  return {
    "--dashboard-column-start": columnStart
  } as CSSProperties;
}

function DashboardMasonryItem({
  children,
  ...props
}: HTMLAttributes<HTMLElement>) {
  const itemRef = useRef<HTMLElement>(null);

  useLayoutEffect(() => {
    const item = itemRef.current;
    const grid = item?.parentElement;
    if (!item || !grid) return undefined;

    const updateSpan = () => {
      const gridStyles = window.getComputedStyle(grid);
      const itemStyles = window.getComputedStyle(item);
      const rowHeight = Number.parseFloat(gridStyles.gridAutoRows);
      const bottomGap = Number.parseFloat(itemStyles.marginBottom);
      const nextSpan = dashboardMasonryRowSpan(
        item.getBoundingClientRect().height,
        rowHeight,
        bottomGap
      );
      const gridRowEnd = `span ${nextSpan}`;
      if (item.style.gridRowEnd !== gridRowEnd) {
        item.style.gridRowEnd = gridRowEnd;
      }
    };

    updateSpan();
    if (typeof ResizeObserver === "undefined") return undefined;
    const observer = new ResizeObserver(updateSpan);
    observer.observe(item);
    return () => observer.disconnect();
  }, []);

  return (
    <section ref={itemRef} {...props}>
      {children}
    </section>
  );
}

function DashboardWidgetContent({
  widget,
  placement,
  settings,
  auth,
  modules,
  effectiveView,
  refreshKey
}: {
  widget: DashboardWidgetContribution;
  placement: DashboardWidgetPlacement;
  settings: ApiSettings;
  auth: AuthInfo;
  modules: PlatformWebModule[];
  effectiveView: EffectiveViewProjection | null;
  refreshKey: number;
}) {
  const [scheduledRefreshKey, setScheduledRefreshKey] = useState(0);

  useEffect(() => {
    if (!widget.refreshIntervalMs) return undefined;
    const interval = window.setInterval(
      () => setScheduledRefreshKey((value) => value + 1),
      Math.max(widget.refreshIntervalMs, 5_000)
    );
    return () => window.clearInterval(interval);
  }, [widget.refreshIntervalMs]);

  return widget.render({
    settings,
    auth,
    modules,
    effectiveView,
    instanceId: placement.instanceId,
    widgetId: widget.id,
    refreshKey: refreshKey + scheduledRefreshKey,
    size: placement.size,
    configuration: placement.configuration
  });
}