"use client";

import { useCallback, useEffect, useRef, useState } from "react";
import { useTheme } from "next-themes";
import {
  ReactFlow,
  ReactFlowProvider,
  Background,
  Controls,
  MiniMap,
  applyNodeChanges,
  applyEdgeChanges,
  useReactFlow,
  type Node as RFNode,
  type Edge as RFEdge,
  type NodeChange,
  type EdgeChange,
  type Connection,
  BackgroundVariant,
} from "@xyflow/react";
import "@xyflow/react/dist/style.css";

import { useConvexAuth, useMutation, useQuery } from "convex/react";
import { api } from "@/convex/_generated/api";
import type { Id } from "@/convex/_generated/dataModel";

import { nodeTypes } from "./node-types";
import { convexNodeToRF, convexEdgeToRF, NODE_DEFAULTS } from "@/lib/canvas-utils";
import CanvasToolbar from "@/components/canvas/canvas-toolbar";

interface CanvasInnerProps {
  canvasId: Id<"canvases">;
}

function CanvasInner({ canvasId }: CanvasInnerProps) {
  const { screenToFlowPosition } = useReactFlow();
  const { resolvedTheme } = useTheme();
  const { isLoading: isAuthLoading, isAuthenticated } = useConvexAuth();
  const shouldSkipCanvasQueries = isAuthLoading || !isAuthenticated;

  useEffect(() => {
    if (process.env.NODE_ENV === "production") return;
    if (!isAuthLoading && !isAuthenticated) {
      console.warn("[Canvas debug] mounted without Convex auth", { canvasId });
    }
  }, [canvasId, isAuthLoading, isAuthenticated]);

  // ─── Convex Realtime Queries ───────────────────────────────────
  const convexNodes = useQuery(
    api.nodes.list,
    shouldSkipCanvasQueries ? "skip" : { canvasId },
  );
  const convexEdges = useQuery(
    api.edges.list,
    shouldSkipCanvasQueries ? "skip" : { canvasId },
  );

  // ─── Convex Mutations (exakte Signaturen aus nodes.ts / edges.ts) ──
  const moveNode = useMutation(api.nodes.move);
  const batchMoveNodes = useMutation(api.nodes.batchMove);
  const createNode = useMutation(api.nodes.create);
  const removeNode = useMutation(api.nodes.remove);
  const createEdge = useMutation(api.edges.create);
  const removeEdge = useMutation(api.edges.remove);

  // ─── Lokaler State (für flüssiges Dragging) ───────────────────
  const [nodes, setNodes] = useState<RFNode[]>([]);
  const [edges, setEdges] = useState<RFEdge[]>([]);

  // Drag-Lock: während des Drags kein Convex-Override
  const isDragging = useRef(false);

  // ─── Convex → Lokaler State Sync ──────────────────────────────
  useEffect(() => {
    if (!convexNodes || isDragging.current) return;
    // eslint-disable-next-line react-hooks/set-state-in-effect
    setNodes(convexNodes.map(convexNodeToRF));
  }, [convexNodes]);

  useEffect(() => {
    if (!convexEdges) return;
    // eslint-disable-next-line react-hooks/set-state-in-effect
    setEdges(convexEdges.map(convexEdgeToRF));
  }, [convexEdges]);

  // ─── Node Changes (Drag, Select, Remove) ─────────────────────
  const onNodesChange = useCallback((changes: NodeChange[]) => {
    setNodes((nds) => applyNodeChanges(changes, nds));
  }, []);

  const onEdgesChange = useCallback((changes: EdgeChange[]) => {
    setEdges((eds) => applyEdgeChanges(changes, eds));
  }, []);

  // ─── Drag Start → Lock ────────────────────────────────────────
  const onNodeDragStart = useCallback(() => {
    isDragging.current = true;
  }, []);

  // ─── Drag Stop → Commit zu Convex ─────────────────────────────
  const onNodeDragStop = useCallback(
    (_: React.MouseEvent, node: RFNode, draggedNodes: RFNode[]) => {
      isDragging.current = false;

      // Wenn mehrere Nodes gleichzeitig gedraggt wurden → batchMove
      if (draggedNodes.length > 1) {
        batchMoveNodes({
          moves: draggedNodes.map((n) => ({
            nodeId: n.id as Id<"nodes">,
            positionX: n.position.x,
            positionY: n.position.y,
          })),
        });
      } else {
        moveNode({
          nodeId: node.id as Id<"nodes">,
          positionX: node.position.x,
          positionY: node.position.y,
        });
      }
    },
    [moveNode, batchMoveNodes],
  );

  // ─── Neue Verbindung → Convex Edge ────────────────────────────
  const onConnect = useCallback(
    (connection: Connection) => {
      if (connection.source && connection.target) {
        createEdge({
          canvasId,
          sourceNodeId: connection.source as Id<"nodes">,
          targetNodeId: connection.target as Id<"nodes">,
          sourceHandle: connection.sourceHandle ?? undefined,
          targetHandle: connection.targetHandle ?? undefined,
        });
      }
    },
    [createEdge, canvasId],
  );

  // ─── Node löschen → Convex ────────────────────────────────────
  const onNodesDelete = useCallback(
    (deletedNodes: RFNode[]) => {
      for (const node of deletedNodes) {
        removeNode({ nodeId: node.id as Id<"nodes"> });
      }
    },
    [removeNode],
  );

  // ─── Edge löschen → Convex ────────────────────────────────────
  const onEdgesDelete = useCallback(
    (deletedEdges: RFEdge[]) => {
      for (const edge of deletedEdges) {
        removeEdge({ edgeId: edge.id as Id<"edges"> });
      }
    },
    [removeEdge],
  );

  const onDragOver = useCallback((event: React.DragEvent) => {
    event.preventDefault();
    event.dataTransfer.dropEffect = "move";
  }, []);

  const onDrop = useCallback(
    (event: React.DragEvent) => {
      event.preventDefault();

      const nodeType = event.dataTransfer.getData(
        "application/lemonspace-node-type",
      );
      if (!nodeType) {
        return;
      }

      const position = screenToFlowPosition({
        x: event.clientX,
        y: event.clientY,
      });

      const defaults = NODE_DEFAULTS[nodeType] ?? {
        width: 200,
        height: 100,
        data: {},
      };

      createNode({
        canvasId,
        type: nodeType,
        positionX: position.x,
        positionY: position.y,
        width: defaults.width,
        height: defaults.height,
        data: defaults.data,
      });
    },
    [screenToFlowPosition, createNode, canvasId],
  );

  // ─── Loading State ────────────────────────────────────────────
  if (convexNodes === undefined || convexEdges === undefined) {
    return (
      <div className="flex h-full w-full items-center justify-center bg-background">
        <div className="flex flex-col items-center gap-3">
          <div className="h-8 w-8 animate-spin rounded-full border-2 border-primary border-t-transparent" />
          <span className="text-sm text-muted-foreground">Canvas lädt…</span>
        </div>
      </div>
    );
  }

  return (
    <div className="relative h-full w-full">
      <CanvasToolbar canvasId={canvasId} />
      <ReactFlow
        nodes={nodes}
        edges={edges}
        nodeTypes={nodeTypes}
        onNodesChange={onNodesChange}
        onEdgesChange={onEdgesChange}
        onNodeDragStart={onNodeDragStart}
        onNodeDragStop={onNodeDragStop}
        onConnect={onConnect}
        onNodesDelete={onNodesDelete}
        onEdgesDelete={onEdgesDelete}
        onDragOver={onDragOver}
        onDrop={onDrop}
        fitView
        snapToGrid
        snapGrid={[16, 16]}
        deleteKeyCode={["Backspace", "Delete"]}
        multiSelectionKeyCode="Shift"
        proOptions={{ hideAttribution: true }}
        colorMode={resolvedTheme === "dark" ? "dark" : "light"}
        className="bg-background"
      >
        <Background variant={BackgroundVariant.Dots} gap={16} size={1} />
        <Controls className="bg-card! border! shadow-sm! rounded-lg!" />
        <MiniMap
          className="bg-card! border! shadow-sm! rounded-lg!"
          nodeColor="#6366f1"
          maskColor="rgba(0, 0, 0, 0.1)"
        />
      </ReactFlow>
    </div>
  );
}

interface CanvasProps {
  canvasId: Id<"canvases">;
}

export default function Canvas({ canvasId }: CanvasProps) {
  return (
    <ReactFlowProvider>
      <CanvasInner canvasId={canvasId} />
    </ReactFlowProvider>
  );
}