import { createContext, useContext } from "react";
import {
  Handle,
  NodeResizer,
  Position,
  type Node,
  type NodeProps,
} from "@xyflow/react";
import { IconUser } from "@consta/icons/IconUser";
import { IconSettings } from "@consta/icons/IconSettings";
import { IconCode } from "@consta/icons/IconCode";
import { IconHand } from "@consta/icons/IconHand";
import { IconTable } from "@consta/icons/IconTable";
import { IconSendMessage } from "@consta/icons/IconSendMessage";
import { IconMail } from "@consta/icons/IconMail";
import { IconWatchStroked } from "@consta/icons/IconWatchStroked";
import { IconTable2 } from "@consta/icons/IconTable2";
import { IconAlert } from "@consta/icons/IconAlert";
import { IconLightningBolt } from "@consta/icons/IconLightningBolt";
import { IconArrowUp } from "@consta/icons/IconArrowUp";
import { IconArrowPrevious } from "@consta/icons/IconArrowPrevious";
import { IconRecord } from "@consta/icons/IconRecord";
import { IconPolygonMultiple } from "@consta/icons/IconPolygonMultiple";
import { IconGisMultiple } from "@consta/icons/IconGisMultiple";
import type { IconComponent } from "@consta/icons/Icon";
import type { DiagramNodeData, EventSubtype, NodeKind, TaskSubtype } from "./types";

type ShapeNode = Node<DiagramNodeData, NodeKind>;

/** Ids of nodes that currently have children (i.e. render as a drill-into-able sub-process). */
export const NodesWithChildrenContext = createContext<Set<string>>(new Set());

/** Current editor mode — resize handles and connection points only show in 'edit'. */
export const ModeContext = createContext<"edit" | "view">("edit");

// Gradients from palette.css's "ОСНОВНАЯ ПАЛИТРА" section — the one the
// palette itself labels as meant for diagrams/flowcharts/semantic highlights.
// This is what nodes actually render with until a user picks a custom color.
export const DEFAULT_NODE_BACKGROUND: Record<NodeKind, string> = {
  task: "var(--gradient-blue)",
  startEvent: "var(--gradient-green)",
  intermediateEvent: "var(--gradient-orange)",
  endEvent: "var(--gradient-red)",
  exclusiveGateway: "var(--gradient-purple)",
  parallelGateway: "var(--gradient-cyan)",
  inclusiveGateway: "var(--gradient-olive)",
  complexGateway: "var(--gradient-violet)",
  eventBasedGateway: "var(--gradient-teal-dark)",
  hint: "var(--gradient-frost)",
  dataObject: "var(--gradient-ice)",
};

// The color picker only understands flat hex, so it needs a solid fallback
// distinct from the gradient rendered on canvas — the gradient's start color.
export const DEFAULT_NODE_COLOR: Record<NodeKind, string> = {
  task: "#0790CB",
  startEvent: "#2CB587",
  intermediateEvent: "#FF8E58",
  endEvent: "#E13042",
  exclusiveGateway: "#A12C7E",
  parallelGateway: "#1BD3F7",
  inclusiveGateway: "#BBBD39",
  complexGateway: "#8A5CE7",
  eventBasedGateway: "#3C81A0",
  hint: "#D7E5ED",
  dataObject: "#CEEAFF",
};

// BPMN task-type icon shown as a small badge in the shape's top-left corner —
// 'none' (the plain abstract Task) intentionally has no entry, so it renders bare.
export const TASK_SUBTYPE_ICON: Partial<Record<TaskSubtype, IconComponent>> = {
  user: IconUser,
  service: IconSettings,
  script: IconCode,
  manual: IconHand,
  businessRule: IconTable,
  send: IconSendMessage,
  receive: IconMail,
};

export const TASK_SUBTYPE_LABEL: Record<TaskSubtype, string> = {
  none: "Действие",
  user: "Действие пользователя",
  service: "Сервисное действие",
  script: "Действие-скрипт",
  manual: "Ручное действие",
  businessRule: "Действие по бизнес-правилам",
  send: "Действие отправки",
  receive: "Действие получения",
};

// BPMN event-trigger icon shown centered inside the event circle — 'none'
// (the plain, untyped event) intentionally has no entry.
export const EVENT_SUBTYPE_ICON: Partial<Record<EventSubtype, IconComponent>> = {
  message: IconMail,
  timer: IconWatchStroked,
  conditional: IconTable2,
  signal: IconAlert,
  error: IconLightningBolt,
  escalation: IconArrowUp,
  compensation: IconArrowPrevious,
  terminate: IconRecord,
  multiple: IconPolygonMultiple,
  parallelMultiple: IconGisMultiple,
};

export const EVENT_SUBTYPE_LABEL: Record<EventSubtype, string> = {
  none: "Без триггера",
  message: "Сообщение",
  timer: "Таймер",
  conditional: "Условие",
  signal: "Сигнал",
  error: "Ошибка",
  escalation: "Эскалация",
  compensation: "Компенсация",
  terminate: "Завершение процесса",
  multiple: "Множественное",
  parallelMultiple: "Параллельное множественное",
};

// Which trigger subtypes are valid on each event kind, per BPMN 2.0 — used to
// filter the subtype picker in NodeInspector so it never offers an invalid combination.
export const EVENT_SUBTYPES_BY_KIND: Record<
  "startEvent" | "intermediateEvent" | "endEvent",
  EventSubtype[]
> = {
  startEvent: ["none", "message", "timer", "conditional", "signal", "multiple", "parallelMultiple"],
  intermediateEvent: [
    "none",
    "message",
    "timer",
    "conditional",
    "signal",
    "escalation",
    "compensation",
    "multiple",
    "parallelMultiple",
  ],
  endEvent: [
    "none",
    "message",
    "error",
    "escalation",
    "compensation",
    "signal",
    "terminate",
    "multiple",
  ],
};

export const DEFAULT_TASK_BORDER_RADIUS = 6;

// Text on the colored shape body (task label, gateway icon) needs a light
// default; the caption below events/gateways sits on the plain canvas
// background instead and needs a dark one. Both are overridable via the
// same `data.textColor`/`data.fontSize`.
export const DEFAULT_NODE_TEXT_COLOR = "#FFFFFF";
export const DEFAULT_CAPTION_TEXT_COLOR = "#525A64";
export const DEFAULT_NODE_FONT_SIZE = 12;

const HANDLE_POSITIONS: { id: string; position: Position }[] = [
  { id: "top", position: Position.Top },
  { id: "right", position: Position.Right },
  { id: "bottom", position: Position.Bottom },
  { id: "left", position: Position.Left },
];

/**
 * A single handle per side acts as both connection start and end
 * (React Flow handles are connectable both ways by default) — paired with
 * connectionMode="loose" on <ReactFlow> so any point can link to any point.
 */
function ShapeHandles() {
  return (
    <>
      {HANDLE_POSITIONS.map(({ id, position }) => (
        <Handle key={id} id={id} type="source" position={position} />
      ))}
    </>
  );
}

function SubProcessBadge({ id }: { id: string }) {
  const withChildren = useContext(NodesWithChildrenContext);
  if (!withChildren.has(id)) return null;
  return (
    <span
      className="diagram-node__badge"
      title="Есть вложенные узлы — выберите фигуру, чтобы открыть их из боковой панели"
    >
      ⇒
    </span>
  );
}

function ShapeResizer({
  selected,
  minWidth,
  minHeight,
  keepAspectRatio = true,
}: {
  selected: boolean;
  minWidth: number;
  minHeight: number;
  keepAspectRatio?: boolean;
}) {
  const mode = useContext(ModeContext);
  return (
    <NodeResizer
      isVisible={selected && mode === "edit"}
      minWidth={minWidth}
      minHeight={minHeight}
      keepAspectRatio={keepAspectRatio}
    />
  );
}

function TaskNode({ id, data, selected }: NodeProps<ShapeNode>) {
  const subtype = (data.subtype as TaskSubtype | undefined) ?? "none";
  const SubtypeIcon = TASK_SUBTYPE_ICON[subtype];
  const textColor = data.textColor ?? DEFAULT_NODE_TEXT_COLOR;
  return (
    <div
      className="diagram-node diagram-node--task"
      style={{
        background: data.color ?? DEFAULT_NODE_BACKGROUND.task,
        borderRadius: data.borderRadius ?? DEFAULT_TASK_BORDER_RADIUS,
      }}
    >
      <ShapeResizer
        selected={selected}
        minWidth={70}
        minHeight={32}
        keepAspectRatio={false}
      />
      <ShapeHandles />
      <SubProcessBadge id={id} />
      {SubtypeIcon && (
        <span
          className="diagram-node__subtype-badge"
          style={{ color: textColor }}
          title={TASK_SUBTYPE_LABEL[subtype]}
        >
          <SubtypeIcon size="xs" />
        </span>
      )}
      <span
        className="diagram-node__label"
        style={{
          color: textColor,
          fontSize: data.fontSize ?? DEFAULT_NODE_FONT_SIZE,
        }}
      >
        {data.label}
      </span>
    </div>
  );
}

function EventNode({ id, data, type, selected }: NodeProps<ShapeNode>) {
  const kind =
    (type as "startEvent" | "intermediateEvent" | "endEvent") ?? "startEvent";
  const subtype = (data.subtype as EventSubtype | undefined) ?? "none";
  const SubtypeIcon = EVENT_SUBTYPE_ICON[subtype];
  return (
    <div
      className="diagram-node diagram-node--circle"
      style={{ background: data.color ?? DEFAULT_NODE_BACKGROUND[kind] }}
    >
      <ShapeResizer selected={selected} minWidth={24} minHeight={24} />
      <ShapeHandles />
      <SubProcessBadge id={id} />
      {SubtypeIcon && (
        <span
          className="diagram-node__event-icon"
          style={{ color: data.textColor ?? DEFAULT_NODE_TEXT_COLOR }}
          title={EVENT_SUBTYPE_LABEL[subtype]}
        >
          <SubtypeIcon size="s" />
        </span>
      )}
      <span
        className="diagram-node__caption"
        style={{
          color: data.textColor ?? DEFAULT_CAPTION_TEXT_COLOR,
          fontSize: data.fontSize ?? DEFAULT_NODE_FONT_SIZE,
        }}
      >
        {data.label}
      </span>
    </div>
  );
}

const GATEWAY_ICON: Record<
  "exclusiveGateway" | "parallelGateway" | "inclusiveGateway" | "complexGateway" | "eventBasedGateway",
  string
> = {
  exclusiveGateway: "✕",
  parallelGateway: "+",
  inclusiveGateway: "○",
  complexGateway: "✳",
  eventBasedGateway: "⬠",
};

function GatewayNode({ id, data, type, selected }: NodeProps<ShapeNode>) {
  const kind =
    (type as
      | "exclusiveGateway"
      | "parallelGateway"
      | "inclusiveGateway"
      | "complexGateway"
      | "eventBasedGateway") ?? "exclusiveGateway";
  return (
    <div className="diagram-node--gateway-outer">
      <ShapeResizer selected={selected} minWidth={32} minHeight={32} />
      {/*
        The diamond is drawn with clip-path on a plain (unrotated) box, not
        `transform: rotate(45deg)` — a rotated element makes React Flow's
        getBoundingClientRect-based handle measurement pick up sub-pixel
        rounding from the rotation, which showed up as a visible kink in
        otherwise-straight horizontal/vertical edges. With clip-path, the
        standard Position.Top/Right/Bottom/Left handles already land exactly
        on the diamond's tips (they're at the box's edge midpoints either
        way), so this reuses the same ShapeHandles as every other shape.
        Handles/badge/caption are siblings of the clipped div, not children
        of it, since clip-path would otherwise cut off anything of theirs
        that renders outside the diamond outline.
      */}
      <div
        className="diagram-node--diamond-bg"
        style={{ background: data.color ?? DEFAULT_NODE_BACKGROUND[kind] }}
      />
      <ShapeHandles />
      <SubProcessBadge id={id} />
      <span className="diagram-node__icon">{GATEWAY_ICON[kind]}</span>
      <span
        className="diagram-node__caption"
        style={{
          color: data.textColor ?? DEFAULT_CAPTION_TEXT_COLOR,
          fontSize: data.fontSize ?? DEFAULT_NODE_FONT_SIZE,
        }}
      >
        {data.label}
      </span>
    </div>
  );
}

// Not a BPMN element — a free-floating annotation the user places next to
// other shapes. No handles: it's never meant to be wired into the flow.
function HintNode({ data, selected }: NodeProps<ShapeNode>) {
  return (
    <div
      className="diagram-node diagram-node--hint"
      style={{
        background: data.color ?? DEFAULT_NODE_BACKGROUND.hint,
        borderRadius: data.borderRadius ?? DEFAULT_TASK_BORDER_RADIUS,
      }}
    >
      <ShapeResizer
        selected={selected}
        minWidth={60}
        minHeight={32}
        keepAspectRatio={false}
      />
      <span
        className="diagram-node__label"
        style={{
          // The default hint fill (--gradient-frost) is pale, unlike the
          // vivid task backgrounds, so it needs the dark caption color, not
          // the light one — same reasoning as DataObjectNode below.
          color: data.textColor ?? DEFAULT_CAPTION_TEXT_COLOR,
          fontSize: data.fontSize ?? DEFAULT_NODE_FONT_SIZE,
        }}
      >
        {data.label}
      </span>
    </div>
  );
}

// BPMN Data Object — represents a document/input/output attached to a task
// via a (typically dashed) Data Association edge. The folded top-right corner
// is clipped on an inner div, not the outer one, so ShapeHandles — siblings of
// it — still land at the plain bounding-box edges instead of being cut off
// (same reasoning as the gateway diamond above).
function DataObjectNode({ data, selected }: NodeProps<ShapeNode>) {
  return (
    <div className="diagram-node--data-object-outer">
      <ShapeResizer
        selected={selected}
        minWidth={50}
        minHeight={60}
        keepAspectRatio={false}
      />
      <div
        className="diagram-node--data-object-bg"
        style={{ background: data.color ?? DEFAULT_NODE_BACKGROUND.dataObject }}
      />
      <ShapeHandles />
      <span
        className="diagram-node__label"
        style={{
          // The folded-corner bg's `clip-path` gives it its own stacking
          // context (z-index: 0, set in CSS), so the label needs to be
          // positioned with a higher z-index to paint above it.
          position: "relative",
          zIndex: 1,
          color: data.textColor ?? DEFAULT_CAPTION_TEXT_COLOR,
          fontSize: data.fontSize ?? DEFAULT_NODE_FONT_SIZE,
        }}
      >
        {data.label}
      </span>
    </div>
  );
}

export const nodeTypes = {
  task: TaskNode,
  startEvent: EventNode,
  intermediateEvent: EventNode,
  endEvent: EventNode,
  exclusiveGateway: GatewayNode,
  parallelGateway: GatewayNode,
  inclusiveGateway: GatewayNode,
  complexGateway: GatewayNode,
  eventBasedGateway: GatewayNode,
  hint: HintNode,
  dataObject: DataObjectNode,
};