import {
  useCallback,
  useEffect,
  useLayoutEffect,
  useRef,
  useState,
  type CSSProperties,
  type KeyboardEvent,
  type PointerEvent as ReactPointerEvent,
} from "react";
import {
  clampHudPositionToViewport,
  type NormalizedHudPosition,
} from "../game/hudLayout";
import type { ThreatMeterRow } from "../game/threatMeter";

export interface ThreatMeterWidgetProps {
  readonly targetName: string;
  readonly rows: readonly ThreatMeterRow[];
  readonly position: NormalizedHudPosition;
  readonly onPositionChange: (position: NormalizedHudPosition) => void;
}

interface DragState {
  readonly pointerId: number;
  readonly offsetX: number;
  readonly offsetY: number;
}

function positionsMatch(left: NormalizedHudPosition, right: NormalizedHudPosition): boolean {
  return Math.abs(left.x - right.x) < 0.0001 && Math.abs(left.y - right.y) < 0.0001;
}

export function ThreatMeterWidget({
  targetName,
  rows,
  position,
  onPositionChange,
}: ThreatMeterWidgetProps) {
  const panelRef = useRef<HTMLElement>(null);
  const dragRef = useRef<DragState | null>(null);
  const latestPositionRef = useRef(position);
  const [localPosition, setLocalPosition] = useState(position);
  latestPositionRef.current = localPosition;

  useEffect(() => {
    if (dragRef.current || positionsMatch(position, latestPositionRef.current)) return;
    latestPositionRef.current = position;
    setLocalPosition(position);
  }, [position]);

  const constrain = useCallback((candidate: NormalizedHudPosition) => {
    const rect = panelRef.current?.getBoundingClientRect();
    return clampHudPositionToViewport(
      candidate,
      { width: window.innerWidth, height: window.innerHeight },
      { width: rect?.width ?? 156, height: rect?.height ?? 92 },
    );
  }, []);

  const setConstrainedPosition = useCallback((candidate: NormalizedHudPosition, commit: boolean) => {
    const next = constrain(candidate);
    latestPositionRef.current = next;
    setLocalPosition(next);
    if (commit) onPositionChange(next);
  }, [constrain, onPositionChange]);

  useLayoutEffect(() => {
    const keepVisible = () => {
      const next = constrain(latestPositionRef.current);
      if (!positionsMatch(next, latestPositionRef.current)) setConstrainedPosition(next, true);
    };
    keepVisible();
    window.addEventListener("resize", keepVisible);
    return () => window.removeEventListener("resize", keepVisible);
  }, [constrain, setConstrainedPosition]);

  useEffect(() => {
    const moveDrag = (event: PointerEvent) => {
      const drag = dragRef.current;
      if (!drag || drag.pointerId !== event.pointerId) return;
      event.preventDefault();
      event.stopPropagation();
      setConstrainedPosition({
        x: (event.clientX - drag.offsetX) / Math.max(1, window.innerWidth),
        y: (event.clientY - drag.offsetY) / Math.max(1, window.innerHeight),
      }, false);
    };

    const finishDrag = (event: PointerEvent) => {
      const drag = dragRef.current;
      if (!drag || drag.pointerId !== event.pointerId) return;
      event.preventDefault();
      event.stopPropagation();
      dragRef.current = null;
      panelRef.current?.classList.remove("is-dragging");
      onPositionChange(latestPositionRef.current);
    };

    window.addEventListener("pointermove", moveDrag);
    window.addEventListener("pointerup", finishDrag);
    window.addEventListener("pointercancel", finishDrag);
    return () => {
      window.removeEventListener("pointermove", moveDrag);
      window.removeEventListener("pointerup", finishDrag);
      window.removeEventListener("pointercancel", finishDrag);
    };
  }, [onPositionChange, setConstrainedPosition]);

  const beginDrag = (event: ReactPointerEvent<HTMLButtonElement>) => {
    if (event.button !== 0) return;
    event.preventDefault();
    event.stopPropagation();
    if (document.pointerLockElement) document.exitPointerLock();
    const rect = panelRef.current?.getBoundingClientRect();
    dragRef.current = {
      pointerId: event.pointerId,
      offsetX: event.clientX - (rect ? rect.left + rect.width / 2 : event.clientX),
      offsetY: event.clientY - (rect ? rect.top + rect.height / 2 : event.clientY),
    };
    event.currentTarget.setPointerCapture(event.pointerId);
    panelRef.current?.classList.add("is-dragging");
  };

  const moveWithKeyboard = (event: KeyboardEvent<HTMLButtonElement>) => {
    const direction = {
      ArrowLeft: [-1, 0],
      ArrowRight: [1, 0],
      ArrowUp: [0, -1],
      ArrowDown: [0, 1],
    }[event.key];
    if (!direction) return;
    event.preventDefault();
    event.stopPropagation();
    const step = event.shiftKey ? 0.05 : 0.015;
    setConstrainedPosition({
      x: latestPositionRef.current.x + direction[0] * step,
      y: latestPositionRef.current.y + direction[1] * step,
    }, true);
  };

  const currentTarget = rows.find((row) => row.currentTarget) ?? null;
  const widgetStyle = {
    left: `${localPosition.x * 100}%`,
    top: `${localPosition.y * 100}%`,
  } as CSSProperties;

  return (
    <section
      ref={panelRef}
      className="threat-widget"
      style={widgetStyle}
      aria-label={`Threat meter for ${targetName}`}
      onPointerDown={(event) => event.stopPropagation()}
    >
      <button
        type="button"
        className="threat-widget__drag-handle"
        aria-label={`Move threat meter for ${targetName}. Use arrow keys for precise movement.`}
        onPointerDown={beginDrag}
        onKeyDown={moveWithKeyboard}
      >
        <strong>Threat</strong>
        <span>{targetName}</span>
        <i aria-hidden="true">::</i>
      </button>
      <div className="threat-widget__victim">
        <span>Target</span>
        <b>{currentTarget?.name ?? "None"}</b>
      </div>
      <div className="threat-widget__rows">
        {rows.map((row) => (
          <div
            key={row.actorId}
            className={`threat-widget__row threat-widget__row--${row.role} ${row.currentTarget ? "is-target" : ""} ${row.forced ? "is-forced" : ""}`}
          >
            <span><b>{row.name}</b><i>{row.forced ? "TAUNT" : `${Math.round(row.percentOfLeader)}%`}</i></span>
            <em aria-hidden="true"><i style={{ width: `${row.percentOfLeader}%` }} /></em>
          </div>
        ))}
      </div>
    </section>
  );
}