"use client";

import { useState, useRef, useCallback, useEffect } from "react";
import Image from "next/image";
import { UI_CONFIG } from "@/lib/config";
import type { TeamMember } from "@/types/content";

const {
  autoPlayMs: AUTO_PLAY_MS,
  pauseMs: PAUSE_MS,
  cardSpacing: CARD_SPACING,
} = UI_CONFIG.team;

function wrapIndex(i: number, total: number) {
  return ((i % total) + total) % total;
}

function getDiff(index: number, active: number, total: number) {
  let diff = index - active;
  if (diff > total / 2) diff -= total;
  if (diff < -total / 2) diff += total;
  return diff;
}

function lerp(a: number, b: number, t: number) {
  return a + (b - a) * t;
}

function clamp(v: number, min: number, max: number) {
  return Math.max(min, Math.min(max, v));
}

// Slot properties for each position (0=center, 1=near, 2=mid, 3=far, 4=hidden)
const SLOTS = [
  { w: 280, h: 400, opacity: 1, scale: 1, x: 0, brightness: 1, grayscale: 0, z: 10, border: true },
  { w: 220, h: 340, opacity: 0.8, scale: 0.97, x: 260, brightness: 0.6, grayscale: 0.2, z: 5, border: false },
  { w: 180, h: 280, opacity: 0.6, scale: 0.93, x: 470, brightness: 0.45, grayscale: 0.35, z: 3, border: false },
  { w: 150, h: 230, opacity: 0.35, scale: 0.88, x: 640, brightness: 0.3, grayscale: 0.5, z: 2, border: false },
  { w: 120, h: 180, opacity: 0, scale: 0.83, x: 780, brightness: 0.2, grayscale: 0.8, z: 1, border: false },
];

interface TeamCarouselProps {
  members: TeamMember[];
  activeIndex: number;
  onActiveChange: (index: number) => void;
}

export function TeamCarousel({ members, activeIndex, onActiveChange }: TeamCarouselProps) {
  const total = members.length;
  const [dragOffset, setDragOffset] = useState(0);
  const isDraggingRef = useRef(false);
  const wasDragRef = useRef(false);
  const pausedUntilRef = useRef(0);
  const dragStartRef = useRef<{ x: number; startIndex: number } | null>(null);

  // Pause auto-rotation when activeIndex changes externally (e.g. dot click)
  const prevIndexRef = useRef(activeIndex);
  useEffect(() => {
    if (prevIndexRef.current !== activeIndex) {
      prevIndexRef.current = activeIndex;
      pausedUntilRef.current = Date.now() + PAUSE_MS;
    }
  }, [activeIndex]);

  // Auto-rotate — completely skip while dragging
  useEffect(() => {
    const id = setInterval(() => {
      if (isDraggingRef.current) return;
      if (Date.now() < pausedUntilRef.current) return;
      onActiveChange((activeIndex + 1) % total);
    }, AUTO_PLAY_MS);
    return () => clearInterval(id);
  }, [total, activeIndex, onActiveChange]);

  // Pointer handlers
  const onPointerDown = useCallback(
    (e: React.PointerEvent) => {
      (e.target as HTMLElement).setPointerCapture(e.pointerId);
      isDraggingRef.current = true;
      wasDragRef.current = false;
      dragStartRef.current = { x: e.clientX, startIndex: activeIndex };
      setDragOffset(0);
    },
    [activeIndex]
  );

  const onPointerMove = useCallback(
    (e: React.PointerEvent) => {
      if (!dragStartRef.current) return;
      const dx = e.clientX - dragStartRef.current.x;
      if (Math.abs(dx) > 10) wasDragRef.current = true;
      setDragOffset(dx);
    },
    []
  );

  const onPointerUp = useCallback(() => {
    if (!dragStartRef.current) return;
    const startIdx = dragStartRef.current.startIndex;
    const currentOffset = dragOffset;
    const wasDrag = Math.abs(currentOffset) > 10;
    const steps = wasDrag ? Math.round(currentOffset / CARD_SPACING) : 0;
    dragStartRef.current = null;
    isDraggingRef.current = false;
    pausedUntilRef.current = Date.now() + PAUSE_MS;
    if (steps !== 0) {
      // Update index and reset offset in the same batch so the old card
      // never becomes center for a frame (prevents label flash)
      onActiveChange(wrapIndex(startIdx - steps, total));
    }
    setDragOffset(0);
  }, [total, dragOffset, onActiveChange]);

  // Compute interpolated style for each card
  const baseIndex = dragStartRef.current ? dragStartRef.current.startIndex : activeIndex;

  function getCardStyle(index: number) {
    const baseDiff = getDiff(index, baseIndex, total);
    const fractionalShift = dragOffset / CARD_SPACING;
    const continuousDiff = baseDiff + fractionalShift;
    const absDiff = Math.abs(continuousDiff);

    if (absDiff > 4) return null;

    const lowerSlot = Math.floor(absDiff);
    const upperSlot = Math.ceil(absDiff);
    const t = absDiff - lowerSlot;

    const s0 = SLOTS[clamp(lowerSlot, 0, 4)];
    const s1 = SLOTS[clamp(upperSlot, 0, 4)];

    const sign = continuousDiff >= 0 ? 1 : -1;
    const x = sign * lerp(s0.x, s1.x, t);
    const w = lerp(s0.w, s1.w, t);
    const h = lerp(s0.h, s1.h, t);
    const opacity = lerp(s0.opacity, s1.opacity, t);
    const scale = lerp(s0.scale, s1.scale, t);
    const brightness = lerp(s0.brightness, s1.brightness, t);
    const grayscale = lerp(s0.grayscale, s1.grayscale, t);
    const z = Math.round(lerp(s0.z, s1.z, t));
    const showBorder = absDiff < 0.5;

    if (opacity < 0.02) return null;

    return {
      width: w,
      height: h,
      opacity,
      zIndex: z,
      transform: `translateX(${x}px) scale(${scale})`,
      filter: `brightness(${brightness}) grayscale(${grayscale})`,
      borderColor: showBorder ? "rgba(201,169,110,0.3)" : "transparent",
      boxShadow: showBorder
        ? "0 0 60px rgba(201,169,110,0.12)"
        : "none",
      transition: isDraggingRef.current
        ? "none"
        : "all 0.8s cubic-bezier(0.25, 0.46, 0.45, 0.94)",
      isCenter: absDiff < 0.5,
      /** 1 at center, fades to 0 by absDiff=0.6 */
      centerOpacity: clamp(1 - absDiff / 0.6, 0, 1),
    };
  }

  return (
    <div
      className="relative mx-auto flex items-end justify-center cursor-grab select-none active:cursor-grabbing touch-pan-y"
      style={{ height: UI_CONFIG.team.stageHeight }}
      onPointerDown={onPointerDown}
      onPointerMove={onPointerMove}
      onPointerUp={onPointerUp}
      onPointerCancel={onPointerUp}
      onLostPointerCapture={onPointerUp}
    >
      {/* Spotlight cone */}
      <div
        className="pointer-events-none absolute left-1/2 -translate-x-1/2 bottom-0"
        style={{
          width: 400,
          height: 500,
          background:
            "conic-gradient(from 180deg at 50% 0%, transparent 30%, rgba(201,169,110,0.06) 45%, rgba(201,169,110,0.1) 50%, rgba(201,169,110,0.06) 55%, transparent 70%)",
        }}
      />

      {/* Cards */}
      {members.map((m, i) => {
        const style = getCardStyle(i);
        if (!style) return null;

        return (
          <div
            key={m.name}
            onClick={() => {
              if (!style.isCenter && !wasDragRef.current) {
                onActiveChange(i);
                pausedUntilRef.current = Date.now() + PAUSE_MS;
              }
            }}
            className={`absolute bottom-0 overflow-hidden rounded-2xl border ${style.isCenter ? "team-card-glitter" : "cursor-pointer"} pointer-events-auto`}
            style={{
              width: style.width,
              height: style.height,
              opacity: style.opacity,
              zIndex: style.zIndex,
              transform: style.transform,
              filter: style.filter,
              borderColor: style.isCenter ? "transparent" : style.borderColor,
              boxShadow: style.isCenter
                ? "0 0 40px rgba(201,169,110,0.15), 0 0 80px rgba(201,169,110,0.08)"
                : style.boxShadow,
              transition: style.transition,
            }}
          >
            <Image
              src={m.image}
              alt={m.name}
              fill
              loading="lazy"
              sizes="280px"
              className="object-cover"
              draggable={false}
            />

            {style.centerOpacity > 0 && (
              <>
                <div
                  className="absolute inset-0 bg-gradient-to-t from-black/80 via-black/10 to-transparent"
                  style={{ opacity: style.centerOpacity }}
                />
                <div
                  className="absolute bottom-0 left-0 right-0 p-5"
                  style={{ opacity: style.centerOpacity }}
                >
                  <h3 className="text-lg font-bold text-white sm:text-xl drop-shadow-lg">
                    {m.name}
                  </h3>
                  <p className="text-sm font-medium text-gold-light drop-shadow-lg">
                    {m.role}
                  </p>
                </div>
              </>
            )}
          </div>
        );
      })}
    </div>
  );
}
