"use client";

import { useCallback, useLayoutEffect, useRef, useState } from "react";

import { milestones } from "@/components/roadmap/milestones";
import { TimelineItem } from "@/components/roadmap/timeline-item";
import { TimelineRail } from "@/components/roadmap/timeline-rail";
import {
  getMilestoneSide,
} from "@/components/roadmap/timeline-config";
import { useActiveTimelineItem } from "@/components/roadmap/use-active-timeline-item";
import { Container } from "@/components/container";
import { MotionReveal } from "@/components/motion-reveal";
import { layout } from "@/lib/layout";
import { type } from "@/lib/typography";
import { cn } from "@/lib/utils";

type RoadmapSectionProps = {
  className?: string;
};

/** Stacked timeline (nodes above cards) below Tailwind `lg`. */
const STACKED_RAIL_MQ = "(max-width: 1023px)";

export function RoadmapSection({ className }: RoadmapSectionProps) {
  const sectionRef = useRef<HTMLElement>(null);
  const trackRef = useRef<HTMLDivElement>(null);
  const nodeRefs = useRef<(HTMLDivElement | null)[]>([]);
  const cardRefs = useRef<(HTMLElement | null)[]>([]);
  const [railMetrics, setRailMetrics] = useState({
    offsetTop: 0,
    trackHeight: 0,
    progressHeight: 0,
  });

  const { activeIndex, setItemRef, selectActiveIndex } = useActiveTimelineItem(
    milestones.length,
    sectionRef
  );

  const setNodeRef = useCallback(
    (index: number) => (element: HTMLDivElement | null) => {
      nodeRefs.current[index] = element;
    },
    []
  );

  const setCardRef = useCallback(
    (index: number) => (element: HTMLElement | null) => {
      cardRefs.current[index] = element;
    },
    []
  );

  const updateRailMetrics = useCallback(() => {
    const track = trackRef.current;
    const firstNode = nodeRefs.current[0];
    const lastNode = nodeRefs.current[milestones.length - 1];
    const activeNode = nodeRefs.current[activeIndex];
    if (!track || !firstNode || !lastNode || !activeNode) return;

    const trackTop = track.getBoundingClientRect().top;
    const stacked =
      typeof window !== "undefined" &&
      window.matchMedia(STACKED_RAIL_MQ).matches;

    if (stacked) {
      const firstCard = cardRefs.current[0];
      const lastCard = cardRefs.current[milestones.length - 1];
      const activeCard = cardRefs.current[activeIndex];
      if (!firstCard || !lastCard || !activeCard) return;

      // Card centers keep the rail behind end cards — never above the first
      // or below the last (nodes sit above cards in the stacked layout).
      const firstRect = firstCard.getBoundingClientRect();
      const lastRect = lastCard.getBoundingClientRect();
      const activeRect = activeCard.getBoundingClientRect();
      const railStart =
        firstRect.top + firstRect.height / 2 - trackTop;
      const railEnd = lastRect.top + lastRect.height / 2 - trackTop;
      const activeCenter =
        activeRect.top + activeRect.height / 2 - trackTop;

      setRailMetrics({
        offsetTop: railStart,
        trackHeight: Math.max(0, railEnd - railStart),
        progressHeight: Math.max(0, activeCenter - railStart),
      });
      return;
    }

    const firstCenter =
      firstNode.getBoundingClientRect().top + firstNode.offsetHeight / 2;
    const lastCenter =
      lastNode.getBoundingClientRect().top + lastNode.offsetHeight / 2;
    const activeCenter =
      activeNode.getBoundingClientRect().top + activeNode.offsetHeight / 2;

    setRailMetrics({
      offsetTop: firstCenter - trackTop,
      trackHeight: Math.max(0, lastCenter - firstCenter),
      progressHeight: Math.max(0, activeCenter - firstCenter),
    });
  }, [activeIndex]);

  useLayoutEffect(() => {
    updateRailMetrics();
    window.addEventListener("resize", updateRailMetrics, { passive: true });
    window.addEventListener("scroll", updateRailMetrics, { passive: true });

    const media = window.matchMedia(STACKED_RAIL_MQ);
    const onMediaChange = () => updateRailMetrics();
    media.addEventListener("change", onMediaChange);

    const track = trackRef.current;
    const observer =
      track && typeof ResizeObserver !== "undefined"
        ? new ResizeObserver(updateRailMetrics)
        : null;
    if (track) observer?.observe(track);

    return () => {
      window.removeEventListener("resize", updateRailMetrics);
      window.removeEventListener("scroll", updateRailMetrics);
      media.removeEventListener("change", onMediaChange);
      observer?.disconnect();
    };
  }, [updateRailMetrics]);

  return (
    <section
      ref={sectionRef}
      id="roadmap"
      className={cn(
        "timeline-section section-shell bg-section-canvas",
        layout.sectionY,
        layout.scrollMargin,
        className
      )}
    >
      <Container className="section-content">
        <MotionReveal>
          <header className="relative mb-8 text-center md:mb-10">
            <div className="local-highlight local-highlight--soft" aria-hidden />
            <p
              className={cn(
                type.eyebrow,
                "relative mb-2 text-center text-primary"
              )}
            >
              مسیر همکاری
            </p>
            <h2
              className={cn(
                type.h2,
                "relative text-center text-balance text-foreground"
              )}
            >
              نقشه راه امین رایان
            </h2>
            <p
              className={cn(
                type["body-sm"],
                "relative mx-auto mt-3 max-w-md text-center text-muted-foreground"
              )}
            >
              هر مرحله با اسکرول یا کلیک فعال می‌شود
            </p>
          </header>
        </MotionReveal>

        {/* dir=ltr keeps physical left/right card alternation consistent */}
        <div
          ref={trackRef}
          dir="ltr"
          className="timeline-track relative mx-auto max-w-4xl"
        >
          <TimelineRail
            offsetTop={railMetrics.offsetTop}
            trackHeight={railMetrics.trackHeight}
            progressHeight={railMetrics.progressHeight}
            className="left-1/2"
          />

          <ol className="relative z-10 m-0 list-none p-0">
            {milestones.map((milestone, index) => (
              <TimelineItem
                key={milestone.id}
                milestone={milestone}
                index={index}
                side={getMilestoneSide(index)}
                active={activeIndex === index}
                completed={index < activeIndex}
                itemRef={setItemRef(index)}
                nodeRef={setNodeRef(index)}
                cardRef={setCardRef(index)}
                onSelect={() => selectActiveIndex(index)}
              />
            ))}
          </ol>
        </div>
      </Container>
    </section>
  );
}