import { useLayoutEffect, useRef, useState } from "react";
import { Link } from "react-router-dom";
import { useStore } from "@/store";
import styles from "./CommercialGroup.module.css";
import Banner from "@/components/Banner";
import ParagraphSection from "@/components/layout/ParagraphSection";
import Section from "@/components/layout/Section";
import TopTabs from "@/components/layout/TopTabsSection/TopTabs";
import SectionTitle from "@/components/layout/SectionTitle";
import ScrollReveal from "@/components/ScrollReveal";
import BottomTabsSection from "@/components/layout/BottomTabsSection";

const FALLBACK_GRADIENT = "linear-gradient(135deg, #1a2a4a 0%, #2d4a7c 100%)";

function PlaceholderImage() {
    return <div className={styles.placeholder}>占位图</div>;
}

export default function BusinessCommercialGroup() {
    const appConfig = useStore((s) => s.appConfig);
    const { viewDetail = "查看详情" } = appConfig?.__global__?.others
    const data = appConfig?.business?.commercialGroup;
    const section3Data = data?.section3Data;
    const section4Data = data?.section4Data;

    const [activeTabIndex, setActiveTabIndex] = useState(0);
    const [activeFeaturesTabIndex, setActiveFeaturesTabIndex] = useState(0);

    const featuresHeroTabsRef = useRef<HTMLDivElement>(null);
    const featuresTabItemRefs = useRef<(HTMLDivElement | null)[]>([]);
    const [featuresTabIndicator, setFeaturesTabIndicator] = useState({ x: 0, width: 0 });

    const featuresFirstBg = section3Data?.tabItems?.[0]?.backgroundImage ?? "";
    const [featuresBg, setFeaturesBg] = useState({
        a: featuresFirstBg,
        b: featuresFirstBg,
        showA: true,
    });

    useLayoutEffect(() => {
        if (!section3Data?.tabItems?.length) return;
        const next = section3Data.tabItems[activeFeaturesTabIndex]?.backgroundImage ?? "";
        setFeaturesBg((prev) => {
            const visible = prev.showA ? prev.a : prev.b;
            if (next === visible) return prev;
            // 数据首帧就绪：直接铺满两层，避免从空图做一次淡入
            if (!visible && next) {
                return { a: next, b: next, showA: true };
            }
            if (prev.showA) {
                return { ...prev, b: next, showA: false };
            }
            return { ...prev, a: next, showA: true };
        });
    }, [activeFeaturesTabIndex, section3Data]);

    useLayoutEffect(() => {
        if (!section3Data?.tabItems?.length) return;
        const root = featuresHeroTabsRef.current;
        if (!root) return;

        const updateIndicator = () => {
            const tab = featuresTabItemRefs.current[activeFeaturesTabIndex];
            if (!tab) return;
            const rootRect = root.getBoundingClientRect();
            const tabRect = tab.getBoundingClientRect();
            setFeaturesTabIndicator({
                x: tabRect.left - rootRect.left,
                width: tabRect.width,
            });
        };

        updateIndicator();
        const ro = new ResizeObserver(updateIndicator);
        ro.observe(root);
        window.addEventListener("resize", updateIndicator);
        return () => {
            ro.disconnect();
            window.removeEventListener("resize", updateIndicator);
        };
    }, [activeFeaturesTabIndex, section3Data?.tabItems]);

    if (!data) return null;

    const banner = data.banner;
    const section1Data = data.section1Data;
    const section2Data = data.section2Data;

    return (
        <div>
            <Banner
                title={banner?.title ?? ""}
                largedesc={banner?.content}
                titleSize={banner?.titleSize as "medium" | "large" | undefined ?? "medium"}
                backgroundImage={banner?.backgroundImage ?? "/images/bg-commercial-group.png"}
            />

            {section1Data && <ParagraphSection data={section1Data} />}

            <Section
                background={section2Data.backgroundImage}
                className={styles.twoColSection}
            >
                <TopTabs className={styles.twoColSectionTabs} data={section2Data} activeIndex={activeTabIndex} setActiveIndex={setActiveTabIndex} />
                <div className={styles.twoColSectionContent}>
                    <ScrollReveal
                        preset="slideRight"
                        duration={1}
                        className={styles.twoColImageWrap}
                    >
                        <div className={styles.twoColImage} style={{
                            backgroundImage: `url(${section2Data.tabItems[activeTabIndex]?.sideImage as string})`,
                        }}>
                        </div>
                    </ScrollReveal>

                    <div className={styles.twoColText}>
                        <div className={styles.twoColTextContent}>
                            <ScrollReveal preset="slideUp" delay={0.5} >
                                <p className={styles.twoColDesc} dangerouslySetInnerHTML={{ __html: section2Data.tabItems[activeTabIndex]?.content ?? "" }}></p>
                            </ScrollReveal>
                            <Link
                                to={section2Data.tabItems[activeTabIndex]?.path ?? "#"}
                                className={styles.btnPrimary}
                            >
                                {viewDetail}
                            </Link>
                        </div>
                    </div>
                </div>
            </Section>


            {section3Data && <BottomTabsSection data={section3Data} />}

            {
                section4Data.hide ? null : (
                    <section
                        className={`${styles.twoColSection} ${styles.propertyServices}`}
                        style={{
                            backgroundImage: `url(${section4Data?.backgroundImage}), ${FALLBACK_GRADIENT}`,
                        }}
                    >
                        <div className={styles.propertyServicesContent}>
                            <div className={styles.propertyServicesTitle}>{section4Data?.title}</div>
                            <p className={styles.propertyServicesSubtitle}>{section4Data?.content}</p>
                            <ScrollReveal preset="slideUp" className={styles.propertyServicesBtn}>
                                <Link to={section4Data?.path ?? "#"} >
                                    {viewDetail}
                                </Link>
                            </ScrollReveal>
                        </div>
                    </section>
                )
            }
        </div>
    );
}