import React, { useCallback, useEffect, useRef, useState } from 'react';
import { fetchData } from '../../fetching/Fetch.js';
import { SERVER_URL } from '../../constants.js';

function resolveMediaUrl(mediaUrl) {
    if (!mediaUrl) return null;
    return mediaUrl.startsWith('http') ? mediaUrl : `${SERVER_URL}${mediaUrl}`;
}

export default function AdCarousel({ tenantCode }) {
    const [ads, setAds] = useState([]);
    const [index, setIndex] = useState(0);
    const [error, setError] = useState(null);
    const timerRef = useRef(null);
    const videoRef = useRef(null);

    const clearTimer = useCallback(() => {
        if (timerRef.current) {
            clearTimeout(timerRef.current);
            timerRef.current = null;
        }
    }, []);

    const loadAds = useCallback(async () => {
        if (!tenantCode) return;
        try {
            const response = await fetchData(
                `${SERVER_URL}/api/v1/ads/${encodeURIComponent(tenantCode)}/active`,
                'GET'
            );
            if (!response.success) {
                setError('Could not load advertisements.');
                return;
            }
            const next = Array.isArray(response.data) ? response.data : [];
            setAds(next);
            setError(null);
            setIndex((current) => (next.length === 0 ? 0 : current % next.length));
        } catch (err) {
            console.error(err);
            setError('Could not load advertisements.');
        }
    }, [tenantCode]);

    useEffect(() => {
        loadAds();
        const interval = setInterval(loadAds, 60 * 1000);
        return () => clearInterval(interval);
    }, [loadAds]);

    const goNext = useCallback(() => {
        setIndex((current) => {
            if (ads.length === 0) return 0;
            return (current + 1) % ads.length;
        });
    }, [ads.length]);

    const currentAd = ads[index] ?? null;

    useEffect(() => {
        clearTimer();
        if (!currentAd) return undefined;

        if (currentAd.mediaType === 'IMAGE') {
            const durationMs = Math.max(1, Number(currentAd.durationSeconds) || 10) * 1000;
            timerRef.current = setTimeout(goNext, durationMs);
            return clearTimer;
        }

        // Videos advance on ended; fallback if play fails
        timerRef.current = setTimeout(goNext, 5 * 60 * 1000);
        return clearTimer;
    }, [currentAd, goNext, clearTimer]);

    useEffect(() => {
        const video = videoRef.current;
        if (!video || currentAd?.mediaType !== 'VIDEO') return undefined;

        let removeUnmuteListener = () => {};

        const onEnded = () => goNext();
        const scheduleFallbackAdvance = () => {
            clearTimer();
            const durationMs = Math.max(5, Number(currentAd.durationSeconds) || 15) * 1000;
            timerRef.current = setTimeout(goNext, durationMs);
        };

        video.addEventListener('ended', onEnded);
        video.muted = false;
        video.playsInline = true;

        const playPromise = video.play();
        if (playPromise?.catch) {
            playPromise.catch(() => {
                // Unmuted autoplay blocked — keep video playing muted, then unmute on gesture.
                video.muted = true;
                const mutedPlay = video.play();
                if (mutedPlay?.catch) {
                    mutedPlay.catch(scheduleFallbackAdvance);
                }

                const unmute = () => {
                    video.muted = false;
                    video.play()?.catch(() => {});
                };
                window.addEventListener('pointerdown', unmute, { once: true });
                removeUnmuteListener = () => window.removeEventListener('pointerdown', unmute);
            });
        }

        return () => {
            video.removeEventListener('ended', onEnded);
            removeUnmuteListener();
        };
    }, [currentAd, goNext, clearTimer]);

    if (error) {
        return (
            <section className="branch-display__ad-panel">
                <h2 className="branch-display__section-title">Pengiklanan</h2>
                <p className="branch-display__empty">{error}</p>
            </section>
        );
    }

    if (ads.length === 0) {
        return (
            <section className="branch-display__ad-panel">
                <h2 className="branch-display__section-title">Pengiklanan</h2>
                <p className="branch-display__empty">Tiada pengiklanan aktif.</p>
            </section>
        );
    }

    const src = resolveMediaUrl(currentAd.mediaUrl);

    return (
        <section className="branch-display__ad-panel">
            <div className="branch-display__ad-header">
                <h2 className="branch-display__section-title">Pengiklanan</h2>
            </div>
            <div className="branch-display__ad-stage">
                {currentAd.mediaType === 'VIDEO' ? (
                    <video
                        key={currentAd.id}
                        ref={videoRef}
                        className="branch-display__ad-media"
                        src={src}
                        playsInline
                        autoPlay
                    />
                ) : (
                    <img
                        key={currentAd.id}
                        className="branch-display__ad-media"
                        src={src}
                        alt={currentAd.title || currentAd.fileName || 'Advertisement'}
                    />
                )}
            </div>
            {currentAd.title ? (
                <p className="branch-display__ad-caption">{currentAd.title}</p>
            ) : null}
        </section>
    );
}