import React, { useState, useEffect, useRef, Suspense, lazy } from "react";
import { toast } from "react-toastify";
import { Button } from "@mui/joy";
import { Accordion, AccordionTab } from "primereact/accordion";
import { AutoComplete } from "primereact/autocomplete";
import BreadcrumbNav from "./BreadcrumbNav";
import { API_URL, ENVIRONMENT } from "@/config";

export default function MediaRequestForm() {
    const [type, setType] = useState("artist");
    const [selectedArtist, setSelectedArtist] = useState(null);
    const [artistInput, setArtistInput] = useState("");
    const [albumInput, setAlbumInput] = useState("");
    const [trackInput, setTrackInput] = useState("");
    const [selectedItem, setSelectedItem] = useState(null);
    const [albums, setAlbums] = useState([]);
    const [tracksByAlbum, setTracksByAlbum] = useState({});
    const [selectedTracks, setSelectedTracks] = useState({});
    const [artistSuggestions, setArtistSuggestions] = useState([]);
    const [isSubmitting, setIsSubmitting] = useState(false);
    const [isSearching, setIsSearching] = useState(false);
    const [loadingAlbumId, setLoadingAlbumId] = useState(null);
    const [expandedAlbums, setExpandedAlbums] = useState([]);

    const debounceTimeout = useRef(null);
    const autoCompleteRef = useRef(null);

    const delay = (ms) => new Promise((resolve) => setTimeout(resolve, ms)); // Helper for delays

    // Helper fetch wrapper that includes cookies automatically
    const authFetch = async (url, options = {}) => {
        const opts = {
            ...options,
            credentials: "include",  // <--- send HttpOnly cookies with requests
        };
        return fetch(url, opts);
    };


    const Spinner = () => (
        <span
            className="inline-block ml-2 h-4 w-4 border-2 border-t-2 border-gray-300 border-t-blue-600 rounded-full animate-spin"
            aria-label="Loading"
        />
    );

    // Fetch artist suggestions for autocomplete
    const searchArtists = (e) => {
        const query = e.query.trim();
        if (!query) {
            setArtistSuggestions([]);
            setSelectedArtist(null);
            return;
        }

        if (debounceTimeout.current) clearTimeout(debounceTimeout.current);

        debounceTimeout.current = setTimeout(async () => {
            try {
                // Ensure at least 600ms between actual requests
                const now = Date.now();
                if (!searchArtists.lastCall) searchArtists.lastCall = 0;
                const elapsed = now - searchArtists.lastCall;
                const minDelay = 600; // ms
                if (elapsed < minDelay) await delay(minDelay - elapsed);

                searchArtists.lastCall = Date.now();

                const res = await authFetch(
                    `${API_URL}/trip/get_artists_by_name?artist=${encodeURIComponent(query)}`
                );
                if (!res.ok) throw new Error("API error");
                const data = await res.json();
                setArtistSuggestions(data);
            } catch (err) {
                toast.error("Failed to fetch artist suggestions.");
                setArtistSuggestions([]);
            }
        }, 500); // debounce 500ms
    };



    //helpers for string truncation
    const truncate = (text, maxLen) =>
        maxLen <= 3
            ? text.slice(0, maxLen)
            : text.length <= maxLen
                ? text
                : text.slice(0, maxLen - 3) + '...';

    const artistItemTemplate = (artist) => {
        if (!artist) return null;
        return <div>{truncate(artist.artist, 58)}</div>;
    };


    // Handle autocomplete input changes (typing/selecting)
    const handleArtistChange = (e) => {
        if (typeof e.value === "string") {
            setArtistInput(e.value);
            setSelectedArtist(null);
        } else if (e.value && typeof e.value === "object") {
            setSelectedArtist(e.value);
            setArtistInput(e.value.artist);
        } else {
            setArtistInput("");
            setSelectedArtist(null);
        }
    };

    // Search button click handler
    const handleSearch = async () => {
        setIsSearching(true);
        if (type === "artist") {
            if (!selectedArtist) {
                toast.error("Please select a valid artist from suggestions.");
                setIsSearching(false);
                return;
            }

            setSelectedItem(selectedArtist.artist);

            try {
                const res = await authFetch(
                    `${API_URL}/trip/get_albums_by_artist_id/${selectedArtist.id}`
                );
                if (!res.ok) throw new Error("API error");
                const data = await res.json();

                data.sort((a, b) =>
                    (b.release_date || "").localeCompare(a.release_date || "")
                );

                setAlbums(data);
                setTracksByAlbum({});
                setExpandedAlbums([]);

                // Set selectedTracks for all albums as null (means tracks loading/not loaded)
                setSelectedTracks(
                    data.reduce((acc, album) => {
                        acc[album.id] = null;
                        return acc;
                    }, {})
                );
            } catch (err) {
                toast.error("Failed to fetch albums for artist.");
                setAlbums([]);
                setTracksByAlbum({});
                setSelectedTracks({});
            }
        } else if (type === "album") {
            if (!artistInput.trim() || !albumInput.trim()) {
                toast.error("Artist and Album are required.");
                setIsSearching(false);
                return;
            }
            setSelectedItem(`${artistInput} - ${albumInput}`);
            setAlbums([]);
            setTracksByAlbum({});
            setSelectedTracks({});
        } else if (type === "track") {
            if (!artistInput.trim() || !trackInput.trim()) {
                toast.error("Artist and Track are required.");
                setIsSearching(false);
                return;
            }
            setSelectedItem(`${artistInput} - ${trackInput}`);
            setAlbums([]);
            setTracksByAlbum({});
            setSelectedTracks({});
        }
        setIsSearching(false);
    };

    const handleTrackClick = async (trackId, artist, title) => {
        try {
            const res = await authFetch(`${API_URL}/trip/get_track_by_id/${trackId}`);
            if (!res.ok) throw new Error("Failed to fetch track URL");
            const data = await res.json();

            if (data.stream_url) {
                const fileResponse = await authFetch(data.stream_url);
                if (!fileResponse.ok) throw new Error("Failed to fetch track file");

                const blob = await fileResponse.blob();
                const url = URL.createObjectURL(blob);

                const link = document.createElement("a");
                link.href = url;

                // Sanitize filename (remove / or other illegal chars)
                const sanitize = (str) => str.replace(/[\\/:*?"<>|]/g, "_");
                const filename = `${sanitize(artist)} - ${sanitize(title)}.flac`;

                link.download = filename;

                document.body.appendChild(link);
                link.click();

                link.remove();
                URL.revokeObjectURL(url);
            } else {
                toast.error("No stream URL returned for this track.");
            }
        } catch (error) {
            toast.error("Failed to get track download URL.");
            console.error(error);
        }
    };



    // Sequentially fetch tracks for albums not loaded yet
    useEffect(() => {
        if (type !== "artist" || albums.length === 0) return;

        let isCancelled = false;
        const albumsToFetch = albums.filter((a) => !tracksByAlbum[a.id]);
        if (albumsToFetch.length === 0) return;

        const fetchTracksSequentially = async () => {
            const minDelay = 600; // ms between API requests
            for (const album of albumsToFetch) {
                if (isCancelled) break;

                setLoadingAlbumId(album.id);

                try {
                    const now = Date.now();
                    if (!fetchTracksSequentially.lastCall) fetchTracksSequentially.lastCall = 0;
                    const elapsed = now - fetchTracksSequentially.lastCall;
                    if (elapsed < minDelay) await delay(minDelay - elapsed);
                    fetchTracksSequentially.lastCall = Date.now();

                    const res = await authFetch(`${API_URL}/trip/get_tracks_by_album_id/${album.id}`);
                    if (!res.ok) throw new Error("API error");
                    const data = await res.json();

                    if (isCancelled) break;

                    setTracksByAlbum((prev) => ({ ...prev, [album.id]: data }));
                    setSelectedTracks((prev) => ({
                        ...prev,
                        [album.id]: data.map((t) => String(t.id)),
                    }));
                } catch (err) {
                    toast.error(`Failed to fetch tracks for album ${album.album}.`);
                    setTracksByAlbum((prev) => ({ ...prev, [album.id]: [] }));
                    setSelectedTracks((prev) => ({ ...prev, [album.id]: [] }));
                }
            }
            setLoadingAlbumId(null);
        };

        fetchTracksSequentially();

        return () => {
            isCancelled = true;
        };
    }, [albums, type]);


    // Toggle individual track checkbox
    const toggleTrack = (albumId, trackId) => {
        setSelectedTracks((prev) => {
            const current = new Set(prev[albumId] || []);
            if (current.has(String(trackId))) current.delete(String(trackId));
            else current.add(String(trackId));
            return { ...prev, [albumId]: Array.from(current) };
        });
    };

    // Toggle album checkbox (select/deselect all tracks in album)
    const toggleAlbum = (albumId) => {
        const allTracks = tracksByAlbum[albumId]?.map((t) => String(t.id)) || [];
        setSelectedTracks((prev) => {
            const current = prev[albumId] || [];
            const allSelected = current.length === allTracks.length;
            return {
                ...prev,
                [albumId]: allSelected ? [] : [...allTracks],
            };
        });
    };

    // Attach scroll fix for autocomplete panel
    const attachScrollFix = () => {
        setTimeout(() => {
            const panel = document.querySelector(".p-autocomplete-panel");
            const items = panel?.querySelector(".p-autocomplete-items");
            if (items) {
                items.style.maxHeight = "200px";
                items.style.overflowY = "auto";
                items.style.overscrollBehavior = "contain";
                const wheelHandler = (e) => {
                    const delta = e.deltaY;
                    const atTop = items.scrollTop === 0;
                    const atBottom = items.scrollTop + items.clientHeight >= items.scrollHeight;
                    if ((delta < 0 && atTop) || (delta > 0 && atBottom)) {
                        e.preventDefault();
                    } else {
                        e.stopPropagation();
                    }
                };
                items.removeEventListener("wheel", wheelHandler);
                items.addEventListener("wheel", wheelHandler, { passive: false });
            }
        }, 0);
    };

    // Submit request handler with progress indicator
    const handleSubmitRequest = async () => {
        setIsSubmitting(true);
        try {
            // Example: simulate submission delay
            await new Promise((resolve) => setTimeout(resolve, 1500));
            const allSelectedIds = Object.values(selectedTracks)
                .filter(arr => Array.isArray(arr)) // skip null entries
                .flat();
            toast.success(`Request submitted! (${allSelectedIds.length} tracks)`);
            console.debug("Requested: ", selectedTracks);
            console.debug("Flattened: ", allSelectedIds);
        } catch (err) {
            toast.error("Failed to submit request.");
        } finally {
            setIsSubmitting(false);
        }
    };

    return (
        <div className="max-w-3xl mx-auto my-10 p-6 rounded-xl shadow-md bg-white dark:bg-neutral-900 text-neutral-900 dark:text-neutral-100 border border-neutral-200 dark:border-neutral-700">
            <style>{`
                        /* Accordion tab backgrounds & text */
                        .p-accordion-tab {
                            background-color: #ffffff;
                            color: #000000;
                        }
                        [data-theme="dark"] .p-accordion-tab {
                            background-color: #1e1e1e;
                            color: #ffffff;
                        }

                        /* Accordion header link */
                        .p-accordion-header .p-accordion-header-link {
                            background-color: #f9f9f9;
                            color: #000000;
                        }
                        [data-theme="dark"] .p-accordion-header .p-accordion-header-link {
                            background-color: #1e1e1e !important;
                            color: #ffffff !important;
                        }

                        /* Accordion content panel */
                        .p-accordion-content {
                            background-color: #fafafa;
                            color: #000000;
                        }
                        [data-theme="dark"] .p-accordion-content {
                            background-color: #2a2a2a;
                            color: #ffffff;
                        }

                        /* Track list UL/LI styling */
                        .p-accordion-content ul {
                            padding-left: 0;
                            margin: 0;
                            list-style: none;
                        }
                        [data-theme="dark"] .p-accordion-content ul {
                            color: #ffffff;
                        }

                        /* Track items */
                        .p-accordion-content li {
                            background-color: #fff;
                            border-bottom: 1px solid #e5e5e5;
                        }
                        [data-theme="dark"] .p-accordion-content li {
                            background-color: #2a2a2a;
                            border-bottom: 1px solid #444;
                        }

                        /* Checkboxes inside track list */
                        .p-accordion-content input[type="checkbox"] {
                            accent-color: #1d4ed8; /* optional for consistent dark mode styling */
                        }

                        /* Loading spinner (optional darker style) */
                        [data-theme="dark"] .animate-spin {
                            border-color: #555;
                            border-top-color: #1d4ed8;
                        }

                        /* Small text like audio quality, duration, version */
                        .p-accordion-content span {
                            color: #555;
                        }
                        [data-theme="dark"] .p-accordion-content span {
                            color: #aaa;
                        }
        `}</style>

            <BreadcrumbNav currentPage="request" />

            <div className="flex flex-col gap-6">
                <div className="flex gap-4">
                    <label className="flex items-center gap-2">
                        <input
                            type="radio"
                            value="artist"
                            checked={type === "artist"}
                            onChange={() => setType("artist")}
                        />
                        Artist
                    </label>
                    <label className="flex items-center gap-2">
                        <input
                            type="radio"
                            value="album"
                            checked={type === "album"}
                            onChange={() => setType("album")}
                        />
                        Album
                    </label>
                    <label className="flex items-center gap-2">
                        <input
                            type="radio"
                            value="track"
                            checked={type === "track"}
                            onChange={() => setType("track")}
                        />
                        Track
                    </label>
                </div>

                <div className="flex flex-col gap-4">
                    <AutoComplete
                        ref={autoCompleteRef}
                        value={selectedArtist || artistInput}
                        suggestions={artistSuggestions}
                        field="artist"
                        completeMethod={searchArtists}
                        onChange={handleArtistChange}
                        minLength={3}
                        placeholder="Artist"
                        dropdown
                        className="w-full"
                        inputClassName="w-full px-3 py-2 rounded border border-neutral-300 dark:border-neutral-600 text-black dark:text-white dark:bg-neutral-800"
                        onShow={attachScrollFix}
                        itemTemplate={artistItemTemplate}
                    />

                    {(type === "album" || type === "track") && (
                        <input
                            type="text"
                            className="w-full dark:bg-neutral-800 dark:text-white border border-neutral-300 dark:border-neutral-600 rounded px-3 py-2"
                            value={type === "album" ? albumInput : trackInput}
                            onChange={(e) =>
                                type === "album" ? setAlbumInput(e.target.value) : setTrackInput(e.target.value)
                            }
                            placeholder={type === "album" ? "Album" : "Track"}
                        />
                    )}

                    <Button onClick={handleSearch} disabled={isSearching}>
                        {isSearching ? (
                            <span className="flex items-center gap-2">
                                <span className="animate-spin h-4 w-4 border-2 border-t-2 border-gray-200 border-t-primary rounded-full"></span>
                                Searching...
                            </span>
                        ) : (
                            "Search"
                        )}
                    </Button>
                </div>

                {type === "artist" && albums.length > 0 && (
                    <>
                        <Accordion
                            multiple
                            className="mt-4"
                            activeIndex={expandedAlbums}
                            onTabChange={(e) => setExpandedAlbums(e.index)}
                        >
                            {albums.map(({ album, id, release_date }) => {
                                const allTracks = tracksByAlbum[id] || [];
                                const selected = selectedTracks[id];

                                // Album checkbox is checked if tracks not loaded (selected === null)
                                // or all tracks loaded and all selected
                                const allChecked =
                                    selected === null || (selected?.length === allTracks.length && allTracks.length > 0);
                                const someChecked =
                                    selected !== null && selected.length > 0 && selected.length < allTracks.length;

                                return (
                                    <AccordionTab
                                        key={id}
                                        header={
                                            <div className="flex items-center gap-2">
                                                <input
                                                    type="checkbox"
                                                    checked={allChecked}
                                                    ref={(el) => {
                                                        if (el) el.indeterminate = someChecked;
                                                    }}
                                                    onChange={() => toggleAlbum(id)}
                                                    onClick={(e) => e.stopPropagation()}
                                                    className="cursor-pointer"
                                                    aria-label={`Select all tracks for album ${album}`}
                                                />
                                                <span className="flex items-center">
                                                    {album}
                                                    {loadingAlbumId === id && <Spinner />}
                                                </span>
                                                <small className="ml-2 text-neutral-500 dark:text-neutral-400">({release_date})</small>
                                            </div>
                                        }

                                    >
                                        {allTracks.length > 0 ? (
                                            <ul className="text-sm">
                                                {allTracks.map((track) => (
                                                    <li key={track.id} className="py-1 flex items-center gap-2">
                                                        <input
                                                            type="checkbox"
                                                            checked={selected?.includes(String(track.id))}
                                                            onChange={() => toggleTrack(id, track.id)}
                                                            className="cursor-pointer"
                                                            aria-label={`Select track ${track.title} `}
                                                        />
                                                        <button
                                                            type="button"
                                                            onClick={() => handleTrackClick(track.id, selectedArtist.artist, track.title)}
                                                            className="font-medium text-blue-600 hover:underline cursor-pointer bg-transparent border-none p-0"
                                                            aria-label={`Download track ${track.title} `}
                                                        >
                                                            {track.title}
                                                        </button>
                                                        <span className="text-xs text-neutral-500">{track.audioQuality}</span>
                                                        {track.version && (
                                                            <span className="text-xs text-neutral-400">({track.version})</span>
                                                        )}
                                                        {track.duration && (
                                                            <span className="text-xs text-neutral-500 ml-auto tabular-nums">{track.duration}</span>
                                                        )}
                                                    </li>
                                                ))}

                                            </ul>
                                        ) : (
                                            <div className="text-sm italic text-neutral-600 dark:text-neutral-400">
                                                {tracksByAlbum[id] ? "No tracks found for this album." : "Loading tracks..."}
                                            </div>
                                        )}
                                    </AccordionTab>
                                );
                            })}
                        </Accordion>

                        <div className="flex justify-end">
                            <Button onClick={handleSubmitRequest} color="primary" className="mt-4" disabled={isSubmitting}>
                                {isSubmitting ? (
                                    <span className="flex items-center gap-2">
                                        <span className="animate-spin h-4 w-4 border-2 border-t-2 border-gray-200 border-t-primary rounded-full"></span>
                                        Submitting...
                                    </span>
                                ) : (
                                    "Submit Request"
                                )}
                            </Button>
                        </div>
                    </>
                )}
            </div>
        </div >
    );
}