"use client";

import React, { useEffect, useMemo, useState, useCallback } from "react";
import {
    Loader2,
    Download,
    Folder,
    FileText,
    RefreshCw,
    ArrowUp,
    Home,
} from "lucide-react";

type FileItem = {
    name: string;
    type: "dir" | "file";
    size?: number;
    mtimeMs?: number;
};

type ListResponse =
| { path: string; items: FileItem[] }
| { path: string; entries: FileItem[] }
| { items?: FileItem[]; entries?: FileItem[]; path?: string };

const BASE =
(process.env.NEXT_PUBLIC_FILE_API_BASE_URL || "").replace(/\/$/, "") || "";

function joinPath(a: string, b: string) {
    if (!a || a === "/") return b.startsWith("/") ? b : `/${b}`;
    return `${a.replace(/\/$/, "")}/${b.replace(/^\//, "")}`;
}
function parentPath(path: string) {
    if (!path || path === "/") return "/";
    const parts = path.replace(/\/+$/, "").split("/");
    parts.pop();
    const p = parts.join("/");
    return p === "" ? "/" : p;
}
function formatSize(bytes?: number) {
    if (bytes == null) return "—";
    const units = ["B", "KB", "MB", "GB", "TB"];
    let v = bytes;
    let u = 0;
    while (v >= 1024 && u < units.length - 1) {
        v /= 1024;
        u++;
    }
    return `${v.toFixed(u ? 1 : 0)} ${units[u]}`;
}

export default function FileBrowserPanel() {
    const [path, setPath] = useState<string>("/");
    const [items, setItems] = useState<FileItem[]>([]);
    const [loading, setLoading] = useState(false);
    const [error, setError] = useState<string | null>(null);
    const [previewHref, setPreviewHref] = useState<string | null>(null);

    const urlList = useMemo(() => {
        const p = encodeURIComponent(path || "/");
        return `${BASE}/api/files/list?path=${p}`;
    }, [path]);
    const urlDownload = useCallback((p: string) => {
        const qp = encodeURIComponent(p || "/");
        return `${BASE}/api/files/download?path=${qp}`;
    }, []);
    const urlRaw = useCallback((p: string) => {
        const qp = encodeURIComponent(p || "/");
        return `${BASE}/api/files/raw?path=${qp}`;
    }, []);

    const fetchList = useCallback(async () => {
        setLoading(true);
        setError(null);
        setPreviewHref(null);
        try {
            const res = await fetch(urlList, {
                method: "GET",
                credentials: "include",
                headers: { Accept: "application/json" },
                cache: "no-store",
            });
            if (!res.ok) {
                const text = await res.text().catch(() => "");
                throw new Error(text || `HTTP ${res.status}`);
            }
            const json: ListResponse = await res.json();
            const arr = (json as any).items || (json as any).entries || [];
            if (!Array.isArray(arr)) throw new Error("Malformed list response");
            arr.sort((a: FileItem, b: FileItem) => {
                if (a.type !== b.type) return a.type === "dir" ? -1 : 1;
                return a.name.localeCompare(b.name);
            });
            setItems(arr);
        } catch (e: any) {
            setError(e?.message || String(e));
            setItems([]);
        } finally {
            setLoading(false);
        }
    }, [urlList]);

    useEffect(() => {
        fetchList();
    }, [fetchList]);

    const onOpen = (it: FileItem) => {
        if (it.type === "dir") {
            setPath((p) => joinPath(p, it.name));
        } else {
            setPreviewHref(urlRaw(joinPath(path, it.name)));
        }
    };
    const onUp = () => setPath((p) => parentPath(p));
    const onHome = () => setPath("/");
    const onDownload = (it: FileItem) => {
        const href = urlDownload(joinPath(path, it.name));
        const a = document.createElement("a");
        a.href = href;
        a.download = it.name;
        document.body.appendChild(a);
        a.click();
        a.remove();
    };

    return (
        <div className="space-y-3">
        <style>{`
            @media (min-width: 1024px) {
                .fs-grid {
                    display: grid;
                    grid-template-columns: 1fr clamp(340px, 36vw, 480px);
                    gap: 1rem;
                }
            }
            `}</style>

            <div className="flex items-center gap-2">
            <button
            onClick={onHome}
            className="inline-flex items-center gap-2 rounded-md border px-3 py-1.5 text-sm hover:bg-muted"
            title="Root"
            >
            <Home className="h-4 w-4" /> root
            </button>
            <div className="ml-auto flex items-center gap-2">
            <button
            onClick={fetchList}
            className="inline-flex items-center gap-2 rounded-md border px-3 py-1.5 text-sm hover:bg-muted"
            title="Refresh"
            >
            <RefreshCw className="h-4 w-4" /> Refresh
            </button>
            <button
            onClick={onUp}
            className="inline-flex items-center gap-2 rounded-md border px-3 py-1.5 text-sm hover:bg-muted"
            title="Up one folder"
            >
            <ArrowUp className="h-4 w-4" /> Up
            </button>
            </div>
            </div>

            <div className="text-xs text-muted-foreground select-all">{path || "/"}</div>

            <div className="fs-grid">
            {/* TABLE */}
            <div className="rounded-md border overflow-hidden">
            <div className="overflow-x-auto">
            <div className="min-w-[560px]">
            {/* compact column plan: name grows; others stay tidy */}
            <div className="grid grid-cols-[minmax(260px,1fr),88px,92px,156px,auto] items-center bg-muted px-3 py-2 text-sm font-medium">
            <div>Name</div>
            <div>Type</div>
            <div>Size</div>
            <div>Modified</div>
            <div className="text-right">Actions</div>
            </div>

            <div className="divide-y">
            {loading ? (
                <div className="p-6 text-sm text-muted-foreground flex items-center gap-2">
                <Loader2 className="h-4 w-4 animate-spin" /> Loading…
                </div>
            ) : error ? (
                <div className="p-6 text-sm text-rose-400">Error: {error}</div>
            ) : items.length === 0 ? (
                <div className="p-6 text-sm text-muted-foreground">Empty folder.</div>
            ) : (
                items.map((it) => (
                    <div
                    key={it.name + it.type}
                    className="grid grid-cols-[minmax(260px,1fr),88px,92px,156px,auto] items-center px-3 py-2 text-sm hover:bg-muted/50"
                    >
                    <button
                    className="text-left inline-flex items-center gap-2 hover:underline min-w-0"
                    onClick={() => onOpen(it)}
                    title={it.type === "dir" ? "Open folder" : "Preview"}
                    >
                    {it.type === "dir" ? (
                        <Folder className="h-4 w-4 shrink-0" />
                    ) : (
                        <FileText className="h-4 w-4 shrink-0" />
                    )}
                    <span className="truncate">{it.name}</span>
                    </button>
                    <div className="uppercase tracking-wide text-[11px] text-muted-foreground">
                    {it.type}
                    </div>
                    <div className="text-muted-foreground">{formatSize(it.size)}</div>
                    <div className="text-muted-foreground">
                    {it.mtimeMs ? new Date(it.mtimeMs).toLocaleString() : "—"}
                    </div>
                    <div className="text-right">
                    {it.type === "file" && (
                        <button
                        onClick={() => onDownload(it)}
                        className="inline-flex items-center gap-1 rounded-md border px-2 py-1 text-xs hover:bg-muted"
                        title="Download"
                        >
                        <Download className="h-3.5 w-3.5" />
                        Download
                        </button>
                    )}
                    </div>
                    </div>
                ))
            )}
            </div>
            </div>
            </div>
            </div>

            {/* PREVIEW */}
            <div className="rounded-md border p-3">
            <div className="mb-2 text-sm font-medium">Preview</div>
            {previewHref ? (
                <div className="border rounded overflow-hidden">
                <iframe
                key={previewHref}
                src={previewHref}
                className="w-full h-[420px]"
                title="Preview"
                />
                </div>
            ) : (
                <div className="text-sm text-muted-foreground">
                Select a file to preview.
                </div>
            )}
            </div>
            </div>
            </div>
    );
}