'use client';

import React, { createContext, useCallback, useContext, useEffect, useMemo, useState } from 'react';
import { ResponsiveGridLayout, useContainerWidth, verticalCompactor, type ResponsiveLayouts, type Layout } from 'react-grid-layout';
import { RotateCcw } from 'lucide-react';

const STORAGE_KEY = 'dashboard-layouts';

const BREAKPOINTS = { lg: 1024, md: 768, sm: 0 };
const COLS = { lg: 6, md: 4, sm: 1 };
const ROW_HEIGHT = 200;
const MARGIN: [number, number] = [16, 16];

const DEFAULT_LAYOUTS: ResponsiveLayouts = {
    lg: [
        { i: 'uptime',   x: 0, y: 0, w: 2, h: 1, minW: 2, minH: 1 },
        { i: 'weather',  x: 2, y: 0, w: 2, h: 1, minW: 2, minH: 1 },
        { i: 'globe',    x: 4, y: 0, w: 2, h: 2, minW: 2, minH: 2 },
        { i: 'newsfeed', x: 0, y: 1, w: 4, h: 3, minW: 2, minH: 2 },
    ],
    md: [
        { i: 'uptime',   x: 0, y: 0, w: 2, h: 1, minW: 2, minH: 1 },
        { i: 'weather',  x: 2, y: 0, w: 2, h: 1, minW: 2, minH: 1 },
        { i: 'globe',    x: 0, y: 1, w: 2, h: 2, minW: 2, minH: 2 },
        { i: 'newsfeed', x: 2, y: 1, w: 2, h: 3, minW: 2, minH: 2 },
    ],
    sm: [
        { i: 'uptime',   x: 0, y: 0, w: 1, h: 1, minW: 1, minH: 1 },
        { i: 'weather',  x: 0, y: 1, w: 1, h: 1, minW: 1, minH: 1 },
        { i: 'globe',    x: 0, y: 2, w: 1, h: 2, minW: 1, minH: 2 },
        { i: 'newsfeed', x: 0, y: 4, w: 1, h: 3, minW: 1, minH: 2 },
    ],
};

const DRAG_CONFIG = { handle: '.widget-drag-handle' };

// --- Layout Context ---

interface LayoutContextValue {
    updateWidgetSize: (key: string, w: number, h: number) => void;
}

const LayoutContext = createContext<LayoutContextValue>({
    updateWidgetSize: () => {},
});

export function useLayoutContext() {
    return useContext(LayoutContext);
}

// --- GridShell ---

interface GridShellProps {
    children: React.ReactNode;
}

function loadSavedLayouts(): ResponsiveLayouts | null {
    if (typeof window === 'undefined') return null;
    try {
        const raw = localStorage.getItem(STORAGE_KEY);
        if (raw) return JSON.parse(raw);
    } catch {}
    return null;
}

function persistLayouts(layouts: ResponsiveLayouts) {
    try {
        localStorage.setItem(STORAGE_KEY, JSON.stringify(layouts));
    } catch {}
}

export function GridShell({ children }: GridShellProps) {
    const [layouts, setLayouts] = useState<ResponsiveLayouts>(DEFAULT_LAYOUTS);
    const [ready, setReady] = useState(false);
    const { width, containerRef, mounted } = useContainerWidth({ initialWidth: 1280 });

    useEffect(() => {
        const saved = loadSavedLayouts();
        if (saved) setLayouts(saved);
        setReady(true);
    }, []);

    const handleLayoutChange = useCallback((_layout: Layout, allLayouts: ResponsiveLayouts) => {
        setLayouts(allLayouts);
        persistLayouts(allLayouts);
    }, []);

    const handleReset = useCallback(() => {
        setLayouts(DEFAULT_LAYOUTS);
        persistLayouts(DEFAULT_LAYOUTS);
    }, []);

    const updateWidgetSize = useCallback((key: string, w: number, h: number) => {
        setLayouts((prev) => {
            const next: ResponsiveLayouts = {};
            for (const bp of Object.keys(prev)) {
                const bpLayout = prev[bp];
                if (!bpLayout) continue;
                next[bp] = bpLayout.map((item) =>
                    item.i === key ? { ...item, w, h } : item
                );
            }
            persistLayouts(next);
            return next;
        });
    }, []);

    const contextValue = useMemo(
        () => ({ updateWidgetSize }),
        [updateWidgetSize]
    );

    const childArray = React.Children.toArray(children);

    return (
        <LayoutContext.Provider value={contextValue}>
            <div className="min-h-screen bg-neutral-950 text-neutral-200 p-4 md:p-8">
                <div className="max-w-7xl mx-auto">
                    <header className="mb-8 flex items-center justify-between">
                        <div>
                            <h1 className="text-3xl font-bold tracking-tight text-white mb-1">Mission Control</h1>
                        </div>
                        <div className="flex items-center gap-4">
                            <button
                                onClick={handleReset}
                                className="flex items-center gap-1.5 text-xs text-neutral-500 hover:text-neutral-300 transition-colors px-2 py-1 rounded-lg hover:bg-neutral-800"
                                title="Reset layout"
                            >
                                <RotateCcw size={13} />
                                Reset layout
                            </button>
                            <div className="flex gap-2 items-center">
                                <div className="w-2 h-2 rounded-full bg-emerald-500 animate-pulse" />
                                <span className="text-xs font-mono text-emerald-500">SYSTEM ONLINE</span>
                            </div>
                        </div>
                    </header>

                    <div ref={containerRef as React.RefObject<HTMLDivElement>}>
                        {mounted && ready && (
                            <ResponsiveGridLayout
                                width={width}
                                layouts={layouts}
                                breakpoints={BREAKPOINTS}
                                cols={COLS}
                                rowHeight={ROW_HEIGHT}
                                margin={MARGIN}
                                onLayoutChange={handleLayoutChange}
                                dragConfig={DRAG_CONFIG}
                                compactor={verticalCompactor}
                            >
                                {childArray.map((child) => {
                                    if (!React.isValidElement(child)) return null;
                                    const key = child.key as string;
                                    return (
                                        <div key={key} className="h-full">
                                            {child}
                                        </div>
                                    );
                                })}
                            </ResponsiveGridLayout>
                        )}
                    </div>
                </div>
            </div>
        </LayoutContext.Provider>
    );
}