'use client';

import { useRef, useEffect, useCallback, useState, forwardRef, useImperativeHandle } from 'react';
import { Button } from '@/components/ui/button';
import { Undo2, Trash2, Minus, Plus, X } from 'lucide-react';

export interface AnnotationStroke {
    points: { x: number; y: number }[];
    color: string;
    width: number;
}

export interface AnnotationCanvasHandle {
    getStrokes: () => AnnotationStroke[];
}

interface AnnotationCanvasProps {
    mode: 'draw' | 'view';
    strokes?: AnnotationStroke[];
    onConfirm?: (strokes: AnnotationStroke[]) => void;
    onCancel?: () => void;
    onDismiss?: () => void; // For view mode, close overlay
}

const COLORS = ['#FF3B30', '#FF9500', '#FFCC00', '#34C759', '#007AFF', '#AF52DE', '#FFFFFF'];
const DEFAULT_COLOR = '#FF3B30';
const DEFAULT_WIDTH = 3;
const MIN_WIDTH = 1;
const MAX_WIDTH = 10;

// Reference canvas width for stroke scaling
const REF_WIDTH = 1000;

export const AnnotationCanvas = forwardRef<AnnotationCanvasHandle, AnnotationCanvasProps>(function AnnotationCanvas({ mode, strokes: initialStrokes, onConfirm, onCancel, onDismiss }, ref) {
    const canvasRef = useRef<HTMLCanvasElement>(null);
    const containerRef = useRef<HTMLDivElement>(null);
    const [strokes, setStrokes] = useState<AnnotationStroke[]>(initialStrokes || []);
    const [currentStroke, setCurrentStroke] = useState<AnnotationStroke | null>(null);
    const [color, setColor] = useState(DEFAULT_COLOR);
    const [width, setWidth] = useState(DEFAULT_WIDTH);
    const isDrawingRef = useRef(false);
    void onConfirm;

    // Expose getStrokes so parent can grab current drawing without confirm
    useImperativeHandle(ref, () => ({
        getStrokes: () => strokes,
    }), [strokes]);

    // Render all strokes
    const renderStrokes = useCallback((ctx: CanvasRenderingContext2D, canvas: HTMLCanvasElement, strokeList: AnnotationStroke[], active?: AnnotationStroke | null) => {
        ctx.clearRect(0, 0, canvas.width, canvas.height);

        const scale = canvas.width / REF_WIDTH;

        const draw = (s: AnnotationStroke) => {
            if (s.points.length < 2) return;
            ctx.strokeStyle = s.color;
            ctx.lineWidth = s.width * scale;
            ctx.lineCap = 'round';
            ctx.lineJoin = 'round';
            ctx.beginPath();
            ctx.moveTo(s.points[0].x * canvas.width, s.points[0].y * canvas.height);
            for (let i = 1; i < s.points.length; i++) {
                ctx.lineTo(s.points[i].x * canvas.width, s.points[i].y * canvas.height);
            }
            ctx.stroke();
        };

        strokeList.forEach(draw);
        if (active) draw(active);
    }, []);

    // Keep a stable ref to the latest strokes/currentStroke so the resize
    // handler can redraw without being listed as a dependency (which would
    // re-register the listener on every stroke change).
    const strokesRef = useRef(strokes);
    const currentStrokeRef = useRef(currentStroke);
    useEffect(() => { strokesRef.current = strokes; }, [strokes]);
    useEffect(() => { currentStrokeRef.current = currentStroke; }, [currentStroke]);

    // Resize canvas to match container — listener registered once, never re-added.
    useEffect(() => {
        const resizeCanvas = () => {
            const canvas = canvasRef.current;
            const container = containerRef.current;
            if (!canvas || !container) return;

            const rect = container.getBoundingClientRect();
            canvas.width = rect.width;
            canvas.height = rect.height;

            const ctx = canvas.getContext('2d');
            if (ctx) renderStrokes(ctx, canvas, strokesRef.current, currentStrokeRef.current);
        };

        resizeCanvas();
        window.addEventListener('resize', resizeCanvas);
        return () => window.removeEventListener('resize', resizeCanvas);
    }, [renderStrokes]); // renderStrokes is stable (useCallback with no deps that change)

    // Re-render on stroke changes
    useEffect(() => {
        const canvas = canvasRef.current;
        if (!canvas) return;
        const ctx = canvas.getContext('2d');
        if (!ctx) return;
        renderStrokes(ctx, canvas, strokes, currentStroke);
    }, [strokes, currentStroke, renderStrokes]);

    const getPoint = useCallback((e: React.MouseEvent | React.TouchEvent) => {
        const canvas = canvasRef.current;
        if (!canvas) return null;
        const rect = canvas.getBoundingClientRect();
        let clientX: number, clientY: number;
        if ('touches' in e) {
            clientX = e.touches[0].clientX;
            clientY = e.touches[0].clientY;
        } else {
            clientX = e.clientX;
            clientY = e.clientY;
        }
        return {
            x: (clientX - rect.left) / rect.width,
            y: (clientY - rect.top) / rect.height,
        };
    }, []);

    const handlePointerDown = useCallback((e: React.MouseEvent | React.TouchEvent) => {
        if (mode !== 'draw') return;
        e.preventDefault();
        e.stopPropagation();
        const pt = getPoint(e);
        if (!pt) return;
        isDrawingRef.current = true;
        setCurrentStroke({ points: [pt], color, width });
    }, [mode, color, width, getPoint]);

    const handlePointerMove = useCallback((e: React.MouseEvent | React.TouchEvent) => {
        if (mode !== 'draw' || !isDrawingRef.current) return;
        e.preventDefault();
        e.stopPropagation();
        const pt = getPoint(e);
        if (!pt) return;
        setCurrentStroke(prev => {
            if (!prev) return prev;
            return { ...prev, points: [...prev.points, pt] };
        });
    }, [mode, getPoint]);

    const handlePointerUp = useCallback((e: React.MouseEvent | React.TouchEvent) => {
        if (mode !== 'draw' || !isDrawingRef.current) return;
        e.preventDefault();
        e.stopPropagation();
        isDrawingRef.current = false;
        setCurrentStroke(prev => {
            if (prev && prev.points.length >= 2) {
                setStrokes(s => [...s, prev]);
            }
            return null;
        });
    }, [mode]);

    const handleUndo = useCallback(() => {
        setStrokes(prev => prev.slice(0, -1));
    }, []);

    const handleClear = useCallback(() => {
        setStrokes([]);
    }, []);

    // View mode: click to dismiss
    const handleViewClick = useCallback((e: React.MouseEvent) => {
        if (mode === 'view') {
            e.stopPropagation();
            onDismiss?.();
        }
    }, [mode, onDismiss]);

    if (mode === 'view') {
        return (
            <div
                ref={containerRef}
                className="absolute inset-0 z-[60] cursor-pointer"
                onClick={handleViewClick}
                title="Click to dismiss annotation"
            >
                <canvas
                    ref={canvasRef}
                    className="w-full h-full pointer-events-none"
                />
            </div>
        );
    }

    return (
        <div
            ref={containerRef}
            className="absolute inset-0 z-[60]"
            onClick={(e) => e.stopPropagation()}
        >
            <canvas
                ref={canvasRef}
                className="w-full h-full cursor-crosshair"
                onMouseDown={handlePointerDown}
                onMouseMove={handlePointerMove}
                onMouseUp={handlePointerUp}
                onMouseLeave={handlePointerUp}
                onTouchStart={handlePointerDown}
                onTouchMove={handlePointerMove}
                onTouchEnd={handlePointerUp}
            />

            {/* Toolbar */}
            <div className="absolute top-3 left-1/2 -translate-x-1/2 flex items-center justify-center flex-wrap gap-x-2 gap-y-2 w-[calc(100%-24px)] max-w-fit bg-background/90 backdrop-blur-sm rounded-lg px-3 py-2 shadow-lg border z-[70]">
                {/* Colors */}
                <div className="flex items-center justify-center flex-wrap gap-1.5">
                    {COLORS.map(c => (
                        <button
                            key={c}
                            className="w-6 h-6 rounded-full border-2 transition-transform hover:scale-110 shrink-0"
                            style={{
                                backgroundColor: c,
                                borderColor: color === c ? 'white' : 'transparent',
                                boxShadow: color === c ? `0 0 0 2px ${c}` : 'none',
                            }}
                            onClick={() => setColor(c)}
                        />
                    ))}
                </div>

                <div className="hidden sm:block w-px h-6 bg-border mx-1" />

                {/* Brush size */}
                <div className="flex items-center gap-1">
                    <Button variant="ghost" size="icon" className="h-7 w-7" onClick={() => setWidth(w => Math.max(MIN_WIDTH, w - 1))}>
                        <Minus className="h-3 w-3" />
                    </Button>
                    <span className="text-xs tabular-nums w-4 text-center">{width}</span>
                    <Button variant="ghost" size="icon" className="h-7 w-7" onClick={() => setWidth(w => Math.min(MAX_WIDTH, w + 1))}>
                        <Plus className="h-3 w-3" />
                    </Button>
                </div>

                <div className="hidden sm:block w-px h-6 bg-border mx-1" />

                {/* Actions */}
                <div className="flex items-center gap-1">
                    <Button variant="ghost" size="icon" className="h-7 w-7" onClick={handleUndo} disabled={strokes.length === 0} title="Undo">
                        <Undo2 className="h-4 w-4" />
                    </Button>
                    <Button variant="ghost" size="icon" className="h-7 w-7 text-destructive hover:bg-destructive/10" onClick={handleClear} disabled={strokes.length === 0} title="Clear all">
                        <Trash2 className="h-4 w-4" />
                    </Button>
                </div>

                <div className="hidden sm:block w-px h-6 bg-border mx-1" />

                {/* Close */}
                <Button variant="ghost" size="icon" className="h-7 w-7" onClick={onCancel} title="Close annotation tool">
                    <X className="h-4 w-4" />
                </Button>
            </div>
        </div>
    );
});