export class LayeredCanvas {
    constructor(c) {
        console.log("initializeLayeredCanvas");
        this.canvas = c;
        this.context = canvas.getContext('2d');

        this.canvas.addEventListener('mousedown', this.handleMouseDown.bind(this));
        this.canvas.addEventListener('mousemove', this.handleMouseMove.bind(this));
        this.canvas.addEventListener('mouseup', this.handleMouseUp.bind(this));
        this.canvas.addEventListener('mouseleave', this.handleMouseLeave.bind(this));

        this.layers = [];
    }

    cleanup() {
        this.canvas.removeEventListener('mousedown', this.handleMouseDown.bind(this));
        this.canvas.removeEventListener('mousemove', this.handleMouseMove.bind(this));
        this.canvas.removeEventListener('mouseup', this.handleMouseUp.bind(this));
        this.canvas.removeEventListener('mouseleave', this.handleMouseLeave.bind(this));
    }

    getCanvasSize() {
        return [this.canvas.width, this.canvas.height];
    }
    
    getCanvasPosition(event) {
        const rect = this.canvas.getBoundingClientRect();
        const x = Math.floor(event.clientX - rect.left);
        const y = Math.floor(event.clientY - rect.top);
        return [x, y];
    }
    
    handleMouseDown(event) {
        const p = this.getCanvasPosition(event);
      
        for (let i = this.layers.length - 1; i >= 0; i--) {
            const layer = this.layers[i];
            if (layer.accepts(p)) {
                layer.mouseDown(p);
                this.draggingLayer = layer;
                this.dragStart = p;
                break;
            }
        }
    }
      
    handleMouseMove(event) {
        this.mouseCursor = this.getCanvasPosition(event);
        if (this.draggingLayer) {
            this.draggingLayer.mouseMove(this.getCanvasPosition(event)); // 念のため別の実体
        }
        this.render();
    }
    
    handleMouseUp(event) {
        if (this.draggingLayer) {
            this.draggingLayer.mouseUp(this.getCanvasPosition(event));
            this.draggingLayer = null;
        }
    }
      
    handleMouseLeave(event) {
        this.mouseCursor = [-1,-1];
        if (this.draggingLayer) {
            this.handleMouseUp(event);
        }
    }
      
    render() {
        for (let i = 0; i < this.layers.length; i++) {
            const layer = this.layers[i];
            layer.render(this.canvas, this.context);
        }
    }
    
    redraw() {
        this.render();
    }
    
    addLayer(layer) {
        this.layers.push(layer);
    }
    
}


let mouseSequence = { // mixin
    mouseDown(p) {
        this.mouseHandler = this.mouse(p);
    },
    mouseMove(p) {
        if (this.mouseHandler) {
            this.mouseHandler.next(p);
        }
    },
    mouseUp(p) {
        if (this.mouseHandler) {
            this.mouseHandler.next(null);
            this.mouseHandler = null;
        }
    },
/*
    sample mouse handler
    *mouse(p) {
        while (p = yield) {
            console.log("mouse", p);
        }
    }
*/
};

export function sequentializeMouse(layerClass) {
    layerClass.mouseDown = mouseSequence.mouseDown;
    layerClass.mouseMove = mouseSequence.mouseMove;
    layerClass.mouseUp = mouseSequence.mouseUp;
}

export class Layer {
    constructor() {}

    reserveRender() { renderReserved = true; }

    accepts(point) { return false; }
    mouseDown(point) {}
    mouseMove(point) {}
    mouseUp(point) {}
    render(canvas, ctx) {}
}