import { MeshGeometry } from '@pixi/mesh';
import type { IPoint } from '@pixi/math';

/**
 * RopeGeometry allows you to draw a geometry across several points and then manipulate these points.
 *
 * ```js
 * for (let i = 0; i < 20; i++) {
 *     points.push(new PIXI.Point(i * 50, 0));
 * };
 * const rope = new PIXI.RopeGeometry(100, points);
 * ```
 * @memberof PIXI
 */
export class RopeGeometry extends MeshGeometry
{
    /** An array of points that determine the rope. */
    public points: IPoint[];

    /** Rope texture scale, if zero then the rope texture is stretched. */
    public readonly textureScale: number;

    /**
     * The width (i.e., thickness) of the rope.
     * @readonly
     */
    _width: number;

    /**
     * @param width - The width (i.e., thickness) of the rope.
     * @param points - An array of {@link PIXI.Point} objects to construct this rope.
     * @param textureScale - By default the rope texture will be stretched to match
     *     rope length. If textureScale is positive this value will be treated as a scaling
     *     factor and the texture will preserve its aspect ratio instead. To create a tiling rope
     *     set baseTexture.wrapMode to {@link PIXI.WRAP_MODES.REPEAT} and use a power of two texture,
     *     then set textureScale=1 to keep the original texture pixel size.
     *     In order to reduce alpha channel artifacts provide a larger texture and downsample -
     *     i.e. set textureScale=0.5 to scale it down twice.
     */
    constructor(width = 200, points: IPoint[], textureScale = 0)
    {
        super(new Float32Array(points.length * 4),
            new Float32Array(points.length * 4),
            new Uint16Array((points.length - 1) * 6));

        this.points = points;
        this._width = width;
        this.textureScale = textureScale;

        this.build();
    }

    /**
     * The width (i.e., thickness) of the rope.
     * @readonly
     */
    get width(): number
    {
        return this._width;
    }

    /** Refreshes Rope indices and uvs */
    private build(): void
    {
        const points = this.points;

        if (!points) return;

        const vertexBuffer = this.getBuffer('aVertexPosition');
        const uvBuffer = this.getBuffer('aTextureCoord');
        const indexBuffer = this.getIndex();

        // if too little points, or texture hasn't got UVs set yet just move on.
        if (points.length < 1)
        {
            return;
        }

        // if the number of points has changed we will need to recreate the arraybuffers
        if (vertexBuffer.data.length / 4 !== points.length)
        {
            vertexBuffer.data = new Float32Array(points.length * 4);
            uvBuffer.data = new Float32Array(points.length * 4);
            indexBuffer.data = new Uint16Array((points.length - 1) * 6);
        }

        const uvs = uvBuffer.data;
        const indices = indexBuffer.data;

        uvs[0] = 0;
        uvs[1] = 0;
        uvs[2] = 0;
        uvs[3] = 1;

        let amount = 0;
        let prev = points[0];
        const textureWidth = this._width * this.textureScale;
        const total = points.length; // - 1;

        for (let i = 0; i < total; i++)
        {
            // time to do some smart drawing!
            const index = i * 4;

            if (this.textureScale > 0)
            {
                // calculate pixel distance from previous point
                const dx = prev.x - points[i].x;
                const dy = prev.y - points[i].y;
                const distance = Math.sqrt((dx * dx) + (dy * dy));

                prev = points[i];
                amount += distance / textureWidth;
            }
            else
            {
                // stretch texture
                amount = i / (total - 1);
            }

            uvs[index] = amount;
            uvs[index + 1] = 0;

            uvs[index + 2] = amount;
            uvs[index + 3] = 1;
        }

        let indexCount = 0;

        for (let i = 0; i < total - 1; i++)
        {
            const index = i * 2;

            indices[indexCount++] = index;
            indices[indexCount++] = index + 1;
            indices[indexCount++] = index + 2;

            indices[indexCount++] = index + 2;
            indices[indexCount++] = index + 1;
            indices[indexCount++] = index + 3;
        }

        // ensure that the changes are uploaded
        uvBuffer.update();
        indexBuffer.update();

        this.updateVertices();
    }

    /** refreshes vertices of Rope mesh */
    public updateVertices(): void
    {
        const points = this.points;

        if (points.length < 1)
        {
            return;
        }

        let lastPoint = points[0];
        let nextPoint;
        let perpX = 0;
        let perpY = 0;

        const vertices = this.buffers[0].data;
        const total = points.length;

        for (let i = 0; i < total; i++)
        {
            const point = points[i];
            const index = i * 4;

            if (i < points.length - 1)
            {
                nextPoint = points[i + 1];
            }
            else
            {
                nextPoint = point;
            }

            perpY = -(nextPoint.x - lastPoint.x);
            perpX = nextPoint.y - lastPoint.y;

            let ratio = (1 - (i / (total - 1))) * 10;

            if (ratio > 1)
            {
                ratio = 1;
            }

            const perpLength = Math.sqrt((perpX * perpX) + (perpY * perpY));
            const num = this.textureScale > 0 ? this.textureScale * this._width / 2 : this._width / 2;

            perpX /= perpLength;
            perpY /= perpLength;

            perpX *= num;
            perpY *= num;

            vertices[index] = point.x + perpX;
            vertices[index + 1] = point.y + perpY;
            vertices[index + 2] = point.x - perpX;
            vertices[index + 3] = point.y - perpY;

            lastPoint = point;
        }

        this.buffers[0].update();
    }

    public update(): void
    {
        if (this.textureScale > 0)
        {
            this.build(); // we need to update UVs
        }
        else
        {
            this.updateVertices();
        }
    }
}
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