Application-Web/front/components/arrows/BendableArrow.tsx

import {CSSProperties, ReactElement, useCallback, useEffect, useRef, useState,} from "react"
import {angle, middlePos, Pos, relativeTo} from "./Pos"

import "../../style/bendable_arrows.css"
import Draggable from "react-draggable"

export interface BendableArrowProps {
    startPos: Pos
    segments: Segment[]
    onSegmentsChanges: (edges: Segment[]) => void

    startRadius?: number
    endRadius?: number

    style?: ArrowStyle
}

export interface ArrowStyle {
    width?: number
    head?: () => ReactElement
    tail?: () => ReactElement
}

const ArrowStyleDefaults = {
    width: 4,
}

export interface Segment {
    next: Pos
    controlPoint?: Pos
}

function constraintInCircle(pos: Pos, from: Pos, radius: number): Pos {
    const theta = angle(pos, from)

    return {
        x: pos.x - Math.sin(theta) * radius,
        y: pos.y - Math.cos(theta) * radius,
    }
}


function Triangle({fill}: {fill: string}) {
    return (
        <svg viewBox={"0 0 50 50"} width={20} height={20}>
            <polygon points={"50 0, 0 0, 25 40"} fill={fill}/>
        </svg>
    )
}

export default function BendableArrow({
                                          startPos,

                                          segments,
                                          onSegmentsChanges,

                                          style,
                                          startRadius = 0,
                                          endRadius = 0,
                                      }: BendableArrowProps) {


    const containerRef = useRef<HTMLDivElement>(null)
    const svgRef = useRef<SVGSVGElement>(null)

    const pathRef = useRef<SVGPathElement>(null)

    const styleWidth = style?.width ?? ArrowStyleDefaults.width

    const [controlPointsDots, setControlPointsDots] = useState<ReactElement[]>(
        [],
    )

    useEffect(() => {
        setInternalSegments(segments)
    }, [segments]);

    const [internalSegments, setInternalSegments] = useState(segments)

    const [isSelected, setIsSelected] = useState(false)


    const headRef = useRef<HTMLDivElement>(null)
    const tailRef = useRef<HTMLDivElement>(null)

    useEffect(() => {

        const basePos = containerRef.current!.parentElement!.getBoundingClientRect()

        setControlPointsDots(computeControlPoints(basePos))

        const selectionHandler = (e: MouseEvent) => {
            if (!(e.target instanceof Node))
                return

            setIsSelected(containerRef.current!.contains(e.target))
        }

        document.addEventListener('mousedown', selectionHandler)
        return () => document.removeEventListener('mousedown', selectionHandler)

    }, []);


    function computeControlPoints(basePos: Pos) {
        return internalSegments.map(({next, controlPoint}, i) => {
            const prev = i == 0 ? startPos : internalSegments[i - 1].next

            const prevRelative = relativeTo(prev, basePos)
            const nextRelative = relativeTo(next, basePos)


            const cpPos = controlPoint ? relativeTo(controlPoint, basePos) : {
                x: prevRelative.x / 2 + nextRelative.x / 2,
                y: prevRelative.y / 2 + nextRelative.y / 2,
            }

            return (
                <ControlPoint
                    key={i}
                    pos={cpPos}
                    basePos={basePos}
                    onPosValidated={(controlPoint) => {
                        const segment = internalSegments[i]
                        const segments = internalSegments.toSpliced(i, 1, {...segment, controlPoint})
                        onSegmentsChanges(segments)
                    }}
                    onMoves={(controlPoint) => {
                        setInternalSegments(is => {
                            return is.toSpliced(i, 1, {...is[i], controlPoint})
                        })
                    }}
                />
            )
        })
    }


    const update = useCallback(() => {

        // only one segment is supported for now, which is the first.
        // any other segments will be ignored
        const segment = internalSegments[0] ?? null

        if (segment == null) throw new Error("segments might not be empty.")

        const endPos = segment.next

        const basePos = containerRef.current!.parentElement!.getBoundingClientRect()

        const startRelative = relativeTo(startPos, basePos)
        const endRelative = relativeTo(endPos!, basePos)

        const controlPoint = segment.controlPoint ? relativeTo(segment.controlPoint, basePos) : {
            x: startRelative.x / 2 + endRelative.x / 2,
            y: startRelative.y / 2 + endRelative.y / 2,
        }


        const tailPos = constraintInCircle(
            startRelative,
            controlPoint,
            startRadius!,
        )
        const headPos = constraintInCircle(
            endRelative,
            controlPoint,
            endRadius!,
        )

        const left = Math.min(tailPos.x, headPos.x)
        const top = Math.min(tailPos.y, headPos.y)


        Object.assign(tailRef.current!.style, {
            left: tailPos.x + "px",
            top: tailPos.y + "px",
            transformOrigin: "top center",
            transform: `translateX(-50%) rotate(${-angle(tailPos, controlPoint) * (180 / Math.PI)}deg)`
        } as CSSProperties)


        Object.assign(headRef.current!.style, {
            left: headPos.x + "px",
            top: headPos.y + "px",
            transformOrigin: "top center",
            transform: `translateX(-50%) rotate(${-angle(headPos, controlPoint) * (180 / Math.PI)}deg)`
        } as CSSProperties)


        const svgStyle: CSSProperties = {
            left: left + "px",
            top: top + "px",
        }

        const segmentsRelatives = internalSegments.map(({next, controlPoint}) => {
            return {
                next: relativeTo(next, basePos),
                cp: controlPoint ? relativeTo(controlPoint, basePos) : undefined
            }
        })

        const computedSegments = segmentsRelatives
            .map(({next: n, cp}, idx) => {
                let next = n

                if (idx == internalSegments.length - 1) {
                    //if it is the last element
                    next = constraintInCircle(
                        next,
                        controlPoint,
                        endRadius!,
                    )
                }

                if (cp == undefined) {
                    return `L${next.x - left} ${next.y - top}`
                }

                return `C${cp.x - left} ${cp.y - top}, ${cp.x - left} ${cp.y - top}, ${next.x - left} ${next.y - top}`
            })
            .join(" ")

        const d = `M${tailPos.x - left} ${tailPos.y - top} ` + computedSegments
        pathRef.current!.setAttribute("d", d)
        Object.assign(svgRef.current!.style, svgStyle)

        if (isSelected) {
            setControlPointsDots(computeControlPoints(basePos))
        }
    }, [startPos, internalSegments])


    useEffect(update, [update])

    return (
        <div ref={containerRef} style={{position: "absolute", top: 0, left: 0}}>
            <svg
                ref={svgRef}
                style={{
                    overflow: "visible",
                    position: "absolute",
                    pointerEvents: "none",
                }}>
                <path
                    className="arrow-path"
                    ref={pathRef}
                    stroke={"#000"}
                    strokeWidth={styleWidth}
                    fill="none"
                />
            </svg>

            <div className={"arrow-head"}
                 style={{position: "absolute", transformOrigin: "center"}}
                 ref={headRef}
            >
                {style?.head?.call(style) ?? <Triangle fill={"red"}/>}
            </div>

            <div className={"arrow-tail"}
                 style={{position: "absolute", transformOrigin: "center"}}
                 ref={tailRef}
            >
                {style?.tail?.call(style) ?? <Triangle fill={"blue"}/>}
            </div>

            {isSelected && controlPointsDots}
        </div>
    )
}

interface ControlPointProps {
    pos: Pos
    basePos: Pos,
    onMoves: (currentPos: Pos) => void
    onPosValidated: (newPos: Pos) => void,
    radius?: number
}

function ControlPoint({
                          pos,
                          onMoves,
                          onPosValidated,
                          radius = 7,
                      }: ControlPointProps) {
    const ref = useRef<HTMLDivElement>(null)

    return (
        <Draggable
            nodeRef={ref}
            onStop={() => {
                const pointPos = middlePos(ref.current!.getBoundingClientRect())
                onPosValidated(pointPos)
            }}
            onDrag={() => {
                const pointPos = middlePos(ref.current!.getBoundingClientRect())
                onMoves(pointPos)
            }}
            position={{x: pos.x - radius, y: pos.y - radius}}
        >
            <div
                ref={ref}
                className={"arrow-edge-control-point"}
                style={{
                    position: "absolute",
                    width: radius * 2,
                    height: radius * 2,
                }}
            />
        </Draggable>
    )
}