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

import {
    CSSProperties,
    ReactElement,
    RefObject,
    useCallback,
    useEffect,
    useRef,
    useState,
} from "react"
import {
    add,
    angle,
    between,
    distance,
    middlePos,
    minus,
    mul,
    Pos,
    posWithinBase,
    ratioWithinBase,
} from "./Pos"

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

export interface BendableArrowProps {
    area: RefObject<HTMLElement>
    startPos: Pos
    segments: Segment[]
    onSegmentsChanges: (edges: Segment[]) => void
    forceStraight: boolean

    startRadius?: number
    endRadius?: number

    onDeleteRequested?: () => void

    style?: ArrowStyle
}

export interface ArrowStyle {
    width?: number
    dashArray?: string
    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,
    }
}

export default function BendableArrow({
    area,
    startPos,

    segments,
    onSegmentsChanges,
    forceStraight,

    style,
    startRadius = 0,
    endRadius = 0,
    onDeleteRequested,
}: BendableArrowProps) {
    const containerRef = useRef<HTMLDivElement>(null)
    const svgRef = useRef<SVGSVGElement>(null)
    const pathRef = useRef<SVGPathElement>(null)

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

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

    const [internalSegments, setInternalSegments] = useState(segments)

    const [isSelected, setIsSelected] = useState(false)

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

    function computeControlPoints(parentBase: DOMRect) {
        return segments.flatMap(({ next, controlPoint }, i) => {
            const prev = i == 0 ? startPos : segments[i - 1].next

            const prevRelative = posWithinBase(prev, parentBase)
            const nextRelative = posWithinBase(next, parentBase)

            const cpPos =
                controlPoint ||
                ratioWithinBase(
                    add(between(prevRelative, nextRelative), parentBase),
                    parentBase,
                )

            const setControlPointPos = (newPos: Pos | undefined) => {
                const segment = segments[i]
                const newSegments = segments.toSpliced(i, 1, {
                    ...segment,
                    controlPoint: newPos,
                })
                onSegmentsChanges(newSegments)
            }

            return [
                // curve control point
                <ArrowPoint
                    key={i}
                    className={"arrow-point-control"}
                    posRatio={cpPos}
                    parentBase={parentBase}
                    onPosValidated={setControlPointPos}
                    onRemove={() => setControlPointPos(undefined)}
                    onMoves={(controlPoint) => {
                        setInternalSegments((is) => {
                            return is.toSpliced(i, 1, {
                                ...is[i],
                                controlPoint,
                            })
                        })
                    }}
                />,
                //next pos point (only if this is not the last segment)
                i != segments.length - 1 && (
                    <ArrowPoint
                        className={"arrow-point-next"}
                        posRatio={next}
                        parentBase={parentBase}
                        onPosValidated={(next) => {
                            const currentSegment = segments[i]
                            const newSegments = segments.toSpliced(i, 1, {
                                ...currentSegment,
                                next,
                            })
                            onSegmentsChanges(newSegments)
                        }}
                        onRemove={() => {
                            onSegmentsChanges(
                                segments.toSpliced(Math.max(i - 1, 0), 1),
                            )
                        }}
                        onMoves={(next) => {
                            setInternalSegments((is) => {
                                return is.toSpliced(i, 1, {
                                    ...is[i],
                                    next,
                                })
                            })
                        }}
                    />
                ),
            ]
        })
    }

    const update = useCallback(() => {
        const parentBase = area.current!.getBoundingClientRect()

        const firstSegment = internalSegments[0] ?? null
        if (firstSegment == null)
            throw new Error("segments might not be empty.")

        const lastSegment = internalSegments[internalSegments.length - 1]

        const startRelative = posWithinBase(startPos, parentBase)
        const endRelative = posWithinBase(lastSegment.next, parentBase)

        const startNext =
            firstSegment.controlPoint && !forceStraight
                ? posWithinBase(firstSegment.controlPoint, parentBase)
                : posWithinBase(firstSegment.next, parentBase)

        const endPrevious = forceStraight
            ? startRelative
            : lastSegment.controlPoint
              ? posWithinBase(lastSegment.controlPoint, parentBase)
              : internalSegments[internalSegments.length - 2]
                ? posWithinBase(
                      internalSegments[internalSegments.length - 2].next,
                      parentBase,
                  )
                : startRelative

        const tailPos = constraintInCircle(
            startRelative,
            startNext,
            startRadius!,
        )
        const headPos = constraintInCircle(endRelative, endPrevious, 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, startNext) * (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, endPrevious) * (180 / Math.PI)
            }deg)`,
        } as CSSProperties)

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

        const segmentsRelatives = (
            forceStraight ? internalSegments.slice(-1) : internalSegments
        ).map(({ next, controlPoint }, idx) => {
            const nextPos = posWithinBase(next, parentBase)
            return {
                next: nextPos,
                cp:
                    controlPoint && !forceStraight
                        ? posWithinBase(controlPoint, parentBase)
                        : between(
                              idx == 0
                                  ? startRelative
                                  : posWithinBase(
                                        internalSegments[idx - 1].next,
                                        parentBase,
                                    ),
                              nextPos,
                          ),
            }
        })

        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, cp, endRadius!)
                }

                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)
    }, [startPos, internalSegments, forceStraight])

    useEffect(update, [update])

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

            const isSelected = containerRef.current!.contains(e.target)
            setIsSelected(isSelected)
        }

        document.addEventListener("mousedown", selectionHandler)
        window.addEventListener("resize", update)

        return () => {
            document.removeEventListener("mousedown", selectionHandler)
            window.removeEventListener("resize", update)
        }
    }, [update, containerRef])

    useEffect(() => {
        if (forceStraight) return

        const addSegment = (e: MouseEvent) => {
            const parentBase = area.current!.getBoundingClientRect()

            const clickAbsolutePos: Pos = { x: e.x, y: e.y }
            const clickPosBaseRatio = ratioWithinBase(
                clickAbsolutePos,
                parentBase,
            )

            let segmentInsertionIndex = -1
            let segmentInsertionIsOnRightOfCP = false
            for (let i = 0; i < segments.length; i++) {
                const segment = segments[i]

                let currentPos = i == 0 ? startPos : segments[i - 1].next
                let nextPos = segment.next
                let controlPointPos = segment.controlPoint
                    ? segment.controlPoint
                    : between(currentPos, nextPos)

                const result = searchOnSegment(
                    currentPos,
                    controlPointPos,
                    nextPos,
                    clickPosBaseRatio,
                    0.05,
                )
                if (result == PointSegmentSearchResult.NOT_FOUND) continue

                segmentInsertionIndex = i
                segmentInsertionIsOnRightOfCP =
                    result == PointSegmentSearchResult.RIGHT_TO_CONTROL_POINT
                break
            }

            if (segmentInsertionIndex == -1) return

            const splicedSegment: Segment = segments[segmentInsertionIndex]

            onSegmentsChanges(
                segments.toSpliced(
                    segmentInsertionIndex,
                    1,
                    {
                        next: clickPosBaseRatio,
                        controlPoint: segmentInsertionIsOnRightOfCP
                            ? splicedSegment.controlPoint
                            : undefined,
                    },
                    {
                        next: splicedSegment.next,
                        controlPoint: segmentInsertionIsOnRightOfCP
                            ? undefined
                            : splicedSegment.controlPoint,
                    },
                ),
            )
        }

        pathRef?.current?.addEventListener("dblclick", addSegment)

        return () => {
            pathRef?.current?.removeEventListener("dblclick", addSegment)
        }
    }, [pathRef, segments, onSegmentsChanges])

    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}
                    strokeDasharray={style?.dashArray}
                    fill="none"
                    tabIndex={0}
                    onKeyUp={(e) => {
                        if (onDeleteRequested && e.key == "Delete")
                            onDeleteRequested()
                    }}
                />
            </svg>

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

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

            {!forceStraight &&
                isSelected &&
                computeControlPoints(area.current!.getBoundingClientRect())}
        </div>
    )
}

interface ControlPointProps {
    className: string
    posRatio: Pos
    parentBase: DOMRect
    onMoves: (currentPos: Pos) => void
    onPosValidated: (newPos: Pos) => void
    onRemove: () => void
    radius?: number
}

enum PointSegmentSearchResult {
    LEFT_TO_CONTROL_POINT,
    RIGHT_TO_CONTROL_POINT,
    NOT_FOUND,
}

function searchOnSegment(
    startPos: Pos,
    controlPoint: Pos,
    endPos: Pos,
    point: Pos,
    minDistance: number,
): PointSegmentSearchResult {
    const step =
        1 /
        ((distance(startPos, controlPoint) + distance(controlPoint, endPos)) /
            minDistance)

    const p0MinusP1 = minus(startPos, controlPoint)
    const p2MinusP1 = minus(endPos, controlPoint)

    function getDistanceAt(t: number): number {
        // apply the bezier function
        const pos = add(
            add(controlPoint, mul(p0MinusP1, (1 - t) ** 2)),
            mul(p2MinusP1, t ** 2),
        )
        return distance(pos, point)
    }

    for (let t = 0; t < 1; t += step) {
        if (getDistanceAt(t) <= minDistance)
            return t >= 0.5
                ? PointSegmentSearchResult.RIGHT_TO_CONTROL_POINT
                : PointSegmentSearchResult.LEFT_TO_CONTROL_POINT
    }

    return PointSegmentSearchResult.NOT_FOUND
}

let t = 0
let slice = 0.5
for (let i = 0; i < 100; i++) {
    t += slice
    slice /= 2
    //    console.log(t)
}

function ArrowPoint({
    className,
    posRatio,
    parentBase,
    onMoves,
    onPosValidated,
    onRemove,
    radius = 7,
}: ControlPointProps) {
    const ref = useRef<HTMLDivElement>(null)

    const pos = posWithinBase(posRatio, parentBase)

    return (
        <Draggable
            nodeRef={ref}
            onStop={() => {
                const pointPos = middlePos(ref.current!.getBoundingClientRect())
                onPosValidated(ratioWithinBase(pointPos, parentBase))
            }}
            onDrag={() => {
                const pointPos = middlePos(ref.current!.getBoundingClientRect())
                onMoves(ratioWithinBase(pointPos, parentBase))
            }}
            position={{ x: pos.x - radius, y: pos.y - radius }}>
            <div
                ref={ref}
                className={`arrow-point ${className}`}
                style={{
                    position: "absolute",
                    width: radius * 2,
                    height: radius * 2,
                }}
                onKeyUp={(e) => {
                    if (e.key == "Delete") {
                        onRemove()
                    }
                }}
                tabIndex={0}
            />
        </Draggable>
    )
}