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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 | 'use client' import { useRef, useState, useEffect, useCallback } from 'react' import type { RulerState, EquationProbeState, Fraction } from './types' import type { CoordinatePlaneState } from '../types' import { rulerToScreen } from './renderRuler' import { equationFromPoints, solveForY, solveForX } from './fractionMath' import { decayingSin } from '../../shared/animationMath' /** How close (in world units) the probe must be to an integer grid line to snap */ const GRID_SNAP_THRESHOLD = 0.15 /** Movement threshold (px) to distinguish click from drag */ const CLICK_THRESHOLD = 5 interface UseEquationSliderOptions { rulerRef: React.MutableRefObject<RulerState> stateRef: React.MutableRefObject<CoordinatePlaneState> canvasRef: React.RefObject<HTMLCanvasElement | null> probeRef: React.MutableRefObject<EquationProbeState> requestDraw: () => void pointerCapturedRef: React.MutableRefObject<boolean> /** Incremented when ruler position changes — triggers spring snap-back */ rulerVersion: number /** Called on click (pointer down + up with < 5px movement) */ onClickLabel?: () => void } interface UseEquationSliderResult { sliderT: number isDragging: boolean isSpringAnimating: boolean handlePointerDown: (e: React.PointerEvent) => void probeWorld: { x: number; y: number } nearX: number | null nearY: number | null solvedAtNearX: { x: number; yFrac: Fraction } | null solvedAtNearY: { y: number; xFrac: Fraction } | null } export function useEquationSlider({ rulerRef, stateRef, canvasRef, probeRef, requestDraw, pointerCapturedRef, rulerVersion, onClickLabel, }: UseEquationSliderOptions): UseEquationSliderResult { const [sliderT, setSliderT] = useState(0.5) const [isDragging, setIsDragging] = useState(false) const [isSpringAnimating, setIsSpringAnimating] = useState(false) // Probe solving state const [nearX, setNearX] = useState<number | null>(null) const [nearY, setNearY] = useState<number | null>(null) const [solvedAtNearX, setSolvedAtNearX] = useState<{ x: number; yFrac: Fraction } | null>(null) const [solvedAtNearY, setSolvedAtNearY] = useState<{ y: number; xFrac: Fraction } | null>(null) const [probeWorld, setProbeWorld] = useState({ x: 0, y: 0 }) // Internal refs for drag const dragStartScreenRef = useRef({ x: 0, y: 0 }) const dragStartTRef = useRef(0.5) const rulerDirScreenRef = useRef({ x: 1, y: 0, lengthPx: 1 }) const springRafRef = useRef(0) const didMoveRef = useRef(false) const updateProbe = useCallback( (t: number, solve = true): number => { const ruler = rulerRef.current const dxRuler = ruler.bx - ruler.ax const dyRuler = ruler.by - ruler.ay // World position at t along the ruler line (unclamped — extends into laser) let wx = ruler.ax + dxRuler * t let wy = ruler.ay + dyRuler * t let effectiveT = t let nX: number | null = null let nY: number | null = null let solvX: { x: number; yFrac: Fraction } | null = null let solvY: { y: number; xFrac: Fraction } | null = null // Grid proximity detection + snap — only during manual drag, not spring if (solve) { const equation = equationFromPoints(ruler.ax, ruler.ay, ruler.bx, ruler.by) const roundedX = Math.round(wx) const roundedY = Math.round(wy) const distX = Math.abs(wx - roundedX) const distY = Math.abs(wy - roundedY) if (equation.kind === 'general') { if (distX < GRID_SNAP_THRESHOLD) { nX = roundedX solvX = { x: roundedX, yFrac: solveForY(equation.slope, equation.intercept, roundedX) } } if (distY < GRID_SNAP_THRESHOLD) { nY = roundedY solvY = { y: roundedY, xFrac: solveForX(equation.slope, equation.intercept, roundedY) } } } else if (equation.kind === 'horizontal') { if (distX < GRID_SNAP_THRESHOLD) { nX = roundedX solvX = { x: roundedX, yFrac: { num: equation.y, den: 1 } } } } else if (equation.kind === 'vertical') { if (distY < GRID_SNAP_THRESHOLD) { nY = roundedY solvY = { y: roundedY, xFrac: { num: equation.x, den: 1 } } } } // Snap t to the nearest detected grid line if (nX !== null || nY !== null) { if (nX !== null && nY !== null) { // Both in range — snap to whichever is closer if (distX <= distY && Math.abs(dxRuler) > 0.001) { effectiveT = (roundedX - ruler.ax) / dxRuler } else if (Math.abs(dyRuler) > 0.001) { effectiveT = (roundedY - ruler.ay) / dyRuler } } else if (nX !== null && Math.abs(dxRuler) > 0.001) { effectiveT = (roundedX - ruler.ax) / dxRuler } else if (nY !== null && Math.abs(dyRuler) > 0.001) { effectiveT = (roundedY - ruler.ay) / dyRuler } // Recompute world position from snapped t wx = ruler.ax + dxRuler * effectiveT wy = ruler.ay + dyRuler * effectiveT } } setNearX(nX) setNearY(nY) setSolvedAtNearX(solvX) setSolvedAtNearY(solvY) setProbeWorld({ x: wx, y: wy }) // Update ref for canvas to read probeRef.current = { active: true, t: effectiveT, worldX: wx, worldY: wy, nearX: nX, nearY: nY, solvedAtNearX: solvX, solvedAtNearY: solvY, } requestDraw() return effectiveT }, [rulerRef, probeRef, requestDraw] ) const clearProbe = useCallback(() => { setNearX(null) setNearY(null) setSolvedAtNearX(null) setSolvedAtNearY(null) probeRef.current = { ...probeRef.current, active: false, // Don't touch t — preserve label position; callers reset t explicitly nearX: null, nearY: null, solvedAtNearX: null, solvedAtNearY: null, } requestDraw() }, [probeRef, requestDraw]) // Track whether a spring-back has already been triggered for the current displacement. // Prevents re-triggering on every rulerVersion tick during a continuous ruler drag. const springTriggeredRef = useRef(false) // Spring snap-back animation const startSpring = useCallback( (fromT: number) => { // Cancel any existing spring before starting a new one cancelAnimationFrame(springRafRef.current) const amplitude = fromT - 0.5 if (Math.abs(amplitude) < 0.001) { setSliderT(0.5) probeRef.current.t = 0.5 clearProbe() return } setIsSpringAnimating(true) const startTime = performance.now() function animate() { const elapsed = (performance.now() - startTime) / 1000 // seconds const offset = amplitude * decayingSin(elapsed, 3, 6) if (Math.abs(offset) < 0.001 || elapsed > 1) { // Settled setSliderT(0.5) probeRef.current.t = 0.5 setIsSpringAnimating(false) clearProbe() cancelAnimationFrame(springRafRef.current) return } const t = 0.5 + offset setSliderT(t) updateProbe(t, false) springRafRef.current = requestAnimationFrame(animate) } springRafRef.current = requestAnimationFrame(animate) }, [clearProbe, updateProbe, probeRef] ) // Cleanup spring RAF on unmount useEffect(() => { return () => cancelAnimationFrame(springRafRef.current) }, []) // Spring back to midpoint when ruler position changes (skip initial mount). // Only triggers once per displacement — springTriggeredRef prevents re-firing // on every rulerVersion tick during a continuous ruler drag. const prevRulerVersionRef = useRef(rulerVersion) useEffect(() => { if (prevRulerVersionRef.current === rulerVersion) return prevRulerVersionRef.current = rulerVersion if (springTriggeredRef.current) return // already springing back // Read current t via state updater to avoid stale closure setSliderT((currentT) => { if (Math.abs(currentT - 0.5) > 0.001) { springTriggeredRef.current = true startSpring(currentT) } return currentT }) }, [rulerVersion, startSpring]) // Pointer event handlers const handlePointerDown = useCallback( (e: React.PointerEvent) => { e.stopPropagation() e.preventDefault() // Cancel any running spring cancelAnimationFrame(springRafRef.current) setIsSpringAnimating(false) springTriggeredRef.current = false setIsDragging(true) pointerCapturedRef.current = true const canvas = canvasRef.current if (!canvas) return const rect = canvas.getBoundingClientRect() const dpr = window.devicePixelRatio || 1 const cssWidth = canvas.width / dpr const cssHeight = canvas.height / dpr // Compute ruler direction in screen space const ruler = rulerRef.current const info = rulerToScreen(ruler, stateRef.current, cssWidth, cssHeight) const dirX = info.bx - info.ax const dirY = info.by - info.ay const lengthPx = Math.sqrt(dirX * dirX + dirY * dirY) rulerDirScreenRef.current = { x: lengthPx > 0 ? dirX / lengthPx : 1, y: lengthPx > 0 ? dirY / lengthPx : 0, lengthPx, } dragStartScreenRef.current = { x: e.clientX, y: e.clientY } dragStartTRef.current = sliderT didMoveRef.current = false // Set up window-level listeners for move and up const onPointerMove = (ev: PointerEvent) => { const deltaScreenX = ev.clientX - dragStartScreenRef.current.x const deltaScreenY = ev.clientY - dragStartScreenRef.current.y // Check if movement exceeds click threshold if (!didMoveRef.current) { const dist = Math.sqrt(deltaScreenX * deltaScreenX + deltaScreenY * deltaScreenY) if (dist >= CLICK_THRESHOLD) { didMoveRef.current = true } else { return // Don't start dragging until threshold exceeded } } const dir = rulerDirScreenRef.current // Project screen delta onto ruler direction const projectedPx = deltaScreenX * dir.x + deltaScreenY * dir.y const deltaT = dir.lengthPx > 0 ? projectedPx / dir.lengthPx : 0 const newT = dragStartTRef.current + deltaT const effectiveT = updateProbe(newT) setSliderT(effectiveT) } const onPointerUp = () => { window.removeEventListener('pointermove', onPointerMove) window.removeEventListener('pointerup', onPointerUp) setIsDragging(false) pointerCapturedRef.current = false // Click (no significant movement) → toggle equation form if (!didMoveRef.current) { onClickLabel?.() return } // If at a solve point, keep the probe active with indicators visible. // Otherwise just clear solve state but keep position. const probe = probeRef.current if (probe.nearX == null && probe.nearY == null) { clearProbe() } } window.addEventListener('pointermove', onPointerMove) window.addEventListener('pointerup', onPointerUp) }, [ canvasRef, rulerRef, stateRef, sliderT, pointerCapturedRef, updateProbe, clearProbe, onClickLabel, ] ) return { sliderT, isDragging, isSpringAnimating, handlePointerDown, probeWorld, nearX, nearY, solvedAtNearX, solvedAtNearY, } } |