mini-prog/miniprogram/engine/renderer/webglVectorRenderer.ts

import { getTileSizePx, type CameraState } from '../camera/camera'
import { worldTileToLonLat } from '../../utils/projection'
import { type MapScene } from './mapRenderer'
import { CourseLayer, type ProjectedCourseLayers, type ProjectedCourseLeg } from '../layer/courseLayer'
import { TrackLayer } from '../layer/trackLayer'
import { GpsLayer } from '../layer/gpsLayer'

const COURSE_COLOR: [number, number, number, number] = [0.8, 0.0, 0.42, 0.96]
const COMPLETED_ROUTE_COLOR: [number, number, number, number] = [0.48, 0.5, 0.54, 0.82]
const SKIPPED_ROUTE_COLOR: [number, number, number, number] = [0.38, 0.4, 0.44, 0.72]
const ACTIVE_CONTROL_COLOR: [number, number, number, number] = [0.22, 1, 0.95, 1]
const READY_CONTROL_COLOR: [number, number, number, number] = [0.38, 1, 0.92, 1]
const MULTI_ACTIVE_CONTROL_COLOR: [number, number, number, number] = [1, 0.8, 0.2, 0.98]
const FOCUSED_CONTROL_COLOR: [number, number, number, number] = [0.98, 0.96, 0.98, 1]
const MULTI_ACTIVE_PULSE_COLOR: [number, number, number, number] = [0.18, 1, 0.96, 0.86]
const FOCUSED_PULSE_COLOR: [number, number, number, number] = [1, 0.36, 0.84, 0.88]
const READY_PULSE_COLOR: [number, number, number, number] = [0.44, 1, 0.92, 0.98]
const COMPLETED_SETTLE_COLOR: [number, number, number, number] = [0.86, 0.9, 0.94, 0.24]
const SKIPPED_SETTLE_COLOR: [number, number, number, number] = [0.72, 0.76, 0.82, 0.18]
const SKIPPED_SLASH_COLOR: [number, number, number, number] = [0.78, 0.82, 0.88, 0.9]
const ACTIVE_LEG_COLOR: [number, number, number, number] = [0.18, 1, 0.94, 0.5]
const EARTH_CIRCUMFERENCE_METERS = 40075016.686
const CONTROL_RING_WIDTH_RATIO = 0.2
const FINISH_INNER_RADIUS_RATIO = 0.6
const FINISH_RING_WIDTH_RATIO = 0.2
const START_RING_WIDTH_RATIO = 0.2
const LEG_WIDTH_RATIO = 0.2
const LEG_TRIM_TO_RING_CENTER_RATIO = 1 - CONTROL_RING_WIDTH_RATIO / 2
const ACTIVE_CONTROL_PULSE_SPEED = 0.18
const ACTIVE_CONTROL_PULSE_MIN_SCALE = 1.12
const ACTIVE_CONTROL_PULSE_MAX_SCALE = 1.46
const ACTIVE_CONTROL_PULSE_WIDTH_RATIO = 0.12
const GUIDE_FLOW_COUNT = 5
const GUIDE_FLOW_SPEED = 0.02
const GUIDE_FLOW_TRAIL = 0.16
const GUIDE_FLOW_MIN_WIDTH_RATIO = 0.12
const GUIDE_FLOW_MAX_WIDTH_RATIO = 0.22
const GUIDE_FLOW_HEAD_RADIUS_RATIO = 0.18

type RgbaColor = [number, number, number, number]

function createShader(gl: any, type: number, source: string): any {
  const shader = gl.createShader(type)
  if (!shader) {
    throw new Error('WebGL shader 创建失败')
  }

  gl.shaderSource(shader, source)
  gl.compileShader(shader)
  if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
    const message = gl.getShaderInfoLog(shader) || 'unknown shader error'
    gl.deleteShader(shader)
    throw new Error(message)
  }

  return shader
}

function createProgram(gl: any, vertexSource: string, fragmentSource: string): any {
  const vertexShader = createShader(gl, gl.VERTEX_SHADER, vertexSource)
  const fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, fragmentSource)
  const program = gl.createProgram()
  if (!program) {
    throw new Error('WebGL program 创建失败')
  }

  gl.attachShader(program, vertexShader)
  gl.attachShader(program, fragmentShader)
  gl.linkProgram(program)
  gl.deleteShader(vertexShader)
  gl.deleteShader(fragmentShader)

  if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
    const message = gl.getProgramInfoLog(program) || 'unknown program error'
    gl.deleteProgram(program)
    throw new Error(message)
  }

  return program
}

export class WebGLVectorRenderer {
  canvas: any
  gl: any
  dpr: number
  courseLayer: CourseLayer
  trackLayer: TrackLayer
  gpsLayer: GpsLayer
  program: any
  positionBuffer: any
  colorBuffer: any
  positionLocation: number
  colorLocation: number

  constructor(courseLayer: CourseLayer, trackLayer: TrackLayer, gpsLayer: GpsLayer) {
    this.canvas = null
    this.gl = null
    this.dpr = 1
    this.courseLayer = courseLayer
    this.trackLayer = trackLayer
    this.gpsLayer = gpsLayer
    this.program = null
    this.positionBuffer = null
    this.colorBuffer = null
    this.positionLocation = -1
    this.colorLocation = -1
  }

  attachCanvas(canvasNode: any, width: number, height: number, dpr: number): void {
    this.canvas = canvasNode
    this.dpr = dpr || 1
    canvasNode.width = Math.max(1, Math.floor(width * this.dpr))
    canvasNode.height = Math.max(1, Math.floor(height * this.dpr))
    this.attachContext(canvasNode.getContext('webgl') || canvasNode.getContext('experimental-webgl'), canvasNode)
  }

  attachContext(gl: any, canvasNode: any): void {
    if (!gl) {
      throw new Error('当前环境不支持 WebGL Vector Layer')
    }

    this.canvas = canvasNode
    this.gl = gl
    this.program = createProgram(
      gl,
      'attribute vec2 a_position; attribute vec4 a_color; varying vec4 v_color; void main() { gl_Position = vec4(a_position, 0.0, 1.0); v_color = a_color; }',
      'precision mediump float; varying vec4 v_color; void main() { gl_FragColor = v_color; }',
    )
    this.positionBuffer = gl.createBuffer()
    this.colorBuffer = gl.createBuffer()
    this.positionLocation = gl.getAttribLocation(this.program, 'a_position')
    this.colorLocation = gl.getAttribLocation(this.program, 'a_color')

    gl.viewport(0, 0, canvasNode.width, canvasNode.height)
    gl.enable(gl.BLEND)
    gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)
  }

  destroy(): void {
    if (this.gl) {
      if (this.program) {
        this.gl.deleteProgram(this.program)
      }
      if (this.positionBuffer) {
        this.gl.deleteBuffer(this.positionBuffer)
      }
      if (this.colorBuffer) {
        this.gl.deleteBuffer(this.colorBuffer)
      }
    }

    this.program = null
    this.positionBuffer = null
    this.colorBuffer = null
    this.gl = null
    this.canvas = null
  }

  render(scene: MapScene, pulseFrame: number): void {
    if (!this.gl || !this.program || !this.positionBuffer || !this.colorBuffer || !this.canvas) {
      return
    }

    const gl = this.gl
    const course = this.courseLayer.projectCourse(scene)
    const trackPoints = this.trackLayer.projectPoints(scene)
    const gpsPoint = this.gpsLayer.projectPoint(scene)
    const positions: number[] = []
    const colors: number[] = []

    if (course) {
      this.pushCourse(positions, colors, course, scene, pulseFrame)
    }

    for (let index = 1; index < trackPoints.length; index += 1) {
      this.pushSegment(positions, colors, trackPoints[index - 1], trackPoints[index], 6, [0.09, 0.43, 0.36, 0.96], scene)
    }

    if (gpsPoint) {
      this.pushCircle(positions, colors, gpsPoint.x, gpsPoint.y, this.gpsLayer.getPulseRadius(pulseFrame), [0.13, 0.62, 0.74, 0.22], scene)
      this.pushCircle(positions, colors, gpsPoint.x, gpsPoint.y, 13, [1, 1, 1, 0.95], scene)
      this.pushCircle(positions, colors, gpsPoint.x, gpsPoint.y, 9, [0.13, 0.63, 0.74, 1], scene)
    }

    if (!positions.length) {
      return
    }

    gl.viewport(0, 0, this.canvas.width, this.canvas.height)
    gl.useProgram(this.program)

    gl.bindBuffer(gl.ARRAY_BUFFER, this.positionBuffer)
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STREAM_DRAW)
    gl.enableVertexAttribArray(this.positionLocation)
    gl.vertexAttribPointer(this.positionLocation, 2, gl.FLOAT, false, 0, 0)

    gl.bindBuffer(gl.ARRAY_BUFFER, this.colorBuffer)
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STREAM_DRAW)
    gl.enableVertexAttribArray(this.colorLocation)
    gl.vertexAttribPointer(this.colorLocation, 4, gl.FLOAT, false, 0, 0)

    gl.drawArrays(gl.TRIANGLES, 0, positions.length / 2)
  }

  isLite(scene: MapScene): boolean {
    return scene.animationLevel === 'lite'
  }

  getRingSegments(scene: MapScene): number {
    return this.isLite(scene) ? 24 : 36
  }

  getCircleSegments(scene: MapScene): number {
    return this.isLite(scene) ? 14 : 20
  }

  getPixelsPerMeter(scene: MapScene): number {
    const camera: CameraState = {
      centerWorldX: scene.exactCenterWorldX,
      centerWorldY: scene.exactCenterWorldY,
      viewportWidth: scene.viewportWidth,
      viewportHeight: scene.viewportHeight,
      visibleColumns: scene.visibleColumns,
    }
    const tileSizePx = getTileSizePx(camera)
    const centerLonLat = worldTileToLonLat({ x: scene.exactCenterWorldX, y: scene.exactCenterWorldY }, scene.zoom)
    const metersPerTile = Math.cos(centerLonLat.lat * Math.PI / 180) * EARTH_CIRCUMFERENCE_METERS / Math.pow(2, scene.zoom)
    if (!tileSizePx || !metersPerTile) {
      return 0
    }
    return tileSizePx / metersPerTile
  }

  getMetric(scene: MapScene, meters: number): number {
    return meters * this.getPixelsPerMeter(scene)
  }

  getControlRadiusMeters(scene: MapScene): number {
    return scene.cpRadiusMeters > 0 ? scene.cpRadiusMeters : 5
  }

  pushCourse(
    positions: number[],
    colors: number[],
    course: ProjectedCourseLayers,
    scene: MapScene,
    pulseFrame: number,
  ): void {
    const controlRadiusMeters = this.getControlRadiusMeters(scene)

    if (scene.revealFullCourse && scene.showCourseLegs) {
      for (let index = 0; index < course.legs.length; index += 1) {
        const leg = course.legs[index]
        this.pushCourseLeg(positions, colors, leg, controlRadiusMeters, this.getLegColor(scene, index), scene)
        if (scene.guidanceLegAnimationEnabled && scene.activeLegIndices.includes(index)) {
          this.pushCourseLegHighlight(positions, colors, leg, controlRadiusMeters, scene)
        }
      }

      const guideLeg = this.getGuideLeg(course, scene)
      if (guideLeg) {
        this.pushGuidanceFlow(positions, colors, guideLeg, controlRadiusMeters, scene, pulseFrame)
      }
    }

    for (const start of course.starts) {
      if (scene.activeStart) {
        this.pushActiveStartPulse(positions, colors, start.point.x, start.point.y, start.headingDeg, controlRadiusMeters, scene, pulseFrame)
      }
      if (scene.completedStart) {
        this.pushRing(
          positions,
          colors,
          start.point.x,
          start.point.y,
          this.getMetric(scene, controlRadiusMeters * 1.16),
          this.getMetric(scene, controlRadiusMeters * 1.02),
          COMPLETED_SETTLE_COLOR,
          scene,
        )
      }
      this.pushStartTriangle(positions, colors, start.point.x, start.point.y, start.headingDeg, controlRadiusMeters, this.getStartColor(scene), scene)
    }
    if (!scene.revealFullCourse) {
      return
    }

    for (const control of course.controls) {
      if (scene.activeControlSequences.includes(control.sequence)) {
        if (scene.controlVisualMode === 'single-target') {
          this.pushActiveControlPulse(positions, colors, control.point.x, control.point.y, controlRadiusMeters, scene, pulseFrame)
        } else {
          this.pushActiveControlPulse(positions, colors, control.point.x, control.point.y, controlRadiusMeters, scene, pulseFrame, MULTI_ACTIVE_PULSE_COLOR)
          if (!this.isLite(scene)) {
            this.pushActiveControlPulse(positions, colors, control.point.x, control.point.y, controlRadiusMeters * 1.2, scene, pulseFrame + 9, [0.9, 1, 1, 0.52])
          }
        }
      }

      if (scene.readyControlSequences.includes(control.sequence)) {
        this.pushActiveControlPulse(positions, colors, control.point.x, control.point.y, controlRadiusMeters * 1.04, scene, pulseFrame, READY_PULSE_COLOR)
        if (!this.isLite(scene)) {
          this.pushActiveControlPulse(positions, colors, control.point.x, control.point.y, controlRadiusMeters * 1.22, scene, pulseFrame + 11, [0.92, 1, 1, 0.42])
        }
        this.pushRing(
          positions,
          colors,
          control.point.x,
          control.point.y,
          this.getMetric(scene, controlRadiusMeters * 1.16),
          this.getMetric(scene, controlRadiusMeters * 1.02),
          READY_CONTROL_COLOR,
          scene,
        )
      }

      this.pushRing(
        positions,
        colors,
        control.point.x,
        control.point.y,
        this.getMetric(scene, controlRadiusMeters),
        this.getMetric(scene, controlRadiusMeters * (1 - CONTROL_RING_WIDTH_RATIO)),
        this.getControlColor(scene, control.sequence),
        scene,
      )

      if (scene.focusedControlSequences.includes(control.sequence)) {
        this.pushActiveControlPulse(positions, colors, control.point.x, control.point.y, controlRadiusMeters * 1.02, scene, pulseFrame, FOCUSED_PULSE_COLOR)
        if (!this.isLite(scene)) {
          this.pushActiveControlPulse(positions, colors, control.point.x, control.point.y, controlRadiusMeters * 1.32, scene, pulseFrame + 15, [1, 0.86, 0.94, 0.5])
        }
        this.pushRing(
          positions,
          colors,
          control.point.x,
          control.point.y,
          this.getMetric(scene, controlRadiusMeters * 1.24),
          this.getMetric(scene, controlRadiusMeters * 1.06),
          FOCUSED_CONTROL_COLOR,
          scene,
        )
      }

      if (scene.completedControlSequences.includes(control.sequence)) {
        this.pushRing(
          positions,
          colors,
          control.point.x,
          control.point.y,
          this.getMetric(scene, controlRadiusMeters * 1.14),
          this.getMetric(scene, controlRadiusMeters * 1.02),
          COMPLETED_SETTLE_COLOR,
          scene,
        )
      }

      if (this.isSkippedControl(scene, control.sequence)) {
        this.pushRing(
          positions,
          colors,
          control.point.x,
          control.point.y,
          this.getMetric(scene, controlRadiusMeters * 1.1),
          this.getMetric(scene, controlRadiusMeters * 1.01),
          SKIPPED_SETTLE_COLOR,
          scene,
        )
        this.pushSkippedControlSlash(positions, colors, control.point.x, control.point.y, controlRadiusMeters, scene)
      }
    }

    for (const finish of course.finishes) {
      if (scene.activeFinish) {
        this.pushActiveControlPulse(positions, colors, finish.point.x, finish.point.y, controlRadiusMeters, scene, pulseFrame)
      }
      if (scene.focusedFinish) {
        this.pushActiveControlPulse(positions, colors, finish.point.x, finish.point.y, controlRadiusMeters * 1.04, scene, pulseFrame, FOCUSED_PULSE_COLOR)
        if (!this.isLite(scene)) {
          this.pushActiveControlPulse(positions, colors, finish.point.x, finish.point.y, controlRadiusMeters * 1.34, scene, pulseFrame + 12, [1, 0.86, 0.94, 0.46])
        }
      }

      const finishColor = this.getFinishColor(scene)
      if (scene.completedFinish) {
        this.pushRing(
          positions,
          colors,
          finish.point.x,
          finish.point.y,
          this.getMetric(scene, controlRadiusMeters * 1.18),
          this.getMetric(scene, controlRadiusMeters * 1.02),
          COMPLETED_SETTLE_COLOR,
          scene,
        )
      }
      this.pushRing(
        positions,
        colors,
        finish.point.x,
        finish.point.y,
        this.getMetric(scene, controlRadiusMeters),
        this.getMetric(scene, controlRadiusMeters * (1 - FINISH_RING_WIDTH_RATIO)),
        finishColor,
        scene,
      )
      this.pushRing(
        positions,
        colors,
        finish.point.x,
        finish.point.y,
        this.getMetric(scene, controlRadiusMeters * FINISH_INNER_RADIUS_RATIO),
        this.getMetric(scene, controlRadiusMeters * FINISH_INNER_RADIUS_RATIO * (1 - FINISH_RING_WIDTH_RATIO / FINISH_INNER_RADIUS_RATIO)),
        finishColor,
        scene,
      )
    }
  }

  getGuideLeg(course: ProjectedCourseLayers, scene: MapScene): ProjectedCourseLeg | null {
    if (!scene.guidanceLegAnimationEnabled) {
      return null
    }

    const activeIndex = scene.activeLegIndices.length ? scene.activeLegIndices[0] : -1
    if (activeIndex >= 0 && activeIndex < course.legs.length) {
      return course.legs[activeIndex]
    }

    return null
  }

  getLegColor(scene: MapScene, index: number): RgbaColor {
    return this.isCompletedLeg(scene, index) ? COMPLETED_ROUTE_COLOR : COURSE_COLOR
  }

  isCompletedLeg(scene: MapScene, index: number): boolean {
    return scene.completedLegIndices.includes(index)
  }

  isSkippedControl(scene: MapScene, sequence: number): boolean {
    return scene.skippedControlSequences.includes(sequence)
  }

  pushCourseLeg(
    positions: number[],
    colors: number[],
    leg: ProjectedCourseLeg,
    controlRadiusMeters: number,
    color: RgbaColor,
    scene: MapScene,
  ): void {
    const trimmed = this.getTrimmedCourseLeg(leg, controlRadiusMeters, scene)
    if (!trimmed) {
      return
    }

    this.pushSegment(positions, colors, trimmed.from, trimmed.to, this.getMetric(scene, controlRadiusMeters * LEG_WIDTH_RATIO), color, scene)
  }

  pushCourseLegHighlight(
    positions: number[],
    colors: number[],
    leg: ProjectedCourseLeg,
    controlRadiusMeters: number,
    scene: MapScene,
  ): void {
    const trimmed = this.getTrimmedCourseLeg(leg, controlRadiusMeters, scene)
    if (!trimmed) {
      return
    }

    this.pushSegment(
      positions,
      colors,
      trimmed.from,
      trimmed.to,
      this.getMetric(scene, controlRadiusMeters * LEG_WIDTH_RATIO * 1.5),
      ACTIVE_LEG_COLOR,
      scene,
    )
  }

  pushActiveControlPulse(
    positions: number[],
    colors: number[],
    centerX: number,
    centerY: number,
    controlRadiusMeters: number,
    scene: MapScene,
    pulseFrame: number,
    pulseColor?: RgbaColor,
  ): void {
    const pulse = (Math.sin(pulseFrame * ACTIVE_CONTROL_PULSE_SPEED) + 1) / 2
    const pulseScale = ACTIVE_CONTROL_PULSE_MIN_SCALE + (ACTIVE_CONTROL_PULSE_MAX_SCALE - ACTIVE_CONTROL_PULSE_MIN_SCALE) * pulse
    const pulseWidthScale = pulseScale - ACTIVE_CONTROL_PULSE_WIDTH_RATIO
    const baseColor = pulseColor || ACTIVE_CONTROL_COLOR
    const glowAlpha = Math.min(1, baseColor[3] * (0.46 + pulse * 0.5))
    const glowColor: RgbaColor = [baseColor[0], baseColor[1], baseColor[2], glowAlpha]

    this.pushRing(
      positions,
      colors,
      centerX,
      centerY,
      this.getMetric(scene, controlRadiusMeters * pulseScale),
      this.getMetric(scene, controlRadiusMeters * Math.max(1, pulseWidthScale)),
      glowColor,
      scene,
    )
  }

  pushSkippedControlSlash(
    positions: number[],
    colors: number[],
    centerX: number,
    centerY: number,
    controlRadiusMeters: number,
    scene: MapScene,
  ): void {
    const slashRadius = this.getMetric(scene, controlRadiusMeters * 0.72)
    const slashWidth = this.getMetric(scene, controlRadiusMeters * 0.08)
    this.pushSegment(
      positions,
      colors,
      { x: centerX - slashRadius, y: centerY + slashRadius },
      { x: centerX + slashRadius, y: centerY - slashRadius },
      slashWidth,
      SKIPPED_SLASH_COLOR,
      scene,
    )
  }

  pushActiveStartPulse(
    positions: number[],
    colors: number[],
    centerX: number,
    centerY: number,
    headingDeg: number | null,
    controlRadiusMeters: number,
    scene: MapScene,
    pulseFrame: number,
  ): void {
    const pulse = (Math.sin(pulseFrame * ACTIVE_CONTROL_PULSE_SPEED) + 1) / 2
    const pulseScale = ACTIVE_CONTROL_PULSE_MIN_SCALE + (ACTIVE_CONTROL_PULSE_MAX_SCALE - ACTIVE_CONTROL_PULSE_MIN_SCALE) * pulse
    const pulseWidthScale = pulseScale - ACTIVE_CONTROL_PULSE_WIDTH_RATIO
    const glowAlpha = 0.24 + pulse * 0.34
    const glowColor: RgbaColor = [0.36, 1, 0.96, glowAlpha]
    const headingRad = ((headingDeg === null ? 0 : headingDeg) - 90) * Math.PI / 180
    const ringCenterX = centerX + Math.cos(headingRad) * this.getMetric(scene, controlRadiusMeters * 0.04)
    const ringCenterY = centerY + Math.sin(headingRad) * this.getMetric(scene, controlRadiusMeters * 0.04)

    this.pushRing(
      positions,
      colors,
      ringCenterX,
      ringCenterY,
      this.getMetric(scene, controlRadiusMeters * pulseScale),
      this.getMetric(scene, controlRadiusMeters * Math.max(1, pulseWidthScale)),
      glowColor,
      scene,
    )
  }

  getStartColor(scene: MapScene): RgbaColor {
    if (scene.activeStart) {
      return ACTIVE_CONTROL_COLOR
    }

    if (scene.completedStart) {
      return COMPLETED_ROUTE_COLOR
    }

    return COURSE_COLOR
  }

  getControlColor(scene: MapScene, sequence: number): RgbaColor {
    if (scene.readyControlSequences.includes(sequence)) {
      return READY_CONTROL_COLOR
    }

    if (scene.activeControlSequences.includes(sequence)) {
      return scene.controlVisualMode === 'multi-target' ? MULTI_ACTIVE_CONTROL_COLOR : ACTIVE_CONTROL_COLOR
    }

    if (scene.completedControlSequences.includes(sequence)) {
      return COMPLETED_ROUTE_COLOR
    }

    if (this.isSkippedControl(scene, sequence)) {
      return SKIPPED_ROUTE_COLOR
    }

    return COURSE_COLOR
  }


  getFinishColor(scene: MapScene): RgbaColor {
    if (scene.focusedFinish) {
      return FOCUSED_CONTROL_COLOR
    }

    if (scene.activeFinish) {
      return ACTIVE_CONTROL_COLOR
    }

    if (scene.completedFinish) {
      return COMPLETED_ROUTE_COLOR
    }

    return COURSE_COLOR
  }

  pushGuidanceFlow(
    positions: number[],
    colors: number[],
    leg: ProjectedCourseLeg,
    controlRadiusMeters: number,
    scene: MapScene,
    pulseFrame: number,
  ): void {
    const trimmed = this.getTrimmedCourseLeg(leg, controlRadiusMeters, scene)
    if (!trimmed) {
      return
    }

    const dx = trimmed.to.x - trimmed.from.x
    const dy = trimmed.to.y - trimmed.from.y
    const length = Math.sqrt(dx * dx + dy * dy)
    if (!length) {
      return
    }

    for (let index = 0; index < GUIDE_FLOW_COUNT; index += 1) {
      const progress = (pulseFrame * GUIDE_FLOW_SPEED + index / GUIDE_FLOW_COUNT) % 1
      const tailProgress = Math.max(0, progress - GUIDE_FLOW_TRAIL)
      const head = {
        x: trimmed.from.x + dx * progress,
        y: trimmed.from.y + dy * progress,
      }
      const tail = {
        x: trimmed.from.x + dx * tailProgress,
        y: trimmed.from.y + dy * tailProgress,
      }
      const eased = progress * progress
      const width = this.getMetric(
        scene,
        controlRadiusMeters * (GUIDE_FLOW_MIN_WIDTH_RATIO + (GUIDE_FLOW_MAX_WIDTH_RATIO - GUIDE_FLOW_MIN_WIDTH_RATIO) * eased),
      )
      const outerColor = this.getGuideFlowOuterColor(eased)
      const innerColor = this.getGuideFlowInnerColor(eased)
      const headRadius = this.getMetric(scene, controlRadiusMeters * GUIDE_FLOW_HEAD_RADIUS_RATIO * (0.72 + eased * 0.42))

      this.pushSegment(positions, colors, tail, head, width * 1.9, outerColor, scene)
      this.pushSegment(positions, colors, tail, head, width, innerColor, scene)
      this.pushCircle(positions, colors, head.x, head.y, headRadius * 1.35, outerColor, scene)
      this.pushCircle(positions, colors, head.x, head.y, headRadius, innerColor, scene)
    }
  }

  getTrimmedCourseLeg(
    leg: ProjectedCourseLeg,
    controlRadiusMeters: number,
    scene: MapScene,
  ): { from: { x: number; y: number }; to: { x: number; y: number } } | null {
    return this.trimSegment(
      leg.from,
      leg.to,
      this.getLegTrim(leg.fromKind, controlRadiusMeters, scene),
      this.getLegTrim(leg.toKind, controlRadiusMeters, scene),
    )
  }

  getGuideFlowOuterColor(progress: number): RgbaColor {
    return [0.28, 0.92, 1, 0.14 + progress * 0.22]
  }

  getGuideFlowInnerColor(progress: number): RgbaColor {
    return [0.94, 0.99, 1, 0.38 + progress * 0.42]
  }

  getLegTrim(kind: ProjectedCourseLeg['fromKind'], controlRadiusMeters: number, scene: MapScene): number {
    if (kind === 'start') {
      return this.getMetric(scene, controlRadiusMeters * (1 - START_RING_WIDTH_RATIO / 2))
    }

    if (kind === 'finish') {
      return this.getMetric(scene, controlRadiusMeters * (1 - FINISH_RING_WIDTH_RATIO / 2))
    }

    return this.getMetric(scene, controlRadiusMeters * LEG_TRIM_TO_RING_CENTER_RATIO)
  }

  trimSegment(
    from: { x: number; y: number },
    to: { x: number; y: number },
    fromTrim: number,
    toTrim: number,
  ): { from: { x: number; y: number }; to: { x: number; y: number } } | null {
    const dx = to.x - from.x
    const dy = to.y - from.y
    const length = Math.sqrt(dx * dx + dy * dy)
    if (!length || length <= fromTrim + toTrim) {
      return null
    }

    const ux = dx / length
    const uy = dy / length
    return {
      from: {
        x: from.x + ux * fromTrim,
        y: from.y + uy * fromTrim,
      },
      to: {
        x: to.x - ux * toTrim,
        y: to.y - uy * toTrim,
      },
    }
  }

  pushStartTriangle(
    positions: number[],
    colors: number[],
    centerX: number,
    centerY: number,
    headingDeg: number | null,
    controlRadiusMeters: number,
    color: RgbaColor,
    scene: MapScene,
  ): void {
    const startRadius = this.getMetric(scene, controlRadiusMeters)
    const startRingWidth = this.getMetric(scene, controlRadiusMeters * START_RING_WIDTH_RATIO)
    const headingRad = ((headingDeg === null ? 0 : headingDeg) - 90) * Math.PI / 180
    const vertices = [0, 1, 2].map((index) => {
      const angle = headingRad + index * (Math.PI * 2 / 3)
      return {
        x: centerX + Math.cos(angle) * startRadius,
        y: centerY + Math.sin(angle) * startRadius,
      }
    })

    this.pushSegment(positions, colors, vertices[0], vertices[1], startRingWidth, color, scene)
    this.pushSegment(positions, colors, vertices[1], vertices[2], startRingWidth, color, scene)
    this.pushSegment(positions, colors, vertices[2], vertices[0], startRingWidth, color, scene)
  }

  pushRing(
    positions: number[],
    colors: number[],
    centerX: number,
    centerY: number,
    outerRadius: number,
    innerRadius: number,
    color: RgbaColor,
    scene: MapScene,
  ): void {
    const segments = this.getRingSegments(scene)
    for (let index = 0; index < segments; index += 1) {
      const startAngle = index / segments * Math.PI * 2
      const endAngle = (index + 1) / segments * Math.PI * 2
      const outerStart = this.toClip(centerX + Math.cos(startAngle) * outerRadius, centerY + Math.sin(startAngle) * outerRadius, scene)
      const outerEnd = this.toClip(centerX + Math.cos(endAngle) * outerRadius, centerY + Math.sin(endAngle) * outerRadius, scene)
      const innerStart = this.toClip(centerX + Math.cos(startAngle) * innerRadius, centerY + Math.sin(startAngle) * innerRadius, scene)
      const innerEnd = this.toClip(centerX + Math.cos(endAngle) * innerRadius, centerY + Math.sin(endAngle) * innerRadius, scene)
      this.pushTriangle(positions, colors, outerStart, outerEnd, innerStart, color)
      this.pushTriangle(positions, colors, innerStart, outerEnd, innerEnd, color)
    }
  }

  pushSegment(
    positions: number[],
    colors: number[],
    start: { x: number; y: number },
    end: { x: number; y: number },
    width: number,
    color: RgbaColor,
    scene: MapScene,
  ): void {
    const deltaX = end.x - start.x
    const deltaY = end.y - start.y
    const length = Math.sqrt(deltaX * deltaX + deltaY * deltaY)
    if (!length) {
      return
    }

    const normalX = -deltaY / length * (width / 2)
    const normalY = deltaX / length * (width / 2)
    const topLeft = this.toClip(start.x + normalX, start.y + normalY, scene)
    const topRight = this.toClip(end.x + normalX, end.y + normalY, scene)
    const bottomLeft = this.toClip(start.x - normalX, start.y - normalY, scene)
    const bottomRight = this.toClip(end.x - normalX, end.y - normalY, scene)

    this.pushTriangle(positions, colors, topLeft, topRight, bottomLeft, color)
    this.pushTriangle(positions, colors, bottomLeft, topRight, bottomRight, color)
  }

  pushCircle(
    positions: number[],
    colors: number[],
    centerX: number,
    centerY: number,
    radius: number,
    color: RgbaColor,
    scene: MapScene,
  ): void {
    const segments = this.getCircleSegments(scene)
    const center = this.toClip(centerX, centerY, scene)
    for (let index = 0; index < segments; index += 1) {
      const startAngle = index / segments * Math.PI * 2
      const endAngle = (index + 1) / segments * Math.PI * 2
      const start = this.toClip(centerX + Math.cos(startAngle) * radius, centerY + Math.sin(startAngle) * radius, scene)
      const end = this.toClip(centerX + Math.cos(endAngle) * radius, centerY + Math.sin(endAngle) * radius, scene)
      this.pushTriangle(positions, colors, center, start, end, color)
    }
  }

  pushTriangle(
    positions: number[],
    colors: number[],
    first: { x: number; y: number },
    second: { x: number; y: number },
    third: { x: number; y: number },
    color: RgbaColor,
  ): void {
    positions.push(first.x, first.y, second.x, second.y, third.x, third.y)
    for (let index = 0; index < 3; index += 1) {
      colors.push(color[0], color[1], color[2], color[3])
    }
  }

  toClip(x: number, y: number, scene: MapScene): { x: number; y: number } {
    const previewScale = scene.previewScale || 1
    const originX = scene.previewOriginX || scene.viewportWidth / 2
    const originY = scene.previewOriginY || scene.viewportHeight / 2
    const scaledX = originX + (x - originX) * previewScale
    const scaledY = originY + (y - originY) * previewScale

    return {
      x: scaledX / scene.viewportWidth * 2 - 1,
      y: 1 - scaledY / scene.viewportHeight * 2,
    }
  }
}