114 lines
2.8 KiB
Go
114 lines
2.8 KiB
Go
package clockface
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import (
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"fmt"
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"io"
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"math"
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"time"
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)
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// Point represents a two-dimentional Cartesian coordinate
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type Point struct {
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X float64
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Y float64
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}
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const (
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hourHandLength = 50
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minuteHandLength = 80
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secondHandLength = 90
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clockCentreX = 150
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clockCentreY = 150
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)
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const (
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secondsInHalfClock = 30
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secondsInClock = 2 * secondsInHalfClock
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minutesInHalfClock = 30
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minutesInClock = 2 * minutesInHalfClock
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hoursInHalfClock = 6
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hoursInClock = 2 * hoursInHalfClock
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)
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const svgStart = `<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
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<svg xmlns="http://www.w3.org/2000/svg"
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width="100%"
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height="100%"
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viewBox="0 0 300 300"
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version="2.0">`
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const bezel = `<circle cx="150" cy="150" r="100" style="fill:#fff;stroke:#000;stroke-width:5px;"/>`
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const svgEnd = `</svg>`
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func SVGWriter(w io.Writer, t time.Time) {
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io.WriteString(w, svgStart)
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io.WriteString(w, bezel)
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secondHand(w, t)
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minuteHand(w, t)
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hourHand(w, t)
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io.WriteString(w, svgEnd)
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}
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// SecondHand is the unit vector of the second hand of an analogue clock at the time `t` represented as a Point
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func secondHand(w io.Writer, t time.Time) {
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p := secondHandPoint(t)
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makeHand(w, secondHandLength, p)
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}
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// MinuteHand is the unit vector of the minute hand of an analogue clock at the time `t` represented as a Point
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func minuteHand(w io.Writer, t time.Time) {
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p := minuteHandPoint(t)
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makeHand(w, minuteHandLength, p)
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}
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// MinuteHand is the unit vector of the minute hand of an analogue clock at the time `t` represented as a Point
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func hourHand(w io.Writer, t time.Time) {
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p := hourHandPoint(t)
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makeHand(w, hourHandLength, p)
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}
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func makeHand(w io.Writer, length float64, p Point) {
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p = Point{p.X * length, p.Y * length} // scale
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p = Point{p.X, -p.Y} // flip
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p = Point{p.X + clockCentreX, p.Y + clockCentreY} // translate
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fmt.Fprintf(
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w,
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`<line x1="150" y1="150" x2="%f" y2="%f" style="fill:none;stroke:#f00;stroke-width:3px;"/>`,
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p.X,
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p.Y,
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)
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}
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func hoursInRadians(t time.Time) float64 {
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return (minutesInRadians(t) / hoursInClock) + math.Pi/(hoursInHalfClock/float64(t.Hour()%hoursInClock))
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}
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func hourHandPoint(t time.Time) Point {
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return angleToPoint(hoursInRadians(t))
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}
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func minutesInRadians(t time.Time) float64 {
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return (secondsInRadians(t) / minutesInClock) + math.Pi/(minutesInHalfClock/float64(t.Minute()))
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}
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func minuteHandPoint(t time.Time) Point {
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return angleToPoint(minutesInRadians(t))
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}
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func secondsInRadians(t time.Time) float64 {
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return math.Pi / (secondsInHalfClock / float64(t.Second()))
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}
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func secondHandPoint(t time.Time) Point {
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return angleToPoint(secondsInRadians(t))
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}
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func angleToPoint(angle float64) Point {
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x := math.Sin(angle)
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y := math.Cos(angle)
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return Point{x, y}
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}
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