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via/internal/examples/maplibre/main.go
ryan 297808d4cc
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feat: animate fleet of container ships along bay waypoints (#13)
2026-02-20 21:10:24 +00:00

342 lines
9.0 KiB
Go

package main
import (
"fmt"
"math"
"math/rand"
"strconv"
"sync"
"time"
"github.com/ryanhamamura/via"
"github.com/ryanhamamura/via/h"
"github.com/ryanhamamura/via/maplibre"
)
type posMsg struct {
Lng float64 `json:"lng"`
Lat float64 `json:"lat"`
}
var (
vehicleOnce sync.Once
vehicle struct {
mu sync.RWMutex
lng, lat float64
}
)
// shipState tracks a ship lerping along a loop of waypoints.
type shipState struct {
lng, lat float64
waypoints [][2]float64 // [lng, lat] pairs
wpIdx int // index of next target waypoint
progress float64 // 0..1 toward next waypoint
speed float64 // progress increment per tick
}
func (s *shipState) tick() {
s.progress += s.speed
for s.progress >= 1 {
s.progress -= 1
s.wpIdx = (s.wpIdx + 1) % len(s.waypoints)
}
from := s.waypoints[(s.wpIdx-1+len(s.waypoints))%len(s.waypoints)]
to := s.waypoints[s.wpIdx]
s.lng = from[0] + (to[0]-from[0])*s.progress
s.lat = from[1] + (to[1]-from[1])*s.progress
}
// heading returns clockwise degrees from north (for SVG rotation).
func (s *shipState) heading() float64 {
from := s.waypoints[(s.wpIdx-1+len(s.waypoints))%len(s.waypoints)]
to := s.waypoints[s.wpIdx]
dx := to[0] - from[0]
dy := to[1] - from[1]
// atan2 gives angle from +X axis; convert to CW from north
return math.Mod(math.Atan2(dx, dy)*180/math.Pi+360, 360)
}
var (
fleetOnce sync.Once
fleet struct {
mu sync.RWMutex
ships [3]shipState
}
)
const shipSVG = `<svg width="48" height="28" viewBox="0 0 80 44" xmlns="http://www.w3.org/2000/svg">` +
`<path d="M2 30 L10 42 L70 42 L78 30 Z" fill="#1b3a5c"/>` +
`<rect x="12" y="24" width="56" height="6" rx="1" fill="#2c5f8a"/>` +
`<rect x="18" y="14" width="46" height="10" rx="1" fill="#2c5f8a" stroke="#1b3a5c" stroke-width="0.5"/>` +
`<rect x="8" y="12" width="9" height="12" rx="1" fill="#d5dfe8" stroke="#2c5f8a" stroke-width="0.5"/>` +
`<rect x="9.5" y="13" width="6" height="4" rx="0.5" fill="#85c1e9"/>` +
`<rect x="10" y="4" width="5" height="8" rx="0.5" fill="#1b3a5c"/>` +
`<rect x="9.5" y="2" width="6" height="3" rx="0.5" fill="#c0392b"/>` +
`</svg>`
func main() {
v := via.New()
v.Config(via.Options{
DocumentTitle: "MapLibre GL Example",
ServerAddress: ":7331",
DevMode: true,
Plugins: []via.Plugin{maplibre.Plugin},
})
// Single goroutine moves the vehicle — all clients read the same position.
vehicle.lng = -122.43
vehicle.lat = 37.77
vehicleOnce.Do(func() {
go func() {
for {
time.Sleep(time.Second)
vehicle.mu.Lock()
vehicle.lng = -122.43 + (rand.Float64()-0.5)*0.02
vehicle.lat = 37.77 + (rand.Float64()-0.5)*0.02
vehicle.mu.Unlock()
}
}()
})
// Fleet of ships following waypoint loops through SF Bay.
fleetOnce.Do(func() {
fleet.ships = [3]shipState{
{ // Golden Gate → Alcatraz → Pier 39 → back out
waypoints: [][2]float64{
{-122.478, 37.819}, {-122.423, 37.827},
{-122.410, 37.809}, {-122.423, 37.827},
},
speed: 0.03,
},
{ // Oakland → Treasure Island → Angel Island → loop
waypoints: [][2]float64{
{-122.330, 37.795}, {-122.370, 37.823},
{-122.432, 37.860}, {-122.370, 37.823},
},
speed: 0.02,
},
{ // Sausalito → Pier 39 ferry route
waypoints: [][2]float64{
{-122.480, 37.859}, {-122.435, 37.840},
{-122.410, 37.809}, {-122.435, 37.840},
},
speed: 0.025,
},
}
// Set initial positions.
for i := range fleet.ships {
s := &fleet.ships[i]
s.lng = s.waypoints[0][0]
s.lat = s.waypoints[0][1]
s.wpIdx = 1
}
go func() {
for {
time.Sleep(time.Second)
fleet.mu.Lock()
for i := range fleet.ships {
fleet.ships[i].tick()
}
fleet.mu.Unlock()
}
}()
})
v.Page("/", func(c *via.Context) {
m := maplibre.New(c, maplibre.Options{
Style: "https://demotiles.maplibre.org/style.json",
Center: maplibre.LngLat{Lng: -122.4194, Lat: 37.7749},
Zoom: 10,
Height: "500px",
})
m.AddControl("nav", maplibre.NavigationControl{})
m.AddControl("scale", maplibre.ScaleControl{Unit: "metric"})
// Static markers with popups
m.AddMarker("sf", maplibre.Marker{
LngLat: maplibre.LngLat{Lng: -122.4194, Lat: 37.7749},
Color: "#e74c3c",
Popup: &maplibre.Popup{
Content: "<strong>San Francisco</strong><p>The Golden City</p>",
},
})
m.AddMarker("oak", maplibre.Marker{
LngLat: maplibre.LngLat{Lng: -122.2711, Lat: 37.8044},
Color: "#2ecc71",
Popup: &maplibre.Popup{
Content: "<strong>Oakland</strong>",
},
})
// Animated container ships following waypoint routes
shipNames := [3]string{"MSC Adriatica", "Evergreen Harmony", "Maersk Aurora"}
type shipSignals struct{ lng, lat *via.Signal }
var ships [3]shipSignals
fleet.mu.RLock()
for i, s := range fleet.ships {
ships[i].lng = c.Signal(s.lng)
ships[i].lat = c.Signal(s.lat)
m.AddMarker(fmt.Sprintf("ship-%d", i), maplibre.Marker{
LngSignal: ships[i].lng,
LatSignal: ships[i].lat,
Element: shipSVG,
Anchor: "center",
Rotation: s.heading(),
Popup: &maplibre.Popup{
Content: fmt.Sprintf("<strong>%s</strong>", shipNames[i]),
},
})
}
fleet.mu.RUnlock()
// Custom SVG vehicle marker — reads shared Go state
vehicleLng := c.Signal(-122.43)
vehicleLat := c.Signal(37.77)
m.AddMarker("vehicle", maplibre.Marker{
LngSignal: vehicleLng,
LatSignal: vehicleLat,
Element: `<svg width="20" height="20" viewBox="0 0 20 20" xmlns="http://www.w3.org/2000/svg">` +
`<circle cx="10" cy="10" r="9" fill="#9b59b6" stroke="#fff" stroke-width="2"/>` +
`</svg>`,
Anchor: "center",
})
c.OnInterval(time.Second, func() {
vehicle.mu.RLock()
lng, lat := vehicle.lng, vehicle.lat
vehicle.mu.RUnlock()
vehicleLng.SetValue(lng)
vehicleLat.SetValue(lat)
fleet.mu.RLock()
for i, s := range fleet.ships {
ships[i].lng.SetValue(s.lng)
ships[i].lat.SetValue(s.lat)
}
fleet.mu.RUnlock()
c.SyncSignals()
})
// Yellow click marker — synced across clients via PubSub
clickLng := c.Signal(-122.4194)
clickLat := c.Signal(37.7749)
m.AddMarker("clicked", maplibre.Marker{
LngSignal: clickLng,
LatSignal: clickLat,
Color: "#f39c12",
})
via.Subscribe(c, "map.click", func(msg posMsg) {
clickLng.SetValue(msg.Lng)
clickLat.SetValue(msg.Lat)
c.SyncSignals()
})
click := m.OnClick()
handleClick := c.Action(func() {
e := click.Data()
via.Publish(c, "map.click", posMsg{Lng: e.LngLat.Lng, Lat: e.LngLat.Lat})
})
// Blue draggable pin — synced across clients via PubSub
pinLng := c.Signal(-122.41)
pinLat := c.Signal(37.78)
m.AddMarker("pin", maplibre.Marker{
LngSignal: pinLng,
LatSignal: pinLat,
Color: "#3498db",
Draggable: true,
})
via.Subscribe(c, "map.pin", func(msg posMsg) {
pinLng.SetValue(msg.Lng)
pinLat.SetValue(msg.Lat)
c.SyncSignals()
})
handlePinDrag := c.Action(func() {
lng, _ := strconv.ParseFloat(pinLng.String(), 64)
lat, _ := strconv.ParseFloat(pinLat.String(), 64)
via.Publish(c, "map.pin", posMsg{Lng: lng, Lat: lat})
})
// GeoJSON polygon source + fill layer
m.AddSource("park", maplibre.GeoJSONSource{
Data: map[string]any{
"type": "Feature",
"geometry": map[string]any{
"type": "Polygon",
"coordinates": []any{[]any{
[]float64{-122.4547, 37.7654},
[]float64{-122.4547, 37.7754},
[]float64{-122.4387, 37.7754},
[]float64{-122.4387, 37.7654},
[]float64{-122.4547, 37.7654},
}},
},
"properties": map[string]any{
"name": "Golden Gate Park",
},
},
})
m.AddLayer(maplibre.Layer{
ID: "park-fill",
Type: "fill",
Source: "park",
Paint: map[string]any{
"fill-color": "#2ecc71",
"fill-opacity": 0.3,
},
})
// FlyTo actions
zoom14 := 14.0
flyToSF := c.Action(func() {
m.FlyTo(maplibre.CameraOptions{
Center: &maplibre.LngLat{Lng: -122.4194, Lat: 37.7749},
Zoom: &zoom14,
})
})
flyToOak := c.Action(func() {
m.FlyTo(maplibre.CameraOptions{
Center: &maplibre.LngLat{Lng: -122.2711, Lat: 37.8044},
Zoom: &zoom14,
})
})
c.View(func() h.H {
return h.Div(
h.Div(
h.Attr("style", "max-width:960px;margin:0 auto;padding:1rem;font-family:sans-serif"),
h.H1(h.Text("MapLibre GL Example")),
m.Element(
click.Input(handleClick.OnInput()),
h.Input(h.Type("hidden"), pinLng.Bind(), handlePinDrag.OnInput()),
),
h.Div(h.Attr("style", "margin-top:1rem;display:flex;gap:0.5rem;flex-wrap:wrap"),
h.Button(h.Text("Fly to San Francisco"), flyToSF.OnClick()),
h.Button(h.Text("Fly to Oakland"), flyToOak.OnClick()),
),
h.Div(h.Attr("style", "margin-top:0.5rem;font-size:0.9rem"),
h.P(h.Text("Zoom: "), m.Zoom.Text()),
h.P(h.Text("Center: "), m.CenterLng.Text(), h.Text(", "), m.CenterLat.Text()),
h.P(h.Text("Click: "), clickLng.Text(), h.Text(", "), clickLat.Text()),
h.P(h.Text("Vehicle: "), vehicleLng.Text(), h.Text(", "), vehicleLat.Text()),
h.P(h.Text("Draggable Pin: "), pinLng.Text(), h.Text(", "), pinLat.Text()),
),
),
)
})
})
v.Start()
}