server/obstacle.go

package server

import (
	"encoding/json"
	"math"
	"math/rand"

	v "hackerbots.us/vector"
)

// Obstacle is the implementation of the generic building type in the game.
type Obstacle struct {
	Bounds v.AABB2d `json:"bounds"`
	Hp     int      `json:"-"`
}

func (o *Obstacle) MarshalJSON() ([]byte, error) {
	payload := [4]float64{
		o.Bounds.A.X,
		o.Bounds.A.Y,

		o.Bounds.B.X,
		o.Bounds.B.Y,
	}
	return json.Marshal(payload)
}

func (o *Obstacle) UnmarshalJSON(incoming []byte) error {
	payload := [4]float64{}
	err := json.Unmarshal(incoming, &payload)
	if err != nil {
		return err
	}
	o.Bounds = v.AABB2d{
		A: v.Point2d{X: payload[0], Y: payload[1]},
		B: v.Point2d{X: payload[2], Y: payload[3]},
	}
	return nil
}

func (o Obstacle) distance_from_point(p v.Point2d) float64 {
	dist := math.MaxFloat32

	dist = math.Min(dist, float64(p.Sub(o.Bounds.A).Mag()))
	dist = math.Min(dist, float64(p.Sub(o.Bounds.B).Mag()))
	dist = math.Min(dist, float64(p.Sub(v.Point2d{X: o.Bounds.A.X, Y: o.Bounds.B.Y}).Mag()))
	dist = math.Min(dist, float64(p.Sub(v.Point2d{X: o.Bounds.B.X, Y: o.Bounds.A.Y}).Mag()))

	return dist
}

func obstacleFromValues(x, y, w, h float64, hp int) (o Obstacle) {
	return Obstacle{
		Bounds: v.AABB2d{
			A: v.Point2d{X: x, Y: y},
			B: v.Point2d{X: x + w, Y: y + h},
		},
		Hp: hp,
	}
}

// GenerateObstacles returns a slice of (count) obstacles within a region
// bounded by width, height.
func GenerateObstacles(count int, width, height float64) []Obstacle {
	out := []Obstacle{}

	// Create obstacles that cover the edges of the world, so we don't need to
	// special case collision at the edges
	// left wall
	out = append(out, obstacleFromValues(0, 5, 5, height-10, 0))
	// // right wall
	out = append(out, obstacleFromValues(width-5, 5, 5, height-10, 0))
	// // top wall
	out = append(out, obstacleFromValues(0, height-5, width, 5, 0))
	// bottom wall
	out = append(out, obstacleFromValues(0, 0, width, 5, 0))

	// Now create N random objects somewhere in the world
	for i := 0; i < count; i++ {
		x := rand.Float64() * (width - (width / 10))
		y := rand.Float64() * (height - (height / 10))
		w := rand.Float64()*(width/10) + 20
		h := rand.Float64()*(height/10) + 20
		out = append(
			out,
			obstacleFromValues(x, y, w, h, 10000))
	}
	return out
}