server/projectile.go

package main

import (
	v "bitbucket.org/hackerbots/vector"
	"log"
)

type Projectile struct {
	Id       string    `json:"id"`
	Position v.Point2d `json:"position"`
	MoveTo   v.Point2d `json:"-"`
	Radius   int       `json:"-"`
	Speed    float32   `json:"-"`
	Damage   int       `json:"-"`
	Owner    *Robot    `json:"-"`
}

func (p *Projectile) Tick(g *game) {
	vec := p.MoveTo.Sub(p.Position)
	v_norm := vec.Normalize()
	v_scaled := v_norm.Scale(p.Speed * delta)
	newPos := p.Position.Add(v_scaled)

	hit_player := false
	for player := range g.players {
		for _, r := range player.Robots {
			if &r == p.Owner {
				continue
			}

			player_rect := v.RectFromPoint(r.Position, 3)
			collision, _, _ := v.RectIntersection(player_rect, p.Position, v_scaled)
			if collision {
				hit_player = true

				if r.Health > 0 {
					// Direct hit causes more damage
					log.Printf("Direct Hit %v, Dmg:%v", r.Id, p.Damage)

					r.Health -= p.Damage
					r.Hit = true
				}
			}
		}
	}

	// Are we going to intersect the destination zone in this tick?
	r_dest := v.RectFromPoint(p.MoveTo, 3.0)

	travel := newPos.Sub(p.Position)
	arrived, _, pos := v.RectIntersection(r_dest, p.Position, travel)

	if !arrived {
		for _, obj := range g.obstacles {
			collision, _, pos := v.RectIntersection(obj.Bounds, p.Position, travel)
			if collision {
				arrived = true
				p.Position = pos
			}
		}
	} else {
		p.Position = pos
	}

	if arrived || hit_player {
		delete(g.projectiles, p)

		// Spawn a splosion
		splo := &Splosion{
			Id:       p.Id,
			Position: p.Position,
			Radius:   p.Radius,
			Lifespan: 8,
		}
		g.splosions[splo] = true

		for player := range g.players {
			for _, r := range player.Robots {
				dist := v.Distance(r.Position, p.Position)
				if dist < float32(p.Radius) {
					if r.Health > 0 {
						r.Health -= p.Damage
						r.Hit = true
					}
				}
			}
		}
	} else {
		p.Position.X = newPos.X
		p.Position.Y = newPos.Y
	}
}