entity_enemy.go

package main

import (
	"math/rand"
	"time"

	"github.com/gdamore/tcell/v2"
)

var enemyFrames = []rune{
	'\u25F4',
	'\u25F5',
	'\u25F6',
	'\u25F7',
}

type Enemy struct {
	Class
	Position
	Velocity
	Sprite
	Delay
	animationDelay Delay
}

// Draw returns the current animation frame but also increments
// the frame for the next draw call
func (e *Enemy) Draw() rune {
	if e.animationDelay.Tick() {
		e.frame++
		if e.frame > len(e.frames)-1 {
			e.frame = 0
		}
	}

	return e.frames[e.frame]
}

// Move checks for an entity in what would be our Enemy's occupying
// cell post-movement. If the cell-to-be-occupied has no occupying
// entity, update the Enemy's position based on movement vectors.
func (e *Enemy) Move() {
	e.SetPosition(e.x+e.vx, e.y+e.vy)
}

// HasVelocity overrides Velocity.HasVelocity to randomize
// movement direction and speed (time between movement intervals)
func (e *Enemy) HasVelocity() bool {
	if !e.Tick() {
		return false
	}

	e.SetRandomVelocity()
	return true
}

// NewEnemy returns a new Enemy
func NewEnemy(x, y int) *Enemy {
	delay := time.Duration(rand.Intn(501)+250) * time.Millisecond
	animationDelay := time.Duration(rand.Intn(250)+250) * time.Millisecond
	return &Enemy{
		Class: NewEnemyClass(),
		Delay: Delay{
			ticker: *time.NewTicker(delay),
		},
		Position: Position{
			x: x,
			y: y,
		},
		Velocity: Velocity{
			vx: 0,
			vy: 0,
		},
		Sprite: Sprite{
			frames: enemyFrames,
			frame:  0,
			color:  tcell.ColorRed,
		},
		animationDelay: Delay{
			ticker: *time.NewTicker(animationDelay),
		},
	}
}