appearblock.go

// Copyright 2021 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package trigger

import (
	"github.com/divVerent/aaaaxy/internal/engine"
	"github.com/divVerent/aaaaxy/internal/game/constants"
	"github.com/divVerent/aaaaxy/internal/game/interfaces"
	"github.com/divVerent/aaaaxy/internal/image"
	"github.com/divVerent/aaaaxy/internal/level"
)

// AppearBlock is a simple entity type that renders a static sprite. It can be optionally solid and/or opaque.
type AppearBlock struct {
	World  *engine.World
	Entity *engine.Entity

	AnimFrame int
}

var count int = 0

const (
	AppearFrames         = 16
	AppearXDistance      = 2 * level.TileSize
	AppearYDistance      = level.TileSize / 4
	AppearSolidThreshold = 12
)

func (a *AppearBlock) Spawn(w *engine.World, sp *level.SpawnableProps, e *engine.Entity) error {
	a.World = w
	a.Entity = e

	var err error
	e.Image, err = image.Load("sprites", "appearblock.png")
	if err != nil {
		return err
	}
	e.Alpha = 0.0
	w.SetZIndex(e, constants.AppearBlockZ)

	return nil
}

func (a *AppearBlock) Despawn() {}

func (a *AppearBlock) Update() {
	delta := a.Entity.Rect.Delta(a.World.Player.Rect)
	actualDistance := delta.Mul2(AppearYDistance, AppearXDistance).Norm0()
	maxDistance := AppearXDistance * AppearYDistance
	wantFrame := 0
	if actualDistance <= maxDistance && delta.Dot(a.World.Player.Impl.(interfaces.Physics).ReadOnGroundVec()) > 0 {
		wantFrame = AppearFrames * (maxDistance - actualDistance) / maxDistance
	}
	if a.AnimFrame < wantFrame {
		a.AnimFrame++
	} else if a.AnimFrame > wantFrame {
		a.AnimFrame--
	}
	a.Entity.Alpha = float64(a.AnimFrame) / AppearFrames
	a.World.MutateContentsBool(a.Entity, level.PlayerSolidContents, a.AnimFrame >= AppearSolidThreshold)
}

func (a *AppearBlock) Touch(other *engine.Entity) {}

func init() {
	engine.RegisterEntityType(&AppearBlock{})
}