ichigo/engine/game.go
2021-08-30 16:27:12 +10:00

257 lines
6.1 KiB
Go

package engine
import (
"encoding/gob"
"errors"
"fmt"
"io/fs"
"reflect"
"sync"
"github.com/hajimehoshi/ebiten/v2"
)
var _ interface {
Disabler
Hider
Identifier
Updater
Scanner
} = &Game{}
var (
errNilComponent = errors.New("nil component")
errNilParent = errors.New("nil parent")
)
func init() {
gob.Register(&Game{})
}
// Game implements the ebiten methods using a collection of components. One
// component must be the designated root component - usually a scene of some
// kind.
type Game struct {
Disabled
Hidden
ScreenWidth int
ScreenHeight int
Root DrawUpdater // typically a *Scene or SceneRef though
dbmu sync.RWMutex
byID map[string]Identifier // Named components by ID
byAB map[abKey]map[interface{}]struct{} // Ancestor/behaviour index
par map[interface{}]interface{} // par[x] is parent of x
}
type abKey struct {
ancestor string
behaviour reflect.Type
}
// Draw draws the entire thing, with default draw options.
func (g *Game) Draw(screen *ebiten.Image) {
if g.Hidden {
return
}
g.Root.Draw(screen, ebiten.DrawImageOptions{})
}
// Layout returns the configured screen width/height.
func (g *Game) Layout(outsideWidth, outsideHeight int) (w, h int) {
return g.ScreenWidth, g.ScreenHeight
}
// Update updates the scene.
func (g *Game) Update() error {
if g.Disabled {
return nil
}
return g.Root.Update()
}
// Ident returns "__GAME__".
func (g *Game) Ident() string { return "__GAME__" }
// Component returns the component with a given ID, or nil if there is none.
// This only returns sensible values for registered components (e.g. after
// LoadAndPrepare).
func (g *Game) Component(id string) Identifier {
g.dbmu.RLock()
defer g.dbmu.RUnlock()
return g.byID[id]
}
// Parent returns the parent of a given component, or nil if there is none.
// This only returns sensible values for registered components (e.g. after
// LoadAndPrepare).
func (g *Game) Parent(c interface{}) interface{} {
g.dbmu.RLock()
defer g.dbmu.RUnlock()
return g.par[c]
}
// Query looks for components having both a given ancestor and implementing
// a given behaviour (see Behaviors in interface.go). This only returns sensible
// values after LoadAndPrepare. Note that every component is its own ancestor.
func (g *Game) Query(ancestorID string, behaviour reflect.Type) map[interface{}]struct{} {
g.dbmu.RLock()
defer g.dbmu.RUnlock()
return g.byAB[abKey{ancestorID, behaviour}]
}
// Scan implements Scanner.
func (g *Game) Scan() []interface{} { return []interface{}{g.Root} }
// Walk calls visit with every component and its parent, reachable from the
// given component via Scan, for as long as visit returns nil. The parent of
// the first component (as passed to visit) will be nil.
func Walk(component interface{}, visit func(component, parent interface{}) error) error {
return walk(component, nil, visit)
}
func walk(component, parent interface{}, visit func(component, parent interface{}) error) error {
if err := visit(component, parent); err != nil {
return err
}
sc, ok := component.(Scanner)
if !ok {
return nil
}
for _, c := range sc.Scan() {
if err := walk(c, component, visit); err != nil {
return err
}
}
return nil
}
// LoadAndPrepare first calls Load on all Loaders. Once loading is complete, it
// builds the component databases and then calls Prepare on every Preparer.
// LoadAndPrepare must be called before any calls to Component or Query.
func (g *Game) LoadAndPrepare(assets fs.FS) error {
// Load all the Loaders.
if err := Walk(g, func(c, _ interface{}) error {
l, ok := c.(Loader)
if !ok {
return nil
}
return l.Load(assets)
}); err != nil {
return err
}
// Build the component databases
g.dbmu.Lock()
g.byID = make(map[string]Identifier)
g.byAB = make(map[abKey]map[interface{}]struct{})
g.par = make(map[interface{}]interface{})
if err := Walk(g, g.register); err != nil {
return err
}
g.dbmu.Unlock()
// Prepare all the Preppers
for p := range g.Query(g.Ident(), PrepperType) {
if err := p.(Prepper).Prepare(g); err != nil {
return err
}
}
return nil
}
// Register registers a component into the component database (as the
// child of a given parent). Passing a nil component or parent is an error.
// Registering multiple components with the same ID is also an error.
func (g *Game) Register(component, parent interface{}) error {
if component == nil {
return errNilComponent
}
if parent == nil && component != g {
return errNilParent
}
g.dbmu.Lock()
defer g.dbmu.Unlock()
return g.register(component, parent)
}
func (g *Game) register(component, parent interface{}) error {
// register in g.par
if parent != nil {
g.par[component] = parent
}
// register in g.byAB
ct := reflect.TypeOf(component)
for _, b := range Behaviours {
if !ct.Implements(b) {
continue
}
// TODO: better than O(len(path)^2) time and memory?
for p := component; p != nil; p = g.par[p] {
i, ok := p.(Identifier)
if !ok {
continue
}
k := abKey{i.Ident(), b}
if g.byAB[k] == nil {
g.byAB[k] = make(map[interface{}]struct{})
}
g.byAB[k][component] = struct{}{}
}
}
// register in g.byID if needed
i, ok := component.(Identifier)
if !ok {
return nil
}
id := i.Ident()
if _, exists := g.byID[id]; exists {
return fmt.Errorf("duplicate id %q", id)
}
g.byID[id] = i
return nil
}
// Unregister removes the component from the component database.
// Passing a nil component has no effect.
func (g *Game) Unregister(component interface{}) {
if component == nil {
return
}
g.dbmu.Lock()
g.unregister(component)
g.dbmu.Unlock()
}
func (g *Game) unregister(component interface{}) {
// unregister from g.byAB, using g.par to trace the path
ct := reflect.TypeOf(component)
for _, b := range Behaviours {
if !ct.Implements(b) {
continue
}
for p := component; p != nil; p = g.par[p] {
i, ok := p.(Identifier)
if !ok {
continue
}
k := abKey{i.Ident(), b}
if g.byAB[k] == nil {
continue
}
delete(g.byAB[k], component)
}
}
// unregister from g.par
delete(g.par, component)
// unregister from g.byID if needed
i, ok := component.(Identifier)
if !ok {
return
}
delete(g.byID, i.Ident())
}