add snake game

pkg/snake/snake.go

@@ -0,0 +1,165 @@
+package snake
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"time"
+
+	"github.com/samber/lo"
+)
+
+type Position struct {
+	x int
+	y int
+}
+
+type Direction int
+
+const (
+	Up Direction = iota
+	Down
+	Left
+	Right
+)
+
+type CellType int
+
+const (
+	None CellType = iota
+	Snake
+	Food
+)
+
+type State struct {
+	// first element is the head, final element is the tail
+	snakePositions []Position
+	direction      Direction
+	foodPosition   Position
+}
+
+type Game struct {
+	state State
+
+	width  int
+	height int
+	render func(cells [][]CellType, alive bool)
+
+	randIntFn func(int) int
+}
+
+func NewGame(width, height int, render func(cells [][]CellType, dead bool)) *Game {
+	return &Game{
+		width:     width,
+		height:    height,
+		render:    render,
+		randIntFn: rand.Intn,
+	}
+}
+
+func (self *Game) Start(ctx context.Context) {
+	self.initializeState()
+
+	go func() {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-time.After(time.Duration(500/self.getSpeed()) * time.Millisecond):
+				fmt.Println("updating")
+
+				alive := self.tick()
+				self.render(self.getCells(), alive)
+				if !alive {
+					return
+				}
+			}
+		}
+	}()
+}
+
+func (self *Game) initializeState() {
+	centerOfScreen := Position{self.width / 2, self.height / 2}
+
+	self.state = State{
+		snakePositions: []Position{centerOfScreen},
+		direction:      Right,
+	}
+
+	self.state.foodPosition = self.setNewFoodPos()
+}
+
+// assume the player never actually wins, meaning we don't get stuck in a loop
+func (self *Game) setNewFoodPos() Position {
+	for i := 0; i < 1000; i++ {
+		newFoodPos := Position{self.randIntFn(self.width), self.randIntFn(self.height)}
+
+		if !lo.Contains(self.state.snakePositions, newFoodPos) {
+			return newFoodPos
+		}
+	}
+
+	panic("SORRY, BUT I WAS TOO LAZY TO MAKE THE SNAKE GAME SMART ENOUGH TO PUT THE FOOD SOMEWHERE SENSIBLE NO MATTER WHAT, AND I ALSO WAS TOO LAZY TO ADD A WIN CONDITION")
+}
+
+// returns whether the snake is alive
+func (self *Game) tick() bool {
+	newHeadPos := self.state.snakePositions[0]
+
+	switch self.state.direction {
+	case Up:
+		newHeadPos.y--
+	case Down:
+		newHeadPos.y++
+	case Left:
+		newHeadPos.x--
+	case Right:
+		newHeadPos.x++
+	}
+
+	if newHeadPos.x < 0 || newHeadPos.x >= self.width || newHeadPos.y < 0 || newHeadPos.y >= self.height {
+		return false
+	}
+
+	if lo.Contains(self.state.snakePositions, newHeadPos) {
+		return false
+	}
+
+	self.state.snakePositions = append([]Position{newHeadPos}, self.state.snakePositions...)
+
+	if newHeadPos == self.state.foodPosition {
+		self.state.foodPosition = self.setNewFoodPos()
+	} else {
+		self.state.snakePositions = self.state.snakePositions[:len(self.state.snakePositions)-1]
+	}
+
+	return true
+}
+
+func (self *Game) getSpeed() int {
+	return len(self.state.snakePositions)
+}
+
+func (self *Game) getCells() [][]CellType {
+	cells := make([][]CellType, self.height)
+
+	setCell := func(pos Position, value CellType) {
+		cells[pos.y][pos.x] = value
+	}
+
+	for i := 0; i < self.height; i++ {
+		cells[i] = make([]CellType, self.width)
+	}
+
+	for _, pos := range self.state.snakePositions {
+		setCell(pos, Snake)
+	}
+
+	setCell(self.state.foodPosition, Food)
+
+	return cells
+}
+
+func (self *Game) SetDirection(direction Direction) {
+	self.state.direction = direction
+}