From 3271dd5e63ad3d36235f453289c937684548d2d5 Mon Sep 17 00:00:00 2001
From: Inanc Gumus <m@inanc.io>
Date: Thu, 14 Mar 2019 20:36:32 +0300
Subject: [PATCH] add: bouncing ball exercise #1

---
 .../exercises/01-width-and-height/main.go     | 173 ++++++++++++++++++
 .../01-width-and-height/solution}/main.go     |  46 +++--
 18-bouncing-ball-project/exercises/README.md  |   6 +
 3 files changed, 210 insertions(+), 15 deletions(-)
 create mode 100644 18-bouncing-ball-project/exercises/01-width-and-height/main.go
 rename 18-bouncing-ball-project/{04-finalize => exercises/01-width-and-height/solution}/main.go (64%)
 create mode 100644 18-bouncing-ball-project/exercises/README.md

diff --git a/18-bouncing-ball-project/exercises/01-width-and-height/main.go b/18-bouncing-ball-project/exercises/01-width-and-height/main.go
new file mode 100644
index 0000000..67a904c
--- /dev/null
+++ b/18-bouncing-ball-project/exercises/01-width-and-height/main.go
@@ -0,0 +1,173 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+// ---------------------------------------------------------
+// EXERCISE: Adjust the width and height automatically
+//
+//  In this exercise, your goal is simple:
+//
+//    Instead of setting the width and height manually,
+//    you need to get the width and height of the terminal
+//    screen from your operating system.
+//
+//    Don't worry, it is easier than it sounds. You just
+//    need to read a few documentation and install a
+//    Go package.
+//
+//  1. Go here: https://godoc.org/golang.org/x/crypto/ssh/terminal
+//
+//  2. Find the function that gives you the width and height
+//     of the terminal.
+//
+//  3. Call that function from your program and get the
+//     width and height.
+//
+//  4. When an error occurs while retrieving the width
+//     and height, report it.
+//
+//  5. Set the width and height of the board.
+//
+//  6. After solving the above steps, update your program
+//     to use my screen package instead. It offers an
+//     easier way to get the width and height of a
+//     terminal.
+//
+//     go get -u https://github.com/inancgumus/screen
+//
+//
+// BONUS
+//
+//  1. When you set the width, you may see that the ball
+//     goes beyond the left and right borders. This happens
+//     because the ball emoji spans to multiple console
+//     columns (or cells). Ordinary characters have a
+//     single column.
+//
+//     1. Get the width of the ball emoji using function
+//        from the following package:
+//
+//        go get -u github.com/mattn/go-runewidth
+//
+//     2. Divide the width using the rune width of the
+//        ball emoji.
+//
+//  2. Your terminal may have borders, so reduce the
+//     height by taking into account the height of
+//     your terminal borders.
+//
+//
+// EXPECTED OUTPUT
+//
+//  When you run the program, the ball should start
+//  animating across the total width and height of your
+//  terminal screen dynamically.
+//
+//  Currently you set width and height manually, so it
+//  wasn't matter whether your terminal was bigger or
+//  smaller, but now it will be!
+//
+//
+// HINT
+//
+//  Please take a look at this if you get stuck.
+//
+//  You need to pass the Standard Out file handler
+//  to the function that returns you the dimensions.
+//
+//  Check out my screen package to find out how I'm
+//  passing the Standard Out file handler.
+//
+//     https://github.com/inancgumus/screen/blob/master/dimensions.go
+//
+// ---------------------------------------------------------
+
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/inancgumus/screen"
+)
+
+func main() {
+	const (
+		width  = 50
+		height = 10
+
+		cellEmpty = ' '
+		cellBall  = '⚾'
+
+		maxFrames = 1200
+		speed     = time.Second / 20
+	)
+
+	var (
+		px, py int    // ball position
+		vx, vy = 1, 1 // velocities
+
+		cell rune // current cell (for caching)
+	)
+
+	// create the board
+	board := make([][]bool, width)
+	for row := range board {
+		board[row] = make([]bool, height)
+	}
+
+	// create a drawing buffer
+	buf := make([]rune, 0, width*height)
+
+	// clear the screen once
+	screen.Clear()
+
+	for i := 0; i < maxFrames; i++ {
+		// calculate the next ball position
+		px += vx
+		py += vy
+
+		// when the ball hits a border reverse its direction
+		if px <= 0 || px >= width-1 {
+			vx *= -1
+		}
+		if py <= 0 || py >= height-1 {
+			vy *= -1
+		}
+
+		// remove the previous ball
+		for y := range board[0] {
+			for x := range board {
+				board[x][y] = false
+			}
+		}
+
+		// put the new ball
+		board[px][py] = true
+
+		// rewind the buffer (allow appending from the beginning)
+		buf = buf[:0]
+
+		// draw the board into the buffer
+		for y := range board[0] {
+			for x := range board {
+				cell = cellEmpty
+				if board[x][y] {
+					cell = cellBall
+				}
+				buf = append(buf, cell, ' ')
+			}
+			buf = append(buf, '\n')
+		}
+
+		// print the buffer
+		screen.MoveTopLeft()
+		fmt.Print(string(buf))
+
+		// slow down the animation
+		time.Sleep(speed)
+	}
+}
diff --git a/18-bouncing-ball-project/04-finalize/main.go b/18-bouncing-ball-project/exercises/01-width-and-height/solution/main.go
similarity index 64%
rename from 18-bouncing-ball-project/04-finalize/main.go
rename to 18-bouncing-ball-project/exercises/01-width-and-height/solution/main.go
index f7a4de4..246c9ba 100644
--- a/18-bouncing-ball-project/04-finalize/main.go
+++ b/18-bouncing-ball-project/exercises/01-width-and-height/solution/main.go
@@ -9,9 +9,13 @@ package main
 
 import (
 	"fmt"
+	"os"
 	"time"
 
+	"github.com/mattn/go-runewidth"
+
 	"github.com/inancgumus/screen"
+	"golang.org/x/crypto/ssh/terminal"
 )
 
 func main() {
@@ -23,19 +27,30 @@ func main() {
 		speed     = time.Second / 20
 	)
 
-	// get the width and height of the terminal dynamically ***
-	width, height := screen.Size()
-	width /= 2 // our emoji is 2 chars wide
-	height--   // for the border
-
 	var (
-		px, py   int    // ball position
-		ppx, ppy int    // previous ball position ***
-		vx, vy   = 1, 1 // velocities
+		px, py int    // ball position
+		vx, vy = 1, 1 // velocities
 
 		cell rune // current cell (for caching)
 	)
 
+	// get the width and height
+	width, height, err := terminal.GetSize(int(os.Stdout.Fd()))
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	// you can get the width and height using the screen package easily:
+	// width, height := screen.Size()
+
+	// get the rune width of the ball emoji
+	ballWidth := runewidth.RuneWidth(cellBall)
+
+	// adjust the width and height
+	width /= ballWidth
+	height-- // there is a 1 pixel border in my terminal
+
 	// create the board
 	board := make([][]bool, width)
 	for row := range board {
@@ -61,15 +76,16 @@ func main() {
 			vy *= -1
 		}
 
-		// check whether the ball goes beyond the borders
-		if !(px >= width || py >= height) {
-			// remove the previous ball and put the new ball
-			board[px][py], board[ppx][ppy] = true, false
-
-			// save the previous positions
-			ppx, ppy = px, py
+		// remove the previous ball
+		for y := range board[0] {
+			for x := range board {
+				board[x][y] = false
+			}
 		}
 
+		// put the new ball
+		board[px][py] = true
+
 		// rewind the buffer (allow appending from the beginning)
 		buf = buf[:0]
 
diff --git a/18-bouncing-ball-project/exercises/README.md b/18-bouncing-ball-project/exercises/README.md
new file mode 100644
index 0000000..4277e08
--- /dev/null
+++ b/18-bouncing-ball-project/exercises/README.md
@@ -0,0 +1,6 @@
+# Exercises
+
+1. **[Adjust the width and height automatically](https://github.com/inancgumus/learngo/tree/master/18-bouncing-ball-project/exercises/01-width-and-height)**
+
+    In this exercise, your goal is getting the width and height of the terminal screen from your operating system (instead of setting the width and height manually).
+