add: more exercises to funcs

25-functions/exercises/README.md

@@ -6,4 +6,12 @@
 
 2. **[Refactor the Game Store to Funcs - Step #2](https://github.com/inancgumus/learngo/tree/master/25-functions/exercises/refactor-to-funcs-2)**
 
-    Let's continue the refactoring from the previous exercise. This time, you're going to refactor the command handling logic.
+    Let's continue the refactoring from the previous exercise. This time, you're going to refactor the command handling logic.
+
+3. **[Refactor the Game Store to Funcs - Step #3](https://github.com/inancgumus/learngo/tree/master/25-functions/exercises/refactor-to-funcs-3)**
+
+    Let's continue from the previous exercise. This time, you're going to add json encoding and decoding using funcs.
+
+4. **[Rewrite the Log Parser program using funcs](https://github.com/inancgumus/learngo/tree/master/25-functions/exercises/rewrite-log-parser-using-funcs)**
+
+  You've watched the lecture. Now, try to rewrite the same log parser program using funcs on your own.

25-functions/exercises/refactor-to-funcs-3/commands.go

@@ -0,0 +1,70 @@
+// 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/
+//
+
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func runCmd(input string, games []game, byID map[int]game) bool {
+	fmt.Println()
+
+	cmd := strings.Fields(input)
+	if len(cmd) == 0 {
+		return true
+	}
+
+	switch cmd[0] {
+	case "quit":
+		return cmdQuit()
+
+	case "list":
+		return cmdList(games)
+
+	case "id":
+		return cmdByID(cmd, games, byID)
+	}
+	return true
+}
+
+func cmdQuit() bool {
+	fmt.Println("bye!")
+	return false
+}
+
+func cmdList(games []game) bool {
+	for _, g := range games {
+		printGame(g)
+	}
+	return true
+}
+
+func cmdByID(cmd []string, games []game, byID map[int]game) bool {
+	if len(cmd) != 2 {
+		fmt.Println("wrong id")
+		return true
+	}
+
+	id, err := strconv.Atoi(cmd[1])
+	if err != nil {
+		fmt.Println("wrong id")
+		return true
+	}
+
+	g, ok := byID[id]
+	if !ok {
+		fmt.Println("sorry. i don't have the game")
+		return true
+	}
+
+	printGame(g)
+
+	return true
+}

25-functions/exercises/refactor-to-funcs-3/games.go

@@ -0,0 +1,74 @@
+// 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/
+//
+
+package main
+
+import "fmt"
+
+const data = `
+[
+        {
+                "id": 1,
+                "name": "god of war",
+                "genre": "action adventure",
+                "price": 50
+        },
+        {
+                "id": 2,
+                "name": "x-com 2",
+                "genre": "strategy",
+                "price": 40
+        },
+        {
+                "id": 3,
+                "name": "minecraft",
+                "genre": "sandbox",
+                "price": 20
+        }
+]`
+
+type item struct {
+	id    int
+	name  string
+	price int
+}
+
+type game struct {
+	item
+	genre string
+}
+
+func load() (games []game) {
+	games = addGame(games, newGame(1, 50, "god of war", "action adventure"))
+	games = addGame(games, newGame(2, 40, "x-com 2", "strategy"))
+	games = addGame(games, newGame(3, 20, "minecraft", "sandbox"))
+	return
+}
+
+func addGame(games []game, g game) []game {
+	return append(games, g)
+}
+
+func newGame(id, price int, name, genre string) game {
+	return game{
+		item:  item{id: id, name: name, price: price},
+		genre: genre,
+	}
+}
+
+func indexByID(games []game) (byID map[int]game) {
+	byID = make(map[int]game)
+	for _, g := range games {
+		byID[g.id] = g
+	}
+	return
+}
+
+func printGame(g game) {
+	fmt.Printf("#%d: %-15q %-20s $%d\n",
+		g.id, g.name, "("+g.genre+")", g.price)
+}

25-functions/exercises/refactor-to-funcs-3/main.go

@@ -0,0 +1,61 @@
+// 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: Refactor the game store to funcs - step #3
+//
+//  Let's continue from the previous exercise. This time,
+//  you're going to add json encoding and decoding using
+//  funcs.
+//
+//  1- Create a new command in a func that encodes the
+//     game store data to json and terminates the program.
+//     Lastly, add it to runCmd func.
+//
+//     For more information, see: "Encode" exercise from
+//     the structs section.
+//
+//        Name  : cmdSave
+//        Inputs: []game
+//        Output: bool
+//
+//  2- Refactor the load() to load the games from the
+//     `data` constant (it's in the games.go as well).
+//
+//     For more information, see: "Decode" exercise from
+//     the structs section.
+//
+// ---------------------------------------------------------
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+func main() {
+	games := load()
+	byID := indexByID(games)
+
+	fmt.Printf("Inanc's game store has %d games.\n", len(games))
+
+	in := bufio.NewScanner(os.Stdin)
+	for {
+		fmt.Printf(`
+  > list   : lists all the games
+  > id N   : queries a game by id
+  > quit   : quits
+
+`)
+
+		if !in.Scan() || !runCmd(in.Text(), games, byID) {
+			break
+		}
+	}
+}

25-functions/exercises/refactor-to-funcs-3/solution/commands.go

@@ -0,0 +1,91 @@
+// 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/
+//
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func runCmd(input string, games []game, byID map[int]game) bool {
+	fmt.Println()
+
+	cmd := strings.Fields(input)
+	if len(cmd) == 0 {
+		return true
+	}
+
+	switch cmd[0] {
+	case "quit":
+		return cmdQuit()
+
+	case "list":
+		return cmdList(games)
+
+	case "id":
+		return cmdByID(cmd, games, byID)
+
+	case "save":
+		return cmdSave(games)
+	}
+	return true
+}
+
+func cmdQuit() bool {
+	fmt.Println("bye!")
+	return false
+}
+
+func cmdList(games []game) bool {
+	for _, g := range games {
+		printGame(g)
+	}
+	return true
+}
+
+func cmdByID(cmd []string, games []game, byID map[int]game) bool {
+	if len(cmd) != 2 {
+		fmt.Println("wrong id")
+		return true
+	}
+
+	id, err := strconv.Atoi(cmd[1])
+	if err != nil {
+		fmt.Println("wrong id")
+		return true
+	}
+
+	g, ok := byID[id]
+	if !ok {
+		fmt.Println("sorry. i don't have the game")
+		return true
+	}
+
+	printGame(g)
+
+	return true
+}
+
+func cmdSave(games []game) bool {
+	// load the data into encodable game values
+	var jg []jsonGame
+	for _, g := range games {
+		jg = append(jg, jsonGame{g.id, g.name, g.genre, g.price})
+	}
+
+	out, err := json.MarshalIndent(jg, "", "\t")
+	if err != nil {
+		fmt.Println("sorry, can't save:", err)
+		return true
+	}
+
+	fmt.Println(string(out))
+	return false
+}

25-functions/exercises/refactor-to-funcs-3/solution/games.go

@@ -0,0 +1,93 @@
+// 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/
+//
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+const data = `
+[
+        {
+                "id": 1,
+                "name": "god of war",
+                "genre": "action adventure",
+                "price": 50
+        },
+        {
+                "id": 2,
+                "name": "x-com 2",
+                "genre": "strategy",
+                "price": 40
+        },
+        {
+                "id": 3,
+                "name": "minecraft",
+                "genre": "sandbox",
+                "price": 20
+        }
+]`
+
+type item struct {
+	id    int
+	name  string
+	price int
+}
+
+type game struct {
+	item
+	genre string
+}
+
+// encodable and decodable game type
+type jsonGame struct {
+	ID    int    `json:"id"`
+	Name  string `json:"name"`
+	Genre string `json:"genre"`
+	Price int    `json:"price"`
+}
+
+func load() (games []game) {
+	// load the initial data from json
+	var decoded []jsonGame
+	if err := json.Unmarshal([]byte(data), &decoded); err != nil {
+		fmt.Println("Sorry, there is a problem:", err)
+		return
+	}
+
+	// load the data into usual game values
+	for _, dg := range decoded {
+		games = addGame(games, newGame(dg.ID, dg.Price, dg.Name, dg.Genre))
+	}
+	return games
+}
+
+func addGame(games []game, g game) []game {
+	return append(games, g)
+}
+
+func newGame(id, price int, name, genre string) game {
+	return game{
+		item:  item{id: id, name: name, price: price},
+		genre: genre,
+	}
+}
+
+func indexByID(games []game) (byID map[int]game) {
+	byID = make(map[int]game)
+	for _, g := range games {
+		byID[g.id] = g
+	}
+	return
+}
+
+func printGame(g game) {
+	fmt.Printf("#%d: %-15q %-20s $%d\n",
+		g.id, g.name, "("+g.genre+")", g.price)
+}

25-functions/exercises/refactor-to-funcs-3/solution/main.go

@@ -0,0 +1,36 @@
+// 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/
+//
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+func main() {
+	games := load()
+	byID := indexByID(games)
+
+	fmt.Printf("Inanc's game store has %d games.\n", len(games))
+
+	in := bufio.NewScanner(os.Stdin)
+	for {
+		fmt.Printf(`
+  > list   : lists all the games
+  > id N   : queries a game by id
+  > save   : exports the data to json and quits  
+  > quit   : quits
+
+`)
+
+		if !in.Scan() || !runCmd(in.Text(), games, byID) {
+			break
+		}
+	}
+}

25-functions/exercises/rewrite-log-parser-using-funcs/log.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org 4
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions/exercises/rewrite-log-parser-using-funcs/log_err_missing.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions/exercises/rewrite-log-parser-using-funcs/log_err_negative.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org -100
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions/exercises/rewrite-log-parser-using-funcs/log_err_str.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org FOUR
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

25-functions/exercises/rewrite-log-parser-using-funcs/main.go

@@ -0,0 +1,94 @@
+// 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/
+//
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// result stores the parsed result for a domain
+type result struct {
+	domain string
+	visits int
+	// add more metrics if needed
+}
+
+// parser keep tracks of the parsing
+type parser struct {
+	sum     map[string]result // metrics per domain
+	domains []string          // unique domain names
+	total   int               // total visits for all domains
+	lines   int               // number of parsed lines (for the error messages)
+}
+
+func main() {
+	p := parser{sum: make(map[string]result)}
+
+	// Scan the standard-in line by line
+	in := bufio.NewScanner(os.Stdin)
+	for in.Scan() {
+		p.lines++
+
+		// Parse the fields
+		fields := strings.Fields(in.Text())
+		if len(fields) != 2 {
+			fmt.Printf("wrong input: %v (line #%d)\n", fields, p.lines)
+			return
+		}
+
+		domain := fields[0]
+
+		// Sum the total visits per domain
+		visits, err := strconv.Atoi(fields[1])
+		if visits < 0 || err != nil {
+			fmt.Printf("wrong input: %q (line #%d)\n", fields[1], p.lines)
+			return
+		}
+
+		// Collect the unique domains
+		if _, ok := p.sum[domain]; !ok {
+			p.domains = append(p.domains, domain)
+		}
+
+		// Keep track of total and per domain visits
+		p.total += visits
+
+		// You cannot assign to composite values
+		// p.sum[domain].visits += visits
+
+		// create and assign a new copy of `visit`
+		p.sum[domain] = result{
+			domain: domain,
+			visits: visits + p.sum[domain].visits,
+		}
+	}
+
+	// Print the visits per domain
+	sort.Strings(p.domains)
+
+	fmt.Printf("%-30s %10s\n", "DOMAIN", "VISITS")
+	fmt.Println(strings.Repeat("-", 45))
+
+	for _, domain := range p.domains {
+		parsed := p.sum[domain]
+		fmt.Printf("%-30s %10d\n", domain, parsed.visits)
+	}
+
+	// Print the total visits for all domains
+	fmt.Printf("\n%-30s %10d\n", "TOTAL", p.total)
+
+	// Let's handle the error
+	if err := in.Err(); err != nil {
+		fmt.Println("> Err:", err)
+	}
+}