refactor: common ifaces

interfaces/12-marshaler/database.json

@@ -0,0 +1,17 @@
+[
+	{
+		"title": "moby dick",
+		"price": 10,
+		"released": 118281600
+	},
+	{
+		"title": "odyssey",
+		"price": 15,
+		"released": 733622400
+	},
+	{
+		"title": "hobbit",
+		"price": 25,
+		"released": -62135596800
+	}
+]

interfaces/12-marshaler/json.go

@@ -0,0 +1,29 @@
+// 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"
+)
+
+func encode() ([]byte, error) {
+	l := list{
+		{Title: "moby dick", Price: 10, Released: toTimestamp(118281600)},
+		{Title: "odyssey", Price: 15, Released: toTimestamp("733622400")},
+		{Title: "hobbit", Price: 25},
+	}
+
+	return json.MarshalIndent(l, "", "\t")
+}
+
+func decode(data []byte) (l list, err error) {
+	if err := json.Unmarshal(data, &l); err != nil {
+		return nil, err
+	}
+	return l, nil
+}

interfaces/12-marshaler/list.go

@@ -0,0 +1,49 @@
+// 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"
+	"sort"
+	"strings"
+)
+
+type list []*product
+
+func (l list) String() string {
+	if len(l) == 0 {
+		return "Sorry. We're waiting for delivery 🚚.\n"
+	}
+
+	sort.Sort(l)
+	var str strings.Builder
+	for _, p := range l {
+		fmt.Fprintf(&str, "* %s\n", p)
+	}
+	return str.String()
+}
+
+func (l list) discount(ratio float64) {
+	for _, p := range l {
+		p.discount(ratio)
+	}
+}
+
+// by default `list` sorts by `Title`.
+func (l list) Len() int           { return len(l) }
+func (l list) Swap(i, j int)      { l[i], l[j] = l[j], l[i] }
+func (l list) Less(i, j int) bool { return l[i].Title < l[j].Title }
+
+// byRelease sorts by product release dates.
+type byRelease struct {
+	list
+}
+
+func (bp byRelease) Less(i, j int) bool {
+	return bp.list[i].Released.Before(bp.list[j].Released.Time)
+}

interfaces/12-marshaler/main.go

@@ -0,0 +1,21 @@
+// 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"
+)
+
+func main() {
+	// removed error handling for brevity (normally you shouldn't do this).
+	out, _ := encode()
+	fmt.Println(string(out))
+
+	l, _ := decode(out)
+	fmt.Print(l)
+}

interfaces/12-marshaler/money.go

@@ -0,0 +1,16 @@
+// 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"
+
+type money float64
+
+func (m money) String() string {
+	return fmt.Sprintf("$%.2f", m)
+}

interfaces/12-marshaler/product.go

@@ -0,0 +1,26 @@
+// 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"
+)
+
+type product struct {
+	Title    string    `json:"title"`
+	Price    money     `json:"price"`
+	Released timestamp `json:"released,omitempty"`
+}
+
+func (p *product) String() string {
+	return fmt.Sprintf("%s: %s (%s)", p.Title, p.Price, p.Released)
+}
+
+func (p *product) discount(ratio float64) {
+	p.Price *= money(1 - ratio)
+}

interfaces/12-marshaler/timestamp.go

@@ -0,0 +1,57 @@
+// 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 (
+	"strconv"
+	"time"
+)
+
+type timestamp struct {
+	time.Time
+}
+
+func (ts timestamp) String() string {
+	if ts.IsZero() {
+		return "unknown"
+	}
+
+	// Mon Jan 2 15:04:05 -0700 MST 2006
+	const layout = "2006/01"
+	return ts.Format(layout)
+}
+
+// timestamp knows how to decode itself from json.
+// UnmarshalJSON is an implementation of the json.Unmarshaler interface.
+// json.Unmarshal and json.Decode call this method.
+func (ts *timestamp) UnmarshalJSON(data []byte) error {
+	*ts = toTimestamp(string(data))
+	return nil
+}
+
+// timestamp knows how to encode itself to json.
+// MarshalJSON is an implementation of the json.Marshaler interface.
+// json.Marshal and json.Encode call this method.
+func (ts timestamp) MarshalJSON() (out []byte, err error) {
+	// return ts.Time.MarshalJSON()
+	return strconv.AppendInt(out, ts.Unix(), 10), nil
+}
+
+func toTimestamp(v interface{}) (ts timestamp) {
+	var t int
+
+	switch v := v.(type) {
+	case int:
+		t = v
+	case string:
+		t, _ = strconv.Atoi(v)
+	}
+
+	ts.Time = time.Unix(int64(t), 0)
+	return ts
+}