From 311baef9e4339b672983d2f06d846c9797a6223a Mon Sep 17 00:00:00 2001
From: Inanc Gumus <m@inanc.io>
Date: Tue, 3 Sep 2019 23:15:46 +0300
Subject: [PATCH] add: timestamp to reflection decoder

---
 interfaces/11-reflection-decoder/_decoder.go  | 60 +++++++++++++++
 .../11-reflection-decoder/_decoder_reader.go  | 36 +++++++++
 interfaces/11-reflection-decoder/_main.go     | 42 ++++++++++
 .../11-reflection-decoder/_main_reader.go     | 30 ++++++++
 interfaces/11-reflection-decoder/book.go      | 38 +--------
 .../11-reflection-decoder/database.json       |  6 +-
 interfaces/11-reflection-decoder/decoder.go   | 14 ++++
 interfaces/11-reflection-decoder/list.go      | 11 ++-
 interfaces/11-reflection-decoder/main.go      | 18 +++++
 interfaces/11-reflection-decoder/product.go   |  4 +-
 interfaces/11-reflection-decoder/timestamp.go | 77 +++++++++++++++++++
 11 files changed, 294 insertions(+), 42 deletions(-)
 create mode 100644 interfaces/11-reflection-decoder/_decoder.go
 create mode 100644 interfaces/11-reflection-decoder/_decoder_reader.go
 create mode 100644 interfaces/11-reflection-decoder/_main.go
 create mode 100644 interfaces/11-reflection-decoder/_main_reader.go
 create mode 100644 interfaces/11-reflection-decoder/timestamp.go

diff --git a/interfaces/11-reflection-decoder/_decoder.go b/interfaces/11-reflection-decoder/_decoder.go
new file mode 100644
index 0000000..75f7669
--- /dev/null
+++ b/interfaces/11-reflection-decoder/_decoder.go
@@ -0,0 +1,60 @@
+// 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"
+	"reflect"
+)
+
+type decoder map[string]interface{}
+
+type schema struct {
+	Category string
+	Item     json.RawMessage
+}
+
+func (d decoder) decode(data []byte) (list, error) {
+	var schemas []schema
+
+	if err := json.Unmarshal(data, &schemas); err != nil {
+		return nil, err
+	}
+
+	return d.products(schemas)
+}
+
+func (d decoder) products(ss []schema) (list, error) {
+	var store list
+
+	for _, s := range ss {
+		prod, err := d.product(s.Category, s.Item)
+
+		if err != nil {
+			return nil, err
+		}
+
+		store = append(store, prod)
+	}
+
+	return store, nil
+}
+
+func (d decoder) product(kind string, data []byte) (item, error) {
+	p := d.newProduct(kind)
+
+	err := json.Unmarshal(data, p)
+
+	return p, err
+}
+
+func (d decoder) newProduct(kind string) item {
+	t := reflect.TypeOf(d[kind])
+	v := reflect.New(t)
+	return v.Interface().(item)
+}
diff --git a/interfaces/11-reflection-decoder/_decoder_reader.go b/interfaces/11-reflection-decoder/_decoder_reader.go
new file mode 100644
index 0000000..b9104f1
--- /dev/null
+++ b/interfaces/11-reflection-decoder/_decoder_reader.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 (
+	"io"
+	"io/ioutil"
+	"os"
+)
+
+func (d decoder) fromFile(path string) (list, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+
+	return d.readFile(f)
+}
+
+func (d decoder) readFile(f *os.File) (list, error) {
+	return d.read(f)
+}
+
+func (d decoder) read(r io.Reader) (list, error) {
+	data, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+
+	return d.decode(data)
+}
diff --git a/interfaces/11-reflection-decoder/_main.go b/interfaces/11-reflection-decoder/_main.go
new file mode 100644
index 0000000..9679ed2
--- /dev/null
+++ b/interfaces/11-reflection-decoder/_main.go
@@ -0,0 +1,42 @@
+// 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"
+	"io/ioutil"
+	"log"
+	"os"
+)
+
+func main() {
+	dec := make(decoder)
+	dec["book"] = book{}
+	dec["game"] = game{}
+	dec["puzzle"] = puzzle{}
+	dec["toy"] = toy{}
+
+	data, err := ioutil.ReadAll(os.Stdin)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	store, err := dec.decode(data)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	fmt.Print(store)
+
+	// store.discount(.5)
+	// fmt.Print(store)
+
+	// ----
+	// data, err := save(store)
+	// fmt.Println(string(data), err)
+}
diff --git a/interfaces/11-reflection-decoder/_main_reader.go b/interfaces/11-reflection-decoder/_main_reader.go
new file mode 100644
index 0000000..9dc25be
--- /dev/null
+++ b/interfaces/11-reflection-decoder/_main_reader.go
@@ -0,0 +1,30 @@
+// 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"
+	"log"
+	"os"
+)
+
+func main() {
+	dec := decoder{
+		"book":   book{},
+		"game":   game{},
+		"puzzle": puzzle{},
+		"toy":    toy{},
+	}
+
+	store, err := dec.read(os.Stdin)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	fmt.Print(store)
+}
diff --git a/interfaces/11-reflection-decoder/book.go b/interfaces/11-reflection-decoder/book.go
index 3e24559..c36372f 100644
--- a/interfaces/11-reflection-decoder/book.go
+++ b/interfaces/11-reflection-decoder/book.go
@@ -8,46 +8,14 @@
 package main
 
 import (
-	"encoding/json"
 	"fmt"
-	"strconv"
-	"time"
 )
 
 type book struct {
 	product
-	Published interface{}
+	Published timestamp
 }
 
-func (b book) String() string {
-	p := format(b.Published)
-	return fmt.Sprintf("%s - (%v)", &b.product, p)
-}
-
-func (b *book) MarshalJSON() ([]byte, error) {
-	type jbook book
-
-	jb := (*jbook)(b)
-	jb.Published = format(b.Published)
-
-	return json.Marshal(jb)
-}
-
-func format(v interface{}) string {
-	var t int
-
-	switch v := v.(type) {
-	case int:
-		t = v
-	case string:
-		t, _ = strconv.Atoi(v)
-	default:
-		return "unknown"
-	}
-
-	// Mon Jan 2 15:04:05 -0700 MST 2006
-	const layout = "2006/01"
-
-	u := time.Unix(int64(t), 0)
-	return u.Format(layout)
+func (b *book) String() string {
+	return fmt.Sprintf("%s - (%s)", &b.product, b.Published)
 }
diff --git a/interfaces/11-reflection-decoder/database.json b/interfaces/11-reflection-decoder/database.json
index 92e780c..5caa227 100644
--- a/interfaces/11-reflection-decoder/database.json
+++ b/interfaces/11-reflection-decoder/database.json
@@ -4,7 +4,7 @@
 		"Item": {
 			"Title": "moby dick",
 			"Price": 10,
-			"Published": "1973/10"
+			"Published": 118281600
 		}
 	},
 	{
@@ -12,7 +12,7 @@
 		"Item": {
 			"Title": "odyssey",
 			"Price": 15,
-			"Published": "1993/04"
+			"Published": 733622400
 		}
 	},
 	{
@@ -20,7 +20,7 @@
 		"Item": {
 			"Title": "hobbit",
 			"Price": 25,
-			"Published": "unknown"
+			"Published": -62135596800
 		}
 	},
 	{
diff --git a/interfaces/11-reflection-decoder/decoder.go b/interfaces/11-reflection-decoder/decoder.go
index c1ea908..feb7fe4 100644
--- a/interfaces/11-reflection-decoder/decoder.go
+++ b/interfaces/11-reflection-decoder/decoder.go
@@ -61,3 +61,17 @@ func newProduct(category string) item {
 	}
 	return nil
 }
+
+// func (d decoder) newProduct(category string) item {
+// 	t := reflect.TypeOf(d[category])
+// 	v := reflect.New(t)
+// 	return v.Interface().(item)
+// }
+
+// func toProduct(kind string, data []byte) (item, error) {
+// 	p := newProduct(kind)
+
+// 	err := json.Unmarshal(data, p)
+
+// 	return p, err
+// }
diff --git a/interfaces/11-reflection-decoder/list.go b/interfaces/11-reflection-decoder/list.go
index 0a7dede..3d644a3 100644
--- a/interfaces/11-reflection-decoder/list.go
+++ b/interfaces/11-reflection-decoder/list.go
@@ -19,9 +19,15 @@ type item interface {
 	fmt.Stringer
 }
 
+// schema adds an additional category field
+// to the product types.
 type schema struct {
+	// Category is the product category field.
 	Category string
-	Item     item
+
+	// Item is an interface value.
+	// Here, we are embedding an interface value.
+	Item item
 }
 
 type list []item
@@ -30,6 +36,9 @@ func (l list) MarshalJSON() ([]byte, error) {
 	var schemas []schema
 
 	for _, it := range l {
+		// TypeOf -> finds the dynamic type of "it"
+		// Elem   -> returns the element type of the pointer
+		// Name   -> returns the type name as string
 		cat := reflect.TypeOf(it).Elem().Name()
 		schemas = append(schemas, schema{cat, it})
 	}
diff --git a/interfaces/11-reflection-decoder/main.go b/interfaces/11-reflection-decoder/main.go
index 30b76f4..fefd0a1 100644
--- a/interfaces/11-reflection-decoder/main.go
+++ b/interfaces/11-reflection-decoder/main.go
@@ -14,6 +14,23 @@ import (
 )
 
 func main() {
+	// store := list{
+	// 	&book{product{"moby dick", 10}, toTimestamp(118281600)},
+	// 	&book{product{"odyssey", 15}, toTimestamp("733622400")},
+	// 	&book{product{"hobbit", 25}, unknown},
+	// 	&puzzle{product{"rubik's cube", 5}},
+	// 	&game{product{"minecraft", 20}},
+	// 	&game{product{"tetris", 5}},
+	// 	&toy{product{"yoda", 150}},
+	// }
+
+	// out, err := json.MarshalIndent(store, "", "\t")
+	// if err != nil {
+	// 	log.Fatalln(err)
+	// }
+
+	// fmt.Println(string(out))
+
 	data, err := ioutil.ReadFile("database.json")
 	if err != nil {
 		log.Fatalln(err)
@@ -25,6 +42,7 @@ func main() {
 	}
 
 	fmt.Print(store)
+
 	// for _, p := range store {
 	// 	fmt.Printf("%#v\n", p)
 	// }
diff --git a/interfaces/11-reflection-decoder/product.go b/interfaces/11-reflection-decoder/product.go
index 2fd584d..f93cb84 100644
--- a/interfaces/11-reflection-decoder/product.go
+++ b/interfaces/11-reflection-decoder/product.go
@@ -7,9 +7,7 @@
 
 package main
 
-import (
-	"fmt"
-)
+import "fmt"
 
 type product struct {
 	Title string
diff --git a/interfaces/11-reflection-decoder/timestamp.go b/interfaces/11-reflection-decoder/timestamp.go
new file mode 100644
index 0000000..dad84a2
--- /dev/null
+++ b/interfaces/11-reflection-decoder/timestamp.go
@@ -0,0 +1,77 @@
+// 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"
+)
+
+// Mon Jan 2 15:04:05 -0700 MST 2006
+const layout = "2006/01"
+
+// unknown is the zero value of a timestamp.
+var unknown = timestamp(time.Time{})
+
+// timestamp prints timestamps, it's a stringer.
+// It is useful even if it's zero.
+type timestamp time.Time
+
+// 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) {
+	u := time.Time(ts).Unix()
+	return strconv.AppendInt(out, u, 10), nil
+}
+
+// UnmarshalJSON is an implementation of the json.Unmarshaler interface.
+// json.Unmarshal and json.Decode call this method.
+func (ts *timestamp) UnmarshalJSON(data []byte) error {
+	s := string(data)
+
+	// Let the ParseInt parse quoted strings.
+	us, err := strconv.Unquote(s)
+	if err == nil {
+		s = us
+	}
+
+	// Always overwrite the timestamp when decoding.
+	*ts = unknown
+
+	// Handle the numeric case.
+	if n, err := strconv.ParseInt(s, 10, 64); err == nil {
+		*ts = timestamp(time.Unix(n, 0))
+	}
+
+	return nil
+}
+
+func (ts timestamp) String() string {
+	t := time.Time(ts)
+
+	if t.IsZero() {
+		return "unknown"
+	}
+
+	return t.Format(layout)
+}
+
+func toTimestamp(v interface{}) timestamp {
+	var t int
+
+	switch v := v.(type) {
+	case int:
+		t = v
+	case string:
+		t, _ = strconv.Atoi(v)
+	default:
+		return unknown
+	}
+
+	return timestamp(time.Unix(int64(t), 0))
+}