add: io reader writer begins

This commit is contained in:
Inanc Gumus
2019-09-07 23:04:53 +03:00
parent 38db8418d4
commit e462f87c9b
11 changed files with 459 additions and 0 deletions

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// 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 book struct {
product
Published timestamp
}
func (b *book) String() string {
return fmt.Sprintf("%s - (%s)", &b.product, b.Published)
}

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// 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"
"reflect"
)
type database struct {
list *list
types map[string]item // the registry of the types
}
// #v1
// func (db *database) load(path string) error {
// data, err := ioutil.ReadFile(path)
// if err != nil {
// return err
// }
// return json.Unmarshal(data, db)
// }
// #v2
// func (db *database) load(r io.Reader) error {
// data, err := ioutil.ReadAll(r)
// if err != nil {
// return err
// }
// return json.Unmarshal(data, db)
// }
// #v3
// TODO: use decoder
// #v1
// func (db *database) save(path string) error {
// data, err := json.MarshalIndent(db, "", "\t")
// if err != nil {
// return err
// }
// return ioutil.WriteFile(path, data, 0644)
// }
// #v2
// func (db *database) save(w io.Writer) error {
// data, err := json.MarshalIndent(db, "", "\t")
// if err != nil {
// return err
// }
//
// return io.Copy(w, bytes.NewReader(data))
// }
// #v3
// TODO: use encoder
func (db *database) MarshalJSON() ([]byte, error) {
type encodable struct {
Type string
Item item
}
var e []encodable
for _, it := range *db.list {
// TypeOf -> finds the dynamic type of "it"
// Elem -> returns the element type of the pointer
// Name -> returns the type name as string
t := reflect.TypeOf(it).Elem().Name()
e = append(e, encodable{t, it})
}
return json.Marshal(e)
}
func (db *database) UnmarshalJSON(data []byte) error {
var decodables []struct {
Type string
Item json.RawMessage
}
if err := json.Unmarshal(data, &decodables); err != nil {
return err
}
for _, d := range decodables {
it, err := db.newItem(d.Item, d.Type)
if err != nil {
return err
}
*db.list = append(*db.list, it)
}
return nil
}
func (db *database) newItem(data []byte, typ string) (item, error) {
it, ok := db.types[typ]
if !ok {
return nil, fmt.Errorf("newItem: type (%q) does not exist", typ)
}
// get the dynamic type inside "it" like *book, *game, etc..
t := reflect.TypeOf(it)
// get the pointer type's element type like book, game, etc...
e := t.Elem()
// create a new pointer value of the type like new(book), new(game), etc...
v := reflect.New(e)
// get the interface value and cast it to the item type
it = v.Interface().(item)
return it, json.Unmarshal(data, &it)
}
func (db *database) register(typ string, it item) {
if db.types == nil {
db.types = make(map[string]item)
}
db.types[typ] = it
}

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[
{
"Type": "book",
"Item": {
"Title": "moby dick",
"Price": 10,
"Published": 118281600
}
},
{
"Type": "book",
"Item": {
"Title": "odyssey",
"Price": 15,
"Published": 733622400
}
},
{
"Type": "book",
"Item": {
"Title": "hobbit",
"Price": 25,
"Published": -62135596800
}
},
{
"Type": "puzzle",
"Item": {
"Title": "rubik's cube",
"Price": 5
}
},
{
"Type": "game",
"Item": {
"Title": "minecraft",
"Price": 20
}
},
{
"Type": "game",
"Item": {
"Title": "tetris",
"Price": 5
}
},
{
"Type": "toy",
"Item": {
"Title": "yoda",
"Price": 150
}
}
]

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// 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
type game struct {
product
}

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// 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"
"strings"
)
type item interface {
discount(float64)
fmt.Stringer
}
type list []item
func (l list) String() string {
if len(l) == 0 {
return "Sorry. We're waiting for delivery 🚚."
}
var str strings.Builder
for _, it := range l {
str.WriteString(it.String())
str.WriteRune('\n')
}
return str.String()
}
func (l list) discount(ratio float64) {
for _, it := range l {
it.discount(ratio)
}
}

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// 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"
"io/ioutil"
"log"
)
func main() {
data, err := ioutil.ReadFile("database.json")
if err != nil {
log.Fatalln(err)
}
var store list
db := database{list: &store}
db.register("book", new(book))
db.register("book", new(book))
db.register("game", new(game))
db.register("puzzle", new(puzzle))
db.register("toy", new(toy))
if err := json.Unmarshal(data, &db); err != nil {
log.Fatalln(err)
}
fmt.Print(store)
/*
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}},
}
db := database{list: &store}
out, err := json.MarshalIndent(&db, "", "\t")
if err != nil {
log.Fatalln(err)
}
fmt.Println(string(out))
// store.discount(.5)
// fmt.Print(store)
*/
}

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// 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)
}

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// 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
Price money
}
func (p *product) String() string {
return fmt.Sprintf("%-15s: %s", p.Title, p.Price)
}
func (p *product) discount(ratio float64) {
p.Price *= money(1 - ratio)
}

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// 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
type puzzle struct {
product
}

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// 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 from timestamp.
func (ts timestamp) MarshalJSON() (out []byte, err error) {
u := time.Time(ts).Unix()
return strconv.AppendInt(out, u, 10), nil
}
// UnmarshalJSON data to timestamp.
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
}
// String representation of the timestamp.
func (ts timestamp) String() string {
t := time.Time(ts)
if t.IsZero() {
return "unknown"
}
return t.Format(layout)
}
// toTimestamp from an unknown value.
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))
}

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// 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
type toy struct {
product
}