108 lines
2.0 KiB
Go
108 lines
2.0 KiB
Go
// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package main
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import (
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"encoding/json"
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"fmt"
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"io/ioutil"
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"log"
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"os"
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"reflect"
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)
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type database struct {
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list *list
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types map[string]item
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}
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func (db *database) save() error {
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data, err := json.MarshalIndent(db, "", "\t")
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if err != nil {
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log.Fatalln(err)
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}
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return ioutil.WriteFile("database.json", data, os.ModePerm)
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}
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func (db *database) load() error {
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data, err := ioutil.ReadFile("database.json")
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if err != nil {
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return err
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}
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if err = json.Unmarshal(data, db); err != nil {
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return err
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}
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return nil
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}
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func (db *database) MarshalJSON() ([]byte, error) {
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type encodable struct {
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Category string
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Item item
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}
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var e []encodable
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for _, it := range *db.list {
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// TypeOf -> finds the dynamic type of "it"
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// Elem -> returns the element type of the pointer
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// Name -> returns the type name as string
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cat := reflect.TypeOf(it).Elem().Name()
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e = append(e, encodable{cat, it})
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}
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return json.Marshal(e)
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}
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func (db *database) UnmarshalJSON(data []byte) error {
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var decodables []struct {
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Category string
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Item json.RawMessage
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}
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if err := json.Unmarshal(data, &decodables); err != nil {
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return err
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}
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for _, d := range decodables {
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it, err := db.newItem(d.Category)
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if err != nil {
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return err
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}
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if err := json.Unmarshal(d.Item, &it); err != nil {
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return err
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}
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*db.list = append(*db.list, it)
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}
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return nil
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}
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func (db *database) register(category string, t item) {
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if db.types == nil {
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db.types = make(map[string]item)
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}
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db.types[category] = t
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}
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func (db *database) newItem(category string) (item, error) {
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it, ok := db.types[category]
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if !ok {
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return nil, fmt.Errorf("register %q within database before decoding", category)
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}
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t := reflect.TypeOf(it).Elem()
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v := reflect.New(t)
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return v.Interface().(item), nil
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}
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