92 lines
1.7 KiB
Go
92 lines
1.7 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"
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"io/ioutil"
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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 // the registry of the types
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}
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// load the list by decoding the data from any data source.
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func (db *database) load(r io.Reader) error {
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// ReadAll reads from `r` entirely into memory.
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// `data` contains the entire data in memory.
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data, err := ioutil.ReadAll(r)
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if err != nil {
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return err
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}
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return json.Unmarshal(data, db)
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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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Type 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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t := reflect.TypeOf(it).Elem().Name()
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e = append(e, encodable{t, 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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Type 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.Item, d.Type)
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if 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) newItem(data []byte, typ string) (item, error) {
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it, ok := db.types[typ]
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if !ok {
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return nil, fmt.Errorf("newItem: type (%q) does not exist", typ)
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}
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t := reflect.TypeOf(it)
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e := t.Elem()
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v := reflect.New(e)
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it = v.Interface().(item)
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return it, json.Unmarshal(data, &it)
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}
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func (db *database) register(typ string, it 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[typ] = it
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}
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