blob: 2a5f0062a457a9d132a7ddfe06d4e99af078b723 [file] [log] [blame]
// +build ignore,OMIT
package main
import (
"encoding/json"
"fmt"
"log"
"strings"
)
type romanNumeral int
var numerals = []struct {
s string
v int
}{
{"M", 1000}, {"CM", 900},
{"D", 500}, {"CD", 400},
{"C", 100}, {"XC", 90},
{"L", 50}, {"XL", 40},
{"X", 10}, {"IX", 9},
{"V", 5}, {"IV", 4},
{"I", 1},
}
func (n romanNumeral) String() string {
res := ""
v := int(n)
for _, num := range numerals {
res += strings.Repeat(num.s, v/num.v)
v %= num.v
}
return res
}
func parseRomanNumeral(s string) (romanNumeral, error) {
res := 0
for _, num := range numerals {
for strings.HasPrefix(s, num.s) {
res += num.v
s = s[len(num.s):]
}
}
return romanNumeral(res), nil
}
func (n romanNumeral) MarshalJSON() ([]byte, error) {
if n <= 0 {
return nil, fmt.Errorf("Romans had only natural (=>1) numbers")
}
return json.Marshal(n.String())
}
func (n *romanNumeral) UnmarshalJSON(data []byte) error {
var s string
if err := json.Unmarshal(data, &s); err != nil {
return err
}
p, err := parseRomanNumeral(s)
if err == nil {
*n = p
}
return err
}
type Movie struct {
Title string
Year romanNumeral
}
func main() {
// Encoding
movies := []Movie{{"E.T.", 1982}, {"The Matrix", 1999}, {"Casablanca", 1942}}
res, err := json.MarshalIndent(movies, "", "\t") // HL
if err != nil {
log.Fatal(err)
}
fmt.Printf("Movies: %s\n", res)
// Decoding
var m Movie
inputText := `{"Title": "Alien", "Year":"MCMLXXIX"}`
if err := json.NewDecoder(strings.NewReader(inputText)).Decode(&m); err != nil {
log.Fatal(err)
}
fmt.Printf("%s was released in %d\n", m.Title, m.Year)
}