package dto

import (
	"encoding/json"
	"fmt"
	"strconv"
)

// ID accepts legacy JSON integers and decimal strings. Its wire representation
// is always a string so a browser can round-trip all uint64 values exactly.
type ID uint64

func (id ID) MarshalJSON() ([]byte, error) {
	return json.Marshal(strconv.FormatUint(uint64(id), 10))
}

func (id *ID) UnmarshalJSON(raw []byte) error {
	text := string(raw)
	if len(raw) > 0 && raw[0] == '"' {
		if err := json.Unmarshal(raw, &text); err != nil {
			return err
		}
	}
	if text == "" {
		return fmt.Errorf("ID must be a decimal integer")
	}
	for _, digit := range text {
		if digit < '0' || digit > '9' {
			return fmt.Errorf("ID must be a decimal integer")
		}
	}
	value, err := strconv.ParseUint(text, 10, 64)
	if err != nil {
		return fmt.Errorf("ID is outside the uint64 range")
	}
	*id = ID(value)
	return nil
}