conf/value.go

package conf

import (
	"errors"
	"net/url"
	"strconv"
	"strings"
)

var (
	ErrCouldNotConvert = errors.New("conf: could not cast one or more values to required type")
)

const (
	separatorSlice = ","
	separatorMap   = ":"
)

type Value string

// Map tries to interpret value as "key: value" pairs
// separated by comma like in the following string:
// "key1: value1, key2: value2, key3: value3".
func (v Value) Map() (Map, error) {
	split := tidySplit(v, separatorSlice)

	m := make(Map, len(split))

	for i := range split {
		k, v, ok := toKV(split[i], separatorMap)
		if !ok {
			return nil, ErrCouldNotConvert
		}

		m[k] = Value(v)
	}

	return m, nil
}

// String returns Value as string
func (v Value) String() string {
	return string(v)
}

// Int converts Value to int. Returned error
// will be non nil if convesion failed.
func (v Value) Int() (int, error) {
	return parseValue(v, strconv.Atoi) // Atoi in fact checks int size, no need to use ParseInt
}

// IntSlice splits Value (separator is ",") and adds
// each of resulting values to []int if possible.
// Returns nil and non-nil error on first failure to convert.
func (v Value) IntSlice() ([]int, error) {
	return parseSlice(v, strconv.Atoi)
}

// Float64 converts Value to float64. Returned error
// will be non nil if convesion failed.
func (v Value) Float64() (float64, error) {
	return parseValue(v, parseFloat64)
}

// Float64Slice splits Value (separator is ",") and adds
// each of resulting values to []float64 if possible.
// Returns nil and non-nil error on first failure to convert.
func (v Value) Float64Slice() ([]float64, error) {
	return parseSlice(v, parseFloat64)
}

// StringSlice splits Value (separator is ",") and adds
// each of resulting values to []string trimming leading and trailing spaces
// from each string.
func (v Value) StringSlice() []string {
	return tidySplit(v, separatorSlice)
}

// Bool tries to interpret Value as bool
// "1", "t", "T", true", "True", "TRUE" yields true
// "0", "f", "F, "false", "False", "FALSE" yields false
// If nothing matches will return false and conf.ErrCouldNotConvert.
func (v Value) Bool() (bool, error) {
	return parseValue(v, strconv.ParseBool)
}

// URL tries to interpret value as url.URL
func (v Value) URL() (*url.URL, error) {
	return parseValue(v, url.Parse)
}

func parseSlice[T any, S ~string](s S, f func(string) (T, error)) ([]T, error) {
	split := tidySplit(s, separatorSlice)

	list := make([]T, 0, len(split))
	for _, str := range split {
		v, err := parseValue(str, f)
		if err != nil {
			return nil, err
		}

		list = append(list, v)
	}

	return list, nil
}

func parseValue[T any, S ~string](s S, f func(string) (T, error)) (T, error) {
	v, err := f(string(s))
	if err != nil {
		return v, errors.Join(ErrCouldNotConvert, err)
	}

	return v, err
}

func tidySplit[S ~string](s S, sep string) []string {
	splitted := strings.Split(string(s), sep)
	for i, str := range splitted {
		splitted[i] = trim(str)
	}
	return splitted
}

func parseFloat64(s string) (float64, error) {
	return strconv.ParseFloat(s, 64)
}