package i18n

import (
	"encoding/json"
	"regexp"
	"strings"
)

// Lang represents a loaded language.
type Lang struct {
	Code    string `json:"code"`
	Name    string `json:"name"`
	langMap map[string]string
}

// I18nLang is a simple i18n library that translates strings using a language map.
// It mimicks some functionality of the vue-i18n library so that the same JSON
// language map may be used in the JS frontent and the Go backend.
type I18nLang struct {
	Code    string `json:"code"`
	Name    string `json:"name"`
	langMap map[string]string
}

var reParam = regexp.MustCompile(`(?i)\{([a-z0-9-.]+)\}`)

// New returns an I18n instance.
func New(code string, b []byte) (*I18nLang, error) {
	var l map[string]string
	if err := json.Unmarshal(b, &l); err != nil {
		return nil, err
	}
	return &I18nLang{
		langMap: l,
	}, nil
}

// JSON returns the languagemap as raw JSON.
func (i *I18nLang) JSON() []byte {
	b, _ := json.Marshal(i.langMap)
	return b
}

// T returns the translation for the given key similar to vue i18n's t().
func (i *I18nLang) T(key string) string {
	s, ok := i.langMap[key]
	if !ok {
		return key
	}

	return i.getSingular(s)
}

// Ts returns the translation for the given key similar to vue i18n's t()
// and subsitutes the params in the given map in the translated value.
// In the language values, the substitutions are represented as: {key}
func (i *I18nLang) Ts(key string, params map[string]string) string {
	s, ok := i.langMap[key]
	if !ok {
		return key
	}

	s = i.getSingular(s)
	for p, val := range params {

		// If there are {params} in the map values, substitute them.
		val = i.subAllParams(val)

		s = strings.ReplaceAll(s, `{`+p+`}`, val)
	}

	return s
}

// Ts2 returns the translation for the given key similar to vue i18n's t()
// and subsitutes the params in the given map in the translated value.
// In the language values, the substitutions are represented as: {key}
// The params and values are received as a pairs of succeeding strings.
// That is, the number of these arguments should be an even number.
// eg: Ts2("globals.message.notFound",
//         "name", "campaigns",
//         "error", err)
func (i *I18nLang) Ts2(key string, params ...string) string {
	if len(params)%2 != 0 {
		return key + `: Invalid arguments`
	}

	s, ok := i.langMap[key]
	if !ok {
		return key
	}

	s = i.getSingular(s)
	for n := 0; n < len(params); n += 2 {
		// If there are {params} in the param values, substitute them.
		val := i.subAllParams(params[n+1])
		s = strings.ReplaceAll(s, `{`+params[n]+`}`, val)
	}

	return s
}

// Tc returns the translation for the given key similar to vue i18n's tc().
// It expects the language string in the map to be of the form `Singular | Plural` and
// returns `Plural` if n > 1, or `Singular` otherwise.
func (i *I18nLang) Tc(key string, n int) string {
	s, ok := i.langMap[key]
	if !ok {
		return key
	}

	// Plural.
	if n > 1 {
		return i.getPlural(s)
	}

	return i.getSingular(s)
}

// getSingular returns the singular term from the vuei18n pipe separated value.
// singular term | plural term
func (i *I18nLang) getSingular(s string) string {
	if !strings.Contains(s, "|") {
		return s
	}

	return strings.TrimSpace(strings.Split(s, "|")[0])
}

// getSingular returns the plural term from the vuei18n pipe separated value.
// singular term | plural term
func (i *I18nLang) getPlural(s string) string {
	if !strings.Contains(s, "|") {
		return s
	}

	chunks := strings.Split(s, "|")
	if len(chunks) == 2 {
		return strings.TrimSpace(chunks[1])
	}

	return strings.TrimSpace(chunks[0])
}

// subAllParams recursively resolves and replaces all {params} in a string.
func (i *I18nLang) subAllParams(s string) string {
	if !strings.Contains(s, `{`) {
		return s
	}

	parts := reParam.FindAllStringSubmatch(s, -1)
	if len(parts) < 1 {
		return s
	}

	for _, p := range parts {
		s = strings.ReplaceAll(s, p[0], i.T(p[1]))
	}

	return i.subAllParams(s)
}