Add currency_pattern to language relation

The design calls for rendering all amounts with their currency symbol,
but golang.org/x/text’s currency package always render the symbol in
front, which is wrong in Catalan and Spanish, and a lot of other
languages.

Consulting the Internet, the most popular package for that is
accounting[0], which is almost as useless because they confuse locale
with the currency’s country of origin’s “usual locale” (e.g., en-US for
USD), which is also wrong: in Catalan i need to write USD prices as
"1.234,56 $" regardless of what Americans do.

With accounting i have the recourse of initializing the struct that
holds all the “locale” information, which is also wrong because i have
to define the decimal and thousands separators, something that depends
only on the locale, next to the currency’s precision, that is
locale-independent.  But, since all CLDR data from golang.org/x/text
is inside an internal package, i can not access it and would need to
define all that information myself, which defeats the purpose of using
an external package.

Since for now i only need the format pattern for currency, i just saved
it into the database of available languages, that i do not expect to
grow too much.

[0]: https://github.com/leekchan/accounting

deploy/available_languages.sql

@@ -4,10 +4,10 @@
 
 begin;
 
-insert into public.language (lang_tag, name, endonym, selectable)
+insert into public.language (lang_tag, name, endonym, selectable, currency_pattern)
-values ('und', 'Undefined', 'Undefined', false)
+values ('und', 'Undefined', 'Undefined', false, '%[3]s%.[1]*[2]f')
-     , ('ca', 'Catalan', 'català', true)
+     , ('ca', 'Catalan', 'català', true, '%.[1]*[2]f %[3]s')
-     , ('es', 'Spanish', 'español', true)
+     , ('es', 'Spanish', 'español', true, '%.[1]*[2]f %[3]s')
 ;
 
 commit;

deploy/language.sql

@@ -9,7 +9,8 @@ create table language (
 	lang_tag text primary key check (length(lang_tag) < 36), -- RFC5646 recommends 35 at least
 	name text not null,
 	endonym text not null,
-	selectable boolean not null
+	selectable boolean not null,
+	currency_pattern text not null
 );
 
 grant select on table language to guest;

pkg/locale.go

@@ -12,27 +12,31 @@ const contextLocaleKey = "numerus-locale"
 
 type Locale struct {
 	*gotext.Locale
+	CurrencyPattern string
 	Language        language.Tag
 }
 
-func NewLocale(lang language.Tag) *Locale {
+func NewLocale(lang availableLanguage) *Locale {
 	return &Locale{
-		gotext.NewLocale("locales", lang.String()),
+		gotext.NewLocale("locales", lang.tag.String()),
-		lang,
+		lang.currencyPattern,
+		lang.tag,
 	}
 }
 
 func LocaleSetter(db *Db, next http.Handler) http.Handler {
 	availableLanguages := mustGetAvailableLanguages(db)
-	var matcher = language.NewMatcher(availableLanguages)
 
 	locales := map[language.Tag]*Locale{}
+	var tags []language.Tag
 	for _, lang := range availableLanguages {
 		locale := NewLocale(lang)
 		locale.AddDomain("numerus")
-		locales[lang] = locale
+		locales[lang.tag] = locale
+		tags = append(tags, lang.tag)
 	}
 	defaultLocale := locales[language.Catalan]
+	var matcher = language.NewMatcher(tags)
 
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		var locale *Locale
@@ -70,21 +74,27 @@ func gettext(str string, locale *Locale) string {
 	return locale.Get(str)
 }
 
-func mustGetAvailableLanguages(db *Db) []language.Tag {
+type availableLanguage struct {
-	rows, err := db.Query(context.Background(), "select lang_tag from language where selectable")
+	tag             language.Tag
+	currencyPattern string
+}
+
+func mustGetAvailableLanguages(db *Db) []availableLanguage {
+	rows, err := db.Query(context.Background(), "select lang_tag, currency_pattern from language where selectable")
 	if err != nil {
 		panic(err)
 	}
 	defer rows.Close()
 
-	var langs []language.Tag
+	var langs []availableLanguage
 	for rows.Next() {
 		var langTag string
-		err = rows.Scan(&langTag)
+		var currencyPattern string
+		err = rows.Scan(&langTag, &currencyPattern)
 		if err != nil {
 			panic(err)
 		}
-		langs = append(langs, language.MustParse(langTag))
+		langs = append(langs, availableLanguage{language.MustParse(langTag), currencyPattern})
 	}
 	if rows.Err() != nil {
 		panic(rows.Err())

pkg/template.go

@@ -38,7 +38,7 @@ func mustRenderTemplate(wr io.Writer, r *http.Request, layout string, filename s
 			if err != nil {
 				f = math.NaN()
 			}
-			return p.Sprintf("%.*f", company.DecimalDigits, number.Decimal(f))
+			return p.Sprintf(locale.CurrencyPattern, company.DecimalDigits, number.Decimal(f), company.CurrencySymbol)
 		},
 		"formatDate": func(time time.Time) string {
 			return time.Format("02/01/2006")

test/language.sql

@@ -7,7 +7,7 @@ begin;
 
 set search_path to public;
 
-select plan(23);
+select plan(27);
 
 select has_table('language');
 select has_pk('language');
@@ -37,6 +37,11 @@ select col_type_is('language', 'selectable', 'boolean');
 select col_not_null('language', 'selectable');
 select col_hasnt_default('language', 'selectable');
 
+select has_column('language', 'currency_pattern');
+select col_type_is('language', 'currency_pattern', 'text');
+select col_not_null('language', 'currency_pattern');
+select col_hasnt_default('language', 'currency_pattern');
+
 select *
 from finish();
 

verify/available_languages.sql

@@ -9,20 +9,23 @@ from language
 where lang_tag = 'und'
   and name = 'Undefined'
   and endonym = 'Undefined'
-  and not selectable;
+  and not selectable
+  and currency_pattern = '%[3]s%.[1]*[2]f';
 
 select 1 / count(*)
 from language
 where lang_tag = 'ca'
   and name = 'Catalan'
   and endonym = 'català'
-  and selectable;
+  and selectable
+  and currency_pattern = '%.[1]*[2]f %[3]s';
 
 select 1 / count(*)
 from language
 where lang_tag = 'es'
   and name = 'Spanish'
   and endonym = 'español'
-  and selectable;
+  and selectable
+  and currency_pattern = '%.[1]*[2]f %[3]s';
 
 rollback;

verify/language.sql

@@ -6,6 +6,7 @@ select lang_tag
      , name
      , endonym
      , selectable
+     , currency_pattern
 from public.language
 where false;
 

web/template/invoices/products.gohtml

@@ -49,7 +49,7 @@
                         <tr>
                             <td><input type="checkbox" name="id" id="new-product-id-{{$key}}" value="{{.Id}}"></td>
                             <td><label for="new-product-id-{{$key}}">{{ .Name }}</label></td>
-                            <td>{{ .Price | formatPrice }}</td>
+                            <td class="numeric">{{ .Price | formatPrice }}</td>
                         </tr>
                     {{- end }}
                 {{ else }}

web/template/products/index.gohtml

@@ -29,7 +29,7 @@
                 <tr>
                     <td></td>
                     <td><a href="{{ companyURI "/products/"}}{{ .Slug }}">{{ .Name }}</a></td>
-                    <td>{{ .Price | formatPrice }}</td>
+                    <td class="numeric">{{ .Price | formatPrice }}</td>
                 </tr>
             {{- end }}
         {{ else }}