Detect translations in high-level structs

This patch adds .IsTranslated(), .IsTranslatedN() and related functions
to following objects:
- Po
- Mo
- locale
- gotext
and it creates helper interfaces in introspector.go.

This makes it possible to detect whether a string is translatable or not
during runtime.

Resolves #42

gotext.go

@@ -245,3 +245,57 @@ func GetNDC(dom, str, plural string, n int, ctx string, vars ...interface{}) str
 
 	return tr
 }
+
+// IsTranslated reports whether a string is translated
+func IsTranslated(str string) bool {
+	return IsTranslatedND(GetDomain(), str, 0)
+}
+
+// IsTranslatedN reports whether a plural string is translated
+func IsTranslatedN(str string, n int) bool {
+	return IsTranslatedND(GetDomain(), str, n)
+}
+
+// IsTranslatedD reports whether a domain string is translated
+func IsTranslatedD(dom, str string) bool {
+	return IsTranslatedND(dom, str, 0)
+}
+
+// IsTranslatedND reports whether a plural domain string is translated
+func IsTranslatedND(dom, str string, n int) bool {
+	loadStorage(false)
+
+	globalConfig.RLock()
+	defer globalConfig.RUnlock()
+
+	if _, ok := globalConfig.storage.Domains[dom]; !ok {
+		globalConfig.storage.AddDomain(dom)
+	}
+
+	return globalConfig.storage.IsTranslatedND(dom, str, n)
+}
+
+// IsTranslatedC reports whether a context string is translated
+func IsTranslatedC(str, ctx string) bool {
+	return IsTranslatedNDC(GetDomain(), str, 0, ctx)
+}
+
+// IsTranslatedNC reports whether a plural context string is translated
+func IsTranslatedNC(str string, n int, ctx string) bool {
+	return IsTranslatedNDC(GetDomain(), str, n, ctx)
+}
+
+// IsTranslatedDC reports whether a domain context string is translated
+func IsTranslatedDC(dom, str, ctx string) bool {
+	return IsTranslatedNDC(dom, str, 0, ctx)
+}
+
+// IsTranslatedNDC reports whether a plural domain context string is translated
+func IsTranslatedNDC(dom, str string, n int, ctx string) bool {
+	loadStorage(false)
+
+	globalConfig.RLock()
+	defer globalConfig.RUnlock()
+
+	return globalConfig.storage.IsTranslatedNDC(dom, str, n, ctx)
+}

gotext_test.go

@@ -176,6 +176,33 @@ msgstr "Another text on another domain"
 	if tr != "Another text on another domain" {
 		t.Errorf("Expected 'Another text on another domain' but got '%s'", tr)
 	}
+
+	// Test IsTranslation functions
+	if !IsTranslated("My text") {
+		t.Error("'My text' should be reported as translated.")
+	}
+	if IsTranslated("Another string") {
+		t.Error("'Another string' should be reported as not translated.")
+	}
+	plural := "One with var: %s"
+	if !IsTranslated(plural) {
+		t.Errorf("'%s' should be reported as translated for singular.", plural)
+	}
+	if !IsTranslatedN(plural, 0) {
+		t.Errorf("'%s' should be reported as translated for n=0.", plural)
+	}
+	if !IsTranslatedN(plural, 2) {
+		t.Errorf("'%s' should be reported as translated for n=2.", plural)
+	}
+	if !IsTranslatedC("Some random in a context", "Ctx") {
+		t.Errorf("'Some random in a context' should be reported as translated under context.")
+	}
+	if !IsTranslatedC(plural, "Ctx") {
+		t.Errorf("'%s' should be reported as translated for singular under context.", plural)
+	}
+	if !IsTranslatedNC(plural, 0, "Ctx") {
+		t.Errorf("'%s' should be reported as translated for n=0 under context.", plural)
+	}
 }
 
 func TestUntranslated(t *testing.T) {

introspector.go

@@ -0,0 +1,25 @@
+package gotext
+
+// IsTranslatedIntrospector is able to determine whether a given string is translated.
+// Examples of this introspector are Po and Mo, which are specific to their domain.
+// Locale holds multiple domains and also implements IsTranslatedDomainIntrospector.
+type IsTranslatedIntrospector interface {
+	IsTranslated(str string) bool
+	IsTranslatedN(str string, n int) bool
+	IsTranslatedC(str, ctx string) bool
+	IsTranslatedNC(str string, n int, ctx string) bool
+}
+
+// IsTranslatedDomainIntrospector is able to determine whether a given string is translated.
+// Example of this introspector is Locale, which holds multiple domains.
+// Simpler objects that are domain-specific, like Po or Mo, implement IsTranslatedIntrospector.
+type IsTranslatedDomainIntrospector interface {
+	IsTranslated(str string) bool
+	IsTranslatedN(str string, n int) bool
+	IsTranslatedD(dom, str string) bool
+	IsTranslatedND(dom, str string, n int) bool
+	IsTranslatedC(str, ctx string) bool
+	IsTranslatedNC(str string, n int, ctx string) bool
+	IsTranslatedDC(dom, str, ctx string) bool
+	IsTranslatedNDC(dom, str string, n int, ctx string) bool
+}

locale.go

@@ -311,6 +311,66 @@ func (l *Locale) GetTranslations() map[string]*Translation {
 	return all
 }
 
+// IsTranslated reports whether a string is translated
+func (l *Locale) IsTranslated(str string) bool {
+	return l.IsTranslatedND(l.GetDomain(), str, 0)
+}
+
+// IsTranslatedN reports whether a plural string is translated
+func (l *Locale) IsTranslatedN(str string, n int) bool {
+	return l.IsTranslatedND(l.GetDomain(), str, n)
+}
+
+// IsTranslatedD reports whether a domain string is translated
+func (l *Locale) IsTranslatedD(dom, str string) bool {
+	return l.IsTranslatedND(dom, str, 0)
+}
+
+// IsTranslatedND reports whether a plural domain string is translated
+func (l *Locale) IsTranslatedND(dom, str string, n int) bool {
+	l.RLock()
+	defer l.RUnlock()
+
+	if l.Domains == nil {
+		return false
+	}
+	translator, ok := l.Domains[dom]
+	if !ok {
+		return false
+	}
+	return translator.GetDomain().IsTranslatedN(str, n)
+}
+
+// IsTranslatedC reports whether a context string is translated
+func (l *Locale) IsTranslatedC(str, ctx string) bool {
+	return l.IsTranslatedNDC(l.GetDomain(), str, 0, ctx)
+}
+
+// IsTranslatedNC reports whether a plural context string is translated
+func (l *Locale) IsTranslatedNC(str string, n int, ctx string) bool {
+	return l.IsTranslatedNDC(l.GetDomain(), str, n, ctx)
+}
+
+// IsTranslatedDC reports whether a domain context string is translated
+func (l *Locale) IsTranslatedDC(dom, str, ctx string) bool {
+	return l.IsTranslatedNDC(dom, str, 0, ctx)
+}
+
+// IsTranslatedNDC reports whether a plural domain context string is translated
+func (l *Locale) IsTranslatedNDC(dom string, str string, n int, ctx string) bool {
+	l.RLock()
+	defer l.RUnlock()
+
+	if l.Domains == nil {
+		return false
+	}
+	translator, ok := l.Domains[dom]
+	if !ok {
+		return false
+	}
+	return translator.GetDomain().IsTranslatedNC(str, n, ctx)
+}
+
 // LocaleEncoding is used as intermediary storage to encode Locale objects to Gob.
 type LocaleEncoding struct {
 	Path          string

mo.go

@@ -92,6 +92,19 @@ func (mo *Mo) GetNC(str, plural string, n int, ctx string, vars ...interface{})
 	return mo.domain.GetNC(str, plural, n, ctx, vars...)
 }
 
+func (mo *Mo) IsTranslated(str string) bool {
+	return mo.domain.IsTranslated(str)
+}
+func (mo *Mo) IsTranslatedN(str string, n int) bool {
+	return mo.domain.IsTranslatedN(str, n)
+}
+func (mo *Mo) IsTranslatedC(str, ctx string) bool {
+	return mo.domain.IsTranslatedC(str, ctx)
+}
+func (mo *Mo) IsTranslatedNC(str string, n int, ctx string) bool {
+	return mo.domain.IsTranslatedNC(str, n, ctx)
+}
+
 func (mo *Mo) MarshalBinary() ([]byte, error) {
 	return mo.domain.MarshalBinary()
 }

po.go

@@ -114,6 +114,19 @@ func (po *Po) GetNC(str, plural string, n int, ctx string, vars ...interface{})
 	return po.domain.GetNC(str, plural, n, ctx, vars...)
 }
 
+func (po *Po) IsTranslated(str string) bool {
+	return po.domain.IsTranslated(str)
+}
+func (po *Po) IsTranslatedN(str string, n int) bool {
+	return po.domain.IsTranslatedN(str, n)
+}
+func (po *Po) IsTranslatedC(str, ctx string) bool {
+	return po.domain.IsTranslatedC(str, ctx)
+}
+func (po *Po) IsTranslatedNC(str string, n int, ctx string) bool {
+	return po.domain.IsTranslatedNC(str, n, ctx)
+}
+
 func (po *Po) MarshalText() ([]byte, error) {
 	return po.domain.MarshalText()
 }