Maker and Init Checkers functions are added. (#5)

* Maker function.

* Make required is added.

* Init checkers is added.

check_required.go

@@ -2,9 +2,16 @@ package checker
 
 import "reflect"
 
+// ResultRequired indicates that the required value is missing.
 const ResultRequired Result = "REQUIRED"
 
-func checkRequired(value reflect.Value) Result {
+// makeRequired makes a checker function for required.
+func makeRequired(_ string) CheckFunc {
+	return checkRequired
+}
+
+// checkRequired checks if the required value is provided.
+func checkRequired(value, _ reflect.Value) Result {
 	if value.IsZero() {
 		return ResultRequired
 	}

check_required_test.go

@@ -8,7 +8,7 @@ import (
 func TestCheckRequiredValidString(t *testing.T) {
 	s := "valid"
 
-	if checkRequired(reflect.ValueOf(s)) != ResultValid {
+	if checkRequired(reflect.ValueOf(s), reflect.ValueOf(nil)) != ResultValid {
 		t.Fail()
 	}
 }
@@ -16,7 +16,7 @@ func TestCheckRequiredValidString(t *testing.T) {
 func TestCheckRequiredUninitializedString(t *testing.T) {
 	var s string
 
-	if checkRequired(reflect.ValueOf(s)) != ResultRequired {
+	if checkRequired(reflect.ValueOf(s), reflect.ValueOf(nil)) != ResultRequired {
 		t.Fail()
 	}
 }
@@ -24,7 +24,7 @@ func TestCheckRequiredUninitializedString(t *testing.T) {
 func TestCheckRequiredEmptyString(t *testing.T) {
 	s := ""
 
-	if checkRequired(reflect.ValueOf(s)) != ResultRequired {
+	if checkRequired(reflect.ValueOf(s), reflect.ValueOf(nil)) != ResultRequired {
 		t.Fail()
 	}
 }
@@ -32,7 +32,7 @@ func TestCheckRequiredEmptyString(t *testing.T) {
 func TestCheckRequiredUninitializedNumber(t *testing.T) {
 	var n int
 
-	if checkRequired(reflect.ValueOf(n)) != ResultRequired {
+	if checkRequired(reflect.ValueOf(n), reflect.ValueOf(nil)) != ResultRequired {
 		t.Fail()
 	}
 }
@@ -40,7 +40,7 @@ func TestCheckRequiredUninitializedNumber(t *testing.T) {
 func TestCheckRequiredValidSlice(t *testing.T) {
 	s := []int{1}
 
-	if checkRequired(reflect.ValueOf(s)) != ResultValid {
+	if checkRequired(reflect.ValueOf(s), reflect.ValueOf(nil)) != ResultValid {
 		t.Fail()
 	}
 }
@@ -48,7 +48,7 @@ func TestCheckRequiredValidSlice(t *testing.T) {
 func TestCheckRequiredUninitializedSlice(t *testing.T) {
 	var s []int
 
-	if checkRequired(reflect.ValueOf(s)) != ResultRequired {
+	if checkRequired(reflect.ValueOf(s), reflect.ValueOf(nil)) != ResultRequired {
 		t.Fail()
 	}
 }
@@ -56,7 +56,7 @@ func TestCheckRequiredUninitializedSlice(t *testing.T) {
 func TestCheckRequiredEmptySlice(t *testing.T) {
 	s := make([]int, 0)
 
-	if checkRequired(reflect.ValueOf(s)) != ResultRequired {
+	if checkRequired(reflect.ValueOf(s), reflect.ValueOf(nil)) != ResultRequired {
 		t.Fail()
 	}
 }
@@ -64,7 +64,7 @@ func TestCheckRequiredEmptySlice(t *testing.T) {
 func TestCheckRequiredValidArray(t *testing.T) {
 	s := [1]int{1}
 
-	if checkRequired(reflect.ValueOf(s)) != ResultValid {
+	if checkRequired(reflect.ValueOf(s), reflect.ValueOf(nil)) != ResultValid {
 		t.Fail()
 	}
 }
@@ -72,7 +72,7 @@ func TestCheckRequiredValidArray(t *testing.T) {
 func TestCheckRequiredEmptyArray(t *testing.T) {
 	s := [1]int{}
 
-	if checkRequired(reflect.ValueOf(s)) != ResultRequired {
+	if checkRequired(reflect.ValueOf(s), reflect.ValueOf(nil)) != ResultRequired {
 		t.Fail()
 	}
 }
@@ -82,7 +82,7 @@ func TestCheckRequiredValidMap(t *testing.T) {
 		"a": "b",
 	}
 
-	if checkRequired(reflect.ValueOf(m)) != ResultValid {
+	if checkRequired(reflect.ValueOf(m), reflect.ValueOf(nil)) != ResultValid {
 		t.Fail()
 	}
 }
@@ -90,7 +90,7 @@ func TestCheckRequiredValidMap(t *testing.T) {
 func TestCheckRequiredUninitializedMap(t *testing.T) {
 	var m map[string]string
 
-	if checkRequired(reflect.ValueOf(m)) != ResultRequired {
+	if checkRequired(reflect.ValueOf(m), reflect.ValueOf(nil)) != ResultRequired {
 		t.Fail()
 	}
 }
@@ -98,7 +98,17 @@ func TestCheckRequiredUninitializedMap(t *testing.T) {
 func TestCheckRequiredEmptyMap(t *testing.T) {
 	m := map[string]string{}
 
-	if checkRequired(reflect.ValueOf(m)) != ResultRequired {
+	if checkRequired(reflect.ValueOf(m), reflect.ValueOf(nil)) != ResultRequired {
+		t.Fail()
+	}
+}
+
+func TestMakeRequired(t *testing.T) {
+	check := makeRequired("")
+
+	s := "valid"
+
+	if check(reflect.ValueOf(s), reflect.ValueOf(nil)) != ResultValid {
 		t.Fail()
 	}
 }

checker.go

@@ -1,14 +1,55 @@
 // Package checker is a Go library for validating user input through struct tags.
 package checker
 
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
 // Result is a unique textual identifier for the mistake.
 type Result string
 
-// ResultValid result indicates that the user input is valid.
-const ResultValid Result = "VALID"
+// CheckFunc defines the checker function.
+type CheckFunc func(value, parent reflect.Value) Result
+
+// MakeFunc defines the maker function.
+type MakeFunc func(params string) CheckFunc
 
 // Mistake provides the field where the mistake was made and a result for the mistake.
 type Mistake struct {
 	Field  string
 	Result Result
 }
+
+// ResultValid result indicates that the user input is valid.
+const ResultValid Result = "VALID"
+
+// makers provdes mapping to maker function for the checkers.
+var makers = map[string]MakeFunc{
+	"required": makeRequired,
+}
+
+// Register registers the given checker name and the maker function.
+func Register(name string, maker MakeFunc) {
+	makers[name] = maker
+}
+
+// initCheckers initializes the checkers provided in the config.
+func initCheckers(config string) []CheckFunc {
+	fields := strings.Fields(config)
+	checkers := make([]CheckFunc, len(fields))
+
+	for i, field := range fields {
+		name, params, _ := strings.Cut(field, ":")
+
+		maker, ok := makers[name]
+		if !ok {
+			panic(fmt.Sprintf("checker %s is unkown", name))
+		}
+
+		checkers[i] = maker(params)
+	}
+
+	return checkers
+}

checker_test.go

@@ -0,0 +1,52 @@
+package checker
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestInitCheckersUnknown(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fail()
+		}
+	}()
+
+	initCheckers("unknown")
+}
+
+func TestInitCheckersKnwon(t *testing.T) {
+	checkers := initCheckers("required")
+
+	if len(checkers) != 1 {
+		t.Fail()
+	}
+
+	if reflect.ValueOf(checkers[0]).Pointer() != reflect.ValueOf(checkRequired).Pointer() {
+		t.Fail()
+	}
+}
+
+func TestRegister(t *testing.T) {
+	var checker CheckFunc = func(_, _ reflect.Value) Result {
+		return ResultValid
+	}
+
+	var maker MakeFunc = func(_ string) CheckFunc {
+		return checker
+	}
+
+	name := "test"
+
+	Register(name, maker)
+
+	checkers := initCheckers(name)
+
+	if len(checkers) != 1 {
+		t.Fail()
+	}
+
+	if reflect.ValueOf(checkers[0]).Pointer() != reflect.ValueOf(checker).Pointer() {
+		t.Fail()
+	}
+}