From ff27adbde5bbdb166a99c9c60e6ac5df3c2232dd Mon Sep 17 00:00:00 2001
From: Onur Cinar <onur.cinar@gmail.com>
Date: Thu, 22 Aug 2024 06:59:07 -0700
Subject: [PATCH] Config rules.

---
 checker2.go      | 117 +++++++++++++++++++++++++++++++++++++++++++++++
 checker2_test.go |  41 +++++++++++++++++
 2 files changed, 158 insertions(+)
 create mode 100644 checker2.go
 create mode 100644 checker2_test.go

diff --git a/checker2.go b/checker2.go
new file mode 100644
index 0000000..b20a6a4
--- /dev/null
+++ b/checker2.go
@@ -0,0 +1,117 @@
+package checker
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+type Rule struct {
+	FieldIndex []int
+	Checkers   []CheckFunc
+}
+
+// rulesRegistry stores a collection of rules associated with a specific type.
+var rulesRegistry = map[reflect.Type][]*Rule{}
+
+// checkersCache stores checkers associated with a specific config.
+var checkersCache = map[string]CheckFunc{}
+
+// RegisterRulesFromConfig registers rules based on the provided struct type and config map.
+func RegisterRulesFromConfig(structType reflect.Type, nameToConfig map[string]string) error {
+	rules := make([]*Rule, len(nameToConfig))
+
+	for name, config := range nameToConfig {
+		field, ok := structType.FieldByName(name)
+		if !ok {
+			return fmt.Errorf("field %s not found", name)
+		}
+
+		checkers, err := initCheckersFromConfig(config)
+		if err != nil {
+			return fmt.Errorf("field %s has errors: %w", name, err)
+		}
+
+		rules = append(rules, &Rule{
+			FieldIndex: field.Index,
+			Checkers:   checkers,
+		})
+	}
+
+	rulesRegistry[structType] = rules
+
+	return nil
+}
+
+// RegisterRulesFromTag registers rules based on the provided struct type and field tags.
+func RegisterRulesFromTag(structType reflect.Type) error {
+	structTypes := []reflect.Type{structType}
+
+	for len(structTypes) > 0 {
+		structType := structTypes[0]
+		structTypes = structTypes[1:]
+
+		// Skip already registed structs
+		_, found := rulesRegistry[structType]
+		if found {
+			continue
+		}
+
+		var rules []*Rule
+
+		for i := range structType.NumField() {
+			field := structType.Field(i)
+
+			// Queue the nested structs
+			if field.Type.Kind() == reflect.Struct {
+				structTypes = append(structTypes, field.Type)
+				continue
+			}
+
+			config := field.Tag.Get("checkers")
+			if config == "" {
+				continue
+			}
+
+			checkers, err := initCheckersFromConfig(config)
+			if err != nil {
+				return fmt.Errorf("field %s has errors: %w", field.Name, err)
+			}
+
+			rules = append(rules, &Rule{
+				FieldIndex: field.Index,
+				Checkers:   checkers,
+			})
+		}
+
+		rulesRegistry[structType] = rules
+	}
+
+	return nil
+}
+
+// initCheckersFromConfig parses the given config string and initializes checker instances.
+func initCheckersFromConfig(config string) ([]CheckFunc, error) {
+	items := strings.Fields(config)
+	checkers := make([]CheckFunc, len(items))
+
+	for i, item := range items {
+		checker, ok := checkersCache[item]
+		if ok {
+			checkers[i] = checker
+			continue
+		}
+
+		name, params, _ := strings.Cut(item, ":")
+
+		maker, ok := makers[name]
+		if !ok {
+			return nil, fmt.Errorf("checker %s not found", name)
+		}
+
+		checkers[i] = maker(params)
+		checkersCache[item] = checkers[i]
+	}
+
+	return checkers, nil
+}
diff --git a/checker2_test.go b/checker2_test.go
new file mode 100644
index 0000000..5e8ffcc
--- /dev/null
+++ b/checker2_test.go
@@ -0,0 +1,41 @@
+package checker_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/cinar/checker"
+)
+
+func TestRegisterRulesFromConfig(t *testing.T) {
+	type Person struct {
+		Name  string
+		Email string
+	}
+
+	err := checker.RegisterRulesFromConfig(reflect.TypeFor[Person](), map[string]string{
+		"Name":  "trim required",
+		"Email": "required email",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestRegisterRulesFromTag(t *testing.T) {
+	type Address struct {
+		Street string `checkers:"required"`
+	}
+
+	type Person struct {
+		Name  string `checkers:"trim required"`
+		Email string `checkers:"required email"`
+		Home  Address
+		Work  Address
+	}
+
+	err := checker.RegisterRulesFromTag(reflect.TypeFor[Person]())
+	if err != nil {
+		t.Fatal(err)
+	}
+}