implement middleware compose

README.md

@@ -11,6 +11,8 @@
 
 A lightweight, easy-to-use, and [performant](docs/benchmark_result.md) reverse proxy with a web UI.
 
+_Join our [Discord](https://discord.gg/umReR62nRd) for help and discussions_
+
 ## Table of content
 
 <!-- TOC -->

internal/error/builder.go

@@ -2,6 +2,7 @@ package error
 
 import (
 	"fmt"
+	"strings"
 	"sync"
 )
 
@@ -24,7 +25,6 @@ func NewBuilder(format string, args ...any) Builder {
 func (b Builder) Add(err NestedError) Builder {
 	if err != nil {
 		b.Lock()
-		// TODO: if err severity is higher than b.severity, update b.severity
 		b.errors = append(b.errors, err)
 		b.Unlock()
 	}
@@ -49,6 +49,8 @@ func (b Builder) Addf(format string, args ...any) Builder {
 func (b Builder) Build() NestedError {
 	if len(b.errors) == 0 {
 		return nil
+	} else if len(b.errors) == 1 && !strings.ContainsRune(b.message, ' ') {
+		return b.errors[0].Subject(b.message)
 	}
 	return Join(b.message, b.errors...)
 }

internal/error/error.go

@@ -166,6 +166,8 @@ func (ne NestedError) Subject(s any) NestedError {
 	}
 	if ne.subject == "" {
 		ne.subject = subject
+	} else if !strings.ContainsRune(subject, ' ') || strings.ContainsRune(ne.subject, '.') {
+		ne.subject = fmt.Sprintf("%s.%s", subject, ne.subject)
 	} else {
 		ne.subject = fmt.Sprintf("%s > %s", subject, ne.subject)
 	}

internal/error/errors.go

@@ -6,15 +6,16 @@ import (
 )
 
 var (
-	ErrFailure     = stderrors.New("failed")
-	ErrInvalid     = stderrors.New("invalid")
-	ErrUnsupported = stderrors.New("unsupported")
-	ErrUnexpected  = stderrors.New("unexpected")
-	ErrNotExists   = stderrors.New("does not exist")
-	ErrMissing     = stderrors.New("missing")
-	ErrDuplicated  = stderrors.New("duplicated")
-	ErrOutOfRange  = stderrors.New("out of range")
-	ErrTypeError   = stderrors.New("type error")
+	ErrFailure      = stderrors.New("failed")
+	ErrInvalid      = stderrors.New("invalid")
+	ErrUnsupported  = stderrors.New("unsupported")
+	ErrUnexpected   = stderrors.New("unexpected")
+	ErrNotExists    = stderrors.New("does not exist")
+	ErrMissing      = stderrors.New("missing")
+	ErrDuplicated   = stderrors.New("duplicated")
+	ErrOutOfRange   = stderrors.New("out of range")
+	ErrTypeError    = stderrors.New("type error")
+	ErrTypeMismatch = stderrors.New("type mismatch")
 )
 
 const fmtSubjectWhat = "%w %v: %q"
@@ -63,6 +64,14 @@ func OutOfRange(subject any, value any) NestedError {
 	return errorf("%v %w: %v", subject, ErrOutOfRange, value)
 }
 
-func TypeError(subject any, from, to reflect.Value) NestedError {
-	return errorf("%v %w: %T -> %T", subject, ErrTypeError, from.Interface(), to.Interface())
+func TypeError(subject any, from, to reflect.Type) NestedError {
+	return errorf("%v %w: %s -> %s\n", subject, ErrTypeError, from, to)
+}
+
+func TypeError2(subject any, from, to reflect.Value) NestedError {
+	return TypeError(subject, from.Type(), to.Type())
+}
+
+func TypeMismatch[Expect any](value any) NestedError {
+	return errorf("%w: expect %s got %T", ErrTypeMismatch, reflect.TypeFor[Expect](), value)
 }

internal/net/http/middleware/cloudflare_real_ip.go

@@ -13,6 +13,7 @@ import (
 	"github.com/sirupsen/logrus"
 	"github.com/yusing/go-proxy/internal/common"
 	E "github.com/yusing/go-proxy/internal/error"
+	"github.com/yusing/go-proxy/internal/types"
 )
 
 const (
@@ -53,7 +54,7 @@ func NewCloudflareRealIP(_ OptionsRaw) (*Middleware, E.NestedError) {
 	return cri.m, nil
 }
 
-func tryFetchCFCIDR() (cfCIDRs []*net.IPNet) {
+func tryFetchCFCIDR() (cfCIDRs []*types.CIDR) {
 	if time.Since(cfCIDRsLastUpdate) < cfCIDRsUpdateInterval {
 		return
 	}
@@ -66,14 +67,14 @@ func tryFetchCFCIDR() (cfCIDRs []*net.IPNet) {
 	}
 
 	if common.IsTest {
-		cfCIDRs = []*net.IPNet{
+		cfCIDRs = []*types.CIDR{
 			{IP: net.IPv4(127, 0, 0, 1), Mask: net.IPv4Mask(255, 0, 0, 0)},
 			{IP: net.IPv4(10, 0, 0, 0), Mask: net.IPv4Mask(255, 0, 0, 0)},
 			{IP: net.IPv4(172, 16, 0, 0), Mask: net.IPv4Mask(255, 255, 0, 0)},
 			{IP: net.IPv4(192, 168, 0, 0), Mask: net.IPv4Mask(255, 255, 255, 0)},
 		}
 	} else {
-		cfCIDRs = make([]*net.IPNet, 0, 30)
+		cfCIDRs = make([]*types.CIDR, 0, 30)
 		err := errors.Join(
 			fetchUpdateCFIPRange(cfIPv4CIDRsEndpoint, cfCIDRs),
 			fetchUpdateCFIPRange(cfIPv6CIDRsEndpoint, cfCIDRs),
@@ -90,7 +91,7 @@ func tryFetchCFCIDR() (cfCIDRs []*net.IPNet) {
 	return
 }
 
-func fetchUpdateCFIPRange(endpoint string, cfCIDRs []*net.IPNet) error {
+func fetchUpdateCFIPRange(endpoint string, cfCIDRs []*types.CIDR) error {
 	resp, err := http.Get(endpoint)
 	if err != nil {
 		return err
@@ -110,7 +111,7 @@ func fetchUpdateCFIPRange(endpoint string, cfCIDRs []*net.IPNet) error {
 		if err != nil {
 			return fmt.Errorf("cloudflare responeded an invalid CIDR: %s", line)
 		} else {
-			cfCIDRs = append(cfCIDRs, cidr)
+			cfCIDRs = append(cfCIDRs, (*types.CIDR)(cidr))
 		}
 	}
 

internal/net/http/middleware/middleware.go

@@ -1,6 +1,7 @@
 package middleware
 
 import (
+	"encoding/json"
 	"net/http"
 
 	D "github.com/yusing/go-proxy/internal/docker"
@@ -53,7 +54,14 @@ func (m *Middleware) String() string {
 	return m.name
 }
 
-func (m *Middleware) WithOptionsClone(optsRaw OptionsRaw, rp *ReverseProxy) (*Middleware, E.NestedError) {
+func (m *Middleware) MarshalJSON() ([]byte, error) {
+	return json.MarshalIndent(map[string]any{
+		"name":    m.name,
+		"options": m.impl,
+	}, "", "  ")
+}
+
+func (m *Middleware) WithOptionsClone(optsRaw OptionsRaw) (*Middleware, E.NestedError) {
 	if len(optsRaw) != 0 && m.withOptions != nil {
 		if mWithOpt, err := m.withOptions(optsRaw); err != nil {
 			return nil, err
@@ -87,7 +95,7 @@ func PatchReverseProxy(rp *ReverseProxy, middlewares map[string]OptionsRaw) (res
 			continue
 		}
 
-		m, err := m.WithOptionsClone(opts, rp)
+		m, err := m.WithOptionsClone(opts)
 		if err != nil {
 			invalidOpts.Add(err.Subject(name))
 			continue

internal/net/http/middleware/middleware_builder.go

@@ -8,24 +8,27 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
-func BuildMiddlewaresFromYAML(filePath string) (middlewares map[string]*Middleware, outErr E.NestedError) {
+func BuildMiddlewaresFromComposeFile(filePath string) (map[string]*Middleware, E.NestedError) {
+	fileContent, err := os.ReadFile(filePath)
+	if err != nil {
+		return nil, E.FailWith("read middleware compose file", err)
+	}
+	return BuildMiddlewaresFromYAML(fileContent)
+}
+
+func BuildMiddlewaresFromYAML(data []byte) (middlewares map[string]*Middleware, outErr E.NestedError) {
 	b := E.NewBuilder("middlewares compile errors")
 	defer b.To(&outErr)
 
-	var data map[string][]map[string]any
-	fileContent, err := os.ReadFile(filePath)
-	if err != nil {
-		b.Add(E.FailWith("read file", err))
-		return
-	}
-	err = yaml.Unmarshal(fileContent, &data)
+	var rawMap map[string][]map[string]any
+	err := yaml.Unmarshal(data, &rawMap)
 	if err != nil {
 		b.Add(E.FailWith("toml unmarshal", err))
 		return
 	}
 	middlewares = make(map[string]*Middleware)
-	for name, defs := range data {
-		chainErr := E.NewBuilder("errors in middleware chain %s", name)
+	for name, defs := range rawMap {
+		chainErr := E.NewBuilder(name)
 		chain := make([]*Middleware, 0, len(defs))
 		for i, def := range defs {
 			if def["use"] == nil || def["use"].(string) == "" {
@@ -39,9 +42,9 @@ func BuildMiddlewaresFromYAML(filePath string) (middlewares map[string]*Middlewa
 				continue
 			}
 			delete(def, "use")
-			m, err := base.withOptions(def)
+			m, err := base.WithOptionsClone(def)
 			if err != nil {
-				chainErr.Add(err.Subjectf("%s.%d", name, i))
+				chainErr.Add(err.Subjectf("item%d", i))
 				continue
 			}
 			chain = append(chain, m)

internal/net/http/middleware/middleware_builder_test.go

@@ -1,9 +1,21 @@
 package middleware
 
 import (
+	_ "embed"
+	"encoding/json"
 	"testing"
+
+	E "github.com/yusing/go-proxy/internal/error"
+	. "github.com/yusing/go-proxy/internal/utils/testing"
 )
 
-func TestBuild(t *testing.T) {
+//go:embed test_data/middleware_compose.yml
+var testMiddlewareCompose []byte
 
+func TestBuild(t *testing.T) {
+	// middlewares, err := BuildMiddlewaresFromYAML(testMiddlewareCompose)
+	// ExpectNoError(t, err.Error())
+	data, err := E.Check(json.MarshalIndent(middlewares, "", "  "))
+	ExpectNoError(t, err.Error())
+	t.Log(string(data))
 }

internal/net/http/middleware/middlewares.go

@@ -2,6 +2,7 @@ package middleware
 
 import (
 	"fmt"
+	"net/http"
 	"path"
 	"strings"
 
@@ -15,27 +16,27 @@ import (
 var middlewares map[string]*Middleware
 
 func Get(name string) (middleware *Middleware, ok bool) {
-	middleware, ok = middlewares[name]
+	middleware, ok = middlewares[strings.ToLower(name)]
 	return
 }
 
 // initialize middleware names and label parsers
 func init() {
 	middlewares = map[string]*Middleware{
-		"set_x_forwarded":    SetXForwarded,
-		"hide_x_forwarded":   HideXForwarded,
-		"redirect_http":      RedirectHTTP,
-		"forward_auth":       ForwardAuth.m,
-		"modify_response":    ModifyResponse.m,
-		"modify_request":     ModifyRequest.m,
-		"error_page":         CustomErrorPage,
-		"custom_error_page":  CustomErrorPage,
-		"real_ip":            RealIP.m,
-		"cloudflare_real_ip": CloudflareRealIP.m,
+		"setxforwarded":    SetXForwarded,
+		"hidexforwarded":   HideXForwarded,
+		"redirecthttp":     RedirectHTTP,
+		"forwardauth":      ForwardAuth.m,
+		"modifyresponse":   ModifyResponse.m,
+		"modifyrequest":    ModifyRequest.m,
+		"errorpage":        CustomErrorPage,
+		"customerrorpage":  CustomErrorPage,
+		"realip":           RealIP.m,
+		"cloudflarerealip": CloudflareRealIP.m,
 	}
 	names := make(map[*Middleware][]string)
 	for name, m := range middlewares {
-		names[m] = append(names[m], name)
+		names[m] = append(names[m], http.CanonicalHeaderKey(name))
 		// register middleware name to docker label parsr
 		// in order to parse middleware_name.option=value into correct type
 		if m.labelParserMap != nil {
@@ -49,6 +50,7 @@ func init() {
 			m.name = names[0]
 		}
 	}
+
 	// TODO: seperate from init()
 	b := E.NewBuilder("failed to load middlewares")
 	middlewareDefs, err := U.ListFiles(common.MiddlewareDefsBasePath, 0)
@@ -57,7 +59,7 @@ func init() {
 		return
 	}
 	for _, defFile := range middlewareDefs {
-		mws, err := BuildMiddlewaresFromYAML(defFile)
+		mws, err := BuildMiddlewaresFromComposeFile(defFile)
 		for name, m := range mws {
 			if _, ok := middlewares[name]; ok {
 				b.Add(E.Duplicated("middleware", name))

internal/net/http/middleware/modify_request_test.go

@@ -15,7 +15,7 @@ func TestSetModifyRequest(t *testing.T) {
 	}
 
 	t.Run("set_options", func(t *testing.T) {
-		mr, err := ModifyRequest.m.WithOptionsClone(opts, nil)
+		mr, err := ModifyRequest.m.WithOptionsClone(opts)
 		ExpectNoError(t, err.Error())
 		ExpectDeepEqual(t, mr.impl.(*modifyRequest).SetHeaders, opts["set_headers"].(map[string]string))
 		ExpectDeepEqual(t, mr.impl.(*modifyRequest).AddHeaders, opts["add_headers"].(map[string]string))

internal/net/http/middleware/modify_response_test.go

@@ -15,7 +15,7 @@ func TestSetModifyResponse(t *testing.T) {
 	}
 
 	t.Run("set_options", func(t *testing.T) {
-		mr, err := ModifyResponse.m.WithOptionsClone(opts, nil)
+		mr, err := ModifyResponse.m.WithOptionsClone(opts)
 		ExpectNoError(t, err.Error())
 		ExpectDeepEqual(t, mr.impl.(*modifyResponse).SetHeaders, opts["set_headers"].(map[string]string))
 		ExpectDeepEqual(t, mr.impl.(*modifyResponse).AddHeaders, opts["add_headers"].(map[string]string))

internal/net/http/middleware/real_ip.go

@@ -2,11 +2,11 @@ package middleware
 
 import (
 	"net"
-	"strings"
 
 	"github.com/sirupsen/logrus"
 	D "github.com/yusing/go-proxy/internal/docker"
 	E "github.com/yusing/go-proxy/internal/error"
+	"github.com/yusing/go-proxy/internal/types"
 )
 
 // https://nginx.org/en/docs/http/ngx_http_realip_module.html
@@ -20,7 +20,7 @@ type realIPOpts struct {
 	// Header is the name of the header to use for the real client IP
 	Header string
 	// From is a list of Address / CIDRs to trust
-	From []*net.IPNet
+	From []*types.CIDR
 	/*
 		If recursive search is disabled,
 		the original client address that matches one of the trusted addresses is replaced by
@@ -35,7 +35,7 @@ type realIPOpts struct {
 var RealIP = &realIP{
 	m: &Middleware{
 		labelParserMap: D.ValueParserMap{
-			"from":      CIDRListParser,
+			"from":      D.YamlStringListParser,
 			"recursive": D.BoolParser,
 		},
 		withOptions: NewRealIP,
@@ -45,14 +45,7 @@ var RealIP = &realIP{
 var realIPOptsDefault = func() *realIPOpts {
 	return &realIPOpts{
 		Header: "X-Real-IP",
-		From: []*net.IPNet{
-			{IP: net.IPv4(127, 0, 0, 1), Mask: net.CIDRMask(8, 32)},
-			{IP: net.IPv4(10, 0, 0, 0), Mask: net.CIDRMask(8, 32)},
-			{IP: net.IPv4(172, 16, 0, 0), Mask: net.CIDRMask(12, 32)},
-			{IP: net.IPv4(192, 168, 0, 0), Mask: net.CIDRMask(16, 32)},
-			{IP: net.ParseIP("fc00::"), Mask: net.CIDRMask(7, 128)},
-			{IP: net.ParseIP("fe80::"), Mask: net.CIDRMask(10, 128)},
-		},
+		From:   []*types.CIDR{},
 	}
 }
 
@@ -72,31 +65,6 @@ func NewRealIP(opts OptionsRaw) (*Middleware, E.NestedError) {
 	return riWithOpts.m, nil
 }
 
-func CIDRListParser(s string) (any, E.NestedError) {
-	sl, err := D.YamlStringListParser(s)
-	if err != nil {
-		return nil, err
-	}
-
-	b := E.NewBuilder("invalid CIDR(s)")
-
-	CIDRs := sl.([]string)
-	res := make([]*net.IPNet, 0, len(CIDRs))
-
-	for _, cidr := range CIDRs {
-		if !strings.Contains(cidr, "/") {
-			cidr += "/32" // single IP
-		}
-		_, ipnet, err := net.ParseCIDR(cidr)
-		if err != nil {
-			b.Add(E.Invalid("CIDR", cidr))
-			continue
-		}
-		res = append(res, ipnet)
-	}
-	return res, b.Build()
-}
-
 func (ri *realIP) isInCIDRList(ip net.IP) bool {
 	for _, CIDR := range ri.From {
 		if CIDR.Contains(ip) {

internal/net/http/middleware/real_ip_test.go

@@ -0,0 +1,58 @@
+package middleware
+
+import (
+	"net"
+	"testing"
+
+	"github.com/yusing/go-proxy/internal/types"
+	. "github.com/yusing/go-proxy/internal/utils/testing"
+)
+
+func TestSetRealIP(t *testing.T) {
+	opts := OptionsRaw{
+		"header": "X-Real-IP",
+		"from": []string{
+			"127.0.0.0/8",
+			"192.168.0.0/16",
+			"172.16.0.0/12",
+		},
+		"recursive": true,
+	}
+	optExpected := &realIPOpts{
+		Header: "X-Real-IP",
+		From: []*types.CIDR{
+			{
+				IP:   net.ParseIP("127.0.0.0"),
+				Mask: net.IPv4Mask(255, 0, 0, 0),
+			},
+			{
+				IP:   net.ParseIP("192.168.0.0"),
+				Mask: net.IPv4Mask(255, 255, 0, 0),
+			},
+			{
+				IP:   net.ParseIP("172.16.0.0"),
+				Mask: net.IPv4Mask(255, 240, 0, 0),
+			},
+		},
+		Recursive: true,
+	}
+
+	t.Run("set_options", func(t *testing.T) {
+		ri, err := RealIP.m.WithOptionsClone(opts)
+		ExpectNoError(t, err.Error())
+		// ExpectEqual(t, ri.impl.(*realIP).Header, optExpected.Header)
+		// ExpectDeepEqual(t, ri.impl.(*realIP).From, optExpected.From)
+		// ExpectEqual(t, ri.impl.(*realIP).Recursive, optExpected.Recursive)
+		ExpectDeepEqual(t, ri.impl.(*realIP).realIPOpts, optExpected)
+	})
+
+	// t.Run("request_headers", func(t *testing.T) {
+	// 	result, err := newMiddlewareTest(ModifyRequest.m, &testArgs{
+	// 		middlewareOpt: opts,
+	// 	})
+	// 	ExpectNoError(t, err.Error())
+	// 	ExpectEqual(t, result.RequestHeaders.Get("User-Agent"), "go-proxy/v0.5.0")
+	// 	ExpectTrue(t, slices.Contains(result.RequestHeaders.Values("Accept-Encoding"), "test-value"))
+	// 	ExpectEqual(t, result.RequestHeaders.Get("Accept"), "")
+	// })
+}

internal/net/http/middleware/test_data/middleware_compose.yml

@@ -0,0 +1,41 @@
+theGreatPretender:
+  - use: HideXForwarded
+  - use: ModifyRequest
+    setHeaders:
+      X-Real-IP: 6.6.6.6
+  - use: ModifyResponse
+    hideHeaders:
+      - X-Test3
+      - X-Test4
+
+notAuthenticAuthentik:
+  - use: RedirectHTTP
+  - use: ForwardAuth
+    address: https://authentik.company
+    trustForwardHeader: true
+    addAuthCookiesToResponse:
+      - session_id
+      - user_id
+    authResponseHeaders:
+      - X-Auth-SessionID
+      - X-Auth-UserID
+  - use: CustomErrorPage
+
+realIPAuthentik:
+  - use: RedirectHTTP
+  - use: RealIP
+    header: X-Real-IP
+    from:
+      - "127.0.0.0/8"
+      - "192.168.0.0/16"
+      - "172.16.0.0/12"
+    recursive: true
+  - use: ForwardAuth
+    address: https://authentik.company
+    trustForwardHeader: true
+
+testFakeRealIP:
+  - use: ModifyRequest
+    setHeaders:
+      CF-Connecting-IP: 127.0.0.1
+  - use: CloudflareRealIP

internal/types/cidr.go

@@ -0,0 +1,34 @@
+package types
+
+import (
+	"net"
+	"strings"
+
+	E "github.com/yusing/go-proxy/internal/error"
+)
+
+type CIDR net.IPNet
+
+func (*CIDR) ConvertFrom(val any) (any, E.NestedError) {
+	cidr, ok := val.(string)
+	if !ok {
+		return nil, E.TypeMismatch[string](val)
+	}
+
+	if !strings.Contains(cidr, "/") {
+		cidr += "/32" // single IP
+	}
+	_, ipnet, err := net.ParseCIDR(cidr)
+	if err != nil {
+		return nil, E.Invalid("CIDR", cidr)
+	}
+	return (*CIDR)(ipnet), nil
+}
+
+func (cidr *CIDR) Contains(ip net.IP) bool {
+	return (*net.IPNet)(cidr).Contains(ip)
+}
+
+func (cidr *CIDR) String() string {
+	return (*net.IPNet)(cidr).String()
+}

internal/utils/serialization.go

@@ -12,6 +12,11 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
+type SerializedObject = map[string]any
+type Convertor interface {
+	ConvertFrom(value any) (any, E.NestedError)
+}
+
 func ValidateYaml(schema *jsonschema.Schema, data []byte) E.NestedError {
 	var i any
 
@@ -89,7 +94,7 @@ func Serialize(data any) (SerializedObject, E.NestedError) {
 			} else if field.Anonymous {
 				// If the field is an embedded struct, add its fields to the result
 				fieldMap, err := Serialize(value.Field(i).Interface())
-				if err.HasError() {
+				if err != nil {
 					return nil, err
 				}
 				for k, v := range fieldMap {
@@ -106,90 +111,138 @@ func Serialize(data any) (SerializedObject, E.NestedError) {
 	return result, nil
 }
 
-func Deserialize(src SerializedObject, target any) E.NestedError {
-	if src == nil || target == nil {
+// Deserialize takes a SerializedObject and a target value, and assigns the values in the SerializedObject to the target value.
+// Deserialize ignores case differences between the field names in the SerializedObject and the target.
+//
+// The target value must be a struct or a map[string]any.
+// If the target value is a struct, the SerializedObject will be deserialized into the struct fields.
+// If the target value is a map[string]any, the SerializedObject will be deserialized into the map.
+//
+// The function returns an error if the target value is not a struct or a map[string]any, or if there is an error during deserialization.
+func Deserialize(src SerializedObject, dst any) E.NestedError {
+	if src == nil || dst == nil {
 		return nil
 	}
 
-	tValue := reflect.ValueOf(target)
-	mapping := make(map[string]string)
+	dstV := reflect.ValueOf(dst)
+	dstT := dstV.Type()
 
-	if tValue.Kind() == reflect.Ptr {
-		tValue = tValue.Elem()
+	if dstV.Kind() == reflect.Ptr {
+		dstV = dstV.Elem()
+		dstT = dstV.Type()
 	}
 
 	// convert data fields to lower no-snake
 	// convert target fields to lower no-snake
 	// then check if the field of data is in the target
 
-	if tValue.Kind() == reflect.Struct {
-		t := reflect.TypeOf(target).Elem()
-		for i := 0; i < t.NumField(); i++ {
-			field := t.Field(i)
-			snakeCaseField := ToLowerNoSnake(field.Name)
-			mapping[snakeCaseField] = field.Name
+	// TODO: use E.Builder to collect errors from all fields
+
+	if dstV.Kind() == reflect.Struct {
+		mapping := make(map[string]reflect.Value)
+		for i := 0; i < dstV.NumField(); i++ {
+			field := dstT.Field(i)
+			mapping[ToLowerNoSnake(field.Name)] = dstV.Field(i)
 		}
-	} else if tValue.Kind() == reflect.Map && tValue.Type().Key().Kind() == reflect.String {
-		if tValue.IsNil() {
-			tValue.Set(reflect.MakeMap(tValue.Type()))
+		for k, v := range src {
+			if field, ok := mapping[ToLowerNoSnake(k)]; ok {
+				err := Convert(reflect.ValueOf(v), field)
+				if err != nil {
+					return err.Subject(k)
+				}
+			} else {
+				return E.Unexpected("field", k)
+			}
+		}
+	} else if dstV.Kind() == reflect.Map && dstT.Key().Kind() == reflect.String {
+		if dstV.IsNil() {
+			dstV.Set(reflect.MakeMap(dstT))
 		}
 		for k := range src {
-			// TODO: type check
-			tValue.SetMapIndex(reflect.ValueOf(ToLowerNoSnake(k)), reflect.ValueOf(src[k]))
+			tmp := reflect.New(dstT.Elem()).Elem()
+			err := Convert(reflect.ValueOf(src[k]), tmp)
+			if err != nil {
+				return err.Subject(k)
+			}
+			dstV.SetMapIndex(reflect.ValueOf(ToLowerNoSnake(k)), tmp)
 		}
 		return nil
 	} else {
-		return E.Unsupported("target type", fmt.Sprintf("%T", target))
+		return E.Unsupported("target type", fmt.Sprintf("%T", dst))
 	}
 
-	for k, v := range src {
-		kCleaned := ToLowerNoSnake(k)
-		if fieldName, ok := mapping[kCleaned]; ok {
-			prop := tValue.FieldByName(fieldName)
-			propType := prop.Type()
-			isPtr := prop.Kind() == reflect.Ptr
-			if prop.CanSet() {
-				val := reflect.ValueOf(v)
-				vType := val.Type()
-				switch {
-				case isPtr && vType.ConvertibleTo(propType.Elem()):
-					ptr := reflect.New(propType.Elem())
-					ptr.Elem().Set(val.Convert(propType.Elem()))
-					prop.Set(ptr)
-				case vType.ConvertibleTo(propType):
-					prop.Set(val.Convert(propType))
-				case isPtr:
-					var vSerialized SerializedObject
-					vSerialized, ok = v.(SerializedObject)
-					if !ok {
-						if vType.ConvertibleTo(reflect.TypeFor[SerializedObject]()) {
-							vSerialized = val.Convert(reflect.TypeFor[SerializedObject]()).Interface().(SerializedObject)
-						} else {
-							return E.Failure(fmt.Sprintf("convert %s (%T) to %s", k, v, reflect.TypeFor[SerializedObject]()))
-						}
-					}
-					propNew := reflect.New(propType.Elem())
-					err := Deserialize(vSerialized, propNew.Interface())
-					if err.HasError() {
-						return E.Failure("set field").With(err).Subject(k)
-					}
-					prop.Set(propNew)
-				default:
-					obj, ok := val.Interface().(SerializedObject)
-					if !ok {
-						return E.Invalid("conversion", k).Extraf("from %s to %s", vType, propType)
-					}
-					err := Deserialize(obj, prop.Addr().Interface())
-					if err.HasError() {
-						return E.Failure("set field").With(err).Subject(k)
-					}
-				}
-			} else {
-				return E.Unsupported("field", k).Extraf("type %s is not settable", propType)
-			}
-		} else {
-			return E.Unexpected("field", k)
+	return nil
+}
+
+// Convert attempts to convert the src to dst.
+//
+// If src is a map, it is deserialized into dst.
+// If src is a slice, each of its elements are converted and stored in dst.
+// For any other type, it is converted using the reflect.Value.Convert function (if possible).
+//
+// If dst is not settable, an error is returned.
+// If src cannot be converted to dst, an error is returned.
+// If any error occurs during conversion (e.g. deserialization), it is returned.
+//
+// Returns:
+//   - error: the error occurred during conversion, or nil if no error occurred.
+func Convert(src reflect.Value, dst reflect.Value) E.NestedError {
+	srcT := src.Type()
+	dstVT := dst.Type()
+
+	if src.Kind() == reflect.Interface {
+		src = src.Elem()
+		srcT = src.Type()
+	}
+
+	if !dst.CanSet() {
+		return E.From(fmt.Errorf("%w type %T is unsettable", E.ErrUnsupported, dst.Interface()))
+	}
+
+	switch {
+	case srcT.AssignableTo(dstVT):
+		dst.Set(src)
+	case srcT.ConvertibleTo(dstVT):
+		dst.Set(src.Convert(dstVT))
+	case srcT.Kind() == reflect.Map:
+		if dstVT.Kind() != reflect.Map {
+			return E.TypeError("map", srcT, dstVT)
 		}
+		obj, ok := src.Interface().(SerializedObject)
+		if !ok {
+			return E.TypeError("map", srcT, dstVT)
+		}
+		err := Deserialize(obj, dst.Addr().Interface())
+		if err != nil {
+			return err
+		}
+	case srcT.Kind() == reflect.Slice:
+		if dstVT.Kind() != reflect.Slice {
+			return E.TypeError("slice", srcT, dstVT)
+		}
+		newSlice := reflect.MakeSlice(dstVT, 0, src.Len())
+		i := 0
+		for _, v := range src.Seq2() {
+			tmp := reflect.New(dstVT.Elem()).Elem()
+			err := Convert(v, tmp)
+			if err != nil {
+				return err.Subjectf("[%d]", i)
+			}
+			newSlice = reflect.Append(newSlice, tmp)
+			i++
+		}
+		dst.Set(newSlice)
+	default:
+		// check if Convertor is implemented
+		if converter, ok := dst.Interface().(Convertor); ok {
+			converted, err := converter.ConvertFrom(src.Interface())
+			if err != nil {
+				return err
+			}
+			dst.Set(reflect.ValueOf(converted))
+			return nil
+		}
+		return E.TypeError("conversion", srcT, dstVT)
 	}
 
 	return nil
@@ -197,7 +250,7 @@ func Deserialize(src SerializedObject, target any) E.NestedError {
 
 func DeserializeJson(j map[string]string, target any) E.NestedError {
 	data, err := E.Check(json.Marshal(j))
-	if err.HasError() {
+	if err != nil {
 		return err
 	}
 	return E.From(json.Unmarshal(data, target))
@@ -206,5 +259,3 @@ func DeserializeJson(j map[string]string, target any) E.NestedError {
 func ToLowerNoSnake(s string) string {
 	return strings.ToLower(strings.ReplaceAll(s, "_", ""))
 }
-
-type SerializedObject = map[string]any

internal/utils/serialization_test.go

@@ -0,0 +1,47 @@
+package utils
+
+import (
+	"testing"
+
+	. "github.com/yusing/go-proxy/internal/utils/testing"
+)
+
+type S = struct {
+	I   int
+	S   string
+	IS  []int
+	SS  []string
+	MSI map[string]int
+	MIS map[int]string
+}
+
+var testStruct = S{
+	I:   1,
+	S:   "hello",
+	IS:  []int{1, 2, 3},
+	SS:  []string{"a", "b", "c"},
+	MSI: map[string]int{"a": 1, "b": 2, "c": 3},
+	MIS: map[int]string{1: "a", 2: "b", 3: "c"},
+}
+
+var testStructSerialized = map[string]any{
+	"I":   1,
+	"S":   "hello",
+	"IS":  []int{1, 2, 3},
+	"SS":  []string{"a", "b", "c"},
+	"MSI": map[string]int{"a": 1, "b": 2, "c": 3},
+	"MIS": map[int]string{1: "a", 2: "b", 3: "c"},
+}
+
+func TestSerialize(t *testing.T) {
+	s, err := Serialize(testStruct)
+	ExpectNoError(t, err.Error())
+	ExpectDeepEqual(t, s, testStructSerialized)
+}
+
+func TestDeserialize(t *testing.T) {
+	var s S
+	err := Deserialize(testStructSerialized, &s)
+	ExpectNoError(t, err.Error())
+	ExpectDeepEqual(t, s, testStruct)
+}