7 files changed, 1079 insertions, 0 deletions
diff --git a/modules/setting/config.go b/modules/setting/config.go
new file mode 100644
index 0000000..0355857
--- /dev/null
+++ b/modules/setting/config.go
@@ -0,0 +1,98 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"sync"
+
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting/config"
+)
+
+type PictureStruct struct {
+	DisableGravatar       *config.Value[bool]
+	EnableFederatedAvatar *config.Value[bool]
+}
+
+type OpenWithEditorApp struct {
+	DisplayName string
+	OpenURL     string
+}
+
+type OpenWithEditorAppsType []OpenWithEditorApp
+
+func (t OpenWithEditorAppsType) ToTextareaString() string {
+	ret := ""
+	for _, app := range t {
+		ret += app.DisplayName + " = " + app.OpenURL + "\n"
+	}
+	return ret
+}
+
+func DefaultOpenWithEditorApps() OpenWithEditorAppsType {
+	return OpenWithEditorAppsType{
+		{
+			DisplayName: "VS Code",
+			OpenURL:     "vscode://vscode.git/clone?url={url}",
+		},
+		{
+			DisplayName: "VSCodium",
+			OpenURL:     "vscodium://vscode.git/clone?url={url}",
+		},
+		{
+			DisplayName: "Intellij IDEA",
+			OpenURL:     "jetbrains://idea/checkout/git?idea.required.plugins.id=Git4Idea&checkout.repo={url}",
+		},
+	}
+}
+
+type RepositoryStruct struct {
+	OpenWithEditorApps *config.Value[OpenWithEditorAppsType]
+}
+
+type ConfigStruct struct {
+	Picture    *PictureStruct
+	Repository *RepositoryStruct
+}
+
+var (
+	defaultConfig     *ConfigStruct
+	defaultConfigOnce sync.Once
+)
+
+func initDefaultConfig() {
+	config.SetCfgSecKeyGetter(&cfgSecKeyGetter{})
+	defaultConfig = &ConfigStruct{
+		Picture: &PictureStruct{
+			DisableGravatar:       config.ValueJSON[bool]("picture.disable_gravatar").WithFileConfig(config.CfgSecKey{Sec: "picture", Key: "DISABLE_GRAVATAR"}),
+			EnableFederatedAvatar: config.ValueJSON[bool]("picture.enable_federated_avatar").WithFileConfig(config.CfgSecKey{Sec: "picture", Key: "ENABLE_FEDERATED_AVATAR"}),
+		},
+		Repository: &RepositoryStruct{
+			OpenWithEditorApps: config.ValueJSON[OpenWithEditorAppsType]("repository.open-with.editor-apps"),
+		},
+	}
+}
+
+func Config() *ConfigStruct {
+	defaultConfigOnce.Do(initDefaultConfig)
+	return defaultConfig
+}
+
+type cfgSecKeyGetter struct{}
+
+func (c cfgSecKeyGetter) GetValue(sec, key string) (v string, has bool) {
+	if key == "" {
+		return "", false
+	}
+	cfgSec, err := CfgProvider.GetSection(sec)
+	if err != nil {
+		log.Error("Unable to get config section: %q", sec)
+		return "", false
+	}
+	cfgKey := ConfigSectionKey(cfgSec, key)
+	if cfgKey == nil {
+		return "", false
+	}
+	return cfgKey.Value(), true
+}
diff --git a/modules/setting/config/getter.go b/modules/setting/config/getter.go
new file mode 100644
index 0000000..99f9a47
--- /dev/null
+++ b/modules/setting/config/getter.go
@@ -0,0 +1,49 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package config
+
+import (
+	"context"
+	"sync"
+)
+
+var getterMu sync.RWMutex
+
+type CfgSecKeyGetter interface {
+	GetValue(sec, key string) (v string, has bool)
+}
+
+var cfgSecKeyGetterInternal CfgSecKeyGetter
+
+func SetCfgSecKeyGetter(p CfgSecKeyGetter) {
+	getterMu.Lock()
+	cfgSecKeyGetterInternal = p
+	getterMu.Unlock()
+}
+
+func GetCfgSecKeyGetter() CfgSecKeyGetter {
+	getterMu.RLock()
+	defer getterMu.RUnlock()
+	return cfgSecKeyGetterInternal
+}
+
+type DynKeyGetter interface {
+	GetValue(ctx context.Context, key string) (v string, has bool)
+	GetRevision(ctx context.Context) int
+	InvalidateCache()
+}
+
+var dynKeyGetterInternal DynKeyGetter
+
+func SetDynGetter(p DynKeyGetter) {
+	getterMu.Lock()
+	dynKeyGetterInternal = p
+	getterMu.Unlock()
+}
+
+func GetDynGetter() DynKeyGetter {
+	getterMu.RLock()
+	defer getterMu.RUnlock()
+	return dynKeyGetterInternal
+}
diff --git a/modules/setting/config/value.go b/modules/setting/config/value.go
new file mode 100644
index 0000000..f0ec120
--- /dev/null
+++ b/modules/setting/config/value.go
@@ -0,0 +1,94 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package config
+
+import (
+	"context"
+	"sync"
+
+	"code.gitea.io/gitea/modules/json"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/util"
+)
+
+type CfgSecKey struct {
+	Sec, Key string
+}
+
+type Value[T any] struct {
+	mu sync.RWMutex
+
+	cfgSecKey CfgSecKey
+	dynKey    string
+
+	def, value T
+	revision   int
+}
+
+func (value *Value[T]) parse(key, valStr string) (v T) {
+	v = value.def
+	if valStr != "" {
+		if err := json.Unmarshal(util.UnsafeStringToBytes(valStr), &v); err != nil {
+			log.Error("Unable to unmarshal json config for key %q, err: %v", key, err)
+		}
+	}
+	return v
+}
+
+func (value *Value[T]) Value(ctx context.Context) (v T) {
+	dg := GetDynGetter()
+	if dg == nil {
+		// this is an edge case: the database is not initialized but the system setting is going to be used
+		// it should panic to avoid inconsistent config values (from config / system setting) and fix the code
+		panic("no config dyn value getter")
+	}
+
+	rev := dg.GetRevision(ctx)
+
+	// if the revision in database doesn't change, use the last value
+	value.mu.RLock()
+	if rev == value.revision {
+		v = value.value
+		value.mu.RUnlock()
+		return v
+	}
+	value.mu.RUnlock()
+
+	// try to parse the config and cache it
+	var valStr *string
+	if dynVal, has := dg.GetValue(ctx, value.dynKey); has {
+		valStr = &dynVal
+	} else if cfgVal, has := GetCfgSecKeyGetter().GetValue(value.cfgSecKey.Sec, value.cfgSecKey.Key); has {
+		valStr = &cfgVal
+	}
+	if valStr == nil {
+		v = value.def
+	} else {
+		v = value.parse(value.dynKey, *valStr)
+	}
+
+	value.mu.Lock()
+	value.value = v
+	value.revision = rev
+	value.mu.Unlock()
+	return v
+}
+
+func (value *Value[T]) DynKey() string {
+	return value.dynKey
+}
+
+func (value *Value[T]) WithDefault(def T) *Value[T] {
+	value.def = def
+	return value
+}
+
+func (value *Value[T]) WithFileConfig(cfgSecKey CfgSecKey) *Value[T] {
+	value.cfgSecKey = cfgSecKey
+	return value
+}
+
+func ValueJSON[T any](dynKey string) *Value[T] {
+	return &Value[T]{dynKey: dynKey}
+}
diff --git a/modules/setting/config_env.go b/modules/setting/config_env.go
new file mode 100644
index 0000000..fa0100d
--- /dev/null
+++ b/modules/setting/config_env.go
@@ -0,0 +1,170 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"bytes"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"code.gitea.io/gitea/modules/log"
+)
+
+const (
+	EnvConfigKeyPrefixGitea = "^(FORGEJO|GITEA)__"
+	EnvConfigKeySuffixFile  = "__FILE"
+)
+
+const escapeRegexpString = "_0[xX](([0-9a-fA-F][0-9a-fA-F])+)_"
+
+var escapeRegex = regexp.MustCompile(escapeRegexpString)
+
+func CollectEnvConfigKeys() (keys []string) {
+	for _, env := range os.Environ() {
+		if strings.HasPrefix(env, EnvConfigKeyPrefixGitea) {
+			k, _, _ := strings.Cut(env, "=")
+			keys = append(keys, k)
+		}
+	}
+	return keys
+}
+
+func ClearEnvConfigKeys() {
+	for _, k := range CollectEnvConfigKeys() {
+		_ = os.Unsetenv(k)
+	}
+}
+
+// decodeEnvSectionKey will decode a portable string encoded Section__Key pair
+// Portable strings are considered to be of the form [A-Z0-9_]*
+// We will encode a disallowed value as the UTF8 byte string preceded by _0X and
+// followed by _. E.g. _0X2C_ for a '-' and _0X2E_ for '.'
+// Section and Key are separated by a plain '__'.
+// The entire section can be encoded as a UTF8 byte string
+func decodeEnvSectionKey(encoded string) (ok bool, section, key string) {
+	inKey := false
+	last := 0
+	escapeStringIndices := escapeRegex.FindAllStringIndex(encoded, -1)
+	for _, unescapeIdx := range escapeStringIndices {
+		preceding := encoded[last:unescapeIdx[0]]
+		if !inKey {
+			if splitter := strings.Index(preceding, "__"); splitter > -1 {
+				section += preceding[:splitter]
+				inKey = true
+				key += preceding[splitter+2:]
+			} else {
+				section += preceding
+			}
+		} else {
+			key += preceding
+		}
+		toDecode := encoded[unescapeIdx[0]+3 : unescapeIdx[1]-1]
+		decodedBytes := make([]byte, len(toDecode)/2)
+		for i := 0; i < len(toDecode)/2; i++ {
+			// Can ignore error here as we know these should be hexadecimal from the regexp
+			byteInt, _ := strconv.ParseInt(toDecode[2*i:2*i+2], 16, 0)
+			decodedBytes[i] = byte(byteInt)
+		}
+		if inKey {
+			key += string(decodedBytes)
+		} else {
+			section += string(decodedBytes)
+		}
+		last = unescapeIdx[1]
+	}
+	remaining := encoded[last:]
+	if !inKey {
+		if splitter := strings.Index(remaining, "__"); splitter > -1 {
+			section += remaining[:splitter]
+			key += remaining[splitter+2:]
+		} else {
+			section += remaining
+		}
+	} else {
+		key += remaining
+	}
+	section = strings.ToLower(section)
+	ok = key != ""
+	if !ok {
+		section = ""
+		key = ""
+	}
+	return ok, section, key
+}
+
+// decodeEnvironmentKey decode the environment key to section and key
+// The environment key is in the form of GITEA__SECTION__KEY or GITEA__SECTION__KEY__FILE
+func decodeEnvironmentKey(prefixRegexp *regexp.Regexp, suffixFile, envKey string) (ok bool, section, key string, useFileValue bool) { //nolint:unparam
+	if strings.HasSuffix(envKey, suffixFile) {
+		useFileValue = true
+		envKey = envKey[:len(envKey)-len(suffixFile)]
+	}
+	loc := prefixRegexp.FindStringIndex(envKey)
+	if loc == nil {
+		return false, "", "", false
+	}
+	ok, section, key = decodeEnvSectionKey(envKey[loc[1]:])
+	return ok, section, key, useFileValue
+}
+
+func EnvironmentToConfig(cfg ConfigProvider, envs []string) (changed bool) {
+	prefixRegexp := regexp.MustCompile(EnvConfigKeyPrefixGitea)
+	for _, kv := range envs {
+		idx := strings.IndexByte(kv, '=')
+		if idx < 0 {
+			continue
+		}
+
+		// parse the environment variable to config section name and key name
+		envKey := kv[:idx]
+		envValue := kv[idx+1:]
+		ok, sectionName, keyName, useFileValue := decodeEnvironmentKey(prefixRegexp, EnvConfigKeySuffixFile, envKey)
+		if !ok {
+			continue
+		}
+
+		// use environment value as config value, or read the file content as value if the key indicates a file
+		keyValue := envValue
+		if useFileValue {
+			fileContent, err := os.ReadFile(envValue)
+			if err != nil {
+				log.Error("Error reading file for %s : %v", envKey, envValue, err)
+				continue
+			}
+			if bytes.HasSuffix(fileContent, []byte("\r\n")) {
+				fileContent = fileContent[:len(fileContent)-2]
+			} else if bytes.HasSuffix(fileContent, []byte("\n")) {
+				fileContent = fileContent[:len(fileContent)-1]
+			}
+			keyValue = string(fileContent)
+		}
+
+		// try to set the config value if necessary
+		section, err := cfg.GetSection(sectionName)
+		if err != nil {
+			section, err = cfg.NewSection(sectionName)
+			if err != nil {
+				log.Error("Error creating section: %s : %v", sectionName, err)
+				continue
+			}
+		}
+		key := ConfigSectionKey(section, keyName)
+		if key == nil {
+			changed = true
+			key, err = section.NewKey(keyName, keyValue)
+			if err != nil {
+				log.Error("Error creating key: %s in section: %s with value: %s : %v", keyName, sectionName, keyValue, err)
+				continue
+			}
+		}
+		oldValue := key.Value()
+		if !changed && oldValue != keyValue {
+			changed = true
+		}
+		key.SetValue(keyValue)
+	}
+	return changed
+}
diff --git a/modules/setting/config_env_test.go b/modules/setting/config_env_test.go
new file mode 100644
index 0000000..bec3e58
--- /dev/null
+++ b/modules/setting/config_env_test.go
@@ -0,0 +1,151 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"os"
+	"regexp"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDecodeEnvSectionKey(t *testing.T) {
+	ok, section, key := decodeEnvSectionKey("SEC__KEY")
+	assert.True(t, ok)
+	assert.Equal(t, "sec", section)
+	assert.Equal(t, "KEY", key)
+
+	ok, section, key = decodeEnvSectionKey("sec__key")
+	assert.True(t, ok)
+	assert.Equal(t, "sec", section)
+	assert.Equal(t, "key", key)
+
+	ok, section, key = decodeEnvSectionKey("LOG_0x2E_CONSOLE__STDERR")
+	assert.True(t, ok)
+	assert.Equal(t, "log.console", section)
+	assert.Equal(t, "STDERR", key)
+
+	ok, section, key = decodeEnvSectionKey("SEC")
+	assert.False(t, ok)
+	assert.Equal(t, "", section)
+	assert.Equal(t, "", key)
+}
+
+func TestDecodeEnvironmentKey(t *testing.T) {
+	prefix := regexp.MustCompile(EnvConfigKeyPrefixGitea)
+	suffix := "__FILE"
+
+	ok, section, key, file := decodeEnvironmentKey(prefix, suffix, "SEC__KEY")
+	assert.False(t, ok)
+	assert.Equal(t, "", section)
+	assert.Equal(t, "", key)
+	assert.False(t, file)
+
+	ok, section, key, file = decodeEnvironmentKey(prefix, suffix, "GITEA__SEC")
+	assert.False(t, ok)
+	assert.Equal(t, "", section)
+	assert.Equal(t, "", key)
+	assert.False(t, file)
+
+	ok, section, key, file = decodeEnvironmentKey(prefix, suffix, "GITEA____KEY")
+	assert.True(t, ok)
+	assert.Equal(t, "", section)
+	assert.Equal(t, "KEY", key)
+	assert.False(t, file)
+
+	ok, section, key, file = decodeEnvironmentKey(prefix, suffix, "GITEA__SEC__KEY")
+	assert.True(t, ok)
+	assert.Equal(t, "sec", section)
+	assert.Equal(t, "KEY", key)
+	assert.False(t, file)
+
+	ok, section, key, file = decodeEnvironmentKey(prefix, suffix, "FORGEJO__SEC__KEY")
+	assert.True(t, ok)
+	assert.Equal(t, "sec", section)
+	assert.Equal(t, "KEY", key)
+	assert.False(t, file)
+
+	// with "__FILE" suffix, it doesn't support to write "[sec].FILE" to config (no such key FILE is used in Gitea)
+	// but it could be fixed in the future by adding a new suffix like "__VALUE" (no such key VALUE is used in Gitea either)
+	ok, section, key, file = decodeEnvironmentKey(prefix, suffix, "GITEA__SEC__FILE")
+	assert.False(t, ok)
+	assert.Equal(t, "", section)
+	assert.Equal(t, "", key)
+	assert.True(t, file)
+
+	ok, section, key, file = decodeEnvironmentKey(prefix, suffix, "GITEA__SEC__KEY__FILE")
+	assert.True(t, ok)
+	assert.Equal(t, "sec", section)
+	assert.Equal(t, "KEY", key)
+	assert.True(t, file)
+}
+
+func TestEnvironmentToConfig(t *testing.T) {
+	cfg, _ := NewConfigProviderFromData("")
+
+	changed := EnvironmentToConfig(cfg, nil)
+	assert.False(t, changed)
+
+	cfg, err := NewConfigProviderFromData(`
+[sec]
+key = old
+`)
+	require.NoError(t, err)
+
+	changed = EnvironmentToConfig(cfg, []string{"GITEA__sec__key=new"})
+	assert.True(t, changed)
+	assert.Equal(t, "new", cfg.Section("sec").Key("key").String())
+
+	changed = EnvironmentToConfig(cfg, []string{"GITEA__sec__key=new"})
+	assert.False(t, changed)
+
+	tmpFile := t.TempDir() + "/the-file"
+	_ = os.WriteFile(tmpFile, []byte("value-from-file"), 0o644)
+	changed = EnvironmentToConfig(cfg, []string{"GITEA__sec__key__FILE=" + tmpFile})
+	assert.True(t, changed)
+	assert.Equal(t, "value-from-file", cfg.Section("sec").Key("key").String())
+
+	cfg, _ = NewConfigProviderFromData("")
+	_ = os.WriteFile(tmpFile, []byte("value-from-file\n"), 0o644)
+	EnvironmentToConfig(cfg, []string{"GITEA__sec__key__FILE=" + tmpFile})
+	assert.Equal(t, "value-from-file", cfg.Section("sec").Key("key").String())
+
+	cfg, _ = NewConfigProviderFromData("")
+	_ = os.WriteFile(tmpFile, []byte("value-from-file\r\n"), 0o644)
+	EnvironmentToConfig(cfg, []string{"GITEA__sec__key__FILE=" + tmpFile})
+	assert.Equal(t, "value-from-file", cfg.Section("sec").Key("key").String())
+
+	cfg, _ = NewConfigProviderFromData("")
+	_ = os.WriteFile(tmpFile, []byte("value-from-file\n\n"), 0o644)
+	EnvironmentToConfig(cfg, []string{"GITEA__sec__key__FILE=" + tmpFile})
+	assert.Equal(t, "value-from-file\n", cfg.Section("sec").Key("key").String())
+}
+
+func TestEnvironmentToConfigSubSecKey(t *testing.T) {
+	// the INI package has a quirk: by default, the keys are inherited.
+	// when maintaining the keys, the newly added sub key should not be affected by the parent key.
+	cfg, err := NewConfigProviderFromData(`
+[sec]
+key = some
+`)
+	require.NoError(t, err)
+
+	changed := EnvironmentToConfig(cfg, []string{"GITEA__sec_0X2E_sub__key=some"})
+	assert.True(t, changed)
+
+	tmpFile := t.TempDir() + "/test-sub-sec-key.ini"
+	defer os.Remove(tmpFile)
+	err = cfg.SaveTo(tmpFile)
+	require.NoError(t, err)
+	bs, err := os.ReadFile(tmpFile)
+	require.NoError(t, err)
+	assert.Equal(t, `[sec]
+key = some
+
+[sec.sub]
+key = some
+`, string(bs))
+}
diff --git a/modules/setting/config_provider.go b/modules/setting/config_provider.go
new file mode 100644
index 0000000..12cf36a
--- /dev/null
+++ b/modules/setting/config_provider.go
@@ -0,0 +1,360 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/util"
+
+	"gopkg.in/ini.v1" //nolint:depguard
+)
+
+type ConfigKey interface {
+	Name() string
+	Value() string
+	SetValue(v string)
+
+	In(defaultVal string, candidates []string) string
+	String() string
+	Strings(delim string) []string
+
+	MustString(defaultVal string) string
+	MustBool(defaultVal ...bool) bool
+	MustInt(defaultVal ...int) int
+	MustInt64(defaultVal ...int64) int64
+	MustDuration(defaultVal ...time.Duration) time.Duration
+}
+
+type ConfigSection interface {
+	Name() string
+	MapTo(any) error
+	HasKey(key string) bool
+	NewKey(name, value string) (ConfigKey, error)
+	Key(key string) ConfigKey
+	Keys() []ConfigKey
+	ChildSections() []ConfigSection
+}
+
+// ConfigProvider represents a config provider
+type ConfigProvider interface {
+	Section(section string) ConfigSection
+	Sections() []ConfigSection
+	NewSection(name string) (ConfigSection, error)
+	GetSection(name string) (ConfigSection, error)
+	Save() error
+	SaveTo(filename string) error
+
+	GetFile() string
+	DisableSaving()
+	PrepareSaving() (ConfigProvider, error)
+	IsLoadedFromEmpty() bool
+}
+
+type iniConfigProvider struct {
+	file string
+	ini  *ini.File
+
+	disableSaving   bool // disable the "Save" method because the config options could be polluted
+	loadedFromEmpty bool // whether the file has not existed previously
+}
+
+type iniConfigSection struct {
+	sec *ini.Section
+}
+
+var (
+	_ ConfigProvider = (*iniConfigProvider)(nil)
+	_ ConfigSection  = (*iniConfigSection)(nil)
+	_ ConfigKey      = (*ini.Key)(nil)
+)
+
+// ConfigSectionKey only searches the keys in the given section, but it is O(n).
+// ini package has a special behavior:  with "[sec] a=1" and an empty "[sec.sub]",
+// then in "[sec.sub]", Key()/HasKey() can always see "a=1" because it always tries parent sections.
+// It returns nil if the key doesn't exist.
+func ConfigSectionKey(sec ConfigSection, key string) ConfigKey {
+	if sec == nil {
+		return nil
+	}
+	for _, k := range sec.Keys() {
+		if k.Name() == key {
+			return k
+		}
+	}
+	return nil
+}
+
+func ConfigSectionKeyString(sec ConfigSection, key string, def ...string) string {
+	k := ConfigSectionKey(sec, key)
+	if k != nil && k.String() != "" {
+		return k.String()
+	}
+	if len(def) > 0 {
+		return def[0]
+	}
+	return ""
+}
+
+func ConfigSectionKeyBool(sec ConfigSection, key string, def ...bool) bool {
+	k := ConfigSectionKey(sec, key)
+	if k != nil && k.String() != "" {
+		b, _ := strconv.ParseBool(k.String())
+		return b
+	}
+	if len(def) > 0 {
+		return def[0]
+	}
+	return false
+}
+
+// ConfigInheritedKey works like ini.Section.Key(), but it always returns a new key instance, it is O(n) because NewKey is O(n)
+// and the returned key is safe to be used with "MustXxx", it doesn't change the parent's values.
+// Otherwise, ini.Section.Key().MustXxx would pollute the parent section's keys.
+// It never returns nil.
+func ConfigInheritedKey(sec ConfigSection, key string) ConfigKey {
+	k := sec.Key(key)
+	if k != nil && k.String() != "" {
+		newKey, _ := sec.NewKey(k.Name(), k.String())
+		return newKey
+	}
+	newKey, _ := sec.NewKey(key, "")
+	return newKey
+}
+
+func ConfigInheritedKeyString(sec ConfigSection, key string, def ...string) string {
+	k := sec.Key(key)
+	if k != nil && k.String() != "" {
+		return k.String()
+	}
+	if len(def) > 0 {
+		return def[0]
+	}
+	return ""
+}
+
+func (s *iniConfigSection) Name() string {
+	return s.sec.Name()
+}
+
+func (s *iniConfigSection) MapTo(v any) error {
+	return s.sec.MapTo(v)
+}
+
+func (s *iniConfigSection) HasKey(key string) bool {
+	return s.sec.HasKey(key)
+}
+
+func (s *iniConfigSection) NewKey(name, value string) (ConfigKey, error) {
+	return s.sec.NewKey(name, value)
+}
+
+func (s *iniConfigSection) Key(key string) ConfigKey {
+	return s.sec.Key(key)
+}
+
+func (s *iniConfigSection) Keys() (keys []ConfigKey) {
+	for _, k := range s.sec.Keys() {
+		keys = append(keys, k)
+	}
+	return keys
+}
+
+func (s *iniConfigSection) ChildSections() (sections []ConfigSection) {
+	for _, s := range s.sec.ChildSections() {
+		sections = append(sections, &iniConfigSection{s})
+	}
+	return sections
+}
+
+func configProviderLoadOptions() ini.LoadOptions {
+	return ini.LoadOptions{
+		KeyValueDelimiterOnWrite: " = ",
+		IgnoreContinuation:       true,
+	}
+}
+
+// NewConfigProviderFromData this function is mainly for testing purpose
+func NewConfigProviderFromData(configContent string) (ConfigProvider, error) {
+	cfg, err := ini.LoadSources(configProviderLoadOptions(), strings.NewReader(configContent))
+	if err != nil {
+		return nil, err
+	}
+	cfg.NameMapper = ini.SnackCase
+	return &iniConfigProvider{
+		ini:             cfg,
+		loadedFromEmpty: true,
+	}, nil
+}
+
+// NewConfigProviderFromFile load configuration from file.
+// NOTE: do not print any log except error.
+func NewConfigProviderFromFile(file string) (ConfigProvider, error) {
+	cfg := ini.Empty(configProviderLoadOptions())
+	loadedFromEmpty := true
+
+	if file != "" {
+		isFile, err := util.IsFile(file)
+		if err != nil {
+			return nil, fmt.Errorf("unable to check if %q is a file. Error: %v", file, err)
+		}
+		if isFile {
+			if err = cfg.Append(file); err != nil {
+				return nil, fmt.Errorf("failed to load config file %q: %v", file, err)
+			}
+			loadedFromEmpty = false
+		}
+	}
+
+	cfg.NameMapper = ini.SnackCase
+	return &iniConfigProvider{
+		file:            file,
+		ini:             cfg,
+		loadedFromEmpty: loadedFromEmpty,
+	}, nil
+}
+
+func (p *iniConfigProvider) Section(section string) ConfigSection {
+	return &iniConfigSection{sec: p.ini.Section(section)}
+}
+
+func (p *iniConfigProvider) Sections() (sections []ConfigSection) {
+	for _, s := range p.ini.Sections() {
+		sections = append(sections, &iniConfigSection{s})
+	}
+	return sections
+}
+
+func (p *iniConfigProvider) NewSection(name string) (ConfigSection, error) {
+	sec, err := p.ini.NewSection(name)
+	if err != nil {
+		return nil, err
+	}
+	return &iniConfigSection{sec: sec}, nil
+}
+
+func (p *iniConfigProvider) GetSection(name string) (ConfigSection, error) {
+	sec, err := p.ini.GetSection(name)
+	if err != nil {
+		return nil, err
+	}
+	return &iniConfigSection{sec: sec}, nil
+}
+
+var errDisableSaving = errors.New("this config can't be saved, developers should prepare a new config to save")
+
+func (p *iniConfigProvider) GetFile() string {
+	return p.file
+}
+
+// Save saves the content into file
+func (p *iniConfigProvider) Save() error {
+	if p.disableSaving {
+		return errDisableSaving
+	}
+	filename := p.file
+	if filename == "" {
+		return fmt.Errorf("config file path must not be empty")
+	}
+	if p.loadedFromEmpty {
+		if err := os.MkdirAll(filepath.Dir(filename), os.ModePerm); err != nil {
+			return fmt.Errorf("failed to create %q: %v", filename, err)
+		}
+	}
+	if err := p.ini.SaveTo(filename); err != nil {
+		return fmt.Errorf("failed to save %q: %v", filename, err)
+	}
+
+	// Change permissions to be more restrictive
+	fi, err := os.Stat(filename)
+	if err != nil {
+		return fmt.Errorf("failed to determine current conf file permissions: %v", err)
+	}
+
+	if fi.Mode().Perm() > 0o600 {
+		if err = os.Chmod(filename, 0o600); err != nil {
+			log.Warn("Failed changing conf file permissions to -rw-------. Consider changing them manually.")
+		}
+	}
+	return nil
+}
+
+func (p *iniConfigProvider) SaveTo(filename string) error {
+	if p.disableSaving {
+		return errDisableSaving
+	}
+	return p.ini.SaveTo(filename)
+}
+
+// DisableSaving disables the saving function, use PrepareSaving to get clear config options.
+func (p *iniConfigProvider) DisableSaving() {
+	p.disableSaving = true
+}
+
+// PrepareSaving loads the ini from file again to get clear config options.
+// Otherwise, the "MustXxx" calls would have polluted the current config provider,
+// it makes the "Save" outputs a lot of garbage options
+// After the INI package gets refactored, no "MustXxx" pollution, this workaround can be dropped.
+func (p *iniConfigProvider) PrepareSaving() (ConfigProvider, error) {
+	if p.file == "" {
+		return nil, errors.New("no config file to save")
+	}
+	return NewConfigProviderFromFile(p.file)
+}
+
+func (p *iniConfigProvider) IsLoadedFromEmpty() bool {
+	return p.loadedFromEmpty
+}
+
+func mustMapSetting(rootCfg ConfigProvider, sectionName string, setting any) {
+	if err := rootCfg.Section(sectionName).MapTo(setting); err != nil {
+		log.Fatal("Failed to map %s settings: %v", sectionName, err)
+	}
+}
+
+// DeprecatedWarnings contains the warning message for various deprecations, including: setting option, file/folder, etc
+var DeprecatedWarnings []string
+
+func deprecatedSetting(rootCfg ConfigProvider, oldSection, oldKey, newSection, newKey, version string) {
+	if rootCfg.Section(oldSection).HasKey(oldKey) {
+		msg := fmt.Sprintf("Deprecated config option `[%s]` `%s` present. Use `[%s]` `%s` instead. This fallback will be/has been removed in %s", oldSection, oldKey, newSection, newKey, version)
+		log.Error("%v", msg)
+		DeprecatedWarnings = append(DeprecatedWarnings, msg)
+	}
+}
+
+// deprecatedSettingDB add a hint that the configuration has been moved to database but still kept in app.ini
+func deprecatedSettingDB(rootCfg ConfigProvider, oldSection, oldKey string) {
+	if rootCfg.Section(oldSection).HasKey(oldKey) {
+		log.Error("Deprecated `[%s]` `%s` present which has been copied to database table sys_setting", oldSection, oldKey)
+	}
+}
+
+// NewConfigProviderForLocale loads locale configuration from source and others. "string" if for a local file path, "[]byte" is for INI content
+func NewConfigProviderForLocale(source any, others ...any) (ConfigProvider, error) {
+	iniFile, err := ini.LoadSources(ini.LoadOptions{
+		IgnoreInlineComment:         true,
+		UnescapeValueCommentSymbols: true,
+		IgnoreContinuation:          true,
+	}, source, others...)
+	if err != nil {
+		return nil, fmt.Errorf("unable to load locale ini: %w", err)
+	}
+	iniFile.BlockMode = false
+	return &iniConfigProvider{
+		ini:             iniFile,
+		loadedFromEmpty: true,
+	}, nil
+}
+
+func init() {
+	ini.PrettyFormat = false
+}
diff --git a/modules/setting/config_provider_test.go b/modules/setting/config_provider_test.go
new file mode 100644
index 0000000..702be80
--- /dev/null
+++ b/modules/setting/config_provider_test.go
@@ -0,0 +1,157 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestConfigProviderBehaviors(t *testing.T) {
+	t.Run("BuggyKeyOverwritten", func(t *testing.T) {
+		cfg, _ := NewConfigProviderFromData(`
+[foo]
+key =
+`)
+		sec := cfg.Section("foo")
+		secSub := cfg.Section("foo.bar")
+		secSub.Key("key").MustString("1")             // try to read a key from subsection
+		assert.Equal(t, "1", sec.Key("key").String()) // TODO: BUGGY! the key in [foo] is overwritten
+	})
+
+	t.Run("SubsectionSeeParentKeys", func(t *testing.T) {
+		cfg, _ := NewConfigProviderFromData(`
+[foo]
+key = 123
+`)
+		secSub := cfg.Section("foo.bar.xxx")
+		assert.Equal(t, "123", secSub.Key("key").String())
+	})
+	t.Run("TrailingSlash", func(t *testing.T) {
+		cfg, _ := NewConfigProviderFromData(`
+[foo]
+key = E:\
+xxx = yyy
+`)
+		sec := cfg.Section("foo")
+		assert.Equal(t, "E:\\", sec.Key("key").String())
+		assert.Equal(t, "yyy", sec.Key("xxx").String())
+	})
+}
+
+func TestConfigProviderHelper(t *testing.T) {
+	cfg, _ := NewConfigProviderFromData(`
+[foo]
+empty =
+key = 123
+`)
+
+	sec := cfg.Section("foo")
+	secSub := cfg.Section("foo.bar")
+
+	// test empty key
+	assert.Equal(t, "def", ConfigSectionKeyString(sec, "empty", "def"))
+	assert.Equal(t, "xyz", ConfigSectionKeyString(secSub, "empty", "xyz"))
+
+	// test non-inherited key, only see the keys in current section
+	assert.NotNil(t, ConfigSectionKey(sec, "key"))
+	assert.Nil(t, ConfigSectionKey(secSub, "key"))
+
+	// test default behavior
+	assert.Equal(t, "123", ConfigSectionKeyString(sec, "key"))
+	assert.Equal(t, "", ConfigSectionKeyString(secSub, "key"))
+	assert.Equal(t, "def", ConfigSectionKeyString(secSub, "key", "def"))
+
+	assert.Equal(t, "123", ConfigInheritedKeyString(secSub, "key"))
+
+	// Workaround for ini package's BuggyKeyOverwritten behavior
+	assert.Equal(t, "", ConfigSectionKeyString(sec, "empty"))
+	assert.Equal(t, "", ConfigSectionKeyString(secSub, "empty"))
+	assert.Equal(t, "def", ConfigInheritedKey(secSub, "empty").MustString("def"))
+	assert.Equal(t, "def", ConfigInheritedKey(secSub, "empty").MustString("xyz"))
+	assert.Equal(t, "", ConfigSectionKeyString(sec, "empty"))
+	assert.Equal(t, "def", ConfigSectionKeyString(secSub, "empty"))
+}
+
+func TestNewConfigProviderFromFile(t *testing.T) {
+	cfg, err := NewConfigProviderFromFile("no-such.ini")
+	require.NoError(t, err)
+	assert.True(t, cfg.IsLoadedFromEmpty())
+
+	// load non-existing file and save
+	testFile := t.TempDir() + "/test.ini"
+	testFile1 := t.TempDir() + "/test1.ini"
+	cfg, err = NewConfigProviderFromFile(testFile)
+	require.NoError(t, err)
+
+	sec, _ := cfg.NewSection("foo")
+	_, _ = sec.NewKey("k1", "a")
+	require.NoError(t, cfg.Save())
+	_, _ = sec.NewKey("k2", "b")
+	require.NoError(t, cfg.SaveTo(testFile1))
+
+	bs, err := os.ReadFile(testFile)
+	require.NoError(t, err)
+	assert.Equal(t, "[foo]\nk1 = a\n", string(bs))
+
+	bs, err = os.ReadFile(testFile1)
+	require.NoError(t, err)
+	assert.Equal(t, "[foo]\nk1 = a\nk2 = b\n", string(bs))
+
+	// load existing file and save
+	cfg, err = NewConfigProviderFromFile(testFile)
+	require.NoError(t, err)
+	assert.Equal(t, "a", cfg.Section("foo").Key("k1").String())
+	sec, _ = cfg.NewSection("bar")
+	_, _ = sec.NewKey("k1", "b")
+	require.NoError(t, cfg.Save())
+	bs, err = os.ReadFile(testFile)
+	require.NoError(t, err)
+	assert.Equal(t, "[foo]\nk1 = a\n\n[bar]\nk1 = b\n", string(bs))
+}
+
+func TestNewConfigProviderForLocale(t *testing.T) {
+	// load locale from file
+	localeFile := t.TempDir() + "/locale.ini"
+	_ = os.WriteFile(localeFile, []byte(`k1=a`), 0o644)
+	cfg, err := NewConfigProviderForLocale(localeFile)
+	require.NoError(t, err)
+	assert.Equal(t, "a", cfg.Section("").Key("k1").String())
+
+	// load locale from bytes
+	cfg, err = NewConfigProviderForLocale([]byte("k1=foo\nk2=bar"))
+	require.NoError(t, err)
+	assert.Equal(t, "foo", cfg.Section("").Key("k1").String())
+	cfg, err = NewConfigProviderForLocale([]byte("k1=foo\nk2=bar"), []byte("k2=xxx"))
+	require.NoError(t, err)
+	assert.Equal(t, "foo", cfg.Section("").Key("k1").String())
+	assert.Equal(t, "xxx", cfg.Section("").Key("k2").String())
+}
+
+func TestDisableSaving(t *testing.T) {
+	testFile := t.TempDir() + "/test.ini"
+	_ = os.WriteFile(testFile, []byte("k1=a\nk2=b"), 0o644)
+	cfg, err := NewConfigProviderFromFile(testFile)
+	require.NoError(t, err)
+
+	cfg.DisableSaving()
+	err = cfg.Save()
+	require.ErrorIs(t, err, errDisableSaving)
+
+	saveCfg, err := cfg.PrepareSaving()
+	require.NoError(t, err)
+
+	saveCfg.Section("").Key("k1").MustString("x")
+	saveCfg.Section("").Key("k2").SetValue("y")
+	saveCfg.Section("").Key("k3").SetValue("z")
+	err = saveCfg.Save()
+	require.NoError(t, err)
+
+	bs, err := os.ReadFile(testFile)
+	require.NoError(t, err)
+	assert.Equal(t, "k1 = a\nk2 = y\nk3 = z\n", string(bs))
+}