config: move [ui] parsing in separate file

The config.go file is getting too big. Move the aerc.conf [ui] section
parsing logic into a dedicated ui.go file.

Add a defaultUiConfig() function to also get the default configuration
values in a separate file.

Extract fragmented bits of code in AercConfig.parseConfig() in a new
AercConfig.parseUi() function defined in ui.go.

Change parseUiConfig() into a UIConfig.parse() method.

Change some methods receiver args to pointers to avoid unnecessary
copies.

No functional change.

Signed-off-by: Robin Jarry <robin@jarry.cc>
Acked-by: Moritz Poldrack <moritz@poldrack.dev>

2 files changed, 345 insertions, 316 deletions

diff --git a/config/config.go b/config/config.go
index 7a880b6d..91fd99a2 100644
--- a/config/config.go
+++ b/config/config.go
@@ -8,13 +8,10 @@ import (
 	"path"
 	"regexp"
 	"strings"
-	"time"
 	"unicode"
 
-	"github.com/gdamore/tcell/v2"
 	"github.com/go-ini/ini"
 	"github.com/google/shlex"
-	"github.com/imdario/mergo"
 	"github.com/kyoh86/xdg"
 	"github.com/mitchellh/go-homedir"
 
@@ -28,75 +25,6 @@ type GeneralConfig struct {
 	UnsafeAccountsConf bool   `ini:"unsafe-accounts-conf"`
 }
 
-type UIConfig struct {
-	AutoMarkRead                  bool          `ini:"auto-mark-read"`
-	IndexFormat                   string        `ini:"index-format"`
-	TimestampFormat               string        `ini:"timestamp-format"`
-	ThisDayTimeFormat             string        `ini:"this-day-time-format"`
-	ThisWeekTimeFormat            string        `ini:"this-week-time-format"`
-	ThisYearTimeFormat            string        `ini:"this-year-time-format"`
-	MessageViewTimestampFormat    string        `ini:"message-view-timestamp-format"`
-	MessageViewThisDayTimeFormat  string        `ini:"message-view-this-day-time-format"`
-	MessageViewThisWeekTimeFormat string        `ini:"message-view-this-week-time-format"`
-	MessageViewThisYearTimeFormat string        `ini:"message-view-this-year-time-format"`
-	ShowHeaders                   []string      `delim:","`
-	RenderAccountTabs             string        `ini:"render-account-tabs"`
-	PinnedTabMarker               string        `ini:"pinned-tab-marker"`
-	SidebarWidth                  int           `ini:"sidebar-width"`
-	PreviewHeight                 int           `ini:"preview-height"`
-	EmptyMessage                  string        `ini:"empty-message"`
-	EmptyDirlist                  string        `ini:"empty-dirlist"`
-	MouseEnabled                  bool          `ini:"mouse-enabled"`
-	ThreadingEnabled              bool          `ini:"threading-enabled"`
-	ForceClientThreads            bool          `ini:"force-client-threads"`
-	ClientThreadsDelay            time.Duration `ini:"client-threads-delay"`
-	FuzzyComplete                 bool          `ini:"fuzzy-complete"`
-	NewMessageBell                bool          `ini:"new-message-bell"`
-	Spinner                       string        `ini:"spinner"`
-	SpinnerDelimiter              string        `ini:"spinner-delimiter"`
-	IconUnencrypted               string        `ini:"icon-unencrypted"`
-	IconEncrypted                 string        `ini:"icon-encrypted"`
-	IconSigned                    string        `ini:"icon-signed"`
-	IconSignedEncrypted           string        `ini:"icon-signed-encrypted"`
-	IconUnknown                   string        `ini:"icon-unknown"`
-	IconInvalid                   string        `ini:"icon-invalid"`
-	DirListFormat                 string        `ini:"dirlist-format"`
-	DirListDelay                  time.Duration `ini:"dirlist-delay"`
-	DirListTree                   bool          `ini:"dirlist-tree"`
-	DirListCollapse               int           `ini:"dirlist-collapse"`
-	Sort                          []string      `delim:" "`
-	NextMessageOnDelete           bool          `ini:"next-message-on-delete"`
-	CompletionDelay               time.Duration `ini:"completion-delay"`
-	CompletionMinChars            int           `ini:"completion-min-chars"`
-	CompletionPopovers            bool          `ini:"completion-popovers"`
-	StyleSetDirs                  []string      `ini:"stylesets-dirs" delim:":"`
-	StyleSetName                  string        `ini:"styleset-name"`
-	style                         StyleSet
-	// customize border appearance
-	BorderCharVertical   rune `ini:"-"`
-	BorderCharHorizontal rune `ini:"-"`
-
-	ReverseOrder       bool `ini:"reverse-msglist-order"`
-	ReverseThreadOrder bool `ini:"reverse-thread-order"`
-	SortThreadSiblings bool `ini:"sort-thread-siblings"`
-}
-
-type ContextType int
-
-const (
-	UI_CONTEXT_FOLDER ContextType = iota
-	UI_CONTEXT_ACCOUNT
-	UI_CONTEXT_SUBJECT
-	BIND_CONTEXT_ACCOUNT
-	BIND_CONTEXT_FOLDER
-)
-
-type UIConfigContext struct {
-	ContextType ContextType
-	Regex       *regexp.Regexp
-	UiConfig    UIConfig
-}
-
 const (
 	FILTER_MIMETYPE = iota
 	FILTER_HEADER
@@ -326,61 +254,6 @@ func (config *AercConfig) LoadConfig(file *ini.File) error {
 		}
 	}
 
-	if ui, err := file.GetSection("ui"); err == nil {
-		if err := parseUiConfig(ui, &config.Ui); err != nil {
-			return err
-		}
-	}
-
-	for _, sectionName := range file.SectionStrings() {
-		if !strings.Contains(sectionName, "ui:") {
-			continue
-		}
-
-		uiSection, err := file.GetSection(sectionName)
-		if err != nil {
-			return err
-		}
-		uiSubConfig := UIConfig{}
-		if err := parseUiConfig(uiSection, &uiSubConfig); err != nil {
-			return err
-		}
-		contextualUi := UIConfigContext{
-			UiConfig: uiSubConfig,
-		}
-
-		var index int
-		switch {
-		case strings.Contains(sectionName, "~"):
-			index = strings.Index(sectionName, "~")
-			regex := string(sectionName[index+1:])
-			contextualUi.Regex, err = regexp.Compile(regex)
-			if err != nil {
-				return err
-			}
-		case strings.Contains(sectionName, "="):
-			index = strings.Index(sectionName, "=")
-			value := string(sectionName[index+1:])
-			contextualUi.Regex, err = regexp.Compile(regexp.QuoteMeta(value))
-			if err != nil {
-				return err
-			}
-		default:
-			return fmt.Errorf("Invalid Ui Context regex in %s", sectionName)
-		}
-
-		switch sectionName[3:index] {
-		case "account":
-			contextualUi.ContextType = UI_CONTEXT_ACCOUNT
-		case "folder":
-			contextualUi.ContextType = UI_CONTEXT_FOLDER
-		case "subject":
-			contextualUi.ContextType = UI_CONTEXT_SUBJECT
-		default:
-			return fmt.Errorf("Unknown Contextual Ui Section: %s", sectionName)
-		}
-		config.ContextualUis = append(config.ContextualUis, contextualUi)
-	}
 	if triggers, err := file.GetSection("triggers"); err == nil {
 		if err := triggers.MapTo(&config.Triggers); err != nil {
 			return err
@@ -396,11 +269,8 @@ func (config *AercConfig) LoadConfig(file *ini.File) error {
 		}
 	}
 
-	// append default paths to template-dirs and styleset-dirs
+	// append default paths to template-dirs
 	for _, dir := range SearchDirs {
-		config.Ui.StyleSetDirs = append(
-			config.Ui.StyleSetDirs, path.Join(dir, "stylesets"),
-		)
 		config.Templates.TemplateDirs = append(
 			config.Templates.TemplateDirs, path.Join(dir, "templates"),
 		)
@@ -418,82 +288,6 @@ func (config *AercConfig) LoadConfig(file *ini.File) error {
 	if err := templates.CheckTemplate(t.Forwards, t.TemplateDirs); err != nil {
 		return err
 	}
-	if err := config.Ui.loadStyleSet(
-		config.Ui.StyleSetDirs); err != nil {
-		return err
-	}
-
-	for idx, contextualUi := range config.ContextualUis {
-		if contextualUi.UiConfig.StyleSetName == "" &&
-			len(contextualUi.UiConfig.StyleSetDirs) == 0 {
-			continue // no need to do anything if nothing is overridden
-		}
-		// fill in the missing part from the base
-		if contextualUi.UiConfig.StyleSetName == "" {
-			config.ContextualUis[idx].UiConfig.StyleSetName = config.Ui.StyleSetName
-		} else if len(contextualUi.UiConfig.StyleSetDirs) == 0 {
-			config.ContextualUis[idx].UiConfig.StyleSetDirs = config.Ui.StyleSetDirs
-		}
-		// since at least one of them has changed, load the styleset
-		if err := config.ContextualUis[idx].UiConfig.loadStyleSet(
-			config.ContextualUis[idx].UiConfig.StyleSetDirs); err != nil {
-			return err
-		}
-	}
-
-	return nil
-}
-
-func parseUiConfig(section *ini.Section, config *UIConfig) error {
-	if err := section.MapTo(config); err != nil {
-		return err
-	}
-
-	if key, err := section.GetKey("border-char-vertical"); err == nil {
-		chars := []rune(key.String())
-		if len(chars) != 1 {
-			return fmt.Errorf("%v must be one and only one character", key)
-		}
-		config.BorderCharVertical = chars[0]
-	}
-	if key, err := section.GetKey("border-char-horizontal"); err == nil {
-		chars := []rune(key.String())
-		if len(chars) != 1 {
-			return fmt.Errorf("%v must be one and only one character", key)
-		}
-		config.BorderCharHorizontal = chars[0]
-	}
-
-	// Values with type=time.Duration must be explicitly set. If these
-	// values are given a default in the struct passed to ui.MapTo, which
-	// they are, a zero-value in the config won't overwrite the default.
-	if key, err := section.GetKey("dirlist-delay"); err == nil {
-		dur, err := key.Duration()
-		if err != nil {
-			return err
-		}
-		config.DirListDelay = dur
-	}
-	if key, err := section.GetKey("completion-delay"); err == nil {
-		dur, err := key.Duration()
-		if err != nil {
-			return err
-		}
-		config.CompletionDelay = dur
-	}
-
-	if config.MessageViewTimestampFormat == "" {
-		config.MessageViewTimestampFormat = config.TimestampFormat
-	}
-	if config.MessageViewThisDayTimeFormat == "" {
-		config.MessageViewThisDayTimeFormat = config.TimestampFormat
-	}
-	if config.MessageViewThisWeekTimeFormat == "" {
-		config.MessageViewThisWeekTimeFormat = config.TimestampFormat
-	}
-	if config.MessageViewThisDayTimeFormat == "" {
-		config.MessageViewThisDayTimeFormat = config.TimestampFormat
-	}
 
 	return nil
 }
@@ -547,47 +341,7 @@ func LoadConfigFromFile(root *string, accts []string) (*AercConfig, error) {
 			UnsafeAccountsConf: false,
 		},
 
-		Ui: UIConfig{
-			AutoMarkRead:       true,
-			IndexFormat:        "%-20.20D %-17.17n %Z %s",
-			TimestampFormat:    "2006-01-02 03:04 PM",
-			ThisDayTimeFormat:  "",
-			ThisWeekTimeFormat: "",
-			ThisYearTimeFormat: "",
-			ShowHeaders: []string{
-				"From", "To", "Cc", "Bcc", "Subject", "Date",
-			},
-			RenderAccountTabs:   "auto",
-			PinnedTabMarker:     "`",
-			SidebarWidth:        20,
-			PreviewHeight:       12,
-			EmptyMessage:        "(no messages)",
-			EmptyDirlist:        "(no folders)",
-			MouseEnabled:        false,
-			ClientThreadsDelay:  50 * time.Millisecond,
-			NewMessageBell:      true,
-			FuzzyComplete:       false,
-			Spinner:             "[..]    , [..]   ,  [..]  ,   [..] ,    [..],   [..] ,  [..]  , [..]   ",
-			SpinnerDelimiter:    ",",
-			IconUnencrypted:     "",
-			IconSigned:          "[s]",
-			IconEncrypted:       "[e]",
-			IconSignedEncrypted: "",
-			IconUnknown:         "[s?]",
-			IconInvalid:         "[s!]",
-			DirListFormat:       "%n %>r",
-			DirListDelay:        200 * time.Millisecond,
-			NextMessageOnDelete: true,
-			CompletionDelay:     250 * time.Millisecond,
-			CompletionMinChars:  1,
-			CompletionPopovers:  true,
-			StyleSetDirs:        []string{},
-			StyleSetName:        "default",
-			// border defaults
-			BorderCharVertical:   ' ',
-			BorderCharHorizontal: ' ',
-		},
-
+		Ui:            defaultUiConfig(),
 		ContextualUis: []UIConfigContext{},
 
 		Viewer: ViewerConfig{
@@ -630,6 +384,9 @@ func LoadConfigFromFile(root *string, accts []string) (*AercConfig, error) {
 	if err = config.LoadConfig(file); err != nil {
 		return nil, err
 	}
+	if err := config.parseUi(file); err != nil {
+		return nil, err
+	}
 
 	if ui, err := file.GetSection("general"); err == nil {
 		if err := ui.MapTo(&config.General); err != nil {
@@ -641,7 +398,6 @@ func LoadConfigFromFile(root *string, accts []string) (*AercConfig, error) {
 	}
 
 	logging.Debugf("aerc.conf: [general] %#v", config.General)
-	logging.Debugf("aerc.conf: [ui] %#v", config.Ui)
 	logging.Debugf("aerc.conf: [statusline] %#v", config.Statusline)
 	logging.Debugf("aerc.conf: [viewer] %#v", config.Viewer)
 	logging.Debugf("aerc.conf: [compose] %#v", config.Compose)
@@ -669,73 +425,6 @@ func parseLayout(layout string) [][]string {
 	return l
 }
 
-func (ui *UIConfig) loadStyleSet(styleSetDirs []string) error {
-	ui.style = NewStyleSet()
-	err := ui.style.LoadStyleSet(ui.StyleSetName, styleSetDirs)
-	if err != nil {
-		return fmt.Errorf("Unable to load default styleset: %w", err)
-	}
-
-	return nil
-}
-
-func (config AercConfig) mergeContextualUi(baseUi UIConfig,
-	contextType ContextType, s string,
-) UIConfig {
-	for _, contextualUi := range config.ContextualUis {
-		if contextualUi.ContextType != contextType {
-			continue
-		}
-
-		if !contextualUi.Regex.Match([]byte(s)) {
-			continue
-		}
-
-		err := mergo.Merge(&baseUi, contextualUi.UiConfig, mergo.WithOverride)
-		if err != nil {
-			logging.Warnf("merge ui failed: %v", err)
-		}
-		if contextualUi.UiConfig.StyleSetName != "" {
-			baseUi.style = contextualUi.UiConfig.style
-		}
-		return baseUi
-	}
-
-	return baseUi
-}
-
-func (config AercConfig) GetUiConfig(params map[ContextType]string) *UIConfig {
-	baseUi := config.Ui
-
-	for k, v := range params {
-		baseUi = config.mergeContextualUi(baseUi, k, v)
-	}
-
-	return &baseUi
-}
-
-func (config *AercConfig) GetContextualUIConfigs() []UIConfigContext {
-	return config.ContextualUis
-}
-
-func (uiConfig UIConfig) GetStyle(so StyleObject) tcell.Style {
-	return uiConfig.style.Get(so)
-}
-
-func (uiConfig UIConfig) GetStyleSelected(so StyleObject) tcell.Style {
-	return uiConfig.style.Selected(so)
-}
-
-func (uiConfig UIConfig) GetComposedStyle(base StyleObject,
-	styles []StyleObject,
-) tcell.Style {
-	return uiConfig.style.Compose(base, styles)
-}
-
-func (uiConfig UIConfig) GetComposedStyleSelected(base StyleObject, styles []StyleObject) tcell.Style {
-	return uiConfig.style.ComposeSelected(base, styles)
-}
-
 func contains(list []string, v string) bool {
 	for _, item := range list {
 		if item == v {
diff --git a/config/ui.go b/config/ui.go
new file mode 100644
index 00000000..16a296df
--- /dev/null
+++ b/config/ui.go
@@ -0,0 +1,340 @@
+package config
+
+import (
+	"fmt"
+	"path"
+	"regexp"
+	"strings"
+	"time"
+
+	"git.sr.ht/~rjarry/aerc/logging"
+	"github.com/gdamore/tcell/v2"
+	"github.com/go-ini/ini"
+	"github.com/imdario/mergo"
+)
+
+type UIConfig struct {
+	AutoMarkRead                  bool          `ini:"auto-mark-read"`
+	IndexFormat                   string        `ini:"index-format"`
+	TimestampFormat               string        `ini:"timestamp-format"`
+	ThisDayTimeFormat             string        `ini:"this-day-time-format"`
+	ThisWeekTimeFormat            string        `ini:"this-week-time-format"`
+	ThisYearTimeFormat            string        `ini:"this-year-time-format"`
+	MessageViewTimestampFormat    string        `ini:"message-view-timestamp-format"`
+	MessageViewThisDayTimeFormat  string        `ini:"message-view-this-day-time-format"`
+	MessageViewThisWeekTimeFormat string        `ini:"message-view-this-week-time-format"`
+	MessageViewThisYearTimeFormat string        `ini:"message-view-this-year-time-format"`
+	ShowHeaders                   []string      `delim:","`
+	RenderAccountTabs             string        `ini:"render-account-tabs"`
+	PinnedTabMarker               string        `ini:"pinned-tab-marker"`
+	SidebarWidth                  int           `ini:"sidebar-width"`
+	PreviewHeight                 int           `ini:"preview-height"`
+	EmptyMessage                  string        `ini:"empty-message"`
+	EmptyDirlist                  string        `ini:"empty-dirlist"`
+	MouseEnabled                  bool          `ini:"mouse-enabled"`
+	ThreadingEnabled              bool          `ini:"threading-enabled"`
+	ForceClientThreads            bool          `ini:"force-client-threads"`
+	ClientThreadsDelay            time.Duration `ini:"client-threads-delay"`
+	FuzzyComplete                 bool          `ini:"fuzzy-complete"`
+	NewMessageBell                bool          `ini:"new-message-bell"`
+	Spinner                       string        `ini:"spinner"`
+	SpinnerDelimiter              string        `ini:"spinner-delimiter"`
+	IconUnencrypted               string        `ini:"icon-unencrypted"`
+	IconEncrypted                 string        `ini:"icon-encrypted"`
+	IconSigned                    string        `ini:"icon-signed"`
+	IconSignedEncrypted           string        `ini:"icon-signed-encrypted"`
+	IconUnknown                   string        `ini:"icon-unknown"`
+	IconInvalid                   string        `ini:"icon-invalid"`
+	DirListFormat                 string        `ini:"dirlist-format"`
+	DirListDelay                  time.Duration `ini:"dirlist-delay"`
+	DirListTree                   bool          `ini:"dirlist-tree"`
+	DirListCollapse               int           `ini:"dirlist-collapse"`
+	Sort                          []string      `delim:" "`
+	NextMessageOnDelete           bool          `ini:"next-message-on-delete"`
+	CompletionDelay               time.Duration `ini:"completion-delay"`
+	CompletionMinChars            int           `ini:"completion-min-chars"`
+	CompletionPopovers            bool          `ini:"completion-popovers"`
+	StyleSetDirs                  []string      `ini:"stylesets-dirs" delim:":"`
+	StyleSetName                  string        `ini:"styleset-name"`
+	style                         StyleSet
+	// customize border appearance
+	BorderCharVertical   rune `ini:"-"`
+	BorderCharHorizontal rune `ini:"-"`
+
+	ReverseOrder       bool `ini:"reverse-msglist-order"`
+	ReverseThreadOrder bool `ini:"reverse-thread-order"`
+	SortThreadSiblings bool `ini:"sort-thread-siblings"`
+}
+
+type ContextType int
+
+const (
+	UI_CONTEXT_FOLDER ContextType = iota
+	UI_CONTEXT_ACCOUNT
+	UI_CONTEXT_SUBJECT
+	BIND_CONTEXT_ACCOUNT
+	BIND_CONTEXT_FOLDER
+)
+
+type UIConfigContext struct {
+	ContextType ContextType
+	Regex       *regexp.Regexp
+	UiConfig    UIConfig
+}
+
+func defaultUiConfig() UIConfig {
+	return UIConfig{
+		AutoMarkRead:       true,
+		IndexFormat:        "%-20.20D %-17.17n %Z %s",
+		TimestampFormat:    "2006-01-02 03:04 PM",
+		ThisDayTimeFormat:  "",
+		ThisWeekTimeFormat: "",
+		ThisYearTimeFormat: "",
+		ShowHeaders: []string{
+			"From", "To", "Cc", "Bcc", "Subject", "Date",
+		},
+		RenderAccountTabs:   "auto",
+		PinnedTabMarker:     "`",
+		SidebarWidth:        20,
+		PreviewHeight:       12,
+		EmptyMessage:        "(no messages)",
+		EmptyDirlist:        "(no folders)",
+		MouseEnabled:        false,
+		ClientThreadsDelay:  50 * time.Millisecond,
+		NewMessageBell:      true,
+		FuzzyComplete:       false,
+		Spinner:             "[..]    , [..]   ,  [..]  ,   [..] ,    [..],   [..] ,  [..]  , [..]   ",
+		SpinnerDelimiter:    ",",
+		IconUnencrypted:     "",
+		IconSigned:          "[s]",
+		IconEncrypted:       "[e]",
+		IconSignedEncrypted: "",
+		IconUnknown:         "[s?]",
+		IconInvalid:         "[s!]",
+		DirListFormat:       "%n %>r",
+		DirListDelay:        200 * time.Millisecond,
+		NextMessageOnDelete: true,
+		CompletionDelay:     250 * time.Millisecond,
+		CompletionMinChars:  1,
+		CompletionPopovers:  true,
+		StyleSetDirs:        []string{},
+		StyleSetName:        "default",
+		// border defaults
+		BorderCharVertical:   ' ',
+		BorderCharHorizontal: ' ',
+	}
+}
+
+func (config *AercConfig) parseUi(file *ini.File) error {
+	if ui, err := file.GetSection("ui"); err == nil {
+		if err := config.Ui.parse(ui); err != nil {
+			return err
+		}
+	}
+
+	for _, sectionName := range file.SectionStrings() {
+		if !strings.Contains(sectionName, "ui:") {
+			continue
+		}
+
+		uiSection, err := file.GetSection(sectionName)
+		if err != nil {
+			return err
+		}
+		uiSubConfig := UIConfig{}
+		if err := uiSubConfig.parse(uiSection); err != nil {
+			return err
+		}
+		contextualUi := UIConfigContext{
+			UiConfig: uiSubConfig,
+		}
+
+		var index int
+		switch {
+		case strings.Contains(sectionName, "~"):
+			index = strings.Index(sectionName, "~")
+			regex := string(sectionName[index+1:])
+			contextualUi.Regex, err = regexp.Compile(regex)
+			if err != nil {
+				return err
+			}
+		case strings.Contains(sectionName, "="):
+			index = strings.Index(sectionName, "=")
+			value := string(sectionName[index+1:])
+			contextualUi.Regex, err = regexp.Compile(regexp.QuoteMeta(value))
+			if err != nil {
+				return err
+			}
+		default:
+			return fmt.Errorf("Invalid Ui Context regex in %s", sectionName)
+		}
+
+		switch sectionName[3:index] {
+		case "account":
+			contextualUi.ContextType = UI_CONTEXT_ACCOUNT
+		case "folder":
+			contextualUi.ContextType = UI_CONTEXT_FOLDER
+		case "subject":
+			contextualUi.ContextType = UI_CONTEXT_SUBJECT
+		default:
+			return fmt.Errorf("Unknown Contextual Ui Section: %s", sectionName)
+		}
+		config.ContextualUis = append(config.ContextualUis, contextualUi)
+	}
+
+	// append default paths to styleset-dirs
+	for _, dir := range SearchDirs {
+		config.Ui.StyleSetDirs = append(
+			config.Ui.StyleSetDirs, path.Join(dir, "stylesets"),
+		)
+	}
+
+	if err := config.Ui.loadStyleSet(config.Ui.StyleSetDirs); err != nil {
+		return err
+	}
+
+	for idx, contextualUi := range config.ContextualUis {
+		if contextualUi.UiConfig.StyleSetName == "" &&
+			len(contextualUi.UiConfig.StyleSetDirs) == 0 {
+			continue // no need to do anything if nothing is overridden
+		}
+		// fill in the missing part from the base
+		if contextualUi.UiConfig.StyleSetName == "" {
+			config.ContextualUis[idx].UiConfig.StyleSetName = config.Ui.StyleSetName
+		} else if len(contextualUi.UiConfig.StyleSetDirs) == 0 {
+			config.ContextualUis[idx].UiConfig.StyleSetDirs = config.Ui.StyleSetDirs
+		}
+		// since at least one of them has changed, load the styleset
+		if err := config.ContextualUis[idx].UiConfig.loadStyleSet(
+			config.ContextualUis[idx].UiConfig.StyleSetDirs); err != nil {
+			return err
+		}
+	}
+
+	logging.Debugf("aerc.conf: [ui] %#v", config.Ui)
+
+	return nil
+}
+
+func (config *UIConfig) parse(section *ini.Section) error {
+	if err := section.MapTo(config); err != nil {
+		return err
+	}
+
+	if key, err := section.GetKey("border-char-vertical"); err == nil {
+		chars := []rune(key.String())
+		if len(chars) != 1 {
+			return fmt.Errorf("%v must be one and only one character", key)
+		}
+		config.BorderCharVertical = chars[0]
+	}
+	if key, err := section.GetKey("border-char-horizontal"); err == nil {
+		chars := []rune(key.String())
+		if len(chars) != 1 {
+			return fmt.Errorf("%v must be one and only one character", key)
+		}
+		config.BorderCharHorizontal = chars[0]
+	}
+
+	// Values with type=time.Duration must be explicitly set. If these
+	// values are given a default in the struct passed to ui.MapTo, which
+	// they are, a zero-value in the config won't overwrite the default.
+	if key, err := section.GetKey("dirlist-delay"); err == nil {
+		dur, err := key.Duration()
+		if err != nil {
+			return err
+		}
+		config.DirListDelay = dur
+	}
+	if key, err := section.GetKey("completion-delay"); err == nil {
+		dur, err := key.Duration()
+		if err != nil {
+			return err
+		}
+		config.CompletionDelay = dur
+	}
+
+	if config.MessageViewTimestampFormat == "" {
+		config.MessageViewTimestampFormat = config.TimestampFormat
+	}
+	if config.MessageViewThisDayTimeFormat == "" {
+		config.MessageViewThisDayTimeFormat = config.TimestampFormat
+	}
+	if config.MessageViewThisWeekTimeFormat == "" {
+		config.MessageViewThisWeekTimeFormat = config.TimestampFormat
+	}
+	if config.MessageViewThisDayTimeFormat == "" {
+		config.MessageViewThisDayTimeFormat = config.TimestampFormat
+	}
+
+	return nil
+}
+
+func (ui *UIConfig) loadStyleSet(styleSetDirs []string) error {
+	ui.style = NewStyleSet()
+	err := ui.style.LoadStyleSet(ui.StyleSetName, styleSetDirs)
+	if err != nil {
+		return fmt.Errorf("Unable to load default styleset: %w", err)
+	}
+
+	return nil
+}
+
+func (config *AercConfig) mergeContextualUi(baseUi UIConfig,
+	contextType ContextType, s string,
+) UIConfig {
+	for _, contextualUi := range config.ContextualUis {
+		if contextualUi.ContextType != contextType {
+			continue
+		}
+
+		if !contextualUi.Regex.Match([]byte(s)) {
+			continue
+		}
+
+		err := mergo.Merge(&baseUi, contextualUi.UiConfig, mergo.WithOverride)
+		if err != nil {
+			logging.Warnf("merge ui failed: %v", err)
+		}
+		if contextualUi.UiConfig.StyleSetName != "" {
+			baseUi.style = contextualUi.UiConfig.style
+		}
+		return baseUi
+	}
+
+	return baseUi
+}
+
+func (uiConfig *UIConfig) GetStyle(so StyleObject) tcell.Style {
+	return uiConfig.style.Get(so)
+}
+
+func (uiConfig *UIConfig) GetStyleSelected(so StyleObject) tcell.Style {
+	return uiConfig.style.Selected(so)
+}
+
+func (uiConfig *UIConfig) GetComposedStyle(base StyleObject,
+	styles []StyleObject,
+) tcell.Style {
+	return uiConfig.style.Compose(base, styles)
+}
+
+func (uiConfig *UIConfig) GetComposedStyleSelected(
+	base StyleObject, styles []StyleObject,
+) tcell.Style {
+	return uiConfig.style.ComposeSelected(base, styles)
+}
+
+func (config *AercConfig) GetUiConfig(params map[ContextType]string) *UIConfig {
+	baseUi := config.Ui
+
+	for k, v := range params {
+		baseUi = config.mergeContextualUi(baseUi, k, v)
+	}
+
+	return &baseUi
+}
+
+func (config *AercConfig) GetContextualUIConfigs() []UIConfigContext {
+	return config.ContextualUis
+}