statusline: refactor to make it more customizable

Refactor statusline by clearly separating the rendering part from the
text display. Use printf-like format string for statusline
customization.

Document printf-like format string to customize the statusline.

Allow to completely mute the statusline (except for push notifications)
with a format specifier.

Provide a display mode with unicode icons for the status elements.

Implements: https://todo.sr.ht/~rjarry/aerc/34
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

8 files changed, 407 insertions, 93 deletions

diff --git a/config/aerc.conf b/config/aerc.conf
index 1ad7ce5a..458f6359 100644
--- a/config/aerc.conf
+++ b/config/aerc.conf
@@ -139,6 +139,23 @@ styleset-name=default
 # Default: false
 #threading-enabled=false
 
+[statusline]
+# Describes the format string for the statusline.
+#
+# Default: [%a] %S %>%T
+render-format=[%a] %S %>%T
+
+# Specifies the separator between grouped statusline elements.
+#
+# Default: " | "
+# separator=
+
+# Defines the mode for displaying the status elements.
+# Options: text, icon
+#
+# Default: text
+# display-mode=
+
 [viewer]
 #
 # Specifies the pager to use when displaying emails. Note that some filters
diff --git a/config/config.go b/config/config.go
index f8b2f650..8eeea100 100644
--- a/config/config.go
+++ b/config/config.go
@@ -147,6 +147,12 @@ type ViewerConfig struct {
 	KeyPassthrough bool       `ini:"-"`
 }
 
+type StatuslineConfig struct {
+	RenderFormat string `ini:"render-format"`
+	Separator    string
+	DisplayMode  string `ini:"display-mode"`
+}
+
 type TriggersConfig struct {
 	NewEmail       string `ini:"new-email"`
 	ExecuteCommand func(command []string) error
@@ -163,11 +169,12 @@ type AercConfig struct {
 	Bindings        BindingConfig
 	ContextualBinds []BindingConfigContext
 	Compose         ComposeConfig
-	Ini             *ini.File       `ini:"-"`
-	Accounts        []AccountConfig `ini:"-"`
-	Filters         []FilterConfig  `ini:"-"`
-	Viewer          ViewerConfig    `ini:"-"`
-	Triggers        TriggersConfig  `ini:"-"`
+	Ini             *ini.File        `ini:"-"`
+	Accounts        []AccountConfig  `ini:"-"`
+	Filters         []FilterConfig   `ini:"-"`
+	Viewer          ViewerConfig     `ini:"-"`
+	Statusline      StatuslineConfig `ini:"-"`
+	Triggers        TriggersConfig   `ini:"-"`
 	Ui              UIConfig
 	ContextualUis   []UIConfigContext
 	General         GeneralConfig
@@ -410,6 +417,11 @@ func (config *AercConfig) LoadConfig(file *ini.File) error {
 			}
 		}
 	}
+	if statusline, err := file.GetSection("statusline"); err == nil {
+		if err := statusline.MapTo(&config.Statusline); err != nil {
+			return err
+		}
+	}
 	if compose, err := file.GetSection("compose"); err == nil {
 		if err := compose.MapTo(&config.Compose); err != nil {
 			return err
@@ -654,6 +666,12 @@ func LoadConfigFromFile(root *string, logger *log.Logger) (*AercConfig, error) {
 			},
 		},
 
+		Statusline: StatuslineConfig{
+			RenderFormat: "[%a] %S %>%T",
+			Separator:    " | ",
+			DisplayMode:  "",
+		},
+
 		Compose: ComposeConfig{
 			HeaderLayout: [][]string{
 				{"To", "From"},
diff --git a/doc/aerc-config.5.scd b/doc/aerc-config.5.scd
index 493fd715..b615629b 100644
--- a/doc/aerc-config.5.scd
+++ b/doc/aerc-config.5.scd
@@ -295,6 +295,52 @@ index-format=...
 index-format=...
 ```
 
+## STATUSLINE
+
+These options are configured in the *[statusline]* section of aerc.conf.
+
+*render-format*
+	Describes the format string for the statusline format.
+
+	For a minimal statusline that only shows the current account and
+	the connection information, use [%a] %c.
+
+	To completely mute the statusline (except for push notficiations), use
+	%m only.
+
+	Default: [%a] %S %>%T
+
+[- *Format specifier*
+:[ *Description*
+|  %%
+:  literal %
+|  %a
+:  active account name
+|  %d
+:  active directory name
+|  %c
+:  connection state
+|  %m
+:  mute statusline and show only push notifications
+|  %S
+:  general status information (e.g. connection state, filter, search)
+|  %T
+:  general on/off information (e.g. passthrough, threading, sorting)
+|  %>
+:  does not print anything but all format specifier that follow will be right justified. 
+
+*separator*
+	Specifies the separator between grouped statusline elements (e.g. for
+	the %S and %T specifiers in *render-format*).
+
+	Default: " | "
+
+*display-mode*
+	Defines the mode for displaying the status elements.
+	Options: text, icon
+
+	Default: text
+
 
 ## VIEWER
 
diff --git a/lib/statusline/folderstate.go b/lib/statusline/folderstate.go
deleted file mode 100644
index ff470b72..00000000
--- a/lib/statusline/folderstate.go
+++ /dev/null
@@ -1,32 +0,0 @@
-package statusline
-
-type folderState struct {
-	Search         string
-	Filter         string
-	FilterActivity string
-	Sorting        string
-
-	Threading string
-}
-
-func (fs *folderState) State() []string {
-	var line []string
-
-	if fs.FilterActivity != "" {
-		line = append(line, fs.FilterActivity)
-	} else {
-		if fs.Filter != "" {
-			line = append(line, fs.Filter)
-		}
-	}
-	if fs.Search != "" {
-		line = append(line, fs.Search)
-	}
-	if fs.Sorting != "" {
-		line = append(line, fs.Sorting)
-	}
-	if fs.Threading != "" {
-		line = append(line, fs.Threading)
-	}
-	return line
-}
diff --git a/lib/statusline/renderer.go b/lib/statusline/renderer.go
new file mode 100644
index 00000000..2ab05dd9
--- /dev/null
+++ b/lib/statusline/renderer.go
@@ -0,0 +1,194 @@
+package statusline
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"unicode"
+
+	"github.com/mattn/go-runewidth"
+)
+
+type renderParams struct {
+	width int
+	sep   string
+	acct  *accountState
+	fldr  *folderState
+}
+
+type renderFunc func(r renderParams) string
+
+func newRenderer(renderFormat, textMode string) renderFunc {
+	var texter Texter
+	switch strings.ToLower(textMode) {
+	case "icon":
+		texter = &icon{}
+	default:
+		texter = &text{}
+	}
+
+	return renderer(texter, renderFormat)
+}
+
+func renderer(texter Texter, renderFormat string) renderFunc {
+	var leftFmt, rightFmt string
+	if idx := strings.Index(renderFormat, "%>"); idx < 0 {
+		leftFmt = renderFormat
+	} else {
+		leftFmt, rightFmt = renderFormat[:idx], strings.Replace(renderFormat[idx:], "%>", "", 1)
+	}
+
+	return func(r renderParams) string {
+		lfmtStr, largs, err := parseStatuslineFormat(leftFmt, texter, r)
+		if err != nil {
+			return err.Error()
+		}
+		rfmtStr, rargs, err := parseStatuslineFormat(rightFmt, texter, r)
+		if err != nil {
+			return err.Error()
+		}
+		leftText, rightText := fmt.Sprintf(lfmtStr, largs...), fmt.Sprintf(rfmtStr, rargs...)
+		return runewidth.FillRight(leftText, r.width-len(rightText)-1) + rightText
+	}
+}
+
+func connectionInfo(acct *accountState, texter Texter) (conn string) {
+	if acct.ConnActivity != "" {
+		conn += acct.ConnActivity
+	} else {
+		if acct.Connected {
+			conn += texter.Connected()
+		} else {
+			conn += texter.Disconnected()
+		}
+	}
+	return
+}
+
+func contentInfo(acct *accountState, fldr *folderState, texter Texter) []string {
+	var status []string
+	if fldr.FilterActivity != "" {
+		status = append(status, fldr.FilterActivity)
+	} else {
+		if fldr.Filter != "" {
+			status = append(status, texter.FormatFilter(fldr.Filter))
+		}
+	}
+	if fldr.Search != "" {
+		status = append(status, texter.FormatSearch(fldr.Search))
+	}
+	return status
+}
+
+func trayInfo(acct *accountState, fldr *folderState, texter Texter) []string {
+	var tray []string
+	if fldr.Sorting {
+		tray = append(tray, texter.Sorting())
+	}
+	if fldr.Threading {
+		tray = append(tray, texter.Threading())
+	}
+	if acct.Passthrough {
+		tray = append(tray, texter.Passthrough())
+	}
+	return tray
+}
+
+func parseStatuslineFormat(format string, texter Texter, r renderParams) (string, []interface{}, error) {
+	retval := make([]byte, 0, len(format))
+	var args []interface{}
+	mute := false
+
+	var c rune
+	for i, ni := 0, 0; i < len(format); {
+		ni = strings.IndexByte(format[i:], '%')
+		if ni < 0 {
+			ni = len(format)
+			retval = append(retval, []byte(format[i:ni])...)
+			break
+		}
+		ni += i + 1
+		// Check for fmt flags
+		if ni == len(format) {
+			goto handle_end_error
+		}
+		c = rune(format[ni])
+		if c == '+' || c == '-' || c == '#' || c == ' ' || c == '0' {
+			ni++
+		}
+
+		// Check for precision and width
+		if ni == len(format) {
+			goto handle_end_error
+		}
+		c = rune(format[ni])
+		for unicode.IsDigit(c) {
+			ni++
+			c = rune(format[ni])
+		}
+		if c == '.' {
+			ni++
+			c = rune(format[ni])
+			for unicode.IsDigit(c) {
+				ni++
+				c = rune(format[ni])
+			}
+		}
+
+		retval = append(retval, []byte(format[i:ni])...)
+		// Get final format verb
+		if ni == len(format) {
+			goto handle_end_error
+		}
+		c = rune(format[ni])
+		switch c {
+		case '%':
+			retval = append(retval, '%')
+		case 'a':
+			retval = append(retval, 's')
+			args = append(args, r.acct.Name)
+		case 'c':
+			retval = append(retval, 's')
+			args = append(args, connectionInfo(r.acct, texter))
+		case 'd':
+			retval = append(retval, 's')
+			args = append(args, r.fldr.Name)
+		case 'm':
+			mute = true
+		case 'S':
+			var status []string
+			if conn := connectionInfo(r.acct, texter); conn != "" {
+				status = append(status, conn)
+			}
+
+			if r.acct.Connected {
+				status = append(status, contentInfo(r.acct, r.fldr, texter)...)
+			}
+			retval = append(retval, 's')
+			args = append(args, strings.Join(status, r.sep))
+		case 'T':
+			var tray []string
+			if r.acct.Connected {
+				tray = trayInfo(r.acct, r.fldr, texter)
+			}
+			retval = append(retval, 's')
+			args = append(args, strings.Join(tray, r.sep))
+		default:
+			// Just ignore it and print as is
+			// so %k in index format becomes %%k to Printf
+			retval = append(retval, '%')
+			retval = append(retval, byte(c))
+		}
+		i = ni + 1
+	}
+
+	if mute {
+		return "", nil, nil
+	}
+
+	return string(retval), args, nil
+
+handle_end_error:
+	return "", nil,
+		errors.New("reached end of string while parsing statusline format")
+}
diff --git a/lib/statusline/state.go b/lib/statusline/state.go
index 895bb2c4..3fecd0fe 100644
--- a/lib/statusline/state.go
+++ b/lib/statusline/state.go
@@ -2,76 +2,80 @@ package statusline
 
 import (
 	"fmt"
-	"strings"
+
+	"git.sr.ht/~rjarry/aerc/config"
 )
 
 type State struct {
-	Name      string
-	Multiple  bool
-	Separator string
+	separator string
+	renderer  renderFunc
+	acct      *accountState
+	fldr      map[string]*folderState
+	width     int
+}
 
-	Connection   string
+type accountState struct {
+	Name         string
+	Multiple     bool
 	ConnActivity string
 	Connected    bool
+	Passthrough  bool
+}
 
-	Passthrough string
-
-	fs map[string]*folderState
+type folderState struct {
+	Name           string
+	Search         string
+	Filter         string
+	FilterActivity string
+	Sorting        bool
+	Threading      bool
 }
 
-func NewState(name string, multipleAccts bool, sep string) *State {
-	return &State{Name: name, Multiple: multipleAccts, Separator: sep,
-		fs: make(map[string]*folderState)}
+func NewState(name string, multipleAccts bool, conf config.StatuslineConfig) *State {
+	return &State{separator: conf.Separator,
+		renderer: newRenderer(conf.RenderFormat, conf.DisplayMode),
+		acct:     &accountState{Name: name, Multiple: multipleAccts},
+		fldr:     make(map[string]*folderState),
+	}
 }
 
 func (s *State) StatusLine(folder string) string {
-	var line []string
-	if s.Connection != "" || s.ConnActivity != "" {
-		conn := s.Connection
-		if s.ConnActivity != "" {
-			conn = s.ConnActivity
-		}
-		if s.Multiple {
-			line = append(line, fmt.Sprintf("[%s] %s", s.Name, conn))
-		} else {
-			line = append(line, conn)
-		}
-	}
-	if s.Connected {
-		if s.Passthrough != "" {
-			line = append(line, s.Passthrough)
-		}
-		if folder != "" {
-			line = append(line, s.folderState(folder).State()...)
-		}
-	}
-	return strings.Join(line, s.Separator)
+	return s.renderer(renderParams{
+		width: s.width,
+		sep:   s.separator,
+		acct:  s.acct,
+		fldr:  s.folderState(folder),
+	})
 }
 
 func (s *State) folderState(folder string) *folderState {
-	if _, ok := s.fs[folder]; !ok {
-		s.fs[folder] = &folderState{}
+	if _, ok := s.fldr[folder]; !ok {
+		s.fldr[folder] = &folderState{Name: folder}
+	}
+	return s.fldr[folder]
+}
+
+func (s *State) SetWidth(w int) bool {
+	changeState := false
+	if s.width != w {
+		s.width = w
+		changeState = true
 	}
-	return s.fs[folder]
+	return changeState
 }
 
 type SetStateFunc func(s *State, folder string)
 
 func Connected(state bool) SetStateFunc {
 	return func(s *State, folder string) {
-		s.ConnActivity = ""
-		s.Connected = state
-		if state {
-			s.Connection = "Connected"
-		} else {
-			s.Connection = "Disconnected"
-		}
+		s.acct.ConnActivity = ""
+		s.acct.Connected = state
 	}
 }
 
 func ConnectionActivity(desc string) SetStateFunc {
 	return func(s *State, folder string) {
-		s.ConnActivity = desc
+		s.acct.ConnActivity = desc
 	}
 }
 
@@ -111,27 +115,18 @@ func Search(desc string) SetStateFunc {
 
 func Sorting(on bool) SetStateFunc {
 	return func(s *State, folder string) {
-		s.folderState(folder).Sorting = ""
-		if on {
-			s.folderState(folder).Sorting = "sorting"
-		}
+		s.folderState(folder).Sorting = on
 	}
 }
 
 func Threading(on bool) SetStateFunc {
 	return func(s *State, folder string) {
-		s.folderState(folder).Threading = ""
-		if on {
-			s.folderState(folder).Threading = "threading"
-		}
+		s.folderState(folder).Threading = on
 	}
 }
 
 func Passthrough(on bool) SetStateFunc {
 	return func(s *State, folder string) {
-		s.Passthrough = ""
-		if on {
-			s.Passthrough = "passthrough"
-		}
+		s.acct.Passthrough = on
 	}
 }
diff --git a/lib/statusline/texter.go b/lib/statusline/texter.go
new file mode 100644
index 00000000..d06b1982
--- /dev/null
+++ b/lib/statusline/texter.go
@@ -0,0 +1,73 @@
+package statusline
+
+import "strings"
+
+type Texter interface {
+	Connected() string
+	Disconnected() string
+	Passthrough() string
+	Sorting() string
+	Threading() string
+	FormatFilter(string) string
+	FormatSearch(string) string
+}
+
+type text struct{}
+
+func (t text) Connected() string {
+	return "Connected"
+}
+
+func (t text) Disconnected() string {
+	return "Disconnected"
+}
+
+func (t text) Passthrough() string {
+	return "passthrough"
+}
+
+func (t text) Sorting() string {
+	return "sorting"
+}
+
+func (t text) Threading() string {
+	return "threading"
+}
+
+func (t text) FormatFilter(s string) string {
+	return s
+}
+
+func (t text) FormatSearch(s string) string {
+	return s
+}
+
+type icon struct{}
+
+func (i icon) Connected() string {
+	return "✓"
+}
+
+func (i icon) Disconnected() string {
+	return "✘"
+}
+
+func (i icon) Passthrough() string {
+	return "➔"
+}
+
+func (i icon) Sorting() string {
+	return "⚙"
+}
+
+func (i icon) Threading() string {
+	return "🧵"
+}
+
+func (i icon) FormatFilter(s string) string {
+	return strings.ReplaceAll(s, "filter", "🔦")
+}
+
+func (i icon) FormatSearch(s string) string {
+	return strings.ReplaceAll(s, "search", "🔎")
+}
diff --git a/widgets/account.go b/widgets/account.go
index 994bba6e..b34396bd 100644
--- a/widgets/account.go
+++ b/widgets/account.go
@@ -59,7 +59,7 @@ func NewAccountView(aerc *Aerc, conf *config.AercConfig, acct *config.AccountCon
 		conf:   conf,
 		host:   host,
 		logger: logger,
-		state:  statusline.NewState(acct.Name, len(conf.Accounts) > 1, " | "),
+		state:  statusline.NewState(acct.Name, len(conf.Accounts) > 1, conf.Statusline),
 	}
 
 	view.grid = ui.NewGrid().Rows([]ui.GridSpec{
@@ -170,6 +170,9 @@ func (acct *AccountView) Invalidate() {
 }
 
 func (acct *AccountView) Draw(ctx *ui.Context) {
+	if acct.state.SetWidth(ctx.Width()) {
+		acct.UpdateStatus()
+	}
 	acct.grid.Draw(ctx)
 }