styleset: allow dynamic msglist styling

Add support for dynamic msglist*.$HEADER,$VALUE.$ATTR = $VALUE where
$VALUE can be either a fixed string or a regular expression. This is
intended as a replacement of contextual ui sections based on subject
values.

Implements: https://todo.sr.ht/~rjarry/aerc/18
Signed-off-by: Robin Jarry <robin@jarry.cc>
Tested-by: Bence Ferdinandy <bence@ferdinandy.com>

5 files changed, 134 insertions, 33 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e2d7ba47..f126d485 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Allow configuring URL handlers via `x-scheme-handler/<scheme>` `[openers]` in
   `aerc.conf`.
 - Allow basic shell globbing in `[openers]` MIME types.
+- Dynamic `msglist_*` styling based on email header values in stylesets.
 
 ### Changed
 
diff --git a/config/style.go b/config/style.go
index c8134585..79bd69d1 100644
--- a/config/style.go
+++ b/config/style.go
@@ -9,6 +9,7 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/emersion/go-message/mail"
 	"github.com/gdamore/tcell/v2"
 	"github.com/go-ini/ini"
 	"github.com/mitchellh/go-homedir"
@@ -107,6 +108,9 @@ type Style struct {
 	Reverse   bool
 	Italic    bool
 	Dim       bool
+	header    string         // only for msglist
+	pattern   string         // only for msglist
+	re        *regexp.Regexp // only for msglist
 }
 
 func (s Style) Get() tcell.Style {
@@ -251,40 +255,64 @@ func (s Style) composeWith(styles []*Style) Style {
 	return newStyle
 }
 
+type StyleConf struct {
+	base    Style
+	dynamic []Style
+}
+
 type StyleSet struct {
-	objects  map[StyleObject]*Style
-	selected map[StyleObject]*Style
+	objects  map[StyleObject]*StyleConf
+	selected map[StyleObject]*StyleConf
 	user     map[string]*Style
 	path     string
 }
 
 func NewStyleSet() StyleSet {
 	ss := StyleSet{
-		objects:  make(map[StyleObject]*Style),
-		selected: make(map[StyleObject]*Style),
+		objects:  make(map[StyleObject]*StyleConf),
+		selected: make(map[StyleObject]*StyleConf),
 		user:     make(map[string]*Style),
 	}
 	for _, so := range StyleNames {
-		ss.objects[so] = new(Style)
-		ss.selected[so] = new(Style)
+		ss.objects[so] = new(StyleConf)
+		ss.selected[so] = new(StyleConf)
 	}
-
 	return ss
 }
 
 func (ss StyleSet) reset() {
 	for _, so := range StyleNames {
-		ss.objects[so].Reset()
-		ss.selected[so].Reset()
+		ss.objects[so].base.Reset()
+		for _, d := range ss.objects[so].dynamic {
+			d.Reset()
+		}
+		ss.selected[so].base.Reset()
+		for _, d := range ss.selected[so].dynamic {
+			d.Reset()
+		}
 	}
 }
 
-func (ss StyleSet) Get(so StyleObject) tcell.Style {
-	return ss.objects[so].Get()
+func (c *StyleConf) getStyle(h *mail.Header) *Style {
+	if h == nil {
+		return &c.base
+	}
+	for _, s := range c.dynamic {
+		val, _ := h.Text(s.header)
+		if s.re.MatchString(val) {
+			s = c.base.composeWith([]*Style{&s})
+			return &s
+		}
+	}
+	return &c.base
+}
+
+func (ss StyleSet) Get(so StyleObject, h *mail.Header) tcell.Style {
+	return ss.objects[so].getStyle(h).Get()
 }
 
-func (ss StyleSet) Selected(so StyleObject) tcell.Style {
-	return ss.selected[so].Get()
+func (ss StyleSet) Selected(so StyleObject, h *mail.Header) tcell.Style {
+	return ss.selected[so].getStyle(h).Get()
 }
 
 func (ss StyleSet) UserStyle(name string) tcell.Style {
@@ -294,23 +322,25 @@ func (ss StyleSet) UserStyle(name string) tcell.Style {
 	return tcell.StyleDefault
 }
 
-func (ss StyleSet) Compose(so StyleObject, sos []StyleObject) tcell.Style {
-	base := *ss.objects[so]
+func (ss StyleSet) Compose(
+	so StyleObject, sos []StyleObject, h *mail.Header,
+) tcell.Style {
+	base := *ss.objects[so].getStyle(h)
 	styles := make([]*Style, len(sos))
 	for i, so := range sos {
-		styles[i] = ss.objects[so]
+		styles[i] = ss.objects[so].getStyle(h)
 	}
 
 	return base.composeWith(styles).Get()
 }
 
-func (ss StyleSet) ComposeSelected(so StyleObject,
-	sos []StyleObject,
+func (ss StyleSet) ComposeSelected(
+	so StyleObject, sos []StyleObject, h *mail.Header,
 ) tcell.Style {
-	base := *ss.selected[so]
+	base := *ss.selected[so].getStyle(h)
 	styles := make([]*Style, len(sos))
 	for i, so := range sos {
-		styles[i] = ss.selected[so]
+		styles[i] = ss.selected[so].getStyle(h)
 	}
 
 	return base.composeWith(styles).Get()
@@ -386,17 +416,18 @@ func (ss *StyleSet) ParseStyleSet(file *ini.File) error {
 	return nil
 }
 
-var styleObjRe = regexp.MustCompile(`^([\w\*\?]+)(\.selected)?\.(\w+)$`)
+var styleObjRe = regexp.MustCompile(`^([\w\*\?]+)(?:\.([\w-]+),(.+?))?(\.selected)?\.(\w+)$`)
 
 func (ss *StyleSet) parseKey(key *ini.Key, selected bool) error {
 	groups := styleObjRe.FindStringSubmatch(key.Name())
 	if groups == nil {
 		return errors.New("invalid style syntax: " + key.Name())
 	}
-	if groups[2] == ".selected" && !selected {
+	if groups[4] == ".selected" && !selected {
 		return nil
 	}
-	obj, attr := groups[1], groups[3]
+	obj, attr := groups[1], groups[5]
+	header, pattern := groups[2], groups[3]
 
 	objRe, err := fnmatchToRegex(obj)
 	if err != nil {
@@ -408,12 +439,12 @@ func (ss *StyleSet) parseKey(key *ini.Key, selected bool) error {
 			continue
 		}
 		if !selected {
-			err = ss.objects[so].Set(attr, key.Value())
+			err = ss.objects[so].update(header, pattern, attr, key.Value())
 			if err != nil {
 				return err
 			}
 		}
-		err = ss.selected[so].Set(attr, key.Value())
+		err = ss.selected[so].update(header, pattern, attr, key.Value())
 		if err != nil {
 			return err
 		}
@@ -425,6 +456,37 @@ func (ss *StyleSet) parseKey(key *ini.Key, selected bool) error {
 	return nil
 }
 
+func (c *StyleConf) update(header, pattern, attr, val string) error {
+	if header == "" || pattern == "" {
+		return (&c.base).Set(attr, val)
+	}
+	for i := range c.dynamic {
+		s := &c.dynamic[i]
+		if s.header == header && s.pattern == pattern {
+			return s.Set(attr, val)
+		}
+	}
+	if strings.HasPrefix(pattern, "~") {
+		pattern = pattern[1:]
+	} else {
+		pattern = "^" + regexp.QuoteMeta(pattern) + "$"
+	}
+	re, err := regexp.Compile(pattern)
+	if err != nil {
+		return err
+	}
+	var s Style
+	err = (&s).Set(attr, val)
+	if err != nil {
+		return err
+	}
+	s.header = header
+	s.pattern = pattern
+	s.re = re
+	c.dynamic = append(c.dynamic, s)
+	return nil
+}
+
 func (ss *StyleSet) LoadStyleSet(stylesetName string, stylesetDirs []string) error {
 	filepath, err := findStyleSet(stylesetName, stylesetDirs)
 	if err != nil {
diff --git a/config/ui.go b/config/ui.go
index c67502da..56a59e74 100644
--- a/config/ui.go
+++ b/config/ui.go
@@ -11,6 +11,7 @@ import (
 
 	"git.sr.ht/~rjarry/aerc/lib/templates"
 	"git.sr.ht/~rjarry/aerc/log"
+	"github.com/emersion/go-message/mail"
 	"github.com/gdamore/tcell/v2"
 	"github.com/go-ini/ini"
 	"github.com/imdario/mergo"
@@ -485,23 +486,35 @@ func (uiConfig *UIConfig) GetUserStyle(name string) tcell.Style {
 }
 
 func (uiConfig *UIConfig) GetStyle(so StyleObject) tcell.Style {
-	return uiConfig.style.Get(so)
+	return uiConfig.style.Get(so, nil)
 }
 
 func (uiConfig *UIConfig) GetStyleSelected(so StyleObject) tcell.Style {
-	return uiConfig.style.Selected(so)
+	return uiConfig.style.Selected(so, nil)
 }
 
 func (uiConfig *UIConfig) GetComposedStyle(base StyleObject,
 	styles []StyleObject,
 ) tcell.Style {
-	return uiConfig.style.Compose(base, styles)
+	return uiConfig.style.Compose(base, styles, nil)
 }
 
 func (uiConfig *UIConfig) GetComposedStyleSelected(
 	base StyleObject, styles []StyleObject,
 ) tcell.Style {
-	return uiConfig.style.ComposeSelected(base, styles)
+	return uiConfig.style.ComposeSelected(base, styles, nil)
+}
+
+func (uiConfig *UIConfig) MsgComposedStyle(
+	base StyleObject, styles []StyleObject, h *mail.Header,
+) tcell.Style {
+	return uiConfig.style.Compose(base, styles, h)
+}
+
+func (uiConfig *UIConfig) MsgComposedStyleSelected(
+	base StyleObject, styles []StyleObject, h *mail.Header,
+) tcell.Style {
+	return uiConfig.style.ComposeSelected(base, styles, h)
 }
 
 func (uiConfig *UIConfig) StyleSetPath() string {
diff --git a/doc/aerc-stylesets.7.scd b/doc/aerc-stylesets.7.scd
index 61d6843d..c9f0a78f 100644
--- a/doc/aerc-stylesets.7.scd
+++ b/doc/aerc-stylesets.7.scd
@@ -248,6 +248,26 @@ The order for *dirlist_\** styles is:
 . *dirlist_unread*
 . *dirlist_recent*
 
+# DYNAMIC MESSAGE LIST STYLES
+
+All *msglist_\** styles can be defined for specific email header values. The
+syntax is as follows:
+
+	*msglist_<name>*._<header>_,_<header_value>_.*<attribute>* = _<attr_value>_
+
+If _<header_value>_ starts with a tilde character _~_, it will be interpreted as
+a regular expression.
+
+Examples:
+
+```
+msglist\*.X-Sourcehut-Patchset-Update,APPROVED.fg = green
+msglist\*.X-Sourcehut-Patchset-Update,NEEDS\_REVISION.fg = yellow
+msglist\*.X-Sourcehut-Patchset-Update,REJECTED.fg = red
+"msglist_*.Subject,~^(\[[\w-]+\]\s*)?\[(RFC )?PATCH.fg" = #ffffaf
+"msglist_*.Subject,~^(\[[\w-]+\]\s*)?\[(RFC )?PATCH.selected.fg" = #ffffaf
+```
+
 # COLORS
 
 The color values are set using the values accepted by the tcell library.
diff --git a/widgets/msglist.go b/widgets/msglist.go
index 4bf20b09..0937b786 100644
--- a/widgets/msglist.go
+++ b/widgets/msglist.go
@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	sortthread "github.com/emersion/go-imap-sortthread"
+	"github.com/emersion/go-message/mail"
 	"github.com/gdamore/tcell/v2"
 
 	"git.sr.ht/~rjarry/aerc/config"
@@ -50,6 +51,7 @@ type messageRowParams struct {
 	needsHeaders bool
 	uiConfig     *config.UIConfig
 	styles       []config.StyleObject
+	headers      *mail.Header
 }
 
 func (ml *MessageList) Draw(ctx *ui.Context) {
@@ -110,11 +112,13 @@ func (ml *MessageList) Draw(ctx *ui.Context) {
 		row := &t.Rows[r]
 		params, _ := row.Priv.(messageRowParams)
 		if params.uid == store.SelectedUid() {
-			style = params.uiConfig.GetComposedStyleSelected(
-				config.STYLE_MSGLIST_DEFAULT, params.styles)
+			style = params.uiConfig.MsgComposedStyleSelected(
+				config.STYLE_MSGLIST_DEFAULT, params.styles,
+				params.headers)
 		} else {
-			style = params.uiConfig.GetComposedStyle(
-				config.STYLE_MSGLIST_DEFAULT, params.styles)
+			style = params.uiConfig.MsgComposedStyle(
+				config.STYLE_MSGLIST_DEFAULT, params.styles,
+				params.headers)
 		}
 		return style
 	}
@@ -266,6 +270,7 @@ func addMessage(
 	// TODO deprecate subject contextual UIs? Only related setting is
 	// styleset, should implement a better per-message styling method
 	params.uiConfig = uiConfig.ForSubject(msg.Envelope.Subject)
+	params.headers = msg.RFC822Headers
 
 	return table.AddRow(cells, params)
 }