templates: allow inline user styles

Allow custom user-defined styles in a styleset. The styles can take any
name, and must be under the [user] ini section. All attributes apply to
user defined styles.

Example:

	[user]
	red.fg=red
	red.bold=true

Add a .Style function which accepts the name of a user-defined style and
applies it to the string.

	{{.Style "red" "foo"}}

Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>

8 files changed, 66 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4fb5021e..42c41de5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Change local domain name for SMTP with `smtp-domain=example.com` in
   `aerc.conf`
 - New column-based status line format with `status-columns`.
+- Inline user-defined styles can be inserted in UI templates via the
+  `{{.Style "name" string}}` function.
 
 ### Changed
 
diff --git a/config/style.go b/config/style.go
index 65c5a3b1..317c77d0 100644
--- a/config/style.go
+++ b/config/style.go
@@ -254,6 +254,7 @@ func (s Style) composeWith(styles []*Style) Style {
 type StyleSet struct {
 	objects  map[StyleObject]*Style
 	selected map[StyleObject]*Style
+	user     map[string]*Style
 	path     string
 }
 
@@ -261,6 +262,7 @@ func NewStyleSet() StyleSet {
 	ss := StyleSet{
 		objects:  make(map[StyleObject]*Style),
 		selected: make(map[StyleObject]*Style),
+		user:     make(map[string]*Style),
 	}
 	for _, so := range StyleNames {
 		ss.objects[so] = new(Style)
@@ -285,6 +287,10 @@ func (ss StyleSet) Selected(so StyleObject) tcell.Style {
 	return ss.selected[so].Get()
 }
 
+func (ss StyleSet) UserStyle(name string) tcell.Style {
+	return ss.user[name].Get()
+}
+
 func (ss StyleSet) Compose(so StyleObject, sos []StyleObject) tcell.Style {
 	base := *ss.objects[so]
 	styles := make([]*Style, len(sos))
@@ -437,6 +443,32 @@ func (ss *StyleSet) ParseStyleSet(file *ini.File) error {
 		}
 	}
 
+	user, err := file.GetSection("user")
+	if err != nil {
+		// This errors if the section doesn't exist, which is ok
+		return nil
+	}
+	for _, key := range user.KeyStrings() {
+		tokens := strings.Split(key, ".")
+		var styleName, attr string
+		switch len(tokens) {
+		case 2:
+			styleName, attr = tokens[0], tokens[1]
+		default:
+			return errors.New("Style parsing error: " + key)
+		}
+		val := user.KeysHash()[key]
+		s, ok := ss.user[styleName]
+		if !ok {
+			// Haven't seen this name before, add it to the map
+			s = &Style{}
+			ss.user[styleName] = s
+		}
+		if err := s.Set(attr, val); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }
 
diff --git a/config/templates.go b/config/templates.go
index bc05be66..f618d365 100644
--- a/config/templates.go
+++ b/config/templates.go
@@ -111,3 +111,4 @@ func (d *dummyData) ContentInfo() string             { return "" }
 func (d *dummyData) StatusInfo() string              { return "" }
 func (d *dummyData) TrayInfo() string                { return "" }
 func (d *dummyData) PendingKeys() string             { return "" }
+func (d *dummyData) Style(string, string) string     { return "" }
diff --git a/config/ui.go b/config/ui.go
index b1330ffd..64469643 100644
--- a/config/ui.go
+++ b/config/ui.go
@@ -629,6 +629,10 @@ func (base *UIConfig) mergeContextual(
 	return base
 }
 
+func (uiConfig *UIConfig) GetUserStyle(name string) tcell.Style {
+	return uiConfig.style.UserStyle(name)
+}
+
 func (uiConfig *UIConfig) GetStyle(so StyleObject) tcell.Style {
 	return uiConfig.style.Get(so)
 }
diff --git a/doc/aerc-stylesets.7.scd b/doc/aerc-stylesets.7.scd
index eaedb4cb..c633dcef 100644
--- a/doc/aerc-stylesets.7.scd
+++ b/doc/aerc-stylesets.7.scd
@@ -166,6 +166,18 @@ declared under a *[viewer]* section of the styleset file.
 |  *quote_x*
 :  Above fourth level quoted text.
 
+User defined styles can be used to style arbitrary strings in go-templates (see
+_.Style_ in *aerc-templates*(7)). User styles must be defined in the _[user]_
+ini section. Styles can be referenced by their name (e.g. _red.fg_ is named
+"red").
+
+Example:
+
+```
+[user]
+red.fg=red
+```
+
 ## FNMATCH STYLE WILDCARD MATCHING
 
 The styleset configuration can be made simpler by using the fnmatch
diff --git a/doc/aerc-templates.7.scd b/doc/aerc-templates.7.scd
index 83b19ac9..f3f2a568 100644
--- a/doc/aerc-templates.7.scd
+++ b/doc/aerc-templates.7.scd
@@ -363,6 +363,13 @@ aerc provides the following additional functions:
 	{{compactPath .Folder}}
 	```
 
+*.Style*
+	Apply a user-defined style (see *aerc-stylesets*(7)) to a string.
+
+	```
+	{{.Style "red" .Account}}
+	```
+
 *version*
 	Returns the version of aerc, which can be useful for things like X-Mailer.
 
diff --git a/lib/state/templates.go b/lib/state/templates.go
index 2d5e39f5..d5631b11 100644
--- a/lib/state/templates.go
+++ b/lib/state/templates.go
@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"git.sr.ht/~rjarry/aerc/config"
+	"git.sr.ht/~rjarry/aerc/lib/parse"
 	"git.sr.ht/~rjarry/aerc/models"
 	sortthread "github.com/emersion/go-imap-sortthread"
 	"github.com/emersion/go-message/mail"
@@ -449,3 +450,9 @@ func (d *TemplateData) TrayInfo() string {
 func (d *TemplateData) PendingKeys() string {
 	return config.FormatKeyStrokes(d.pendingKeys)
 }
+
+func (d *TemplateData) Style(name string, content string) string {
+	cfg := config.Ui.ForAccount(d.Account())
+	style := cfg.GetUserStyle(name)
+	return parse.ApplyStyle(style, content)
+}
diff --git a/models/templates.go b/models/templates.go
index 4886b83c..916b3974 100644
--- a/models/templates.go
+++ b/models/templates.go
@@ -40,4 +40,5 @@ type TemplateData interface {
 	StatusInfo() string
 	TrayInfo() string
 	PendingKeys() string
+	Style(string, string) string
 }