Add new-email trigger

This patch sets up the trigger config section of aerc.conf.

Each trigger has its own function which is called from the place where
it is triggered. Currently only the new-email trigger is implemented.

The triggers make use of format strings. For instance, in the new-email
trigger this allows the user to select the trigger command and also the
information extracted from the command and placed into their command.

To actually execute the trigger commands the keypresses are simulated.

Further triggers can be implemented in the future.

Formatting of the command is moved to a new package.

11 files changed, 175 insertions, 35 deletions

diff --git a/aerc.go b/aerc.go
index ca131e6..2420b44 100644
--- a/aerc.go
+++ b/aerc.go
@@ -52,7 +52,7 @@ func getCommands(selected libui.Drawable) []*commands.Commands {
 	}
 }
 
-func execCommand(aerc *widgets.Aerc, ui *libui.UI, cmd string) error {
+func execCommand(aerc *widgets.Aerc, ui *libui.UI, cmd []string) error {
 	cmds := getCommands((*aerc).SelectedTab())
 	for i, set := range cmds {
 		err := set.ExecuteCommand(aerc, cmd)
@@ -144,11 +144,11 @@ func main() {
 		ui   *libui.UI
 	)
 
-	aerc = widgets.NewAerc(conf, logger, func(cmd string) error {
-			return execCommand(aerc, ui, cmd)
-		}, func(cmd string) []string {
-			return getCompletions(aerc, cmd)
-		})
+	aerc = widgets.NewAerc(conf, logger, func(cmd []string) error {
+		return execCommand(aerc, ui, cmd)
+	}, func(cmd string) []string {
+		return getCompletions(aerc, cmd)
+	})
 
 	ui, err = libui.Initialize(conf, aerc)
 	if err != nil {
diff --git a/commands/commands.go b/commands/commands.go
index 4038fe2..c6f149f 100644
--- a/commands/commands.go
+++ b/commands/commands.go
@@ -56,11 +56,7 @@ type CommandSource interface {
 	Commands() *Commands
 }
 
-func (cmds *Commands) ExecuteCommand(aerc *widgets.Aerc, cmd string) error {
-	args, err := shlex.Split(cmd)
-	if err != nil {
-		return err
-	}
+func (cmds *Commands) ExecuteCommand(aerc *widgets.Aerc, args []string) error {
 	if len(args) == 0 {
 		return errors.New("Expected a command.")
 	}
diff --git a/config/aerc.conf.in b/config/aerc.conf.in
index 4219042..5b080e9 100644
--- a/config/aerc.conf.in
+++ b/config/aerc.conf.in
@@ -96,3 +96,14 @@ subject,~^\[PATCH=awk -f @SHAREDIR@/filters/hldiff
 #text/html=@SHAREDIR@/filters/html
 text/*=awk -f @SHAREDIR@/filters/plaintext
 #image/*=catimg -w $(tput cols) -
+
+[triggers]
+#
+# Triggers specify commands to execute when certain events occur.
+#
+# Example:
+# new-email=exec notify-send "New email from %n" "%s"<Enter>
+
+#
+# Executed when a new email arrives in the selected folder
+new-email=
diff --git a/config/config.go b/config/config.go
index 4a049fa..f863729 100644
--- a/config/config.go
+++ b/config/config.go
@@ -84,6 +84,11 @@ type ViewerConfig struct {
 	HeaderLayout   [][]string `ini:"-"`
 }
 
+type TriggersConfig struct {
+	NewEmail       string `ini:"new-email"`
+	ExecuteCommand func(command []string) error
+}
+
 type AercConfig struct {
 	Bindings BindingConfig
 	Compose  ComposeConfig
@@ -91,6 +96,7 @@ type AercConfig struct {
 	Accounts []AccountConfig `ini:"-"`
 	Filters  []FilterConfig  `ini:"-"`
 	Viewer   ViewerConfig    `ini:"-"`
+	Triggers TriggersConfig  `ini:"-"`
 	Ui       UIConfig
 	General  GeneralConfig
 }
@@ -278,6 +284,11 @@ func (config *AercConfig) LoadConfig(file *ini.File) error {
 			return err
 		}
 	}
+	if triggers, err := file.GetSection("triggers"); err == nil {
+		if err := triggers.MapTo(&config.Triggers); err != nil {
+			return err
+		}
+	}
 	return nil
 }
 
diff --git a/config/triggers.go b/config/triggers.go
new file mode 100644
index 0000000..d31f267
--- /dev/null
+++ b/config/triggers.go
@@ -0,0 +1,49 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/google/shlex"
+
+	"git.sr.ht/~sircmpwn/aerc/lib/format"
+	"git.sr.ht/~sircmpwn/aerc/models"
+)
+
+func (trig *TriggersConfig) ExecTrigger(triggerCmd string,
+	triggerFmt func(string) (string, error)) error {
+
+	if len(triggerCmd) == 0 {
+		return errors.New("Trigger command empty")
+	}
+	triggerCmdParts, err := shlex.Split(triggerCmd)
+	if err != nil {
+		return err
+	}
+
+	var command []string
+	for _, part := range triggerCmdParts {
+		formattedPart, err := triggerFmt(part)
+		if err != nil {
+			return err
+		}
+		command = append(command, formattedPart)
+	}
+	return trig.ExecuteCommand(command)
+}
+
+func (trig *TriggersConfig) ExecNewEmail(account *AccountConfig,
+	conf *AercConfig, msg *models.MessageInfo) {
+	err := trig.ExecTrigger(trig.NewEmail,
+		func(part string) (string, error) {
+			formatstr, args, err := format.ParseMessageFormat(part,
+				conf.Ui.TimestampFormat, account.Name, 0, msg)
+			if err != nil {
+				return "", err
+			}
+			return fmt.Sprintf(formatstr, args...), nil
+		})
+	if err != nil {
+		fmt.Printf("Error from the new-email trigger: %s\n", err)
+	}
+}
diff --git a/doc/aerc-config.5.scd b/doc/aerc-config.5.scd
index 665f4f4..08f65af 100644
--- a/doc/aerc-config.5.scd
+++ b/doc/aerc-config.5.scd
@@ -68,6 +68,10 @@ These options are configured in the *[ui]* section of aerc.conf.
 :  comma-separated list of formatted CC names and addresses
 |  %s
 :  subject
+|  %t
+:  the (first) address the new email was sent to
+|  %T
+:  the account name which received the email
 |  %u
 :  sender mailbox name (e.g. "smith" in "smith@example.net")
 |  %v
@@ -164,6 +168,22 @@ aerc ships with some default filters installed in the share directory (usually
 _/usr/share/aerc/filters_). Note that these may have additional dependencies
 that aerc does not have alone.
 
+## TRIGGERS
+
+Triggers specify commands to execute when certain events occur.
+
+They are configured in the *[triggers]* section of aerc.conf.
+
+*new-email*
+	Executed when a new email arrives in the selected folder.
+
+	e.g. new-email=exec notify-send "New email from %n" "%s"
+
+	Default: ""
+
+	Format specifiers from *index-format* are expanded with respect to the new
+	message.
+
 # ACCOUNTS.CONF
 
 This file is used for configuring each mail account used for aerc. Each section
diff --git a/lib/indexformat.go b/lib/format/format.go
index 34b4d77..b403f2d 100644
--- a/lib/indexformat.go
+++ b/lib/format/format.go
@@ -1,4 +1,4 @@
-package lib
+package format
 
 import (
 	"errors"
@@ -6,14 +6,12 @@ import (
 	"strings"
 	"unicode"
 
-	"git.sr.ht/~sircmpwn/aerc/config"
 	"git.sr.ht/~sircmpwn/aerc/models"
 )
 
-func ParseIndexFormat(conf *config.AercConfig, number int,
-	msg *models.MessageInfo) (string, []interface{}, error) {
-
-	format := conf.Ui.IndexFormat
+func ParseMessageFormat(format string, timestampformat string,
+	accountName string, number int, msg *models.MessageInfo) (string,
+	[]interface{}, error) {
 	retval := make([]byte, 0, len(format))
 	var args []interface{}
 
@@ -64,11 +62,13 @@ func ParseIndexFormat(conf *config.AercConfig, number int,
 			retval = append(retval, '%')
 		case 'a':
 			if len(msg.Envelope.From) == 0 {
-				return "", nil, errors.New("found no address for sender")
+				return "", nil,
+					errors.New("found no address for sender")
 			}
 			addr := msg.Envelope.From[0]
 			retval = append(retval, 's')
-			args = append(args, fmt.Sprintf("%s@%s", addr.Mailbox, addr.Host))
+			args = append(args,
+				fmt.Sprintf("%s@%s", addr.Mailbox, addr.Host))
 		case 'A':
 			var addr *models.Address
 			if len(msg.Envelope.ReplyTo) == 0 {
@@ -82,26 +82,31 @@ func ParseIndexFormat(conf *config.AercConfig, number int,
 				addr = msg.Envelope.ReplyTo[0]
 			}
 			retval = append(retval, 's')
-			args = append(args, fmt.Sprintf("%s@%s", addr.Mailbox, addr.Host))
+			args = append(args,
+				fmt.Sprintf("%s@%s", addr.Mailbox, addr.Host))
 		case 'C':
 			retval = append(retval, 'd')
 			args = append(args, number)
 		case 'd':
 			retval = append(retval, 's')
-			args = append(args, msg.InternalDate.Format(conf.Ui.TimestampFormat))
+			args = append(args,
+				msg.InternalDate.Format(timestampformat))
 		case 'D':
 			retval = append(retval, 's')
-			args = append(args, msg.InternalDate.Local().Format(conf.Ui.TimestampFormat))
+			args = append(args,
+				msg.InternalDate.Local().Format(timestampformat))
 		case 'f':
 			if len(msg.Envelope.From) == 0 {
-				return "", nil, errors.New("found no address for sender")
+				return "", nil,
+					errors.New("found no address for sender")
 			}
 			addr := msg.Envelope.From[0].Format()
 			retval = append(retval, 's')
 			args = append(args, addr)
 		case 'F':
 			if len(msg.Envelope.From) == 0 {
-				return "", nil, errors.New("found no address for sender")
+				return "", nil,
+					errors.New("found no address for sender")
 			}
 			addr := msg.Envelope.From[0]
 			// TODO: handle case when sender is current user. Then
@@ -120,7 +125,8 @@ func ParseIndexFormat(conf *config.AercConfig, number int,
 			args = append(args, msg.Envelope.MessageId)
 		case 'n':
 			if len(msg.Envelope.From) == 0 {
-				return "", nil, errors.New("found no address for sender")
+				return "", nil,
+					errors.New("found no address for sender")
 			}
 			addr := msg.Envelope.From[0]
 			var val string
@@ -142,22 +148,37 @@ func ParseIndexFormat(conf *config.AercConfig, number int,
 		case 's':
 			retval = append(retval, 's')
 			args = append(args, msg.Envelope.Subject)
+		case 't':
+			if len(msg.Envelope.To) == 0 {
+				return "", nil,
+					errors.New("found no address for recipient")
+			}
+			addr := msg.Envelope.To[0]
+			retval = append(retval, 's')
+			args = append(args,
+				fmt.Sprintf("%s@%s", addr.Mailbox, addr.Host))
+		case 'T':
+			retval = append(retval, 's')
+			args = append(args, accountName)
 		case 'u':
 			if len(msg.Envelope.From) == 0 {
-				return "", nil, errors.New("found no address for sender")
+				return "", nil,
+					errors.New("found no address for sender")
 			}
 			addr := msg.Envelope.From[0]
 			retval = append(retval, 's')
 			args = append(args, addr.Mailbox)
 		case 'v':
 			if len(msg.Envelope.From) == 0 {
-				return "", nil, errors.New("found no address for sender")
+				return "", nil,
+					errors.New("found no address for sender")
 			}
 			addr := msg.Envelope.From[0]
 			// check if message is from current user
 			if addr.Name != "" {
 				retval = append(retval, 's')
-				args = append(args, strings.Split(addr.Name, " ")[0])
+				args = append(args,
+					strings.Split(addr.Name, " ")[0])
 			}
 		case 'Z':
 			// calculate all flags
@@ -237,5 +258,6 @@ func ParseIndexFormat(conf *config.AercConfig, number int,
 	return string(retval), args, nil
 
 handle_end_error:
-	return "", nil, errors.New("reached end of string while parsing index format")
+	return "", nil,
+		errors.New("reached end of string while parsing message format")
 }
diff --git a/lib/msgstore.go b/lib/msgstore.go
index 736217e..53faaac 100644
--- a/lib/msgstore.go
+++ b/lib/msgstore.go
@@ -32,10 +32,13 @@ type MessageStore struct {
 	pendingBodies  map[uint32]interface{}
 	pendingHeaders map[uint32]interface{}
 	worker         *types.Worker
+
+	triggerNewEmail func(*models.MessageInfo)
 }
 
 func NewMessageStore(worker *types.Worker,
-	dirInfo *models.DirectoryInfo) *MessageStore {
+	dirInfo *models.DirectoryInfo,
+	triggerNewEmail func(*models.MessageInfo)) *MessageStore {
 
 	return &MessageStore{
 		Deleted: make(map[uint32]interface{}),
@@ -48,6 +51,8 @@ func NewMessageStore(worker *types.Worker,
 		pendingBodies:  make(map[uint32]interface{}),
 		pendingHeaders: make(map[uint32]interface{}),
 		worker:         worker,
+
+		triggerNewEmail: triggerNewEmail,
 	}
 }
 
@@ -165,6 +170,18 @@ func (store *MessageStore) Update(msg types.WorkerMessage) {
 		} else {
 			store.Messages[msg.Info.Uid] = msg.Info
 		}
+		seen := false
+		recent := false
+		for _, flag := range msg.Info.Flags {
+			if flag == models.RecentFlag {
+				recent = true
+			} else if flag == models.SeenFlag {
+				seen = true
+			}
+		}
+		if !seen && recent {
+			store.triggerNewEmail(msg.Info)
+		}
 		if _, ok := store.pendingHeaders[msg.Info.Uid]; msg.Info.Envelope != nil && ok {
 			delete(store.pendingHeaders, msg.Info.Uid)
 			if cbs, ok := store.headerCallbacks[msg.Info.Uid]; ok {
diff --git a/widgets/account.go b/widgets/account.go
index f070df1..92e7a56 100644
--- a/widgets/account.go
+++ b/widgets/account.go
@@ -203,7 +203,11 @@ func (acct *AccountView) onMessage(msg types.WorkerMessage) {
 		if store, ok := acct.msgStores[msg.Info.Name]; ok {
 			store.Update(msg)
 		} else {
-			store = lib.NewMessageStore(acct.worker, msg.Info)
+			store = lib.NewMessageStore(acct.worker, msg.Info,
+				func(msg *models.MessageInfo) {
+					acct.conf.Triggers.ExecNewEmail(acct.acct,
+						acct.conf, msg)
+				})
 			acct.msgStores[msg.Info.Name] = store
 			store.OnUpdate(func(_ *lib.MessageStore) {
 				store.OnUpdate(nil)
diff --git a/widgets/aerc.go b/widgets/aerc.go
index 079d442..3cf1f64 100644
--- a/widgets/aerc.go
+++ b/widgets/aerc.go
@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/gdamore/tcell"
+	"github.com/google/shlex"
 
 	"git.sr.ht/~sircmpwn/aerc/config"
 	"git.sr.ht/~sircmpwn/aerc/lib/ui"
@@ -16,7 +17,7 @@ import (
 
 type Aerc struct {
 	accounts    map[string]*AccountView
-	cmd         func(cmd string) error
+	cmd         func(cmd []string) error
 	complete    func(cmd string) []string
 	conf        *config.AercConfig
 	focused     libui.Interactive
@@ -30,7 +31,7 @@ type Aerc struct {
 }
 
 func NewAerc(conf *config.AercConfig, logger *log.Logger,
-	cmd func(cmd string) error, complete func(cmd string) []string) *Aerc {
+	cmd func(cmd []string) error, complete func(cmd string) []string) *Aerc {
 
 	tabs := libui.NewTabs()
 
@@ -62,6 +63,7 @@ func NewAerc(conf *config.AercConfig, logger *log.Logger,
 	}
 
 	statusline.SetAerc(aerc)
+	conf.Triggers.ExecuteCommand = cmd
 
 	for i, acct := range conf.Accounts {
 		view := NewAccountView(conf, &conf.Accounts[i], logger, aerc)
@@ -311,7 +313,12 @@ func (aerc *Aerc) focus(item libui.Interactive) {
 func (aerc *Aerc) BeginExCommand() {
 	previous := aerc.focused
 	exline := NewExLine(func(cmd string) {
-		err := aerc.cmd(cmd)
+		parts, err := shlex.Split(cmd)
+		if err != nil {
+			aerc.PushStatus(" "+err.Error(), 10*time.Second).
+				Color(tcell.ColorDefault, tcell.ColorRed)
+		}
+		err = aerc.cmd(parts)
 		if err != nil {
 			aerc.PushStatus(" "+err.Error(), 10*time.Second).
 				Color(tcell.ColorDefault, tcell.ColorRed)
diff --git a/widgets/msglist.go b/widgets/msglist.go
index e8ba8c1..abf6921 100644
--- a/widgets/msglist.go
+++ b/widgets/msglist.go
@@ -9,6 +9,7 @@ import (
 
 	"git.sr.ht/~sircmpwn/aerc/config"
 	"git.sr.ht/~sircmpwn/aerc/lib"
+	"git.sr.ht/~sircmpwn/aerc/lib/format"
 	"git.sr.ht/~sircmpwn/aerc/lib/ui"
 	"git.sr.ht/~sircmpwn/aerc/models"
 )
@@ -95,7 +96,9 @@ func (ml *MessageList) Draw(ctx *ui.Context) {
 		}
 
 		ctx.Fill(0, row, ctx.Width(), 1, ' ', style)
-		fmtStr, args, err := lib.ParseIndexFormat(ml.conf, i, msg)
+		fmtStr, args, err := format.ParseMessageFormat(
+			ml.conf.Ui.IndexFormat,
+			ml.conf.Ui.TimestampFormat, "", i, msg)
 		if err != nil {
 			ctx.Printf(0, row, style, "%v", err)
 		} else {