compose: use a proper header instead of a string map

Prior to this commit, the composer was based on a map[string]string.
While this approach was very versatile, it lead to a constant encoding / decoding
of addresses and other headers.

This commit switches to a different model, where the composer is based on a header.
Commands which want to interact with it can simply set some defaults they would
like to have. Users can overwrite them however they like.

In order to get access to the functions generating / getting the msgid go-message
was upgraded.

7 files changed, 67 insertions, 42 deletions

diff --git a/commands/compose/header.go b/commands/compose/header.go
index 5188a8a2..dd0adee9 100644
--- a/commands/compose/header.go
+++ b/commands/compose/header.go
@@ -57,18 +57,17 @@ func (Header) Execute(aerc *widgets.Aerc, args []string) error {
 	composer, _ := aerc.SelectedTab().(*widgets.Composer)
 
 	if !force {
-		headers, _, err := composer.PrepareHeader()
+		headers, err := composer.PrepareHeader()
 		if err != nil {
 			return err
 		}
 
-		if headers.Has(strings.Title(args[optind])) {
+		if headers.Has(args[optind]) {
 			return fmt.Errorf("Header %s already exists", args[optind])
 		}
 	}
 
-	composer.AddEditor(strings.Title(args[optind]),
-		strings.Join(args[optind+1:], " "), false)
+	composer.AddEditor(args[optind], strings.Join(args[optind+1:], " "), false)
 
 	return nil
 }
diff --git a/commands/compose/postpone.go b/commands/compose/postpone.go
index 60c9df1a..365b683f 100644
--- a/commands/compose/postpone.go
+++ b/commands/compose/postpone.go
@@ -40,7 +40,7 @@ func (Postpone) Execute(aerc *widgets.Aerc, args []string) error {
 
 	aerc.Logger().Println("Postponing mail")
 
-	header, _, err := composer.PrepareHeader()
+	header, err := composer.PrepareHeader()
 	if err != nil {
 		return errors.Wrap(err, "PrepareHeader")
 	}
diff --git a/commands/compose/send.go b/commands/compose/send.go
index abbcb544..70446dab 100644
--- a/commands/compose/send.go
+++ b/commands/compose/send.go
@@ -4,7 +4,6 @@ import (
 	"crypto/tls"
 	"fmt"
 	"io"
-	"net/mail"
 	"net/url"
 	"os/exec"
 	"strings"
@@ -17,9 +16,11 @@ import (
 	"github.com/pkg/errors"
 
 	"git.sr.ht/~sircmpwn/aerc/lib"
+	"git.sr.ht/~sircmpwn/aerc/lib/format"
 	"git.sr.ht/~sircmpwn/aerc/models"
 	"git.sr.ht/~sircmpwn/aerc/widgets"
 	"git.sr.ht/~sircmpwn/aerc/worker/types"
+	"github.com/emersion/go-message/mail"
 	"golang.org/x/oauth2"
 )
 
@@ -71,15 +72,19 @@ func (Send) Execute(aerc *widgets.Aerc, args []string) error {
 		}
 	}
 
-	header, rcpts, err := composer.PrepareHeader()
+	header, err := composer.PrepareHeader()
 	if err != nil {
 		return errors.Wrap(err, "PrepareHeader")
 	}
+	rcpts, err := listRecipients(header)
+	if err != nil {
+		return errors.Wrap(err, "listRecipients")
+	}
 
 	if config.From == "" {
 		return errors.New("No 'From' configured for this account")
 	}
-	from, err := mail.ParseAddress(config.From)
+	from, err := format.ParseAddress(config.From)
 	if err != nil {
 		return errors.Wrap(err, "ParseAddress(config.From)")
 	}
@@ -288,7 +293,12 @@ func (Send) Execute(aerc *widgets.Aerc, args []string) error {
 					composer.Close()
 				}
 			})
-			header, _, _ := composer.PrepareHeader()
+			header, err := composer.PrepareHeader()
+			if err != nil {
+				aerc.PushError(" " + err.Error())
+				w.Close()
+				return
+			}
 			composer.WriteMessage(header, w)
 			w.Close()
 		} else {
@@ -299,3 +309,17 @@ func (Send) Execute(aerc *widgets.Aerc, args []string) error {
 	}()
 	return nil
 }
+
+func listRecipients(h *mail.Header) ([]string, error) {
+	var rcpts []string
+	for _, key := range []string{"to", "cc", "bcc"} {
+		list, err := h.AddressList(key)
+		if err != nil {
+			return nil, err
+		}
+		for _, addr := range list {
+			rcpts = append(rcpts, addr.Address)
+		}
+	}
+	return rcpts, nil
+}
diff --git a/commands/msg/forward.go b/commands/msg/forward.go
index b17482f9..475d6805 100644
--- a/commands/msg/forward.go
+++ b/commands/msg/forward.go
@@ -15,6 +15,7 @@ import (
 	"git.sr.ht/~sircmpwn/aerc/models"
 	"git.sr.ht/~sircmpwn/aerc/widgets"
 	"git.sr.ht/~sircmpwn/aerc/worker/types"
+	"github.com/emersion/go-message/mail"
 
 	"git.sr.ht/~sircmpwn/getopt"
 )
@@ -49,11 +50,6 @@ func (forward) Execute(aerc *widgets.Aerc, args []string) error {
 		}
 	}
 
-	to := ""
-	if len(args) != 1 {
-		to = strings.Join(args[optind:], ", ")
-	}
-
 	widget := aerc.SelectedTab().(widgets.ProvidesMessage)
 	acct := widget.SelectedAccount()
 	if acct == nil {
@@ -69,11 +65,19 @@ func (forward) Execute(aerc *widgets.Aerc, args []string) error {
 	}
 	acct.Logger().Println("Forwarding email " + msg.Envelope.MessageId)
 
+	h := &mail.Header{}
 	subject := "Fwd: " + msg.Envelope.Subject
-	defaults := map[string]string{
-		"To":      to,
-		"Subject": subject,
+	h.SetSubject(subject)
+
+	if len(args) != 1 {
+		to := strings.Join(args[optind:], ", ")
+		tolist, err := mail.ParseAddressList(to)
+		if err != nil {
+			return fmt.Errorf("invalid to address(es): %v", err)
+		}
+		h.SetAddressList("to", tolist)
 	}
+
 	original := models.OriginalMail{
 		From:          format.FormatAddresses(msg.Envelope.From),
 		Date:          msg.Envelope.Date,
@@ -81,15 +85,15 @@ func (forward) Execute(aerc *widgets.Aerc, args []string) error {
 	}
 
 	addTab := func() (*widgets.Composer, error) {
-		composer, err := widgets.NewComposer(aerc, acct, aerc.Config(), acct.AccountConfig(),
-			acct.Worker(), template, defaults, original)
+		composer, err := widgets.NewComposer(aerc, acct, aerc.Config(),
+			acct.AccountConfig(), acct.Worker(), template, h, original)
 		if err != nil {
 			aerc.PushError("Error: " + err.Error())
 			return nil, err
 		}
 
 		tab := aerc.NewTab(composer, subject)
-		if to == "" {
+		if !h.Has("to") {
 			composer.FocusRecipient()
 		} else {
 			composer.FocusTerminal()
diff --git a/commands/msg/recall.go b/commands/msg/recall.go
index 5212041e..b6c7f65d 100644
--- a/commands/msg/recall.go
+++ b/commands/msg/recall.go
@@ -53,15 +53,9 @@ func (Recall) Execute(aerc *widgets.Aerc, args []string) error {
 	}
 	acct.Logger().Println("Recalling message " + msgInfo.Envelope.MessageId)
 
-	// copy the headers to the defaults map for addition to the composition
-	defaults := make(map[string]string)
-	headerFields := msgInfo.RFC822Headers.Fields()
-	for headerFields.Next() {
-		defaults[headerFields.Key()] = headerFields.Value()
-	}
-
 	composer, err := widgets.NewComposer(aerc, acct, aerc.Config(),
-		acct.AccountConfig(), acct.Worker(), "", defaults, models.OriginalMail{})
+		acct.AccountConfig(), acct.Worker(), "", msgInfo.RFC822Headers,
+		models.OriginalMail{})
 	if err != nil {
 		return errors.Wrap(err, "Cannot open a new composer")
 	}
diff --git a/commands/msg/reply.go b/commands/msg/reply.go
index 0298ac20..863c7d25 100644
--- a/commands/msg/reply.go
+++ b/commands/msg/reply.go
@@ -145,22 +145,22 @@ func (reply) Execute(aerc *widgets.Aerc, args []string) error {
 		subject = msg.Envelope.Subject
 	}
 
-	defaults := map[string]string{
-		"To":          format.FormatAddresses(to),
-		"Cc":          format.FormatAddresses(cc),
-		"From":        format.AddressForHumans(from),
-		"Subject":     subject,
-		"In-Reply-To": msg.Envelope.MessageId,
-	}
+	h := &mail.Header{}
+	h.SetAddressList("to", to)
+	h.SetAddressList("cc", cc)
+	h.SetAddressList("from", []*mail.Address{from})
+	h.SetSubject(subject)
+	h.SetMsgIDList("in-reply-to", []string{msg.Envelope.MessageId})
+	//TODO: references header
 	original := models.OriginalMail{
-		From: format.FormatAddresses(msg.Envelope.From),
-		Date: msg.Envelope.Date,
+		From:          format.FormatAddresses(msg.Envelope.From),
+		Date:          msg.Envelope.Date,
 		RFC822Headers: msg.RFC822Headers,
 	}
 
 	addTab := func() error {
 		composer, err := widgets.NewComposer(aerc, acct, aerc.Config(),
-			acct.AccountConfig(), acct.Worker(), template, defaults, original)
+			acct.AccountConfig(), acct.Worker(), template, h, original)
 		if err != nil {
 			aerc.PushError("Error: " + err.Error())
 			return err
diff --git a/commands/msg/unsubscribe.go b/commands/msg/unsubscribe.go
index dec90d5e..205a255d 100644
--- a/commands/msg/unsubscribe.go
+++ b/commands/msg/unsubscribe.go
@@ -9,6 +9,7 @@ import (
 	"git.sr.ht/~sircmpwn/aerc/lib"
 	"git.sr.ht/~sircmpwn/aerc/models"
 	"git.sr.ht/~sircmpwn/aerc/widgets"
+	"github.com/emersion/go-message/mail"
 )
 
 // Unsubscribe helps people unsubscribe from mailing lists by way of the
@@ -84,10 +85,13 @@ func parseUnsubscribeMethods(header string) (methods []*url.URL) {
 func unsubscribeMailto(aerc *widgets.Aerc, u *url.URL) error {
 	widget := aerc.SelectedTab().(widgets.ProvidesMessage)
 	acct := widget.SelectedAccount()
-	defaults := map[string]string{
-		"To":      u.Opaque,
-		"Subject": u.Query().Get("subject"),
+
+	h := &mail.Header{}
+	h.SetSubject(u.Query().Get("subject"))
+	if to, err := mail.ParseAddressList(u.Opaque); err == nil {
+		h.SetAddressList("to", to)
 	}
+
 	composer, err := widgets.NewComposer(
 		aerc,
 		acct,
@@ -95,7 +99,7 @@ func unsubscribeMailto(aerc *widgets.Aerc, u *url.URL) error {
 		acct.AccountConfig(),
 		acct.Worker(),
 		"",
-		defaults,
+		h,
 		models.OriginalMail{},
 	)
 	if err != nil {