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.

1 files changed, 165 insertions, 123 deletions

diff --git a/widgets/compose.go b/widgets/compose.go
index 522146ab..73ebcb3e 100644
--- a/widgets/compose.go
+++ b/widgets/compose.go
@@ -8,7 +8,7 @@ import (
 	"io/ioutil"
 	"mime"
 	"net/http"
-	gomail "net/mail"
+	"net/textproto"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -23,6 +23,7 @@ import (
 
 	"git.sr.ht/~sircmpwn/aerc/completer"
 	"git.sr.ht/~sircmpwn/aerc/config"
+	"git.sr.ht/~sircmpwn/aerc/lib/format"
 	"git.sr.ht/~sircmpwn/aerc/lib/templates"
 	"git.sr.ht/~sircmpwn/aerc/lib/ui"
 	"git.sr.ht/~sircmpwn/aerc/models"
@@ -30,7 +31,9 @@ import (
 )
 
 type Composer struct {
-	editors map[string]*headerEditor
+	editors map[string]*headerEditor // indexes in lower case (from / cc / bcc)
+	header  *mail.Header
+	parent  models.OriginalMail // parent of current message, only set if reply
 
 	acctConfig *config.AccountConfig
 	config     *config.AercConfig
@@ -38,13 +41,10 @@ type Composer struct {
 	aerc       *Aerc
 
 	attachments []string
-	date        time.Time
-	defaults    map[string]string
 	editor      *Terminal
 	email       *os.File
 	grid        *ui.Grid
 	heditors    *ui.Grid // from, to, cc display a user can jump to
-	msgId       string
 	review      *reviewMessage
 	worker      *types.Worker
 	completer   *completer.Completer
@@ -61,22 +61,29 @@ type Composer struct {
 
 func NewComposer(aerc *Aerc, acct *AccountView, conf *config.AercConfig,
 	acctConfig *config.AccountConfig, worker *types.Worker, template string,
-	defaults map[string]string, original models.OriginalMail) (*Composer, error) {
+	h *mail.Header, orig models.OriginalMail) (*Composer, error) {
 
-	if defaults == nil {
-		defaults = make(map[string]string)
+	if h == nil {
+		h = new(mail.Header)
 	}
-	if from := defaults["From"]; from == "" {
-		defaults["From"] = acctConfig.From
+	if fl, err := h.AddressList("from"); err != nil || fl == nil {
+		fl, err = mail.ParseAddressList(acctConfig.From)
+		// realistically this blows up way before us during the config loading
+		if err != nil {
+			return nil, err
+		}
+		if fl != nil {
+			h.SetAddressList("from", fl)
+
+		}
 	}
 
-	templateData := templates.ParseTemplateData(defaults, original)
+	templateData := templates.ParseTemplateData(h, orig)
 	cmpl := completer.New(conf.Compose.AddressBookCmd, func(err error) {
 		aerc.PushError(
 			fmt.Sprintf("could not complete header: %v", err))
 		worker.Logger.Printf("could not complete header: %v", err)
 	}, aerc.Logger())
-	layout, editors, focusable := buildComposeHeader(aerc, cmpl, defaults)
 
 	email, err := ioutil.TempFile("", "aerc-compose-*.eml")
 	if err != nil {
@@ -89,18 +96,15 @@ func NewComposer(aerc *Aerc, acct *AccountView, conf *config.AercConfig,
 		acctConfig: acctConfig,
 		aerc:       aerc,
 		config:     conf,
-		date:       time.Now(),
-		defaults:   defaults,
-		editors:    editors,
+		header:     h,
+		parent:     orig,
 		email:      email,
-		layout:     layout,
-		msgId:      mail.GenerateMessageID(),
 		worker:     worker,
 		// You have to backtab to get to "From", since you usually don't edit it
 		focused:   1,
-		focusable: focusable,
 		completer: cmpl,
 	}
+	c.buildComposeHeader(aerc, cmpl)
 
 	if err := c.AddTemplate(template, templateData); err != nil {
 		return nil, err
@@ -113,56 +117,51 @@ func NewComposer(aerc *Aerc, acct *AccountView, conf *config.AercConfig,
 	return c, nil
 }
 
-func buildComposeHeader(aerc *Aerc, cmpl *completer.Completer,
-	defaults map[string]string) (
-	newLayout HeaderLayout,
-	editors map[string]*headerEditor,
-	focusable []ui.MouseableDrawableInteractive,
-) {
-	layout := aerc.conf.Compose.HeaderLayout
-	editors = make(map[string]*headerEditor)
-	focusable = make([]ui.MouseableDrawableInteractive, 0)
+func (c *Composer) buildComposeHeader(aerc *Aerc, cmpl *completer.Completer) {
+
+	c.layout = aerc.conf.Compose.HeaderLayout
+	c.editors = make(map[string]*headerEditor)
+	c.focusable = make([]ui.MouseableDrawableInteractive, 0)
 
-	for _, row := range layout {
-		for _, h := range row {
-			e := newHeaderEditor(h, "", aerc.SelectedAccount().UiConfig())
+	for i, row := range c.layout {
+		for j, h := range row {
+			h = strings.ToLower(h)
+			c.layout[i][j] = h // normalize to lowercase
+			e := newHeaderEditor(h, c.header, aerc.SelectedAccount().UiConfig())
 			if aerc.conf.Ui.CompletionPopovers {
-				e.input.TabComplete(cmpl.ForHeader(h), aerc.SelectedAccount().UiConfig().CompletionDelay)
+				e.input.TabComplete(cmpl.ForHeader(h),
+					aerc.SelectedAccount().UiConfig().CompletionDelay)
 			}
-			editors[h] = e
+			c.editors[h] = e
 			switch h {
-			case "From":
+			case "from":
 				// Prepend From to support backtab
-				focusable = append([]ui.MouseableDrawableInteractive{e}, focusable...)
+				c.focusable = append([]ui.MouseableDrawableInteractive{e}, c.focusable...)
 			default:
-				focusable = append(focusable, e)
+				c.focusable = append(c.focusable, e)
 			}
 		}
 	}
 
-	// Add Cc/Bcc editors to layout if in defaults and not already visible
-	for _, h := range []string{"Cc", "Bcc"} {
-		if val, ok := defaults[h]; ok && val != "" {
-			if _, ok := editors[h]; !ok {
-				e := newHeaderEditor(h, "", aerc.SelectedAccount().UiConfig())
+	// Add Cc/Bcc editors to layout if present in header and not already visible
+	for _, h := range []string{"cc", "bcc"} {
+		if c.header.Has(h) {
+			if _, ok := c.editors[h]; !ok {
+				e := newHeaderEditor(h, c.header, aerc.SelectedAccount().UiConfig())
 				if aerc.conf.Ui.CompletionPopovers {
 					e.input.TabComplete(cmpl.ForHeader(h), aerc.SelectedAccount().UiConfig().CompletionDelay)
 				}
-				editors[h] = e
-				focusable = append(focusable, e)
-				layout = append(layout, []string{h})
+				c.editors[h] = e
+				c.focusable = append(c.focusable, e)
+				c.layout = append(c.layout, []string{h})
 			}
 		}
 	}
 
-	// Set default values for all editors
-	for key := range editors {
-		if val, ok := defaults[key]; ok {
-			editors[key].input.Set(val)
-			delete(defaults, key)
-		}
+	// load current header values into all editors
+	for _, e := range c.editors {
+		e.loadValue()
 	}
-	return layout, editors, focusable
 }
 
 func (c *Composer) SetSent() {
@@ -205,15 +204,10 @@ func (c *Composer) AddTemplate(template string, data interface{}) error {
 		return fmt.Errorf("Template loading failed: %v", err)
 	}
 
-	// add the headers contained in the template to the default headers
+	// copy the headers contained in the template to the compose headers
 	hf := mr.Header.Fields()
 	for hf.Next() {
-		var val string
-		var err error
-		if val, err = hf.Text(); err != nil {
-			val = hf.Value()
-		}
-		c.defaults[hf.Key()] = val
+		c.header.Set(hf.Key(), hf.Value())
 	}
 
 	part, err := mr.NextPart()
@@ -293,7 +287,7 @@ func (c *Composer) FocusRecipient() *Composer {
 
 // OnHeaderChange registers an OnChange callback for the specified header.
 func (c *Composer) OnHeaderChange(header string, fn func(subject string)) {
-	if editor, ok := c.editors[header]; ok {
+	if editor, ok := c.editors[strings.ToLower(header)]; ok {
 		editor.OnChange(func() {
 			fn(editor.input.String())
 		})
@@ -378,49 +372,24 @@ func (c *Composer) Worker() *types.Worker {
 	return c.worker
 }
 
-func (c *Composer) PrepareHeader() (*mail.Header, []string, error) {
-	header := &mail.Header{}
-	for h, val := range c.defaults {
-		if val == "" {
-			continue
-		}
-		header.SetText(h, val)
-	}
-	header.SetText("Message-Id", c.msgId)
-	header.SetDate(c.date)
-
-	headerKeys := make([]string, 0, len(c.editors))
-	for key := range c.editors {
-		headerKeys = append(headerKeys, key)
+//PrepareHeader finalizes the header, adding the value from the editors
+func (c *Composer) PrepareHeader() (*mail.Header, error) {
+	for _, editor := range c.editors {
+		editor.storeValue()
 	}
 
-	var rcpts []string
-	for h, editor := range c.editors {
-		val := editor.input.String()
-		if val == "" {
-			continue
-		}
-		switch h {
-		case "From", "To", "Cc", "Bcc": // Address headers
-			hdrRcpts, err := gomail.ParseAddressList(val)
-			if err != nil {
-				return nil, nil, errors.Wrapf(err, "ParseAddressList(%s)", val)
-			}
-			edRcpts := make([]*mail.Address, len(hdrRcpts))
-			for i, addr := range hdrRcpts {
-				edRcpts[i] = (*mail.Address)(addr)
-			}
-			header.SetAddressList(h, edRcpts)
-			if h != "From" {
-				for _, addr := range edRcpts {
-					rcpts = append(rcpts, addr.Address)
-				}
-			}
-		default:
-			header.SetText(h, val)
+	// control headers not normally set by the user
+	// repeated calls to PrepareHeader should be a noop
+	if !c.header.Has("Message-Id") {
+		err := c.header.GenerateMessageID()
+		if err != nil {
+			return nil, err
 		}
 	}
-	return header, rcpts, nil
+	if !c.header.Has("Date") {
+		c.header.SetDate(time.Now())
+	}
+	return c.header, nil
 }
 
 func (c *Composer) WriteMessage(header *mail.Header, writer io.Writer) error {
@@ -639,39 +608,51 @@ func (c *Composer) FocusEditor(editor *headerEditor) {
 
 // AddEditor appends a new header editor to the compose window.
 func (c *Composer) AddEditor(header string, value string, appendHeader bool) {
-	if _, ok := c.editors[header]; ok {
-		if appendHeader {
-			header := c.editors[header].input.String()
-			value = strings.TrimSpace(header) + ", " + value
+	var editor *headerEditor
+	header = strings.ToLower(header)
+	if e, ok := c.editors[header]; ok {
+		e.storeValue() // flush modifications from the user to the header
+		editor = e
+	} else {
+		e := newHeaderEditor(header, c.header,
+			c.aerc.SelectedAccount().UiConfig())
+		if c.config.Ui.CompletionPopovers {
+			e.input.TabComplete(c.completer.ForHeader(header),
+				c.config.Ui.CompletionDelay)
 		}
-		c.editors[header].input.Set(value)
-		if value == "" {
-			c.FocusEditor(c.editors[header])
+		c.editors[header] = e
+		c.layout = append(c.layout, []string{header})
+		// Insert focus of new editor before terminal editor
+		c.focusable = append(
+			c.focusable[:len(c.focusable)-1],
+			e,
+			c.focusable[len(c.focusable)-1],
+		)
+		editor = e
+	}
+
+	if appendHeader {
+		currVal := editor.input.String()
+		if currVal != "" {
+			value = strings.TrimSpace(currVal) + ", " + value
 		}
-		return
 	}
-	e := newHeaderEditor(header, value, c.aerc.SelectedAccount().UiConfig())
-	if c.config.Ui.CompletionPopovers {
-		e.input.TabComplete(c.completer.ForHeader(header), c.config.Ui.CompletionDelay)
-	}
-	c.editors[header] = e
-	c.layout = append(c.layout, []string{header})
-	// Insert focus of new editor before terminal editor
-	c.focusable = append(
-		c.focusable[:len(c.focusable)-1],
-		e,
-		c.focusable[len(c.focusable)-1],
-	)
-	c.updateGrid()
+	if value != "" || appendHeader {
+		c.editors[header].input.Set(value)
+		editor.storeValue()
+	}
 	if value == "" {
 		c.FocusEditor(c.editors[header])
 	}
+	c.updateGrid()
 }
 
 // updateGrid should be called when the underlying header layout is changed.
 func (c *Composer) updateGrid() {
 	heditors, height := c.layout.grid(
-		func(h string) ui.Drawable { return c.editors[h] },
+		func(h string) ui.Drawable {
+			return c.editors[h]
+		},
 	)
 
 	if c.grid == nil {
@@ -707,21 +688,82 @@ func (c *Composer) reloadEmail() error {
 
 type headerEditor struct {
 	name     string
+	header   *mail.Header
 	focused  bool
 	input    *ui.TextInput
 	uiConfig config.UIConfig
 }
 
-func newHeaderEditor(name string, value string, uiConfig config.UIConfig) *headerEditor {
-	return &headerEditor{
-		input:    ui.NewTextInput(value, uiConfig),
+func newHeaderEditor(name string, h *mail.Header,
+	uiConfig config.UIConfig) *headerEditor {
+	he := &headerEditor{
+		input:    ui.NewTextInput("", uiConfig),
 		name:     name,
+		header:   h,
 		uiConfig: uiConfig,
 	}
+	he.loadValue()
+	return he
+}
+
+//extractHumanHeaderValue extracts the human readable string for key from the
+//header. If a parsing error occurs the raw value is returned
+func extractHumanHeaderValue(key string, h *mail.Header) string {
+	var val string
+	var err error
+	switch strings.ToLower(key) {
+	case "to", "from", "cc", "bcc":
+		var list []*mail.Address
+		list, err = h.AddressList(key)
+		val = format.FormatAddresses(list)
+	default:
+		val, err = h.Text(key)
+	}
+	if err != nil {
+		// if we can't parse it, show it raw
+		val = h.Get(key)
+	}
+	return val
+}
+
+//loadValue loads the value of he.name form the underlying header
+//the value is decoded and meant for human consumption.
+//decoding issues are ignored and return their raw values
+func (he *headerEditor) loadValue() {
+	he.input.Set(extractHumanHeaderValue(he.name, he.header))
+	he.input.Invalidate()
+}
+
+//storeValue writes the current state back to the underlying header.
+//errors are ignored
+func (he *headerEditor) storeValue() {
+	val := he.input.String()
+	switch strings.ToLower(he.name) {
+	case "to", "from", "cc", "bcc":
+		list, err := mail.ParseAddressList(val)
+		if err == nil {
+			he.header.SetAddressList(he.name, list)
+		} else {
+			// garbage, but it'll blow up upon sending and the user can
+			// fix the issue
+			he.header.SetText(he.name, val)
+		}
+		val = format.FormatAddresses(list)
+	default:
+		he.header.SetText(he.name, val)
+	}
+}
+
+//setValue overwrites the current value of the header editor and flushes it
+//to the underlying header
+func (he *headerEditor) setValue(val string) {
+	he.input.Set(val)
+	he.storeValue()
 }
 
 func (he *headerEditor) Draw(ctx *ui.Context) {
-	name := he.name + " "
+	normalized := textproto.CanonicalMIMEHeaderKey(he.name)
+	name := normalized + " "
 	size := runewidth.StringWidth(name)
 	defaultStyle := he.uiConfig.GetStyle(config.STYLE_DEFAULT)
 	headerStyle := he.uiConfig.GetStyle(config.STYLE_HEADER)