package widgets

import (
	"bytes"
	"fmt"
	"io"
	"net/textproto"
	"os"
	"os/exec"
	"strings"
	"time"

	"github.com/emersion/go-message/mail"
	"github.com/gdamore/tcell/v2"
	"github.com/mattn/go-runewidth"
	"github.com/mitchellh/go-homedir"
	"github.com/pkg/errors"

	"git.sr.ht/~rjarry/aerc/completer"
	"git.sr.ht/~rjarry/aerc/config"
	"git.sr.ht/~rjarry/aerc/lib"
	"git.sr.ht/~rjarry/aerc/lib/format"
	"git.sr.ht/~rjarry/aerc/lib/templates"
	"git.sr.ht/~rjarry/aerc/lib/ui"
	"git.sr.ht/~rjarry/aerc/logging"
	"git.sr.ht/~rjarry/aerc/models"
	"git.sr.ht/~rjarry/aerc/worker/types"
)

type Composer struct {
	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
	acct       *AccountView
	aerc       *Aerc

	attachments []lib.Attachment
	editor      *Terminal
	email       *os.File
	grid        *ui.Grid
	heditors    *ui.Grid // from, to, cc display a user can jump to
	review      *reviewMessage
	worker      *types.Worker
	completer   *completer.Completer
	crypto      *cryptoStatus
	sign        bool
	encrypt     bool
	attachKey   bool

	layout    HeaderLayout
	focusable []ui.MouseableDrawableInteractive
	focused   int
	sent      bool

	onClose []func(ti *Composer)

	width int

	textParts []*lib.Part
}

func NewComposer(aerc *Aerc, acct *AccountView, conf *config.AercConfig,
	acctConfig *config.AccountConfig, worker *types.Worker, template string,
	h *mail.Header, orig models.OriginalMail,
) (*Composer, error) {
	if h == nil {
		h = new(mail.Header)
	}
	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(h, orig)
	cmd := acctConfig.AddressBookCmd
	if cmd == "" {
		cmd = conf.Compose.AddressBookCmd
	}
	cmpl := completer.New(cmd, func(err error) {
		aerc.PushError(
			fmt.Sprintf("could not complete header: %v", err))
		logging.Errorf("could not complete header: %v", err)
	})

	email, err := os.CreateTemp("", "aerc-compose-*.eml")
	if err != nil {
		// TODO: handle this better
		return nil, err
	}

	c := &Composer{
		acct:       acct,
		acctConfig: acctConfig,
		aerc:       aerc,
		config:     conf,
		header:     h,
		parent:     orig,
		email:      email,
		worker:     worker,
		// You have to backtab to get to "From", since you usually don't edit it
		focused:   1,
		completer: cmpl,
	}
	if err := c.AddTemplate(template, templateData); err != nil {
		return nil, err
	}
	c.buildComposeHeader(aerc, cmpl)

	c.AddSignature()

	c.updateGrid()
	err = c.updateCrypto()
	if err != nil {
		logging.Warnf("failed to update crypto: %v", err)
	}
	c.ShowTerminal()

	if c.acctConfig.PgpAutoSign {
		err = c.SetSign(true)
		logging.Warnf("failed to enable message signing: %v", err)
	}
	if c.acctConfig.PgpOpportunisticEncrypt {
		c.SetEncrypt(true)
	}

	return c, nil
}

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)
	uiConfig := c.acct.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, uiConfig)
			if aerc.conf.Ui.CompletionPopovers {
				e.input.TabComplete(cmpl.ForHeader(h), uiConfig.CompletionDelay)
			}
			c.editors[h] = e
			switch h {
			case "from":
				// Prepend From to support backtab
				c.focusable = append([]ui.MouseableDrawableInteractive{e}, c.focusable...)
			default:
				c.focusable = append(c.focusable, e)
			}
		}
	}

	// 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, uiConfig)
				if aerc.conf.Ui.CompletionPopovers {
					e.input.TabComplete(cmpl.ForHeader(h), uiConfig.CompletionDelay)
				}
				c.editors[h] = e
				c.focusable = append(c.focusable, e)
				c.layout = append(c.layout, []string{h})
			}
		}
	}

	// load current header values into all editors
	for _, e := range c.editors {
		e.loadValue()
	}
}

func (c *Composer) SetSent() {
	c.sent = true
}

func (c *Composer) Sent() bool {
	return c.sent
}

func (c *Composer) SetAttachKey(attach bool) error {
	if !attach {
		name := c.crypto.signKey + ".asc"
		found := false
		for _, a := range c.attachments {
			if a.Name() == name {
				found = true
			}
		}
		if found {
			err := c.DeleteAttachment(name)
			if err != nil {
				return fmt.Errorf("failed to delete attachment '%s: %w", name, err)
			}
		} else {
			attach = !attach
		}
	}
	if attach {
		var s string
		var err error
		if c.crypto.signKey == "" {
			if c.acctConfig.PgpKeyId != "" {
				s = c.acctConfig.PgpKeyId
			} else {
				s, err = getSenderEmail(c)
				if err != nil {
					return err
				}
			}
			c.crypto.signKey, err = c.aerc.Crypto.GetSignerKeyId(s)
			if err != nil {
				return err
			}
		}

		r, err := c.aerc.Crypto.ExportKey(c.crypto.signKey)
		if err != nil {
			return err
		}

		c.attachments = append(c.attachments,
			lib.NewPartAttachment(
				lib.NewPart(
					"application/pgp-keys",
					map[string]string{"charset": "UTF-8"},
					r,
				),
				c.crypto.signKey+".asc",
			),
		)

	}

	c.attachKey = attach

	c.resetReview()
	return nil
}

func (c *Composer) AttachKey() bool {
	return c.attachKey
}

func (c *Composer) SetSign(sign bool) error {
	c.sign = sign
	err := c.updateCrypto()
	if err != nil {
		c.sign = !sign
		return fmt.Errorf("Cannot sign message: %w", err)
	}
	return nil
}

func (c *Composer) Sign() bool {
	return c.sign
}

func (c *Composer) SetEncrypt(encrypt bool) *Composer {
	if !encrypt {
		c.encrypt = encrypt
		err := c.updateCrypto()
		if err != nil {
			logging.Warnf("failed to update crypto: %v", err)
		}
		return c
	}
	// Check on any attempt to encrypt, and any lost focus of "to", "cc", or
	// "bcc" field. Use OnFocusLost instead of OnChange to limit keyring checks
	c.encrypt = c.checkEncryptionKeys("")
	if c.crypto.setEncOneShot {
		// Prevent registering a lot of callbacks
		c.OnFocusLost("to", c.checkEncryptionKeys)
		c.OnFocusLost("cc", c.checkEncryptionKeys)
		c.OnFocusLost("bcc", c.checkEncryptionKeys)
		c.crypto.setEncOneShot = false
	}
	return c
}

func (c *Composer) Encrypt() bool {
	return c.encrypt
}

func (c *Composer) updateCrypto() error {
	if c.crypto == nil {
		uiConfig := c.acct.UiConfig()
		c.crypto = newCryptoStatus(uiConfig)
	}
	var err error
	// Check if signKey is empty so we only run this once
	if c.sign && c.crypto.signKey == "" {
		cp := c.aerc.Crypto
		var s string
		if c.acctConfig.PgpKeyId != "" {
			s = c.acctConfig.PgpKeyId
		} else {
			s, err = getSenderEmail(c)
			if err != nil {
				return err
			}
		}
		c.crypto.signKey, err = cp.GetSignerKeyId(s)
		if err != nil {
			return err
		}
	}
	crHeight := 0
	st := ""
	switch {
	case c.sign && c.encrypt:
		st = fmt.Sprintf("Sign (%s) & Encrypt", c.crypto.signKey)
		crHeight = 1
	case c.sign:
		st = fmt.Sprintf("Sign (%s)", c.crypto.signKey)
		crHeight = 1
	case c.encrypt:
		st = "Encrypt"
		crHeight = 1
	default:
		st = ""
	}
	c.crypto.status.Text(st)
	hHeight := len(c.layout)
	c.grid.Rows([]ui.GridSpec{
		{Strategy: ui.SIZE_EXACT, Size: ui.Const(hHeight)},
		{Strategy: ui.SIZE_EXACT, Size: ui.Const(crHeight)},
		{Strategy: ui.SIZE_EXACT, Size: ui.Const(1)},
		{Strategy: ui.SIZE_WEIGHT, Size: ui.Const(1)},
	})
	c.grid.AddChild(c.crypto).At(1, 0)
	return nil
}

// Note: this does not reload the editor. You must call this before the first
// Draw() call.
func (c *Composer) SetContents(reader io.Reader) *Composer {
	_, err := c.email.Seek(0, io.SeekStart)
	if err != nil {
		logging.Warnf("failed to seek beginning of mail: %v", err)
	}
	_, err = io.Copy(c.email, reader)
	if err != nil {
		logging.Warnf("failed to copy mail: %v", err)
	}
	err = c.email.Sync()
	if err != nil {
		logging.Warnf("failed to sync mail: %v", err)
	}
	_, err = c.email.Seek(0, io.SeekStart)
	if err != nil {
		logging.Warnf("failed to seek beginning of mail after sync: %v", err)
	}
	return c
}

func (c *Composer) AppendContents(reader io.Reader) {
	_, err := c.email.Seek(0, io.SeekEnd)
	if err != nil {
		logging.Warnf("failed to seek beginning of mail: %v", err)
	}
	_, err = io.Copy(c.email, reader)
	if err != nil {
		logging.Warnf("failed to copy mail: %v", err)
	}
	err = c.email.Sync()
	if err != nil {
		logging.Warnf("failed to sync mail: %v", err)
	}
}

func (c *Composer) AppendPart(mimetype string, params map[string]string, body io.Reader) error {
	if !strings.HasPrefix(mimetype, "text") {
		return fmt.Errorf("can only append text mimetypes")
	}
	c.textParts = append(c.textParts, lib.NewPart(mimetype, params, body))
	c.resetReview()
	return nil
}

func (c *Composer) AddTemplate(template string, data interface{}) error {
	if template == "" {
		return nil
	}

	templateText, err := templates.ParseTemplateFromFile(
		template, c.config.Templates.TemplateDirs, data)
	if err != nil {
		return err
	}

	mr, err := mail.CreateReader(templateText)
	if err != nil {
		return fmt.Errorf("Template loading failed: %w", err)
	}

	// copy the headers contained in the template to the compose headers
	hf := mr.Header.Fields()
	for hf.Next() {
		c.header.Set(hf.Key(), hf.Value())
	}

	part, err := mr.NextPart()
	if err != nil {
		return fmt.Errorf("Could not get body of template: %w", err)
	}

	c.AppendContents(part.Body)
	return nil
}

func (c *Composer) AddSignature() {
	var signature []byte
	if c.acctConfig.SignatureCmd != "" {
		var err error
		signature, err = c.readSignatureFromCmd()
		if err != nil {
			signature = c.readSignatureFromFile()
		}
	} else {
		signature = c.readSignatureFromFile()
	}
	c.AppendContents(bytes.NewReader(signature))
}

func (c *Composer) readSignatureFromCmd() ([]byte, error) {
	sigCmd := c.acctConfig.SignatureCmd
	cmd := exec.Command("sh", "-c", sigCmd)
	signature, err := cmd.Output()
	if err != nil {
		return nil, err
	}
	return signature, nil
}

func (c *Composer) readSignatureFromFile() []byte {
	sigFile := c.acctConfig.SignatureFile
	if sigFile == "" {
		return nil
	}
	sigFile, err := homedir.Expand(sigFile)
	if err != nil {
		return nil
	}
	signature, err := os.ReadFile(sigFile)
	if err != nil {
		c.aerc.PushError(
			fmt.Sprintf(" Error loading signature from file: %v", sigFile))
		return nil
	}
	return signature
}

func (c *Composer) FocusTerminal() *Composer {
	if c.editor == nil {
		return c
	}
	c.focusable[c.focused].Focus(false)
	c.focused = len(c.editors)
	c.focusable[c.focused].Focus(true)
	return c
}

// OnHeaderChange registers an OnChange callback for the specified header.
func (c *Composer) OnHeaderChange(header string, fn func(subject string)) {
	if editor, ok := c.editors[strings.ToLower(header)]; ok {
		editor.OnChange(func() {
			fn(editor.input.String())
		})
	}
}

// OnFocusLost registers an OnFocusLost callback for the specified header.
func (c *Composer) OnFocusLost(header string, fn func(input string) bool) {
	if editor, ok := c.editors[strings.ToLower(header)]; ok {
		editor.OnFocusLost(func() {
			fn(editor.input.String())
		})
	}
}

func (c *Composer) OnClose(fn func(composer *Composer)) {
	c.onClose = append(c.onClose, fn)
}

func (c *Composer) Draw(ctx *ui.Context) {
	c.width = ctx.Width()
	c.grid.Draw(ctx)
}

func (c *Composer) Invalidate() {
	c.grid.Invalidate()
}

func (c *Composer) OnInvalidate(fn func(d ui.Drawable)) {
	c.grid.OnInvalidate(func(_ ui.Drawable) {
		fn(c)
	})
}

func (c *Composer) Close() {
	for _, onClose := range c.onClose {
		onClose(c)
	}
	if c.email != nil {
		path := c.email.Name()
		c.email.Close()
		os.Remove(path)
		c.email = nil
	}
	if c.editor != nil {
		c.editor.Destroy()
		c.editor = nil
	}
}

func (c *Composer) Bindings() string {
	switch c.editor {
	case nil:
		return "compose::review"
	case c.focusable[c.focused]:
		return "compose::editor"
	default:
		return "compose"
	}
}

func (c *Composer) Event(event tcell.Event) bool {
	if c.editor != nil {
		return c.focusable[c.focused].Event(event)
	}
	return false
}

func (c *Composer) MouseEvent(localX int, localY int, event tcell.Event) {
	c.grid.MouseEvent(localX, localY, event)
	for _, e := range c.focusable {
		he, ok := e.(*headerEditor)
		if ok && he.focused {
			c.FocusEditor(he.name)
		}
	}
}

func (c *Composer) Focus(focus bool) {
	c.focusable[c.focused].Focus(focus)
}

func (c *Composer) Config() *config.AccountConfig {
	return c.acctConfig
}

func (c *Composer) Account() *AccountView {
	return c.acct
}

func (c *Composer) Worker() *types.Worker {
	return c.worker
}

// PrepareHeader finalizes the header, adding the value from the editors
func (c *Composer) PrepareHeader() (*mail.Header, error) {
	for _, editor := range c.editors {
		editor.storeValue()
	}

	// 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
		}
	}
	if !c.header.Has("Date") {
		c.header.SetDate(time.Now())
	}
	return c.header, nil
}

func getSenderEmail(c *Composer) (string, error) {
	// add the from: field also to the 'recipients' list
	if c.acctConfig.From == "" {
		return "", errors.New("No 'From' configured for this account")
	}
	from, err := mail.ParseAddress(c.acctConfig.From)
	if err != nil {
		return "", errors.Wrap(err, "ParseAddress(config.From)")
	}
	return from.Address, nil
}

func getRecipientsEmail(c *Composer) ([]string, error) {
	h, err := c.PrepareHeader()
	if err != nil {
		return nil, errors.Wrap(err, "PrepareHeader")
	}

	// collect all 'recipients' from header (to:, cc:, bcc:)
	rcpts := make(map[string]bool)
	for _, key := range []string{"to", "cc", "bcc"} {
		list, err := h.AddressList(key)
		if err != nil {
			continue
		}
		for _, entry := range list {
			if entry != nil {
				rcpts[entry.Address] = true
			}
		}
	}

	// return email addresses as string slice
	results := []string{}
	for email := range rcpts {
		results = append(results, email)
	}
	return results, nil
}

func (c *Composer) WriteMessage(header *mail.Header, writer io.Writer) error {
	if err := c.reloadEmail(); err != nil {
		return err
	}

	if c.sign || c.encrypt {

		var signedHeader mail.Header
		signedHeader.SetContentType("text/plain", nil)

		var buf bytes.Buffer
		var cleartext io.WriteCloser
		var err error

		signer := ""
		if c.sign {
			if c.acctConfig.PgpKeyId != "" {
				signer = c.acctConfig.PgpKeyId
			} else {
				signer, err = getSenderEmail(c)
				if err != nil {
					return err
				}
			}
		}

		if c.encrypt {
			rcpts, err := getRecipientsEmail(c)
			if err != nil {
				return err
			}
			cleartext, err = c.aerc.Crypto.Encrypt(&buf, rcpts, signer, c.aerc.DecryptKeys, header)
			if err != nil {
				return err
			}
		} else {
			cleartext, err = c.aerc.Crypto.Sign(&buf, signer, c.aerc.DecryptKeys, header)
			if err != nil {
				return err
			}
		}

		err = writeMsgImpl(c, &signedHeader, cleartext)
		if err != nil {
			return err
		}
		err = cleartext.Close()
		if err != nil {
			return err
		}
		_, err = io.Copy(writer, &buf)
		if err != nil {
			return fmt.Errorf("failed to write message: %w", err)
		}
		return nil

	} else {
		return writeMsgImpl(c, header, writer)
	}
}

func writeMsgImpl(c *Composer, header *mail.Header, writer io.Writer) error {
	if len(c.attachments) == 0 && len(c.textParts) == 0 {
		// no attachments
		return writeInlineBody(header, c.email, writer)
	} else {
		// with attachments
		w, err := mail.CreateWriter(writer, *header)
		if err != nil {
			return errors.Wrap(err, "CreateWriter")
		}
		parts := []*lib.Part{
			lib.NewPart(
				"text/plain",
				map[string]string{"Charset": "UTF-8"},
				c.email,
			),
		}
		if err := writeMultipartBody(append(parts, c.textParts...), w); err != nil {
			return errors.Wrap(err, "writeMultipartBody")
		}
		for _, a := range c.attachments {
			if err := a.WriteTo(w); err != nil {
				return errors.Wrap(err, "writeAttachment")
			}
		}
		w.Close()
	}
	return nil
}

func writeInlineBody(header *mail.Header, body io.Reader, writer io.Writer) error {
	header.SetContentType("text/plain", map[string]string{"charset": "UTF-8"})
	w, err := mail.CreateSingleInlineWriter(writer, *header)
	if err != nil {
		return errors.Wrap(err, "CreateSingleInlineWriter")
	}
	defer w.Close()
	if _, err := io.Copy(w, body); err != nil {
		return errors.Wrap(err, "io.Copy")
	}
	return nil
}

// write the message body to the multipart message
func writeMultipartBody(parts []*lib.Part, w *mail.Writer) error {
	bi, err := w.CreateInline()
	if err != nil {
		return errors.Wrap(err, "CreateInline")
	}
	defer bi.Close()

	for _, part := range parts {
		bh := mail.InlineHeader{}
		bh.SetContentType(part.MimeType, part.Params)
		bw, err := bi.CreatePart(bh)
		if err != nil {
			return errors.Wrap(err, "CreatePart")
		}
		defer bw.Close()
		if _, err := io.Copy(bw, part.Body); err != nil {
			return errors.Wrap(err, "io.Copy")
		}
	}

	return nil
}

func (c *Composer) GetAttachments() []string {
	var names []string
	for _, a := range c.attachments {
		names = append(names, a.Name())
	}
	return names
}

func (c *Composer) AddAttachment(path string) {
	c.attachments = append(c.attachments, lib.NewFileAttachment(path))
	c.resetReview()
}

func (c *Composer) AddPartAttachment(name string, mimetype string, params map[string]string, body io.Reader) {
	c.attachments = append(c.attachments, lib.NewPartAttachment(
		lib.NewPart(mimetype, params, body), name,
	))
	c.resetReview()
}

func (c *Composer) DeleteAttachment(name string) error {
	for i, a := range c.attachments {
		if a.Name() == name {
			c.attachments = append(c.attachments[:i], c.attachments[i+1:]...)
			c.resetReview()
			return nil
		}
	}

	return errors.New("attachment does not exist")
}

func (c *Composer) resetReview() {
	if c.review != nil {
		c.grid.RemoveChild(c.review)
		c.review = newReviewMessage(c, nil)
		c.grid.AddChild(c.review).At(3, 0)
	}
}

func (c *Composer) termEvent(event tcell.Event) bool {
	if event, ok := event.(*tcell.EventMouse); ok {
		if event.Buttons() == tcell.Button1 {
			c.FocusTerminal()
			return true
		}
	}
	return false
}

func (c *Composer) termClosed(err error) {
	c.grid.RemoveChild(c.editor)
	c.review = newReviewMessage(c, err)
	c.grid.AddChild(c.review).At(3, 0)
	c.editor.Destroy()
	c.editor = nil
	c.focusable = c.focusable[:len(c.focusable)-1]
	if c.focused >= len(c.focusable) {
		c.focused = len(c.focusable) - 1
	}
}

func (c *Composer) ShowTerminal() {
	if c.editor != nil {
		return
	}
	if c.review != nil {
		c.grid.RemoveChild(c.review)
	}
	editorName := c.config.Compose.Editor
	if editorName == "" {
		editorName = os.Getenv("EDITOR")
	}
	if editorName == "" {
		editorName = "vi"
	}
	editor := exec.Command("/bin/sh", "-c", editorName+" "+c.email.Name())
	c.editor, _ = NewTerminal(editor) // TODO: handle error
	c.editor.OnEvent = c.termEvent
	c.editor.OnClose = c.termClosed
	c.grid.AddChild(c.editor).At(3, 0)
	c.focusable = append(c.focusable, c.editor)
}

func (c *Composer) PrevField() {
	c.focusable[c.focused].Focus(false)
	c.focused--
	if c.focused == -1 {
		c.focused = len(c.focusable) - 1
	}
	c.focusable[c.focused].Focus(true)
}

func (c *Composer) NextField() {
	c.focusable[c.focused].Focus(false)
	c.focused = (c.focused + 1) % len(c.focusable)
	c.focusable[c.focused].Focus(true)
}

func (c *Composer) FocusEditor(editor string) {
	editor = strings.ToLower(editor)
	c.focusable[c.focused].Focus(false)
	for i, f := range c.focusable {
		e := f.(*headerEditor)
		if strings.ToLower(e.name) == editor {
			c.focused = i
			break
		}
	}
	c.focusable[c.focused].Focus(true)
}

// AddEditor appends a new header editor to the compose window.
func (c *Composer) AddEditor(header string, value string, appendHeader bool) {
	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 {
		uiConfig := c.acct.UiConfig()
		e := newHeaderEditor(header, c.header, uiConfig)
		if uiConfig.CompletionPopovers {
			e.input.TabComplete(c.completer.ForHeader(header), uiConfig.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],
		)
		editor = e
	}

	if appendHeader {
		currVal := editor.input.String()
		if currVal != "" {
			value = strings.TrimSpace(currVal) + ", " + value
		}
	}
	if value != "" || appendHeader {
		c.editors[header].input.Set(value)
		editor.storeValue()
	}
	if value == "" {
		c.FocusEditor(c.editors[header].name)
	}
	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]
		},
	)

	if c.grid == nil {
		c.grid = ui.NewGrid().Columns([]ui.GridSpec{
			{Strategy: ui.SIZE_WEIGHT, Size: ui.Const(1)},
		})
	}
	crHeight := 0
	if c.sign || c.encrypt {
		crHeight = 1
	}
	c.grid.Rows([]ui.GridSpec{
		{Strategy: ui.SIZE_EXACT, Size: ui.Const(height)},
		{Strategy: ui.SIZE_EXACT, Size: ui.Const(crHeight)},
		{Strategy: ui.SIZE_EXACT, Size: ui.Const(1)},
		{Strategy: ui.SIZE_WEIGHT, Size: ui.Const(1)},
	})

	if c.heditors != nil {
		c.grid.RemoveChild(c.heditors)
	}
	borderStyle := c.acct.UiConfig().GetStyle(config.STYLE_BORDER)
	borderChar := c.acct.UiConfig().BorderCharHorizontal
	c.heditors = heditors
	c.grid.AddChild(c.heditors).At(0, 0)
	c.grid.AddChild(ui.NewFill(borderChar, borderStyle)).At(2, 0)
}

func (c *Composer) reloadEmail() error {
	name := c.email.Name()
	c.email.Close()
	file, err := os.Open(name)
	if err != nil {
		return errors.Wrap(err, "ReloadEmail")
	}
	c.email = file
	return nil
}

type headerEditor struct {
	name     string
	header   *mail.Header
	focused  bool
	input    *ui.TextInput
	uiConfig *config.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":
		if strings.TrimSpace(val) == "" {
			// if header is empty, delete it
			he.header.Del(he.name)
			return
		}
		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)
		}
	default:
		he.header.SetText(he.name, val)
	}
}

func (he *headerEditor) Draw(ctx *ui.Context) {
	name := textproto.CanonicalMIMEHeaderKey(he.name)
	// Extra character to put a blank cell between the header and the input
	size := runewidth.StringWidth(name+":") + 1
	defaultStyle := he.uiConfig.GetStyle(config.STYLE_DEFAULT)
	headerStyle := he.uiConfig.GetStyle(config.STYLE_HEADER)
	ctx.Fill(0, 0, size, ctx.Height(), ' ', defaultStyle)
	ctx.Printf(0, 0, headerStyle, "%s:", name)
	he.input.Draw(ctx.Subcontext(size, 0, ctx.Width()-size, 1))
}

func (he *headerEditor) MouseEvent(localX int, localY int, event tcell.Event) {
	if event, ok := event.(*tcell.EventMouse); ok {
		if event.Buttons() == tcell.Button1 {
			he.focused = true
		}

		width := runewidth.StringWidth(he.name + " ")
		if localX >= width {
			he.input.MouseEvent(localX-width, localY, event)
		}
	}
}

func (he *headerEditor) Invalidate() {
	he.input.Invalidate()
}

func (he *headerEditor) OnInvalidate(fn func(ui.Drawable)) {
	he.input.OnInvalidate(func(_ ui.Drawable) {
		fn(he)
	})
}

func (he *headerEditor) Focus(focused bool) {
	he.focused = focused
	he.input.Focus(focused)
}

func (he *headerEditor) Event(event tcell.Event) bool {
	return he.input.Event(event)
}

func (he *headerEditor) OnChange(fn func()) {
	he.input.OnChange(func(_ *ui.TextInput) {
		fn()
	})
}

func (he *headerEditor) OnFocusLost(fn func()) {
	he.input.OnFocusLost(func(_ *ui.TextInput) {
		fn()
	})
}

type reviewMessage struct {
	composer *Composer
	grid     *ui.Grid
}

var reviewCommands = [][]string{
	{":send<enter>", "Send"},
	{":edit<enter>", "Edit"},
	{":attach<space>", "Add attachment"},
	{":detach<space>", "Remove attachment"},
	{":postpone<enter>", "Postpone"},
	{":abort<enter>", "Abort (discard message, no confirmation)"},
	{":choose -o d discard abort -o p postpone postpone<enter>", "Abort or postpone"},
}

func newReviewMessage(composer *Composer, err error) *reviewMessage {
	bindings := composer.config.MergeContextualBinds(
		composer.config.Bindings.ComposeReview,
		config.BIND_CONTEXT_ACCOUNT,
		composer.acctConfig.Name,
		"compose::review",
	)

	var actions []string

	for _, command := range reviewCommands {
		cmd := command[0]
		name := command[1]
		strokes, _ := config.ParseKeyStrokes(cmd)
		var inputs []string
		for _, input := range bindings.GetReverseBindings(strokes) {
			inputs = append(inputs, config.FormatKeyStrokes(input))
		}
		actions = append(actions, fmt.Sprintf("  %-6s  %-40s  %s",
			strings.Join(inputs, ", "), name, cmd))
	}

	spec := []ui.GridSpec{
		{Strategy: ui.SIZE_EXACT, Size: ui.Const(1)},
	}
	for i := 0; i < len(actions)-1; i++ {
		spec = append(spec, ui.GridSpec{Strategy: ui.SIZE_EXACT, Size: ui.Const(1)})
	}
	spec = append(spec, ui.GridSpec{Strategy: ui.SIZE_EXACT, Size: ui.Const(2)})
	spec = append(spec, ui.GridSpec{Strategy: ui.SIZE_EXACT, Size: ui.Const(1)})
	for i := 0; i < len(composer.attachments)-1; i++ {
		spec = append(spec, ui.GridSpec{Strategy: ui.SIZE_EXACT, Size: ui.Const(1)})
	}
	if len(composer.textParts) > 0 {
		spec = append(spec, ui.GridSpec{Strategy: ui.SIZE_EXACT, Size: ui.Const(1)})
		spec = append(spec, ui.GridSpec{Strategy: ui.SIZE_EXACT, Size: ui.Const(1)})
		for i := 0; i < len(composer.textParts); i++ {
			spec = append(spec, ui.GridSpec{Strategy: ui.SIZE_EXACT, Size: ui.Const(1)})
		}
	}
	// make the last element fill remaining space
	spec = append(spec, ui.GridSpec{Strategy: ui.SIZE_WEIGHT, Size: ui.Const(1)})

	grid := ui.NewGrid().Rows(spec).Columns([]ui.GridSpec{
		{Strategy: ui.SIZE_WEIGHT, Size: ui.Const(1)},
	})

	uiConfig := composer.acct.UiConfig()

	if err != nil {
		grid.AddChild(ui.NewText(err.Error(), uiConfig.GetStyle(config.STYLE_ERROR)))
		grid.AddChild(ui.NewText("Press [q] to close this tab.",
			uiConfig.GetStyle(config.STYLE_DEFAULT))).At(1, 0)
	} else {
		grid.AddChild(ui.NewText("Send this email?",
			uiConfig.GetStyle(config.STYLE_TITLE))).At(0, 0)
		i := 1
		for _, action := range actions {
			grid.AddChild(ui.NewText(action,
				uiConfig.GetStyle(config.STYLE_DEFAULT))).At(i, 0)
			i += 1
		}
		grid.AddChild(ui.NewText("Attachments:",
			uiConfig.GetStyle(config.STYLE_TITLE))).At(i, 0)
		i += 1
		if len(composer.attachments) == 0 {
			grid.AddChild(ui.NewText("(none)",
				uiConfig.GetStyle(config.STYLE_DEFAULT))).At(i, 0)
			i += 1
		} else {
			for _, a := range composer.attachments {
				grid.AddChild(ui.NewText(a.Name(), uiConfig.GetStyle(config.STYLE_DEFAULT))).
					At(i, 0)
				i += 1
			}
		}
		if len(composer.textParts) > 0 {
			grid.AddChild(ui.NewText("Parts:",
				uiConfig.GetStyle(config.STYLE_TITLE))).At(i, 0)
			i += 1
			grid.AddChild(ui.NewText("text/plain", uiConfig.GetStyle(config.STYLE_DEFAULT))).At(i, 0)
			i += 1
			for _, p := range composer.textParts {
				grid.AddChild(ui.NewText(p.MimeType, uiConfig.GetStyle(config.STYLE_DEFAULT))).At(i, 0)
				i += 1
			}

		}
	}

	return &reviewMessage{
		composer: composer,
		grid:     grid,
	}
}

func (rm *reviewMessage) Invalidate() {
	rm.grid.Invalidate()
}

func (rm *reviewMessage) OnInvalidate(fn func(ui.Drawable)) {
	rm.grid.OnInvalidate(func(_ ui.Drawable) {
		fn(rm)
	})
}

func (rm *reviewMessage) Draw(ctx *ui.Context) {
	rm.grid.Draw(ctx)
}

type cryptoStatus struct {
	title         string
	status        *ui.Text
	uiConfig      *config.UIConfig
	signKey       string
	setEncOneShot bool
}

func newCryptoStatus(uiConfig *config.UIConfig) *cryptoStatus {
	defaultStyle := uiConfig.GetStyle(config.STYLE_DEFAULT)
	return &cryptoStatus{
		title:         "Security",
		status:        ui.NewText("", defaultStyle),
		uiConfig:      uiConfig,
		signKey:       "",
		setEncOneShot: true,
	}
}

func (cs *cryptoStatus) Draw(ctx *ui.Context) {
	// Extra character to put a blank cell between the header and the input
	size := runewidth.StringWidth(cs.title+":") + 1
	defaultStyle := cs.uiConfig.GetStyle(config.STYLE_DEFAULT)
	titleStyle := cs.uiConfig.GetStyle(config.STYLE_HEADER)
	ctx.Fill(0, 0, size, ctx.Height(), ' ', defaultStyle)
	ctx.Printf(0, 0, titleStyle, "%s:", cs.title)
	cs.status.Draw(ctx.Subcontext(size, 0, ctx.Width()-size, 1))
}

func (cs *cryptoStatus) Invalidate() {
	cs.status.Invalidate()
}

func (cs *cryptoStatus) OnInvalidate(fn func(ui.Drawable)) {
	cs.status.OnInvalidate(func(_ ui.Drawable) {
		fn(cs)
	})
}

func (c *Composer) checkEncryptionKeys(_ string) bool {
	rcpts, err := getRecipientsEmail(c)
	if err != nil {
		// checkEncryptionKeys gets registered as a callback and must
		// explicitly call c.SetEncrypt(false) when encryption is not possible
		c.SetEncrypt(false)
		st := fmt.Sprintf("Cannot encrypt: %v", err)
		c.aerc.statusline.PushError(st)
		return false
	}
	var mk []string
	for _, rcpt := range rcpts {
		key, err := c.aerc.Crypto.GetKeyId(rcpt)
		if err != nil || key == "" {
			mk = append(mk, rcpt)
		}
	}
	if len(mk) > 0 {
		c.SetEncrypt(false)
		st := fmt.Sprintf("Cannot encrypt, missing keys: %s", strings.Join(mk, ", "))
		c.aerc.statusline.PushError(st)
		return false
	}
	// If callbacks were registered, encrypt will be set when user removes
	// recipients with missing keys
	c.encrypt = true
	err = c.updateCrypto()
	if err != nil {
		logging.Warnf("failed update crypto: %v", err)
	}
	return true
}