6 files changed, 619 insertions, 30 deletions

diff --git a/commands/commands.go b/commands/commands.go
index 0a7050e9..f50a1e8a 100644
--- a/commands/commands.go
+++ b/commands/commands.go
@@ -23,6 +23,16 @@ type Command interface {
 	Complete(*widgets.Aerc, []string) []string
 }
 
+type OptionsProvider interface {
+	Command
+	Options() string
+}
+
+type OptionCompleter interface {
+	OptionsProvider
+	CompleteOption(*widgets.Aerc, rune, string) []string
+}
+
 type Commands map[string]Command
 
 func NewCommands() *Commands {
@@ -131,49 +141,98 @@ func (cmds *Commands) ExecuteCommand(
 	return NoSuchCommand(args[0])
 }
 
-func (cmds *Commands) GetCompletions(aerc *widgets.Aerc, cmd string) []string {
-	args, err := shlex.Split(cmd)
+// GetCompletions returns the completion options and the command prefix
+func (cmds *Commands) GetCompletions(
+	aerc *widgets.Aerc, cmd string,
+) (options []string, prefix string) {
+	log.Tracef("completing command: %s", cmd)
+
+	// start completion
+	args, err := splitCmd(cmd)
 	if err != nil {
-		return nil
+		return
 	}
 
 	// nothing entered, list all commands
 	if len(args) == 0 {
-		names := cmds.Names()
-		sort.Strings(names)
-		return names
+		options = cmds.Names()
+		sort.Strings(options)
+		return
+	}
+
+	// complete command name
+	spaceTerminated := cmd[len(cmd)-1] == ' '
+	if len(args) == 1 && !spaceTerminated {
+		for _, n := range cmds.Names() {
+			options = append(options, n+" ")
+		}
+		options = CompletionFromList(aerc, options, args)
+
+		return
+	}
+
+	// look for command in dictionary
+	c, ok := cmds.dict()[args[0]]
+	if !ok {
+		return
 	}
 
 	// complete options
-	if len(args) > 1 || cmd[len(cmd)-1] == ' ' {
-		if cmd, ok := cmds.dict()[args[0]]; ok {
-			var completions []string
-			if len(args) > 1 {
-				completions = cmd.Complete(aerc, args[1:])
-			} else {
-				completions = cmd.Complete(aerc, []string{})
+	var spec string
+	if provider, ok := c.(OptionsProvider); ok {
+		spec = provider.Options()
+	}
+
+	parser, err := newParser(cmd, spec, spaceTerminated)
+	if err != nil {
+		log.Debugf("completion parser failed: %v", err)
+		return
+	}
+
+	switch parser.kind {
+	case SHORT_OPTION:
+		for _, r := range strings.ReplaceAll(spec, ":", "") {
+			if strings.ContainsRune(parser.flag, r) {
+				continue
 			}
-			if completions != nil && len(completions) == 0 {
-				return nil
+			option := string(r)
+			if strings.Contains(spec, option+":") {
+				option += " "
 			}
-
-			options := make([]string, 0)
-			for _, option := range completions {
-				options = append(options, args[0]+" "+option)
+			options = append(options, option)
+		}
+		prefix = cmd
+	case OPTION_ARGUMENT:
+		cmpl, ok := c.(OptionCompleter)
+		if !ok {
+			return
+		}
+		stem := cmd
+		if parser.arg != "" {
+			stem = strings.TrimSuffix(cmd, parser.arg)
+		}
+		pad := ""
+		if !strings.HasSuffix(stem, " ") {
+			pad += " "
+		}
+		s := parser.flag
+		r := rune(s[len(s)-1])
+		for _, option := range cmpl.CompleteOption(aerc, r, parser.arg) {
+			options = append(options, pad+escape(option)+" ")
+		}
+		prefix = stem
+	case OPERAND:
+		stem := strings.Join(args[:parser.optind], " ")
+		for _, option := range c.Complete(aerc, args[1:]) {
+			if strings.Contains(option, "  ") {
+				option = escape(option)
 			}
-			return options
+			options = append(options, " "+option)
 		}
-		return nil
+		prefix = stem
 	}
 
-	// complete available commands
-	names := cmds.Names()
-	options := FilterList(names, args[0], "", aerc.SelectedAccountUiConfig().FuzzyComplete)
-
-	if len(options) > 0 {
-		return options
-	}
-	return nil
+	return
 }
 
 func GetFolders(aerc *widgets.Aerc, args []string) []string {
@@ -246,3 +305,19 @@ func hasUpper(s string) bool {
 	}
 	return false
 }
+
+// splitCmd splits the command into arguments
+func splitCmd(cmd string) ([]string, error) {
+	args, err := shlex.Split(cmd)
+	if err != nil {
+		return nil, err
+	}
+	return args, nil
+}
+
+func escape(s string) string {
+	if strings.Contains(s, " ") {
+		return strings.ReplaceAll(s, " ", "\\ ")
+	}
+	return s
+}
diff --git a/commands/completion_helpers.go b/commands/completion_helpers.go
new file mode 100644
index 00000000..96a423ee
--- /dev/null
+++ b/commands/completion_helpers.go
@@ -0,0 +1,78 @@
+package commands
+
+import (
+	"fmt"
+	"net/mail"
+	"strings"
+
+	"git.sr.ht/~rjarry/aerc/completer"
+	"git.sr.ht/~rjarry/aerc/config"
+	"git.sr.ht/~rjarry/aerc/log"
+	"git.sr.ht/~rjarry/aerc/widgets"
+)
+
+// GetAddress uses the address-book-cmd for address completion
+func GetAddress(aerc *widgets.Aerc, search string) []string {
+	var options []string
+
+	cmd := aerc.SelectedAccount().AccountConfig().AddressBookCmd
+	if cmd == "" {
+		cmd = config.Compose.AddressBookCmd
+		if cmd == "" {
+			return nil
+		}
+	}
+
+	cmpl := completer.New(cmd, func(err error) {
+		aerc.PushError(
+			fmt.Sprintf("could not complete header: %v", err))
+		log.Warnf("could not complete header: %v", err)
+	})
+
+	if len(search) > config.Ui.CompletionMinChars && cmpl != nil {
+		addrList, _ := cmpl.ForHeader("to")(search)
+		for _, full := range addrList {
+			addr, err := mail.ParseAddress(full)
+			if err != nil {
+				continue
+			}
+			options = append(options, addr.Address)
+		}
+	}
+
+	return options
+}
+
+// GetFlagList returns a list of available flags for completion
+func GetFlagList() []string {
+	return []string{"Seen", "Answered", "Flagged"}
+}
+
+// GetDateList returns a list of date terms for completion
+func GetDateList() []string {
+	return []string{
+		"today", "yesterday", "this_week", "this_month",
+		"this_year", "last_week", "last_month", "last_year",
+		"Monday", "Tuesday", "Wednesday", "Thursday", "Friday",
+		"Saturday", "Sunday",
+	}
+}
+
+// Operands returns a slice without any option flags or mandatory option
+// arguments
+func Operands(args []string, spec string) []string {
+	var result []string
+	for i := 0; i < len(args); i++ {
+		if s := args[i]; s == "--" {
+			return args[i+1:]
+		} else if strings.HasPrefix(s, "-") && len(spec) > 0 {
+			r := string(s[len(s)-1]) + ":"
+			if strings.Contains(spec, r) {
+				i++
+			}
+			continue
+		}
+		result = append(result, args[i])
+	}
+	return result
+}
diff --git a/commands/completion_helpers_test.go b/commands/completion_helpers_test.go
new file mode 100644
index 00000000..876dc26d
--- /dev/null
+++ b/commands/completion_helpers_test.go
@@ -0,0 +1,44 @@
+package commands_test
+
+import (
+	"strings"
+	"testing"
+
+	"git.sr.ht/~rjarry/aerc/commands"
+)
+
+func TestCommands_Operand(t *testing.T) {
+	tests := []struct {
+		args []string
+		spec string
+		want string
+	}{
+		{
+			args: []string{"cmd", "-a", "-b", "arg1", "-c", "bla"},
+			spec: "ab:c",
+			want: "cmdbla",
+		},
+		{
+			args: []string{"cmd", "-a", "-b", "arg1", "-c", "--", "bla"},
+			spec: "ab:c",
+			want: "bla",
+		},
+		{
+			args: []string{"cmd", "-a", "-b", "arg1", "-c", "bla"},
+			spec: "ab:c:",
+			want: "cmd",
+		},
+		{
+			args: nil,
+			spec: "ab:c:",
+			want: "",
+		},
+	}
+	for i, test := range tests {
+		arg := strings.Join(commands.Operands(test.args, test.spec), "")
+		if arg != test.want {
+			t.Errorf("failed test %d: want '%s', got '%s'", i,
+				test.want, arg)
+		}
+	}
+}
diff --git a/commands/parser.go b/commands/parser.go
new file mode 100644
index 00000000..e8146506
--- /dev/null
+++ b/commands/parser.go
@@ -0,0 +1,134 @@
+package commands
+
+import (
+	"strings"
+)
+
+type completionType int
+
+const (
+	NONE completionType = iota
+	COMMAND
+	OPERAND
+	SHORT_OPTION
+	OPTION_ARGUMENT
+)
+
+type parser struct {
+	tokens []string
+	optind int
+	spec   string
+	space  bool
+	kind   completionType
+	flag   string
+	arg    string
+	err    error
+}
+
+func newParser(cmd, spec string, spaceTerminated bool) (*parser, error) {
+	args, err := splitCmd(cmd)
+	if err != nil {
+		return nil, err
+	}
+
+	p := &parser{
+		tokens: args,
+		optind: 0,
+		spec:   spec,
+		space:  spaceTerminated,
+		kind:   NONE,
+		flag:   "",
+		arg:    "",
+		err:    nil,
+	}
+
+	state := command
+	for state != nil {
+		state = state(p)
+	}
+
+	return p, p.err
+}
+
+func (p *parser) empty() bool {
+	return len(p.tokens) == 0
+}
+
+func (p *parser) peek() string {
+	return p.tokens[0]
+}
+
+func (p *parser) advance() string {
+	if p.empty() {
+		return ""
+	}
+	tok := p.tokens[0]
+	p.tokens = p.tokens[1:]
+	p.optind++
+	return tok
+}
+
+func (p *parser) set(t completionType) {
+	p.kind = t
+}
+
+func (p *parser) hasArgument() bool {
+	n := len(p.flag)
+	if n > 0 {
+		s := string(p.flag[n-1]) + ":"
+		return strings.Contains(p.spec, s)
+	}
+	return false
+}
+
+type stateFn func(*parser) stateFn
+
+func command(p *parser) stateFn {
+	p.set(COMMAND)
+	p.advance()
+	return peek(p)
+}
+
+func peek(p *parser) stateFn {
+	if p.empty() {
+		if p.space {
+			return operand
+		}
+		return nil
+	}
+	if p.spec == "" {
+		return operand
+	}
+	s := p.peek()
+	switch {
+	case s == "--":
+		p.advance()
+	case strings.HasPrefix(s, "-"):
+		return short_option
+	}
+	return operand
+}
+
+func short_option(p *parser) stateFn {
+	p.set(SHORT_OPTION)
+	tok := p.advance()
+	p.flag = tok[1:]
+	if p.hasArgument() {
+		return option_argument
+	}
+	return peek(p)
+}
+
+func option_argument(p *parser) stateFn {
+	p.set(OPTION_ARGUMENT)
+	p.arg = p.advance()
+	if p.empty() && len(p.arg) == 0 {
+		return nil
+	}
+	return peek(p)
+}
+
+func operand(p *parser) stateFn {
+	p.set(OPERAND)
+	return nil
+}
diff --git a/commands/parser_test.go b/commands/parser_test.go
new file mode 100644
index 00000000..d6ccd385
--- /dev/null
+++ b/commands/parser_test.go
@@ -0,0 +1,258 @@
+package commands
+
+import (
+	"testing"
+)
+
+var parserTests = []struct {
+	name       string
+	cmd        string
+	wantType   completionType
+	wantFlag   string
+	wantArg    string
+	wantOptind int
+}{
+	{
+		name:       "empty command",
+		cmd:        "",
+		wantType:   COMMAND,
+		wantFlag:   "",
+		wantArg:    "",
+		wantOptind: 0,
+	},
+	{
+		name:       "command only",
+		cmd:        "cmd",
+		wantType:   COMMAND,
+		wantFlag:   "",
+		wantArg:    "",
+		wantOptind: 1,
+	},
+	{
+		name:       "with space",
+		cmd:        "cmd ",
+		wantType:   OPERAND,
+		wantFlag:   "",
+		wantArg:    "",
+		wantOptind: 1,
+	},
+	{
+		name:       "with two spaces",
+		cmd:        "cmd  ",
+		wantType:   OPERAND,
+		wantFlag:   "",
+		wantArg:    "",
+		wantOptind: 1,
+	},
+	{
+		name:       "with single option flag",
+		cmd:        "cmd -",
+		wantType:   SHORT_OPTION,
+		wantFlag:   "",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with single option flag two spaces",
+		cmd:        "cmd  -",
+		wantType:   SHORT_OPTION,
+		wantFlag:   "",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with single option flag completed",
+		cmd:        "cmd -a",
+		wantType:   SHORT_OPTION,
+		wantFlag:   "a",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with single option flag completed and space",
+		cmd:        "cmd -a ",
+		wantType:   OPERAND,
+		wantFlag:   "a",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with single option flag completed and two spaces",
+		cmd:        "cmd -a ",
+		wantType:   OPERAND,
+		wantFlag:   "a",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with two single option flag completed",
+		cmd:        "cmd -b -a",
+		wantType:   SHORT_OPTION,
+		wantFlag:   "a",
+		wantArg:    "",
+		wantOptind: 3,
+	},
+	{
+		name:       "with two single option flag combined",
+		cmd:        "cmd -ab",
+		wantType:   SHORT_OPTION,
+		wantFlag:   "ab",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with two single option flag and space",
+		cmd:        "cmd -ab ",
+		wantType:   OPERAND,
+		wantFlag:   "ab",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with mandatory option flag",
+		cmd:        "cmd -f",
+		wantType:   OPTION_ARGUMENT,
+		wantFlag:   "f",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with mandatory option flag and space",
+		cmd:        "cmd -f ",
+		wantType:   OPTION_ARGUMENT,
+		wantFlag:   "f",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with mandatory option flag and two spaces",
+		cmd:        "cmd -f  ",
+		wantType:   OPTION_ARGUMENT,
+		wantFlag:   "f",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with mandatory option flag and completed",
+		cmd:        "cmd -f a",
+		wantType:   OPTION_ARGUMENT,
+		wantFlag:   "f",
+		wantArg:    "a",
+		wantOptind: 3,
+	},
+	{
+		name:       "with mandatory option flag and completed quote",
+		cmd:        "cmd -f 'a b'",
+		wantType:   OPTION_ARGUMENT,
+		wantFlag:   "f",
+		wantArg:    "a b",
+		wantOptind: 3,
+	},
+	{
+		name:       "with mandatory option flag and operand",
+		cmd:        "cmd -f 'a b' hello",
+		wantType:   OPERAND,
+		wantFlag:   "f",
+		wantArg:    "a b",
+		wantOptind: 3,
+	},
+	{
+		name:       "with mandatory option flag and two spaces between",
+		cmd:        "cmd -f  a",
+		wantType:   OPTION_ARGUMENT,
+		wantFlag:   "f",
+		wantArg:    "a",
+		wantOptind: 3,
+	},
+	{
+		name:       "with mandatory option flag and more spaces",
+		cmd:        "cmd -f  a ",
+		wantType:   OPERAND,
+		wantFlag:   "f",
+		wantArg:    "a",
+		wantOptind: 3,
+	},
+	{
+		name:       "with template data",
+		cmd:        "cmd -a {{if .Size}}  hello {{else}} {{end}}",
+		wantType:   OPERAND,
+		wantFlag:   "a",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with operand",
+		cmd:        "cmd -ab /tmp/aerc-",
+		wantType:   OPERAND,
+		wantFlag:   "ab",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+	{
+		name:       "with operand indicator",
+		cmd:        "cmd -ab -- /tmp/aerc-",
+		wantType:   OPERAND,
+		wantFlag:   "ab",
+		wantArg:    "",
+		wantOptind: 3,
+	},
+	{
+		name:       "hyphen connected command",
+		cmd:        "cmd-dmc",
+		wantType:   COMMAND,
+		wantFlag:   "",
+		wantArg:    "",
+		wantOptind: 1,
+	},
+	{
+		name:       "incomplete hyphen connected command",
+		cmd:        "cmd-",
+		wantType:   COMMAND,
+		wantFlag:   "",
+		wantArg:    "",
+		wantOptind: 1,
+	},
+	{
+		name:       "hyphen connected command with option",
+		cmd:        "cmd-dmc -a",
+		wantType:   SHORT_OPTION,
+		wantFlag:   "a",
+		wantArg:    "",
+		wantOptind: 2,
+	},
+}
+
+func TestCommands_Parser(t *testing.T) {
+	for i, test := range parserTests {
+		n := len(test.cmd)
+		spaceTerminated := n > 0 && test.cmd[n-1] == ' '
+		parser, err := newParser(test.cmd, "abf:", spaceTerminated)
+		if err != nil {
+			t.Errorf("parser error: %v", err)
+		}
+
+		if test.wantType != parser.kind {
+			t.Errorf("test %d '%s': completion type does not match: "+
+				"want %d, but got %d", i, test.cmd, test.wantType,
+				parser.kind)
+		}
+
+		if test.wantFlag != parser.flag {
+			t.Errorf("test %d '%s': flag does not match: "+
+				"want %s, but got %s", i, test.cmd, test.wantFlag,
+				parser.flag)
+		}
+
+		if test.wantArg != parser.arg {
+			t.Errorf("test %d '%s': arg does not match: "+
+				"want %s, but got %s", i, test.cmd, test.wantArg,
+				parser.arg)
+		}
+
+		if test.wantOptind != parser.optind {
+			t.Errorf("test %d '%s': optind does not match: "+
+				"want %d, but got %d", i, test.cmd, test.wantOptind,
+				parser.optind)
+		}
+	}
+}
diff --git a/commands/prompt.go b/commands/prompt.go
index 8746bcfe..a93d19a9 100644
--- a/commands/prompt.go
+++ b/commands/prompt.go
@@ -36,7 +36,7 @@ func (Prompt) Complete(aerc *widgets.Aerc, args []string) []string {
 		if hascommand {
 			return nil
 		}
-		cs = GlobalCommands.GetCompletions(aerc, args[1])
+		cs, _ = GlobalCommands.GetCompletions(aerc, args[1])
 	}
 	if cs == nil {
 		return nil