1 files changed, 295 insertions, 0 deletions
diff --git a/internal/cli/query.go b/internal/cli/query.go
new file mode 100644
index 0000000..add170c
--- /dev/null
+++ b/internal/cli/query.go
@@ -0,0 +1,295 @@
+/*******************************************************************************
+*
+* Copyright 2017 Stefan Majewsky <majewsky@gmx.net>
+*
+* This program is free software: you can redistribute it and/or modify it under
+* the terms of the GNU General Public License as published by the Free Software
+* Foundation, either version 3 of the License, or (at your option) any later
+* version.
+*
+* This program is distributed in the hope that it will be useful, but WITHOUT ANY
+* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+* A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License along with
+* this program. If not, see <http://www.gnu.org/licenses/>.
+*
+*******************************************************************************/
+
+package cli
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"regexp"
+	"strconv"
+	"strings"
+
+	terminal "golang.org/x/crypto/ssh/terminal"
+)
+
+//cannot use `var errInterrupted = errors.New("Interrupted!")` because golint
+//complains about the formatting of the error message
+type errInterrupted struct{}
+
+func (e errInterrupted) Error() string {
+	return "Interrupted!"
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// TUI implementation for when stdin is a terminal
+
+type terminalTUI struct {
+	i *Implementation
+}
+
+func (t terminalTUI) Print(w io.Writer, msg string) {
+	w.Write([]byte(msg))
+}
+
+func (t terminalTUI) ReadLine(prompt string) (string, error) {
+	if prompt != "" {
+		t.i.safeStdout().Write([]byte(strings.TrimSpace(prompt) + " "))
+	}
+	str, err := t.i.stdinBuf.ReadString('\n')
+	return strings.TrimSpace(str), err
+}
+
+func (t terminalTUI) Confirm(question string) (bool, error) {
+	out := t.i.safeStdout()
+	out.Write([]byte(strings.TrimSpace(question) + " [y/n] "))
+
+	buf := buffer{Input: t.i.stdin}
+	for {
+		switch string(buf.getNextInput()) {
+		case "y", "Y":
+			out.Write([]byte("-> yes\n"))
+			return true, nil
+		case "n", "N":
+			out.Write([]byte("-> no\n"))
+			return false, nil
+		case "\x03": // Ctrl-C
+			return false, errInterrupted{}
+		}
+	}
+}
+
+//Choice is a thing that the user can choose during Query().
+type Choice struct {
+	//If given, the choice can be selected by pressing the key that
+	//produces this character.
+	Shortcut byte
+	//The display string that describes this choice.
+	Text string
+	//The string to return from Implementation.Query().
+	Return string
+}
+
+func (c Choice) hasShortcut() bool {
+	return c.Shortcut != '\000'
+}
+
+func (t terminalTUI) Query(prompt string, choices ...Choice) (string, error) {
+	if len(choices) == 0 {
+		panic("no choices")
+	}
+
+	//disable line wrap; unexpected wrapping would confuse our cursor-moving code
+	out := t.i.safeStdout()
+	out.Write([]byte("\x1B[?7l"))
+	defer out.Write([]byte("\x1B[?7h"))
+
+	//display question
+	out.Write([]byte(strings.TrimSuffix(prompt, "\n") + "\n"))
+	selected := 0
+
+	buf := buffer{Input: t.i.stdin}
+OUTER:
+	for {
+		displayChoices(out, choices, selected)
+
+		input := buf.getNextInput()
+		if len(input) == 1 {
+			//single character entered - check if a shortcut matches
+			for idx, choice := range choices {
+				if choice.Shortcut == input[0] {
+					selected = idx
+					break OUTER
+				}
+			}
+		}
+
+		switch string(input) {
+		case "\r", "\n":
+			break OUTER
+		case "\x1B[A": // Up arrow key
+			selected--
+			if selected < 0 {
+				selected = 0
+			}
+		case "\x1B[B": // Down arrow key
+			selected++
+			if selected >= len(choices) {
+				selected = len(choices) - 1
+			}
+		case "\x03": // Ctrl-C
+			return "", errInterrupted{}
+		}
+
+		//prepare to re-render choices
+		removeDisplayLines(out, len(choices))
+	}
+
+	//clear query display
+	removeDisplayLines(out, len(choices)+1)
+
+	//display question + chosen answer
+	fmt.Fprintf(out, "%s -> %s\n",
+		strings.TrimSuffix(prompt, "\n"),
+		strings.TrimSpace(choices[selected].Text),
+	)
+
+	return choices[selected].Return, nil
+}
+
+func removeDisplayLines(stdout io.Writer, n int) {
+	for idx := 0; idx < n; idx++ {
+		stdout.Write([]byte("\x1B[A\x1B[2K"))
+	}
+}
+
+func displayChoices(out io.Writer, choices []Choice, selectedIndex int) {
+	hasShortcuts := false
+	for _, choice := range choices {
+		if choice.hasShortcut() {
+			hasShortcuts = true
+			break
+		}
+	}
+
+	for idx, choice := range choices {
+		text := " " + strings.TrimSpace(choice.Text) + " \n"
+		if hasShortcuts {
+			shortcut := choice.Shortcut
+			if !choice.hasShortcut() {
+				shortcut = ' '
+			}
+			text = fmt.Sprintf(" [%c]%s", shortcut, text)
+		}
+
+		if idx == selectedIndex {
+			fmt.Fprintf(out, "\x1B[0;7m%s\x1B[0m", text)
+		} else {
+			out.Write([]byte(text))
+		}
+	}
+}
+
+var ansiEscapeRx = regexp.MustCompile(`^\x1B\[[\x20-\x3F]*[\x40-\x7E]`)
+
+type buffer struct {
+	Input io.Reader
+	buf   [128]byte
+	fill  int
+}
+
+func (b *buffer) getNextInput() []byte {
+	//do we have a simple input character?
+	if b.fill > 0 && b.buf[0] != '\x1B' {
+		result := append([]byte(nil), b.buf[0])
+		copy(b.buf[0:], b.buf[1:])
+		b.fill--
+		return result
+	}
+
+	//do we have a full ANSI escape sequence?
+	match := ansiEscapeRx.Find(b.buf[0:b.fill])
+	if match != nil {
+		result := append([]byte(nil), match...)
+		copy(b.buf[0:], b.buf[len(match):])
+		b.fill -= len(match)
+		return result
+	}
+
+	oldState, err := terminal.MakeRaw(0)
+	if err != nil {
+		panic(err)
+	}
+	defer terminal.Restore(0, oldState)
+
+	//fill buffer some more
+	n, err := b.Input.Read(b.buf[b.fill:])
+	if err != nil {
+		panic(err)
+	}
+	b.fill += n
+
+	return b.getNextInput() //restart
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// TUI implementation for when stdin is a pipe (also used in unit tests)
+
+type pipeTUI struct {
+	i *Implementation
+}
+
+//AnsiColorCodeRx is a regexp that matches ANSI escape sequences of the type SGR.
+var AnsiColorCodeRx = regexp.MustCompile("\x1B" + `\[[0-9;]*m`)
+
+func (t *pipeTUI) Print(w io.Writer, msg string) {
+	w.Write([]byte(AnsiColorCodeRx.ReplaceAllString(msg, "")))
+}
+
+func (t *pipeTUI) ReadLine(prompt string) (string, error) {
+	str, err := t.i.stdinBuf.ReadString('\n')
+	str = strings.TrimSpace(str)
+	if err == nil {
+		fmt.Fprintf(t.i.stderr, "%s %s\n", strings.TrimSpace(prompt), str)
+	}
+	return str, err
+}
+
+func (t *pipeTUI) Confirm(question string) (bool, error) {
+	question = strings.TrimSpace(question)
+	str, err := t.ReadLine(question)
+	if err != nil {
+		return false, err
+	}
+	//recognize /[01tTfF]|true|false/
+	ok, err := strconv.ParseBool(str)
+	if err != nil {
+		//recognize /[yY]|yes|no/
+		ok = strings.HasPrefix(question, "y") || strings.HasPrefix(question, "Y")
+	}
+	fmt.Fprintf(t.i.stderr, "%s -> %v (%s)\n", question, ok, str)
+	return ok, nil
+}
+
+//Query for the pipe TUI is limited to exact matches of the choice text, or
+//matching by choice shortcut.
+func (t *pipeTUI) Query(prompt string, choices ...Choice) (string, error) {
+	str, err := t.i.stdinBuf.ReadString('\n')
+	if err != nil {
+		return str, err
+	}
+	str = strings.TrimSpace(str)
+
+	//prefer exact match on choice.Text
+	for _, choice := range choices {
+		if choice.Text == str {
+			fmt.Fprintf(t.i.stderr, "%s -> %s\n", prompt, choice.Text)
+			return choice.Return, nil
+		}
+	}
+	//allow match on choice.Shortcut
+	for _, choice := range choices {
+		if string(choice.Shortcut) == str {
+			fmt.Fprintf(t.i.stderr, "%s -> %s\n", prompt, choice.Text)
+			return choice.Return, nil
+		}
+	}
+	fmt.Fprintf(t.i.stderr, "%s -> [%s]\n", prompt, str)
+	return "", errors.New("cannot match input with available choices")
+}