diff options
Diffstat (limited to 'pkg/cli/query.go')
| -rw-r--r-- | pkg/cli/query.go | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/pkg/cli/query.go b/pkg/cli/query.go new file mode 100644 index 0000000..a81d153 --- /dev/null +++ b/pkg/cli/query.go @@ -0,0 +1,186 @@ +/******************************************************************************* +* +* 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 ( + "fmt" + "io" + "os" + "regexp" + "strings" + + terminal "golang.org/x/crypto/ssh/terminal" +) + +//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 +} + +func (c Choice) hasShortcut() bool { + return c.Shortcut != '\000' +} + +//Query displays a question and a set of answers and allows the user to select +//one of the answers. Returns the selected Choice instance, as well as its +//index in the original choices list (starting from 0). +func Query(prompt string, choices ...Choice) (Choice, int) { + if len(choices) == 0 { + return Choice{}, -1 + } + + //disable line wrap during doQuery(); unexpected wrapping would confuse our + //cursor-moving code + os.Stdout.Write([]byte("\x1B[?7l")) + defer os.Stdout.Write([]byte("\x1B[?7h")) + + //display question + os.Stdout.Write([]byte(strings.TrimSuffix(prompt, "\n") + "\n")) + selected := 0 + + buf := buffer{Input: os.Stdin} +OUTER: + for { + displayChoices(os.Stdout, 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 + fmt.Fprintf(os.Stderr, "Interrupted!") + os.Exit(255) + default: + fmt.Printf("%#v\n", string(input)) + } + + //prepare to re-render choices + removeDisplayLines(len(choices)) + } + + //clear query display + removeDisplayLines(len(choices) + 1) + + //display question + chosen answer + fmt.Fprintf(os.Stdout, "%s -> %s\n", + strings.TrimSuffix(prompt, "\n"), + strings.TrimSpace(choices[selected].Text), + ) + + return choices[selected], selected +} + +func removeDisplayLines(n int) { + for idx := 0; idx < n; idx++ { + os.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 { + out.Write(Styled(text, AnsiInverse).DisplayString(true)) + } 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 := os.Stdin.Read(b.buf[b.fill:]) + if err != nil { + panic(err) + } + b.fill += n + + return b.getNextInput() //restart +} |