rewrite checkpoint

vendor/github.com/AlecAivazis/survey/terminal/runereader.go

@@ -0,0 +1,184 @@
+package terminal
+
+import (
+	"fmt"
+	"os"
+	"unicode"
+)
+
+type RuneReader struct {
+	Input *os.File
+
+	state runeReaderState
+}
+
+func NewRuneReader(input *os.File) *RuneReader {
+	return &RuneReader{
+		Input: input,
+		state: newRuneReaderState(input),
+	}
+}
+
+func (rr *RuneReader) ReadLine(mask rune) ([]rune, error) {
+	line := []rune{}
+
+	// we only care about horizontal displacements from the origin so start counting at 0
+	index := 0
+
+	for {
+		// wait for some input
+		r, _, err := rr.ReadRune()
+		if err != nil {
+			return line, err
+		}
+
+		// if the user pressed enter or some other newline/termination like ctrl+d
+		if r == '\r' || r == '\n' || r == KeyEndTransmission {
+			// go to the beginning of the next line
+			Print("\r\n")
+
+			// we're done processing the input
+			return line, nil
+		}
+
+		// if the user interrupts (ie with ctrl+c)
+		if r == KeyInterrupt {
+			// go to the beginning of the next line
+			Print("\r\n")
+
+			// we're done processing the input, and treat interrupt like an error
+			return line, fmt.Errorf("interrupt")
+		}
+
+		// allow for backspace/delete editing of inputs
+		if r == KeyBackspace || r == KeyDelete {
+			// and we're not at the beginning of the line
+			if index > 0 && len(line) > 0 {
+				// if we are at the end of the word
+				if index == len(line) {
+					// just remove the last letter from the internal representation
+					line = line[:len(line)-1]
+
+					// go back one
+					CursorBack(1)
+
+					// clear the rest of the line
+					EraseLine(ERASE_LINE_END)
+				} else {
+					// we need to remove a character from the middle of the word
+
+					// remove the current index from the list
+					line = append(line[:index-1], line[index:]...)
+
+					// go back one space so we can clear the rest
+					CursorBack(1)
+
+					// clear the rest of the line
+					EraseLine(ERASE_LINE_END)
+
+					// print what comes after
+					Print(string(line[index-1:]))
+
+					// leave the cursor where the user left it
+					CursorBack(len(line) - index + 1)
+				}
+
+				// decrement the index
+				index--
+			} else {
+				// otherwise the user pressed backspace while at the beginning of the line
+				soundBell()
+			}
+
+			// we're done processing this key
+			continue
+		}
+
+		// if the left arrow is pressed
+		if r == KeyArrowLeft {
+			// and we have space to the left
+			if index > 0 {
+				// move the cursor to the left
+				CursorBack(1)
+				// decrement the index
+				index--
+
+			} else {
+				// otherwise we are at the beginning of where we started reading lines
+				// sound the bell
+				soundBell()
+			}
+
+			// we're done processing this key press
+			continue
+		}
+
+		// if the right arrow is pressed
+		if r == KeyArrowRight {
+			// and we have space to the right of the word
+			if index < len(line) {
+				// move the cursor to the right
+				CursorForward(1)
+				// increment the index
+				index++
+
+			} else {
+				// otherwise we are at the end of the word and can't go past
+				// sound the bell
+				soundBell()
+			}
+
+			// we're done processing this key press
+			continue
+		}
+
+		// if the letter is another escape sequence
+		if unicode.IsControl(r) {
+			// ignore it
+			continue
+		}
+
+		// the user pressed a regular key
+
+		// if we are at the end of the line
+		if index == len(line) {
+			// just append the character at the end of the line
+			line = append(line, r)
+			// increment the location counter
+			index++
+
+			// if we don't need to mask the input
+			if mask == 0 {
+				// just print the character the user pressed
+				Printf("%c", r)
+			} else {
+				// otherwise print the mask we were given
+				Printf("%c", mask)
+			}
+		} else {
+			// we are in the middle of the word so we need to insert the character the user pressed
+			line = append(line[:index], append([]rune{r}, line[index:]...)...)
+
+			// visually insert the character by deleting the rest of the line
+			EraseLine(ERASE_LINE_END)
+
+			// print the rest of the word after
+			for _, char := range line[index:] {
+				// if we don't need to mask the input
+				if mask == 0 {
+					// just print the character the user pressed
+					Printf("%c", char)
+				} else {
+					// otherwise print the mask we were given
+					Printf("%c", mask)
+				}
+			}
+
+			// leave the cursor where the user left it
+			CursorBack(len(line) - index - 1)
+
+			// accomodate the new letter in our counter
+			index++
+		}
+	}
+}