rewrite checkpoint

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

@@ -0,0 +1,134 @@
+// +build !windows
+
+package terminal
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// CursorUp moves the cursor n cells to up.
+func CursorUp(n int) {
+	fmt.Printf("\x1b[%dA", n)
+}
+
+// CursorDown moves the cursor n cells to down.
+func CursorDown(n int) {
+	fmt.Printf("\x1b[%dB", n)
+}
+
+// CursorForward moves the cursor n cells to right.
+func CursorForward(n int) {
+	fmt.Printf("\x1b[%dC", n)
+}
+
+// CursorBack moves the cursor n cells to left.
+func CursorBack(n int) {
+	fmt.Printf("\x1b[%dD", n)
+}
+
+// CursorNextLine moves cursor to beginning of the line n lines down.
+func CursorNextLine(n int) {
+	fmt.Printf("\x1b[%dE", n)
+}
+
+// CursorPreviousLine moves cursor to beginning of the line n lines up.
+func CursorPreviousLine(n int) {
+	fmt.Printf("\x1b[%dF", n)
+}
+
+// CursorHorizontalAbsolute moves cursor horizontally to x.
+func CursorHorizontalAbsolute(x int) {
+	fmt.Printf("\x1b[%dG", x)
+}
+
+// CursorShow shows the cursor.
+func CursorShow() {
+	fmt.Print("\x1b[?25h")
+}
+
+// CursorHide hide the cursor.
+func CursorHide() {
+	fmt.Print("\x1b[?25l")
+}
+
+// CursorMove moves the cursor to a specific x,y location.
+func CursorMove(x int, y int) {
+	fmt.Printf("\x1b[%d;%df", x, y)
+}
+
+// CursorLocation returns the current location of the cursor in the terminal
+func CursorLocation() (*Coord, error) {
+	// print the escape sequence to recieve the position in our stdin
+	fmt.Print("\x1b[6n")
+
+	// read from stdin to get the response
+	reader := bufio.NewReader(os.Stdin)
+	// spec says we read 'til R, so do that
+	text, err := reader.ReadSlice('R')
+	if err != nil {
+		return nil, err
+	}
+
+	// spec also says they're split by ;, so do that too
+	if strings.Contains(string(text), ";") {
+		// a regex to parse the output of the ansi code
+		re := regexp.MustCompile(`\d+;\d+`)
+		line := re.FindString(string(text))
+
+		// find the column and rows embedded in the string
+		coords := strings.Split(line, ";")
+
+		// try to cast the col number to an int
+		col, err := strconv.Atoi(coords[1])
+		if err != nil {
+			return nil, err
+		}
+
+		// try to cast the row number to an int
+		row, err := strconv.Atoi(coords[0])
+		if err != nil {
+			return nil, err
+		}
+
+		// return the coordinate object with the col and row we calculated
+		return &Coord{Short(col), Short(row)}, nil
+	}
+
+	// it didn't work so return an error
+	return nil, fmt.Errorf("could not compute the cursor position using ascii escape sequences")
+}
+
+// Size returns the height and width of the terminal.
+func Size() (*Coord, error) {
+	// the general approach here is to move the cursor to the very bottom
+	// of the terminal, ask for the current location and then move the
+	// cursor back where we started
+
+	// save the current location of the cursor
+	origin, err := CursorLocation()
+	if err != nil {
+		return nil, err
+	}
+
+	// move the cursor to the very bottom of the terminal
+	CursorMove(999, 999)
+
+	// ask for the current location
+	bottom, err := CursorLocation()
+	if err != nil {
+		return nil, err
+	}
+
+	// move back where we began
+	CursorUp(int(bottom.Y - origin.Y))
+	CursorHorizontalAbsolute(int(origin.X))
+
+	// sice the bottom was calcuated in the lower right corner, it
+	// is the dimensions we are looking for
+	return bottom, nil
+}