fixed GetTOTP, started rough QR code implementation

GetTOTP handles TOTP method retrieval for confirmation and deletion.

QR code implementation looks like it's gonna suck, so might end up
using a library for this later.

controller/qr.go

@@ -0,0 +1,107 @@
+package controller
+
+import (
+	"bytes"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"image"
+	"image/color"
+	"image/png"
+)
+
+const margin = 4
+
+type QRCodeECCLevel int64
+const (
+    LOW QRCodeECCLevel = iota
+    MEDIUM
+    QUARTILE
+    HIGH
+)
+
+func GenerateQRCode(data []byte) (string, error) {
+    version := 1
+
+    size := 0
+    size = 21 + version * 4
+    if version > 10 {
+        return "", errors.New(fmt.Sprintf("QR version %d not supported", version))
+    }
+
+    img := image.NewGray(image.Rect(0, 0, size + margin * 2, size + margin * 2))
+
+    // fill white
+    for y := range size + margin * 2 {
+        for x := range size + margin * 2 {
+            img.Set(x, y, color.White)
+        }
+    }
+
+    // draw alignment squares
+    drawLargeAlignmentSquare(margin, margin, img)
+    drawLargeAlignmentSquare(margin, margin + size - 7, img)
+    drawLargeAlignmentSquare(margin + size - 7, margin, img)
+    drawSmallAlignmentSquare(size - 5, size - 5, img)
+    /*
+    if version > 4 {
+        space := version * 3 - 2
+        end := size / space
+        for y := range size / space + 1 {
+            for x := range size / space + 1 {
+                if x == 0 && y == 0 { continue }
+                if x == 0 && y == end { continue }
+                if x == end && y == 0 { continue }
+                if x == end && y == end { continue }
+                drawSmallAlignmentSquare(
+                    x * space + margin + 4,
+                    y * space + margin + 4,
+                    img,
+                )
+            }
+        }
+    }
+    */
+
+    // draw timing bits
+    for i := margin + 6; i < size - 4; i++ {
+        if (i % 2 == 0) {
+            img.Set(i, margin + 6, color.Black)
+            img.Set(margin + 6, i, color.Black)
+        }
+    }
+    img.Set(margin + 8, size - 4, color.Black)
+
+    var imgBuf bytes.Buffer
+    err := png.Encode(&imgBuf, img)
+    if err != nil {
+        return "", err
+    }
+
+    base64Img := base64.StdEncoding.EncodeToString(imgBuf.Bytes())
+
+    return "data:image/png;base64," + base64Img, nil
+}
+
+func drawLargeAlignmentSquare(x int, y int, img *image.Gray) {
+    for yi := range 7 {
+        for xi := range 7 {
+            if (xi == 0 || xi == 6) || (yi == 0 || yi == 6) {
+                img.Set(x + xi, y + yi, color.Black)
+            } else if (xi > 1 && xi < 5) && (yi > 1 && yi < 5) {
+                img.Set(x + xi, y + yi, color.Black)
+            }
+        }
+    }
+}
+
+func drawSmallAlignmentSquare(x int, y int, img *image.Gray) {
+    for yi := range 5 {
+        for xi := range 5 {
+            if (xi == 0 || xi == 4) || (yi == 0 || yi == 4) {
+                img.Set(x + xi, y + yi, color.Black)
+            }
+        }
+    }
+    img.Set(x + 2, y + 2, color.Black)
+}