Fixes some mycology test suite errors

pkg/field/blank.go

@@ -0,0 +1,97 @@
+package field
+
+func (f *Field) Blank(x, y int) {
+	if !f.isIn(x, y) {
+		// outside the field, nothing to do
+		return
+	}
+	l := &f.lines[y-f.y]
+	if x < l.x || x >= l.x+l.l {
+		// outside the current line's columns
+		return
+	}
+	if x > l.x && x < l.x+l.l-1 {
+		// just set the value
+		l.columns[x-l.x] = ' '
+		return
+	}
+	// do we need to trim this line?
+	if l.l == 1 {
+		// this was the last character on the line
+		if y == f.y {
+			// We need to trim the leading lines
+			leadingLines := 1
+			for i := 1; i < f.ly; i++ {
+				if f.lines[i].l == 0 {
+					leadingLines++
+				} else {
+					break
+				}
+			}
+			f.y += leadingLines
+			f.ly -= leadingLines
+			lines := make([]Line, f.ly)
+			for i := 0; i < f.ly; i++ {
+				lines[i] = f.lines[leadingLines+i]
+			}
+			f.lines = lines
+		} else if y == f.y+f.ly-1 {
+			// We need to trim the trailing lines
+			trailingLines := 1
+			for i := f.ly + f.y - 2; i >= 0; i-- {
+				if f.lines[i].l == 0 {
+					trailingLines++
+				} else {
+					break
+				}
+			}
+			f.ly -= trailingLines
+			f.lines = f.lines[:f.ly]
+		} else {
+			// it was a line in the middle
+			l.l = 0
+			l.columns = make([]int, 0)
+		}
+	} else if x == l.x {
+		// We need to remove leading spaces
+		leadingSpaces := 1
+		for i := 1; i < l.l; i++ {
+			if l.columns[i] == ' ' {
+				leadingSpaces++
+			} else {
+				break
+			}
+		}
+		l.x += leadingSpaces
+		l.l -= leadingSpaces
+		columns := make([]int, l.l)
+		for i := 0; i < l.l; i++ {
+			columns[i] = l.columns[leadingSpaces+i]
+		}
+		l.columns = columns
+	} else if x == l.l+l.x-1 {
+		// we need to remove trailing spaces
+		trailingSpaces := 1
+		for i := l.l - 2; i >= 0; i-- {
+			if l.columns[i] == ' ' {
+				trailingSpaces++
+			} else {
+				break
+			}
+		}
+		l.l -= trailingSpaces
+		l.columns = l.columns[:l.l]
+	}
+	// we now need to find the new field limits
+	f.x = f.lines[0].x
+	x2 := f.lines[0].l + f.lines[0].x
+	for i := 1; i < f.ly; i++ {
+		if f.x > f.lines[i].x {
+			f.x = f.lines[i].x
+		}
+		if x2 < f.lines[i].x+f.lines[i].l {
+			x2 = f.lines[i].x + f.lines[i].l
+		}
+	}
+	f.lx = x2 - f.x
+}