Fix -startpos flag being ignored (#1129)

* Refactored cursor location login into a function. Fixed buffer overflow when line position is 1 more than file lines

* Fixed crash when -startpos has an invalid argument

* Adapted tests to new interface

* Fixed bug where -startpos with lines 0 and 1 would both be on the first line

* Changed Fatalf format back to digits

* Fixed issues with buffer cursor location. Added tests for new function

* ParseCursorLocation will now return an error when path doesnt contain line/col

* Fixed off-by-one line error

* Fixed tests to account for subtracting 1 from the line index

cmd/micro/buffer_test.go

@@ -0,0 +1,117 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestGetBufferCursorLocationEmptyArgs(t *testing.T) {
+	buf := NewBufferFromString("this is my\nbuffer\nfile\nhello", "")
+
+	location, err := GetBufferCursorLocation(nil, buf)
+
+	assertEqual(t, 0, location.Y)
+	assertEqual(t, 0, location.X)
+
+	// an error is present due to the cursorLocation being nil
+	assertTrue(t, err != nil)
+
+}
+
+func TestGetBufferCursorLocationStartposFlag(t *testing.T) {
+	buf := NewBufferFromString("this is my\nbuffer\nfile\nhello", "")
+
+	*flagStartPos = "1,2"
+
+	location, err := GetBufferCursorLocation(nil, buf)
+
+	// note: 1 is subtracted from the line to get the correct index in the buffer
+	assertTrue(t, 0 == location.Y)
+	assertTrue(t, 2 == location.X)
+
+	// an error is present due to the cursorLocation being nil
+	assertTrue(t, err != nil)
+}
+
+func TestGetBufferCursorLocationInvalidStartposFlag(t *testing.T) {
+	buf := NewBufferFromString("this is my\nbuffer\nfile\nhello", "")
+
+	*flagStartPos = "apples,2"
+
+	location, err := GetBufferCursorLocation(nil, buf)
+	// expect to default to the start of the file, which is 0,0
+	assertEqual(t, 0, location.Y)
+	assertEqual(t, 0, location.X)
+
+	// an error is present due to the cursorLocation being nil
+	assertTrue(t, err != nil)
+}
+func TestGetBufferCursorLocationStartposFlagAndCursorPosition(t *testing.T) {
+	text := "this is my\nbuffer\nfile\nhello"
+	cursorPosition := []string{"3", "1"}
+
+	buf := NewBufferFromString(text, "")
+
+	*flagStartPos = "1,2"
+
+	location, err := GetBufferCursorLocation(cursorPosition, buf)
+	// expect to have the flag positions, not the cursor position
+	// note: 1 is subtracted from the line to get the correct index in the buffer
+	assertEqual(t, 0, location.Y)
+	assertEqual(t, 2, location.X)
+
+	assertTrue(t, err == nil)
+}
+func TestGetBufferCursorLocationCursorPositionAndInvalidStartposFlag(t *testing.T) {
+	text := "this is my\nbuffer\nfile\nhello"
+	cursorPosition := []string{"3", "1"}
+
+	buf := NewBufferFromString(text, "")
+
+	*flagStartPos = "apples,2"
+
+	location, err := GetBufferCursorLocation(cursorPosition, buf)
+	// expect to have the flag positions, not the cursor position
+	// note: 1 is subtracted from the line to get the correct index in the buffer
+	assertEqual(t, 2, location.Y)
+	assertEqual(t, 1, location.X)
+
+	// no errors this time as cursorPosition is not nil
+	assertTrue(t, err == nil)
+}
+
+func TestGetBufferCursorLocationNoErrorWhenOverflowWithStartpos(t *testing.T) {
+	text := "this is my\nbuffer\nfile\nhello"
+
+	buf := NewBufferFromString(text, "")
+
+	*flagStartPos = "50,50"
+
+	location, err := GetBufferCursorLocation(nil, buf)
+	// expect to have the flag positions, not the cursor position
+	assertEqual(t, buf.NumLines-1, location.Y)
+	assertEqual(t, 5, location.X)
+
+	// error is expected as cursorPosition is nil
+	assertTrue(t, err != nil)
+}
+func TestGetBufferCursorLocationNoErrorWhenOverflowWithCursorPosition(t *testing.T) {
+	text := "this is my\nbuffer\nfile\nhello"
+	cursorPosition := []string{"50", "2"}
+
+	*flagStartPos = ""
+
+	buf := NewBufferFromString(text, "")
+
+	location, err := GetBufferCursorLocation(cursorPosition, buf)
+	// expect to have the flag positions, not the cursor position
+	assertEqual(t, buf.NumLines-1, location.Y)
+	assertEqual(t, 2, location.X)
+
+	// error is expected as cursorPosition is nil
+	assertTrue(t, err == nil)
+}
+
+//func TestGetBufferCursorLocationColonArgs(t *testing.T) {
+//	buf := new(Buffer)
+
+//}