Began implementing the befunge field data structure

pkg/field/error.go

@@ -0,0 +1,34 @@
+package field
+
+import "fmt"
+
+// Read error
+type ReadError struct {
+	err error
+}
+
+func (e ReadError) Error() string {
+	return fmt.Sprintf("Failed to decode file")
+}
+func (e ReadError) Unwrap() error { return e.err }
+
+func newReadError(err error) error {
+	return &ReadError{
+		err: err,
+	}
+}
+
+// Funge decoding error
+type DecodeError struct {
+	msg string
+}
+
+func (e DecodeError) Error() string {
+	return fmt.Sprintf("Failed to decode file with message : %s", e.msg)
+}
+
+func newDecodeError(msg string) error {
+	return &DecodeError{
+		msg: msg,
+	}
+}

pkg/field/error_test.go

@@ -0,0 +1,20 @@
+package field
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func requireErrorTypeMatch(t *testing.T, err error, expected error) {
+	require.Equalf(t, reflect.TypeOf(err), reflect.TypeOf(expected), "Invalid error type. Got %s but expected %s", reflect.TypeOf(err), reflect.TypeOf(expected))
+}
+
+func TestErrorsCoverage(t *testing.T) {
+	readErr := ReadError{}
+	_ = readErr.Error()
+	_ = readErr.Unwrap()
+	decodeError := DecodeError{}
+	_ = decodeError.Error()
+}

pkg/field/field.go

@@ -0,0 +1,81 @@
+package field
+
+import (
+	"bytes"
+	"io"
+)
+
+//            32-bit Befunge-98
+//           =================
+//                   |-2,147,483,648
+//                   |
+//                   |    x
+//              -----+-----
+// -2,147,483,648    |    2,147,483,647
+//                   |
+//                  y|2,147,483,647
+
+type Field struct {
+	firstLineIndex int
+	length         int
+	lines          []Line
+}
+
+type Line struct {
+	firstColumnIndex int
+	length           int
+	columns          []byte
+}
+
+func LoadFile(fd io.Reader) (*Field, error) {
+	f := new(Field)
+	l := new(Line)
+	trailingSpaces := 0
+	for {
+		data := make([]byte, 4096)
+		if n, errRead := fd.Read(data); errRead != nil {
+			if errRead == io.EOF {
+				if f.length == 0 && l.length == 0 {
+					return nil, newDecodeError("No instruction on the first line of the file produces an unusable program in Befunge98")
+				}
+				if l.length > 0 {
+					f.length++
+					f.lines = append(f.lines, *l)
+				}
+				break
+			} else {
+				return nil, newReadError(errRead)
+			}
+		} else {
+			for i := 0; i < n; i++ {
+				if data[i] == '\n' || data[i] == '\r' {
+					if f.length == 0 && l.length == 0 {
+						return nil, newDecodeError("No instruction on the first line of the file produces an unusable program in Befunge98")
+					}
+					f.length++
+					f.lines = append(f.lines, *l)
+					l = new(Line)
+					trailingSpaces = 0
+					if i+1 < n && data[i] == '\r' && data[i+1] == '\n' {
+						i++
+					}
+				} else {
+					if l.length == 0 && data[i] == ' ' {
+						l.firstColumnIndex++ // trim leading spaces
+					} else {
+						if data[i] == ' ' {
+							trailingSpaces++
+						} else {
+							l.columns = append(l.columns, bytes.Repeat([]byte{' '}, trailingSpaces)...)
+							l.length += trailingSpaces
+							trailingSpaces = 0
+							l.length++
+							l.columns = append(l.columns, data[i])
+						}
+					}
+				}
+			}
+		}
+	}
+	return f, nil
+}

pkg/field/field_test.go

@@ -0,0 +1,154 @@
+package field
+
+import (
+	"io"
+	"os"
+	"testing"
+	"testing/iotest"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestLoadFile(t *testing.T) {
+	// minimal b98 file
+	minimalField := Field{
+		firstLineIndex: 0,
+		length:         1,
+		lines: []Line{
+			Line{
+				firstColumnIndex: 0,
+				length:           1,
+				columns:          []byte{'@'},
+			},
+		},
+	}
+	// hello b98 file
+	helloField := Field{
+		firstLineIndex: 0,
+		length:         1,
+		lines: []Line{
+			Line{
+				firstColumnIndex: 0,
+				length:           24,
+				columns:          []byte{'6', '4', '+', '"', '!', 'd', 'l', 'r', 'o', 'W', ' ', ',', 'o', 'l', 'l', 'e', 'H', '"', '>', ':', '#', ',', '_', '@'},
+			},
+		},
+	}
+	// factorial b98 file
+	factorialField := Field{
+		firstLineIndex: 0,
+		length:         2,
+		lines: []Line{
+			Line{
+				firstColumnIndex: 0,
+				length:           15,
+				columns:          []byte{'&', '>', ':', '1', '-', ':', 'v', ' ', 'v', ' ', '*', '_', '$', '.', '@'},
+			},
+			Line{
+				firstColumnIndex: 1,
+				length:           11,
+				columns:          []byte{'^', ' ', ' ', ' ', ' ', '_', '$', '>', '\\', ':', '^'},
+			},
+		},
+	}
+	// dna b98 file
+	dnaField := Field{
+		firstLineIndex: 0,
+		length:         8,
+		lines: []Line{
+			Line{
+				firstColumnIndex: 0,
+				length:           7,
+				columns:          []byte{'7', '^', 'D', 'N', '>', 'v', 'A'},
+			},
+			Line{
+				firstColumnIndex: 0,
+				length:           7,
+				columns:          []byte{'v', '_', '#', 'v', '?', ' ', 'v'},
+			},
+			Line{
+				firstColumnIndex: 0,
+				length:           7,
+				columns:          []byte{'7', '^', '<', '"', '"', '"', '"'},
+			},
+			Line{
+				firstColumnIndex: 0,
+				length:           7,
+				columns:          []byte{'3', ' ', ' ', 'A', 'C', 'G', 'T'},
+			},
+			Line{
+				firstColumnIndex: 0,
+				length:           7,
+				columns:          []byte{'9', '0', '!', '"', '"', '"', '"'},
+			},
+			Line{
+				firstColumnIndex: 0,
+				length:           7,
+				columns:          []byte{'4', '*', ':', '>', '>', '>', 'v'},
+			},
+			Line{
+				firstColumnIndex: 0,
+				length:           7,
+				columns:          []byte{'+', '8', '^', '-', '1', ',', '<'},
+			},
+			Line{
+				firstColumnIndex: 0,
+				length:           7,
+				columns:          []byte{'>', ' ', ',', '+', ',', '@', ')'},
+			},
+		},
+	}
+	// \r\n file b98 file
+	rnField := Field{
+		firstLineIndex: 0,
+		length:         1,
+		lines: []Line{
+			Line{
+				firstColumnIndex: 0,
+				length:           24,
+				columns:          []byte{'6', '4', '+', '"', '!', 'd', 'l', 'r', 'o', 'W', ' ', ',', 'o', 'l', 'l', 'e', 'H', '"', '>', ':', '#', ',', '_', '@'},
+			},
+		},
+	}
+	// Test cases
+	type addError func(r io.Reader) io.Reader
+	testCases := []struct {
+		name          string
+		input         string
+		inputAddError addError
+		expected      *Field
+		expectedError error
+	}{
+		{"Empty file", "test_data/empty.b98", nil, nil, &DecodeError{}},
+		{"Invalid file content", "test_data/invalid.b98", nil, nil, &DecodeError{}},
+		{"io error", "test_data/minimal.b98", iotest.TimeoutReader, nil, &ReadError{}},
+		{"minimal", "test_data/minimal.b98", nil, &minimalField, nil},
+		{"hello", "test_data/hello.b98", nil, &helloField, nil},
+		{"factorial", "test_data/factorial.b98", nil, &factorialField, nil},
+		{"dna", "test_data/dna.b98", nil, &dnaField, nil},
+		{"\\r\\n file", "test_data/rn.b98", nil, &rnField, nil},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			var fd io.Reader
+			file, err := os.Open(tc.input)
+			require.NoError(t, err, "Failed to open file")
+			defer file.Close()
+			if tc.inputAddError != nil {
+				fd = tc.inputAddError(file)
+			} else {
+				fd = file
+			}
+			valid, err := LoadFile(fd)
+			if tc.expectedError != nil {
+				require.Error(t, err)
+				requireErrorTypeMatch(t, err, tc.expectedError)
+				require.Nil(t, valid)
+			} else {
+				require.NoError(t, err)
+			}
+			assert.Equal(t, tc.expected, valid, "Invalid value")
+		})
+	}
+}

pkg/field/test_data/dna.b98

@@ -0,0 +1,8 @@
+7^DN>vA
+v_#v? v
+7^<""""
+3  ACGT  
+90!""""
+4*:>>>v
++8^-1,<
+> ,+,@)  

pkg/field/test_data/factorial.b98

@@ -0,0 +1,2 @@
+&>:1-:v v *_$.@  
+ ^    _$>\:^ 

pkg/field/test_data/hello.b98

@@ -0,0 +1 @@
+64+"!dlroW ,olleH">:#,_@

pkg/field/test_data/invalid.b98

@@ -0,0 +1,2 @@
+
+@

pkg/field/test_data/minimal.b98

@@ -0,0 +1 @@
+@

pkg/field/test_data/rn.b98

@@ -0,0 +1 @@
+64+"!dlroW ,olleH">:#,_@