Implement JSON marshalling for the matrix class

matrix/matrix.go

@@ -4,6 +4,7 @@
 package matrix
 
 import (
+	"encoding/json"
 	"errors"
 
 	"golang.org/x/exp/constraints"
@@ -107,6 +108,17 @@ func CreateFromFlatSlice[T Number](rows, cols int, values []T) *Matrix[T] {
 	return m
 }
 
+// CreateFromJSON creates a new matrix from JSON data representing a
+// two-dimensional array. Returns an error if the JSON is invalid, the array is
+// empty, or the inner arrays have inconsistent lengths.
+func CreateFromJSON[T Number](data []byte) (*Matrix[T], error) {
+	m := &Matrix[T]{}
+	if err := m.UnmarshalJSON(data); err != nil {
+		return nil, err
+	}
+	return m, nil
+}
+
 // Convert will take a matrix of type T and convert it into a matrix of type U
 // Only works on SimpleNumber matrices
 func Convert[U, T SimpleNumber](in *Matrix[T]) *Matrix[U] {
@@ -320,3 +332,39 @@ func (m *Matrix[T]) Fill(value T) *Matrix[T] {
 	}
 	return m
 }
+
+// UnmarshalJSON implements json.Unmarshaler for Matrix, creating a matrix from
+// a JSON two-dimensional array.
+func (m *Matrix[T]) UnmarshalJSON(data []byte) error {
+	var values [][]T
+	if err := json.Unmarshal(data, &values); err != nil {
+		return err
+	}
+
+	rows := len(values)
+	if rows == 0 {
+		return ErrInvalidDimensions
+	}
+	cols := len(values[0])
+	if cols == 0 {
+		return ErrInvalidDimensions
+	}
+
+	for i := range rows {
+		if len(values[i]) != cols {
+			return ErrIncompatibleDataDimensions
+		}
+	}
+
+	m.rows = rows
+	m.cols = cols
+	m.values = values
+
+	return nil
+}
+
+// MarshalJSON implements json.Marshaler for Matrix, serializing the matrix as
+// a JSON two-dimensional array.
+func (m *Matrix[T]) MarshalJSON() ([]byte, error) {
+	return json.Marshal(m.values)
+}

matrix/matrix_test.go

@@ -1,6 +1,7 @@
 package matrix_test
 
 import (
+	"encoding/json"
 	"testing"
 
 	"git.omicron.one/playground/cryptography/matrix"
@@ -129,6 +130,46 @@ func TestCreateFromFlatSlice(t *testing.T) {
 	})
 }
 
+func TestCreateFromJSON(t *testing.T) {
+	// data json
+	data := []byte(`[[1, 2, 3], [4, 5, 6]]`)
+	m, err := matrix.CreateFromJSON[int](data)
+	assert.Nil(t, err)
+	assert.NotNil(t, m)
+	assert.Equal(t, 2, m.Rows())
+	assert.Equal(t, 3, m.Cols())
+	assert.Equal(t, 1, m.Get(0, 0))
+	assert.Equal(t, 2, m.Get(0, 1))
+	assert.Equal(t, 3, m.Get(0, 2))
+	assert.Equal(t, 4, m.Get(1, 0))
+	assert.Equal(t, 5, m.Get(1, 1))
+	assert.Equal(t, 6, m.Get(1, 2))
+
+	// invalid json
+	data = []byte(`[[1, 2, 3], [4, 5,`)
+	m, err = matrix.CreateFromJSON[int](data)
+	assert.NotNil(t, err)
+	assert.Nil(t, m)
+
+	// empty matrix
+	data = []byte(`[]`)
+	m, err = matrix.CreateFromJSON[int](data)
+	assert.ErrorIs(t, err, matrix.ErrInvalidDimensions)
+	assert.Nil(t, m)
+
+	// empty rows
+	data = []byte(`[[]]`)
+	m, err = matrix.CreateFromJSON[int](data)
+	assert.ErrorIs(t, err, matrix.ErrInvalidDimensions)
+	assert.Nil(t, m)
+
+	// mixed row length
+	data = []byte(`[[1, 2, 3], [4, 5]]`)
+	m, err = matrix.CreateFromJSON[int](data)
+	assert.ErrorIs(t, err, matrix.ErrIncompatibleDataDimensions)
+	assert.Nil(t, m)
+}
+
 func TestSum(t *testing.T) {
 	a := matrix.CreateFromFlatSlice(2, 3, []int{1, 2, 3, 4, 5, 6})
 	b := matrix.CreateFromFlatSlice(2, 3, []int{1, 1, 1, 1, 1, 1})
@@ -528,3 +569,87 @@ func TestMatrix_Fill(t *testing.T) {
 	assert.Equal(t, 3, a.Get(1, 1))
 	assert.Equal(t, 3, a.Get(1, 2))
 }
+
+func TestMatrix_UnmarshalJSON(t *testing.T) {
+	// int matrix
+	data := []byte(`[[1,2,3],[4,5,6]]`)
+	var m *matrix.Matrix[int]
+	err := json.Unmarshal(data, &m)
+	assert.Nil(t, err)
+
+	assert.Equal(t, 2, m.Rows())
+	assert.Equal(t, 3, m.Cols())
+	assert.Equal(t, 1, m.Get(0, 0))
+	assert.Equal(t, 2, m.Get(0, 1))
+	assert.Equal(t, 3, m.Get(0, 2))
+	assert.Equal(t, 4, m.Get(1, 0))
+	assert.Equal(t, 5, m.Get(1, 1))
+	assert.Equal(t, 6, m.Get(1, 2))
+
+	// float matrix
+	data = []byte(`[[1.5,2.5],[3.5,4.5]]`)
+	var mf *matrix.Matrix[float64]
+	err = json.Unmarshal(data, &mf)
+	assert.Nil(t, err)
+
+	assert.Equal(t, 2, mf.Rows())
+	assert.Equal(t, 2, mf.Cols())
+	assert.Equal(t, 1.5, mf.Get(0, 0))
+	assert.Equal(t, 2.5, mf.Get(0, 1))
+	assert.Equal(t, 3.5, mf.Get(1, 0))
+	assert.Equal(t, 4.5, mf.Get(1, 1))
+
+	// via json.Unmarshal
+	matrices := []byte(`[[[1,2],[3,4]],[[5,6,7]]]`)
+	var ms []*matrix.Matrix[int]
+	err = json.Unmarshal(matrices, &ms)
+	assert.Nil(t, err)
+	assert.Len(t, ms, 2)
+	assert.Equal(t, 2, ms[0].Get(0, 1))
+	assert.Equal(t, 7, ms[1].Get(0, 2))
+
+	// invalid JSON
+	err = m.UnmarshalJSON([]byte(`invalid`))
+	assert.NotNil(t, err)
+
+	// empty array
+	err = m.UnmarshalJSON([]byte(`[]`))
+	assert.ErrorIs(t, err, matrix.ErrInvalidDimensions)
+
+	// empty inner array
+	err = m.UnmarshalJSON([]byte(`[[]]`))
+	assert.ErrorIs(t, err, matrix.ErrInvalidDimensions)
+
+	// inconsistent lengths
+	err = m.UnmarshalJSON([]byte(`[[1,2],[3]]`))
+	assert.ErrorIs(t, err, matrix.ErrIncompatibleDataDimensions)
+}
+
+func TestMatrix_MarshallJSON(t *testing.T) {
+	// int matrix
+	m := matrix.CreateFromSlice([][]int{{1, 2, 3}, {4, 5, 6}})
+	data, err := m.MarshalJSON()
+	assert.Nil(t, err)
+	assert.NotNil(t, data)
+
+	expected := `[[1,2,3],[4,5,6]]`
+	assert.Equal(t, expected, string(data))
+
+	// float matrix
+	mf := matrix.CreateFromSlice([][]float64{{1.5, 2.5}, {3.5, 4.5}})
+	data, err = mf.MarshalJSON()
+	assert.Nil(t, err)
+	assert.NotNil(t, data)
+	expectedFloat := `[[1.5,2.5],[3.5,4.5]]`
+	assert.Equal(t, expectedFloat, string(data))
+
+	// slice of matrices via json.Marshal
+	m1 := matrix.CreateFromSlice([][]int{{1, 2}, {3, 4}})
+	m2 := matrix.CreateFromSlice([][]int{{5, 6, 7}})
+	matrices := []*matrix.Matrix[int]{m1, m2}
+
+	data, err = json.Marshal(matrices)
+	assert.Nil(t, err)
+	expected = `[[[1,2],[3,4]],[[5,6,7]]]`
+	assert.Equal(t, expected, string(data))
+}