tupleconv: implement basics

- `Mapper[T]`: this in an interface for converting from a certain
fixed type to any.
Some basic mappers were implemented: parsers for tarantool types.

- `Converter`: this is a struct, that converts tuples
using `fmt`: mappers list.

- `tt_helpers`: these are auxiliary functions
 used to build `fmt` for the `Converter`.

Relates to #1

converter.go

@@ -0,0 +1,100 @@
+package tupleconv
+
+import (
+	"errors"
+	"fmt"
+)
+
+// ErrUnexpectedValue is unexpected value error.
+type ErrUnexpectedValue struct {
+	val any
+}
+
+// NewErrUnexpectedValue creates ErrUnexpectedValue by the value.
+func NewErrUnexpectedValue(val any) error {
+	return &ErrUnexpectedValue{val: val}
+}
+
+// Error is the error implementation for ErrUnexpectedValue.
+func (err *ErrUnexpectedValue) Error() string {
+	return fmt.Sprintf("unexpected value: %v", err.val)
+}
+
+var ErrWrongTupleLength = errors.New(
+	"tuple length should be equal to the length of the mappers list",
+)
+
+var ErrInvalidFmt = errors.New("invalid fmt")
+
+// Converter performs tuple conversion.
+type Converter[T any] struct {
+	fmt      []Mapper[T]
+	isSingle bool
+}
+
+// NewConverter creates Converter.
+func NewConverter[T any](fmt []Mapper[T]) (*Converter[T], error) {
+	if len(fmt) == 0 {
+		return nil, ErrInvalidFmt
+	}
+	conv := &Converter[T]{fmt: fmt}
+	return conv, nil
+}
+
+// NewConverterSingle creates a Converter with a single type as a format.
+func NewConverterSingle[T any](fmt Mapper[T]) (*Converter[T], error) {
+	conv := &Converter[T]{
+		fmt:      []Mapper[T]{fmt},
+		isSingle: true,
+	}
+	return conv, nil
+}
+
+// validateTuple validates tuple in accordance with the Converter properties.
+func (conv *Converter[T]) validateTuple(tuple []T) error {
+	if conv.isSingle {
+		return nil
+	}
+	if len(conv.fmt) != len(tuple) {
+		return ErrWrongTupleLength
+	}
+	return nil
+}
+
+// ConvertVerbose converts tuple.
+// It returns converted slice, conversion errors slice, API error.
+func (conv *Converter[T]) ConvertVerbose(tuple []T) ([]any, []error, error) {
+	if err := conv.validateTuple(tuple); err != nil {
+		return nil, nil, err
+	}
+	result := make([]any, len(tuple))
+	convErrors := make([]error, len(tuple))
+	for i, field := range tuple {
+		c := conv.fmt[0]
+		if !conv.isSingle {
+			c = conv.fmt[i]
+		}
+		result[i], convErrors[i] = c.Map(field)
+	}
+	return result, convErrors, nil
+}
+
+// Convert converts tuple until the first error.
+func (conv *Converter[T]) Convert(tuple []T) ([]any, error) {
+	if err := conv.validateTuple(tuple); err != nil {
+		return nil, err
+	}
+	var err error
+	result := make([]any, len(tuple))
+	for i, field := range tuple {
+		c := conv.fmt[0]
+		if !conv.isSingle {
+			c = conv.fmt[i]
+		}
+		result[i], err = c.Map(field)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return result, nil
+}

converter_test.go

@@ -0,0 +1,179 @@
+package tupleconv
+
+import (
+	"errors"
+	"fmt"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
+func TestValidateTuple(t *testing.T) {
+	sampleMapper := NewFuncMapper(func(t string) (any, error) {
+		return t + "1", nil
+	})
+
+	singleConv, err := NewConverterSingle[string](sampleMapper)
+	require.NoError(t, err)
+
+	assert.NoError(t, singleConv.validateTuple([]string{"a", "b", "c"}))
+	assert.NoError(t, singleConv.validateTuple([]string{""}))
+	assert.NoError(t, singleConv.validateTuple([]string{"a"}))
+
+	conv, err := NewConverter([]Mapper[string]{sampleMapper, sampleMapper})
+	require.NoError(t, err)
+
+	assert.NoError(t, conv.validateTuple([]string{"a", "b"}))
+	assert.Error(t, conv.validateTuple([]string{"a"}))
+	assert.Error(t, conv.validateTuple([]string{"a", "b", "c"}))
+}
+
+func TestSingleConverter(t *testing.T) {
+	stringer := NewFuncMapper(func(t any) (any, error) {
+		return fmt.Sprintln(t), nil
+	})
+
+	encoder, err := NewConverterSingle[any](stringer)
+	require.NoError(t, err)
+
+	cases := []struct {
+		name     string
+		tuple    []any
+		expected []any
+	}{
+		{
+			name:     "empty",
+			tuple:    []any{},
+			expected: []any{},
+		},
+		{
+			name: "different types",
+			tuple: []any{
+				"a",
+				1,
+				nil,
+				map[string]string{
+					"1": "2",
+					"3": "4",
+				},
+			},
+			expected: []any{
+				"a\n",
+				"1\n",
+				"<nil>\n",
+				"map[1:2 3:4]\n",
+			},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			actual, err := encoder.Convert(tc.tuple)
+			assert.NoError(t, err)
+			assert.Equal(t, tc.expected, actual)
+
+			actualVerbose, errorList, err := encoder.ConvertVerbose(tc.tuple)
+			assert.NoError(t, err)
+			assert.Equal(t, tc.expected, actualVerbose)
+			assert.Equal(t, len(tc.expected), len(errorList))
+			for _, err := range errorList {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}
+
+func TestConverter(t *testing.T) {
+	idealMapper := NewFuncMapper(func(t string) (any, error) {
+		return 42, nil
+	})
+
+	someError := errors.New("some error")
+	nonIdealMapper := NewFuncMapper(func(t string) (any, error) {
+		if t == "bad" {
+			return "", someError
+		}
+		return t, nil
+	})
+
+	decoder, err := NewConverter([]Mapper[string]{idealMapper, nonIdealMapper})
+	require.NoError(t, err)
+
+	t.Run("Convert", func(t *testing.T) {
+		cases := []struct {
+			name          string
+			tuple         []string
+			expectedTuple []any
+			wantErr       bool
+		}{
+			{
+				name:          "all is ok",
+				tuple:         []string{"1", "2"},
+				expectedTuple: []any{42, "2"},
+			},
+			{
+				name:    "wrong tuple length",
+				tuple:   []string{"1"},
+				wantErr: true,
+			},
+			{
+				name:    "decoding error",
+				tuple:   []string{"1", "bad"},
+				wantErr: true,
+			},
+		}
+
+		for _, tc := range cases {
+			t.Run(tc.name, func(t *testing.T) {
+				actualTuple, err := decoder.Convert(tc.tuple)
+				if tc.wantErr {
+					assert.Error(t, err)
+				} else {
+					assert.NoError(t, err)
+					assert.Equal(t, tc.expectedTuple, actualTuple)
+				}
+			})
+		}
+	})
+
+	t.Run("ConvertVerbose", func(t *testing.T) {
+		cases := []struct {
+			name              string
+			tuple             []string
+			expectedTuple     []any
+			expectedErrorList []error
+			wantAPIError      bool
+		}{
+			{
+				name:              "all is ok",
+				tuple:             []string{"1", "2"},
+				expectedTuple:     []any{42, "2"},
+				expectedErrorList: []error{nil, nil},
+				wantAPIError:      false,
+			},
+			{
+				name:         "wrong tuple length",
+				tuple:        []string{"1", "2", "3", "4"},
+				wantAPIError: true,
+			},
+			{
+				name:              "decoding error",
+				tuple:             []string{"1000", "bad"},
+				expectedTuple:     []any{42, ""},
+				expectedErrorList: []error{nil, someError},
+			},
+		}
+		for _, tc := range cases {
+			t.Run(tc.name, func(t *testing.T) {
+				actualTuple, errorList, err := decoder.ConvertVerbose(tc.tuple)
+				if tc.wantAPIError {
+					assert.Error(t, err)
+				} else {
+					assert.NoError(t, err)
+					assert.Equal(t, tc.expectedTuple, actualTuple)
+					assert.Equal(t, tc.expectedErrorList, errorList)
+				}
+			})
+		}
+	})
+}

go.mod

@@ -0,0 +1,26 @@
+module github.com/tarantool/go-tupleconv
+
+go 1.19
+
+require (
+	github.com/google/uuid v1.3.0
+	github.com/shopspring/decimal v1.3.1
+	github.com/stretchr/testify v1.7.1
+	github.com/tarantool/go-tarantool v1.12.0
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.0 // indirect
+	github.com/golang/protobuf v1.3.1 // indirect
+	github.com/mattn/go-pointer v0.0.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/spacemonkeygo/spacelog v0.0.0-20180420211403-2296661a0572 // indirect
+	github.com/tarantool/go-openssl v0.0.8-0.20230307065445-720eeb389195 // indirect
+	github.com/vmihailenco/msgpack/v5 v5.3.5 // indirect
+	github.com/vmihailenco/tagparser/v2 v2.0.0 // indirect
+	golang.org/x/net v0.0.0-20201021035429-f5854403a974 // indirect
+	golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 // indirect
+	google.golang.org/appengine v1.6.7 // indirect
+	gopkg.in/vmihailenco/msgpack.v2 v2.9.2 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
+)

go.sum

@@ -0,0 +1,53 @@
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+github.com/golang/protobuf v1.3.1 h1:YF8+flBXS5eO826T4nzqPrxfhQThhXl0YzfuUPu4SBg=
+github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/google/uuid v1.3.0 h1:t6JiXgmwXMjEs8VusXIJk2BXHsn+wx8BZdTaoZ5fu7I=
+github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
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