feat: bencoder decoder implementation and testing and documenting

Signed-off-by: nabil salah <[email protected]>

.github/workflows/go.yml

@@ -0,0 +1,32 @@
+# This workflow will build a golang project
+# For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-go
+
+name: Go
+
+on:
+  push:
+    branches: [ "development","main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+
+  Check:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up Go
+      uses: actions/setup-go@v4
+      with:
+        go-version: '1.22.4'
+
+    - name: golangci-lint
+      uses: golangci/golangci-lint-action@v3
+
+    - name: gofmt
+      run: make format
+
+
+    - name: Test
+      run: make test

Makefile

@@ -0,0 +1,5 @@
+test:
+	go test -v -cover ./...
+
+format:
+	go fmt ./...

README.md

@@ -1 +1,42 @@
-# bencode-nabil
+# bencode-nabil
+
+Encoder and Decode of Bencode
+
+## Installation
+
+As a library
+
+```shell
+go get github.com/codescalersinternships/bencode-nabil/pkg
+```
+
+## Usage
+
+in your Go app you can do something like
+
+```go
+package main
+
+import (
+	"fmt"
+
+	bencoder "github.com/codescalersinternships/bencode-nabil/pkg"
+)
+
+
+
+
+func main() {
+	s := "d3:bar4:spam3:fooi42ee"
+
+	ret,_ := bencoder.Encoder(s)
+	fmt.Println(ret)
+}
+
+```
+
+## Testing
+
+```shell
+make test
+```

go.mod

@@ -0,0 +1,10 @@
+module github.com/codescalersinternships/bencode-nabil
+
+go 1.22.4
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/testify v1.9.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -0,0 +1,11 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-stack/stack v1.8.1 h1:ntEHSVwIt7PNXNpgPmVfMrNhLtgjlmnZha2kOpuRiDw=
+github.com/go-stack/stack v1.8.1/go.mod h1:dcoOX6HbPZSZptuspn9bctJ+N/CnF5gGygcUP3XYfe4=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
+github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

pkg/bencoder.go

@@ -0,0 +1,176 @@
+package bencoder
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func readInteger(idx *int, str *string, terminator string) (int64, error) {
+	out := ""
+	lim := strings.Index((*str)[*idx:], terminator)
+	if lim == -1 {
+		return -1, fmt.Errorf("%s","error of terminator wasn't found")
+	}
+	lim = lim + (*idx)
+	out = (*str)[*idx:lim]
+	*idx = lim 
+	integer, err := strconv.ParseInt(out, 10, 64)
+	if err != nil {
+		return -1, err
+	}
+	return integer, nil
+}
+
+func readBulkString(idx *int, str *string) (interface{}, error) {
+	out := ""
+	length, err := readInteger(idx, str,":")
+	if err != nil {
+		return "", err
+	}
+	if length == -1 {
+		return nil, nil
+	}
+	(*idx)++
+	lim := (*idx) + int(length)
+	if lim > len(*str) {
+		return "", fmt.Errorf("%s","error of string lenght isn't enough")
+	}
+	out = (*str)[*idx:lim]
+	if out == "-1" {
+		return "", nil
+	}
+	*idx = lim -1
+	return out, nil
+}
+
+
+func readMap(idx *int, str *string) (map[interface{}]interface{}, error) {
+	var out = make(map[interface{}]interface{})
+	var prev interface{}
+	for i := 0; ; i++ {
+		var val interface{}
+		if (*str)[*idx] == 'i' {
+			(*idx)++
+			integer, err := readInteger(idx, str,"e")
+			if err != nil {
+				return nil, err
+			}
+			val = integer
+			(*idx)++
+			if i%2 == 1 {
+				out[prev] = val
+			}
+
+			prev = val
+			continue
+		}
+		if (*str)[*idx] >= '0' && (*str)[*idx] <= '9' {
+			bulkString, err := readBulkString(idx, str)
+			if err != nil {
+				return nil, err
+			}
+			val = bulkString
+			(*idx)++
+			if i%2 == 1 {
+				out[prev] = val
+			}
+
+			prev = val
+			continue
+		}
+		if (*str)[*idx] == 'l' {
+			(*idx)++
+			array, err := Decoder(*str, idx)
+			if err != nil {
+				return nil, err
+			}
+			val = array
+			(*idx)++
+			if i%2 == 1 {
+				out[prev] = val
+			}
+
+			prev = val
+			continue
+		}
+
+		if (*str)[*idx] == 'd' {
+			(*idx)++
+			respMap, err := readMap(idx, str)
+			if err != nil {
+				return nil, err
+			}
+			val = respMap
+			(*idx)++
+			if i%2 == 1 {
+				out[prev] = val
+			}
+
+			prev = val
+			continue
+		}
+		if (*str)[*idx] == 'e' {
+			break
+		}
+	}
+	return out, nil
+}
+
+// Decoder reads an bencoded string, returning an array of interfaces of items
+func Decoder(str string, start ...*int) (interface{}, error) {
+	var out []interface{}
+	var idx int = 0
+	if len(start) > 0 {
+		idx = *start[0]
+	}
+	for ; idx < len(str); idx++ {
+		if str[idx] == 'i' {
+			idx++
+			integer, err := readInteger(&idx, &str,"e")
+			if err != nil {
+				return nil, err
+			}
+			out = append(out, integer)
+			continue
+		}
+		if str[idx] >= '0' && str[idx] <= '9' {
+			bulkString, err := readBulkString(&idx, &str)
+			if err != nil {
+				return nil, err
+			}
+			out = append(out, bulkString)
+			continue
+		}
+		if str[idx] == 'l' {
+			idx++
+			array, err := Decoder(str, &idx)
+			if err != nil {
+				return nil, err
+			}
+			out = append(out, array)
+			continue
+		}
+
+		if str[idx] == 'd' {
+			idx++
+			respMap, err := readMap(&idx, &str)
+			if err != nil {
+				return nil, err
+			}
+			out = append(out, respMap)
+			continue
+		}
+		if str[idx] == 'e' {
+			break
+		}
+	}
+	if len(start) > 0 {
+		*start[0] = idx
+	}
+	if len(out) == 1 {
+		return out[0], nil
+	}
+	return out, nil
+}
+

pkg/bencoder_test.go

@@ -0,0 +1,94 @@
+package bencoder
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+
+func TestDecoder(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected interface{}
+		expectedError bool
+	}{
+		{
+			name:     "Simple string",
+			input:    "4:spam",
+			expected: "spam",
+			expectedError: false,
+		},
+		{
+			name:     "Integer",
+			input:    "i123e",
+			expected: int64(123),
+			expectedError: false,
+		},
+		{
+			name:     "List of strings",
+			input:    "l4:spam4:eggse",
+			expected: []interface{}{"spam", "eggs"},
+			expectedError: false,
+		},
+		{
+			name: "Dictionary with strings",
+			input:    "d3:cow3:moo4:spam4:eggse",
+			expected: map[interface {}]interface {}(
+				map[interface {}]interface {}{
+					"cow":"moo", "spam":"eggs",
+				},
+			),
+			expectedError: false,
+		},
+		{
+			name:     "Invalid bencoded string",
+			input:    "invalid",
+			expected: nil,
+			expectedError: true,
+		},
+		{
+			name: "Dictionary with strings and integers",
+			input:    "d3:cow3:moo4:spami123ee",
+			expected: map[interface {}]interface {}(
+				map[interface {}]interface {}{
+					"cow":"moo", "spam":int64(123),
+				},
+			),
+			expectedError: false,
+		},
+		{
+			name: "Dictionary with strings and arrays",
+			input:    "d3:cow3:moo4:spaml4:spam4:eggsee",
+			expected: map[interface {}]interface {}(
+				map[interface {}]interface {}{
+					"cow":"moo", 
+					"spam":[]interface {}{"spam", "eggs"},
+				},
+			),
+			expectedError: false,
+		},
+		{
+			name: "Dictionary with strings and dictionaries",
+			input:    "d3:cow3:moo4:spamd3:cow3:moo4:spam4:eggsee",
+			expected: map[interface {}]interface {}(
+				map[interface {}]interface {}{
+					"cow":"moo", 
+					"spam":map[interface {}]interface {}{"cow":"moo", "spam":"eggs"},
+				},
+			),
+			expectedError: false,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			got, err := Decoder(test.input)
+			if test.expectedError {
+				assert.Error(t, err)
+			}
+			assert.Equal(t, test.expected, got)
+		})
+	}
+}