diff --git a/.github/workflows/golangci-lint.yml b/.github/workflows/golangci-lint.yml
new file mode 100644
index 0000000..00f314d
--- /dev/null
+++ b/.github/workflows/golangci-lint.yml
@@ -0,0 +1,23 @@
+name: golangci-lint
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  golangci:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+      - uses: actions/setup-go@v6
+        with:
+          go-version: stable
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v9
+        with:
+          version: v2.6
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..f576800
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,19 @@
+name: Go
+on: [push]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v5
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.25.0'
+      - name: Install dependencies
+        run: go get .
+      - name: Build
+        run: go build -v ./...
+      - name: Test with the Go CLI
+        run: go test
\ No newline at end of file
diff --git a/.golangci.yml b/.golangci.yml
new file mode 100644
index 0000000..64bb863
--- /dev/null
+++ b/.golangci.yml
@@ -0,0 +1,32 @@
+version: "2"
+
+linters:
+  enable:
+    - bodyclose
+    - errcheck
+    - goconst
+    - gocritic
+    - govet
+    - ineffassign
+    - mirror
+    - misspell
+    - nolintlint
+    - paralleltest
+    - revive
+    - staticcheck
+    - unconvert
+    - unparam
+    - unused
+    - whitespace
+
+formatters:
+  enable:
+    - gci
+    - gofmt
+    - goimports
+  settings:
+    gci:
+      sections:
+        - standard
+        - default
+        - localmodule
\ No newline at end of file
diff --git a/README.md b/README.md
index 8d70794..e40988f 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,23 @@
 # codemd
-Parse source code files and generate a markdown file
+
+Convert between markdown files containing code blocks and individual source files.
+
+## Installation
+
+```bash
+go install github.com/lynxai-team/codemd@latest
+```
+
+## Usage
+
+### Convert source files to markdown
+
+```bash
+codemd tomd -f main.go -f helper.js -o docs.md
+```
+
+Or scan a directory:
+
+```bash
+codemd tomd -d ./src -o docs.md
+```
diff --git a/codemd.go b/codemd.go
new file mode 100644
index 0000000..b2f9b17
--- /dev/null
+++ b/codemd.go
@@ -0,0 +1,319 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// Document represents a collection of code blocks that can be converted
+// between markdown and source files.
+type Document struct {
+	Blocks []CodeBlock
+}
+
+// CodeBlock represents a single code block with its metadata.
+type CodeBlock struct {
+	Filename string
+	Language string
+	Content  string
+}
+
+// NewDocument returns an empty Document.
+func NewDocument() *Document {
+	return &Document{
+		Blocks: []CodeBlock{},
+	}
+}
+
+// Reset clears all blocks from the document.
+func (d *Document) Reset() {
+	d.Blocks = []CodeBlock{}
+}
+
+// ParseMarkdown reads a markdown file and adds extracted code blocks to the document.
+func (d *Document) ParseMarkdown(markdownPath string) error {
+	data, err := os.ReadFile(markdownPath)
+	if err != nil {
+		return fmt.Errorf("failed to open file: %w", err)
+	}
+
+	lines := strings.Split(string(data), "\n")
+
+	var inCodeBlock bool
+	var language string
+	var content strings.Builder
+	var lastHeaderFilename string
+	fileCounter := 0
+
+	for _, line := range lines {
+		if inCodeBlock {
+			if strings.HasPrefix(strings.TrimSpace(line), "```") {
+				fileCounter++
+
+				d.Blocks = append(d.Blocks, CodeBlock{
+					Filename: filename(lastHeaderFilename, language, fileCounter),
+					Language: language,
+					Content:  content.String(),
+				})
+
+				inCodeBlock = false
+				language = ""
+				content.Reset()
+				lastHeaderFilename = ""
+				continue
+			}
+			content.WriteString(line + "\n")
+			continue
+		}
+
+		switch line := strings.TrimSpace(line); {
+		case strings.HasPrefix(line, "```"):
+			inCodeBlock = true
+			language = strings.TrimSpace(line[3:])
+		case strings.HasPrefix(line, "## "):
+			headerText := strings.TrimSpace(line[3:])
+			if headerText != "" {
+				lastHeaderFilename = headerText
+			}
+		case line == "":
+			continue
+		default:
+			lastHeaderFilename = ""
+		}
+	}
+
+	return nil
+}
+
+// filename determines the appropriate filename for a code block.
+// It prefers the header filename if its extension matches the language,
+// otherwise generates a filename based on the language and counter.
+func filename(headerFilename, language string, counter int) string {
+	defaultName := fmt.Sprintf("file%d", counter)
+
+	ext := determineFileExtension(language)
+	if ext == "" {
+		return defaultName
+	}
+
+	if headerFilename != "" && filepath.Ext(headerFilename) == ext {
+		return headerFilename
+	}
+
+	return fmt.Sprintf("file%d%s", counter, ext)
+}
+
+// ParseFiles reads source files and adds them as blocks to the document.
+func (d *Document) ParseFiles(filePaths ...string) error {
+	for _, filePath := range filePaths {
+		if _, err := os.Stat(filePath); os.IsNotExist(err) {
+			return fmt.Errorf("file does not exist: %s", filePath)
+		}
+
+		filename := filepath.Base(filePath)
+		language := detectSourceLanguage(filename)
+		if language == "" {
+			continue
+		}
+
+		content, err := os.ReadFile(filePath)
+		if err != nil {
+			return fmt.Errorf("failed to read file %s: %w", filePath, err)
+		}
+
+		block := CodeBlock{
+			Filename: filePath,
+			Language: language,
+			Content:  string(content),
+		}
+
+		d.Blocks = append(d.Blocks, block)
+	}
+
+	return nil
+}
+
+// ParseDir recursively scans a directory for source files and adds them to the document.
+func (d *Document) ParseDir(dir string) error {
+	files, err := getFilesFromDirectory(dir)
+	if err != nil {
+		return fmt.Errorf("failed to scan directory: %w", err)
+	}
+
+	sort.Strings(files)
+
+	return d.ParseFiles(files...)
+}
+
+// ToMarkdown writes the Document as a markdown file.
+func (d *Document) ToMarkdown(outputPath string) error {
+	file, err := os.Create(outputPath)
+	if err != nil {
+		return fmt.Errorf("failed to create file: %w", err)
+	}
+	defer func() { _ = file.Close() }()
+
+	if _, err := file.WriteString("# Code Files\n\n"); err != nil {
+		return fmt.Errorf("failed to write header: %w", err)
+	}
+
+	for i, block := range d.Blocks {
+		if i > 0 {
+			if _, err := file.WriteString("\n"); err != nil {
+				return fmt.Errorf("failed to write spacing: %w", err)
+			}
+		}
+
+		if _, err := fmt.Fprintf(file, "## %s\n\n", block.Filename); err != nil {
+			return fmt.Errorf("failed to write filename header: %w", err)
+		}
+
+		if _, err := fmt.Fprintf(file, "```%s\n", block.Language); err != nil {
+			return fmt.Errorf("failed to write code block start: %w", err)
+		}
+
+		if _, err := fmt.Fprintf(file, "%s```\n", block.Content); err != nil {
+			return fmt.Errorf("failed to write code block: %w", err)
+		}
+	}
+
+	return nil
+}
+
+// ToSourceFiles writes the Document as individual source files.
+func (d *Document) ToSourceFiles(outputDir string) error {
+	if err := os.MkdirAll(outputDir, 0755); err != nil {
+		return fmt.Errorf("failed to create output directory: %w", err)
+	}
+
+	for _, block := range d.Blocks {
+		fullPath := filepath.Join(outputDir, block.Filename)
+
+		dir := filepath.Dir(fullPath)
+		if err := os.MkdirAll(dir, 0755); err != nil {
+			return fmt.Errorf("failed to create directory %s: %w", dir, err)
+		}
+
+		if err := os.WriteFile(fullPath, []byte(block.Content), 0644); err != nil {
+			return fmt.Errorf("failed to write file %s: %w", fullPath, err)
+		}
+	}
+
+	return nil
+}
+
+// defaultSkipPatterns contains patterns for paths to skip during directory scanning
+var defaultSkipPatterns = []string{
+	".git/",
+	".gitignore",
+	".gitattributes",
+	".svn/",
+	".hg/",
+
+	"node_modules/",
+	"vendor/",
+	".venv/",
+	"venv/",
+	"env/",
+	"__pycache__/",
+
+	"dist/",
+	"build/",
+	"target/",
+	"bin/",
+	"obj/",
+	".next/",
+	"out/",
+	"coverage/",
+
+	".vscode/",
+	".idea/",
+	"*.swp",
+	"*.swo",
+	".DS_Store",
+	"Thumbs.db",
+
+	".pytest_cache/",
+	".tox/",
+	"*.egg-info/",
+	".mypy_cache/",
+	".coverage",
+
+	".env",
+	".env.*",
+	".npmrc",
+
+	"package-lock.json",
+	"yarn.lock",
+	"Cargo.lock",
+	"pnpm-lock.yaml",
+	"poetry.lock",
+	"go.sum",
+
+	"*.exe",
+	"*.dll",
+	"*.so",
+	"*.dylib",
+	"*.o",
+	"*.obj",
+	"*.a",
+	"*.lib",
+
+	"*.log",
+	"*.tmp",
+	"*.temp",
+
+	".*",
+}
+
+// getFilesFromDirectory returns all source files in a directory recursively,
+// skipping common non-source directories and files.
+func getFilesFromDirectory(dir string) ([]string, error) {
+	var files []string
+	err := filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if shouldSkip(path, info.IsDir(), defaultSkipPatterns) {
+			if info.IsDir() {
+				return filepath.SkipDir
+			}
+			return nil
+		}
+
+		if !info.IsDir() {
+			files = append(files, path)
+		}
+		return nil
+	})
+	return files, err
+}
+
+// shouldSkip checks if a path matches any skip pattern
+func shouldSkip(path string, isDir bool, patterns []string) bool {
+	name := filepath.Base(path)
+
+	for _, pattern := range patterns {
+		if strings.HasSuffix(pattern, "/") {
+			if !isDir {
+				continue
+			}
+			dirPattern := strings.TrimSuffix(pattern, "/")
+			if matched, _ := filepath.Match(dirPattern, name); matched {
+				return true
+			}
+		} else {
+			if matched, _ := filepath.Match(pattern, name); matched {
+				if pattern == ".*" && name == "." {
+					continue
+				}
+				return true
+			}
+		}
+	}
+	return false
+}
diff --git a/codemd_test.go b/codemd_test.go
new file mode 100644
index 0000000..bb2209a
--- /dev/null
+++ b/codemd_test.go
@@ -0,0 +1,87 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMarkdownToSourceFiles(t *testing.T) {
+	t.Parallel()
+
+	doc := NewDocument()
+	tempDir := t.TempDir()
+
+	require.NoError(t, doc.ParseMarkdown("testdata/golden.md"))
+	require.NoError(t, doc.ToSourceFiles(tempDir))
+
+	filePairs := []struct {
+		actual string
+		wanted string
+	}{
+		{"main.c", "testdata/code/main.c"},
+		{"helper.js", "testdata/code/helper.js"},
+		{"file3.css", "testdata/code/main.css"},
+	}
+
+	for _, cf := range filePairs {
+		assertEqualFile(
+			t,
+			filepath.Join(tempDir, cf.actual),
+			cf.wanted,
+		)
+	}
+}
+
+func TestSourceFilesToMarkdown(t *testing.T) {
+	t.Parallel()
+
+	cases := map[string]struct {
+		parseFunc func(doc *Document) error
+	}{
+		"individual files": {
+			parseFunc: func(doc *Document) error {
+				return doc.ParseFiles(
+					"testdata/code/helper.js",
+					"testdata/code/main.c",
+					"testdata/code/main.css",
+				)
+			},
+		},
+		"directory": {
+			parseFunc: func(doc *Document) error {
+				return doc.ParseDir("testdata/code")
+			},
+		},
+	}
+
+	for name, cc := range cases {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			doc := NewDocument()
+
+			require.NoError(t, cc.parseFunc(doc))
+
+			outputPath := filepath.Join(t.TempDir(), "generated.md")
+
+			require.NoError(t, doc.ToMarkdown(outputPath))
+			assertEqualFile(t, outputPath, "testdata/golden-code.md")
+		})
+	}
+}
+
+func assertEqualFile(t *testing.T, actualPath, expectedPath string) {
+	t.Helper()
+
+	actualContent, err := os.ReadFile(actualPath)
+	require.NoError(t, err, "read file %s", actualPath)
+
+	expectedContent, err := os.ReadFile(expectedPath)
+	require.NoError(t, err, "read file %s", expectedPath)
+
+	assert.Equal(t, string(expectedContent), string(actualContent))
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..1af0198
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,19 @@
+module github.com/lynxai-team/codemd
+
+go 1.25.0
+
+require (
+	github.com/spf13/cobra v1.10.2
+	github.com/stretchr/testify v1.11.1
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/kr/pretty v0.3.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/rogpeppe/go-internal v1.13.1 // indirect
+	github.com/spf13/pflag v1.0.9 // indirect
+	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..4074d86
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,32 @@
+github.com/cpuguy83/go-md2man/v2 v2.0.6/go.mod h1:oOW0eioCTA6cOiMLiUPZOpcVxMig6NIQQ7OS05n1F4g=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
+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/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
+github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
+github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e/go.mod h1:pJLUxLENpZxwdsKMEsNbx1VGcRFpLqf3715MtcvvzbA=
+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/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
+github.com/rogpeppe/go-internal v1.13.1 h1:KvO1DLK/DRN07sQ1LQKScxyZJuNnedQ5/wKSR38lUII=
+github.com/rogpeppe/go-internal v1.13.1/go.mod h1:uMEvuHeurkdAXX61udpOXGD/AzZDWNMNyH2VO9fmH0o=
+github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/spf13/cobra v1.10.2 h1:DMTTonx5m65Ic0GOoRY2c16WCbHxOOw6xxezuLaBpcU=
+github.com/spf13/cobra v1.10.2/go.mod h1:7C1pvHqHw5A4vrJfjNwvOdzYu0Gml16OCs2GRiTUUS4=
+github.com/spf13/pflag v1.0.9 h1:9exaQaMOCwffKiiiYk6/BndUBv+iRViNW+4lEMi0PvY=
+github.com/spf13/pflag v1.0.9/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..d2c024c
--- /dev/null
+++ b/main.go
@@ -0,0 +1,139 @@
+// codemd-lite is a lightweight tool to convert between markdown files
+// containing code blocks and individual source code files.
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+func main() {
+	cmd := CommandMdCodeLite()
+
+	if err := cmd.Execute(); err != nil {
+		cmd.PrintErr(err)
+		os.Exit(1)
+	}
+}
+
+func CommandMdCodeLite() *cobra.Command {
+	var cmd = &cobra.Command{
+		Use:   "codemd",
+		Short: "A tool to convert between markdown and source files",
+		CompletionOptions: cobra.CompletionOptions{
+			DisableDefaultCmd: true,
+		},
+	}
+
+	cmd.AddCommand(CommandToCode())
+	cmd.AddCommand(CommandToMarkdown())
+
+	return cmd
+}
+
+func CommandToCode() *cobra.Command {
+	var mdFile string
+	var outputDir string
+
+	cmd := &cobra.Command{
+		Use:     "tocode",
+		Short:   "Convert markdown file to source files",
+		Example: `codemd tocode -i docs.md -o src`,
+		Args:    cobra.NoArgs,
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			if mdFile == "" {
+				return fmt.Errorf("markdown file is required (use --input or -i)")
+			}
+			if outputDir == "" {
+				return fmt.Errorf("output directory is required (use --output or -o)")
+			}
+
+			doc := NewDocument()
+
+			cmd.Printf("Parsing markdown file: %s\n", mdFile)
+			if err := doc.ParseMarkdown(mdFile); err != nil {
+				return fmt.Errorf("failed to parse markdown: %w", err)
+			}
+
+			cmd.Printf("Extracting %d code blocks to: %s\n", len(doc.Blocks), outputDir)
+			if err := doc.ToSourceFiles(outputDir); err != nil {
+				return fmt.Errorf("failed to extract files: %w", err)
+			}
+
+			cmd.Printf("Successfully extracted:")
+			for _, block := range doc.Blocks {
+				cmd.Printf("  - %s (%s)\n", block.Filename, block.Language)
+			}
+
+			return nil
+		},
+	}
+
+	cmd.Flags().StringVarP(&mdFile, "input", "i", "", "Input markdown file to extract from")
+	_ = cmd.MarkFlagRequired("input")
+
+	cmd.Flags().StringVarP(&outputDir, "output", "o", "", "Output directory for extracted files")
+	_ = cmd.MarkFlagRequired("output")
+
+	return cmd
+}
+
+func CommandToMarkdown() *cobra.Command {
+	var outputFile string
+	var directory string
+	var files []string
+
+	cmd := &cobra.Command{
+		Use:     "tomd",
+		Short:   "Convert source files to markdown",
+		Example: `codemd tomd -f file1 -f file2 -o output.md`,
+		Args:    cobra.NoArgs,
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			if outputFile == "" {
+				return fmt.Errorf("output file is required (use --output or -o)")
+			}
+
+			doc := NewDocument()
+
+			if directory == "" && len(files) == 0 {
+				return fmt.Errorf("must specify either --dir or --files (or both)")
+			}
+
+			if directory != "" {
+				cmd.Printf("Scanning directory: %s\n", directory)
+				if err := doc.ParseDir(directory); err != nil {
+					return fmt.Errorf("failed to scan directory: %w", err)
+				}
+			}
+
+			if len(files) > 0 {
+				cmd.Printf("Parsing %d files\n", len(files))
+				if err := doc.ParseFiles(files...); err != nil {
+					return fmt.Errorf("failed to parse files: %w", err)
+				}
+			}
+
+			cmd.Printf("Generating markdown with %d code blocks: %s\n", len(doc.Blocks), outputFile)
+			if err := doc.ToMarkdown(outputFile); err != nil {
+				return fmt.Errorf("failed to generate markdown: %w", err)
+			}
+
+			cmd.Printf("Successfully generated markdown with:")
+			for _, block := range doc.Blocks {
+				cmd.Printf("  - %s (%s)\n", block.Filename, block.Language)
+			}
+
+			return nil
+		},
+	}
+
+	cmd.Flags().StringVarP(&outputFile, "output", "o", "", "Output markdown file")
+	_ = cmd.MarkFlagRequired("output")
+
+	cmd.Flags().StringVarP(&directory, "dir", "d", "", "Directory to scan for source files")
+	cmd.Flags().StringSliceVarP(&files, "files", "f", nil, "Files to include")
+
+	return cmd
+}
diff --git a/markdown.go b/markdown.go
new file mode 100644
index 0000000..1e3c518
--- /dev/null
+++ b/markdown.go
@@ -0,0 +1,175 @@
+package main
+
+import (
+	"path/filepath"
+	"strings"
+)
+
+var extToLanguage = map[string]string{
+	// Programming languages
+	".go":    "go",
+	".js":    "javascript",
+	".ts":    "typescript",
+	".py":    "python",
+	".java":  "java",
+	".c":     "c",
+	".cpp":   "cpp",
+	".cxx":   "cpp",
+	".cs":    "csharp",
+	".php":   "php",
+	".rb":    "ruby",
+	".rs":    "rust",
+	".swift": "swift",
+	".kt":    "kotlin",
+	".scala": "scala",
+	".pl":    "perl",
+	".lua":   "lua",
+	".r":     "r",
+
+	// Web technologies
+	".html": "html",
+	".htm":  "html",
+	".css":  "css",
+	".xml":  "xml",
+	".json": "json",
+	".yml":  "yaml",
+	".yaml": "yaml",
+	".toml": "toml",
+
+	// Shell/scripting
+	".sh":   "bash",
+	".ps1":  "powershell",
+	".bat":  "batch",
+	".cmd":  "batch",
+	".fish": "fish",
+	".zsh":  "zsh",
+
+	// Database
+	".sql": "sql",
+
+	// Markup/config
+	".md":         "markdown",
+	".tex":        "latex",
+	".ini":        "ini",
+	".properties": "properties",
+	".dockerfile": "dockerfile",
+	".makefile":   "makefile",
+	".gitignore":  "gitignore",
+
+	// Data formats
+	".csv":   "csv",
+	".jsonl": "jsonl",
+	".tsv":   "tsv",
+
+	// Other formats
+	".txt":  "text",
+	".diff": "diff",
+	".log":  "log",
+	".conf": "conf",
+}
+
+var languageToExt = map[string]string{
+	// Programming languages
+	"go":         ".go",
+	"javascript": ".js",
+	"js":         ".js",
+	"typescript": ".ts",
+	"ts":         ".ts",
+	"python":     ".py",
+	"py":         ".py",
+	"java":       ".java",
+	"c":          ".c",
+	"cpp":        ".cpp",
+	"c++":        ".cpp",
+	"cxx":        ".cpp",
+	"csharp":     ".cs",
+	"c#":         ".cs",
+	"cs":         ".cs",
+	"php":        ".php",
+	"ruby":       ".rb",
+	"rb":         ".rb",
+	"rust":       ".rs",
+	"rs":         ".rs",
+	"swift":      ".swift",
+	"kotlin":     ".kt",
+	"kt":         ".kt",
+	"scala":      ".scala",
+	"perl":       ".pl",
+	"lua":        ".lua",
+	"r":          ".r",
+
+	// Web technologies
+	"html": ".html",
+	"css":  ".css",
+	"xml":  ".xml",
+	"json": ".json",
+	"yaml": ".yml",
+	"yml":  ".yml",
+	"toml": ".toml",
+
+	// Shell/scripting
+	"bash":       ".sh",
+	"shell":      ".sh",
+	"sh":         ".sh",
+	"powershell": ".ps1",
+	"ps1":        ".ps1",
+	"batch":      ".bat",
+	"cmd":        ".bat",
+	"bat":        ".bat",
+	"fish":       ".fish",
+	"zsh":        ".zsh",
+
+	// Database
+	"sql":        ".sql",
+	"mysql":      ".sql",
+	"postgresql": ".sql",
+	"postgres":   ".sql",
+	"sqlite":     ".sql",
+
+	// Markup/config
+	"markdown":   ".md",
+	"md":         ".md",
+	"latex":      ".tex",
+	"tex":        ".tex",
+	"ini":        ".ini",
+	"properties": ".properties",
+	"dockerfile": ".dockerfile",
+	"docker":     ".dockerfile",
+	"makefile":   ".makefile",
+	"make":       ".makefile",
+	"gitignore":  ".gitignore",
+
+	// Data formats
+	"csv":   ".csv",
+	"jsonl": ".jsonl",
+	"tsv":   ".tsv",
+
+	// Other formats
+	"text":   ".txt",
+	"txt":    ".txt",
+	"plain":  ".txt",
+	"diff":   ".diff",
+	"log":    ".log",
+	"conf":   ".conf",
+	"config": ".conf",
+}
+
+// detectSourceLanguage returns the programming language based on the filename extension.
+func detectSourceLanguage(filename string) string {
+	ext := strings.ToLower(filepath.Ext(filename))
+	if language, ok := extToLanguage[ext]; ok {
+		return language
+	}
+
+	return ""
+}
+
+// determineFileExtension returns the appropriate file extension for a given programming language.
+func determineFileExtension(language string) string {
+	key := strings.ToLower(language)
+	if ext, ok := languageToExt[key]; ok {
+		return ext
+	}
+
+	return ""
+}
diff --git a/testdata/code/.gitignore b/testdata/code/.gitignore
new file mode 100644
index 0000000..8e8874f
--- /dev/null
+++ b/testdata/code/.gitignore
@@ -0,0 +1 @@
+ignored-file.txt
diff --git a/testdata/code/helper.js b/testdata/code/helper.js
new file mode 100644
index 0000000..4ed55b5
--- /dev/null
+++ b/testdata/code/helper.js
@@ -0,0 +1,5 @@
+function add(a, b) {
+  return a + b;
+}
+
+module.exports = { add };
diff --git a/testdata/code/main.c b/testdata/code/main.c
new file mode 100644
index 0000000..0923337
--- /dev/null
+++ b/testdata/code/main.c
@@ -0,0 +1,6 @@
+#include <stdio.h>
+
+int main() {
+  printf("Hello, World!\n");
+  return 0;
+}
diff --git a/testdata/code/main.css b/testdata/code/main.css
new file mode 100644
index 0000000..ee014f1
--- /dev/null
+++ b/testdata/code/main.css
@@ -0,0 +1,9 @@
+body {
+  margin: 0;
+  font-family: Arial, sans-serif;
+}
+
+.container {
+  max-width: 1200px;
+  margin: 0 auto;
+}
diff --git a/testdata/golden-code.md b/testdata/golden-code.md
new file mode 100644
index 0000000..b7a0aff
--- /dev/null
+++ b/testdata/golden-code.md
@@ -0,0 +1,36 @@
+# Code Files
+
+## testdata/code/helper.js
+
+```javascript
+function add(a, b) {
+  return a + b;
+}
+
+module.exports = { add };
+```
+
+## testdata/code/main.c
+
+```c
+#include <stdio.h>
+
+int main() {
+  printf("Hello, World!\n");
+  return 0;
+}
+```
+
+## testdata/code/main.css
+
+```css
+body {
+  margin: 0;
+  font-family: Arial, sans-serif;
+}
+
+.container {
+  max-width: 1200px;
+  margin: 0 auto;
+}
+```
diff --git a/testdata/golden.md b/testdata/golden.md
new file mode 100644
index 0000000..25144ef
--- /dev/null
+++ b/testdata/golden.md
@@ -0,0 +1,36 @@
+# Simple Test
+
+This is a test markdown file for md-code-lite.
+
+## main.c
+
+```c
+#include <stdio.h>
+
+int main() {
+  printf("Hello, World!\n");
+  return 0;
+}
+```
+
+## helper.js
+
+```javascript
+function add(a, b) {
+  return a + b;
+}
+
+module.exports = { add };
+```
+
+```css
+body {
+  margin: 0;
+  font-family: Arial, sans-serif;
+}
+
+.container {
+  max-width: 1200px;
+  margin: 0 auto;
+}
+```