Add markdown response body formatter

README.md

@@ -6,7 +6,7 @@ A modern HTTP(S) client for the command line.
 
 ## Features
 
-- **Response formatting** - Automatic formatting and syntax highlighting for JSON, XML, YAML, HTML, CSS, CSV, MessagePack, Protocol Buffers, and more
+- **Response formatting** - Automatic formatting and syntax highlighting for JSON, XML, YAML, HTML, CSS, CSV, Markdown, MessagePack, Protocol Buffers, and more
 - **Image rendering** - Display images directly in your terminal
 - **WebSocket support** - Bidirectional WebSocket connections with automatic JSON formatting
 - **gRPC support** - Make gRPC calls with automatic JSON-to-protobuf conversion

docs/output-formatting.md

@@ -137,6 +137,20 @@ Features:
 fetch example.com/styles.css
 ```
 
+### Markdown
+
+**Content-Types**: `text/markdown`, `text/x-markdown`
+
+Features:
+
+- Syntax highlighting for headings, bold, italic, code spans, links, images
+- Fenced code block delegation to JSON, YAML, XML, HTML, CSS formatters
+- Blockquote and list marker highlighting
+
+```sh
+fetch example.com/README.md
+```
+
 ### CSV
 
 **Content-Types**: `text/csv`, `application/csv`

go.mod

@@ -9,6 +9,7 @@ require (
 	github.com/mattn/go-runewidth v0.0.19
 	github.com/quic-go/quic-go v0.59.0
 	github.com/tinylib/msgp v1.6.3
+	github.com/yuin/goldmark v1.7.16
 	golang.org/x/crypto v0.48.0
 	golang.org/x/image v0.36.0
 	golang.org/x/net v0.50.0

go.sum

@@ -24,6 +24,8 @@ github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 github.com/tinylib/msgp v1.6.3 h1:bCSxiTz386UTgyT1i0MSCvdbWjVW+8sG3PjkGsZQt4s=
 github.com/tinylib/msgp v1.6.3/go.mod h1:RSp0LW9oSxFut3KzESt5Voq4GVWyS+PSulT77roAqEA=
+github.com/yuin/goldmark v1.7.16 h1:n+CJdUxaFMiDUNnWC3dMWCIQJSkxH4uz3ZwQBkAlVNE=
+github.com/yuin/goldmark v1.7.16/go.mod h1:ip/1k0VRfGynBgxOz0yCqHrbZXhcjxyuS66Brc7iBKg=
 go.uber.org/mock v0.5.2 h1:LbtPTcP8A5k9WPXj54PPPbjcI4Y6lhyOZXn+VS7wNko=
 go.uber.org/mock v0.5.2/go.mod h1:wLlUxC2vVTPTaE3UD51E0BGOAElKrILxhVSDYQLld5o=
 golang.org/x/crypto v0.48.0 h1:/VRzVqiRSggnhY7gNRxPauEQ5Drw9haKdM0jqfcCFts=

internal/core/printer.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"io"
 	"os"
+	"sync"
 )
 
 // Sequence represents an ANSI escape sequence.
@@ -61,7 +62,7 @@ func (h *Handle) Stdout() *Printer {
 // Printer allows for writing data with optional ANSI escape sequences based on
 // the color settings for a target.
 type Printer struct {
-	file     *os.File
+	file     io.Writer
 	buf      bytes.Buffer
 	useColor bool
 }
@@ -81,6 +82,25 @@ func newPrinter(file *os.File, isTerm bool, c Color) *Printer {
 	return &Printer{file: file, useColor: useColor}
 }
 
+// TestPrinter returns a Printer suitable for testing. All output, including
+// flushed data, is captured and accessible via Bytes.
+func TestPrinter(useColor bool) *Printer {
+	return &Printer{file: &lockedBuffer{}, useColor: useColor}
+}
+
+// lockedBuffer is a goroutine-safe bytes.Buffer used as the flush target in
+// test printers so that Bytes can return the combined buffered + flushed data.
+type lockedBuffer struct {
+	mu  sync.Mutex
+	buf bytes.Buffer
+}
+
+func (lb *lockedBuffer) Write(p []byte) (int, error) {
+	lb.mu.Lock()
+	defer lb.mu.Unlock()
+	return lb.buf.Write(p)
+}
+
 // Set writes the provided Sequence.
 func (p *Printer) Set(s Sequence) {
 	if p.useColor {
@@ -108,8 +128,17 @@ func (p *Printer) Discard() {
 	p.buf.Reset()
 }
 
-// Bytes returns the current contents of the buffer.
+// Bytes returns the current contents of the buffer. For test printers created
+// with TestPrinter, this also includes previously flushed data.
 func (p *Printer) Bytes() []byte {
+	if lb, ok := p.file.(*lockedBuffer); ok {
+		lb.mu.Lock()
+		flushed := lb.buf.Bytes()
+		lb.mu.Unlock()
+		if len(flushed) > 0 {
+			return append(flushed, p.buf.Bytes()...)
+		}
+	}
 	return p.buf.Bytes()
 }
 

internal/format/contenttype.go

@@ -18,6 +18,7 @@ const (
 	TypeHTML
 	TypeImage
 	TypeJSON
+	TypeMarkdown
 	TypeMsgPack
 	TypeNDJSON
 	TypeProtobuf
@@ -82,6 +83,8 @@ func GetContentType(headers http.Header) (ContentType, string) {
 				return TypeCSV, charset
 			case "html":
 				return TypeHTML, charset
+			case "markdown", "x-markdown":
+				return TypeMarkdown, charset
 			case "event-stream":
 				return TypeSSE, charset
 			case "xml":