logging.go

package middlewares

// Borrowed from https://gist.github.com/elithrar/887d162dfd0c539b700ab4049c76e22b
// Alternatively, we could use https://github.com/samber/slog-chi, however, it pulls in another bunch of dependencies and log messages are more verbose and feel almost little bloated

import (
	"io"
	"net/http"
	"strings"
	"time"
)

type logFunc func(string, ...interface{})

type LoggingMiddleware struct {
	handler         http.Handler
	logFunc         logFunc
	excludePrefixes []string
}

func NewLoggingMiddleware(logFunc logFunc, excludePrefixes []string) func(http.Handler) http.Handler {
	return func(h http.Handler) http.Handler {
		return &LoggingMiddleware{
			handler:         h,
			logFunc:         logFunc,
			excludePrefixes: excludePrefixes,
		}
	}
}

func (lg *LoggingMiddleware) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	ww := wrapWriter(w)

	start := time.Now()
	lg.handler.ServeHTTP(ww, r)
	end := time.Now()
	duration := end.Sub(start)

	path := strings.ToLower(r.URL.Path)
	for _, prefix := range lg.excludePrefixes {
		if strings.HasPrefix(path, prefix) {
			return
		}
	}

	lg.logFunc("[request]",
		"status", ww.Status(),
		"method", r.Method,
		"uri", r.URL.String(),
		"duration", duration,
		"bytes", ww.BytesWritten(),
		"addr", readUserIP(r),
		"user", readUserID(r),
	)
}

func readUserIP(r *http.Request) string {
	ip := r.Header.Get("X-Real-Ip")
	if ip == "" {
		ip = r.Header.Get("X-Forwarded-For")
	}
	if ip == "" {
		ip = r.RemoteAddr
	}
	return ip
}

func readUserID(r *http.Request) string {
	if user := GetPrincipal(r); user != nil {
		return user.ID
	}
	return "-"
}

// The below writer-wrapping code has been lifted from
// https://github.com/zenazn/goji/blob/master/web/middleware/logger.go - because
// it does exactly what is needed, and it's unlikely to change in any
// significant way that makes copying worse-off than importing. MIT licensed
// and (c) Carl Jackson.

// writerProxy is a proxy around an http.ResponseWriter that allows you to hook
// into various parts of the response process.
type writerProxy interface {
	http.ResponseWriter
	// Status returns the HTTP status of the request, or 0 if one has not
	// yet been sent.
	Status() int
	// BytesWritten returns the total number of bytes sent to the client.
	BytesWritten() int
	// Tee causes the response body to be written to the given io.Writer in
	// addition to proxying the writes through. Only one io.Writer can be
	// tee'd to at once: setting a second one will overwrite the first.
	// Writes will be sent to the proxy before being written to this
	// io.Writer. It is illegal for the tee'd writer to be modified
	// concurrently with writes.
	Tee(io.Writer)
	// Unwrap returns the original proxied target.
	Unwrap() http.ResponseWriter
}

// wrapWriter wraps an http.ResponseWriter, returning a proxy that allows you to
// hook into various parts of the response process.
func wrapWriter(w http.ResponseWriter) writerProxy {
	return &basicWriter{ResponseWriter: w}
}

// basicWriter wraps a http.ResponseWriter that implements the minimal
// http.ResponseWriter interface.
type basicWriter struct {
	http.ResponseWriter
	wroteHeader bool
	code        int
	bytes       int
	tee         io.Writer
}

func (b *basicWriter) WriteHeader(code int) {
	if !b.wroteHeader {
		b.code = code
		b.wroteHeader = true
		b.ResponseWriter.WriteHeader(code)
	}
}
func (b *basicWriter) Write(buf []byte) (int, error) {
	b.WriteHeader(http.StatusOK)
	n, err := b.ResponseWriter.Write(buf)
	if b.tee != nil {
		_, err2 := b.tee.Write(buf[:n])
		// Prefer errors generated by the proxied writer.
		if err == nil {
			err = err2
		}
	}
	b.bytes += n
	return n, err
}
func (b *basicWriter) maybeWriteHeader() {
	if !b.wroteHeader {
		b.WriteHeader(http.StatusOK)
	}
}
func (b *basicWriter) Status() int {
	return b.code
}
func (b *basicWriter) BytesWritten() int {
	return b.bytes
}
func (b *basicWriter) Tee(w io.Writer) {
	b.tee = w
}
func (b *basicWriter) Unwrap() http.ResponseWriter {
	return b.ResponseWriter
}