backend-service/internal/middleware/logging.go

package middleware

import (
	"attune-heart-therapy/internal/logger"
	"fmt"
	"time"

	"github.com/gin-gonic/gin"
)

// LoggingMiddleware creates a custom logging middleware with detailed request information
func LoggingMiddleware() gin.HandlerFunc {
	return gin.LoggerWithFormatter(func(param gin.LogFormatterParams) string {
		// Custom log format with more details
		return fmt.Sprintf("[%s] %s %s %s %d %s \"%s\" %s \"%s\" %s\n",
			param.TimeStamp.Format("2006-01-02 15:04:05"),
			param.ClientIP,
			param.Method,
			param.Path,
			param.StatusCode,
			param.Latency,
			param.Request.UserAgent(),
			param.ErrorMessage,
			param.Request.Referer(),
			formatBodySize(param.BodySize),
		)
	})
}

// StructuredLoggingMiddleware creates a structured logging middleware for better log parsing
func StructuredLoggingMiddleware() gin.HandlerFunc {
	log := logger.New("http")

	return func(c *gin.Context) {
		// Start timer
		start := time.Now()
		path := c.Request.URL.Path
		raw := c.Request.URL.RawQuery

		// Process request
		c.Next()

		// Calculate latency
		latency := time.Since(start)

		// Build full path with query string
		if raw != "" {
			path = path + "?" + raw
		}

		// Prepare log fields
		fields := map[string]interface{}{
			"method":     c.Request.Method,
			"path":       path,
			"status":     c.Writer.Status(),
			"latency_ms": latency.Milliseconds(),
			"client_ip":  c.ClientIP(),
			"body_size":  c.Writer.Size(),
			"user_agent": c.Request.UserAgent(),
		}

		// Add trace ID if available
		if traceID, exists := c.Get("trace_id"); exists {
			fields["trace_id"] = traceID
		}

		// Add user ID if available
		if userID, exists := c.Get("user_id"); exists {
			fields["user_id"] = userID
		}

		// Log based on status code
		statusCode := c.Writer.Status()

		if statusCode >= 500 {
			log.Error("HTTP request completed with server error", nil, fields)
		} else if statusCode >= 400 {
			log.Warn("HTTP request completed with client error", fields)
		} else {
			log.Info("HTTP request completed successfully", fields)
		}

		// Log errors if any
		if len(c.Errors) > 0 {
			errorFields := map[string]interface{}{
				"method":    c.Request.Method,
				"path":      path,
				"client_ip": c.ClientIP(),
				"errors":    c.Errors.String(),
			}
			log.Error("Request completed with errors", c.Errors.Last().Err, errorFields)
		}
	}
}

// formatBodySize formats body size in human readable format
func formatBodySize(size int) string {
	if size == 0 {
		return "0B"
	}

	const unit = 1024
	if size < unit {
		return fmt.Sprintf("%dB", size)
	}

	div, exp := int64(unit), 0
	for n := size / unit; n >= unit; n /= unit {
		div *= unit
		exp++
	}

	return fmt.Sprintf("%.1f%cB", float64(size)/float64(div), "KMGTPE"[exp])
}