Go URL filter query parsing

main.go

package main

import (
	"fmt"
	"net/http"
	"net/url"
)

func main() {
	// Simulate a URL with filter parameters
	rawURL := "http://example.com/whatever?filter[certificate_authority]=certainly&filter[state]=pending&limit=10"

	// Parse the URL
	parsedURL, err := url.Parse(rawURL)
	if err != nil {
		fmt.Println("Error parsing URL:", err)
		return
	}

	// Get query parameters
	query := parsedURL.Query()

	// Direct access with bracket notation
	certAuthority := query.Get("filter[certificate_authority]")
	state := query.Get("filter[state]")
	limit := query.Get("limit")

	// Display results
	fmt.Println("=== Parsed Query Parameters ===")
	fmt.Printf("Certificate Authority: %q\n", certAuthority)
	fmt.Printf("State: %q\n", state)
	fmt.Printf("Limit: %q\n", limit)

	// Show all query parameters
	fmt.Println("\n=== All Query Parameters ===")
	for key, values := range query {
		fmt.Printf("%s = %v\n", key, values)
	}

	// Example: Build a handler function
	fmt.Println("\n=== Using in HTTP Handler ===")
	simulateHandler(parsedURL.Query())
}

// Simulate an HTTP handler
func simulateHandler(query url.Values) {
	certAuthority := query.Get("filter[certificate_authority]")
	state := query.Get("filter[state]")

	if certAuthority == "" && state == "" {
		fmt.Println("No filters provided")
		return
	}

	fmt.Println("Processing filters:")
	if certAuthority != "" {
		fmt.Printf("  - Certificate Authority: %s\n", certAuthority)
	}
	if state != "" {
		fmt.Printf("  - State: %s\n", state)
	}
}

// Bonus: Example with actual http.Request
func exampleHTTPHandler(w http.ResponseWriter, r *http.Request) {
	query := r.URL.Query()

	certAuthority := query.Get("filter[certificate_authority]")
	state := query.Get("filter[state]")

	fmt.Fprintf(w, "Certificate Authority: %s\n", certAuthority)
	fmt.Fprintf(w, "State: %s\n", state)
}