headers

var (
	// Monoid is a Monoid for combining http.Header maps.
	// It uses a union operation where values from both headers are preserved.
	// When the same header exists in both maps, the values are concatenated.
	//
	// Example:
	//   h1 := make(http.Header)
	//   h1.Set("X-Custom", "value1")
	//
	//   h2 := make(http.Header)
	//   h2.Set("Authorization", "Bearer token")
	//
	//   combined := Monoid.Concat(h1, h2)
	//   // combined contains both X-Custom and Authorization headers
	Monoid = RG.UnionMonoid[http.Header](A.Semigroup[string]())

	// AtValues is a Lens that focuses on all values of a specific header.
	// It returns a lens that accesses the []string slice of header values.
	// The header name is automatically canonicalized using MIME header key rules.
	//
	// Parameters:
	//   - name: The header name (will be canonicalized)
	//
	// Returns:
	//   - A Lens[http.Header, []string] focusing on the header's values
	//
	// Example:
	//   lens := AtValues("Content-Type")
	//   values := lens.Get(headers) // Returns []string
	//   newHeaders := lens.Set([]string{"application/json"})(headers)
	AtValues = F.Flow2(
		textproto.CanonicalMIMEHeaderKey,
		LRG.AtRecord[http.Header, []string],
	)

	// AtValue is a Lens that focuses on the first value of a specific header.
	// It returns a lens that accesses an Option[string] representing the first
	// header value, or None if the header doesn't exist.
	// The header name is automatically canonicalized using MIME header key rules.
	//
	// Parameters:
	//   - name: The header name (will be canonicalized)
	//
	// Returns:
	//   - A Lens[http.Header, Option[string]] focusing on the first header value
	//
	// Example:
	//   lens := AtValue("Authorization")
	//   token := lens.Get(headers) // Returns Option[string]
	//
	//   // Set a header value
	//   newHeaders := lens.Set(O.Some("Bearer token"))(headers)
	//
	//   // Remove a header
	//   newHeaders := lens.Set(O.None[string]())(headers)
	AtValue = F.Flow2(
		AtValues,
		composeHead,
	)
)