auth/internal/metadata/delivery/http/metadata_http.go

package http

import (
	"encoding/json"
	"fmt"
	"net/http"

	"source.toby3d.me/toby3d/auth/internal/common"
	"source.toby3d.me/toby3d/auth/internal/domain"
)

type (

	//nolint:tagliatelle // https://indieauth.net/source/#indieauth-server-metadata
	Response struct {
		// URL of a page containing human-readable information that
		// developers might need to know when using the server.
		ServiceDocumentation string `json:"service_documentation,omitempty"`

		// The Authorization Endpoint.
		AuthorizationEndpoint string `json:"authorization_endpoint"`

		// The Token Endpoint.
		TokenEndpoint string `json:"token_endpoint"`

		// The Introspection Endpoint.
		IntrospectionEndpoint string `json:"introspection_endpoint"`

		// The User Info Endpoint.
		UserinfoEndpoint string `json:"userinfo_endpoint,omitempty"`

		// The Revocation Endpoint.
		RevocationEndpoint string `json:"revocation_endpoint,omitempty"`

		// The server's issuer identifier.
		Issuer string `json:"issuer"`

		// JSON array containing the value "none".
		RevocationEndpointAuthMethodsSupported []string `json:"revocation_endpoint_auth_methods_supported,omitempty"` //nolint:lll

		// JSON array containing the response_type values supported.
		ResponseTypesSupported []string `json:"response_types_supported,omitempty"`

		// JSON array containing grant type values supported.
		GrantTypesSupported []string `json:"grant_types_supported,omitempty"`

		// JSON array containing scope values supported by the
		// IndieAuth server.
		ScopesSupported []string `json:"scopes_supported,omitempty"`

		// JSON array containing the methods supported for PKCE.
		CodeChallengeMethodsSupported []string `json:"code_challenge_methods_supported"`

		// JSON array containing a list of client authentication methods
		// supported by this introspection endpoint.
		IntrospectionEndpointAuthMethodsSupported []string `json:"introspection_endpoint_auth_methods_supported,omitempty"` //nolint:lll

		// Boolean parameter indicating whether the authorization server
		// provides the iss parameter.
		AuthorizationResponseIssParameterSupported bool `json:"authorization_response_iss_parameter_supported,omitempty"` //nolint:lll
	}

	Handler struct {
		metadata *domain.Metadata
	}
)

func NewHandler(metadata *domain.Metadata) *Handler {
	return &Handler{metadata: metadata}
}

func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if r.Method != "" && r.Method != http.MethodGet {
		http.Error(w, http.StatusText(http.StatusMethodNotAllowed), http.StatusMethodNotAllowed)

		return
	}

	w.Header().Set(common.HeaderContentType, common.MIMEApplicationJSONCharsetUTF8)
	_ = json.NewEncoder(w).Encode(NewResponse(h.metadata))
}

func NewResponse(src *domain.Metadata) *Response {
	out := &Response{
		AuthorizationEndpoint:                      "",
		AuthorizationResponseIssParameterSupported: src.AuthorizationResponseIssParameterSupported,
		CodeChallengeMethodsSupported:              make([]string, 0),
		GrantTypesSupported:                        make([]string, 0),
		IntrospectionEndpoint:                      "",
		IntrospectionEndpointAuthMethodsSupported:  make([]string, 0),
		Issuer:                                 "",
		ResponseTypesSupported:                 make([]string, 0),
		RevocationEndpoint:                     "",
		RevocationEndpointAuthMethodsSupported: make([]string, 0),
		ScopesSupported:                        make([]string, 0),
		ServiceDocumentation:                   "",
		TokenEndpoint:                          "",
		UserinfoEndpoint:                       "",
	}

	for i := range src.ScopesSupported {
		out.ScopesSupported = append(out.ScopesSupported, src.ScopesSupported[i].String())
	}

	for i := range src.ResponseTypesSupported {
		out.ResponseTypesSupported = append(out.ResponseTypesSupported, src.ResponseTypesSupported[i].String())
	}

	for i := range src.GrantTypesSupported {
		out.GrantTypesSupported = append(out.GrantTypesSupported, src.GrantTypesSupported[i].String())
	}

	for i := range src.CodeChallengeMethodsSupported {
		out.CodeChallengeMethodsSupported = append(out.CodeChallengeMethodsSupported,
			src.CodeChallengeMethodsSupported[i].String())
	}

	out.IntrospectionEndpointAuthMethodsSupported = append(out.IntrospectionEndpointAuthMethodsSupported,
		src.IntrospectionEndpointAuthMethodsSupported...)

	// NOTE(toby3d) = If a revocation endpoint is provided, this property
	// should also be provided with the value ["none"], since the omission
	// of this value defaults to client_secret_basic according to RFC8414.
	out.RevocationEndpointAuthMethodsSupported = append(out.RevocationEndpointAuthMethodsSupported,
		src.RevocationEndpointAuthMethodsSupported...)

	for dst, src := range map[*string]fmt.Stringer{
		&out.AuthorizationEndpoint: src.AuthorizationEndpoint,
		&out.IntrospectionEndpoint: src.IntrospectionEndpoint,
		&out.Issuer:                src.Issuer,
		&out.RevocationEndpoint:    src.RevocationEndpoint,
		&out.ServiceDocumentation:  src.ServiceDocumentation,
		&out.TokenEndpoint:         src.TokenEndpoint,
		&out.UserinfoEndpoint:      src.UserinfoEndpoint,
	} {
		if src == nil {
			continue
		}

		*dst = src.String()
	}

	return out
}