upstream

type AuthorizationOption func(*authorizationOptions)

type BaseOAuth2Provider struct {
	// contains filtered or unexported fields
}

type CommonOAuthConfig struct {
	// ClientID is the OAuth client ID registered with the upstream IDP.
	ClientID string

	// ClientSecret is the OAuth client secret registered with the upstream IDP.
	// Optional for public clients (RFC 6749 Section 2.1) which authenticate using
	// PKCE instead of a client secret. Required for confidential clients.
	ClientSecret string

	// Scopes are the OAuth scopes to request from the upstream IDP.
	Scopes []string

	// RedirectURI is the callback URL where the upstream IDP will redirect
	// after authentication.
	RedirectURI string
}

type IDTokenClaims struct {
	// Issuer is the issuer identifier (iss claim).
	Issuer string

	// Subject is the subject identifier (sub claim).
	Subject string

	// Audience contains the audience(s) this ID Token is intended for (aud claim).
	Audience []string

	// ExpiresAt is the expiration time (exp claim).
	ExpiresAt time.Time

	// IssuedAt is the time at which the ID Token was issued (iat claim).
	IssuedAt time.Time

	// Nonce is the value used to associate a client session with an ID Token (nonce claim).
	Nonce string

	// AuthTime is the time when the end-user authentication occurred (auth_time claim).
	AuthTime time.Time

	// AuthorizedParty is the party to which the ID Token was issued (azp claim).
	AuthorizedParty string

	// Email is the user's email address.
	Email string

	// EmailVerified indicates whether the user's email has been verified.
	EmailVerified bool

	// Name is the user's full name.
	Name string

	// RawClaims contains all claims from the ID Token payload.
	RawClaims map[string]any
}

type OAuth2Config struct {
	CommonOAuthConfig

	// AuthorizationEndpoint is the URL for the OAuth authorization endpoint.
	AuthorizationEndpoint string

	// TokenEndpoint is the URL for the OAuth token endpoint.
	TokenEndpoint string

	// UserInfo contains configuration for fetching user information (optional).
	// When nil, the provider does not support UserInfo fetching.
	UserInfo *UserInfoConfig
}

type OAuth2Provider interface {
	// Type returns the provider type.
	Type() ProviderType

	// AuthorizationURL builds the URL to redirect the user to the upstream IDP.
	// state: our internal state to correlate callback
	// codeChallenge: PKCE challenge to send to upstream (if supported)
	// opts: optional configuration such as nonce or additional parameters
	AuthorizationURL(state, codeChallenge string, opts ...AuthorizationOption) (string, error)

	// ExchangeCode exchanges an authorization code for tokens with the upstream IDP.
	ExchangeCode(ctx context.Context, code, codeVerifier string) (*Tokens, error)

	// RefreshTokens refreshes the upstream IDP tokens.
	RefreshTokens(ctx context.Context, refreshToken string) (*Tokens, error)

	// ResolveIdentity validates tokens and returns the canonical subject.
	// For OIDC providers with ID tokens, it validates the token and nonce.
	// For OAuth2 providers or as fallback, it fetches UserInfo.
	ResolveIdentity(ctx context.Context, tokens *Tokens, nonce string) (subject string, err error)

	// FetchUserInfo retrieves user information using the provided access token.
	// Returns an error if the provider is not configured for UserInfo fetching.
	FetchUserInfo(ctx context.Context, accessToken string) (*UserInfo, error)
}

type OAuth2ProviderOption func(*BaseOAuth2Provider)

type OIDCEndpoints struct {
	// Issuer is the issuer identifier.
	Issuer string `json:"issuer"`

	// AuthorizationEndpoint is the URL for the authorization endpoint.
	AuthorizationEndpoint string `json:"authorization_endpoint"`

	// TokenEndpoint is the URL for the token endpoint.
	TokenEndpoint string `json:"token_endpoint"`

	// UserInfoEndpoint is the URL for the userinfo endpoint.
	UserInfoEndpoint string `json:"userinfo_endpoint,omitempty"`

	// JWKSEndpoint is the URL for the JWKS endpoint.
	JWKSEndpoint string `json:"jwks_uri,omitempty"`

	// CodeChallengeMethodsSupported lists the supported PKCE code challenge methods.
	CodeChallengeMethodsSupported []string `json:"code_challenge_methods_supported,omitempty"`
}

type ProviderType string

type Tokens struct {
	// AccessToken is the access token from the upstream IDP.
	AccessToken string

	// RefreshToken is the refresh token from the upstream IDP (if provided).
	RefreshToken string

	// IDToken is the ID token from the upstream IDP (for OIDC).
	IDToken string

	// ExpiresAt is when the access token expires.
	ExpiresAt time.Time
}

type UserInfo struct {
	// Subject is the unique identifier for the user (sub claim).
	Subject string `json:"sub"`

	// Email is the user's email address.
	Email string `json:"email,omitempty"`

	// Name is the user's full name.
	Name string `json:"name,omitempty"`

	// Claims contains all claims returned by the userinfo endpoint.
	Claims map[string]any `json:"-"`
}

type UserInfoConfig struct {
	// EndpointURL is the URL of the userinfo endpoint (required).
	EndpointURL string

	// HTTPMethod is the HTTP method to use (default: GET).
	HTTPMethod string

	// AdditionalHeaders contains extra headers to include in the request.
	AdditionalHeaders map[string]string

	// FieldMapping contains custom field mapping configuration.
	// If nil, standard OIDC field names are used ("sub", "name", "email").
	FieldMapping *UserInfoFieldMapping
}

type UserInfoFieldMapping struct {
	// SubjectField is the field name for the user ID (e.g., "sub" for OIDC, "id" for GitHub).
	// Default: "sub"
	SubjectField string
}