package config

import (
	"errors"
	"fmt"
	"net/url"
	"strings"
)

// OIDC is sign-in through an identity provider: Keycloak, Entra ID, Google,
// Okta, Authentik — anything that speaks OpenID Connect.
//
//	auth:
//	  oidc:
//	    issuer: https://login.example.com/realms/acme
//	    client_id: llmgw
//	    client_secret_file: /etc/llmgw/secrets/oidc-client-secret
//	    label: Acme SSO
//	    create_accounts: true
//	    roles: {admin: [llmgw-admins], operator: [llmgw-ops]}
//	    memberships: {ml-team: "team:Acme/ml"}
type OIDC struct {
	// Issuer is the provider's address; its /.well-known/openid-configuration
	// says the rest.
	Issuer string `koanf:"issuer"`
	// ClientID and the file holding its secret, as registered with the
	// provider.
	ClientID         string `koanf:"client_id"`
	ClientSecretFile string `koanf:"client_secret_file"`
	// RedirectURL is where the provider sends people back:
	// https://<gateway>/login/oidc/callback. Empty works it out from the
	// request, which is right unless a proxy changes the address.
	RedirectURL string `koanf:"redirect_url"`
	// Label is what the sign-in button says: "Sign in with <label>".
	Label string `koanf:"label"`
	// Scopes asked for besides openid; empty is email and profile, and
	// groups when Roles or Memberships use them.
	Scopes []string `koanf:"scopes"`
	// GroupsClaim names the ID token claim holding groups; empty is
	// "groups".
	GroupsClaim string `koanf:"groups_claim"`
	// CreateAccounts makes an account, active, for a person the provider
	// vouches for and the gateway does not know. Off, only existing accounts
	// sign in this way.
	CreateAccounts bool `koanf:"create_accounts"`
	// Roles maps a staff role (viewer, operator, billing, admin) to the
	// groups that give it. Set at every sign-in: someone taken out of the
	// group loses the role the next time.
	Roles map[string][]string `koanf:"roles"`
	// Memberships maps a group to a place in the tree — org:NAME,
	// team:ORG/TEAM, project:ORG/TEAM/PROJECT — joined at sign-in.
	Memberships map[string]string `koanf:"memberships"`
	// PasswordSignIn off refuses passwords on the sign-in form: people come
	// in through the provider only. Administrators still can, so a broken
	// provider does not lock everybody out.
	NoPasswords bool `koanf:"no_passwords"`
}

// Enabled reports whether OIDC sign-in is configured.
func (o OIDC) Enabled() bool { return o.Issuer != "" }

// Validate checks the settings before a provider is asked anything.
func (o OIDC) Validate() error {
	if !o.Enabled() {
		return nil
	}
	u, err := url.Parse(o.Issuer)
	if err != nil || u.Scheme != "https" && !(u.Scheme == "http" && (u.Hostname() == "localhost" || u.Hostname() == "127.0.0.1")) {
		return fmt.Errorf("auth.oidc.issuer %q: an https address", o.Issuer)
	}
	if o.ClientID == "" {
		return errors.New("auth.oidc.client_id is required")
	}
	for role := range o.Roles {
		switch role {
		case "viewer", "operator", "billing", "admin":
		default:
			return fmt.Errorf("auth.oidc.roles: %q is not viewer, operator, billing or admin", role)
		}
	}
	for g, where := range o.Memberships {
		kind, path, ok := strings.Cut(where, ":")
		if !ok || path == "" || (kind != "org" && kind != "team" && kind != "project") {
			return fmt.Errorf("auth.oidc.memberships.%s is %q: org:NAME, team:ORG/TEAM or project:ORG/TEAM/PROJECT", g, where)
		}
	}
	return nil
}

// SCIM lets an identity provider provision accounts (/scim/v2): made,
// suspended and reinstated as they are there, with groups mapped by
// auth.oidc's roles and memberships.
type SCIM struct {
	// TokenFile holds the bearer token the provider sends. Empty turns
	// provisioning off.
	TokenFile string `koanf:"token_file"`
}