package oauthserver

import (
	"context"
	"net/http"

	"github.com/grafana/grafana/pkg/services/accesscontrol"
	"gopkg.in/square/go-jose.v2"
)

const (
	// TmpOrgID is the orgID we use while global service accounts are not supported.
	TmpOrgID int64 = 1
	// NoServiceAccountID is the ID we use for client that have no service account associated.
	NoServiceAccountID int64 = 0

	// List of scopes used to identify the impersonated user.
	ScopeUsersSelf       = "users:self"
	ScopeGlobalUsersSelf = "global.users:self"
	ScopeTeamsSelf       = "teams:self"

	// Supported encryptions
	RS256 = "RS256"
	ES256 = "ES256"
)

// OAuth2Server represents a service in charge of managing OAuth2 clients
// and handling OAuth2 requests (token, introspection).
type OAuth2Server interface {
	// SaveExternalService creates or updates an external service in the database, it generates client_id and secrets and
	// it ensures that the associated service account has the correct permissions.
	SaveExternalService(ctx context.Context, cmd *ExternalServiceRegistration) (*ExternalServiceDTO, error)
	// GetExternalService retrieves an external service from store by client_id. It populates the SelfPermissions and
	// SignedInUser from the associated service account.
	GetExternalService(ctx context.Context, id string) (*ExternalService, error)

	// HandleTokenRequest handles the client's OAuth2 query to obtain an access_token by presenting its authorization
	// grant (ex: client_credentials, jwtbearer).
	HandleTokenRequest(rw http.ResponseWriter, req *http.Request)
	// HandleIntrospectionRequest handles the OAuth2 query to determine the active state of an OAuth 2.0 token and
	// to determine meta-information about this token.
	HandleIntrospectionRequest(rw http.ResponseWriter, req *http.Request)
}

//go:generate mockery --name Store --structname MockStore --outpkg oauthtest --filename store_mock.go --output ./oauthtest/

type Store interface {
	RegisterExternalService(ctx context.Context, client *ExternalService) error
	SaveExternalService(ctx context.Context, client *ExternalService) error
	GetExternalService(ctx context.Context, id string) (*ExternalService, error)
	GetExternalServiceByName(ctx context.Context, name string) (*ExternalService, error)
	GetExternalServicePublicKey(ctx context.Context, clientID string) (*jose.JSONWebKey, error)
}

type KeyOption struct {
	// URL       string `json:"url,omitempty"` // TODO allow specifying a URL (to a .jwks file) to fetch the key from
	// PublicPEM contains the Base64 encoded public key in PEM format
	PublicPEM string `json:"public_pem,omitempty"`
	Generate  bool   `json:"generate,omitempty"`
}

type SelfCfg struct {
	// Enabled allows the service to request access tokens for itself using the client_credentials grant
	Enabled bool `json:"enabled"`
	// Permissions are the permissions that the external service needs its associated service account to have.
	Permissions []accesscontrol.Permission `json:"permissions,omitempty"`
}
type ImpersonationCfg struct {
	// Enabled allows the service to request access tokens to impersonate users using the jwtbearer grant
	Enabled bool `json:"enabled"`
	// Groups allows the service to list the impersonated user's teams
	Groups bool `json:"groups"`
	// Permissions are the permissions that the external service needs when impersonating a user.
	// The intersection of this set with the impersonated user's permission guarantees that the client will not
	// gain more privileges than the impersonated user has.
	Permissions []accesscontrol.Permission `json:"permissions,omitempty"`
}

// ExternalServiceRegistration represents the registration form to save new OAuth2 client.
type ExternalServiceRegistration struct {
	Name string `json:"name"`
	// RedirectURI is the URI that is used in the code flow.
	// Note that this is not used yet.
	RedirectURI *string `json:"redirectUri,omitempty"`
	// Impersonation access configuration
	Impersonation ImpersonationCfg `json:"impersonation"`
	// Self access configuration
	Self SelfCfg `json:"self"`
	// Key is the option to specify a public key or ask the server to generate a crypto key pair.
	Key *KeyOption `json:"key,omitempty"`
}