package server

import (
	"context"
	"fmt"
	"log"
	"net"
	"net/http"
	"reflect"
	"strings"
	"time"

	"forge.cadoles.com/Cadoles/emissary/internal/auth"
	"forge.cadoles.com/Cadoles/emissary/internal/auth/agent"
	"forge.cadoles.com/Cadoles/emissary/internal/auth/thirdparty"
	"forge.cadoles.com/Cadoles/emissary/internal/config"
	"forge.cadoles.com/Cadoles/emissary/internal/datastore"
	"forge.cadoles.com/Cadoles/emissary/internal/jwk"
	"github.com/antonmedv/expr"
	"github.com/antonmedv/expr/vm"
	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
	"github.com/go-chi/cors"
	"github.com/lestrrat-go/jwx/v2/jwa"
	"github.com/lestrrat-go/jwx/v2/jwt"
	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"
)

type Server struct {
	conf      config.ServerConfig
	agentRepo datastore.AgentRepository
}

func (s *Server) Start(ctx context.Context) (<-chan net.Addr, <-chan error) {
	errs := make(chan error)
	addrs := make(chan net.Addr)

	go s.run(ctx, addrs, errs)

	return addrs, errs
}

func (s *Server) run(parentCtx context.Context, addrs chan net.Addr, errs chan error) {
	defer func() {
		close(errs)
		close(addrs)
	}()

	ctx, cancel := context.WithCancel(parentCtx)
	defer cancel()

	if err := s.initRepositories(ctx); err != nil {
		errs <- errors.WithStack(err)

		return
	}

	listener, err := net.Listen("tcp", fmt.Sprintf("%s:%d", s.conf.HTTP.Host, s.conf.HTTP.Port))
	if err != nil {
		errs <- errors.WithStack(err)

		return
	}

	addrs <- listener.Addr()

	defer func() {
		if err := listener.Close(); err != nil && !errors.Is(err, net.ErrClosed) {
			errs <- errors.WithStack(err)
		}
	}()

	go func() {
		<-ctx.Done()

		if err := listener.Close(); err != nil && !errors.Is(err, net.ErrClosed) {
			log.Printf("%+v", errors.WithStack(err))
		}
	}()

	router := chi.NewRouter()

	router.Use(middleware.Logger)

	corsMiddleware := cors.New(cors.Options{
		AllowedOrigins:   s.conf.CORS.AllowedOrigins,
		AllowedMethods:   s.conf.CORS.AllowedMethods,
		AllowCredentials: bool(s.conf.CORS.AllowCredentials),
		AllowedHeaders:   s.conf.CORS.AllowedHeaders,
		Debug:            bool(s.conf.CORS.Debug),
	})

	router.Use(corsMiddleware.Handler)

	thirdPartyAuth, err := s.getThirdPartyAuthenticator()
	if err != nil {
		errs <- errors.WithStack(err)

		return
	}

	router.Route("/api/v1", func(r chi.Router) {
		r.Post("/register", s.registerAgent)

		r.Group(func(r chi.Router) {
			r.Use(auth.Middleware(
				thirdPartyAuth,
				agent.NewAuthenticator(s.agentRepo, agent.DefaultAcceptableSkew),
			))

			r.Route("/agents", func(r chi.Router) {
				r.With(assertGlobalReadAccess).Get("/", s.queryAgents)
				r.With(assertAgentReadAccess).Get("/{agentID}", s.getAgent)
				r.With(assertAgentWriteAccess).Put("/{agentID}", s.updateAgent)
				r.With(assertAgentWriteAccess).Delete("/{agentID}", s.deleteAgent)

				r.With(assertAgentReadAccess).Get("/{agentID}/specs", s.getAgentSpecs)
				r.With(assertAgentWriteAccess).Post("/{agentID}/specs", s.updateSpec)
				r.With(assertAgentWriteAccess).Delete("/{agentID}/specs", s.deleteSpec)
			})
		})
	})

	logger.Info(ctx, "http server listening")

	if err := http.Serve(listener, router); err != nil && !errors.Is(err, net.ErrClosed) {
		errs <- errors.WithStack(err)
	}

	logger.Info(ctx, "http server exiting")
}

func (s *Server) getThirdPartyAuthenticator() (*thirdparty.Authenticator, error) {
	var localPublicKey jwk.Key

	localAuth := s.conf.Auth.Local
	if localAuth != nil {
		key, err := jwk.LoadOrGenerate(string(localAuth.PrivateKeyPath), jwk.DefaultKeySize)
		if err != nil {
			return nil, errors.WithStack(err)
		}

		publicKey, err := key.PublicKey()
		if err != nil {
			return nil, errors.WithStack(err)
		}

		if err := publicKey.Set(jwk.AlgorithmKey, jwa.RS256); err != nil {
			return nil, errors.WithStack(err)
		}

		localPublicKey = publicKey
	}

	var getRemoteKeySet thirdparty.GetKeySet

	remoteAuth := s.conf.Auth.Remote
	if remoteAuth != nil {
		refreshInterval := time.Minute * 15
		if remoteAuth.RefreshInterval != nil {
			refreshInterval = time.Duration(*remoteAuth.RefreshInterval)
		}

		fn, err := jwk.CreateCachedRemoteKeySet(context.Background(), string(remoteAuth.JsonWebKeySetURL), refreshInterval)
		if err != nil {
			return nil, errors.WithStack(err)
		}

		getRemoteKeySet = fn
	}

	getKeySet := func(ctx context.Context) (jwk.Set, error) {
		keySet := jwk.NewSet()

		if localPublicKey != nil {
			if err := keySet.AddKey(localPublicKey); err != nil {
				return nil, errors.WithStack(err)
			}
		}

		if getRemoteKeySet != nil {
			remoteKeySet, err := getRemoteKeySet(ctx)
			if err != nil {
				return nil, errors.WithStack(err)
			}

			for idx := 0; idx < remoteKeySet.Len(); idx++ {
				key, ok := remoteKeySet.Key(idx)
				if !ok {
					break
				}

				if err := keySet.AddKey(key); err != nil {
					return nil, errors.WithStack(err)
				}
			}
		}

		return keySet, nil
	}

	getTokenRole, err := s.createGetTokenRoleFunc()
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return thirdparty.NewAuthenticator(getKeySet, getTokenRole, thirdparty.DefaultAcceptableSkew), nil
}

func (s *Server) createGetTokenRoleFunc() (func(ctx context.Context, token jwt.Token) (string, error), error) {
	rawRules := s.conf.Auth.RoleExtractionRules
	rules := make([]*vm.Program, 0, len(rawRules))

	type Env struct {
		JWT map[string]any `expr:"jwt"`
	}

	strFunc := expr.Function(
		"str",
		func(params ...any) (any, error) {
			var builder strings.Builder

			for _, p := range params {
				if _, err := builder.WriteString(fmt.Sprintf("%v", p)); err != nil {
					return nil, errors.WithStack(err)
				}
			}

			return builder.String(), nil
		},
		new(func(any) string),
	)

	for _, rr := range rawRules {
		r, err := expr.Compile(rr,
			expr.Env(Env{}),
			expr.AsKind(reflect.String),
			strFunc,
		)
		if err != nil {
			return nil, errors.Wrapf(err, "could not compile role extraction rule '%s'", rr)
		}

		rules = append(rules, r)
	}

	return func(ctx context.Context, token jwt.Token) (string, error) {
		jwt, err := token.AsMap(ctx)
		if err != nil {
			return "", errors.WithStack(err)
		}

		vm := vm.VM{}

		for _, r := range rules {
			result, err := vm.Run(r, Env{
				JWT: jwt,
			})
			if err != nil {
				return "", errors.WithStack(err)
			}

			role, ok := result.(string)
			if !ok {
				logger.Debug(ctx, "ignoring unexpected role extraction result", logger.F("result", result))
				continue
			}

			if role != "" {
				return role, nil
			}
		}

		return "", errors.New("could not extract role from token")
	}, nil
}

func New(funcs ...OptionFunc) *Server {
	opt := defaultOption()
	for _, fn := range funcs {
		fn(opt)
	}

	return &Server{
		conf: opt.Config,
	}
}