package auth

import (
	"context"
	"net/http"
	"strings"

	"github.com/lestrrat-go/jwx/v2/jwk"
	"github.com/lestrrat-go/jwx/v2/jws"
	"github.com/lestrrat-go/jwx/v2/jwt"
	"github.com/pkg/errors"
)

const (
	CookieName string = "edge-auth"
)

type GetKeySetFunc func() (jwk.Set, error)

func WithJWT(getKeySet GetKeySetFunc) OptionFunc {
	return func(o *Option) {
		o.GetClaim = func(ctx context.Context, r *http.Request, claimName string) (string, error) {
			claim, err := getClaim[string](r, claimName, getKeySet)
			if err != nil {
				return "", errors.WithStack(err)
			}

			return claim, nil
		}
	}
}

func FindToken(r *http.Request, getKeySet GetKeySetFunc) (jwt.Token, error) {
	authorization := r.Header.Get("Authorization")

	// Retrieve token from Authorization header
	rawToken := strings.TrimPrefix(authorization, "Bearer ")

	// Retrieve token from ?edge-auth=<value>
	if rawToken == "" {
		rawToken = r.URL.Query().Get(CookieName)
	}

	if rawToken == "" {
		cookie, err := r.Cookie(CookieName)
		if err != nil && !errors.Is(err, http.ErrNoCookie) {
			return nil, errors.WithStack(err)
		}

		if cookie != nil {
			rawToken = cookie.Value
		}
	}

	if rawToken == "" {
		return nil, errors.WithStack(ErrUnauthenticated)
	}

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

	if keySet == nil {
		return nil, errors.New("no keyset")
	}

	token, err := jwt.Parse([]byte(rawToken),
		jwt.WithKeySet(keySet, jws.WithRequireKid(false)),
		jwt.WithValidate(true),
	)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return token, nil
}

func getClaim[T any](r *http.Request, claimAttr string, getKeySet GetKeySetFunc) (T, error) {
	token, err := FindToken(r, getKeySet)
	if err != nil {
		return *new(T), errors.WithStack(err)
	}

	ctx := r.Context()

	mapClaims, err := token.AsMap(ctx)
	if err != nil {
		return *new(T), errors.WithStack(err)
	}

	rawClaim, exists := mapClaims[claimAttr]
	if !exists {
		return *new(T), errors.WithStack(ErrClaimNotFound)
	}

	claim, ok := rawClaim.(T)
	if !ok {
		return *new(T), errors.Errorf("unexpected claim '%s' to be of type '%T', got '%T'", claimAttr, new(T), rawClaim)
	}

	return claim, nil
}