package jwt

import (
	"context"
	"errors"
	"net/http"

	"github.com/lestrrat-go/jwx/jwa"
	"github.com/lestrrat-go/jwx/jwt"

	"go.pkg.cx/middleware"
)

// Errors
var (
	ErrTokenInvalid  = errors.New("token invalid")
	ErrTokenNotFound = errors.New("token not found")
)

// Context keys
var (
	JWTCtxKey  = &middleware.CtxKey{Pkg: "go.pkg.cx/middleware/auth/jwt", Name: "JWT"}
	DataCtxKey = &middleware.CtxKey{Pkg: "go.pkg.cx/middleware/auth/token", Name: "Data"}
)

// DefaultOptions represents default jwt auth middleware options
var DefaultOptions = Options(
	WithFindTokenFn(middleware.TokenFromAuthorizationHeader),
	WithFindTokenFn(middleware.TokenFromQuery("jwt")),
	WithFindTokenFn(middleware.TokenFromCookie("jwt")),
	SetResponseHandler(RespondWithUnauthorized),
	SetValidateTokenFn(allowAll),
)

// Options turns a list of option instances into an option
func Options(opts ...Option) Option {
	return func(a *auth) {
		for _, opt := range opts {
			opt(a)
		}
	}
}

// Option configures jwt auth middleware
type Option func(a *auth)

// SetKey sets key to verify jwt token with
func SetKey(key interface{}) Option {
	return func(a *auth) {
		a.key = key
	}
}

// SetAlgorithm sets algorithm to verify jwt token with
func SetAlgorithm(alg jwa.SignatureAlgorithm) Option {
	return func(a *auth) {
		a.algorithm = alg
	}
}

// WithFindTokenFn adds jwt token find function to the list
func WithFindTokenFn(fn func(r *http.Request) string) Option {
	return func(a *auth) {
		a.findTokenFns = append(a.findTokenFns, fn)
	}
}

// SetFindTokenFns sets jwt token find functions list
func SetFindTokenFns(fns ...func(r *http.Request) string) Option {
	return func(a *auth) {
		a.findTokenFns = fns
	}
}

// WithVerifyOption adds jwt verify option to the list
func WithVerifyOption(opt jwt.ValidateOption) Option {
	return func(a *auth) {
		a.verifyOptions = append(a.verifyOptions, opt)
	}
}

// SetVerifyOptions sets jwt verify options list
func SetVerifyOptions(opts ...jwt.ValidateOption) Option {
	return func(a *auth) {
		a.verifyOptions = opts
	}
}

// SetValidateTokenFn sets token validation function
func SetValidateTokenFn(fn func(token jwt.Token) (bool, interface{})) Option {
	return func(a *auth) {
		a.validateTokenFn = fn
	}
}

// SetResponseHandler sets response handler
func SetResponseHandler(fn middleware.ResponseHandle) Option {
	return func(a *auth) {
		a.responseHandler = fn
	}
}

type auth struct {
	key             interface{}
	algorithm       jwa.SignatureAlgorithm
	verifyOptions   []jwt.ValidateOption
	findTokenFns    []func(r *http.Request) string
	validateTokenFn func(token jwt.Token) (bool, interface{})
	responseHandler middleware.ResponseHandle
}

// Middleware returns jwt auth middleware
func Middleware(key interface{}, alg jwa.SignatureAlgorithm, opts ...Option) func(next http.Handler) http.Handler {
	a := &auth{}
	opts = append(opts, SetKey(key), SetAlgorithm(alg))
	opts = append([]Option{DefaultOptions}, opts...)

	for _, opt := range opts {
		opt(a)
	}

	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			var token string
			for _, findTokenFn := range a.findTokenFns {
				token = findTokenFn(r)
				if token != "" {
					break
				}
			}

			if token == "" {
				a.responseHandler(w, r, ErrTokenNotFound)
				return
			}

			jwtToken, err := jwt.ParseString(token, jwt.WithVerify(a.algorithm, a.key))
			if err != nil {
				a.responseHandler(w, r, err)
				return
			}

			if err := jwt.Validate(jwtToken, a.verifyOptions...); err != nil {
				a.responseHandler(w, r, err)
				return
			}

			valid, data := a.validateTokenFn(jwtToken)
			if !valid {
				a.responseHandler(w, r, ErrTokenInvalid)
				return
			}

			ctx := r.Context()
			ctx = context.WithValue(ctx, JWTCtxKey, jwtToken)
			ctx = context.WithValue(ctx, DataCtxKey, data)

			next.ServeHTTP(w, r.WithContext(ctx))
		})
	}
}

// RespondWithUnauthorized is a default response handler
func RespondWithUnauthorized(w http.ResponseWriter, _ *http.Request, _ error) {
	http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
}

func allowAll(_ jwt.Token) (bool, interface{}) {
	return true, nil
}