package narco

import (
	"fmt"
	"net/http"
	"strings"

	"github.com/codemodus/chain"
	"golang.org/x/net/context"
	"ponyo.epfl.ch/gitlab/alexandre.tuleu/narco/jwt"
)

type JWT struct {
	signer jwt.Signer
}

const (
	jwtKeyGenerator narcoKey = 2
	jwtKeyOutput    narcoKey = 3
)

func (j *JWT) Wrap() func(chain.Handler) chain.Handler {
	return func(other chain.Handler) chain.Handler {
		return chain.HandlerFunc(func(ctx context.Context, rw http.ResponseWriter, req *http.Request) {
			tokenGenerator, ok := ctx.Value(jwtKeyGenerator).(TokenCreator)

			if tokenGenerator == nil || ok == false {
				//we did not register a token we ignore all processing
				other.ServeHTTPContext(ctx, rw, req)
				return
			}

			// check for the header
			tokenStr, ok := req.Header["Authorization"]
			if ok == false {
				// no Authorization header, we are just not
				// authentified, we process down, no token added
				other.ServeHTTPContext(ctx, rw, req)
				return
			}

			if len(tokenStr) != 1 || strings.HasPrefix(tokenStr[0], "Bearer ") == false {
				Error(ctx, rw, fmt.Errorf("Invalid Authorization HTTP Header %v", tokenStr), http.StatusForbidden)
				return
			}
			tkData := strings.TrimPrefix(tokenStr[0], "Bearer ")

			//parse the desired token, with signature checking
			token := tokenGenerator()
			err := jwt.DecodeJWS([]byte(tkData), token, j.signer)
			if err != nil {
				Error(ctx, rw, err, http.StatusForbidden)
				return
			}

			// we process down the pipeline, with the token added to
			// context
			other.ServeHTTPContext(context.WithValue(ctx, jwtKeyOutput, token), rw, req)
		})
	}
}

func GetJwt(ctx context.Context) interface{} {
	return ctx.Value(jwtKeyOutput)
}

//A Token Creator should produce a new pointer to a desired token
//struct
type TokenCreator func() interface{}

// RegisterJwtType should be used to register the token rtyope
// expected in the context. TokenCreator should allocate a new,
// unparsed token.
func RegisterJwtType(ctx context.Context, generator TokenCreator) context.Context {
	return context.WithValue(ctx, jwtKeyGenerator, generator)
}

func NewJWT(s jwt.Signer) *JWT {
	return &JWT{signer: s}
}