package gortsplib

import (
	"encoding/base64"
	"fmt"
	"net/url"
	"strings"
)

// authClient is an object that helps a client to send its credentials to a
// server.
type authClient struct {
	user   string
	pass   string
	method AuthMethod
	realm  string
	nonce  string
}

// newAuthClient allocates an authClient.
// header is the WWW-Authenticate header provided by the server.
func newAuthClient(v HeaderValue, user string, pass string) (*authClient, error) {
	// prefer digest
	if headerAuthDigest := func() string {
		for _, vi := range v {
			if strings.HasPrefix(vi, "Digest ") {
				return vi
			}
		}
		return ""
	}(); headerAuthDigest != "" {
		auth, err := ReadHeaderAuth(HeaderValue{headerAuthDigest})
		if err != nil {
			return nil, err
		}

		if auth.Realm == nil {
			return nil, fmt.Errorf("realm not provided")
		}

		if auth.Nonce == nil {
			return nil, fmt.Errorf("nonce not provided")
		}

		return &authClient{
			user:   user,
			pass:   pass,
			method: Digest,
			realm:  *auth.Realm,
			nonce:  *auth.Nonce,
		}, nil
	}

	if headerAuthBasic := func() string {
		for _, vi := range v {
			if strings.HasPrefix(vi, "Basic ") {
				return vi
			}
		}
		return ""
	}(); headerAuthBasic != "" {
		auth, err := ReadHeaderAuth(HeaderValue{headerAuthBasic})
		if err != nil {
			return nil, err
		}

		if auth.Realm == nil {
			return nil, fmt.Errorf("realm not provided")
		}

		return &authClient{
			user:   user,
			pass:   pass,
			method: Basic,
			realm:  *auth.Realm,
		}, nil
	}

	return nil, fmt.Errorf("there are no authentication methods available")
}

// GenerateHeader generates an Authorization Header that allows to authenticate a request with
// the given method and url.
func (ac *authClient) GenerateHeader(method Method, ur *url.URL) HeaderValue {
	switch ac.method {
	case Basic:
		response := base64.StdEncoding.EncodeToString([]byte(ac.user + ":" + ac.pass))

		return HeaderValue{"Basic " + response}

	case Digest:
		response := md5Hex(md5Hex(ac.user+":"+ac.realm+":"+ac.pass) + ":" +
			ac.nonce + ":" + md5Hex(string(method)+":"+ur.String()))

		return (&HeaderAuth{
			Method:   Digest,
			Username: &ac.user,
			Realm:    &ac.realm,
			Nonce:    &ac.nonce,
			URI: func() *string {
				v := ur.String()
				return &v
			}(),
			Response: &response,
		}).Write()
	}

	return nil
}