/*
Copyright 2023 The Dapr Authors
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
    http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package internal

import (
	"errors"
	"fmt"
	"net"
	"net/url"
	"strings"
)

// Parsed represents a parsed gRPC endpoint.
type Parsed struct {
	Target string
	TLS    bool
}

func ParseGRPCEndpoint(endpoint string) (Parsed, error) {
	target := endpoint
	if len(target) == 0 {
		return Parsed{}, errors.New("target is required")
	}

	var dnsAuthority string
	var hostname string
	var tls bool

	urlSplit := strings.Split(target, ":")
	if len(urlSplit) == 3 && !strings.Contains(target, "://") {
		target = strings.Replace(target, ":", "://", 1)
	} else if len(urlSplit) >= 2 && !strings.Contains(target, "://") && schemeKnown(urlSplit[0]) {
		target = strings.Replace(target, ":", "://", 1)
	} else {
		urlSplit = strings.Split(target, "://")
		if len(urlSplit) == 1 {
			target = "dns://" + target
		} else {
			scheme := urlSplit[0]
			if !schemeKnown(scheme) {
				return Parsed{}, fmt.Errorf(("unknown scheme: %q"), scheme)
			}

			if scheme == "dns" {
				urlSplit = strings.Split(target, "/")
				if len(urlSplit) < 4 {
					return Parsed{}, fmt.Errorf("invalid dns scheme: %q", target)
				}
				dnsAuthority = urlSplit[2]
				target = "dns://" + urlSplit[3]
			}
		}
	}

	ptarget, err := url.Parse(target)
	if err != nil {
		return Parsed{}, err
	}

	var errs []string
	for k := range ptarget.Query() {
		if k != "tls" {
			errs = append(errs, fmt.Sprintf("unrecognized query parameter: %q", k))
		}
	}
	if len(errs) > 0 {
		return Parsed{}, fmt.Errorf("failed to parse target %q: %s", target, strings.Join(errs, "; "))
	}

	if ptarget.Query().Has("tls") {
		if ptarget.Scheme == "http" || ptarget.Scheme == "https" {
			return Parsed{}, errors.New("cannot use tls query parameter with http(s) scheme")
		}

		qtls := ptarget.Query().Get("tls")
		if qtls != "true" && qtls != "false" {
			return Parsed{}, fmt.Errorf("invalid value for tls query parameter: %q", qtls)
		}

		tls = qtls == "true"
	}

	scheme := ptarget.Scheme
	if scheme == "https" {
		tls = true
	}
	if scheme == "http" || scheme == "https" {
		scheme = "dns"
	}

	hostname = ptarget.Host

	host, port, err := net.SplitHostPort(hostname)
	aerr, ok := err.(*net.AddrError)
	if ok && aerr.Err == "missing port in address" {
		port = "443"
	} else if err != nil {
		return Parsed{}, err
	} else {
		hostname = host
	}

	if len(hostname) == 0 {
		if scheme == "dns" {
			hostname = "localhost"
		} else {
			hostname = ptarget.Path
		}
	}

	switch scheme {
	case "unix":
		separator := ":"
		if strings.HasPrefix(endpoint, "unix://") {
			separator = "://"
		}
		target = scheme + separator + hostname

	case "vsock":
		target = scheme + ":" + hostname + ":" + port

	case "unix-abstract":
		target = scheme + ":" + hostname

	case "dns":
		if len(ptarget.Path) > 0 {
			return Parsed{}, fmt.Errorf("path is not allowed: %q", ptarget.Path)
		}

		if strings.Count(hostname, ":") == 7 && !strings.HasPrefix(hostname, "[") && !strings.HasSuffix(hostname, "]") {
			hostname = "[" + hostname + "]"
		}
		if len(dnsAuthority) > 0 {
			dnsAuthority = "//" + dnsAuthority + "/"
		}
		target = scheme + ":" + dnsAuthority + hostname + ":" + port

	default:
		return Parsed{}, fmt.Errorf("unsupported scheme: %q", scheme)
	}

	return Parsed{
		Target: target,
		TLS:    tls,
	}, nil
}

func schemeKnown(scheme string) bool {
	for _, s := range []string{
		"dns",
		"unix",
		"unix-abstract",
		"vsock",
		"http",
		"https",
	} {
		if scheme == s {
			return true
		}
	}

	return false
}