// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package madmin

import (
	"encoding/json"
	"io"
	"io/ioutil"
	"net"
	"net/http"
	"net/url"
	"strings"

	"github.com/minio/minio-go/v7/pkg/s3utils"
)

// AdminAPIVersion - admin api version used in the request.
const (
	AdminAPIVersion   = "v3"
	AdminAPIVersionV2 = "v2"
	adminAPIPrefix    = "/" + AdminAPIVersion
)

// jsonDecoder decode json to go type.
func jsonDecoder(body io.Reader, v interface{}) error {
	d := json.NewDecoder(body)
	return d.Decode(v)
}

// getEndpointURL - construct a new endpoint.
func getEndpointURL(endpoint string, secure bool) (*url.URL, error) {
	if strings.Contains(endpoint, ":") {
		host, _, err := net.SplitHostPort(endpoint)
		if err != nil {
			return nil, err
		}
		if !s3utils.IsValidIP(host) && !s3utils.IsValidDomain(host) {
			msg := "Endpoint: " + endpoint + " does not follow ip address or domain name standards."
			return nil, ErrInvalidArgument(msg)
		}
	} else {
		if !s3utils.IsValidIP(endpoint) && !s3utils.IsValidDomain(endpoint) {
			msg := "Endpoint: " + endpoint + " does not follow ip address or domain name standards."
			return nil, ErrInvalidArgument(msg)
		}
	}

	// If secure is false, use 'http' scheme.
	scheme := "https"
	if !secure {
		scheme = "http"
	}

	// Strip the obvious :443 and :80 from the endpoint
	// to avoid the signature mismatch error.
	if secure && strings.HasSuffix(endpoint, ":443") {
		endpoint = strings.TrimSuffix(endpoint, ":443")
	}
	if !secure && strings.HasSuffix(endpoint, ":80") {
		endpoint = strings.TrimSuffix(endpoint, ":80")
	}

	// Construct a secured endpoint URL.
	endpointURLStr := scheme + "://" + endpoint
	endpointURL, err := url.Parse(endpointURLStr)
	if err != nil {
		return nil, err
	}

	// Validate incoming endpoint URL.
	if err := isValidEndpointURL(endpointURL.String()); err != nil {
		return nil, err
	}
	return endpointURL, nil
}

// Verify if input endpoint URL is valid.
func isValidEndpointURL(endpointURL string) error {
	if endpointURL == "" {
		return ErrInvalidArgument("Endpoint url cannot be empty.")
	}
	url, err := url.Parse(endpointURL)
	if err != nil {
		return ErrInvalidArgument("Endpoint url cannot be parsed.")
	}
	if url.Path != "/" && url.Path != "" {
		return ErrInvalidArgument("Endpoint url cannot have fully qualified paths.")
	}
	return nil
}

// closeResponse close non nil response with any response Body.
// convenient wrapper to drain any remaining data on response body.
//
// Subsequently this allows golang http RoundTripper
// to re-use the same connection for future requests.
func closeResponse(resp *http.Response) {
	// Callers should close resp.Body when done reading from it.
	// If resp.Body is not closed, the Client's underlying RoundTripper
	// (typically Transport) may not be able to re-use a persistent TCP
	// connection to the server for a subsequent "keep-alive" request.
	if resp != nil && resp.Body != nil {
		// Drain any remaining Body and then close the connection.
		// Without this closing connection would disallow re-using
		// the same connection for future uses.
		//  - http://stackoverflow.com/a/17961593/4465767
		io.Copy(ioutil.Discard, resp.Body)
		resp.Body.Close()
	}
}