/*
Copyright (c) 2016 VMware, Inc. All Rights Reserved.

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 object

import (
	"crypto/sha256"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/asn1"
	"errors"
	"fmt"
	"io"
	"net/url"
	"strings"
	"text/tabwriter"

	"github.com/vmware/govmomi/vim25/soap"
	"github.com/vmware/govmomi/vim25/types"
)

// HostCertificateInfo provides helpers for types.HostCertificateManagerCertificateInfo
type HostCertificateInfo struct {
	types.HostCertificateManagerCertificateInfo

	ThumbprintSHA1   string
	ThumbprintSHA256 string

	Err         error
	Certificate *x509.Certificate `json:"-"`

	subjectName *pkix.Name
	issuerName  *pkix.Name
}

// FromCertificate converts x509.Certificate to HostCertificateInfo
func (info *HostCertificateInfo) FromCertificate(cert *x509.Certificate) *HostCertificateInfo {
	info.Certificate = cert
	info.subjectName = &cert.Subject
	info.issuerName = &cert.Issuer

	info.Issuer = info.fromName(info.issuerName)
	info.NotBefore = &cert.NotBefore
	info.NotAfter = &cert.NotAfter
	info.Subject = info.fromName(info.subjectName)

	info.ThumbprintSHA1 = soap.ThumbprintSHA1(cert)

	// SHA-256 for info purposes only, API fields all use SHA-1
	sum := sha256.Sum256(cert.Raw)
	hex := make([]string, len(sum))
	for i, b := range sum {
		hex[i] = fmt.Sprintf("%02X", b)
	}
	info.ThumbprintSHA256 = strings.Join(hex, ":")

	if info.Status == "" {
		info.Status = string(types.HostCertificateManagerCertificateInfoCertificateStatusUnknown)
	}

	return info
}

// FromURL connects to the given URL.Host via tls.Dial with the given tls.Config and populates the HostCertificateInfo
// via tls.ConnectionState.  If the certificate was verified with the given tls.Config, the Err field will be nil.
// Otherwise, Err will be set to the x509.UnknownAuthorityError or x509.HostnameError.
// If tls.Dial returns an error of any other type, that error is returned.
func (info *HostCertificateInfo) FromURL(u *url.URL, config *tls.Config) error {
	addr := u.Host
	if !(strings.LastIndex(addr, ":") > strings.LastIndex(addr, "]")) {
		addr += ":443"
	}

	conn, err := tls.Dial("tcp", addr, config)
	if err != nil {
		if !errors.As(err, &x509.UnknownAuthorityError{}) && !errors.As(err, &x509.HostnameError{}){
			return err
		}

		info.Err = err

		conn, err = tls.Dial("tcp", addr, &tls.Config{InsecureSkipVerify: true})
		if err != nil {
			return err
		}
	} else {
		info.Status = string(types.HostCertificateManagerCertificateInfoCertificateStatusGood)
	}

	state := conn.ConnectionState()
	_ = conn.Close()
	info.FromCertificate(state.PeerCertificates[0])

	return nil
}

var emailAddressOID = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 1}

func (info *HostCertificateInfo) fromName(name *pkix.Name) string {
	var attrs []string

	oids := map[string]string{
		emailAddressOID.String(): "emailAddress",
	}

	for _, attr := range name.Names {
		if key, ok := oids[attr.Type.String()]; ok {
			attrs = append(attrs, fmt.Sprintf("%s=%s", key, attr.Value))
		}
	}

	attrs = append(attrs, fmt.Sprintf("CN=%s", name.CommonName))

	add := func(key string, vals []string) {
		for _, val := range vals {
			attrs = append(attrs, fmt.Sprintf("%s=%s", key, val))
		}
	}

	elts := []struct {
		key string
		val []string
	}{
		{"OU", name.OrganizationalUnit},
		{"O", name.Organization},
		{"L", name.Locality},
		{"ST", name.Province},
		{"C", name.Country},
	}

	for _, elt := range elts {
		add(elt.key, elt.val)
	}

	return strings.Join(attrs, ",")
}

func (info *HostCertificateInfo) toName(s string) *pkix.Name {
	var name pkix.Name

	for _, pair := range strings.Split(s, ",") {
		attr := strings.SplitN(pair, "=", 2)
		if len(attr) != 2 {
			continue
		}

		v := attr[1]

		switch strings.ToLower(attr[0]) {
		case "cn":
			name.CommonName = v
		case "ou":
			name.OrganizationalUnit = append(name.OrganizationalUnit, v)
		case "o":
			name.Organization = append(name.Organization, v)
		case "l":
			name.Locality = append(name.Locality, v)
		case "st":
			name.Province = append(name.Province, v)
		case "c":
			name.Country = append(name.Country, v)
		case "emailaddress":
			name.Names = append(name.Names, pkix.AttributeTypeAndValue{Type: emailAddressOID, Value: v})
		}
	}

	return &name
}

// SubjectName parses Subject into a pkix.Name
func (info *HostCertificateInfo) SubjectName() *pkix.Name {
	if info.subjectName != nil {
		return info.subjectName
	}

	return info.toName(info.Subject)
}

// IssuerName parses Issuer into a pkix.Name
func (info *HostCertificateInfo) IssuerName() *pkix.Name {
	if info.issuerName != nil {
		return info.issuerName
	}

	return info.toName(info.Issuer)
}

// Write outputs info similar to the Chrome Certificate Viewer.
func (info *HostCertificateInfo) Write(w io.Writer) error {
	tw := tabwriter.NewWriter(w, 2, 0, 2, ' ', 0)

	s := func(val string) string {
		if val != "" {
			return val
		}
		return "<Not Part Of Certificate>"
	}

	ss := func(val []string) string {
		return s(strings.Join(val, ","))
	}

	name := func(n *pkix.Name) {
		fmt.Fprintf(tw, "  Common Name (CN):\t%s\n", s(n.CommonName))
		fmt.Fprintf(tw, "  Organization (O):\t%s\n", ss(n.Organization))
		fmt.Fprintf(tw, "  Organizational Unit (OU):\t%s\n", ss(n.OrganizationalUnit))
	}

	status := info.Status
	if info.Err != nil {
		status = fmt.Sprintf("ERROR %s", info.Err)
	}
	fmt.Fprintf(tw, "Certificate Status:\t%s\n", status)

	fmt.Fprintln(tw, "Issued To:\t")
	name(info.SubjectName())

	fmt.Fprintln(tw, "Issued By:\t")
	name(info.IssuerName())

	fmt.Fprintln(tw, "Validity Period:\t")
	fmt.Fprintf(tw, "  Issued On:\t%s\n", info.NotBefore)
	fmt.Fprintf(tw, "  Expires On:\t%s\n", info.NotAfter)

	if info.ThumbprintSHA1 != "" {
		fmt.Fprintln(tw, "Thumbprints:\t")
		if info.ThumbprintSHA256 != "" {
			fmt.Fprintf(tw, "  SHA-256 Thumbprint:\t%s\n", info.ThumbprintSHA256)
		}
		fmt.Fprintf(tw, "  SHA-1 Thumbprint:\t%s\n", info.ThumbprintSHA1)
	}

	return tw.Flush()
}