package certs

import (
	"bytes"
	"crypto/x509"
	"crypto/x509/pkix"
	"fmt"
	"strings"
	"time"
)

var (
	// From RFC 5280 Section 4.1.2.5
	unknownNotAfter = time.Unix(253402300799, 0)
)

// compareCertData returns an error if any of the 'important' bits of the two
// certificates differ. Those are the bits that we template ourselves, and that
// are not issue-dependent (ie. not time or serial or kid or ...).
func compareCertData(template, cert *x509.Certificate) error {
	if want, got := template.Subject.String(), cert.Subject.String(); want != got {
		return fmt.Errorf("issued for different subject, wanted %s, got %s", want, got)
	}
	if want, got := strings.Join(template.DNSNames, ","), strings.Join(cert.DNSNames, ","); want != got {
		return fmt.Errorf("issued for different DNS names, wanted %s, got %s", want, got)
	}
	if want, got := len(template.IPAddresses), len(cert.IPAddresses); want != got {
		return fmt.Errorf("issued for different IP addresses, wanted %v, got %v", want, got)
	} else {
		for i := 0; i < len(template.IPAddresses); i++ {
			if want, got := template.IPAddresses[i], cert.IPAddresses[i]; !bytes.Equal(want, got) {
				return fmt.Errorf("issued for different IP addresses, wanted %v, got %v", want, got)
			}
		}
	}
	if want, got := template.KeyUsage, cert.KeyUsage; want != got {
		return fmt.Errorf("issued for different key usage, wanted %d, got %d", want, got)
	}
	if want, got := len(template.ExtKeyUsage), len(cert.ExtKeyUsage); want != got {
		return fmt.Errorf("issued for different ext key usage, wanted %v, got %v", want, got)
	} else {
		for i := 0; i < len(template.ExtKeyUsage); i++ {
			if want, got := template.ExtKeyUsage[i], cert.ExtKeyUsage[i]; want != got {
				return fmt.Errorf("issued for different ext key usage, wanted %v, got %v", want, got)
			}
		}
	}
	if want, got := template.IsCA, cert.IsCA; want != got {
		return fmt.Errorf("issued for different IsCA, wanted %v, got %v", want, got)
	}
	if want, got := template.BasicConstraintsValid, cert.BasicConstraintsValid; want != got {
		return fmt.Errorf("issued for different basic constraints valid, wanted %v, got %v", want, got)
	}
	return nil
}

// template builds an x509 'template' certificate, ie. makes an
// x509.Certificate with all the fields built up from the data contained in
// Certificate, but without any per-issue fields like times, serial number,
// etc.
func (c *Certificate) template() *x509.Certificate {
	template := &x509.Certificate{
		Subject: pkix.Name{
			CommonName: c.cn,
		},
		DNSNames:    c.san,
		IPAddresses: c.ips,
	}
	if c.o != "" {
		template.Subject.Organization = []string{c.o}
	}
	switch c.kind {
	case kindServer:
		template.KeyUsage = x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment
		template.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth}
		template.DNSNames = c.san
	case kindClient:
		template.KeyUsage = x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment
		template.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth}
		template.DNSNames = c.san
	case kindClientServer:
		template.KeyUsage = x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment
		template.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth}
	case kindCA:
		template.IsCA = true
		template.BasicConstraintsValid = true
		template.KeyUsage = x509.KeyUsageCertSign | x509.KeyUsageCRLSign | x509.KeyUsageDigitalSignature
		template.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageOCSPSigning}
		template.AuthorityKeyId = template.SubjectKeyId
	case kindProdvider:
		template.IsCA = true
		template.BasicConstraintsValid = true
		template.KeyUsage = x509.KeyUsageCertSign | x509.KeyUsageCRLSign | x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment
		template.ExtKeyUsage = []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageOCSPSigning}
		template.AuthorityKeyId = template.SubjectKeyId
	}
	return template
}