package authority

import (
	"encoding/json"
	"fmt"
	"net"
	"os"
	"time"

	"github.com/pkg/errors"
	"github.com/smallstep/certificates/authority/provisioner"
	"github.com/smallstep/certificates/db"
	kms "github.com/smallstep/certificates/kms/apiv1"
	"github.com/smallstep/certificates/templates"
	"github.com/smallstep/cli/crypto/tlsutil"
	"github.com/smallstep/cli/crypto/x509util"
)

var (
	// DefaultTLSOptions represents the default TLS version as well as the cipher
	// suites used in the TLS certificates.
	DefaultTLSOptions = tlsutil.TLSOptions{
		CipherSuites: x509util.CipherSuites{
			"TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305",
			"TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
			"TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
		},
		MinVersion:    1.2,
		MaxVersion:    1.2,
		Renegotiation: false,
	}
	defaultBackdate         = time.Minute
	defaultDisableRenewal   = false
	defaultEnableSSHCA      = false
	globalProvisionerClaims = provisioner.Claims{
		MinTLSDur:         &provisioner.Duration{Duration: 5 * time.Minute}, // TLS certs
		MaxTLSDur:         &provisioner.Duration{Duration: 24 * time.Hour},
		DefaultTLSDur:     &provisioner.Duration{Duration: 24 * time.Hour},
		DisableRenewal:    &defaultDisableRenewal,
		MinUserSSHDur:     &provisioner.Duration{Duration: 5 * time.Minute}, // User SSH certs
		MaxUserSSHDur:     &provisioner.Duration{Duration: 24 * time.Hour},
		DefaultUserSSHDur: &provisioner.Duration{Duration: 16 * time.Hour},
		MinHostSSHDur:     &provisioner.Duration{Duration: 5 * time.Minute}, // Host SSH certs
		MaxHostSSHDur:     &provisioner.Duration{Duration: 30 * 24 * time.Hour},
		DefaultHostSSHDur: &provisioner.Duration{Duration: 30 * 24 * time.Hour},
		EnableSSHCA:       &defaultEnableSSHCA,
	}
)

// Config represents the CA configuration and it's mapped to a JSON object.
type Config struct {
	Root             multiString          `json:"root"`
	FederatedRoots   []string             `json:"federatedRoots"`
	IntermediateCert string               `json:"crt"`
	IntermediateKey  string               `json:"key"`
	Address          string               `json:"address"`
	DNSNames         []string             `json:"dnsNames"`
	KMS              *kms.Options         `json:"kms,omitempty"`
	SSH              *SSHConfig           `json:"ssh,omitempty"`
	Logger           json.RawMessage      `json:"logger,omitempty"`
	DB               *db.Config           `json:"db,omitempty"`
	Monitoring       json.RawMessage      `json:"monitoring,omitempty"`
	AuthorityConfig  *AuthConfig          `json:"authority,omitempty"`
	TLS              *tlsutil.TLSOptions  `json:"tls,omitempty"`
	Password         string               `json:"password,omitempty"`
	Templates        *templates.Templates `json:"templates,omitempty"`
}

// AuthConfig represents the configuration options for the authority.
type AuthConfig struct {
	Provisioners         provisioner.List      `json:"provisioners"`
	Template             *x509util.ASN1DN      `json:"template,omitempty"`
	Claims               *provisioner.Claims   `json:"claims,omitempty"`
	DisableIssuedAtCheck bool                  `json:"disableIssuedAtCheck,omitempty"`
	Backdate             *provisioner.Duration `json:"backdate,omitempty"`
}

// init initializes the required fields in the AuthConfig if they are not
// provided.
func (c *AuthConfig) init() {
	if c.Provisioners == nil {
		c.Provisioners = provisioner.List{}
	}
	if c.Template == nil {
		c.Template = &x509util.ASN1DN{}
	}
	if c.Backdate == nil {
		c.Backdate = &provisioner.Duration{
			Duration: defaultBackdate,
		}
	}
}

// Validate validates the authority configuration.
func (c *AuthConfig) Validate(audiences provisioner.Audiences) error {
	if c == nil {
		return errors.New("authority cannot be undefined")
	}

	// Initialize required fields.
	c.init()

	// Check that only one K8sSA is enabled
	var k8sCount int
	for _, p := range c.Provisioners {
		if p.GetType() == provisioner.TypeK8sSA {
			k8sCount++
		}
	}
	if k8sCount > 1 {
		return errors.New("cannot have more than one kubernetes service account provisioner")
	}

	if c.Backdate.Duration < 0 {
		return errors.New("authority.backdate cannot be less than 0")
	}

	return nil
}

// LoadConfiguration parses the given filename in JSON format and returns the
// configuration struct.
func LoadConfiguration(filename string) (*Config, error) {
	f, err := os.Open(filename)
	if err != nil {
		return nil, errors.Wrapf(err, "error opening %s", filename)
	}
	defer f.Close()

	var c Config
	if err := json.NewDecoder(f).Decode(&c); err != nil {
		return nil, errors.Wrapf(err, "error parsing %s", filename)
	}

	return &c, nil
}

// initializes the minimal configuration required to create an authority. This
// is mainly used on embedded authorities.
func (c *Config) init() {
	if c.DNSNames == nil {
		c.DNSNames = []string{"localhost", "127.0.0.1", "::1"}
	}
	if c.TLS == nil {
		c.TLS = &DefaultTLSOptions
	}
	if c.AuthorityConfig == nil {
		c.AuthorityConfig = &AuthConfig{}
	}
	c.AuthorityConfig.init()
}

// Save saves the configuration to the given filename.
func (c *Config) Save(filename string) error {
	f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
	if err != nil {
		return errors.Wrapf(err, "error opening %s", filename)
	}
	defer f.Close()

	enc := json.NewEncoder(f)
	enc.SetIndent("", "\t")
	return errors.Wrapf(enc.Encode(c), "error writing %s", filename)
}

// Validate validates the configuration.
func (c *Config) Validate() error {
	switch {
	case c.Address == "":
		return errors.New("address cannot be empty")

	case c.Root.HasEmpties():
		return errors.New("root cannot be empty")

	case c.IntermediateCert == "":
		return errors.New("crt cannot be empty")

	case c.IntermediateKey == "":
		return errors.New("key cannot be empty")

	case len(c.DNSNames) == 0:
		return errors.New("dnsNames cannot be empty")
	}

	// Validate address (a port is required)
	if _, _, err := net.SplitHostPort(c.Address); err != nil {
		return errors.Errorf("invalid address %s", c.Address)
	}

	if c.TLS == nil {
		c.TLS = &DefaultTLSOptions
	} else {
		if len(c.TLS.CipherSuites) == 0 {
			c.TLS.CipherSuites = DefaultTLSOptions.CipherSuites
		}
		if c.TLS.MaxVersion == 0 {
			c.TLS.MaxVersion = DefaultTLSOptions.MaxVersion
		}
		if c.TLS.MinVersion == 0 {
			c.TLS.MinVersion = c.TLS.MaxVersion
		}
		if c.TLS.MinVersion > c.TLS.MaxVersion {
			return errors.New("tls minVersion cannot exceed tls maxVersion")
		}
		c.TLS.Renegotiation = c.TLS.Renegotiation || DefaultTLSOptions.Renegotiation
	}

	// Validate KMS options, nil is ok.
	if err := c.KMS.Validate(); err != nil {
		return err
	}

	// Validate ssh: nil is ok
	if err := c.SSH.Validate(); err != nil {
		return err
	}

	// Validate templates: nil is ok
	if err := c.Templates.Validate(); err != nil {
		return err
	}

	return c.AuthorityConfig.Validate(c.getAudiences())
}

// getAudiences returns the legacy and possible urls without the ports that will
// be used as the default provisioner audiences. The CA might have proxies in
// front so we cannot rely on the port.
func (c *Config) getAudiences() provisioner.Audiences {
	audiences := provisioner.Audiences{
		Sign:      []string{legacyAuthority},
		Revoke:    []string{legacyAuthority},
		SSHSign:   []string{},
		SSHRevoke: []string{},
		SSHRenew:  []string{},
	}

	for _, name := range c.DNSNames {
		audiences.Sign = append(audiences.Sign,
			fmt.Sprintf("https://%s/1.0/sign", name),
			fmt.Sprintf("https://%s/sign", name),
			fmt.Sprintf("https://%s/1.0/ssh/sign", name),
			fmt.Sprintf("https://%s/ssh/sign", name))
		audiences.Revoke = append(audiences.Revoke,
			fmt.Sprintf("https://%s/1.0/revoke", name),
			fmt.Sprintf("https://%s/revoke", name))
		audiences.SSHSign = append(audiences.SSHSign,
			fmt.Sprintf("https://%s/1.0/ssh/sign", name),
			fmt.Sprintf("https://%s/ssh/sign", name),
			fmt.Sprintf("https://%s/1.0/sign", name),
			fmt.Sprintf("https://%s/sign", name))
		audiences.SSHRevoke = append(audiences.SSHRevoke,
			fmt.Sprintf("https://%s/1.0/ssh/revoke", name),
			fmt.Sprintf("https://%s/ssh/revoke", name))
		audiences.SSHRenew = append(audiences.SSHRenew,
			fmt.Sprintf("https://%s/1.0/ssh/renew", name),
			fmt.Sprintf("https://%s/ssh/renew", name))
		audiences.SSHRekey = append(audiences.SSHRekey,
			fmt.Sprintf("https://%s/1.0/ssh/rekey", name),
			fmt.Sprintf("https://%s/ssh/rekey", name))
	}

	return audiences
}