package provisioner

import (
	"time"

	"github.com/pkg/errors"
	"golang.org/x/crypto/ssh"
)

// Claims so that individual provisioners can override global claims.
type Claims struct {
	// TLS CA properties
	MinTLSDur     *Duration `json:"minTLSCertDuration,omitempty"`
	MaxTLSDur     *Duration `json:"maxTLSCertDuration,omitempty"`
	DefaultTLSDur *Duration `json:"defaultTLSCertDuration,omitempty"`

	// SSH CA properties
	MinUserSSHDur     *Duration `json:"minUserSSHCertDuration,omitempty"`
	MaxUserSSHDur     *Duration `json:"maxUserSSHCertDuration,omitempty"`
	DefaultUserSSHDur *Duration `json:"defaultUserSSHCertDuration,omitempty"`
	MinHostSSHDur     *Duration `json:"minHostSSHCertDuration,omitempty"`
	MaxHostSSHDur     *Duration `json:"maxHostSSHCertDuration,omitempty"`
	DefaultHostSSHDur *Duration `json:"defaultHostSSHCertDuration,omitempty"`
	EnableSSHCA       *bool     `json:"enableSSHCA,omitempty"`

	// Renewal properties
	DisableRenewal          *bool `json:"disableRenewal,omitempty"`
	AllowRenewalAfterExpiry *bool `json:"allowRenewalAfterExpiry,omitempty"`

	// Other properties
	DisableSmallstepExtensions *bool `json:"disableSmallstepExtensions,omitempty"`
}

// Claimer is the type that controls claims. It provides an interface around the
// current claim and the global one.
type Claimer struct {
	global Claims
	claims *Claims
}

// NewClaimer initializes a new claimer with the given claims.
func NewClaimer(claims *Claims, global Claims) (*Claimer, error) {
	c := &Claimer{global: global, claims: claims}
	err := c.Validate()
	return c, err
}

// Claims returns the merge of the inner and global claims.
func (c *Claimer) Claims() Claims {
	disableRenewal := c.IsDisableRenewal()
	allowRenewalAfterExpiry := c.AllowRenewalAfterExpiry()
	enableSSHCA := c.IsSSHCAEnabled()
	disableSmallstepExtensions := c.IsDisableSmallstepExtensions()

	return Claims{
		MinTLSDur:                  &Duration{c.MinTLSCertDuration()},
		MaxTLSDur:                  &Duration{c.MaxTLSCertDuration()},
		DefaultTLSDur:              &Duration{c.DefaultTLSCertDuration()},
		MinUserSSHDur:              &Duration{c.MinUserSSHCertDuration()},
		MaxUserSSHDur:              &Duration{c.MaxUserSSHCertDuration()},
		DefaultUserSSHDur:          &Duration{c.DefaultUserSSHCertDuration()},
		MinHostSSHDur:              &Duration{c.MinHostSSHCertDuration()},
		MaxHostSSHDur:              &Duration{c.MaxHostSSHCertDuration()},
		DefaultHostSSHDur:          &Duration{c.DefaultHostSSHCertDuration()},
		EnableSSHCA:                &enableSSHCA,
		DisableRenewal:             &disableRenewal,
		AllowRenewalAfterExpiry:    &allowRenewalAfterExpiry,
		DisableSmallstepExtensions: &disableSmallstepExtensions,
	}
}

// DefaultTLSCertDuration returns the default TLS cert duration for the
// provisioner. If the default is not set within the provisioner, then the global
// default from the authority configuration will be used.
func (c *Claimer) DefaultTLSCertDuration() time.Duration {
	if c.claims == nil || c.claims.DefaultTLSDur == nil {
		return c.global.DefaultTLSDur.Duration
	}
	return c.claims.DefaultTLSDur.Duration
}

// MinTLSCertDuration returns the minimum TLS cert duration for the provisioner.
// If the minimum is not set within the provisioner, then the global
// minimum from the authority configuration will be used.
func (c *Claimer) MinTLSCertDuration() time.Duration {
	if c.claims == nil || c.claims.MinTLSDur == nil {
		if c.claims != nil && c.claims.DefaultTLSDur != nil && c.claims.DefaultTLSDur.Duration < c.global.MinTLSDur.Duration {
			return c.claims.DefaultTLSDur.Duration
		}
		return c.global.MinTLSDur.Duration
	}
	return c.claims.MinTLSDur.Duration
}

// MaxTLSCertDuration returns the maximum TLS cert duration for the provisioner.
// If the maximum is not set within the provisioner, then the global
// maximum from the authority configuration will be used.
func (c *Claimer) MaxTLSCertDuration() time.Duration {
	if c.claims == nil || c.claims.MaxTLSDur == nil {
		if c.claims != nil && c.claims.DefaultTLSDur != nil && c.claims.DefaultTLSDur.Duration > c.global.MaxTLSDur.Duration {
			return c.claims.DefaultTLSDur.Duration
		}
		return c.global.MaxTLSDur.Duration
	}
	return c.claims.MaxTLSDur.Duration
}

// IsDisableRenewal returns if the renewal flow is disabled for the
// provisioner. If the property is not set within the provisioner, then the
// global value from the authority configuration will be used.
func (c *Claimer) IsDisableRenewal() bool {
	if c.claims == nil || c.claims.DisableRenewal == nil {
		return *c.global.DisableRenewal
	}
	return *c.claims.DisableRenewal
}

// IsDisableSmallstepExtensions returns whether Smallstep extensions, such as
// the provisioner extension, should be excluded from the certificate.
func (c *Claimer) IsDisableSmallstepExtensions() bool {
	if c.claims == nil || c.claims.DisableSmallstepExtensions == nil {
		return *c.global.DisableSmallstepExtensions
	}
	return *c.claims.DisableSmallstepExtensions
}

// AllowRenewalAfterExpiry returns if the renewal flow is authorized if the
// certificate is expired. If the property is not set within the provisioner
// then the global value from the authority configuration will be used.
func (c *Claimer) AllowRenewalAfterExpiry() bool {
	if c.claims == nil || c.claims.AllowRenewalAfterExpiry == nil {
		return *c.global.AllowRenewalAfterExpiry
	}
	return *c.claims.AllowRenewalAfterExpiry
}

// DefaultSSHCertDuration returns the default SSH certificate duration for the
// given certificate type.
func (c *Claimer) DefaultSSHCertDuration(certType uint32) (time.Duration, error) {
	switch certType {
	case ssh.UserCert:
		return c.DefaultUserSSHCertDuration(), nil
	case ssh.HostCert:
		return c.DefaultHostSSHCertDuration(), nil
	case 0:
		return 0, errors.New("ssh certificate type has not been set")
	default:
		return 0, errors.Errorf("ssh certificate has an unknown type: %d", certType)
	}
}

// DefaultUserSSHCertDuration returns the default SSH user cert duration for the
// provisioner. If the default is not set within the provisioner, then the
// global default from the authority configuration will be used.
func (c *Claimer) DefaultUserSSHCertDuration() time.Duration {
	if c.claims == nil || c.claims.DefaultUserSSHDur == nil {
		return c.global.DefaultUserSSHDur.Duration
	}
	return c.claims.DefaultUserSSHDur.Duration
}

// MinUserSSHCertDuration returns the minimum SSH user cert duration for the
// provisioner. If the minimum is not set within the provisioner, then the
// global minimum from the authority configuration will be used.
func (c *Claimer) MinUserSSHCertDuration() time.Duration {
	if c.claims == nil || c.claims.MinUserSSHDur == nil {
		if c.claims != nil && c.claims.DefaultUserSSHDur != nil && c.claims.DefaultUserSSHDur.Duration < c.global.MinUserSSHDur.Duration {
			return c.claims.DefaultUserSSHDur.Duration
		}
		return c.global.MinUserSSHDur.Duration
	}
	return c.claims.MinUserSSHDur.Duration
}

// MaxUserSSHCertDuration returns the maximum SSH user cert duration for the
// provisioner. If the maximum is not set within the provisioner, then the
// global maximum from the authority configuration will be used.
func (c *Claimer) MaxUserSSHCertDuration() time.Duration {
	if c.claims == nil || c.claims.MaxUserSSHDur == nil {
		if c.claims != nil && c.claims.DefaultUserSSHDur != nil && c.claims.DefaultUserSSHDur.Duration > c.global.MaxUserSSHDur.Duration {
			return c.claims.DefaultUserSSHDur.Duration
		}
		return c.global.MaxUserSSHDur.Duration
	}
	return c.claims.MaxUserSSHDur.Duration
}

// DefaultHostSSHCertDuration returns the default SSH host cert duration for the
// provisioner. If the default is not set within the provisioner, then the
// global default from the authority configuration will be used.
func (c *Claimer) DefaultHostSSHCertDuration() time.Duration {
	if c.claims == nil || c.claims.DefaultHostSSHDur == nil {
		return c.global.DefaultHostSSHDur.Duration
	}
	return c.claims.DefaultHostSSHDur.Duration
}

// MinHostSSHCertDuration returns the minimum SSH host cert duration for the
// provisioner. If the minimum is not set within the provisioner, then the
// global minimum from the authority configuration will be used.
func (c *Claimer) MinHostSSHCertDuration() time.Duration {
	if c.claims == nil || c.claims.MinHostSSHDur == nil {
		if c.claims != nil && c.claims.DefaultHostSSHDur != nil && c.claims.DefaultHostSSHDur.Duration < c.global.MinHostSSHDur.Duration {
			return c.claims.DefaultHostSSHDur.Duration
		}
		return c.global.MinHostSSHDur.Duration
	}
	return c.claims.MinHostSSHDur.Duration
}

// MaxHostSSHCertDuration returns the maximum SSH Host cert duration for the
// provisioner. If the maximum is not set within the provisioner, then the
// global maximum from the authority configuration will be used.
func (c *Claimer) MaxHostSSHCertDuration() time.Duration {
	if c.claims == nil || c.claims.MaxHostSSHDur == nil {
		if c.claims != nil && c.claims.DefaultHostSSHDur != nil && c.claims.DefaultHostSSHDur.Duration > c.global.MaxHostSSHDur.Duration {
			return c.claims.DefaultHostSSHDur.Duration
		}
		return c.global.MaxHostSSHDur.Duration
	}
	return c.claims.MaxHostSSHDur.Duration
}

// IsSSHCAEnabled returns if the SSH CA is enabled for the provisioner. If the
// property is not set within the provisioner, then the global value from the
// authority configuration will be used.
func (c *Claimer) IsSSHCAEnabled() bool {
	if c.claims == nil || c.claims.EnableSSHCA == nil {
		return *c.global.EnableSSHCA
	}
	return *c.claims.EnableSSHCA
}

// Validate validates and modifies the Claims with default values.
func (c *Claimer) Validate() error {
	var (
		min = c.MinTLSCertDuration()
		max = c.MaxTLSCertDuration()
		def = c.DefaultTLSCertDuration()
	)
	switch {
	case min <= 0:
		return errors.Errorf("claims: MinTLSCertDuration must be greater than 0")
	case max <= 0:
		return errors.Errorf("claims: MaxTLSCertDuration must be greater than 0")
	case def <= 0:
		return errors.Errorf("claims: DefaultTLSCertDuration must be greater than 0")
	case max < min:
		return errors.Errorf("claims: MaxCertDuration cannot be less "+
			"than MinCertDuration: MaxCertDuration - %v, MinCertDuration - %v", max, min)
	case def < min:
		return errors.Errorf("claims: DefaultCertDuration cannot be less than MinCertDuration: DefaultCertDuration - %v, MinCertDuration - %v", def, min)
	case max < def:
		return errors.Errorf("claims: MaxCertDuration cannot be less than DefaultCertDuration: MaxCertDuration - %v, DefaultCertDuration - %v", max, def)
	default:
		return nil
	}
}