package provisioner

import (
	"context"
	"crypto/x509"
	"encoding/json"
	"net/url"
	"regexp"
	"strings"

	"github.com/pkg/errors"
)

// Interface is the interface that all provisioner types must implement.
type Interface interface {
	GetID() string
	GetTokenID(token string) (string, error)
	GetName() string
	GetType() Type
	GetEncryptedKey() (kid string, key string, ok bool)
	Init(config Config) error
	AuthorizeSign(ctx context.Context, token string) ([]SignOption, error)
	AuthorizeRenewal(cert *x509.Certificate) error
	AuthorizeRevoke(token string) error
}

// Audiences stores all supported audiences by request type.
type Audiences struct {
	Sign   []string
	Revoke []string
}

// All returns all supported audiences across all request types in one list.
func (a Audiences) All() []string {
	return append(a.Sign, a.Revoke...)
}

// WithFragment returns a copy of audiences where the url audiences contains the
// given fragment.
func (a Audiences) WithFragment(fragment string) Audiences {
	ret := Audiences{
		Sign:   make([]string, len(a.Sign)),
		Revoke: make([]string, len(a.Revoke)),
	}
	for i, s := range a.Sign {
		if u, err := url.Parse(s); err == nil {
			ret.Sign[i] = u.ResolveReference(&url.URL{Fragment: fragment}).String()
		} else {
			ret.Sign[i] = s
		}
	}
	for i, s := range a.Revoke {
		if u, err := url.Parse(s); err == nil {
			ret.Revoke[i] = u.ResolveReference(&url.URL{Fragment: fragment}).String()
		} else {
			ret.Revoke[i] = s
		}
	}
	return ret
}

// generateSignAudience generates a sign audience with the format
// https://<host>/1.0/sign#provisionerID
func generateSignAudience(caURL string, provisionerID string) (string, error) {
	u, err := url.Parse(caURL)
	if err != nil {
		return "", errors.Wrapf(err, "error parsing %s", caURL)
	}
	return u.ResolveReference(&url.URL{Path: "/1.0/sign", Fragment: provisionerID}).String(), nil
}

// Type indicates the provisioner Type.
type Type int

const (
	noopType Type = 0
	// TypeJWK is used to indicate the JWK provisioners.
	TypeJWK Type = 1
	// TypeOIDC is used to indicate the OIDC provisioners.
	TypeOIDC Type = 2
	// TypeGCP is used to indicate the GCP provisioners.
	TypeGCP Type = 3
	// TypeAWS is used to indicate the AWS provisioners.
	TypeAWS Type = 4
	// TypeAzure is used to indicate the Azure provisioners.
	TypeAzure Type = 5

	// RevokeAudienceKey is the key for the 'revoke' audiences in the audiences map.
	RevokeAudienceKey = "revoke"
	// SignAudienceKey is the key for the 'sign' audiences in the audiences map.
	SignAudienceKey = "sign"
)

// String returns the string representation of the type.
func (t Type) String() string {
	switch t {
	case TypeJWK:
		return "JWK"
	case TypeOIDC:
		return "OIDC"
	case TypeGCP:
		return "GCP"
	case TypeAWS:
		return "AWS"
	case TypeAzure:
		return "Azure"
	default:
		return ""
	}
}

// Config defines the default parameters used in the initialization of
// provisioners.
type Config struct {
	// Claims are the default claims.
	Claims Claims
	// Audiences are the audiences used in the default provisioner, (JWK).
	Audiences Audiences
}

type provisioner struct {
	Type string `json:"type"`
}

// List represents a list of provisioners.
type List []Interface

// UnmarshalJSON implements json.Unmarshaler and allows to unmarshal a list of a
// interfaces into the right type.
func (l *List) UnmarshalJSON(data []byte) error {
	ps := []json.RawMessage{}
	if err := json.Unmarshal(data, &ps); err != nil {
		return errors.Wrap(err, "error unmarshaling provisioner list")
	}

	*l = List{}
	for _, data := range ps {
		var typ provisioner
		if err := json.Unmarshal(data, &typ); err != nil {
			return errors.Errorf("error unmarshaling provisioner")
		}
		var p Interface
		switch strings.ToLower(typ.Type) {
		case "jwk":
			p = &JWK{}
		case "oidc":
			p = &OIDC{}
		case "gcp":
			p = &GCP{}
		case "aws":
			p = &AWS{}
		case "azure":
			p = &Azure{}
		default:
			// Skip unsupported provisioners. A client using this method may be
			// compiled with a version of smallstep/certificates that does not
			// support a specific provisioner type. If we don't skip unknown
			// provisioners, a client encountering an unknown provisioner will
			// break. Rather than break the client, we skip the provisioner.
			// TODO: accept a pluggable logger (depending on client) that can
			// warn the user that an unknown provisioner was found and suggest
			// that the user update their client's dependency on
			// step/certificates and recompile.
			continue
		}
		if err := json.Unmarshal(data, p); err != nil {
			return errors.Errorf("error unmarshaling provisioner")
		}
		*l = append(*l, p)
	}

	return nil
}

var sshUserRegex = regexp.MustCompile("^[a-z][-a-z0-9_]*$")

// SanitizeSSHUserPrincipal grabs an email or a string with the format
// local@domain and returns a sanitized version of the local, valid to be used
// as a user name. If the email starts with a letter between a and z, the
// resulting string will match the regular expression `^[a-z][-a-z0-9_]*$`.
func SanitizeSSHUserPrincipal(email string) string {
	if i := strings.LastIndex(email, "@"); i >= 0 {
		email = email[:i]
	}
	return strings.Map(func(r rune) rune {
		switch {
		case r >= 'a' && r <= 'z':
			return r
		case r >= '0' && r <= '9':
			return r
		case r == '-':
			return '-'
		case r == '.': // drop dots
			return -1
		default:
			return '_'
		}
	}, strings.ToLower(email))
}