package core

import (
	"crypto"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"hash/fnv"
	"net/netip"
	"strings"
	"time"

	"github.com/go-jose/go-jose/v4"
	"golang.org/x/crypto/ocsp"

	"github.com/letsencrypt/boulder/identifier"
	"github.com/letsencrypt/boulder/probs"
	"github.com/letsencrypt/boulder/revocation"
)

// AcmeStatus defines the state of a given authorization
type AcmeStatus string

// These statuses are the states of authorizations, challenges, and registrations
const (
	StatusUnknown     = AcmeStatus("unknown")     // Unknown status; the default
	StatusPending     = AcmeStatus("pending")     // In process; client has next action
	StatusProcessing  = AcmeStatus("processing")  // In process; server has next action
	StatusReady       = AcmeStatus("ready")       // Order is ready for finalization
	StatusValid       = AcmeStatus("valid")       // Object is valid
	StatusInvalid     = AcmeStatus("invalid")     // Validation failed
	StatusRevoked     = AcmeStatus("revoked")     // Object no longer valid
	StatusDeactivated = AcmeStatus("deactivated") // Object has been deactivated
)

// AcmeChallenge values identify different types of ACME challenges
type AcmeChallenge string

// These types are the available challenges
const (
	ChallengeTypeHTTP01       = AcmeChallenge("http-01")
	ChallengeTypeDNS01        = AcmeChallenge("dns-01")
	ChallengeTypeTLSALPN01    = AcmeChallenge("tls-alpn-01")
	ChallengeTypeDNSAccount01 = AcmeChallenge("dns-account-01")
)

// IsValid tests whether the challenge is a known challenge
func (c AcmeChallenge) IsValid() bool {
	switch c {
	case ChallengeTypeHTTP01, ChallengeTypeDNS01, ChallengeTypeTLSALPN01, ChallengeTypeDNSAccount01:
		return true
	default:
		return false
	}
}

// OCSPStatus defines the state of OCSP for a certificate
type OCSPStatus string

// These status are the states of OCSP
const (
	OCSPStatusGood    = OCSPStatus("good")
	OCSPStatusRevoked = OCSPStatus("revoked")
)

var OCSPStatusToInt = map[OCSPStatus]int{
	OCSPStatusGood:    ocsp.Good,
	OCSPStatusRevoked: ocsp.Revoked,
}

// DNSPrefix is attached to DNS names in DNS challenges
const DNSPrefix = "_acme-challenge"

type RawCertificateRequest struct {
	CSR JSONBuffer `json:"csr"` // The encoded CSR
}

// Registration objects represent non-public metadata attached
// to account keys.
type Registration struct {
	// Unique identifier
	ID int64 `json:"-"`

	// Account key to which the details are attached
	Key *jose.JSONWebKey `json:"key"`

	// Contact URIs
	Contact *[]string `json:"contact,omitempty"`

	// Agreement with terms of service
	Agreement string `json:"-"`

	// CreatedAt is the time the registration was created.
	CreatedAt *time.Time `json:"createdAt,omitempty"`

	Status AcmeStatus `json:"status"`
}

// ValidationRecord represents a validation attempt against a specific URL/hostname
// and the IP addresses that were resolved and used.
type ValidationRecord struct {
	// SimpleHTTP only
	URL string `json:"url,omitempty"`

	// Shared
	//
	// Hostname can hold either a DNS name or an IP address.
	Hostname          string       `json:"hostname,omitempty"`
	Port              string       `json:"port,omitempty"`
	AddressesResolved []netip.Addr `json:"addressesResolved,omitempty"`
	AddressUsed       netip.Addr   `json:"addressUsed"`

	// AddressesTried contains a list of addresses tried before the `AddressUsed`.
	// Presently this will only ever be one IP from `AddressesResolved` since the
	// only retry is in the case of a v6 failure with one v4 fallback. E.g. if
	// a record with `AddressesResolved: { 127.0.0.1, ::1 }` were processed for
	// a challenge validation with the IPv6 first flag on and the ::1 address
	// failed but the 127.0.0.1 retry succeeded then the record would end up
	// being:
	// {
	//   ...
	//   AddressesResolved: [ 127.0.0.1, ::1 ],
	//   AddressUsed: 127.0.0.1
	//   AddressesTried: [ ::1 ],
	//   ...
	// }
	AddressesTried []netip.Addr `json:"addressesTried,omitempty"`

	// ResolverAddrs is the host:port of the DNS resolver(s) that fulfilled the
	// lookup for AddressUsed. During recursive A and AAAA lookups, a record may
	// instead look like A:host:port or AAAA:host:port
	ResolverAddrs []string `json:"resolverAddrs,omitempty"`
}

// Challenge is an aggregate of all data needed for any challenges.
//
// Rather than define individual types for different types of
// challenge, we just throw all the elements into one bucket,
// together with the common metadata elements.
type Challenge struct {
	// Type is the type of challenge encoded in this object.
	Type AcmeChallenge `json:"type"`

	// URL is the URL to which a response can be posted. Required for all types.
	URL string `json:"url,omitempty"`

	// Status is the status of this challenge. Required for all types.
	Status AcmeStatus `json:"status,omitempty"`

	// Validated is the time at which the server validated the challenge. Required
	// if status is valid.
	Validated *time.Time `json:"validated,omitempty"`

	// Error contains the error that occurred during challenge validation, if any.
	// If set, the Status must be "invalid".
	Error *probs.ProblemDetails `json:"error,omitempty"`

	// Token is a random value that uniquely identifies the challenge. It is used
	// by all current challenges (http-01, tls-alpn-01, and dns-01).
	Token string `json:"token,omitempty"`

	// Contains information about URLs used or redirected to and IPs resolved and
	// used
	ValidationRecord []ValidationRecord `json:"validationRecord,omitempty"`
}

// ExpectedKeyAuthorization computes the expected KeyAuthorization value for
// the challenge.
func (ch Challenge) ExpectedKeyAuthorization(key *jose.JSONWebKey) (string, error) {
	if key == nil {
		return "", fmt.Errorf("Cannot authorize a nil key")
	}

	thumbprint, err := key.Thumbprint(crypto.SHA256)
	if err != nil {
		return "", err
	}

	return ch.Token + "." + base64.RawURLEncoding.EncodeToString(thumbprint), nil
}

// RecordsSane checks the sanity of a ValidationRecord object before sending it
// back to the RA to be stored.
func (ch Challenge) RecordsSane() bool {
	if len(ch.ValidationRecord) == 0 {
		return false
	}

	switch ch.Type {
	case ChallengeTypeHTTP01:
		for _, rec := range ch.ValidationRecord {
			// TODO(#7140): Add a check for ResolverAddress == "" only after the
			// core.proto change has been deployed.
			if rec.URL == "" || rec.Hostname == "" || rec.Port == "" || (rec.AddressUsed == netip.Addr{}) ||
				len(rec.AddressesResolved) == 0 {
				return false
			}
		}
	case ChallengeTypeTLSALPN01:
		if len(ch.ValidationRecord) > 1 {
			return false
		}
		if ch.ValidationRecord[0].URL != "" {
			return false
		}
		// TODO(#7140): Add a check for ResolverAddress == "" only after the
		// core.proto change has been deployed.
		if ch.ValidationRecord[0].Hostname == "" || ch.ValidationRecord[0].Port == "" ||
			(ch.ValidationRecord[0].AddressUsed == netip.Addr{}) || len(ch.ValidationRecord[0].AddressesResolved) == 0 {
			return false
		}
	case ChallengeTypeDNS01, ChallengeTypeDNSAccount01:
		if len(ch.ValidationRecord) > 1 {
			return false
		}
		// TODO(#7140): Add a check for ResolverAddress == "" only after the
		// core.proto change has been deployed.
		if ch.ValidationRecord[0].Hostname == "" {
			return false
		}
		return true
	default: // Unsupported challenge type
		return false
	}

	return true
}

// CheckPending ensures that a challenge object is pending and has a token.
// This is used before offering the challenge to the client, and before actually
// validating a challenge.
func (ch Challenge) CheckPending() error {
	if ch.Status != StatusPending {
		return fmt.Errorf("challenge is not pending")
	}

	if !looksLikeAToken(ch.Token) {
		return fmt.Errorf("token is missing or malformed")
	}

	return nil
}

// StringID is used to generate a ID for challenges associated with new style authorizations.
// This is necessary as these challenges no longer have a unique non-sequential identifier
// in the new storage scheme. This identifier is generated by constructing a fnv hash over the
// challenge token and type and encoding the first 4 bytes of it using the base64 URL encoding.
func (ch Challenge) StringID() string {
	h := fnv.New128a()
	h.Write([]byte(ch.Token))
	h.Write([]byte(ch.Type))
	return base64.RawURLEncoding.EncodeToString(h.Sum(nil)[0:4])
}

// Authorization represents the authorization of an account key holder to act on
// behalf of an identifier. This struct is intended to be used both internally
// and for JSON marshaling on the wire. Any fields that should be suppressed on
// the wire (e.g., ID, regID) must be made empty before marshaling.
type Authorization struct {
	// An identifier for this authorization, unique across
	// authorizations and certificates within this instance.
	ID string `json:"-"`

	// The identifier for which authorization is being given
	Identifier identifier.ACMEIdentifier `json:"identifier"`

	// The registration ID associated with the authorization
	RegistrationID int64 `json:"-"`

	// The status of the validation of this authorization
	Status AcmeStatus `json:"status,omitempty"`

	// The date after which this authorization will be no
	// longer be considered valid. Note: a certificate may be issued even on the
	// last day of an authorization's lifetime. The last day for which someone can
	// hold a valid certificate based on an authorization is authorization
	// lifetime + certificate lifetime.
	Expires *time.Time `json:"expires,omitempty"`

	// An array of challenges objects used to validate the
	// applicant's control of the identifier.  For authorizations
	// in process, these are challenges to be fulfilled; for
	// final authorizations, they describe the evidence that
	// the server used in support of granting the authorization.
	//
	// There should only ever be one challenge of each type in this
	// slice and the order of these challenges may not be predictable.
	Challenges []Challenge `json:"challenges,omitempty"`

	// https://datatracker.ietf.org/doc/html/rfc8555#page-29
	//
	// wildcard (optional, boolean):  This field MUST be present and true
	//   for authorizations created as a result of a newOrder request
	//   containing a DNS identifier with a value that was a wildcard
	//   domain name.  For other authorizations, it MUST be absent.
	//   Wildcard domain names are described in Section 7.1.3.
	//
	// This is not represented in the database because we calculate it from
	// the identifier stored in the database. Unlike the identifier returned
	// as part of the authorization, the identifier we store in the database
	// can contain an asterisk.
	Wildcard bool `json:"wildcard,omitempty"`

	// CertificateProfileName is the name of the profile associated with the
	// order that first resulted in the creation of this authorization. Omitted
	// from API responses.
	CertificateProfileName string `json:"-"`
}

// FindChallengeByStringID will look for a challenge matching the given ID inside
// this authorization. If found, it will return the index of that challenge within
// the Authorization's Challenges array. Otherwise it will return -1.
func (authz *Authorization) FindChallengeByStringID(id string) int {
	for i, c := range authz.Challenges {
		if c.StringID() == id {
			return i
		}
	}
	return -1
}

// SolvedBy will look through the Authorizations challenges, returning the type
// of the *first* challenge it finds with Status: valid, or an error if no
// challenge is valid.
func (authz *Authorization) SolvedBy() (AcmeChallenge, error) {
	if len(authz.Challenges) == 0 {
		return "", fmt.Errorf("authorization has no challenges")
	}
	for _, chal := range authz.Challenges {
		if chal.Status == StatusValid {
			return chal.Type, nil
		}
	}
	return "", fmt.Errorf("authorization not solved by any challenge")
}

// JSONBuffer fields get encoded and decoded JOSE-style, in base64url encoding
// with stripped padding.
type JSONBuffer []byte

// MarshalJSON encodes a JSONBuffer for transmission.
func (jb JSONBuffer) MarshalJSON() (result []byte, err error) {
	return json.Marshal(base64.RawURLEncoding.EncodeToString(jb))
}

// UnmarshalJSON decodes a JSONBuffer to an object.
func (jb *JSONBuffer) UnmarshalJSON(data []byte) (err error) {
	var str string
	err = json.Unmarshal(data, &str)
	if err != nil {
		return err
	}
	*jb, err = base64.RawURLEncoding.DecodeString(strings.TrimRight(str, "="))
	return
}

// Certificate objects are entirely internal to the server.  The only
// thing exposed on the wire is the certificate itself.
type Certificate struct {
	ID             int64 `db:"id"`
	RegistrationID int64 `db:"registrationID"`

	Serial  string    `db:"serial"`
	Digest  string    `db:"digest"`
	DER     []byte    `db:"der"`
	Issued  time.Time `db:"issued"`
	Expires time.Time `db:"expires"`
}

// CertificateStatus structs are internal to the server. They represent the
// latest data about the status of the certificate, required for generating new
// OCSP responses and determining if a certificate has been revoked.
type CertificateStatus struct {
	ID int64 `db:"id"`

	Serial string `db:"serial"`

	// status: 'good' or 'revoked'. Note that good, expired certificates remain
	// with status 'good' but don't necessarily get fresh OCSP responses.
	Status OCSPStatus `db:"status"`

	// ocspLastUpdated: The date and time of the last time we generated an OCSP
	// response. If we have never generated one, this has the zero value of
	// time.Time, i.e. Jan 1 1970.
	OCSPLastUpdated time.Time `db:"ocspLastUpdated"`

	// revokedDate: If status is 'revoked', this is the date and time it was
	// revoked. Otherwise it has the zero value of time.Time, i.e. Jan 1 1970.
	RevokedDate time.Time `db:"revokedDate"`

	// revokedReason: If status is 'revoked', this is the reason code for the
	// revocation. Otherwise it is zero (which happens to be the reason
	// code for 'unspecified').
	RevokedReason revocation.Reason `db:"revokedReason"`

	LastExpirationNagSent time.Time `db:"lastExpirationNagSent"`

	// NotAfter and IsExpired are convenience columns which allow expensive
	// queries to quickly filter out certificates that we don't need to care
	// about anymore. These are particularly useful for the CRL updater. See
	// https://github.com/letsencrypt/boulder/issues/1864.
	NotAfter  time.Time `db:"notAfter"`
	IsExpired bool      `db:"isExpired"`

	// Note: this is not an issuance.IssuerNameID because that would create an
	// import cycle between core and issuance.
	// Note2: This field used to be called `issuerID`. We keep the old name in
	// the DB, but update the Go field name to be clear which type of ID this
	// is.
	IssuerNameID int64 `db:"issuerID"`
}

// SCTDERs is a convenience type
type SCTDERs [][]byte

// CertDER is a convenience type that helps differentiate what the
// underlying byte slice contains
type CertDER []byte

// SuggestedWindow is a type exposed inside the RenewalInfo resource.
type SuggestedWindow struct {
	Start time.Time `json:"start"`
	End   time.Time `json:"end"`
}

// IsWithin returns true if the given time is within the suggested window,
// inclusive of the start time and exclusive of the end time.
func (window SuggestedWindow) IsWithin(now time.Time) bool {
	return !now.Before(window.Start) && now.Before(window.End)
}

// RenewalInfo is a type which is exposed to clients which query the renewalInfo
// endpoint specified in draft-aaron-ari.
type RenewalInfo struct {
	SuggestedWindow SuggestedWindow `json:"suggestedWindow"`
	ExplanationURL  string          `json:"explanationURL,omitempty"`
}

// RenewalInfoSimple constructs a `RenewalInfo` object and suggested window
// using a very simple renewal calculation: calculate a point 2/3rds of the way
// through the validity period (or halfway through, for short-lived certs), then
// give a 2%-of-validity wide window around that. Both the `issued` and
// `expires` timestamps are expected to be UTC.
func RenewalInfoSimple(issued time.Time, expires time.Time) RenewalInfo {
	validity := expires.Add(time.Second).Sub(issued)
	renewalOffset := validity / time.Duration(3)
	if validity < 10*24*time.Hour {
		renewalOffset = validity / time.Duration(2)
	}
	idealRenewal := expires.Add(-renewalOffset)
	margin := validity / time.Duration(100)
	return RenewalInfo{
		SuggestedWindow: SuggestedWindow{
			Start: idealRenewal.Add(-1 * margin).Truncate(time.Second),
			End:   idealRenewal.Add(margin).Truncate(time.Second),
		},
	}
}

// RenewalInfoImmediate constructs a `RenewalInfo` object with a suggested
// window in the past. Per the draft-ietf-acme-ari-01 spec, clients should
// attempt to renew immediately if the suggested window is in the past. The
// passed `now` is assumed to be a timestamp representing the current moment in
// time. The `explanationURL` is an optional URL that the subscriber can use to
// learn more about why the renewal is suggested.
func RenewalInfoImmediate(now time.Time, explanationURL string) RenewalInfo {
	oneHourAgo := now.Add(-1 * time.Hour)
	return RenewalInfo{
		SuggestedWindow: SuggestedWindow{
			Start: oneHourAgo.Truncate(time.Second),
			End:   oneHourAgo.Add(time.Minute * 30).Truncate(time.Second),
		},
		ExplanationURL: explanationURL,
	}
}
