package jwt

import (
	"fmt"
	"time"
)

// Claims must just have a Valid method that determines
// if the token is invalid for any supported reason
type Claims interface {
	Valid() error
}

// RegisteredClaims are a structured version of the JWT Claims Set,
// restricted to Registered Claim Names, as referenced at
// https://datatracker.ietf.org/doc/html/rfc7519#section-4.1
//
// This type can be used on its own, but then additional private and
// public claims embedded in the JWT will not be parsed. The typical usecase
// therefore is to embedded this in a user-defined claim type.
//
// See examples for how to use this with your own claim types.
type RegisteredClaims struct {
	// the `iss` (Issuer) claim. See https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.1
	Issuer string `json:"iss,omitempty"`

	// the `sub` (Subject) claim. See https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.2
	Subject string `json:"sub,omitempty"`

	// the `aud` (Audience) claim. See https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.3
	Audience ClaimStrings `json:"aud,omitempty"`

	// the `exp` (Expiration Time) claim. See https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.4
	ExpiresAt *NumericDate `json:"exp,omitempty"`

	// the `nbf` (Not Before) claim. See https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.5
	NotBefore *NumericDate `json:"nbf,omitempty"`

	// the `iat` (Issued At) claim. See https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.6
	IssuedAt *NumericDate `json:"iat,omitempty"`

	// the `jti` (JWT ID) claim. See https://datatracker.ietf.org/doc/html/rfc7519#section-4.1.7
	ID string `json:"jti,omitempty"`
}

func (c RegisteredClaims) GetExpiryAt() *NumericDate {
	return c.ExpiresAt
}

func (c RegisteredClaims) GetNotBefore() *NumericDate {
	return c.NotBefore
}

func (c RegisteredClaims) GetIssuedAt() *NumericDate {
	return c.IssuedAt
}

func (c RegisteredClaims) GetAudience() ClaimStrings {
	return c.Audience
}

func (c RegisteredClaims) GetIssuer() string {
	return c.Issuer
}

// Valid validates time based claims "exp, iat, nbf".
// There is no accounting for clock skew.
// As well, if any of the above claims are not in the token, it will still
// be considered a valid claim.
//
// Deprecated: This function should not be called directly, rather a claim should be validated using
// the Validator struct.
func (c RegisteredClaims) Valid() error {
	return NewValidator().Validate(c)
}

// VerifyAudience compares the aud claim against cmp.
// If required is false, this method will return true if the value matches or is unset
func (c *RegisteredClaims) VerifyAudience(cmp string, req bool) bool {
	return NewValidator().VerifyAudience(c, cmp, req)
}

// VerifyExpiresAt compares the exp claim against cmp (cmp < exp).
// If req is false, it will return true, if exp is unset.
func (c *RegisteredClaims) VerifyExpiresAt(cmp time.Time, req bool) bool {
	return NewValidator().VerifyExpiresAt(c, cmp, req)
}

// VerifyIssuedAt compares the iat claim against cmp (cmp >= iat).
// If req is false, it will return true, if iat is unset.
func (c *RegisteredClaims) VerifyIssuedAt(cmp time.Time, req bool) bool {
	return NewValidator().VerifyIssuedAt(c, cmp, req)
}

// VerifyNotBefore compares the nbf claim against cmp (cmp >= nbf).
// If req is false, it will return true, if nbf is unset.
func (c *RegisteredClaims) VerifyNotBefore(cmp time.Time, req bool) bool {
	return NewValidator().VerifyNotBefore(c, cmp, req)
}

// VerifyIssuer compares the iss claim against cmp.
// If required is false, this method will return true if the value matches or is unset
func (c *RegisteredClaims) VerifyIssuer(cmp string, req bool) bool {
	return NewValidator().VerifyIssuer(c, cmp, req)
}

// StandardClaims are a structured version of the JWT Claims Set, as referenced at
// https://datatracker.ietf.org/doc/html/rfc7519#section-4. They do not follow the
// specification exactly, since they were based on an earlier draft of the
// specification and not updated. The main difference is that they only
// support integer-based date fields and singular audiences. This might lead to
// incompatibilities with other JWT implementations. The use of this is discouraged, instead
// the newer RegisteredClaims struct should be used.
//
// Deprecated: Use RegisteredClaims instead for a forward-compatible way to access registered claims in a struct.
type StandardClaims struct {
	Audience  string `json:"aud,omitempty"`
	ExpiresAt int64  `json:"exp,omitempty"`
	Id        string `json:"jti,omitempty"`
	IssuedAt  int64  `json:"iat,omitempty"`
	Issuer    string `json:"iss,omitempty"`
	NotBefore int64  `json:"nbf,omitempty"`
	Subject   string `json:"sub,omitempty"`
}

// Valid validates time based claims "exp, iat, nbf". There is no accounting for clock skew.
// As well, if any of the above claims are not in the token, it will still
// be considered a valid claim.
func (c StandardClaims) Valid() error {
	vErr := new(ValidationError)
	now := TimeFunc().Unix()

	// The claims below are optional, by default, so if they are set to the
	// default value in Go, let's not fail the verification for them.
	if !c.VerifyExpiresAt(now, false) {
		delta := time.Unix(now, 0).Sub(time.Unix(c.ExpiresAt, 0))
		vErr.Inner = fmt.Errorf("%s by %s", ErrTokenExpired, delta)
		vErr.Errors |= ValidationErrorExpired
	}

	if !c.VerifyIssuedAt(now, false) {
		vErr.Inner = ErrTokenUsedBeforeIssued
		vErr.Errors |= ValidationErrorIssuedAt
	}

	if !c.VerifyNotBefore(now, false) {
		vErr.Inner = ErrTokenNotValidYet
		vErr.Errors |= ValidationErrorNotValidYet
	}

	if vErr.valid() {
		return nil
	}

	return vErr
}

// VerifyAudience compares the aud claim against cmp.
// If required is false, this method will return true if the value matches or is unset
func (c *StandardClaims) VerifyAudience(cmp string, req bool) bool {
	return verifyAud([]string{c.Audience}, cmp, req)
}

// VerifyExpiresAt compares the exp claim against cmp (cmp < exp).
// If req is false, it will return true, if exp is unset.
func (c *StandardClaims) VerifyExpiresAt(cmp int64, req bool) bool {
	if c.ExpiresAt == 0 {
		return verifyExp(nil, time.Unix(cmp, 0), req, 0)
	}

	t := time.Unix(c.ExpiresAt, 0)
	return verifyExp(&t, time.Unix(cmp, 0), req, 0)
}

// VerifyIssuedAt compares the iat claim against cmp (cmp >= iat).
// If req is false, it will return true, if iat is unset.
func (c *StandardClaims) VerifyIssuedAt(cmp int64, req bool) bool {
	if c.IssuedAt == 0 {
		return verifyIat(nil, time.Unix(cmp, 0), req, 0)
	}

	t := time.Unix(c.IssuedAt, 0)
	return verifyIat(&t, time.Unix(cmp, 0), req, 0)
}

// VerifyNotBefore compares the nbf claim against cmp (cmp >= nbf).
// If req is false, it will return true, if nbf is unset.
func (c *StandardClaims) VerifyNotBefore(cmp int64, req bool) bool {
	if c.NotBefore == 0 {
		return verifyNbf(nil, time.Unix(cmp, 0), req, 0)
	}

	t := time.Unix(c.NotBefore, 0)
	return verifyNbf(&t, time.Unix(cmp, 0), req, 0)
}

// VerifyIssuer compares the iss claim against cmp.
// If required is false, this method will return true if the value matches or is unset
func (c *StandardClaims) VerifyIssuer(cmp string, req bool) bool {
	return verifyIss(c.Issuer, cmp, req)
}