package main

// This file handles the complete parameter assignment, as some parameters are
// often used by multiple functions.

import (
  "crypto/elliptic"
  "encoding/base64"
  "encoding/pem"
  "fmt"
  "io"
  "io/ioutil"
  "net"
  "os"
  "reflect"
  "strings"

  "github.com/gibheer/pki"
)

const (
  RsaLowerLength = 2048
  RsaUpperLength = 16384
)

var (
  EcdsaCurves    = []int{224, 256, 384, 521}
)

type (
  // holds all certificate related flags, which need parsing afterwards
  certFlagsContainer struct {
    manual struct {
      serialNumber   string // the serial number for the cert
      commonName     string // the common name used in the cert
      dnsNames       string // all alternative names in the certificate (comma separated list)
      ipAddresses    string // all IP addresses in the certificate (comma separated list)
      emailAddresses string // alternative email addresses
    }
    automatic struct {
      Country       string // the country names which should end up in the cert (comma separated list)
      Organization  string // the organization names (comma separated list)
      OrganizationalUnit string // the organizational units (comma separated list)
      Locality      string // the city or locality (comma separated list)
      Province      string // the province name (comma separated list)
      StreetAddress string // the street addresses of the organization (comma separated list)
      PostalCode    string // the postal codes of the locality
    }
  }

  // a container go gather all incoming flags for further processing
  paramContainer struct {
    outputPath       string // path to output whatever is generated
    inputPath        string // path to an input resource
    cryptType        string // type of something (private key)
    length           int    // the length of something (private key)
    privateKeyPath   string // path to the private key
    publicKeyPath    string // path to the public key
    signRequestPath  string // path to the certificate sign request
    certificateFlags certFlagsContainer // container for certificate related flags
    signature        string // a base64 encoded signature
  }

  privateKeyGenerationFlags struct {
    Type string // type of the private key (rsa, ecdsa)
    Curve elliptic.Curve // curve for ecdsa
    Size  int            // bitsize for rsa
  }

  flagCheck func()(error)
)

var (
  CmdRoot = &Command {
    Short: "A tool to manage keys and certificates.",
    Long: `This tool provides a way to manage private and public keys, create
certificate requests and certificates and sign/verify messages.`,
  }

  CmdCreatePrivateKey = &Command {
    Use: "create-private",
    Short: "create a private key",
    Long: "Create an ecdsa or rsa key with this command",
    Example: "create-private -type=ecdsa -length=521",
    Run: create_private_key,
  }

  CmdCreatePublicKey = &Command {
    Use: "create-public",
    Short: "create a public key from a private key",
    Long: "Create a public key derived from a private key.",
    Example: "create-public -private-key=foo.ecdsa",
    Run: create_public_key,
  }

  CmdSignInput = &Command {
    Use: "sign-input",
    Short: "sign a text using a private key",
    Long: "Create a signature using a private key",
    Example: "sign-input -private-key=foo.ecdsa -input=textfile",
    Run: sign_input,
  }

  CmdVerifyInput = &Command {
    Use: "verify-input",
    Short: "verify a text using a signature",
    Long: "Verify a text using a signature and a public key.",
    Example: "verify-input -public-key=foo.ecdsa.pub -input=textfile -signature=abc456",
    Run: verify_input,
  }

  CmdCreateSignRequest = &Command {
    Use: "create-sign-request",
    Short: "create a certificate sign request",
    Long: "Create a certificate sign request.",
    Example: "create-sign-request -private-key=foo.ecdsa -common-name=foo -serial=1",
    Run: create_sign_request,
  }

  CmdCreateCert = &Command {
    Use: "create-cert",
    Short: "create a certificate from a sign request",
    Long: "Create a certificate based on a certificate sign request.",
    Example: "create-cert -private-key=foo.ecdsa -csr-path=foo.csr",
    Run: create_cert,
  }

  // variable to hold the raw arguments before checking
  flagContainer *paramContainer

  // loaded private key
  FlagPrivateKey pki.PrivateKey
  // loaded public key
  FlagPublicKey  pki.PublicKey
  // the IO handler for input
  FlagInput      io.ReadCloser
  // the IO handler for output
  FlagOutput     io.WriteCloser
  // signature from the args
  FlagSignature  []byte
  // private key specific stuff
  FlagPrivateKeyGeneration privateKeyGenerationFlags
  // a certificate filled with the parameters
  FlagCertificateData *pki.CertificateData
  // the certificate sign request
  FlagCertificateSignRequest *pki.CertificateRequest
)

func InitFlags() {
  flagContainer = &paramContainer{}
  CmdRoot.AddCommand(
    CmdCreatePrivateKey,
    CmdCreatePublicKey,
    CmdSignInput,
    CmdVerifyInput,
    CmdCreateSignRequest,
    CmdCreateCert,
  )

  // private-key
  InitFlagOutput(CmdCreatePrivateKey)
  InitFlagPrivateKeyGeneration(CmdCreatePrivateKey)
  // public-key
  InitFlagOutput(CmdCreatePublicKey)
  InitFlagPrivateKey(CmdCreatePublicKey)
  // sign-input
  InitFlagInput(CmdSignInput)
  InitFlagPrivateKey(CmdSignInput)
  InitFlagOutput(CmdSignInput)
  // verify-input
  InitFlagInput(CmdVerifyInput)
  InitFlagPrivateKey(CmdVerifyInput)
  InitFlagOutput(CmdVerifyInput)
  InitFlagSignature(CmdVerifyInput)
  // create-sign-request
  InitFlagPrivateKey(CmdCreateSignRequest)
  InitFlagOutput(CmdCreateSignRequest)
  InitFlagCertificateFields(CmdCreateSignRequest)
  // create-certificate
  InitFlagPrivateKey(CmdCreateCert)
  InitFlagOutput(CmdCreateCert)
  InitFlagCSR(CmdCreateCert)
}

func checkFlags(checks... flagCheck) error {
  for _, check := range checks {
    if err := check(); err != nil {
      return err
    }
  }
  return nil
}

//// print a message with the usage part
//func (f *Flags) Usagef(message string, args ...interface{}) {
//  fmt.Fprintf(os.Stderr, "error: " + message + "\n", args...)
//  f.flagset.Flags().Usage()
//}

// add the private key option to the requested flags
func InitFlagPrivateKey(cmd *Command) {
  cmd.Flags().StringVar(&flagContainer.privateKeyPath, "private-key", "", "path to the private key (required)")
}

// check the private key flag and load the private key
func checkPrivateKey() error {
  if flagContainer.privateKeyPath == "" { return fmt.Errorf("No private key given!") }
  // check permissions of private key file
  info, err := os.Stat(flagContainer.privateKeyPath)
  if err != nil { return fmt.Errorf("Error reading private key: %s", err) }
  if info.Mode().Perm().String()[4:] != "------" {
    return fmt.Errorf("private key file modifyable by others!")
  }

  pk, err := ReadPrivateKeyFile(flagContainer.privateKeyPath)
  if err != nil { return fmt.Errorf("Error reading private key: %s", err) }
  FlagPrivateKey = pk
  return nil
}

// add the public key flag
func InitFlagPublicKey(cmd *Command) {
  cmd.Flags().StringVar(&flagContainer.publicKeyPath, "public-key", "", "path to the public key (required)")
}

// parse public key flag
func checkPublicKey() error {
  if flagContainer.publicKeyPath == "" { return fmt.Errorf("No public key given!") }

  pu, err := ReadPublicKeyFile(flagContainer.publicKeyPath)
  if err != nil { return fmt.Errorf("Error reading public key: %s", err) }
  FlagPublicKey = pu
  return nil
}

// add flag to load certificate sign request
func InitFlagCSR(cmd *Command) {
  cmd.Flags().StringVar(&flagContainer.signRequestPath, "csr-path", "", "path to the certificate sign request")
}

// parse the certificate sign request
func checkCSR() error {
  rest, err := ioutil.ReadFile(flagContainer.signRequestPath)
  if err != nil { return fmt.Errorf("Error reading certificate sign request: %s", err) }

  var csr_asn1 []byte
  var block *pem.Block
  for len(rest) > 0 {
    block, rest = pem.Decode(rest)
    if block.Type == "CERTIFICATE REQUEST" {
      csr_asn1 = block.Bytes
      break
    }
  }
  if len(csr_asn1) == 0 {
    return fmt.Errorf(
      "No certificate sign request found in %s",
      flagContainer.signRequestPath,
    )
  }

  csr, err := pki.LoadCertificateSignRequest(csr_asn1)
  if err != nil { return fmt.Errorf("Invalid certificate sign request: %s", err) }
  FlagCertificateSignRequest = csr
  return nil
}

func InitFlagOutput(cmd *Command) {
  cmd.Flags().StringVar(&flagContainer.outputPath, "output", "STDOUT", "path to the output or STDOUT")
}

// parse the output parameter and open the file handle
func checkOutput() error {
  if flagContainer.outputPath == "STDOUT" {
    FlagOutput = os.Stdout
    return nil
  }
  var err error
  FlagOutput, err = os.OpenFile(
    flagContainer.outputPath,
    os.O_WRONLY | os.O_APPEND | os.O_CREATE, // do not kill users files!
    0600,
  )
  if err != nil { return err }
  return nil
}

// add the input parameter to load resources from
func InitFlagInput(cmd *Command) {
  cmd.Flags().StringVar(&flagContainer.inputPath, "input", "STDIN", "path to the input or STDIN")
}

// parse the input parameter and open the file handle
func checkInput() error {
  if flagContainer.inputPath == "STDIN" {
    FlagInput = os.Stdin
    return nil
  }
  var err error
  FlagInput, err = os.Open(flagContainer.inputPath)
  if err != nil { return err }
  return nil
}

// This function adds the private key generation flags.
func InitFlagPrivateKeyGeneration(cmd *Command) {
  cmd.Flags().StringVar(&flagContainer.cryptType, "type", "ecdsa", "the type of the private key (ecdsa, rsa)")
  cmd.Flags().IntVar(
    &flagContainer.length,
    "length", 521,
    fmt.Sprintf("%d - %d for rsa; one of %v for ecdsa", RsaLowerLength, RsaUpperLength, EcdsaCurves),
  )
}

// check the private key generation variables and move them to the work space
func checkPrivateKeyGeneration() error {
  pk_type := flagContainer.cryptType
  FlagPrivateKeyGeneration.Type = pk_type
  switch pk_type {
  case "ecdsa":
    switch flagContainer.length {
    case 224: FlagPrivateKeyGeneration.Curve = elliptic.P224()
    case 256: FlagPrivateKeyGeneration.Curve = elliptic.P256()
    case 384: FlagPrivateKeyGeneration.Curve = elliptic.P384()
    case 521: FlagPrivateKeyGeneration.Curve = elliptic.P521()
    default: return fmt.Errorf("Curve %d unknown!", flagContainer.length)
    }
  case "rsa":
    size := flagContainer.length
    if RsaLowerLength <= size && size <= RsaUpperLength {
      FlagPrivateKeyGeneration.Size = size
    } else {
      return fmt.Errorf("Length of %d is not allowed for rsa!", size)
    }
  default: return fmt.Errorf("Type %s is unknown!", pk_type)
  }
  return nil
}

// add the signature flag to load a signature from a signing process
func InitFlagSignature(cmd *Command) {
  cmd.Flags().StringVar(&flagContainer.signature, "signature", "", "the base64 encoded signature to use for verification")
}

// parse the signature flag
func checkSignature() error {
  var err error
  FlagSignature, err = base64.StdEncoding.DecodeString(flagContainer.signature)
  if err != nil { return err }
  return nil
}

// add the certificate fields to the flags
func InitFlagCertificateFields(cmd *Command) {
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.manual.serialNumber,
    "serial", "1", "unique serial number of the CA");
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.manual.commonName,
    "common-name", "", "common name of the entity to certify");
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.manual.dnsNames,
    "dns-names", "", "comma separated list of alternative fqdn entries for the entity");
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.manual.emailAddresses,
    "email-address", "", "comma separated list of alternative email entries for the entity");
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.manual.ipAddresses,
    "ip-address", "", "comma separated list of alternative ip entries for the entity");
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.automatic.Country,
    "country", "", "comma separated list of countries the entitiy resides in");
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.automatic.Organization,
    "organization", "", "comma separated list of organizations the entity belongs to");
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.automatic.OrganizationalUnit,
    "organization-unit", "", "comma separated list of organization units or departments the entity belongs to");
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.automatic.Locality,
    "locality", "", "comma separated list of localities or cities the entity resides in");
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.automatic.Province,
    "province", "", "comma separated list of provinces the entity resides in");
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.automatic.StreetAddress,
    "street-address", "", "comma separated list of street addresses the entity resides in");
  cmd.Flags().StringVar(
    &flagContainer.certificateFlags.automatic.PostalCode,
    "postal-code", "", "comma separated list of postal codes of the localities");
}

// parse the certificate fields into a raw certificate
func checkCertificateFields() error {
  FlagCertificateData = pki.NewCertificateData()
  // convert the automatic flags
  container_type := reflect.ValueOf(&flagContainer.certificateFlags.automatic).Elem()
  cert_data_type := reflect.ValueOf(&FlagCertificateData.Subject).Elem()

  for _, field := range []string{"Country", "Organization", "OrganizationalUnit",
                                 "Locality", "Province", "StreetAddress", "PostalCode"} {
    field_value := container_type.FieldByName(field).String()
    if field_value == "" { continue }
    target := cert_data_type.FieldByName(field)
    target.Set(reflect.ValueOf(strings.Split(field_value, ",")))
  }

  // convert the manual flags
  data     := FlagCertificateData
  raw_data := flagContainer.certificateFlags.manual
  data.Subject.SerialNumber = raw_data.serialNumber
  data.Subject.CommonName   = raw_data.commonName
  if raw_data.dnsNames != "" {
    data.DNSNames             = strings.Split(raw_data.dnsNames, ",")
  }
  if raw_data.emailAddresses != "" {
    data.EmailAddresses       = strings.Split(raw_data.emailAddresses, ",")
  }

  if raw_data.ipAddresses == "" { return nil }
  raw_ips := strings.Split(raw_data.ipAddresses, ",")
  data.IPAddresses = make([]net.IP, len(raw_ips))
  for i, ip := range raw_ips {
    data.IPAddresses[i] = net.ParseIP(ip)
    if data.IPAddresses[i] == nil {
      return fmt.Errorf("'%s' is not a valid IP", ip)
    }
  }

  return nil
}