package main

// This package builds a binary which helps to generate
// private keys, public keys, certificates and also
// includes functionality to sign and verify messages.

import (
	"crypto"
	"encoding/base64"
	"fmt"
	"io"
	"io/ioutil"
	"os"

	"github.com/gibheer/pki"
)

const (
	ErrorProgram int = iota
	ErrorFlagInput
	ErrorInput
)

var (
	EmptyByteArray = make([]byte, 0)
)

func main() {
	InitFlags()
	CmdRoot.Execute()
}

// create a public key derived from a private key
func create_public_key(cmd *Command, args []string) {
	err := checkFlags(checkPrivateKey, checkOutput)
	if err != nil {
		crash_with_help(cmd, ErrorFlagInput, "Flags invalid: %s", err)
	}

	var pub_key pki.Pemmer
	pub_key = FlagPrivateKey.Public()
	marsh_pem, err := pub_key.MarshalPem()
	if err != nil {
		crash_with_help(cmd, ErrorProgram, "Error when marshalling to pem: %s", err)
	}
	_, err = marsh_pem.WriteTo(FlagOutput)
	if err != nil {
		crash_with_help(cmd, ErrorProgram, "Error when writing output: %s", err)
	}
}

// sign a message using he private key
func sign_input(cmd *Command, args []string) {
	err := checkFlags(checkPrivateKey, checkInput, checkOutput)
	if err != nil {
		crash_with_help(cmd, ErrorFlagInput, "Flags invalid: %s", err)
	}

	message, err := ioutil.ReadAll(FlagInput)
	if err != nil {
		crash_with_help(cmd, ErrorProgram, "Error reading input: %s", err)
	}
	signature, err := FlagPrivateKey.Sign(message, crypto.SHA256)
	if err != nil {
		crash_with_help(cmd, ErrorProgram, "Could not compute signature: %s", err)
	}
	_, err = io.WriteString(FlagOutput, base64.StdEncoding.EncodeToString(signature))
	if err != nil {
		crash_with_help(cmd, ErrorProgram, "Could not write to output: %s", err)
	}

	// if we print to stderr, send a final line break to make the output nice
	if FlagOutput == os.Stdout {
		// we can ignore the result, as either Stdout did work or not
		_, _ = io.WriteString(FlagOutput, "\n")
	}
}

// verify a message using a signature and a public key
func verify_input(cmd *Command, args []string) {
	err := checkFlags(checkPublicKey, checkInput, checkOutput, checkSignature)
	if err != nil {
		crash_with_help(cmd, ErrorFlagInput, "Flags invalid: %s", err)
	}

	signature := FlagSignature
	message, err := ioutil.ReadAll(FlagInput)
	if err != nil {
		crash_with_help(cmd, ErrorProgram, "Error reading input: %s", err)
	}
	valid, err := FlagPublicKey.Verify(message, signature, crypto.SHA256)
	if err != nil {
		crash_with_help(cmd, ErrorProgram, "Could not verify message using signature: %s", err)
	}
	if valid {
		fmt.Println("valid")
		os.Exit(0)
	}
	fmt.Println("invalid")
	os.Exit(1)
}

// create a certificate sign request
func create_sign_request(cmd *Command, args []string) {
	err := checkFlags(checkPrivateKey, checkOutput, checkCertificateFields)
	if err != nil {
		crash_with_help(cmd, ErrorFlagInput, "Flags invalid: %s", err)
	}

	csr, err := FlagCertificateRequestData.ToCertificateRequest(FlagPrivateKey)
	if err != nil {
		crash_with_help(cmd, ErrorProgram, "Could not create certificate sign request: %s", err)
	}
	pem_block, err := csr.MarshalPem()
	if err != nil {
		crash_with_help(cmd, ErrorProgram, "Error when marshalling to pem: %s", err)
	}
	_, err = pem_block.WriteTo(FlagOutput)
	if err != nil {
		crash_with_help(cmd, ErrorProgram, "Could not write to output: %s", err)
	}
}

// crash and provide a helpful message
func crash_with_help(cmd *Command, code int, message string, args ...interface{}) {
	fmt.Fprintf(os.Stderr, message+"\n", args...)
	cmd.Usage()
	os.Exit(code)
}

// return the arguments to the program
func program_args() []string {
	return os.Args[2:]
}