package inspect

import (
	"crypto/rsa"
	"crypto/x509"
	"errors"
)

// PKCS1PrivateKeyInfo attempts to parse a DER-form PKCS#1-encoded private RSA
// key, and returns information about it.
func PKCS1PrivateKeyInfo(loc string, der []byte) Info {
	key, err := x509.ParsePKCS1PrivateKey(der)
	if err != nil {
		return &BadInfo{
			Typ:        TypePrivateKey,
			Loc:        loc,
			Underlying: err,
		}
	}

	return PrivateKeyInfo(loc, key)
}

// PKCS1PrivateKeyInfo attempts to parse a DER-form PKCS#8-encoded private RSA
// key, and returns information about it.
func PKCS8PrivateKeyInfo(loc string, der []byte) Info {
	key, err := x509.ParsePKCS8PrivateKey(der)
	if err != nil {
		return &BadInfo{
			Typ:        TypePrivateKey,
			Loc:        loc,
			Underlying: err,
		}
	}

	rsakey, ok := key.(*rsa.PrivateKey)
	if !ok {
		return &BadInfo{
			Typ:        TypePrivateKey,
			Underlying: errors.New("PKCS#8 private key ytpe is not RSA"),
		}
	}

	return PrivateKeyInfo(loc, rsakey)
}

// PrivateKeyInfo returns structured information about the given RSA private key.
func PrivateKeyInfo(loc string, key *rsa.PrivateKey) *PrivateKey {
	pl := make([]int, len(key.Primes))
	for i, n := range key.Primes {
		pl[i] = n.BitLen()
	}

	return &PrivateKey{
		Loc:       loc,
		Primes:    len(key.Primes),
		PrimeLens: pl,
		Public:    PublicKeyInfo(loc, &key.PublicKey),
	}
}

// PrivateKey holds structured information about an RSA private key. It
// implements Info.
type PrivateKey struct {
	// Loc is the location the key was encountered.
	Loc string

	// Primes is the number of primes, ≥ 2.
	Primes int

	// PrimeLens holds the bit length of each prime.
	PrimeLens []int

	// Public holds information about the public portion of the key.
	Public *PublicKey
}

// Type indicates this is a private key.
func (priv *PrivateKey) Type() Type {
	return TypePrivateKey
}

// Location returns the location data stored by PrivateKeyInfo.
func (priv *PrivateKey) Location() string {
	return priv.Loc
}

// Info returns structured information about the private key.
func (priv *PrivateKey) Info() []Section {
	return []Section{
		priv.PrivateKeyInfoSection(),
		priv.Public.PublicKeyInfoSection(),
	}
}

// PrivateKeyInfoSection returns the RSA private key specific information
// section.
func (priv *PrivateKey) PrivateKeyInfoSection() Section {
	return Section{
		Title: "RSA private key",
		Fields: []Field{
			Field{
				Key:   "Primes",
				Value: priv.Primes,
			},
			Field{
				Key:   "Prime lengths",
				Value: priv.PrimeLens,
			},
		},
	}
}