package database

import (
	"errors"
	"log"

	r "github.com/GoRethink/gorethink"
	"github.com/brandur/simplebox"
	"golang.org/x/crypto/acme/autocert"
	"golang.org/x/net/context"
)

// CertCache extends DB to provide certificate management functions for
// https://godoc.org/golang.org/x/crypto/acme/autocert#Cache
type CertCache struct {
	*DB
	SimpleBox *simplebox.SimpleBox
}

// CryptoLevel indicates what form of cryptography the certificate is stored
// with.
type CryptoLevel int

// Crypto levels / strategies defined
const (
	// NOTE: this is defined for debugging / testing usage only
	CryptoLevelNone CryptoLevel = iota

	// Use the global set of secretbox keys
	CryptoLevelSecretbox
)

// CachedCert is an individual cached certificate in the database.
type CachedCert struct {
	Key         string      `gorethink:"id" storm:"id"`
	CryptoLevel CryptoLevel `gorethink:"cryptoLevel"`
	// PEM-encoded bytes with the above crypto level as a filter.
	Body []byte `gorethink:"body"`
}

// Get returns a certificate data for the specified key.
// If there's no such key, Get returns ErrCacheMiss.
func (c *CertCache) Get(ctx context.Context, key string) ([]byte, error) {
	res, err := r.Table("certs").Get(key).Run(c.s)
	if err != nil {
		return nil, err
	}

	cert := &CachedCert{}
	err = res.One(cert)
	if err != nil {
		log.Printf("decoding cached cert failed: %v", err)
		return nil, autocert.ErrCacheMiss
	}

	var body []byte

	switch cert.CryptoLevel {
	case CryptoLevelNone:
		body = cert.Body
	case CryptoLevelSecretbox:
		if c.SimpleBox == nil {
			return nil, errors.New("can't read this cert, no key in memory")
		}

		body, err = c.SimpleBox.Decrypt(cert.Body)
		if err != nil {
			return nil, autocert.ErrCacheMiss
		}
	}

	log.Printf("certcache: fetched: %s", key)

	return body, nil
}

// Put stores the data in the cache under the specified key.
// Underlying implementations may use any data storage format,
// as long as the reverse operation, Get, results in the original data.
func (c *CertCache) Put(ctx context.Context, key string, data []byte) error {
	cert := &CachedCert{
		Key:         key,
		CryptoLevel: CryptoLevelNone,
		Body:        data,
	}

	if c.SimpleBox != nil {
		cert.CryptoLevel = CryptoLevelSecretbox
		cert.Body = c.SimpleBox.Encrypt(data)
	}

	log.Printf("certcache: added: %s", key)

	_, err := r.Table("certs").Insert(cert).RunWrite(c.s)
	return err
}

// Delete removes a certificate data from the cache under the specified key.
// If there's no such key in the cache, Delete returns nil.
func (c *CertCache) Delete(ctx context.Context, key string) error {
	_, err := r.Table("certs").Get(key).Delete().Run(c.s)

	log.Printf("certcache: deleted: %s", key)
	return err
}