package cassandra

import (
	"context"
	"fmt"
	"strings"
	"sync"

	"github.com/gocql/gocql"
	"github.com/hashicorp/vault/sdk/framework"
	"github.com/hashicorp/vault/sdk/logical"
)

// Factory creates a new backend
func Factory(ctx context.Context, conf *logical.BackendConfig) (logical.Backend, error) {
	b := Backend()
	if err := b.Setup(ctx, conf); err != nil {
		return nil, err
	}
	return b, nil
}

// Backend contains the base information for the backend's functionality
func Backend() *backend {
	var b backend
	b.Backend = &framework.Backend{
		Help: strings.TrimSpace(backendHelp),

		PathsSpecial: &logical.Paths{
			SealWrapStorage: []string{
				"config/connection",
			},
		},

		Paths: []*framework.Path{
			pathConfigConnection(&b),
			pathRoles(&b),
			pathCredsCreate(&b),
		},

		Secrets: []*framework.Secret{
			secretCreds(&b),
		},

		Invalidate: b.invalidate,

		Clean: func(_ context.Context) {
			b.ResetDB(nil)
		},
		BackendType: logical.TypeLogical,
	}

	return &b
}

type backend struct {
	*framework.Backend

	// Session is goroutine safe, however, since we reinitialize
	// it when connection info changes, we want to make sure we
	// can close it and use a new connection; hence the lock
	session *gocql.Session
	lock    sync.Mutex
}

type sessionConfig struct {
	Hosts           string `json:"hosts" structs:"hosts" mapstructure:"hosts"`
	Username        string `json:"username" structs:"username" mapstructure:"username"`
	Password        string `json:"password" structs:"password" mapstructure:"password"`
	TLS             bool   `json:"tls" structs:"tls" mapstructure:"tls"`
	InsecureTLS     bool   `json:"insecure_tls" structs:"insecure_tls" mapstructure:"insecure_tls"`
	Certificate     string `json:"certificate" structs:"certificate" mapstructure:"certificate"`
	PrivateKey      string `json:"private_key" structs:"private_key" mapstructure:"private_key"`
	IssuingCA       string `json:"issuing_ca" structs:"issuing_ca" mapstructure:"issuing_ca"`
	ProtocolVersion int    `json:"protocol_version" structs:"protocol_version" mapstructure:"protocol_version"`
	ConnectTimeout  int    `json:"connect_timeout" structs:"connect_timeout" mapstructure:"connect_timeout"`
	TLSMinVersion   string `json:"tls_min_version" structs:"tls_min_version" mapstructure:"tls_min_version"`
}

// DB returns the database connection.
func (b *backend) DB(ctx context.Context, s logical.Storage) (*gocql.Session, error) {
	b.lock.Lock()
	defer b.lock.Unlock()

	// If we already have a DB, we got it!
	if b.session != nil {
		return b.session, nil
	}

	entry, err := s.Get(ctx, "config/connection")
	if err != nil {
		return nil, err
	}
	if entry == nil {
		return nil, fmt.Errorf("configure the DB connection with config/connection first")
	}

	config := &sessionConfig{}
	if err := entry.DecodeJSON(config); err != nil {
		return nil, err
	}

	session, err := createSession(config, s)
	//  Store the session in backend for reuse
	b.session = session

	return session, err
}

// ResetDB forces a connection next time DB() is called.
func (b *backend) ResetDB(newSession *gocql.Session) {
	b.lock.Lock()
	defer b.lock.Unlock()

	if b.session != nil {
		b.session.Close()
	}

	b.session = newSession
}

func (b *backend) invalidate(_ context.Context, key string) {
	switch key {
	case "config/connection":
		b.ResetDB(nil)
	}
}

const backendHelp = `
The Cassandra backend dynamically generates database users.

After mounting this backend, configure it using the endpoints within
the "config/" path.
`