package cluster

import (
	"encoding/binary"
	"expvar"
	"fmt"
	"io"
	"log"
	"net"
	"os"
	"strconv"
	"sync"
	"time"

	"github.com/golang/protobuf/proto"
	"github.com/rqlite/rqlite/command"
)

// stats captures stats for the Cluster service.
var stats *expvar.Map

const (
	numGetNodeAPIRequest  = "num_get_node_api_req"
	numGetNodeAPIResponse = "num_get_node_api_resp"
	numExecuteRequest     = "num_execute_req"
	numQueryRequest       = "num_query_req"
)

const (
	// MuxRaftHeader is the byte used to indicate internode Raft communications.
	MuxRaftHeader = 1

	// MuxClusterHeader is the byte used to request internode cluster state information.
	MuxClusterHeader = 2 // Cluster state communications
)

func init() {
	stats = expvar.NewMap("cluster")
	stats.Add(numGetNodeAPIRequest, 0)
	stats.Add(numGetNodeAPIResponse, 0)
	stats.Add(numExecuteRequest, 0)
	stats.Add(numQueryRequest, 0)
}

// Dialer is the interface dialers must implement.
type Dialer interface {
	// Dial is used to create a connection to a service listening
	// on an address.
	Dial(address string, timeout time.Duration) (net.Conn, error)
}

// Database is the interface any queryable system must implement
type Database interface {
	// Execute executes a slice of queries, each of which is not expected
	// to return rows. If timings is true, then timing information will
	// be return. If tx is true, then either all queries will be executed
	// successfully or it will as though none executed.
	Execute(er *command.ExecuteRequest) ([]*command.ExecuteResult, error)

	// Query executes a slice of queries, each of which returns rows. If
	// timings is true, then timing information will be returned. If tx
	// is true, then all queries will take place while a read transaction
	// is held on the database.
	Query(qr *command.QueryRequest) ([]*command.QueryRows, error)
}

// Transport is the interface the network layer must provide.
type Transport interface {
	net.Listener
	Dialer
}

// Service provides information about the node and cluster.
type Service struct {
	tn   Transport // Network layer this service uses
	addr net.Addr  // Address on which this service is listening

	db Database // The queryable system.

	mu      sync.RWMutex
	https   bool   // Serving HTTPS?
	apiAddr string // host:port this node serves the HTTP API.

	logger *log.Logger
}

// New returns a new instance of the cluster service
func New(tn Transport, db Database) *Service {
	return &Service{
		tn:     tn,
		addr:   tn.Addr(),
		db:     db,
		logger: log.New(os.Stderr, "[cluster] ", log.LstdFlags),
	}
}

// Open opens the Service.
func (s *Service) Open() error {
	go s.serve()
	s.logger.Println("service listening on", s.tn.Addr())
	return nil
}

// Close closes the service.
func (s *Service) Close() error {
	s.tn.Close()
	return nil
}

// Addr returns the address the service is listening on.
func (s *Service) Addr() string {
	return s.addr.String()
}

// EnableHTTPS tells the cluster service the API serves HTTPS.
func (s *Service) EnableHTTPS(b bool) {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.https = b
}

// SetAPIAddr sets the API address the cluster service returns.
func (s *Service) SetAPIAddr(addr string) {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.apiAddr = addr
}

// GetAPIAddr returns the previously-set API address
func (s *Service) GetAPIAddr() string {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.apiAddr
}

// Stats returns status of the Service.
func (s *Service) Stats() (map[string]interface{}, error) {
	st := map[string]interface{}{
		"addr":     s.addr.String(),
		"https":    strconv.FormatBool(s.https),
		"api_addr": s.apiAddr,
	}

	return st, nil
}

func (s *Service) serve() error {
	for {
		conn, err := s.tn.Accept()
		if err != nil {
			return err
		}

		go s.handleConn(conn)
	}
}

func (s *Service) handleConn(conn net.Conn) {
	defer conn.Close()

	b := make([]byte, 4)
	_, err := io.ReadFull(conn, b)
	if err != nil {
		return
	}
	sz := binary.LittleEndian.Uint16(b[0:])

	b = make([]byte, sz)
	_, err = io.ReadFull(conn, b)
	if err != nil {
		return
	}

	c := &Command{}
	err = proto.Unmarshal(b, c)
	if err != nil {
		conn.Close()
	}

	switch c.Type {
	case Command_COMMAND_TYPE_GET_NODE_API_URL:
		stats.Add(numGetNodeAPIRequest, 1)
		s.mu.RLock()
		defer s.mu.RUnlock()

		a := &Address{}
		scheme := "http"
		if s.https {
			scheme = "https"
		}
		a.Url = fmt.Sprintf("%s://%s", scheme, s.apiAddr)

		b, err = proto.Marshal(a)
		if err != nil {
			conn.Close()
		}
		conn.Write(b)
		stats.Add(numGetNodeAPIResponse, 1)

	case Command_COMMAND_TYPE_EXECUTE:
		stats.Add(numExecuteRequest, 1)

		resp := &CommandExecuteResponse{}

		er := c.GetExecuteRequest()
		if er == nil {
			resp.Error = "ExecuteRequest is nil"
		} else {
			res, err := s.db.Execute(er)
			if err != nil {
				resp.Error = err.Error()
			} else {
				resp.Results = make([]*command.ExecuteResult, len(res))
				for i := range res {
					resp.Results[i] = res[i]
				}
			}
		}

		b, err = proto.Marshal(resp)
		if err != nil {
			return
		}
		conn.Write(b)

	case Command_COMMAND_TYPE_QUERY:
		stats.Add(numQueryRequest, 1)

		resp := &CommandQueryResponse{}

		qr := c.GetQueryRequest()
		if qr == nil {
			resp.Error = "QueryRequest is nil"
		} else {
			res, err := s.db.Query(qr)
			if err != nil {
				resp.Error = err.Error()
			} else {
				resp.Rows = make([]*command.QueryRows, len(res))
				for i := range res {
					resp.Rows[i] = res[i]
				}
			}
		}

		b, err = proto.Marshal(resp)
		if err != nil {
			return
		}
		conn.Write(b)
	}
}