package redis

import (
	"context"
	"errors"
	"hash/crc64"
	"sync"
	"time"

	"github.com/dualinventive/go-lruttl"
	"github.com/gomodule/redigo/redis"
	"github.com/mna/redisc"
	"src.dualinventive.com/go/dinet/rpc"
	"src.dualinventive.com/go/lib/dilog"
)

// Redis realtime status subscriber
type Redis struct {
	logger  dilog.Logger
	rc      *redisc.Cluster
	c       chan *rpc.Msg
	cacheMu sync.Mutex
	// cache keeps track of the last update of every Redis record
	cache      *lruttl.Cache
	crc64Table *crc64.Table
}

func createPool(addr string, opts ...redis.DialOption) (*redis.Pool, error) {
	return &redis.Pool{
		MaxIdle:     5,
		MaxActive:   10,
		IdleTimeout: time.Minute,
		Dial: func() (redis.Conn, error) {
			return redis.Dial("tcp", addr, opts...)
		},
		TestOnBorrow: func(c redis.Conn, t time.Time) error {
			_, err := c.Do("PING")
			return err
		},
	}, nil
}

// New creates a new Redis realtime status instance.
func New(logger dilog.Logger, uris []string, connectionTimeout time.Duration, cacheMaxItems int,
	cacheExpiry time.Duration) (*Redis, error) {
	rc := redisc.Cluster{
		StartupNodes: uris,
		DialOptions:  []redis.DialOption{redis.DialConnectTimeout(connectionTimeout)},
		CreatePool:   createPool,
	}

	// Update the cluster nodes inventory based on the first node
	if err := rc.Refresh(); err != nil {
		return nil, err
	}

	r := &Redis{
		logger:     logger,
		rc:         &rc,
		c:          make(chan *rpc.Msg),
		cache:      lruttl.New(cacheMaxItems, cacheExpiry),
		crc64Table: crc64.MakeTable(crc64.ISO),
	}
	return r, nil
}

// Send sends a message to redis. It is processed internally by another go routine.
func (r *Redis) Send(m *rpc.Msg) error {
	r.c <- m
	return nil
}

// Process processes all incomming write messages. This method blocks until the context is invalid.
func (r *Redis) Process(ctx context.Context) {
	for {
		select {
		case <-ctx.Done():
			return
		case m := <-r.c:
			logger := r.logger.WithFields(dilog.Fields{
				"device:uid":  m.DeviceUID,
				"project:id":  m.ProjectID,
				"classmethod": m.ClassMethod,
				"type":        m.Type,
			})
			if err := r.process(logger, m); err != nil {
				logger.WithError(err).Error("Unable to process RPC message")
			}
		}
	}
}

// process processes a single rpc message
func (r *Redis) process(logger dilog.Logger, msg *rpc.Msg) error {
	// Ignore error messages
	if msg.Error != nil {
		return nil
	}

	if ok, err := r.shouldProcess(msg); !ok {
		return err
	}

	// Sensor data
	if msg.ClassMethod == rpc.ClassMethodSensorData {
		var resValueItems []rpc.ResultValueItem
		if err := msg.Result.Unmarshal(&resValueItems); err != nil {
			return err
		}
		if err := r.processSensorData(logger, msg, resValueItems); err != nil {
			return err
		}
		return r.publish(msg)
	}

	var valueItems []map[string]interface{}
	// All other class:method versions with result
	if err := msg.Result.Unmarshal(&valueItems); err == nil {
		if err = r.processGeneralClassMethod(logger, msg, valueItems); err != nil {
			return err
		}
		return r.publish(msg)
	}

	// All other class:method versions without result
	result := make(map[string]interface{})
	result["time"] = msg.Time

	mKeyName := keyName(msg)
	if mKeyName == "" {
		logger.Warning("Redis.process keyName is empty")
		return nil
	}

	if err := r.processMsgResult(logger, mKeyName, fieldName(msg, 0), result); err != nil {
		return err
	}
	return r.publish(msg)
}

func (r *Redis) shouldProcess(msg *rpc.Msg) (bool, error) {
	switch msg.Class() {
	case rpc.ClassLog, rpc.ClassMessage:
		// Drop log and message messages
		return false, nil
	case rpc.ClassProject:
		// Project class must contain a project ID
		if !rpc.ValidProjectID(msg.ProjectID) {
			return false, errors.New("project contains no projectID")
		}

		// Project class must contain a result
		if msg.Result.IsEmpty() {
			return false, errors.New("project contains no result")
		}
	default:
		// All other methods must contain a device UID or project ID
		if !rpc.ValidDeviceUID(msg.DeviceUID) && !rpc.ValidProjectID(msg.ProjectID) {
			return false, errors.New("message has invalid deviceUID or projectID")
		}
	}
	// Drop request messages
	if msg.Type == rpc.MsgTypeRequest {
		return false, nil
	}
	return true, nil
}

// getConn gets a new connection from the cluster
//         it configures it as a retry connection. With 3 retries and 1s timeout delay.
func (r *Redis) getConn() (redis.Conn, error) {
	conn := r.rc.Get()

	// create the retry connection - only Do, Close and Err are
	// supported on that connection. It will make up to 3 attempts
	// to get a valid response, and will wait 100ms before a retry
	// in case of a TRYAGAIN redis error.
	return redisc.RetryConn(conn, 3, time.Second)
}

// Close the connection to redis
func (r *Redis) Close() error {
	return r.rc.Close()
}