package goredis

import "strings"
import "strconv"
import "errors"
import "math/rand"
import "os"
import "fmt"

const RedisClusterHashSlots = 16384
const RedisClusterRequestTTL = 16
const RedisClusterDefaultTimeout = 1

type RedisCluster struct {
	SeedHosts        map[string]bool
	Handles          map[string]*RedisHandle
	Slots            map[uint16]string
	RefreshTableASAP bool
	SingleRedisMode  bool
	MaxIdle          int
	MaxActive        int
	Debug            bool
}

func NewRedisCluster(addrs []string, max_idle, max_active int, debug bool) RedisCluster {
	cluster := RedisCluster{RefreshTableASAP: false,
		SingleRedisMode: false,
		SeedHosts:       make(map[string]bool),
		Handles:         make(map[string]*RedisHandle),
		Slots:           make(map[uint16]string),
		MaxActive:       max_active,
		Debug:           debug}

	if cluster.Debug {
		fmt.Println("[RedisCluster], PID", os.Getpid(), "StartingNewRedisCluster")
	}

	for _, label := range addrs {
		cluster.SeedHosts[label] = true
		cluster.Handles[label] = NewRedisHandle(label, max_idle, max_active, debug)
	}

	for addr, _ := range cluster.SeedHosts {
		node, ok := cluster.Handles[addr]
		if !ok {
			node = NewRedisHandle(addr, cluster.MaxIdle, cluster.MaxActive, cluster.Debug)
			cluster.Handles[addr] = node
		}

		cluster_enabled := cluster.hasClusterEnabled(node)
		if cluster_enabled == false {
			if len(cluster.SeedHosts) == 1 {
				cluster.SingleRedisMode = true
			} else {
				panic(errors.New("Multiple Seed Hosts Given, But Cluster Support Disabled in Redis"))
			}
		}
	}

	if cluster.SingleRedisMode == false {
		cluster.populateSlotsCache()
	}
	return cluster
}

func (self *RedisCluster) Update(max_idle, max_active int32) {
	for _, rh := range self.Handles {
		rh.Pool.Update(max_idle, max_active)
	}
}

func (self *RedisCluster) SetWaitTime(t int) {
	for _, rh := range self.Handles {
		rh.Pool.SetWaitTime(t)
	}
}

func (self *RedisCluster) SetLifeTime(t int) {
	for _, rh := range self.Handles {
		rh.Pool.SetLifeTime(t)
	}
}

func (self *RedisCluster) SetPingTime(t int) {
	for _, rh := range self.Handles {
		rh.Pool.SetPingTime(t)
	}
}

func (self *RedisCluster) TestCluster() error {
	for _, rh := range self.Handles {
		_, err := rh.Do("CLUSTER", "INFO")
		if err != nil {
			return err
		}
	}
	return nil
}

func (self *RedisCluster) GetHandle(key string) *RedisHandle {
	return self.HandleForKey(key)
}

func (self *RedisCluster) Do(cmd string, args ...interface{}) (reply interface{}, err error) {
	return self.SendClusterCommand(cmd, args...)
}

func (self *RedisCluster) hasClusterEnabled(node *RedisHandle) bool {
	_, err := node.Do("CLUSTER", "INFO")
	if err != nil {
		if err.Error() == "ERR This instance has cluster support disabled" ||
			err.Error() == "ERR unknown command 'CLUSTER'" {
			return false
		}
	}
	return true
}

// contact the startup nodes and try to fetch the hash slots -> instances
// map in order to initialize the Slots map.
func (self *RedisCluster) populateSlotsCache() {
	if self.SingleRedisMode == true {
		return
	}
	if self.Debug {
		fmt.Println("[RedisCluster], PID", os.Getpid(), "[PopulateSlots Running]")
	}
	seedHosts := make(map[string]bool)
	handles := make(map[string]*RedisHandle)
	slotsMap := make(map[uint16]string)
	for k, v := range self.SeedHosts {
		seedHosts[k] = v
	}
	for k, v := range self.Handles {
		handles[k] = v
	}
	for k, v := range self.Slots {
		slotsMap[k] = v
	}
	for name, _ := range self.SeedHosts {
		if self.Debug {
			fmt.Println("[RedisCluster] [PopulateSlots] Checking: ", name)
		}
		var (
			node *RedisHandle
			ok   bool
		)
		if node, ok = handles[name]; !ok {
			node = NewRedisHandle(name, self.MaxIdle, self.MaxActive, self.Debug)
			handles[name] = node
		}
		cluster_info, err := node.Do("CLUSTER", "NODES")
		if err == nil {
			lines := strings.Split(string(cluster_info.([]uint8)), "\n")
			for _, line := range lines {
				if line != "" {
					fields := strings.Split(line, " ")
					addr := fields[1]
					if addr == ":0" {
						addr = name
					}
					// add to seedlist if not in cluster
					seedHosts[addr] = true

					// add to handles if not in handles
					if _, ok := handles[name]; !ok {
						handles[name] = NewRedisHandle(addr, self.MaxIdle, self.MaxActive, self.Debug)
					}

					slots := fields[8:len(fields)]
					for _, s_range := range slots {
						slot_range := s_range
						if slot_range != "[" {
							if self.Debug {
								fmt.Println("[RedisCluster] Considering Slot Range", slot_range)
							}
							r_pieces := strings.Split(slot_range, "-")
							min, _ := strconv.Atoi(r_pieces[0])
							max, _ := strconv.Atoi(r_pieces[1])
							for i := min; i <= max; i++ {
								slotsMap[uint16(i)] = addr
							}
						}
					}
				}
			}
			if self.Debug {
				fmt.Println("[RedisCluster] [Initializing] DONE, ",
					"Slots: ", len(slotsMap),
					"Handles So Far:", len(handles),
					"SeedList:", len(seedHosts))
			}
			break
		}
	}
	self.SeedHosts = seedHosts
	self.Handles = handles
	self.Slots = slotsMap
	self.switchToSingleModeIfNeeded()
}

func (self *RedisCluster) switchToSingleModeIfNeeded() {
	// catch case where we really intend to be on
	// single redis mode, but redis was not
	// started on time
	if len(self.SeedHosts) == 1 &&
		len(self.Slots) == 0 &&
		len(self.Handles) == 1 {
		for _, node := range self.Handles {
			cluster_enabled := self.hasClusterEnabled(node)
			if cluster_enabled == false {
				self.SingleRedisMode = true
			}
		}
	}
}

func (self *RedisCluster) KeyForRequest(cmd string, args ...interface{}) string {
	cmd = strings.ToLower(cmd)
	if cmd == "info" ||
		cmd == "multi" ||
		cmd == "exec" ||
		cmd == "slaveof" ||
		cmd == "config" ||
		cmd == "shutdown" {
		return ""
	}
	if args[0] == nil {
		return ""
	}
	strs := args[0].([]interface{})
	if strs != nil && strs[0] != nil {
		return strs[0].(string)
	}
	return ""
}

// Return the hash slot from the key.
func (self *RedisCluster) SlotForKey(key string) uint16 {
	checksum := ChecksumCRC16([]byte(key))
	slot := checksum % RedisClusterHashSlots
	return slot
}

func (self *RedisCluster) RandomRedisHandle() *RedisHandle {
	if len(self.Handles) == 0 {
		return nil
	}
	addrs := make([]string, len(self.Handles))
	i := 0
	for addr, _ := range self.Handles {
		addrs[i] = addr
		i++
	}
	rand_addrs := make([]string, i)
	perm := rand.Perm(i)
	for j, v := range perm {
		rand_addrs[v] = addrs[j]
	}
	handle := self.Handles[rand_addrs[0]]
	self.switchToSingleModeIfNeeded()
	return handle
}

// Given a slot return the link (Redis instance) to the mapped node.
// Make sure to create a connection with the node if we don't have
// one.
func (self *RedisCluster) RedisHandleForSlot(slot uint16) *RedisHandle {

	node, exists := self.Slots[slot]
	// If we don't know what the mapping is, return a random node.
	if !exists {
		if self.Debug {
			fmt.Println("[RedisCluster] No One Appears Responsible For Slot: ", slot, "our slotsize is: ", len(self.Slots))
		}
		return self.RandomRedisHandle()
	}

	r, cx_exists := self.Handles[node]
	// add to cluster if not in cluster
	if cx_exists {
		return r
	} else {
		r = NewRedisHandle(node, self.MaxIdle, self.MaxActive, self.Debug)
		handles := make(map[string]*RedisHandle)
		for k, v := range self.Handles {
			handles[k] = v
		}
		handles[node] = r
		self.Handles = handles
	}
	// XXX consider returning random if failure
	return r
}

func (self *RedisCluster) disconnectAll() {
	if self.Debug {
		fmt.Println("[RedisCluster] PID:", os.Getpid(), " [Disconnect!] Had Handles:", len(self.Handles))
	}
	// disconnect anyone in handles
	for _, handle := range self.Handles {
		handle.Pool.Close()
	}
	self.Handles = make(map[string]*RedisHandle)

	// nuke slots
	self.Slots = make(map[uint16]string)
}

func (self *RedisCluster) handleSingleMode(flush bool, cmd string, args ...interface{}) (reply interface{}, err error) {
	for _, handle := range self.Handles {
		return handle.Do(cmd, args...)
	}
	return nil, errors.New("no redis handle found for single mode")
}

func (self *RedisCluster) SendClusterCommand(cmd string, args ...interface{}) (reply interface{}, err error) {
	var flush bool = true
	// forward onto first redis in the handle
	// if we are set to single mode
	if self.SingleRedisMode == true {
		return self.handleSingleMode(flush, cmd, args...)
	}

	if self.RefreshTableASAP == true {
		if self.Debug {
			fmt.Println("[RedisCluster] Refresh Needed")
		}
		self.disconnectAll()
		self.populateSlotsCache()
		self.RefreshTableASAP = false
		// in case we realized we were now in Single Mode
		if self.SingleRedisMode == true {
			return self.handleSingleMode(flush, cmd, args...)
		}
	}

	ttl := RedisClusterRequestTTL
	key := self.KeyForRequest(cmd, args)
	try_random_node := false
	asking := false
	for {
		if ttl <= 0 {
			break
		}
		ttl -= 1
		if key == "" {
			panic(errors.New("no way to dispatch this type of command to redis cluster"))
		}
		slot := self.SlotForKey(key)

		var redis *RedisHandle

		if self.Debug {
			fmt.Println("[RedisCluster] slot: ", slot, "key", key, "ttl", ttl)
		}

		if try_random_node {
			if self.Debug {
				fmt.Println("[RedisCluster] Trying Random Node")
			}
			redis = self.RandomRedisHandle()
			try_random_node = false
		} else {
			if self.Debug {
				fmt.Println("[RedisCluster] Trying Specific Node")
			}
			redis = self.RedisHandleForSlot(slot)
		}

		if redis == nil {
			if self.Debug {
				fmt.Println("[RedisCluster] could not get redis handle, bailing this round")
			}
			break
		}
		if self.Debug {
			fmt.Println("[RedisCluster] Got addr: ", redis.Addr)
		}

		if asking {
			if self.Debug {
				fmt.Println("ASKING")
			}
			//	conn := redis.GetRedisConn()
			redis.Do("ASKING")
			//	conn.Close()
			asking = false
		}

		var err error
		var resp interface{}

		if flush {
			resp, err = redis.Do(cmd, args...)
			if err == nil {
				if self.Debug {
					fmt.Println("[RedisCluster] Success")
				}
				return resp, nil
			}
		} /*else {
			err = redis.Send(cmd, args...)
			if err == nil {
				if self.Debug {
					fmt.Println("[RedisCluster] Success")
				}
				return nil, nil
			}
		}*/

		// ok we are here so err is not nil
		errv := strings.Split(err.Error(), " ")
		if errv[0] == "MOVED" || errv[0] == "ASK" {
			if errv[0] == "ASK" {
				if self.Debug {
					fmt.Println("[RedisCluster] ASK")
				}
				asking = true
			} else {
				// Serve replied with MOVED. It's better for us to
				// ask for CLUSTER NODES the next time.
				SetRefreshNeeded()
				newslot, _ := strconv.Atoi(errv[1])
				newaddr := errv[2]
				slotsMap := make(map[uint16]string)
				for k, v := range self.Slots {
					slotsMap[k] = v
				}
				slotsMap[uint16(newslot)] = newaddr
				self.Slots = slotsMap
				if self.Debug {
					fmt.Println("[RedisCluster] MOVED newaddr: ", newaddr, "new slot: ", newslot, "my slots len: ", len(self.Slots))
				}
			}
		} else {
			if self.Debug {
				fmt.Println("[RedisCluster] Other Error: ", err.Error())
			}
			try_random_node = true
		}
	}
	if self.Debug {
		fmt.Println("[RedisCluster] Failed Command")
	}
	return nil, errors.New("could not complete command")
}

//func (self *RedisCluster) Send(cmd string, args ...interface{}) (err error) {
//	_, err = self.SendClusterCommand(false, cmd, args...)
//	return err
//}

func (self *RedisCluster) SetRefreshNeeded() {
	self.RefreshTableASAP = true
}

func (self *RedisCluster) HandleForKey(key string) *RedisHandle {
	// forward onto first redis in the handle
	// if we are set to single mode
	if self.SingleRedisMode == true {
		for _, handle := range self.Handles {
			return handle
		}
	}
	slot := self.SlotForKey(key)
	handle := self.RedisHandleForSlot(slot)
	return handle
}

type RedisClusterAccess interface {
	Do(commandName string, args ...interface{}) (reply interface{}, err error)
	//	Send(cmd string, args ...interface{}) (err error)
	SetRefreshNeeded()
	HandleForKey(key string) *RedisHandle
}

var Instance RedisCluster

func Do(commandName string, args ...interface{}) (reply interface{}, err error) {
	return Instance.Do(commandName, args...)
}

//func Send(cmd string, args ...interface{}) (err error) {
//	return Instance.Send(cmd, args...)
//}

func SetRefreshNeeded() {
	Instance.SetRefreshNeeded()
}

func HandleForKey(key string) *RedisHandle {
	return Instance.HandleForKey(key)
}