// Simple RPC client balancer
package balancer2go

import (
	"sync"
)

// The main balancer type
type Balancer struct {
	sync.RWMutex
	clients         map[string]Worker
	balancerChannel chan Worker
}

// Interface for RPC clients
type Worker interface {
	Call(serviceMethod string, args interface{}, reply interface{}) error
	Close() error
}

// Constructor for RateList holding one slice for addreses and one slice for connections.
func NewBalancer() *Balancer {
	r := &Balancer{clients: make(map[string]Worker), balancerChannel: make(chan Worker)} // leaving both slices to nil
	go func() {
		for {
			if len(r.clients) > 0 {
				for _, c := range r.clients {
					r.balancerChannel <- c
				}
			} else {
				r.balancerChannel <- nil
			}
		}
	}()
	return r
}

// Adds a client to the two internal map.
func (bl *Balancer) AddClient(address string, client Worker) {
	bl.Lock()
	defer bl.Unlock()
	bl.clients[address] = client
	return
}

// Removes a client from the map locking the readers and reseting the balancer index.
func (bl *Balancer) RemoveClient(address string) {
	bl.Lock()
	defer bl.Unlock()
	delete(bl.clients, address)
	<-bl.balancerChannel
}

// Returns a client for the specifed address.
func (bl *Balancer) GetClient(address string) (c Worker, exists bool) {
	bl.RLock()
	defer bl.RUnlock()
	c, exists = bl.clients[address]
	return
}

// Returns the next available connection at each call looping at the end of connections.
func (bl *Balancer) Balance() (result Worker) {
	bl.RLock()
	defer bl.RUnlock()
	return <-bl.balancerChannel
}

// Sends a shotdown call to the clients
func (bl *Balancer) Shutdown(shutdownMethod string) {
	bl.Lock()
	defer bl.Unlock()
	var reply string
	for _, client := range bl.clients {
		client.Call(shutdownMethod, "", &reply)
	}
}

// Returns a string slice with all client addresses
func (bl *Balancer) GetClientAddresses() []string {
	bl.RLock()
	defer bl.RUnlock()
	var addresses []string
	for a, _ := range bl.clients {
		addresses = append(addresses, a)
	}
	return addresses
}