package agent

import (
	"fmt"
	"io"
	"log"
	"net"
	"os"
	"path/filepath"
	"sync"

	"github.com/hashicorp/nomad/client"
	"github.com/hashicorp/nomad/nomad"
	"github.com/hashicorp/nomad/nomad/structs"
)

// Agent is a long running daemon that is used to run both
// clients and servers. Servers are responsible for managing
// state and making scheduling decisions. Clients can be
// scheduled to, and are responsible for interfacing with
// servers to run allocations.
type Agent struct {
	config    *Config
	logger    *log.Logger
	logOutput io.Writer

	server *nomad.Server
	client *client.Client

	shutdown     bool
	shutdownCh   chan struct{}
	shutdownLock sync.Mutex
}

// NewAgent is used to create a new agent with the given configuration
func NewAgent(config *Config, logOutput io.Writer) (*Agent, error) {
	// Ensure we have a log sink
	if logOutput == nil {
		logOutput = os.Stderr
	}

	a := &Agent{
		config:     config,
		logger:     log.New(logOutput, "", log.LstdFlags),
		logOutput:  logOutput,
		shutdownCh: make(chan struct{}),
	}

	if err := a.setupServer(); err != nil {
		return nil, err
	}
	if err := a.setupClient(); err != nil {
		return nil, err
	}
	if a.client == nil && a.server == nil {
		return nil, fmt.Errorf("must have at least client or server mode enabled")
	}
	return a, nil
}

// serverConfig is used to generate a new server configuration struct
// for initializing a nomad server.
func (a *Agent) serverConfig() (*nomad.Config, error) {
	conf := a.config.NomadConfig
	if conf == nil {
		conf = nomad.DefaultConfig()
	}
	conf.LogOutput = a.logOutput
	conf.DevMode = a.config.DevMode
	conf.Build = fmt.Sprintf("%s%s", a.config.Version, a.config.VersionPrerelease)
	if a.config.Region != "" {
		conf.Region = a.config.Region
	}
	if a.config.Datacenter != "" {
		conf.Datacenter = a.config.Datacenter
	}
	if a.config.NodeName != "" {
		conf.NodeName = a.config.NodeName
	}
	if a.config.Server.Bootstrap {
		conf.Bootstrap = a.config.Server.Bootstrap
	}
	if a.config.Server.BootstrapExpect > 0 {
		conf.BootstrapExpect = a.config.Server.BootstrapExpect
	}
	if a.config.DataDir != "" {
		conf.DataDir = filepath.Join(a.config.DataDir, "server")
	}
	if a.config.Server.DataDir != "" {
		conf.DataDir = a.config.Server.DataDir
	}
	if a.config.Server.ProtocolVersion != 0 {
		conf.ProtocolVersion = uint8(a.config.Server.ProtocolVersion)
	}
	if a.config.Server.NumSchedulers != 0 {
		conf.NumSchedulers = a.config.Server.NumSchedulers
	}
	if len(a.config.Server.EnabledSchedulers) != 0 {
		conf.EnabledSchedulers = a.config.Server.EnabledSchedulers
	}

	// Set up the advertise addrs
	if addr := a.config.AdvertiseAddrs.Serf; addr != "" {
		serfAddr, err := net.ResolveTCPAddr("tcp", addr)
		if err != nil {
			return nil, fmt.Errorf("error resolving serf advertise address: %s", err)
		}
		conf.SerfConfig.MemberlistConfig.AdvertiseAddr = serfAddr.IP.String()
		conf.SerfConfig.MemberlistConfig.AdvertisePort = serfAddr.Port
	}
	if addr := a.config.AdvertiseAddrs.RPC; addr != "" {
		rpcAddr, err := net.ResolveTCPAddr("tcp", addr)
		if err != nil {
			return nil, fmt.Errorf("error resolving rpc advertise address: %s", err)
		}
		conf.RPCAdvertise = rpcAddr
	}

	// Set up the bind addresses
	if addr := a.config.BindAddr; addr != "" {
		conf.RPCAddr.IP = net.ParseIP(addr)
		conf.SerfConfig.MemberlistConfig.BindAddr = addr
	}
	if addr := a.config.Addresses.RPC; addr != "" {
		conf.RPCAddr.IP = net.ParseIP(addr)
	}
	if addr := a.config.Addresses.Serf; addr != "" {
		conf.SerfConfig.MemberlistConfig.BindAddr = addr
	}

	// Set up the ports
	if port := a.config.Ports.RPC; port != 0 {
		conf.RPCAddr.Port = port
	}
	if port := a.config.Ports.Serf; port != 0 {
		conf.SerfConfig.MemberlistConfig.BindPort = port
	}

	return conf, nil
}

// setupServer is used to setup the server if enabled
func (a *Agent) setupServer() error {
	if !a.config.Server.Enabled {
		return nil
	}

	// Setup the configuration
	conf, err := a.serverConfig()
	if err != nil {
		return fmt.Errorf("server config setup failed: %s", err)
	}

	// Create the server
	server, err := nomad.NewServer(conf)
	if err != nil {
		return fmt.Errorf("server setup failed: %v", err)
	}

	a.server = server
	return nil
}

// setupClient is used to setup the client if enabled
func (a *Agent) setupClient() error {
	if !a.config.Client.Enabled {
		return nil
	}

	// Setup the configuration
	conf := a.config.ClientConfig
	if conf == nil {
		conf = client.DefaultConfig()
	}
	if a.server != nil {
		conf.RPCHandler = a.server
	}
	conf.LogOutput = a.logOutput
	conf.DevMode = a.config.DevMode
	if a.config.Region != "" {
		conf.Region = a.config.Region
	}
	if a.config.DataDir != "" {
		conf.StateDir = filepath.Join(a.config.DataDir, "client")
		conf.AllocDir = filepath.Join(a.config.DataDir, "alloc")
	}
	if a.config.Client.StateDir != "" {
		conf.StateDir = a.config.Client.StateDir
	}
	if a.config.Client.AllocDir != "" {
		conf.AllocDir = a.config.Client.AllocDir
	}
	conf.Servers = a.config.Client.Servers

	// Setup the node
	conf.Node = new(structs.Node)
	conf.Node.Datacenter = a.config.Datacenter
	conf.Node.Name = a.config.NodeName
	conf.Node.ID = a.config.Client.NodeID
	conf.Node.Meta = a.config.Client.Meta
	conf.Node.NodeClass = a.config.Client.NodeClass

	// Create the client
	client, err := client.NewClient(conf)
	if err != nil {
		return fmt.Errorf("client setup failed: %v", err)
	}
	a.client = client
	return nil
}

// Leave is used gracefully exit. Clients will inform servers
// of their departure so that allocations can be rescheduled.
func (a *Agent) Leave() error {
	if a.client != nil {
		if err := a.client.Leave(); err != nil {
			a.logger.Printf("[ERR] agent: client leave failed: %v", err)
		}
	}
	if a.server != nil {
		if err := a.server.Leave(); err != nil {
			a.logger.Printf("[ERR] agent: server leave failed: %v", err)
		}
	}
	return nil
}

// Shutdown is used to terminate the agent.
func (a *Agent) Shutdown() error {
	a.shutdownLock.Lock()
	defer a.shutdownLock.Unlock()

	if a.shutdown {
		return nil
	}

	a.logger.Println("[INFO] agent: requesting shutdown")
	if a.client != nil {
		if err := a.client.Shutdown(); err != nil {
			a.logger.Printf("[ERR] agent: client shutdown failed: %v", err)
		}
	}
	if a.server != nil {
		if err := a.server.Shutdown(); err != nil {
			a.logger.Printf("[ERR] agent: server shutdown failed: %v", err)
		}
	}

	a.logger.Println("[INFO] agent: shutdown complete")
	a.shutdown = true
	close(a.shutdownCh)
	return nil
}

// RPC is used to make an RPC call to the Nomad servers
func (a *Agent) RPC(method string, args interface{}, reply interface{}) error {
	if a.server != nil {
		return a.server.RPC(method, args, reply)
	}
	return a.client.RPC(method, args, reply)
}

// Client returns the configured client or nil
func (a *Agent) Client() *client.Client {
	return a.client
}

// Server returns the configured server or nil
func (a *Agent) Server() *nomad.Server {
	return a.server
}

// Stats is used to return statistics for debugging and insight
// for various sub-systems
func (a *Agent) Stats() map[string]map[string]string {
	stats := make(map[string]map[string]string)
	if a.server != nil {
		subStat := a.server.Stats()
		for k, v := range subStat {
			stats[k] = v
		}
	}
	if a.client != nil {
		subStat := a.client.Stats()
		for k, v := range subStat {
			stats[k] = v
		}
	}
	return stats
}