// Mgmt
// Copyright (C) 2013-2016+ James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package main

import (
	"github.com/codegangsta/cli"
	"log"
	"os"
	"os/signal"
	"sync"
	"syscall"
	"time"
)

// set at compile time
var (
	program string
	version string
)

const (
	DEBUG = false
)

// signal handler
func waitForSignal(exit chan bool) {
	signals := make(chan os.Signal, 1)
	signal.Notify(signals, os.Interrupt) // catch ^C
	//signal.Notify(signals, os.Kill) // catch signals
	signal.Notify(signals, syscall.SIGTERM)

	select {
	case e := <-signals: // any signal will do
		if e == os.Interrupt {
			log.Println("Interrupted by ^C")
		} else {
			log.Println("Interrupted by signal")
		}
	case <-exit: // or a manual signal
		log.Println("Interrupted by exit signal")
	}
}

func run(c *cli.Context) error {
	var start = time.Now().UnixNano()
	var wg sync.WaitGroup
	exit := make(chan bool) // exit signal
	log.Printf("This is: %v, version: %v", program, version)
	log.Printf("Main: Start: %v", start)
	var G, fullGraph *Graph

	// exit after `max-runtime` seconds for no reason at all...
	if i := c.Int("max-runtime"); i > 0 {
		go func() {
			time.Sleep(time.Duration(i) * time.Second)
			exit <- true
		}()
	}

	// setup converger
	converger := NewConverger(
		c.Int("converged-timeout"),
		func() { // lambda to run when converged
			log.Printf("Converged for %d seconds, exiting!", c.Int("converged-timeout"))
			exit <- true // trigger an exit!
		},
	)
	go converger.Loop(true) // main loop for converger, true to start paused

	// initial etcd peer endpoint
	seed := c.String("seed")
	if seed == "" {
		// XXX: start up etcd server, others will join me!
		seed = "http://127.0.0.1:2379" // thus we use the local server!
	}
	// then, connect to `seed` as a client

	// FIXME: validate seed, or wait for it to fail in etcd init?

	// etcd
	etcdO := &EtcdWObject{
		seed:      seed,
		converger: converger,
	}

	hostname := c.String("hostname")
	if hostname == "" {
		hostname, _ = os.Hostname() // etcd watch key // XXX: this is not the correct key name this is the set key name... WOOPS
	}
	go func() {
		startchan := make(chan struct{}) // start signal
		go func() { startchan <- struct{}{} }()
		file := c.String("file")
		configchan := make(chan bool)
		if !c.Bool("no-watch") {
			configchan = ConfigWatch(file)
		}
		log.Println("Etcd: Starting...")
		etcdchan := etcdO.EtcdWatch()
		first := true // first loop or not
		for {
			log.Println("Main: Waiting...")
			select {
			case _ = <-startchan: // kick the loop once at start
				// pass
			case msg := <-etcdchan:
				switch msg {
				// some types of messages we ignore...
				case etcdFoo, etcdBar:
					continue
				// while others passthrough and cause a compile!
				case etcdStart, etcdEvent:
					// pass
				default:
					log.Fatal("Etcd: Unhandled message: ", msg)
				}
			case msg := <-configchan:
				if c.Bool("no-watch") || !msg {
					continue // not ready to read config
				}
				//case compile_event: XXX
			}

			config := ParseConfigFromFile(file)
			if config == nil {
				log.Printf("Config parse failure")
				continue
			}

			// run graph vertex LOCK...
			if !first { // TODO: we can flatten this check out I think
				converger.Pause() // FIXME: add sync wait?
				G.Pause()         // sync
			}

			// build graph from yaml file on events (eg: from etcd)
			// we need the vertices to be paused to work on them
			if newFullgraph, err := fullGraph.NewGraphFromConfig(config, etcdO, hostname); err == nil { // keep references to all original elements
				fullGraph = newFullgraph
			} else {
				log.Printf("Config: Error making new graph from config: %v", err)
				// unpause!
				if !first {
					G.Start(&wg, first) // sync
					converger.Start()   // after G.Start()
				}
				continue
			}

			G = fullGraph.Copy() // copy to active graph
			// XXX: do etcd transaction out here...
			G.AutoEdges() // add autoedges; modifies the graph
			G.AutoGroup() // run autogroup; modifies the graph
			// TODO: do we want to do a transitive reduction?

			log.Printf("Graph: %v", G) // show graph
			err := G.ExecGraphviz(c.String("graphviz-filter"), c.String("graphviz"))
			if err != nil {
				log.Printf("Graphviz: %v", err)
			} else {
				log.Printf("Graphviz: Successfully generated graph!")
			}
			G.AssociateData(converger)
			// G.Start(...) needs to be synchronous or wait,
			// because if half of the nodes are started and
			// some are not ready yet and the EtcdWatch
			// loops, we'll cause G.Pause(...) before we
			// even got going, thus causing nil pointer errors
			G.Start(&wg, first) // sync
			converger.Start()   // after G.Start()
			first = false
		}
	}()

	log.Println("Main: Running...")

	waitForSignal(exit) // pass in exit channel to watch

	G.Exit() // tell all the children to exit

	if DEBUG {
		log.Printf("Graph: %v", G)
	}

	wg.Wait() // wait for primary go routines to exit

	// TODO: wait for each vertex to exit...
	log.Println("Goodbye!")
	return nil
}

func main() {
	//if DEBUG {
	log.SetFlags(log.LstdFlags | log.Lshortfile)
	//}
	log.SetFlags(log.Flags() - log.Ldate) // remove the date for now
	if program == "" || version == "" {
		log.Fatal("Program was not compiled correctly. Please see Makefile.")
	}
	app := cli.NewApp()
	app.Name = program
	app.Usage = "next generation config management"
	app.Version = version
	//app.Action = ... // without a default action, help runs

	app.Commands = []cli.Command{
		{
			Name:    "run",
			Aliases: []string{"r"},
			Usage:   "run",
			Action:  run,
			Flags: []cli.Flag{
				cli.StringFlag{
					Name:   "file, f",
					Value:  "",
					Usage:  "graph definition to run",
					EnvVar: "MGMT_FILE",
				},
				cli.BoolFlag{
					Name:  "no-watch",
					Usage: "do not update graph on watched graph definition file changes",
				},
				cli.StringFlag{
					Name:  "code, c",
					Value: "",
					Usage: "code definition to run",
				},
				cli.StringFlag{
					Name:  "graphviz, g",
					Value: "",
					Usage: "output file for graphviz data",
				},
				cli.StringFlag{
					Name:  "graphviz-filter, gf",
					Value: "dot", // directed graph default
					Usage: "graphviz filter to use",
				},
				// useful for testing multiple instances on same machine
				cli.StringFlag{
					Name:  "hostname",
					Value: "",
					Usage: "hostname to use",
				},
				// if empty, it will startup a new server
				cli.StringFlag{
					Name:   "seed, s",
					Value:  "",
					Usage:  "default etc peer endpoint",
					EnvVar: "MGMT_SEED_ENDPOINT",
				},
				cli.IntFlag{
					Name:   "converged-timeout, t",
					Value:  -1,
					Usage:  "exit after approximately this many seconds in a converged state",
					EnvVar: "MGMT_CONVERGED_TIMEOUT",
				},
				cli.IntFlag{
					Name:   "max-runtime",
					Value:  0,
					Usage:  "exit after a maximum of approximately this many seconds",
					EnvVar: "MGMT_MAX_RUNTIME",
				},
			},
		},
	}
	app.EnableBashCompletion = true
	app.Run(os.Args)
}