// "sync" sub-command: sync data to remote hosts

// Copyright (C) 2021  Simon Ruderich
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"os/signal"
	"sort"
	"strings"
	"sync"

	"golang.org/x/term"

	"ruderich.org/simon/safcm"
	"ruderich.org/simon/safcm/cmd/safcm/config"
	"ruderich.org/simon/safcm/rpc"
)

type Sync struct {
	host *config.Host

	config    *config.Config      // global configuration
	allHosts  *config.Hosts       // known hosts
	allGroups map[string][]string // known groups

	events chan<- Event // all events generated by/for this host

	isTTY bool
}

type Event struct {
	Host *config.Host

	// Only one of Error, Log and ConnEvent is set in a single event
	Error     error
	Log       Log
	ConnEvent rpc.ConnEvent

	Escaped bool // true if untrusted input is already escaped
}

type Log struct {
	Level safcm.LogLevel
	Text  string
}

func MainSync(args []string) error {
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr,
			"usage: %s sync [<options>] <host|group...>\n",
			args[0])
		flag.PrintDefaults()
	}

	optionDryRun := flag.Bool("n", false,
		"dry-run, show diff but don't perform any changes")
	optionQuiet := flag.Bool("q", false,
		"hide successful, non-trigger commands with no output from host changes listing")
	optionLog := flag.String("log", "info", "set log `level`; "+
		"levels: error, info, verbose, debug, debug2, debug3")
	optionSshConfig := flag.String("sshconfig", "",
		"`path` to ssh configuration file; used for tests")

	flag.CommandLine.Parse(args[2:])

	var level safcm.LogLevel
	switch *optionLog {
	case "error":
		level = safcm.LogError
	case "info":
		level = safcm.LogInfo
	case "verbose":
		level = safcm.LogVerbose
	case "debug":
		level = safcm.LogDebug
	case "debug2":
		level = safcm.LogDebug2
	case "debug3":
		level = safcm.LogDebug3
	default:
		return fmt.Errorf("invalid -log value %q", *optionLog)
	}

	names := flag.Args()
	if len(names) == 0 {
		flag.Usage()
		os.Exit(1)
	}

	cfg, allHosts, allGroups, err := LoadBaseFiles()
	if err != nil {
		return err
	}
	cfg.DryRun = *optionDryRun
	cfg.Quiet = *optionQuiet
	cfg.LogLevel = level
	cfg.SshConfig = *optionSshConfig

	toSync, err := hostsToSync(names, allHosts, allGroups)
	if err != nil {
		return err
	}
	if len(toSync) == 0 {
		return fmt.Errorf("no hosts found")
	}

	isTTY := term.IsTerminal(int(os.Stdout.Fd()))

	done := make(chan bool)
	// Collect events from all hosts and print them
	events := make(chan Event)
	go func() {
		var failed bool
		for {
			x := <-events
			if x.Host == nil {
				break
			}
			logEvent(x, cfg.LogLevel, isTTY, &failed)
		}
		done <- failed
	}()

	hostsLeft := make(map[string]bool)
	for _, x := range toSync {
		hostsLeft[x.Name] = true
	}
	var hostsLeftMutex sync.Mutex // protects hostsLeft

	// Show unfinished hosts on Ctrl-C
	sigint := make(chan os.Signal, 1)   // buffered for Notify()
	signal.Notify(sigint, os.Interrupt) // = SIGINT = Ctrl-C
	go func() {
		// Running `ssh` processes get killed by SIGINT which is sent
		// to all processes

		<-sigint
		log.Print("Received SIGINT, aborting ...")

		// Print all queued events
		events <- Event{} // poison pill
		<-done
		// "races" with <-done in the main function and will hang here
		// if the other is faster. This is fine because then all hosts
		// were synced successfully.

		hostsLeftMutex.Lock()
		var hosts []string
		for x := range hostsLeft {
			hosts = append(hosts, x)
		}
		sort.Strings(hosts)
		log.Fatalf("Failed to sync %s", strings.Join(hosts, ", "))
	}()

	// Sync all hosts concurrently
	var wg sync.WaitGroup
	for _, x := range toSync {
		x := x

		// Once in sync.Host() and once in the go func below
		wg.Add(2)

		go func() {
			sync := Sync{
				host:      x,
				config:    cfg,
				allHosts:  allHosts,
				allGroups: allGroups,
				events:    events,
				isTTY:     isTTY,
			}
			err := sync.Host(&wg)
			if err != nil {
				events <- Event{
					Host:  x,
					Error: err,
				}
			}
			wg.Done()

			hostsLeftMutex.Lock()
			defer hostsLeftMutex.Unlock()
			delete(hostsLeft, x.Name)
		}()
	}

	wg.Wait()
	events <- Event{} // poison pill
	failed := <-done

	if failed {
		// Exit instead of returning an error to prevent an extra log
		// message from main()
		os.Exit(1)
	}
	return nil
}

// hostsToSync returns the list of hosts to sync based on the command line
// arguments.
//
// Full host and group matches are required to prevent unexpected behavior. No
// arguments does not expand to all hosts to prevent accidents; "all" can be
// used instead. Both host and group names are permitted as these are unique.
//
// TODO: Add option to permit partial/glob matches
func hostsToSync(names []string, allHosts *config.Hosts,
	allGroups map[string][]string) ([]*config.Host, error) {

	detectedMap := make(map[string]bool)
	for _, x := range config.TransitivelyDetectedGroups(allGroups) {
		detectedMap[x] = true
	}

	const detectedErr = `

Groups depending on "detected" groups cannot be used to select hosts as these
are only available after the hosts were contacted.
`

	nameMap := make(map[string]bool)
	for _, x := range names {
		if detectedMap[x] {
			return nil, fmt.Errorf(
				"group %q depends on \"detected\" groups%s",
				x, detectedErr)
		}
		nameMap[x] = true
	}
	nameMatched := make(map[string]bool)
	// To detect typos we must check all given names but only want to add
	// each match once
	hostMatched := make(map[string]bool)

	var res []*config.Host
	for _, host := range allHosts.List {
		if nameMap[host.Name] {
			res = append(res, host)
			hostMatched[host.Name] = true
			nameMatched[host.Name] = true
		}

		groups, err := config.ResolveHostGroups(host.Name,
			allGroups, nil)
		if err != nil {
			return nil, err
		}
		for _, x := range groups {
			if nameMap[x] {
				if !hostMatched[host.Name] {
					res = append(res, host)
					hostMatched[host.Name] = true
				}
				nameMatched[x] = true
			}
		}
	}

	// Warn about unmatched names to detect typos
	if len(nameMap) != len(nameMatched) {
		var unmatched []string
		for x := range nameMap {
			if !nameMatched[x] {
				unmatched = append(unmatched,
					fmt.Sprintf("%q", x))
			}
		}
		sort.Strings(unmatched)
		return nil, fmt.Errorf("hosts/groups not found: %s",
			strings.Join(unmatched, " "))
	}

	return res, nil
}

func logEvent(x Event, level safcm.LogLevel, isTTY bool, failed *bool) {
	// We have multiple event sources so this is somewhat ugly.
	var prefix, data string
	var color Color
	if x.Error != nil {
		prefix = "[error]"
		data = x.Error.Error()
		color = ColorRed
		// We logged an error, tell the caller
		*failed = true
	} else if x.Log.Level != 0 {
		// LogError and LogDebug3 should not occur here
		switch x.Log.Level {
		case safcm.LogInfo:
			prefix = "[info]"
		case safcm.LogVerbose:
			prefix = "[verbose]"
		case safcm.LogDebug:
			prefix = "[debug]"
		case safcm.LogDebug2:
			prefix = "[debug2]"
		default:
			prefix = fmt.Sprintf("[INVALID=%d]", x.Log.Level)
			color = ColorRed
		}
		data = x.Log.Text
	} else {
		switch x.ConnEvent.Type {
		case rpc.ConnEventStderr:
			prefix = "[stderr]"
		case rpc.ConnEventDebug:
			prefix = "[debug3]"
		case rpc.ConnEventUpload:
			if level < safcm.LogInfo {
				return
			}
			prefix = "[info]"
			x.ConnEvent.Data = "remote helper upload in progress"
		default:
			prefix = fmt.Sprintf("[INVALID=%d]", x.ConnEvent.Type)
			color = ColorRed
		}
		data = x.ConnEvent.Data
	}

	host := x.Host.Name
	if color != 0 {
		host = ColorString(isTTY, color, host)
	}
	// Make sure to escape control characters to prevent terminal
	// injection attacks
	if !x.Escaped {
		data = EscapeControlCharacters(isTTY, data)
	}
	log.Printf("%-9s [%s] %s", prefix, host, data)
}

func (s *Sync) Host(wg *sync.WaitGroup) error {
	conn := rpc.NewConn(s.config.LogLevel >= safcm.LogDebug3)
	// Pass all connection events to main loop
	go func() {
		for {
			x, ok := <-conn.Events
			if !ok {
				break
			}
			s.events <- Event{
				Host:      s.host,
				ConnEvent: x,
			}
		}
		wg.Done()
	}()

	// Connect to remote host
	err := conn.DialSSH(s.host.SshUser, s.host.Name, s.config.SshConfig)
	if err != nil {
		return err
	}
	defer conn.Kill()

	// Collect information about remote host
	detectedGroups, err := s.hostInfo(conn)
	if err != nil {
		return err
	}

	// Sync state to remote host
	err = s.hostSync(conn, detectedGroups)
	if err != nil {
		return err
	}

	// Terminate connection to remote host
	err = conn.Send(safcm.MsgQuitReq{})
	if err != nil {
		return err
	}
	_, err = conn.Recv()
	if err != nil {
		return err
	}
	err = conn.Wait()
	if err != nil {
		return err
	}

	return nil
}

func (s *Sync) logf(level safcm.LogLevel, escaped bool,
	format string, a ...interface{}) {

	if s.config.LogLevel < level {
		return
	}
	s.events <- Event{
		Host: s.host,
		Log: Log{
			Level: level,
			Text:  fmt.Sprintf(format, a...),
		},
		Escaped: escaped,
	}
}
func (s *Sync) logDebugf(format string, a ...interface{}) {
	s.logf(safcm.LogDebug, false, format, a...)
}
func (s *Sync) logVerbosef(format string, a ...interface{}) {
	s.logf(safcm.LogVerbose, false, format, a...)
}

// sendRecv sends a message over conn and waits for the response. Any MsgLog
// messages received before the final (non MsgLog) response are passed to
// s.log.
func (s *Sync) sendRecv(conn *rpc.Conn, msg safcm.Msg) (safcm.Msg, error) {
	err := conn.Send(msg)
	if err != nil {
		return nil, err
	}
	for {
		x, err := conn.Recv()
		if err != nil {
			return nil, err
		}
		log, ok := x.(safcm.MsgLog)
		if ok {
			s.logf(log.Level, false, "%s", log.Text)
			continue
		}
		return x, nil
	}
}