package proxy

import (
	"encoding/json"
	"fmt"
	"log"
	"math/rand"
	"os"
	"sync"
	"time"
)

const (
	defaultCmdPrefix    = ">"
	defaultSendInterval = 0.09
	defaultUserLimit    = 10
	defaultAuthBackend  = "files"
	defaultTelnetAddr   = "[::1]:40010"
	defaultBindAddr     = ":40000"
	defaultListInterval = 300
)

var config Config
var configMu sync.RWMutex

var loadConfigOnce sync.Once

type Server struct {
	Addr      string
	MediaPool string
	Groups    []string
	Fallback  string

	dynamic   bool
	poolAdded time.Time
}

// A Config contains information from the configuration file
// that affects the way the proxy works.
type Config struct {
	NoPlugins        bool
	NoAutoPlugins    bool
	CmdPrefix        string
	RequirePasswd    bool
	SendInterval     float32
	UserLimit        int
	AuthBackend      string
	AuthPostgresConn string
	NoTelnet         bool
	TelnetAddr       string
	BindAddr         string
	DefaultSrv       string
	SrvSelector      string
	Servers          map[string]Server
	ForceDefaultSrv  bool
	KickOnNewPool    bool
	CSMRF            struct {
		NoCSMs          bool
		ChatMsgs        bool
		ItemDefs        bool
		NodeDefs        bool
		NoLimitMapRange bool
		PlayerList      bool
	}
	MapRange   uint32
	DropCSMRF  bool
	Groups     map[string][]string
	UserGroups map[string]string
	List       struct {
		Enable   bool
		Addr     string
		Interval int

		Name     string
		Desc     string
		URL      string
		Creative bool
		Dmg      bool
		PvP      bool
		Game     string
		FarNames bool
		Mods     []string
	}
}

// Conf returns a copy of the Config used by the proxy.
// Any modifications will not affect the original Config.
func Conf() Config {
	loadConfigOnce.Do(func() {
		if err := LoadConfig(); err != nil {
			log.Fatal(err)
		}
	})

	configMu.RLock()
	defer configMu.RUnlock()

	return config.clone()
}

// AddServer dynamically configures a new Server at runtime.
// Servers added in this way are ephemeral and will be lost
// when the proxy shuts down.
// The server must be part of a media pool with at least one
// other member. At least one of the other members always
// needs to be reachable.
// WARNING: Reloading the config will not overwrite servers
// added using this function. The server definition from the
// configuration file will silently be ignored.
func AddServer(name string, s Server) bool {
	configMu.Lock()
	defer configMu.Unlock()

	s.dynamic = true
	s.poolAdded = startTime

	if _, ok := config.Servers[name]; ok {
		return false
	}

	var poolMembers bool
	for _, srv := range config.Servers {
		if !srv.dynamic && srv.MediaPool == s.MediaPool {
			poolMembers = true
		}
	}

	if !poolMembers {
		return false
	}

	config.Servers[name] = s
	return true
}

// RmServer deletes a Server from the Config at runtime.
// Only servers added using AddServer can be deleted at runtime.
// Returns true on success or if the server doesn't exist.
func RmServer(name string) bool {
	configMu.Lock()
	defer configMu.Unlock()

	s, ok := config.Servers[name]
	if !ok {
		return true
	}

	if !s.dynamic {
		return false
	}

	// Can't remove server if players are connected to it
	for cc := range Clts() {
		if cc.ServerName() == name {
			return false
		}
	}

	delete(config.Servers, name)
	return true
}

func (cnf Config) clone() Config {
	newConfig := cnf

	newConfig.Servers = copyMap(cnf.Servers)

	newConfig.Groups = copyMapSlice(cnf.Groups)
	newConfig.UserGroups = copyMap(cnf.UserGroups)

	newConfig.List.Mods = make([]string, len(cnf.List.Mods))
	copy(newConfig.List.Mods, cnf.List.Mods)

	return newConfig
}

// WARNING: Doesn't handle nested maps.
func copyMap[K comparable, V any](in map[K]V) map[K]V {
	out := make(map[K]V)
	for k, v := range in {
		out[k] = v
	}

	return out
}

func copyMapSlice[K comparable, V any](in map[K][]V) map[K][]V {
	out := make(map[K][]V)
	for k, v := range in {
		out[k] = make([]V, len(v))
		copy(out[k], v)
	}

	return out
}

// DefaultServerInfo returns both the name of the default server
// and information about it. The return values are uninitialized
// if no servers exist.
func (cnf Config) DefaultServerInfo() (string, Server) {
	name, ok := cnf.RandomGroupServer(cnf.DefaultSrv)
	if !ok {
		return "", Server{}
	}

	srv, ok := cnf.Servers[name]
	if !ok {
		return "", Server{}
	}

	return name, srv
}

// DefaultServerName returns the name of the default server.
// If no servers exist it returns an empty string.
func (cnf Config) DefaultServerName() string {
	name, _ := cnf.DefaultServerInfo()
	return name
}

// DefaultServer returns information about the default server.
// If no servers exist the returned struct will be uninitialized.
// This is a faster shortcut for Config.Servers[Config.DefaultServerName()].
// You should thus only use this method or the DefaultServerInfo method.
func (cnf Config) DefaultServer() Server {
	_, srv := cnf.DefaultServerInfo()
	return srv
}

// Pools returns all media pools and their member servers.
func (cnf Config) Pools() map[string]map[string]Server {
	pools := make(map[string]map[string]Server)
	for name, srv := range cnf.Servers {
		if pools[srv.MediaPool] == nil {
			pools[srv.MediaPool] = make(map[string]Server)
		}

		pools[srv.MediaPool][name] = srv
	}

	return pools
}

// Groups returns all server groups and their member servers.
func (cnf Config) ServerGroups() map[string]map[string]Server {
	groups := make(map[string]map[string]Server)
	for name, srv := range cnf.Servers {
		for _, group := range srv.Groups {
			if groups[group] == nil {
				groups[group] = make(map[string]Server)
			}

			groups[group][name] = srv
		}
	}

	return groups
}

// RandomGroupServer returns the name of a random member of a server group
// or the input string if it is a valid, existent server name.
// It also returns a boolean indicating success.
// The returned string is blank if there is a failure,
// i.e. if the input string is neither a server nor a group.
func (cnf Config) RandomGroupServer(search string) (string, bool) {
	candidates := make([]string, 0)
	for name, srv := range cnf.Servers {
		if name == search {
			return name, true
		}

		for _, grp := range srv.Groups {
			if grp == search {
				candidates = append(candidates, name)
			}
		}
	}

	if len(candidates) == 0 {
		return "", false
	}

	return candidates[rand.Intn(len(candidates))], true
}

// LoadConfig attempts to parse the configuration file.
// It leaves the config unchanged if there is an error
// and returns the error.
func LoadConfig() error {
	configMu.Lock()
	defer configMu.Unlock()

	oldConf := config.clone()

	config.CmdPrefix = defaultCmdPrefix
	config.SendInterval = defaultSendInterval
	config.UserLimit = defaultUserLimit
	config.AuthBackend = defaultAuthBackend
	config.TelnetAddr = defaultTelnetAddr
	config.BindAddr = defaultBindAddr
	config.Servers = make(map[string]Server)
	config.Groups = make(map[string][]string)
	config.UserGroups = make(map[string]string)
	config.List.Interval = defaultListInterval
	config.List.Mods = make([]string, 0)

	f, err := os.OpenFile(Path("config.json"), os.O_RDWR|os.O_CREATE, 0666)
	if err != nil {
		config = oldConf.clone()
		return err
	}
	defer f.Close()

	if fi, _ := f.Stat(); fi.Size() == 0 {
		f.WriteString("{\n\t\n}\n")
		f.Seek(0, os.SEEK_SET)
	}

	decoder := json.NewDecoder(f)
	if err := decoder.Decode(&config); err != nil {
		config = oldConf.clone()
		return err
	}

	// Dynamic servers shouldn't be deleted silently.
	for name, srv := range oldConf.Servers {
		if srv.dynamic {
			if _, ok := config.Servers[name]; ok {
				config = oldConf.clone()
				return fmt.Errorf("duplicate server %s", name)
			}

			config.Servers[name] = srv
		} else {
			if _, ok := config.Servers[name]; ok {
				continue
			}

			for cc := range Clts() {
				if cc.ServerName() == name {
					config = oldConf.clone()
					return fmt.Errorf("can't delete server %s with players", name)
				}
			}
		}
	}

	for name, srv := range config.Servers {
		if srv.MediaPool == "" {
			srv.MediaPool = name
			config.Servers[name] = srv
		}
	}

	poolKickOnce := sync.OnceFunc(func() {
		for cc := range Clts() {
			cc.Kick("A server with new media has been added to the network. Please reconnect to access it.")
		}
	})

	// Set creation timestamp on new non-dynamic media pools.
	for name, srv := range config.Servers {
		if _, ok := oldConf.Servers[name]; !ok && !srv.dynamic {
			if poolServers, ok := oldConf.Pools()[srv.MediaPool]; ok {
				for _, s2 := range poolServers {
					srv.poolAdded = s2.poolAdded
				}
			} else { // New media pool.
				srv.poolAdded = time.Now()

				if config.KickOnNewPool {
					poolKickOnce()
				}
			}

			config.Servers[name] = srv
		}
	}

	log.Print("load config")
	return nil
}