// Copyright (c) 2012-2014 Jeremy Latt
// Copyright (c) 2014-2015 Edmund Huber
// Copyright (c) 2016-2017 Daniel Oaks <daniel@danieloaks.net>
// released under the MIT license

package irc

import (
	"crypto/tls"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"net"
	"strings"
	"time"

	cloak "github.com/oragono/oragono/irc/cloaking"
	"github.com/oragono/oragono/irc/custime"
	"github.com/oragono/oragono/irc/logger"

	"code.cloudfoundry.org/bytefmt"

	"gopkg.in/yaml.v2"
)

// PassConfig holds the connection password.
type PassConfig struct {
	Password string
}

// TLSListenConfig defines configuration options for listening on TLS.
type TLSListenConfig struct {
	Cert string
	Key  string
}

// Config returns the TLS contiguration assicated with this TLSListenConfig.
func (conf *TLSListenConfig) Config() (*tls.Config, error) {
	cert, err := tls.LoadX509KeyPair(conf.Cert, conf.Key)
	if err != nil {
		return nil, errors.New("tls cert+key: invalid pair")
	}

	return &tls.Config{
		Certificates: []tls.Certificate{cert},
	}, err
}

// PasswordBytes returns the bytes represented by the password hash.
func (conf *PassConfig) PasswordBytes() []byte {
	bytes, err := DecodePasswordHash(conf.Password)
	if err != nil {
		log.Fatal("decode password error: ", err)
	}
	return bytes
}

// AccountRegistrationConfig controls account registration.
type AccountRegistrationConfig struct {
	Enabled          bool
	EnabledCallbacks []string `yaml:"enabled-callbacks"`
	Callbacks        struct {
		Mailto struct {
			Server string
			Port   int
			TLS    struct {
				Enabled            bool
				InsecureSkipVerify bool   `yaml:"insecure_skip_verify"`
				ServerName         string `yaml:"servername"`
			}
			Username             string
			Password             string
			Sender               string
			VerifyMessageSubject string `yaml:"verify-message-subject"`
			VerifyMessage        string `yaml:"verify-message"`
		}
	}
}

// ChannelRegistrationConfig controls channel registration.
type ChannelRegistrationConfig struct {
	Enabled bool
}

// OperClassConfig defines a specific operator class.
type OperClassConfig struct {
	Title        string
	WhoisLine    string
	Extends      string
	Capabilities []string
}

// OperConfig defines a specific operator's configuration.
type OperConfig struct {
	Class     string
	Vhost     string
	WhoisLine string `yaml:"whois-line"`
	Password  string
	Modes     string
}

// PasswordBytes returns the bytes represented by the password hash.
func (conf *OperConfig) PasswordBytes() []byte {
	bytes, err := DecodePasswordHash(conf.Password)
	if err != nil {
		log.Fatal("decode password error: ", err)
	}
	return bytes
}

// RestAPIConfig controls the integrated REST API.
type RestAPIConfig struct {
	Enabled bool
	Listen  string
}

// ConnectionLimitsConfig controls the automated connection limits.
type ConnectionLimitsConfig struct {
	Enabled     bool
	CidrLenIPv4 int `yaml:"cidr-len-ipv4"`
	CidrLenIPv6 int `yaml:"cidr-len-ipv6"`
	IPsPerCidr  int `yaml:"ips-per-subnet"`
	Exempted    []string
}

// ConnectionThrottleConfig controls the automated connection throttling.
type ConnectionThrottleConfig struct {
	Enabled            bool
	CidrLenIPv4        int           `yaml:"cidr-len-ipv4"`
	CidrLenIPv6        int           `yaml:"cidr-len-ipv6"`
	ConnectionsPerCidr int           `yaml:"max-connections"`
	DurationString     string        `yaml:"duration"`
	Duration           time.Duration `yaml:"duration-time"`
	BanDurationString  string        `yaml:"ban-duration"`
	BanDuration        time.Duration
	BanMessage         string `yaml:"ban-message"`
	Exempted           []string
}

// LoggingConfig controls a single logging method.
type LoggingConfig struct {
	Method        string
	MethodStdout  bool
	MethodStderr  bool
	MethodFile    bool
	Filename      string
	TypeString    string       `yaml:"type"`
	Types         []string     `yaml:"real-types"`
	ExcludedTypes []string     `yaml:"real-excluded-types"`
	LevelString   string       `yaml:"level"`
	Level         logger.Level `yaml:"level-real"`
}

// LineLenConfig controls line lengths.
type LineLenConfig struct {
	Tags int
	Rest int
}

// STSConfig controls the STS configuration/
type STSConfig struct {
	Enabled        bool
	Duration       time.Duration `yaml:"duration-real"`
	DurationString string        `yaml:"duration"`
	Port           int
	Preload        bool
}

// Value returns the STS value to advertise in CAP
func (sts *STSConfig) Value() string {
	val := fmt.Sprintf("duration=%d,", int(sts.Duration.Seconds()))
	if sts.Enabled && sts.Port > 0 {
		val += fmt.Sprintf(",port=%d", sts.Port)
	}
	if sts.Enabled && sts.Preload {
		val += ",preload"
	}
	return val
}

// StackImpactConfig is the config used for StackImpact's profiling.
type StackImpactConfig struct {
	Enabled  bool
	AgentKey string `yaml:"agent-key"`
	AppName  string `yaml:"app-name"`
}

// Config defines the overall configuration.
type Config struct {
	Network struct {
		Name       string
		IPCloaking cloak.Config `yaml:"ip-cloaking"`
	}

	Server struct {
		PassConfig
		Password           string
		Name               string
		Listen             []string
		Wslisten           string                      `yaml:"ws-listen"`
		TLSListeners       map[string]*TLSListenConfig `yaml:"tls-listeners"`
		STS                STSConfig
		RestAPI            RestAPIConfig `yaml:"rest-api"`
		CheckIdent         bool          `yaml:"check-ident"`
		MOTD               string
		MaxSendQString     string `yaml:"max-sendq"`
		MaxSendQBytes      uint64
		ConnectionLimits   ConnectionLimitsConfig   `yaml:"connection-limits"`
		ConnectionThrottle ConnectionThrottleConfig `yaml:"connection-throttling"`
	}

	Datastore struct {
		Path string
	}

	Accounts struct {
		Registration          AccountRegistrationConfig
		AuthenticationEnabled bool `yaml:"authentication-enabled"`
	}

	Channels struct {
		Registration ChannelRegistrationConfig
	}

	OperClasses map[string]*OperClassConfig `yaml:"oper-classes"`

	Opers map[string]*OperConfig

	Logging []LoggingConfig

	Debug struct {
		StackImpact StackImpactConfig
	}

	Limits struct {
		AwayLen        uint          `yaml:"awaylen"`
		ChanListModes  uint          `yaml:"chan-list-modes"`
		ChannelLen     uint          `yaml:"channellen"`
		KickLen        uint          `yaml:"kicklen"`
		MonitorEntries uint          `yaml:"monitor-entries"`
		NickLen        uint          `yaml:"nicklen"`
		TopicLen       uint          `yaml:"topiclen"`
		WhowasEntries  uint          `yaml:"whowas-entries"`
		LineLen        LineLenConfig `yaml:"linelen"`
	}
}

// OperClass defines an assembled operator class.
type OperClass struct {
	Title        string
	WhoisLine    string          `yaml:"whois-line"`
	Capabilities map[string]bool // map to make lookups much easier
}

// OperatorClasses returns a map of assembled operator classes from the given config.
func (conf *Config) OperatorClasses() (*map[string]OperClass, error) {
	ocs := make(map[string]OperClass)

	// loop from no extends to most extended, breaking if we can't add any more
	lenOfLastOcs := -1
	for {
		if lenOfLastOcs == len(ocs) {
			return nil, errors.New("OperClasses contains a looping dependency, or a class extends from a class that doesn't exist")
		}
		lenOfLastOcs = len(ocs)

		var anyMissing bool
		for name, info := range conf.OperClasses {
			_, exists := ocs[name]
			_, extendsExists := ocs[info.Extends]
			if exists {
				// class already exists
				continue
			} else if len(info.Extends) > 0 && !extendsExists {
				// class we extend on doesn't exist
				_, exists := conf.OperClasses[info.Extends]
				if !exists {
					return nil, fmt.Errorf("Operclass [%s] extends [%s], which doesn't exist", name, info.Extends)
				}
				anyMissing = true
				continue
			}

			// create new operclass
			var oc OperClass
			oc.Capabilities = make(map[string]bool)

			// get inhereted info from other operclasses
			if len(info.Extends) > 0 {
				einfo, _ := ocs[info.Extends]

				for capab := range einfo.Capabilities {
					oc.Capabilities[capab] = true
				}
			}

			// add our own info
			oc.Title = info.Title
			for _, capab := range info.Capabilities {
				oc.Capabilities[capab] = true
			}
			if len(info.WhoisLine) > 0 {
				oc.WhoisLine = info.WhoisLine
			} else {
				oc.WhoisLine = "is a"
				if strings.Contains(strings.ToLower(string(oc.Title[0])), "aeiou") {
					oc.WhoisLine += "n"
				}
				oc.WhoisLine += " "
				oc.WhoisLine += oc.Title
			}

			ocs[name] = oc
		}

		if !anyMissing {
			// we've got every operclass!
			break
		}
	}

	return &ocs, nil
}

// Oper represents a single assembled operator's config.
type Oper struct {
	Class     *OperClass
	WhoisLine string
	Vhost     string
	Pass      []byte
	Modes     string
}

// Operators returns a map of operator configs from the given OperClass and config.
func (conf *Config) Operators(oc *map[string]OperClass) (map[string]Oper, error) {
	operators := make(map[string]Oper)
	for name, opConf := range conf.Opers {
		var oper Oper

		// oper name
		name, err := CasefoldName(name)
		if err != nil {
			return nil, fmt.Errorf("Could not casefold oper name: %s", err.Error())
		}

		oper.Pass = opConf.PasswordBytes()
		oper.Vhost = opConf.Vhost
		class, exists := (*oc)[opConf.Class]
		if !exists {
			return nil, fmt.Errorf("Could not load operator [%s] - they use operclass [%s] which does not exist", name, opConf.Class)
		}
		oper.Class = &class
		if len(opConf.WhoisLine) > 0 {
			oper.WhoisLine = opConf.WhoisLine
		} else {
			oper.WhoisLine = class.WhoisLine
		}
		oper.Modes = strings.TrimSpace(opConf.Modes)

		// successful, attach to list of opers
		operators[name] = oper
	}
	return operators, nil
}

// TLSListeners returns a list of TLS listeners and their configs.
func (conf *Config) TLSListeners() map[string]*tls.Config {
	tlsListeners := make(map[string]*tls.Config)
	for s, tlsListenersConf := range conf.Server.TLSListeners {
		config, err := tlsListenersConf.Config()
		if err != nil {
			log.Fatal(err)
		}
		tlsListeners[s] = config
	}
	return tlsListeners
}

// LoadConfig loads the given YAML configuration file.
func LoadConfig(filename string) (config *Config, err error) {
	data, err := ioutil.ReadFile(filename)
	if err != nil {
		return nil, err
	}

	err = yaml.Unmarshal(data, &config)
	if err != nil {
		return nil, err
	}

	// we need this so PasswordBytes returns the correct info
	if config.Server.Password != "" {
		config.Server.PassConfig.Password = config.Server.Password
	}

	if config.Network.Name == "" {
		return nil, errors.New("Network name missing")
	}
	if config.Server.Name == "" {
		return nil, errors.New("Server name missing")
	}
	if !IsHostname(config.Server.Name) {
		return nil, errors.New("Server name must match the format of a hostname")
	}
	if config.Datastore.Path == "" {
		return nil, errors.New("Datastore path missing")
	}
	if len(config.Server.Listen) == 0 {
		return nil, errors.New("Server listening addresses missing")
	}
	if config.Limits.NickLen < 1 || config.Limits.ChannelLen < 2 || config.Limits.AwayLen < 1 || config.Limits.KickLen < 1 || config.Limits.TopicLen < 1 {
		return nil, errors.New("Limits aren't setup properly, check them and make them sane")
	}
	if config.Server.STS.Enabled {
		config.Server.STS.Duration, err = custime.ParseDuration(config.Server.STS.DurationString)
		if err != nil {
			return nil, fmt.Errorf("Could not parse STS duration: %s", err.Error())
		}
		if config.Server.STS.Port < 0 || config.Server.STS.Port > 65535 {
			return nil, fmt.Errorf("STS port is incorrect, should be 0 if disabled: %d", config.Server.STS.Port)
		}
	}
	if config.Network.IPCloaking.Enabled {
		_, err := cloak.IPv4(net.ParseIP("8.8.8.8"), config.Network.IPCloaking)
		if err != nil {
			return nil, fmt.Errorf("IPv4 cloaking config is incorrect: %s", err.Error())
		}
	}
	if config.Server.ConnectionThrottle.Enabled {
		config.Server.ConnectionThrottle.Duration, err = time.ParseDuration(config.Server.ConnectionThrottle.DurationString)
		if err != nil {
			return nil, fmt.Errorf("Could not parse connection-throttle duration: %s", err.Error())
		}
		config.Server.ConnectionThrottle.BanDuration, err = time.ParseDuration(config.Server.ConnectionThrottle.BanDurationString)
		if err != nil {
			return nil, fmt.Errorf("Could not parse connection-throttle ban-duration: %s", err.Error())
		}
	}
	if config.Limits.LineLen.Tags < 512 || config.Limits.LineLen.Rest < 512 {
		return nil, errors.New("Line lengths must be 512 or greater (check the linelen section under server->limits)")
	}
	var newLogConfigs []LoggingConfig
	for _, logConfig := range config.Logging {
		// methods
		methods := make(map[string]bool)
		for _, method := range strings.Split(logConfig.Method, " ") {
			if len(method) > 0 {
				methods[strings.ToLower(method)] = true
			}
		}
		if methods["file"] && logConfig.Filename == "" {
			return nil, errors.New("Logging configuration specifies 'file' method but 'filename' is empty")
		}
		logConfig.MethodFile = methods["file"]
		logConfig.MethodStdout = methods["stdout"]
		logConfig.MethodStderr = methods["stderr"]

		// levels
		level, exists := logger.LogLevelNames[strings.ToLower(logConfig.LevelString)]
		if !exists {
			return nil, fmt.Errorf("Could not translate log leve [%s]", logConfig.LevelString)
		}
		logConfig.Level = level

		// types
		for _, typeStr := range strings.Split(logConfig.TypeString, " ") {
			if len(typeStr) == 0 {
				continue
			}
			if typeStr == "-" {
				return nil, errors.New("Encountered logging type '-' with no type to exclude")
			}
			if typeStr[0] == '-' {
				typeStr = typeStr[1:]
				logConfig.ExcludedTypes = append(logConfig.ExcludedTypes, typeStr)
			} else {
				logConfig.Types = append(logConfig.Types, typeStr)
			}
		}
		if len(logConfig.Types) < 1 {
			return nil, errors.New("Logger has no types to log")
		}

		newLogConfigs = append(newLogConfigs, logConfig)
	}
	config.Logging = newLogConfigs

	config.Server.MaxSendQBytes, err = bytefmt.ToBytes(config.Server.MaxSendQString)
	if err != nil {
		return nil, fmt.Errorf("Could not parse maximum SendQ size (make sure it only contains whole numbers): %s", err.Error())
	}

	return config, nil
}