// Copyright (c) 2016- Daniel Oaks <daniel@danieloaks.net>
// released under the MIT license

package irc

import (
	"errors"
	"fmt"
	"net"
	"time"

	"strings"

	"encoding/json"

	"github.com/DanielOaks/girc-go/ircmsg"
	"github.com/tidwall/buntdb"
)

const (
	keyDlineEntry = "bans.dline %s"
)

var (
	errNoExistingBan = errors.New("Ban does not exist")
)

// IPRestrictTime contains the expiration info about the given IP.
type IPRestrictTime struct {
	// Duration is how long this block lasts for.
	Duration time.Duration
	// Expires is when this block expires.
	Expires time.Time
}

// IsExpired returns true if the time has expired.
func (iptime *IPRestrictTime) IsExpired() bool {
	return iptime.Expires.Before(time.Now())
}

// IPBanInfo holds info about an IP/net ban.
type IPBanInfo struct {
	// Reason is the ban reason.
	Reason string
	// OperReason is an oper ban reason.
	OperReason string `json:"oper_reason"`
	// Time holds details about the duration, if it exists.
	Time *IPRestrictTime
}

// dLineAddr contains the address itself and expiration time for a given network.
type dLineAddr struct {
	// Address is the address that is blocked.
	Address net.IP
	// Info contains information on the ban.
	Info IPBanInfo
}

// dLineNet contains the net itself and expiration time for a given network.
type dLineNet struct {
	// Network is the network that is blocked.
	Network net.IPNet
	// Info contains information on the ban.
	Info IPBanInfo
}

// DLineManager manages and dlines.
type DLineManager struct {
	// addresses that are dlined
	addresses map[string]*dLineAddr
	// networks that are dlined
	networks map[string]*dLineNet
}

// NewDLineManager returns a new DLineManager.
func NewDLineManager() *DLineManager {
	var dm DLineManager
	dm.addresses = make(map[string]*dLineAddr)
	dm.networks = make(map[string]*dLineNet)
	return &dm
}

// AddNetwork adds a network to the blocked list.
func (dm *DLineManager) AddNetwork(network net.IPNet, length *IPRestrictTime, reason string, operReason string) {
	netString := network.String()
	dln := dLineNet{
		Network: network,
		Info: IPBanInfo{
			Time:       length,
			Reason:     reason,
			OperReason: operReason,
		},
	}
	dm.networks[netString] = &dln
}

// RemoveNetwork removes a network from the blocked list.
func (dm *DLineManager) RemoveNetwork(network net.IPNet) {
	netString := network.String()
	delete(dm.networks, netString)
}

// AddIP adds an IP address to the blocked list.
func (dm *DLineManager) AddIP(addr net.IP, length *IPRestrictTime, reason string, operReason string) {
	addrString := addr.String()
	dla := dLineAddr{
		Address: addr,
		Info: IPBanInfo{
			Time:       length,
			Reason:     reason,
			OperReason: operReason,
		},
	}
	dm.addresses[addrString] = &dla
}

// RemoveIP removes an IP from the blocked list.
func (dm *DLineManager) RemoveIP(addr net.IP) {
	addrString := addr.String()
	delete(dm.addresses, addrString)
}

// CheckIP returns whether or not an IP address was banned, and how long it is banned for.
func (dm *DLineManager) CheckIP(addr net.IP) (isBanned bool, info *IPBanInfo) {
	// check IP addr
	addrString := addr.String()

	addrInfo := dm.addresses[addrString]
	if addrInfo != nil {
		if addrInfo.Info.Time != nil {
			if addrInfo.Info.Time.IsExpired() {
				// ban on IP has expired, remove it from our blocked list
				dm.RemoveIP(addr)
			} else {
				return true, &addrInfo.Info
			}
		} else {
			return true, &addrInfo.Info
		}
	}

	// check networks
	var netsToRemove []net.IPNet

	for _, netInfo := range dm.networks {
		if !netInfo.Network.Contains(addr) {
			continue
		}

		if netInfo.Info.Time != nil {
			if netInfo.Info.Time.IsExpired() {
				// ban on network has expired, remove it from our blocked list
				netsToRemove = append(netsToRemove, netInfo.Network)
			} else {
				return true, &addrInfo.Info
			}
		} else {
			return true, &addrInfo.Info
		}
	}

	// remove expired networks
	for _, expiredNet := range netsToRemove {
		dm.RemoveNetwork(expiredNet)
	}

	// no matches!
	return false, nil
}

// DLINE [MYSELF] [duration] <ip>/<net> [ON <server>] [reason [| oper reason]]
func dlineHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
	// check oper permissions
	if !client.class.Capabilities["oper:local_ban"] {
		client.Send(nil, server.name, ERR_NOPRIVS, client.nick, msg.Command, "Insufficient oper privs")
		return false
	}

	currentArg := 0

	// when setting a ban that covers the oper's current connection, we require them to say
	// "DLINE MYSELF" so that we're sure they really mean it.
	var dlineMyself bool
	if len(msg.Params) > currentArg+1 && strings.ToLower(msg.Params[currentArg]) == "myself" {
		dlineMyself = true
		currentArg++
	}

	// duration
	duration, err := time.ParseDuration(msg.Params[currentArg])
	durationIsUsed := err == nil
	if durationIsUsed {
		currentArg++
	}

	// get host
	if len(msg.Params) < currentArg+1 {
		client.Send(nil, server.name, ERR_NEEDMOREPARAMS, client.nick, msg.Command, "Not enough parameters")
		return false
	}
	hostString := msg.Params[currentArg]
	currentArg++

	// check host
	var hostAddr net.IP
	var hostNet *net.IPNet

	_, hostNet, err = net.ParseCIDR(hostString)
	if err != nil {
		hostAddr = net.ParseIP(hostString)
	}

	if hostAddr == nil && hostNet == nil {
		client.Send(nil, server.name, ERR_UNKNOWNERROR, client.nick, msg.Command, "Could not parse IP address or CIDR network")
		return false
	}

	if hostNet == nil {
		hostString = hostAddr.String()
		if !dlineMyself && hostAddr.Equal(net.ParseIP(IPString(client.socket.conn.RemoteAddr()))) {
			client.Send(nil, server.name, ERR_UNKNOWNERROR, client.nick, msg.Command, "This ban matches you. To DLINE yourself, you must use the command:  /DLINE MYSELF <arguments>")
			return false
		}
	} else {
		hostString = hostNet.String()
		if !dlineMyself && hostNet.Contains(net.ParseIP(IPString(client.socket.conn.RemoteAddr()))) {
			client.Send(nil, server.name, ERR_UNKNOWNERROR, client.nick, msg.Command, "This ban matches you. To DLINE yourself, you must use the command:  /DLINE MYSELF <arguments>")
			return false
		}
	}

	// check remote
	if len(msg.Params) > currentArg && msg.Params[currentArg] == "ON" {
		client.Send(nil, server.name, ERR_UNKNOWNERROR, client.nick, msg.Command, "Remote servers not yet supported")
		return false
	}

	// get comment(s)
	reason := "No reason given"
	operReason := "No reason given"
	if len(msg.Params) > currentArg {
		tempReason := strings.TrimSpace(msg.Params[currentArg])
		if len(tempReason) > 0 && tempReason != "|" {
			tempReasons := strings.SplitN(tempReason, "|", 2)
			if tempReasons[0] != "" {
				reason = tempReasons[0]
			}
			if len(tempReasons) > 1 && tempReasons[1] != "" {
				operReason = tempReasons[1]
			} else {
				operReason = reason
			}
		}
	}

	// assemble ban info
	var banTime *IPRestrictTime
	if durationIsUsed {
		banTime = &IPRestrictTime{
			Duration: duration,
			Expires:  time.Now().Add(duration),
		}
	}

	info := IPBanInfo{
		Reason:     reason,
		OperReason: operReason,
		Time:       banTime,
	}

	// save in datastore
	err = server.store.Update(func(tx *buntdb.Tx) error {
		dlineKey := fmt.Sprintf(keyDlineEntry, hostString)

		// assemble json from ban info
		b, err := json.Marshal(info)
		if err != nil {
			return err
		}

		tx.Set(dlineKey, string(b), nil)

		return nil
	})

	if hostNet == nil {
		server.dlines.AddIP(hostAddr, banTime, reason, operReason)
	} else {
		server.dlines.AddNetwork(*hostNet, banTime, reason, operReason)
	}

	if durationIsUsed {
		client.Notice(fmt.Sprintf("Added temporary (%s) D-Line for %s", duration.String(), hostString))
	} else {
		client.Notice(fmt.Sprintf("Added D-Line for %s", hostString))
	}

	return false
}

func unDLineHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
	// check oper permissions
	if !client.class.Capabilities["oper:local_unban"] {
		client.Send(nil, server.name, ERR_NOPRIVS, client.nick, msg.Command, "Insufficient oper privs")
		return false
	}

	// get host
	hostString := msg.Params[0]

	// check host
	var hostAddr net.IP
	var hostNet *net.IPNet

	_, hostNet, err := net.ParseCIDR(hostString)
	if err != nil {
		hostAddr = net.ParseIP(hostString)
	}

	if hostAddr == nil && hostNet == nil {
		client.Send(nil, server.name, ERR_UNKNOWNERROR, client.nick, msg.Command, "Could not parse IP address or CIDR network")
		return false
	}

	if hostNet == nil {
		hostString = hostAddr.String()
	} else {
		hostString = hostNet.String()
	}

	// save in datastore
	err = server.store.Update(func(tx *buntdb.Tx) error {
		dlineKey := fmt.Sprintf(keyDlineEntry, hostString)

		// check if it exists or not
		val, err := tx.Get(dlineKey)
		if val == "" {
			return errNoExistingBan
		} else if err != nil {
			return err
		}

		tx.Delete(hostString)
		return nil
	})

	if err != nil {
		client.Send(nil, server.name, ERR_UNKNOWNERROR, client.nick, msg.Command, fmt.Sprintf("Could not remove ban [%s]", err.Error()))
	}

	if hostNet == nil {
		server.dlines.RemoveIP(hostAddr)
	} else {
		server.dlines.RemoveNetwork(*hostNet)
	}

	client.Notice(fmt.Sprintf("Removed D-Line for %s", hostString))
	return false
}

func (s *Server) loadDLines() {
	s.dlines = NewDLineManager()

	// load from datastore
	s.store.View(func(tx *buntdb.Tx) error {
		//TODO(dan): We could make this safer
		tx.AscendKeys("bans.dline *", func(key, value string) bool {
			// get address name
			key = key[len("bans.dline "):]

			// load addr/net
			var hostAddr net.IP
			var hostNet *net.IPNet
			_, hostNet, err := net.ParseCIDR(key)
			if err != nil {
				hostAddr = net.ParseIP(key)
			}

			// load ban info
			var info IPBanInfo
			json.Unmarshal([]byte(value), &info)

			// add to the server
			if hostNet == nil {
				s.dlines.AddIP(hostAddr, info.Time, info.Reason, info.OperReason)
			} else {
				s.dlines.AddNetwork(*hostNet, info.Time, info.Reason, info.OperReason)
			}

			return true // true to continue I guess?
		})
		return nil
	})
}