package service

import (
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net"
	"os"
	"path"

	"github.com/spf13/viper"
	"golang.org/x/crypto/bcrypt"
)

type UnauthorizedError string

func (uae UnauthorizedError) Error() string {
	return "Invalid user or password"
}

type UserConfig struct {
	db *viper.Viper

	UserName string
	PassWord string
	Domain   string
	Router   UserConfigRouter
	Others   []UserConfigOther
}

type UserConfigRouter struct {
	Hostname string
	NFT      UserConfigNFT
}

type UserConfigOther struct {
	Hostname   string
	V6IID      string
	RegisterV4 bool
	NFT        UserConfigNFT
}

type UserConfigNFT struct {
	Table string
	Set4  string
	Set6  string
}

func LoadConfigFile(configFile string) (*UserConfig, error) {
	configFile = path.Clean(configFile)
	log.Printf("Trying to load config file %s", configFile)

	if _, err := os.Stat(configFile); err != nil {
		log.Printf("cannot stat the file %s: %v", configFile, err)
		return nil, UnauthorizedError("cannot stat")
	}
	v := viper.New()
	v.SetConfigFile(configFile)
	err := v.ReadInConfig()

	if err != nil {
		return nil, fmt.Errorf("failed to parse config file %s: %v", configFile, err)
	}

	result := &UserConfig{db: v}

	err = result.db.Unmarshal(result)
	if err != nil {
		return nil, fmt.Errorf("failed to unmarshal config file %s: %v", configFile, err)
	}

	err = result.Validate()
	if err != nil {
		return nil, fmt.Errorf("failed to parse config: %v", err)
	}

	return result, nil
}

func LoadConfigForUser(username string, password string) (*UserConfig, error) {
	configFile := fmt.Sprintf("%s/%s.yml", C.Users.ConfigDir, username)

	result, err := LoadConfigFile(configFile)
	if err != nil {
		return nil, err
	}

	err = result.Authenticate(password)
	if err != nil {
		log.Printf("Failed to check password")
		return nil, UnauthorizedError("pwcheck failed")
	}

	return result, nil
}

func HashPassword(pw []byte) (string, error) {
	hash, err := bcrypt.GenerateFromPassword(pw, bcrypt.DefaultCost)
	if err != nil {
		return "", fmt.Errorf("failed to create password hash: %v", err)
	}
	return string(hash), nil
}

func (uc *UserConfig) Authenticate(pwToCheck string) error {
	hashedPassword := []byte(uc.PassWord)
	bytePwToCheck := []byte(pwToCheck)

	err := bcrypt.CompareHashAndPassword(hashedPassword, bytePwToCheck)

	return err
}

func (uco *UserConfigOther) ConvertIIDToAddress(localNet *net.IPNet) net.IP {
	if localNet == nil {
		return nil
	}
	out := make(net.IP, net.IPv6len)
	ipiid := net.ParseIP(uco.V6IID)
	for i := 0; i < net.IPv6len; i++ {
		// We take the corresponding byte from the IID and mask it out with the
		// inversed Mask of the network we got (in essence a Host Mask). This
		// leaves us those bits, that are not taken by the netmask, so that we
		// can OR all this together.
		maskedIID := ipiid[i] &^ localNet.Mask[i]
		out[i] = localNet.IP[i] | maskedIID
	}
	return out
}

func (ucn *UserConfigNFT) ValidateSetNames() error {
	if ucn.Set4 == "" && ucn.Set6 == "" {
		return nil
	}
	if ucn.Table == "" {
		return errors.New("NFT table name undefined")
	}
	if ucn.Set4 == ucn.Set6 {
		return errors.New("set4 and set6 are identical")
	}

	return nil
}

func (uc *UserConfig) Validate() error {
	if err := uc.Router.NFT.ValidateSetNames(); err != nil {
		return fmt.Errorf("router NFT validation failed: %v", err)
	}
	if uc.Router.Hostname == "" {
		return errors.New("router record has no Hostname")
	}

	dnsnames := make(map[string]bool)
	dnsnames[uc.Router.Hostname] = true

	for i, other := range uc.Others {
		if other.Hostname == "" {
			return fmt.Errorf("other record #%d has no Hostname", i)
		}
		if dnsnames[other.Hostname] {
			return fmt.Errorf("the Hostname %s is used twice", other.Hostname)
		}
		dnsnames[other.Hostname] = true
		if err := other.NFT.ValidateSetNames(); err != nil {
			return fmt.Errorf("other %s NFT validation failed: %v", other.Hostname, err)
		}
		if other.V6IID == "" {
			return fmt.Errorf("other record %s has no V6IID", other.Hostname)
		}
		iidIP := net.ParseIP(other.V6IID)
		if iidIP == nil {
			return fmt.Errorf("other record %s has invalid V6IID %s", other.Hostname, other.V6IID)
		}
		if iidIP.To4() != nil {
			return fmt.Errorf("other record %s IID looks like an IPv4 Address", other.Hostname)
		}
	}

	return nil
}

func (uc *UserConfig) GetStateFileName() string {
	return fmt.Sprintf("%s/%s.yml", C.Users.StateDir, uc.UserName)
}

func (uc *UserConfig) PrettyPrint() string {
	s, err := json.MarshalIndent(uc, "", " ")
	if err != nil {
		log.Fatalf("Failed to pretty print UpdateConfig via JSON: %v", err)
	}
	return string(s)
}