package config

import (
	"crypto/tls"
	"crypto/x509"
	"errors"
	"fmt"
	"io"
	"io/fs"
	"io/ioutil"
	"os"
	"path/filepath"

	"github.com/pelletier/go-toml"
	"google.golang.org/grpc/credentials"
)

type Config struct {
	LogLevel string        `toml:"LogLevel"`
	Server   *ServerConfig `toml:"Server"`
	Client   *ClientConfig `toml:"Client"`
	location string
}
type CertificatePaths struct {
	CertificatePath    string `toml:"CertificatePath"`
	CertificateKeyPath string `toml:"CertificateKeyPath"`
}

type ServerConfig struct {
	GRPC *ServerGRPCConfig `toml:"GRPC"`
	HTTP *ServerHTTPConfig `toml:"HTTP"`
}
type ServerStoreConfig struct {
	Type          string         `toml:"Type"`
	FSStoreConfig *FSStoreConfig `toml:"Filesystem"`
}
type FSStoreConfig struct {
	Dir string `toml:"Dir"`
}
type ServerGRPCConfig struct {
	ListenAddr string            `toml:"ListenAddr"`
	CACerts    *CertificatePaths `toml:"CACerts"`
	Certs      *CertificatePaths `toml:"Certs"`
}
type ServerHTTPConfig struct {
	ListenAddr string `toml:"ListenAddr"`
}

type ClientConfig struct {
	DefaultServer  string            `toml:"DefaultServer"`
	ServerCertPath string            `toml:"ServerCertPath"`
	Certs          *CertificatePaths `toml:"Certs"`
}

func FromDefault() *Config {
	cfg := &Config{
		LogLevel: "INFO",
		Server: &ServerConfig{
			GRPC: &ServerGRPCConfig{
				ListenAddr: ":50051",
				CACerts:    &CertificatePaths{},
				Certs:      &CertificatePaths{},
			},
			HTTP: &ServerHTTPConfig{
				ListenAddr: ":8089",
			},
		},
		Client: &ClientConfig{},
	}

	return cfg
}

func FromReader(r io.Reader) (*Config, error) {
	decoder := toml.NewDecoder(r)
	c := FromDefault()
	if err := decoder.Decode(c); err != nil {
		return nil, fmt.Errorf("unable to read config: %w", err)
	}

	return c, nil
}

func FromFile(path string) (*Config, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, fmt.Errorf("unable to open config-file: %w", err)
	}
	defer f.Close()

	cfg, err := FromReader(f)
	if err == nil {
		cfg.location = path
	}

	return cfg, err
}

func FromDefaultLocations() (*Config, error) {
	defaultLocations := []string{
		"ezshare.toml",
	}
	userConfigDir, err := os.UserConfigDir()
	if err != nil {
		defaultLocations = append(defaultLocations, filepath.Join(userConfigDir, "ezshare", "ezshare.toml"))
	}

	for _, location := range defaultLocations {
		if _, err := os.Stat(location); err == nil {
			return FromFile(location)
		}
	}
	return nil, fmt.Errorf("config not found")
}

func (c *Config) Location() string {
	return c.location
}

func (cp *CertificatePaths) GetCertBytes() ([]byte, error) {
	f, err := os.Open(cp.CertificatePath)
	if err != nil {
		return nil, err
	}
	return ioutil.ReadAll(f)
}

func (cp *CertificatePaths) GetKeyBytes() ([]byte, error) {
	f, err := os.Open(cp.CertificateKeyPath)
	if err != nil {
		return nil, err
	}
	return ioutil.ReadAll(f)
}

func (cc *ClientConfig) ServerCertBytes() ([]byte, error) {
	f, err := os.Open(cc.ServerCertPath)
	if err != nil {
		return nil, fmt.Errorf("unable to open server certificate: %w", err)
	}
	defer f.Close()

	data, err := ioutil.ReadAll(f)
	if err != nil {
		return nil, fmt.Errorf("unable to read client server certificate: %w", err)
	}
	return data, nil
}

func (cc *ClientConfig) Creds() (credentials.TransportCredentials, error) {
	srvCertBytes, err := cc.ServerCertBytes()
	if err != nil {
		return nil, err
	}
	clientCertBytes, err := cc.Certs.GetCertBytes()
	if err != nil {
		return nil, fmt.Errorf("unable to read client cert: %w", err)
	}
	clientKeyBytes, err := cc.Certs.GetKeyBytes()
	if err != nil {
		return nil, fmt.Errorf("unable to read client cert: %w", err)
	}
	certPool := x509.NewCertPool()
	if !certPool.AppendCertsFromPEM(srvCertBytes) {
		return nil, fmt.Errorf("unable to load ca cert")
	}
	clientCert, err := tls.X509KeyPair(clientCertBytes, clientKeyBytes)
	if err != nil {
		return nil, fmt.Errorf("unable to load client cert: %s", err)
	}
	config := &tls.Config{
		Certificates: []tls.Certificate{clientCert},
		RootCAs:      certPool,
	}
	return credentials.NewTLS(config), nil
}

func (c *Config) ToDefaultFile() error {
	userConfigDir, err := os.UserConfigDir()
	if err != nil {
		return err
	}
	configDirPath := filepath.Join(userConfigDir, "ezshare")
	info, err := os.Stat(configDirPath)
	if err != nil {
		if !errors.Is(err, fs.ErrNotExist) {
			return err
		}
		if err := os.Mkdir(configDirPath, 0755); err != nil {
			return fmt.Errorf("unable to create config-dir: %w", err)
		}
	} else {
		if !info.IsDir() {
			return fmt.Errorf("config-directory is not a directory")
		}
	}

	configFilePath := filepath.Join(configDirPath, "ezshare.toml")
	_, err = os.Stat(configFilePath)
	if err != nil {
		if !errors.Is(err, fs.ErrNotExist) {
			return fmt.Errorf("error stating config-file: %w", err)
		}

		f, err := os.Create(configFilePath)
		if err != nil {
			return fmt.Errorf("unable to create config-file: %w", err)
		}
		encoder := toml.NewEncoder(f)
		fmt.Printf("Writing config to '%s'", configFilePath)
		return encoder.Encode(c)
	}
	return fmt.Errorf("config-file already exists")
}