// Copyright 2022 Cloudbase Solutions SRL
//
//    Licensed under the Apache License, Version 2.0 (the "License"); you may
//    not use this file except in compliance with the License. You may obtain
//    a copy of the License at
//
//         http://www.apache.org/licenses/LICENSE-2.0
//
//    Unless required by applicable law or agreed to in writing, software
//    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
//    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
//    License for the specific language governing permissions and limitations
//    under the License.

package config

import (
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"log"
	"net"
	"net/url"
	"os"
	"path/filepath"
	"time"

	"github.com/BurntSushi/toml"
	zxcvbn "github.com/nbutton23/zxcvbn-go"
	"github.com/pkg/errors"
)

type DBBackendType string
type ProviderType string
type OSType string
type OSArch string

const (
	// MySQLBackend represents the MySQL DB backend
	MySQLBackend DBBackendType = "mysql"
	// SQLiteBackend represents the SQLite3 DB backend
	SQLiteBackend DBBackendType = "sqlite3"
	// DefaultJWTTTL is the default duration in seconds a JWT token
	// will be valid.
	DefaultJWTTTL time.Duration = 24 * time.Hour

	// LXDProvider represents the LXD provider.
	LXDProvider ProviderType = "lxd"
	// ExternalProvider represents an external provider.
	ExternalProvider ProviderType = "external"

	// DefaultConfigFilePath is the default path on disk to the garm
	// configuration file.
	DefaultConfigFilePath = "/etc/garm/config.toml"

	// DefaultUser is the default username that should exist on the instances.
	DefaultUser = "runner"
	// DefaultUserShell is the shell for the default user.
	DefaultUserShell = "/bin/bash"

	// DefaultPoolQueueSize is the default size for a pool queue.
	DefaultPoolQueueSize = 10

	// DefaultRunnerBootstrapTimeout is the default timeout in minutes a runner is
	// considered to be defunct. If a runner does not join github in the alloted amount
	// of time and no new updates have been made to it's state, it will be removed.
	DefaultRunnerBootstrapTimeout = 20

	// DefaultGithubURL is the default URL where Github or Github Enterprise can be accessed.
	DefaultGithubURL = "https://github.com"

	// defaultBaseURL is the default URL for the github API.
	defaultBaseURL = "https://api.github.com/"
	// uploadBaseURL is the default URL for guthub uploads.
	uploadBaseURL = "https://uploads.github.com/"
)

var (
	// DefaultConfigDir is the default path on disk to the config dir. The config
	// file will probably be in the same folder, but it is not mandatory.
	DefaultConfigDir = "/etc/garm"

	// DefaultUserGroups are the groups the default user will be part of.
	DefaultUserGroups = []string{
		"sudo", "adm", "cdrom", "dialout",
		"dip", "video", "plugdev", "netdev",
		"docker", "lxd",
	}
)

const (
	Windows OSType = "windows"
	Linux   OSType = "linux"
	Unknown OSType = "unknown"
)

const (
	Amd64 OSArch = "amd64"
	I386  OSArch = "i386"
	Arm64 OSArch = "arm64"
	Arm   OSArch = "arm"
)

// NewConfig returns a new Config
func NewConfig(cfgFile string) (*Config, error) {
	var config Config
	if _, err := toml.DecodeFile(cfgFile, &config); err != nil {
		return nil, errors.Wrap(err, "decoding toml")
	}
	if config.Default.ConfigDir == "" {
		config.Default.ConfigDir = DefaultConfigDir
	}
	if err := config.Validate(); err != nil {
		return nil, errors.Wrap(err, "validating config")
	}
	return &config, nil
}

type Config struct {
	Default   Default    `toml:"default" json:"default"`
	APIServer APIServer  `toml:"apiserver,omitempty" json:"apiserver,omitempty"`
	Metrics   Metrics    `toml:"metrics,omitempty" json:"metrics,omitempty"`
	Database  Database   `toml:"database,omitempty" json:"database,omitempty"`
	Providers []Provider `toml:"provider,omitempty" json:"provider,omitempty"`
	Github    []Github   `toml:"github,omitempty"`
	JWTAuth   JWTAuth    `toml:"jwt_auth" json:"jwt-auth"`
}

// Validate validates the config
func (c *Config) Validate() error {
	if err := c.APIServer.Validate(); err != nil {
		return errors.Wrap(err, "validating APIServer config")
	}
	if err := c.Database.Validate(); err != nil {
		return errors.Wrap(err, "validating database config")
	}

	if err := c.Default.Validate(); err != nil {
		return errors.Wrap(err, "validating default section")
	}

	for _, gh := range c.Github {
		if err := gh.Validate(); err != nil {
			return errors.Wrap(err, "validating github config")
		}
	}

	if err := c.JWTAuth.Validate(); err != nil {
		return errors.Wrap(err, "validating jwt config")
	}

	providerNames := map[string]int{}

	for _, provider := range c.Providers {
		if err := provider.Validate(); err != nil {
			return errors.Wrap(err, "validating provider")
		}
		providerNames[provider.Name] += 1
	}

	for name, count := range providerNames {
		if count > 1 {
			return fmt.Errorf("duplicate provider name %s", name)
		}
	}

	return nil
}

type Default struct {
	// ConfigDir is the folder where the runner may save any aditional files
	// or configurations it may need. Things like auto-generated SSH keys that
	// may be used to access the runner instances.
	ConfigDir string `toml:"config_dir,omitempty" json:"config-dir,omitempty"`
	// CallbackURL is the URL where the instances can send back status reports.
	CallbackURL string `toml:"callback_url" json:"callback-url"`
	// MetadataURL is the URL where instances can fetch information they may need
	// to set themselves up.
	MetadataURL string `toml:"metadata_url" json:"metadata-url"`
	// LogFile is the location of the log file.
	LogFile           string `toml:"log_file,omitempty" json:"log-file"`
	EnableLogStreamer bool   `toml:"enable_log_streamer"`
}

func (d *Default) Validate() error {
	if d.CallbackURL == "" {
		return fmt.Errorf("missing callback_url")
	}
	_, err := url.Parse(d.CallbackURL)
	if err != nil {
		return errors.Wrap(err, "validating callback_url")
	}

	if d.MetadataURL == "" {
		return fmt.Errorf("missing metadata-url")
	}
	if _, err := url.Parse(d.MetadataURL); err != nil {
		return errors.Wrap(err, "validating metadata_url")
	}

	if d.ConfigDir == "" {
		return fmt.Errorf("config_dir cannot be empty")
	}

	if _, err := os.Stat(d.ConfigDir); err != nil {
		return errors.Wrap(err, "accessing config dir")
	}

	return nil
}

// Github hold configuration options specific to interacting with github.
// Currently that is just a OAuth2 personal token.
type Github struct {
	Name          string `toml:"name" json:"name"`
	Description   string `toml:"description" json:"description"`
	OAuth2Token   string `toml:"oauth2_token" json:"oauth2-token"`
	APIBaseURL    string `toml:"api_base_url" json:"api-base-url"`
	UploadBaseURL string `toml:"upload_base_url" json:"upload-base-url"`
	BaseURL       string `toml:"base_url" json:"base-url"`
	// CACertBundlePath is the path on disk to a CA certificate bundle that
	// can validate the endpoints defined above. Leave empty if not using a
	// self signed certificate.
	CACertBundlePath string `toml:"ca_cert_bundle" json:"ca-cert-bundle"`
}

func (g *Github) APIEndpoint() string {
	if g.APIBaseURL != "" {
		return g.APIBaseURL
	}
	return defaultBaseURL
}

func (g *Github) CACertBundle() ([]byte, error) {
	if g.CACertBundlePath == "" {
		// No CA bundle defined.
		return nil, nil
	}
	if _, err := os.Stat(g.CACertBundlePath); err != nil {
		return nil, errors.Wrap(err, "accessing CA bundle")
	}

	contents, err := os.ReadFile(g.CACertBundlePath)
	if err != nil {
		return nil, errors.Wrap(err, "reading CA bundle")
	}

	roots := x509.NewCertPool()
	if ok := roots.AppendCertsFromPEM(contents); !ok {
		return nil, fmt.Errorf("failed to parse CA cert bundle")
	}

	return contents, nil
}

func (g *Github) UploadEndpoint() string {
	if g.UploadBaseURL == "" {
		if g.APIBaseURL != "" {
			return g.APIBaseURL
		}
		return uploadBaseURL
	}
	return g.UploadBaseURL
}

func (g *Github) BaseEndpoint() string {
	if g.BaseURL != "" {
		return g.BaseURL
	}
	return DefaultGithubURL
}

func (g *Github) Validate() error {
	if g.OAuth2Token == "" {
		return fmt.Errorf("missing github oauth2 token")
	}

	return nil
}

// Provider holds access information for a particular provider.
// A provider offers compute resources on which we spin up self hosted runners.
type Provider struct {
	Name         string       `toml:"name" json:"name"`
	ProviderType ProviderType `toml:"provider_type" json:"provider-type"`
	Description  string       `toml:"description" json:"description"`
	LXD          LXD          `toml:"lxd" json:"lxd"`
	External     External     `toml:"external" json:"external"`
}

func (p *Provider) Validate() error {
	if p.Name == "" {
		return fmt.Errorf("missing provider name")
	}

	switch p.ProviderType {
	case LXDProvider:
		if err := p.LXD.Validate(); err != nil {
			return errors.Wrap(err, "validating LXD provider info")
		}
	case ExternalProvider:
		if err := p.External.Validate(); err != nil {
			return errors.Wrap(err, "validating external provider info")
		}
	default:
		return fmt.Errorf("unknown provider type: %s", p.ProviderType)
	}
	return nil
}

// Database is the database config entry
type Database struct {
	Debug     bool          `toml:"debug" json:"debug"`
	DbBackend DBBackendType `toml:"backend" json:"backend"`
	MySQL     MySQL         `toml:"mysql" json:"mysql"`
	SQLite    SQLite        `toml:"sqlite3" json:"sqlite3"`
	// Passphrase is used to encrypt any sensitive info before
	// inserting it into the database. This is just temporary until
	// we move to something like vault or barbican for secrets storage.
	// Don't lose or change this. It will invalidate all encrypted data
	// in the DB. This field must be set and must be exactly 32 characters.
	Passphrase string `toml:"passphrase"`
}

// GormParams returns the database type and connection URI
func (d *Database) GormParams() (dbType DBBackendType, uri string, err error) {
	if err := d.Validate(); err != nil {
		return "", "", errors.Wrap(err, "validating database config")
	}
	dbType = d.DbBackend
	switch dbType {
	case MySQLBackend:
		uri, err = d.MySQL.ConnectionString()
		if err != nil {
			return "", "", errors.Wrap(err, "fetching mysql connection string")
		}
	case SQLiteBackend:
		uri, err = d.SQLite.ConnectionString()
		if err != nil {
			return "", "", errors.Wrap(err, "fetching sqlite3 connection string")
		}
	default:
		return "", "", fmt.Errorf("invalid database backend: %s", dbType)
	}
	return
}

// Validate validates the database config entry
func (d *Database) Validate() error {
	if d.DbBackend == "" {
		return fmt.Errorf("invalid databse configuration: backend is required")
	}

	if len(d.Passphrase) != 32 {
		return fmt.Errorf("passphrase must be set and it must be a string of 32 characters (aes 256)")
	}

	passwordStenght := zxcvbn.PasswordStrength(d.Passphrase, nil)
	if passwordStenght.Score < 4 {
		return fmt.Errorf("database passphrase is too weak")
	}

	switch d.DbBackend {
	case MySQLBackend:
		if err := d.MySQL.Validate(); err != nil {
			return errors.Wrap(err, "validating mysql config")
		}
	case SQLiteBackend:
		if err := d.SQLite.Validate(); err != nil {
			return errors.Wrap(err, "validating sqlite3 config")
		}
	default:
		return fmt.Errorf("invalid database backend: %s", d.DbBackend)
	}
	return nil
}

// SQLite is the config entry for the sqlite3 section
type SQLite struct {
	DBFile string `toml:"db_file" json:"db-file"`
}

func (s *SQLite) Validate() error {
	if s.DBFile == "" {
		return fmt.Errorf("no valid db_file was specified")
	}

	if !filepath.IsAbs(s.DBFile) {
		return fmt.Errorf("please specify an absolute path for db_file")
	}

	parent := filepath.Dir(s.DBFile)
	if _, err := os.Stat(parent); err != nil {
		return errors.Wrapf(err, "accessing db_file parent dir: %s", parent)
	}
	return nil
}

func (s *SQLite) ConnectionString() (string, error) {
	return s.DBFile, nil
}

// MySQL is the config entry for the mysql section
type MySQL struct {
	Username     string `toml:"username" json:"username"`
	Password     string `toml:"password" json:"password"`
	Hostname     string `toml:"hostname" json:"hostname"`
	DatabaseName string `toml:"database" json:"database"`
}

// Validate validates a Database config entry
func (m *MySQL) Validate() error {
	if m.Username == "" || m.Password == "" || m.Hostname == "" || m.DatabaseName == "" {
		return fmt.Errorf(
			"database, username, password, hostname are mandatory parameters for the database section")
	}
	return nil
}

// ConnectionString returns a gorm compatible connection string
func (m *MySQL) ConnectionString() (string, error) {
	if err := m.Validate(); err != nil {
		return "", err
	}

	connString := fmt.Sprintf(
		"%s:%s@tcp(%s)/%s?charset=utf8&parseTime=True&loc=Local&timeout=5s",
		m.Username, m.Password,
		m.Hostname, m.DatabaseName,
	)
	return connString, nil
}

// TLSConfig is the API server TLS config
type TLSConfig struct {
	CRT string `toml:"certificate" json:"certificate"`
	Key string `toml:"key" json:"key"`
}

// Validate validates the TLS config
func (t *TLSConfig) Validate() error {
	if t.CRT == "" || t.Key == "" {
		return fmt.Errorf("missing crt or key")
	}

	_, err := tls.LoadX509KeyPair(t.CRT, t.Key)
	if err != nil {
		return err
	}
	return nil
}

type Metrics struct {
	DisableAuth bool `toml:"disable_auth" json:"disable-auth"`
	Enable      bool `toml:"enable" json:"enable"`
}

// APIServer holds configuration for the API server
// worker
type APIServer struct {
	Bind        string    `toml:"bind" json:"bind"`
	Port        int       `toml:"port" json:"port"`
	UseTLS      bool      `toml:"use_tls" json:"use-tls"`
	TLSConfig   TLSConfig `toml:"tls" json:"tls"`
	CORSOrigins []string  `toml:"cors_origins" json:"cors-origins"`
}

// BindAddress returns a host:port string.
func (a *APIServer) BindAddress() string {
	return fmt.Sprintf("%s:%d", a.Bind, a.Port)
}

// Validate validates the API server config
func (a *APIServer) Validate() error {
	if a.UseTLS {
		if err := a.TLSConfig.Validate(); err != nil {
			return errors.Wrap(err, "TLS validation failed")
		}
	}
	if a.Port > 65535 || a.Port < 1 {
		return fmt.Errorf("invalid port nr %d", a.Port)
	}

	ip := net.ParseIP(a.Bind)
	if ip == nil {
		// No need for deeper validation here, as any invalid
		// IP address specified in this setting will raise an error
		// when we try to bind to it.
		return fmt.Errorf("invalid IP address")
	}
	return nil
}

type timeToLive string

func (d *timeToLive) ParseDuration() (time.Duration, error) {
	duration, err := time.ParseDuration(string(*d))
	if err != nil {
		return 0, err
	}
	return duration, nil
}

func (d *timeToLive) Duration() time.Duration {
	duration, err := d.ParseDuration()
	if err != nil {
		log.Printf("failed to parse duration: %s", err)
		return DefaultJWTTTL
	}
	// TODO(gabriel-samfira): should we have a minimum TTL?
	if duration < DefaultJWTTTL {
		return DefaultJWTTTL
	}

	return duration
}

func (d *timeToLive) UnmarshalText(text []byte) error {
	_, err := time.ParseDuration(string(text))
	if err != nil {
		return errors.Wrap(err, "parsing time_to_live")
	}

	*d = timeToLive(text)
	return nil
}

// JWTAuth holds settings used to generate JWT tokens
type JWTAuth struct {
	Secret     string     `toml:"secret" json:"secret"`
	TimeToLive timeToLive `toml:"time_to_live" json:"time-to-live"`
}

// Validate validates the JWTAuth config
func (j *JWTAuth) Validate() error {
	if _, err := j.TimeToLive.ParseDuration(); err != nil {
		return errors.Wrap(err, "parsing duration")
	}

	if j.Secret == "" {
		return fmt.Errorf("invalid JWT secret")
	}
	passwordStenght := zxcvbn.PasswordStrength(j.Secret, nil)
	if passwordStenght.Score < 4 {
		return fmt.Errorf("jwt_secret is too weak")
	}
	return nil
}