// Sshwifty - A Web SSH client
//
// Copyright (C) 2019 Rui NI <nirui@gmx.com>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

package configuration

import (
	"encoding/json"
	"fmt"
	"os"
	"os/user"
	"path"
	"path/filepath"
	"strings"
	"time"

	"github.com/niruix/sshwifty/application/network"

	"github.com/niruix/sshwifty/application/log"
)

const (
	fileTypeName = "File"
)

type fileCfgServer struct {
	ListenInterface       string // Interface to listen to
	ListenPort            uint16 // Port to listen
	InitialTimeout        int    // Client initial request timeout, in second
	ReadTimeout           int    // Read operation timeout, in second
	WriteTimeout          int    // Write operation timeout, in second
	HeartbeatTimeout      int    // Client heartbeat interval, in second
	ReadDelay             int    // Read delay, in millisecond
	WriteDelay            int    // Write delay, in millisecond
	TLSCertificateFile    string // Location of TLS certificate file
	TLSCertificateKeyFile string // Location of TLS certificate key
}

func (f fileCfgServer) minDur(current, min int) int {
	if current > min {
		return current
	}

	return min
}

func (f *fileCfgServer) build() Server {
	return Server{
		ListenInterface: f.ListenInterface,
		ListenPort:      f.ListenPort,
		InitialTimeout: time.Duration(
			f.minDur(f.InitialTimeout, 5)) * time.Second,
		ReadTimeout: time.Duration(
			f.minDur(f.ReadTimeout, 30)) * time.Second,
		WriteTimeout: time.Duration(
			f.minDur(f.WriteTimeout, 30)) * time.Second,
		HeartbeatTimeout: time.Duration(
			f.minDur(f.HeartbeatTimeout, 10)) * time.Second,
		ReadDelay: time.Duration(
			f.minDur(f.ReadDelay, 0)) * time.Millisecond,
		WriteDelay: time.Duration(
			f.minDur(f.WriteDelay, 0)) * time.Millisecond,
		TLSCertificateFile:    f.TLSCertificateFile,
		TLSCertificateKeyFile: f.TLSCertificateKeyFile,
	}
}

type fileCfgCommon struct {
	HostName       string           // Host name
	SharedKey      string           // Shared key, empty to enable public access
	Socks5         string           // Socks5 server address, optional
	Socks5User     string           // Login user for socks5 server, optional
	Socks5Password string           // Login pass for socks5 server, optional
	Servers        []*fileCfgServer // Servers
}

func loadFile(filePath string) (string, Configuration, error) {
	f, fErr := os.Open(filePath)

	if fErr != nil {
		return fileTypeName, Configuration{}, fErr
	}

	defer f.Close()

	cfg := fileCfgCommon{}

	jDecoder := json.NewDecoder(f)
	jDecodeErr := jDecoder.Decode(&cfg)

	if jDecodeErr != nil {
		return fileTypeName, Configuration{}, jDecodeErr
	}

	servers := make([]Server, len(cfg.Servers))

	for i := range servers {
		servers[i] = cfg.Servers[i].build()
	}

	var dialer network.Dial

	if len(cfg.Socks5) <= 0 {
		dialer = network.TCPDial()
	} else {
		sDial, sDialErr := network.BuildSocks5Dial(
			cfg.Socks5, cfg.Socks5User, cfg.Socks5Password)

		if sDialErr != nil {
			return fileTypeName, Configuration{}, sDialErr
		}

		dialer = sDial
	}

	return fileTypeName, Configuration{
		HostName:  cfg.HostName,
		SharedKey: cfg.SharedKey,
		Dialer:    dialer,
		Servers:   servers,
	}, nil
}

// File creates a configuration file loader
func File(customPath string) Loader {
	return func(log log.Logger) (string, Configuration, error) {
		if len(customPath) > 0 {
			log.Info("Loading configuration from: %s", customPath)

			return loadFile(customPath)
		}

		log.Info("Loading configuration from one of the default " +
			"configuration files ...")

		fallbackFileSearchList := make([]string, 0, 3)

		// ~/.config/sshwifty.conf.json
		u, userErr := user.Current()
		if userErr == nil {
			fallbackFileSearchList = append(
				fallbackFileSearchList,
				path.Join(u.HomeDir, ".config", "sshwifty.conf.json"))
		}

		// /etc/sshwifty.conf.json
		fallbackFileSearchList = append(
			fallbackFileSearchList, "/etc/sshwifty.conf.json")

		// sshwifty.conf.json located at the same directory as Sshwifty bin
		ex, exErr := os.Executable()
		if exErr == nil {
			fallbackFileSearchList = append(
				fallbackFileSearchList,
				path.Join(filepath.Dir(ex), "sshwifty.conf.json"))
		}

		for f := range fallbackFileSearchList {
			fInfo, fErr := os.Stat(fallbackFileSearchList[f])

			if fErr != nil {
				continue
			}

			if fInfo.IsDir() {
				continue
			}

			log.Info("Configuration file \"%s\" has been selected",
				fallbackFileSearchList[f])

			return loadFile(fallbackFileSearchList[f])
		}

		return fileTypeName, Configuration{}, fmt.Errorf(
			"Configuration file was not specified. Also tried fallback files "+
				"\"%s\", but none of it was available",
			strings.Join(fallbackFileSearchList, "\", \""))
	}
}