/*
Copyright (c) 2019 Ben Morrison (gbmor)

This file is part of Getwtxt.

Getwtxt is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Getwtxt 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with Getwtxt.  If not, see <https://www.gnu.org/licenses/>.
*/

package svc // import "git.sr.ht/~gbmor/getwtxt/svc"

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/spf13/viper"
)

var reqLog *log.Logger

// Configuration values are held in an instance of
// this struct.
type Configuration struct {
	Mu            sync.RWMutex
	Port          int           `yaml:"ListenPort"`
	MsgLog        string        `yaml:"MessageLog"`
	ReqLog        string        `yaml:"RequestLog"`
	DBType        string        `yaml:"DatabaseType"`
	DBPath        string        `yaml:"DatabasePath"`
	AssetsDir     string        `yaml:"AssetsDirectory"`
	StaticDir     string        `yaml:"StaticFilesDirectory"`
	AdminPassHash string        `yaml:"-"`
	StdoutLogging bool          `yaml:"StdoutLogging"`
	CacheInterval time.Duration `yaml:"StatusFetchInterval"`
	DBInterval    time.Duration `yaml:"DatabasePushInterval"`
	Instance      `yaml:"Instance"`
}

// Instance refers to meta data about
// this specific instance of getwtxt
type Instance struct {
	Vers  string `yaml:"-"`
	Name  string `yaml:"Instance.SiteName"`
	URL   string `yaml:"Instance.URL"`
	Owner string `yaml:"Instance.OwnerName"`
	Mail  string `yaml:"Instance.Email"`
	Desc  string `yaml:"Instance.Description"`
}

// Called on start-up. Initializes everything
// related to configuration values.
func initConfig() {
	log.Printf("Loading configuration ...\n")

	parseConfigFlag()
	setConfigDefaults()

	if err := viper.ReadInConfig(); err != nil {
		log.Printf("%v\n", err.Error())
		log.Printf("Using defaults ...\n")
		bindConfig()
		return
	}

	viper.WatchConfig()
	viper.OnConfigChange(reInit)
	bindConfig()
}

// Registers either stdout or a specified file
// to the default logger, and the same for the
// request logger.
func initLogging() {
	confObj.Mu.RLock()
	defer confObj.Mu.RUnlock()

	if confObj.StdoutLogging {
		log.SetOutput(os.Stdout)
		reqLog = log.New(os.Stdout, "", log.LstdFlags)

	} else {
		msgLog, err := os.OpenFile(confObj.MsgLog, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0600)
		errLog("Could not open log file: ", err)
		reqLogFile, err := os.OpenFile(confObj.ReqLog, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0600)
		errLog("Could not open log file: ", err)

		// Listen for the signal to close the log file
		// in a separate thread. Passing it as an argument
		// to prevent race conditions when the config is
		// reloaded.
		go func(msg *os.File, req *os.File) {
			<-closeLog
			log.Printf("Closing log files ...\n\n")
			errLog("Could not close log file: ", msg.Close())
			errLog("Could not close log file: ", req.Close())
		}(msgLog, reqLogFile)

		log.SetOutput(msgLog)
		reqLog = log.New(reqLogFile, "", log.LstdFlags)
	}
}

// Default values should a config file
// not be available.
func setConfigDefaults() {
	viper.SetDefault("ListenPort", 9001)
	viper.SetDefault("MessageLog", "logs/message.log")
	viper.SetDefault("RequestLog", "logs/request.log")
	viper.SetDefault("DatabasePath", "getwtxt.db")
	viper.SetDefault("AssetsDirectory", "assets")
	viper.SetDefault("StaticFilesDirectory", "static")
	viper.SetDefault("DatabaseType", "leveldb")
	viper.SetDefault("StdoutLogging", false)
	viper.SetDefault("ReCacheInterval", "1h")
	viper.SetDefault("DatabasePushInterval", "5m")
	viper.SetDefault("AdminPassword", "please_change_me")

	viper.SetDefault("Instance.SiteName", "getwtxt")
	viper.SetDefault("Instance.OwnerName", "Anonymous Microblogger")
	viper.SetDefault("Instance.Email", "nobody@knows")
	viper.SetDefault("Instance.URL", "https://twtxt.example.com")
	viper.SetDefault("Instance.Description", "A fast, resilient twtxt registry server written in Go!")
}

// Reads data from the configuration
// flag and acts accordingly.
func parseConfigFlag() {
	if *flagConfFile == "" {
		viper.SetConfigName("getwtxt")
		viper.SetConfigType("yml")
		viper.AddConfigPath(".")
		viper.AddConfigPath("/usr/local/getwtxt")
		viper.AddConfigPath("/etc")
		viper.AddConfigPath("/usr/local/etc")

	} else {
		path, file := filepath.Split(*flagConfFile)
		if path == "" {
			path = "."
		}
		filename := strings.Split(file, ".")
		viper.SetConfigName(filename[0])
		viper.SetConfigType(filename[1])
		viper.AddConfigPath(path)
	}
}

// Simply goes down the list of fields
// in the confObj instance of &Configuration{},
// assigning values from the config file.
func bindConfig() {
	confObj.Mu.Lock()

	confObj.Port = viper.GetInt("ListenPort")
	confObj.MsgLog = viper.GetString("MessageLog")
	confObj.ReqLog = viper.GetString("RequestLog")
	confObj.DBType = strings.ToLower(viper.GetString("DatabaseType"))
	confObj.DBPath = viper.GetString("DatabasePath")
	confObj.AssetsDir = viper.GetString("AssetsDirectory")
	confObj.StaticDir = viper.GetString("StaticFilesDirectory")
	confObj.StdoutLogging = viper.GetBool("StdoutLogging")
	confObj.CacheInterval = viper.GetDuration("StatusFetchInterval")
	confObj.DBInterval = viper.GetDuration("DatabasePushInterval")
	txtPass := viper.GetString("AdminPassword")
	if txtPass == "please_change_me" || strings.TrimSpace(txtPass) == "" {
		fmt.Println("Please set AdminPassword in getwtxt.yml")
		os.Exit(1)
	}
	passHash, err := HashPass(txtPass)
	if err != nil {
		errFatal("Failed to hash administrator password: ", err)
	}
	confObj.AdminPassHash = passHash

	confObj.Instance.Vers = Vers
	confObj.Instance.Name = viper.GetString("Instance.SiteName")
	confObj.Instance.URL = viper.GetString("Instance.URL")
	confObj.Instance.Owner = viper.GetString("Instance.OwnerName")
	confObj.Instance.Mail = viper.GetString("Instance.Email")
	confObj.Instance.Desc = viper.GetString("Instance.Description")

	if *flagDBType != "" {
		confObj.DBType = *flagDBType
	}
	if *flagDBPath != "" {
		confObj.DBPath = *flagDBPath
	}
	if *flagAssets != "" {
		confObj.AssetsDir = *flagAssets
	}

	confObj.Mu.Unlock()
	announceConfig()
}

// Echoes chosen configuration options on startup and after
// a change in getwtxt.yml is detected.
func announceConfig() {
	confObj.Mu.RLock()
	defer confObj.Mu.RUnlock()

	if confObj.StdoutLogging {
		log.Printf("Logging to: stdout\n")
	} else {
		log.Printf("Logging messages to: %v\n", confObj.MsgLog)
		log.Printf("Logging requests to: %v\n", confObj.ReqLog)
	}
	log.Printf("Using %v database: %v\n", confObj.DBType, confObj.DBPath)
	log.Printf("Database push interval: %v\n", confObj.DBInterval)
	log.Printf("User status fetch interval: %v\n", confObj.CacheInterval)
	log.Printf("Static files directory: %v", confObj.StaticDir)
}