/*
 * Copyright © 2018-2019 A Bunch Tell LLC.
 *
 * This file is part of WriteFreely.
 *
 * WriteFreely is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License, included
 * in the LICENSE file in this source code package.
 */

package writefreely

import (
	"crypto/tls"
	"database/sql"
	"fmt"
	"html/template"
	"io/ioutil"
	"net/http"
	"net/url"
	"os"
	"os/signal"
	"path/filepath"
	"regexp"
	"strings"
	"syscall"
	"time"

	"github.com/gorilla/mux"
	"github.com/gorilla/schema"
	"github.com/gorilla/sessions"
	"github.com/manifoldco/promptui"
	"github.com/writeas/go-strip-markdown"
	"github.com/writeas/impart"
	"github.com/writeas/web-core/auth"
	"github.com/writeas/web-core/converter"
	"github.com/writeas/web-core/log"
	"github.com/writeas/writefreely/author"
	"github.com/writeas/writefreely/config"
	"github.com/writeas/writefreely/key"
	"github.com/writeas/writefreely/migrations"
	"github.com/writeas/writefreely/page"
	"golang.org/x/crypto/acme/autocert"
)

const (
	staticDir       = "static"
	assumedTitleLen = 80
	postsPerPage    = 10

	serverSoftware = "WriteFreely"
	softwareURL    = "https://writefreely.org"
)

var (
	debugging bool

	// Software version can be set from git env using -ldflags
	softwareVer = "0.10.0"

	// DEPRECATED VARS
	isSingleUser bool
)

// App holds data and configuration for an individual WriteFreely instance.
type App struct {
	router       *mux.Router
	shttp        *http.ServeMux
	db           *datastore
	cfg          *config.Config
	cfgFile      string
	keys         *key.Keychain
	sessionStore *sessions.CookieStore
	formDecoder  *schema.Decoder

	timeline *localTimeline
}

// DB returns the App's datastore
func (app *App) DB() *datastore {
	return app.db
}

// Router returns the App's router
func (app *App) Router() *mux.Router {
	return app.router
}

// Config returns the App's current configuration.
func (app *App) Config() *config.Config {
	return app.cfg
}

// SetConfig updates the App's Config to the given value.
func (app *App) SetConfig(cfg *config.Config) {
	app.cfg = cfg
}

// SetKeys updates the App's Keychain to the given value.
func (app *App) SetKeys(k *key.Keychain) {
	app.keys = k
}

// Apper is the interface for getting data into and out of a WriteFreely
// instance (or "App").
//
// App returns the App for the current instance.
//
// LoadConfig reads an app configuration into the App, returning any error
// encountered.
//
// SaveConfig persists the current App configuration.
//
// LoadKeys reads the App's encryption keys and loads them into its
// key.Keychain.
type Apper interface {
	App() *App

	LoadConfig() error
	SaveConfig(*config.Config) error

	LoadKeys() error

	ReqLog(r *http.Request, status int, timeSince time.Duration) string
}

// App returns the App
func (app *App) App() *App {
	return app
}

// LoadConfig loads and parses a config file.
func (app *App) LoadConfig() error {
	log.Info("Loading %s configuration...", app.cfgFile)
	cfg, err := config.Load(app.cfgFile)
	if err != nil {
		log.Error("Unable to load configuration: %v", err)
		os.Exit(1)
		return err
	}
	app.cfg = cfg
	return nil
}

// SaveConfig saves the given Config to disk -- namely, to the App's cfgFile.
func (app *App) SaveConfig(c *config.Config) error {
	return config.Save(c, app.cfgFile)
}

// LoadKeys reads all needed keys from disk into the App. In order to use the
// configured `Server.KeysParentDir`, you must call initKeyPaths(App) before
// this.
func (app *App) LoadKeys() error {
	var err error
	app.keys = &key.Keychain{}

	if debugging {
		log.Info("  %s", emailKeyPath)
	}
	app.keys.EmailKey, err = ioutil.ReadFile(emailKeyPath)
	if err != nil {
		return err
	}

	if debugging {
		log.Info("  %s", cookieAuthKeyPath)
	}
	app.keys.CookieAuthKey, err = ioutil.ReadFile(cookieAuthKeyPath)
	if err != nil {
		return err
	}

	if debugging {
		log.Info("  %s", cookieKeyPath)
	}
	app.keys.CookieKey, err = ioutil.ReadFile(cookieKeyPath)
	if err != nil {
		return err
	}

	return nil
}

func (app *App) ReqLog(r *http.Request, status int, timeSince time.Duration) string {
	return fmt.Sprintf("\"%s %s\" %d %s \"%s\"", r.Method, r.RequestURI, status, timeSince, r.UserAgent())
}

// handleViewHome shows page at root path. Will be the Pad if logged in and the
// catch-all landing page otherwise.
func handleViewHome(app *App, w http.ResponseWriter, r *http.Request) error {
	if app.cfg.App.SingleUser {
		// Render blog index
		return handleViewCollection(app, w, r)
	}

	// Multi-user instance
	forceLanding := r.FormValue("landing") == "1"
	if !forceLanding {
		// Show correct page based on user auth status and configured landing path
		u := getUserSession(app, r)
		if u != nil {
			// User is logged in, so show the Pad
			return handleViewPad(app, w, r)
		}

		if land := app.cfg.App.LandingPath(); land != "/" {
			return impart.HTTPError{http.StatusFound, land}
		}
	}

	p := struct {
		page.StaticPage
		Flashes []template.HTML
		Banner  template.HTML
		Content template.HTML

		ForcedLanding bool
	}{
		StaticPage:    pageForReq(app, r),
		ForcedLanding: forceLanding,
	}

	banner, err := getLandingBanner(app)
	if err != nil {
		log.Error("unable to get landing banner: %v", err)
		return impart.HTTPError{http.StatusInternalServerError, fmt.Sprintf("Could not get banner: %v", err)}
	}
	p.Banner = template.HTML(applyMarkdown([]byte(banner.Content), ""))

	content, err := getLandingBody(app)
	if err != nil {
		log.Error("unable to get landing content: %v", err)
		return impart.HTTPError{http.StatusInternalServerError, fmt.Sprintf("Could not get content: %v", err)}
	}
	p.Content = template.HTML(applyMarkdown([]byte(content.Content), ""))

	// Get error messages
	session, err := app.sessionStore.Get(r, cookieName)
	if err != nil {
		// Ignore this
		log.Error("Unable to get session in handleViewHome; ignoring: %v", err)
	}
	flashes, _ := getSessionFlashes(app, w, r, session)
	for _, flash := range flashes {
		p.Flashes = append(p.Flashes, template.HTML(flash))
	}

	// Show landing page
	return renderPage(w, "landing.tmpl", p)
}

func handleTemplatedPage(app *App, w http.ResponseWriter, r *http.Request, t *template.Template) error {
	p := struct {
		page.StaticPage
		ContentTitle string
		Content      template.HTML
		PlainContent string
		Updated      string

		AboutStats *InstanceStats
	}{
		StaticPage: pageForReq(app, r),
	}
	if r.URL.Path == "/about" || r.URL.Path == "/privacy" {
		var c *instanceContent
		var err error

		if r.URL.Path == "/about" {
			c, err = getAboutPage(app)

			// Fetch stats
			p.AboutStats = &InstanceStats{}
			p.AboutStats.NumPosts, _ = app.db.GetTotalPosts()
			p.AboutStats.NumBlogs, _ = app.db.GetTotalCollections()
		} else {
			c, err = getPrivacyPage(app)
		}

		if err != nil {
			return err
		}
		p.ContentTitle = c.Title.String
		p.Content = template.HTML(applyMarkdown([]byte(c.Content), ""))
		p.PlainContent = shortPostDescription(stripmd.Strip(c.Content))
		if !c.Updated.IsZero() {
			p.Updated = c.Updated.Format("January 2, 2006")
		}
	}

	// Serve templated page
	err := t.ExecuteTemplate(w, "base", p)
	if err != nil {
		log.Error("Unable to render page: %v", err)
	}
	return nil
}

func pageForReq(app *App, r *http.Request) page.StaticPage {
	p := page.StaticPage{
		AppCfg:  app.cfg.App,
		Path:    r.URL.Path,
		Version: "v" + softwareVer,
	}

	// Add user information, if given
	var u *User
	accessToken := r.FormValue("t")
	if accessToken != "" {
		userID := app.db.GetUserID(accessToken)
		if userID != -1 {
			var err error
			u, err = app.db.GetUserByID(userID)
			if err == nil {
				p.Username = u.Username
			}
		}
	} else {
		u = getUserSession(app, r)
		if u != nil {
			p.Username = u.Username
		}
	}
	p.CanViewReader = !app.cfg.App.Private || u != nil

	return p
}

var fileRegex = regexp.MustCompile("/([^/]*\\.[^/]*)$")

// Initialize loads the app configuration and initializes templates, keys,
// session, route handlers, and the database connection.
func Initialize(apper Apper, debug bool) (*App, error) {
	debugging = debug

	apper.LoadConfig()

	// Load templates
	err := InitTemplates(apper.App().Config())
	if err != nil {
		return nil, fmt.Errorf("load templates: %s", err)
	}

	// Load keys and set up session
	initKeyPaths(apper.App()) // TODO: find a better way to do this, since it's unneeded in all Apper implementations
	err = InitKeys(apper)
	if err != nil {
		return nil, fmt.Errorf("init keys: %s", err)
	}
	apper.App().InitSession()

	apper.App().InitDecoder()

	err = ConnectToDatabase(apper.App())
	if err != nil {
		return nil, fmt.Errorf("connect to DB: %s", err)
	}

	// Handle local timeline, if enabled
	if apper.App().cfg.App.LocalTimeline {
		log.Info("Initializing local timeline...")
		initLocalTimeline(apper.App())
	}

	return apper.App(), nil
}

func Serve(app *App, r *mux.Router) {
	log.Info("Going to serve...")

	isSingleUser = app.cfg.App.SingleUser
	app.cfg.Server.Dev = debugging

	// Handle shutdown
	c := make(chan os.Signal, 2)
	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
	go func() {
		<-c
		log.Info("Shutting down...")
		shutdown(app)
		log.Info("Done.")
		os.Exit(0)
	}()

	// Start web application server
	var bindAddress = app.cfg.Server.Bind
	if bindAddress == "" {
		bindAddress = "localhost"
	}
	var err error
	if app.cfg.IsSecureStandalone() {
		if app.cfg.Server.Autocert {
			m := &autocert.Manager{
				Prompt: autocert.AcceptTOS,
				Cache:  autocert.DirCache(app.cfg.Server.TLSCertPath),
			}
			host, err := url.Parse(app.cfg.App.Host)
			if err != nil {
				log.Error("[WARNING] Unable to parse configured host! %s", err)
				log.Error(`[WARNING] ALL hosts are allowed, which can open you to an attack where
clients connect to a server by IP address and pretend to be asking for an
incorrect host name, and cause you to reach the CA's rate limit for certificate
requests. We recommend supplying a valid host name.`)
				log.Info("Using autocert on ANY host")
			} else {
				log.Info("Using autocert on host %s", host.Host)
				m.HostPolicy = autocert.HostWhitelist(host.Host)
			}
			s := &http.Server{
				Addr:    ":https",
				Handler: r,
				TLSConfig: &tls.Config{
					GetCertificate: m.GetCertificate,
				},
			}
			s.SetKeepAlivesEnabled(false)

			go func() {
				log.Info("Serving redirects on http://%s:80", bindAddress)
				err = http.ListenAndServe(":80", m.HTTPHandler(nil))
				log.Error("Unable to start redirect server: %v", err)
			}()

			log.Info("Serving on https://%s:443", bindAddress)
			log.Info("---")
			err = s.ListenAndServeTLS("", "")
		} else {
			go func() {
				log.Info("Serving redirects on http://%s:80", bindAddress)
				err = http.ListenAndServe(fmt.Sprintf("%s:80", bindAddress), http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
					http.Redirect(w, r, app.cfg.App.Host, http.StatusMovedPermanently)
				}))
				log.Error("Unable to start redirect server: %v", err)
			}()

			log.Info("Serving on https://%s:443", bindAddress)
			log.Info("Using manual certificates")
			log.Info("---")
			err = http.ListenAndServeTLS(fmt.Sprintf("%s:443", bindAddress), app.cfg.Server.TLSCertPath, app.cfg.Server.TLSKeyPath, r)
		}
	} else {
		log.Info("Serving on http://%s:%d\n", bindAddress, app.cfg.Server.Port)
		log.Info("---")
		err = http.ListenAndServe(fmt.Sprintf("%s:%d", bindAddress, app.cfg.Server.Port), r)
	}
	if err != nil {
		log.Error("Unable to start: %v", err)
		os.Exit(1)
	}
}

func (app *App) InitDecoder() {
	// TODO: do this at the package level, instead of the App level
	// Initialize modules
	app.formDecoder = schema.NewDecoder()
	app.formDecoder.RegisterConverter(converter.NullJSONString{}, converter.ConvertJSONNullString)
	app.formDecoder.RegisterConverter(converter.NullJSONBool{}, converter.ConvertJSONNullBool)
	app.formDecoder.RegisterConverter(sql.NullString{}, converter.ConvertSQLNullString)
	app.formDecoder.RegisterConverter(sql.NullBool{}, converter.ConvertSQLNullBool)
	app.formDecoder.RegisterConverter(sql.NullInt64{}, converter.ConvertSQLNullInt64)
	app.formDecoder.RegisterConverter(sql.NullFloat64{}, converter.ConvertSQLNullFloat64)
}

// ConnectToDatabase validates and connects to the configured database, then
// tests the connection.
func ConnectToDatabase(app *App) error {
	// Check database configuration
	if app.cfg.Database.Type == driverMySQL && (app.cfg.Database.User == "" || app.cfg.Database.Password == "") {
		return fmt.Errorf("Database user or password not set.")
	}
	if app.cfg.Database.Host == "" {
		app.cfg.Database.Host = "localhost"
	}
	if app.cfg.Database.Database == "" {
		app.cfg.Database.Database = "writefreely"
	}

	// TODO: check err
	connectToDatabase(app)

	// Test database connection
	err := app.db.Ping()
	if err != nil {
		return fmt.Errorf("Database ping failed: %s", err)
	}

	return nil
}

// FormatVersion constructs the version string for the application
func FormatVersion() string {
	return serverSoftware + " " + softwareVer
}

// OutputVersion prints out the version of the application.
func OutputVersion() {
	fmt.Println(FormatVersion())
}

// NewApp creates a new app instance.
func NewApp(cfgFile string) *App {
	return &App{
		cfgFile: cfgFile,
	}
}

// CreateConfig creates a default configuration and saves it to the app's cfgFile.
func CreateConfig(app *App) error {
	log.Info("Creating configuration...")
	c := config.New()
	log.Info("Saving configuration %s...", app.cfgFile)
	err := config.Save(c, app.cfgFile)
	if err != nil {
		return fmt.Errorf("Unable to save configuration: %v", err)
	}
	return nil
}

// DoConfig runs the interactive configuration process.
func DoConfig(app *App, configSections string) {
	if configSections == "" {
		configSections = "server db app"
	}
	// let's check there aren't any garbage in the list
	configSectionsArray := strings.Split(configSections, " ")
	for _, element := range configSectionsArray {
		if element != "server" && element != "db" && element != "app" {
			log.Error("Invalid argument to --sections. Valid arguments are only \"server\", \"db\" and \"app\"")
			os.Exit(1)
		}
	}
	d, err := config.Configure(app.cfgFile, configSections)
	if err != nil {
		log.Error("Unable to configure: %v", err)
		os.Exit(1)
	}
	app.cfg = d.Config
	connectToDatabase(app)
	defer shutdown(app)

	if !app.db.DatabaseInitialized() {
		err = adminInitDatabase(app)
		if err != nil {
			log.Error(err.Error())
			os.Exit(1)
		}
	} else {
		log.Info("Database already initialized.")
	}

	if d.User != nil {
		u := &User{
			Username:   d.User.Username,
			HashedPass: d.User.HashedPass,
			Created:    time.Now().Truncate(time.Second).UTC(),
		}

		// Create blog
		log.Info("Creating user %s...\n", u.Username)
		err = app.db.CreateUser(app.cfg, u, app.cfg.App.SiteName)
		if err != nil {
			log.Error("Unable to create user: %s", err)
			os.Exit(1)
		}
		log.Info("Done!")
	}
	os.Exit(0)
}

// GenerateKeyFiles creates app encryption keys and saves them into the configured KeysParentDir.
func GenerateKeyFiles(app *App) error {
	// Read keys path from config
	app.LoadConfig()

	// Create keys dir if it doesn't exist yet
	fullKeysDir := filepath.Join(app.cfg.Server.KeysParentDir, keysDir)
	if _, err := os.Stat(fullKeysDir); os.IsNotExist(err) {
		err = os.Mkdir(fullKeysDir, 0700)
		if err != nil {
			return err
		}
	}

	// Generate keys
	initKeyPaths(app)
	// TODO: use something like https://github.com/hashicorp/go-multierror to return errors
	var keyErrs error
	err := generateKey(emailKeyPath)
	if err != nil {
		keyErrs = err
	}
	err = generateKey(cookieAuthKeyPath)
	if err != nil {
		keyErrs = err
	}
	err = generateKey(cookieKeyPath)
	if err != nil {
		keyErrs = err
	}

	return keyErrs
}

// CreateSchema creates all database tables needed for the application.
func CreateSchema(apper Apper) error {
	apper.LoadConfig()
	connectToDatabase(apper.App())
	defer shutdown(apper.App())
	err := adminInitDatabase(apper.App())
	if err != nil {
		return err
	}
	return nil
}

// Migrate runs all necessary database migrations.
func Migrate(apper Apper) error {
	apper.LoadConfig()
	connectToDatabase(apper.App())
	defer shutdown(apper.App())

	err := migrations.Migrate(migrations.NewDatastore(apper.App().db.DB, apper.App().db.driverName))
	if err != nil {
		return fmt.Errorf("migrate: %s", err)
	}
	return nil
}

// ResetPassword runs the interactive password reset process.
func ResetPassword(apper Apper, username string) error {
	// Connect to the database
	apper.LoadConfig()
	connectToDatabase(apper.App())
	defer shutdown(apper.App())

	// Fetch user
	u, err := apper.App().db.GetUserForAuth(username)
	if err != nil {
		log.Error("Get user: %s", err)
		os.Exit(1)
	}

	// Prompt for new password
	prompt := promptui.Prompt{
		Templates: &promptui.PromptTemplates{
			Success: "{{ . | bold | faint }}: ",
		},
		Label: "New password",
		Mask:  '*',
	}
	newPass, err := prompt.Run()
	if err != nil {
		log.Error("%s", err)
		os.Exit(1)
	}

	// Do the update
	log.Info("Updating...")
	err = adminResetPassword(apper.App(), u, newPass)
	if err != nil {
		log.Error("%s", err)
		os.Exit(1)
	}
	log.Info("Success.")
	return nil
}

func connectToDatabase(app *App) {
	log.Info("Connecting to %s database...", app.cfg.Database.Type)

	var db *sql.DB
	var err error
	if app.cfg.Database.Type == driverMySQL {
		db, err = sql.Open(app.cfg.Database.Type, fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?charset=utf8mb4&parseTime=true&loc=%s", app.cfg.Database.User, app.cfg.Database.Password, app.cfg.Database.Host, app.cfg.Database.Port, app.cfg.Database.Database, url.QueryEscape(time.Local.String())))
		db.SetMaxOpenConns(50)
	} else if app.cfg.Database.Type == driverSQLite {
		if !SQLiteEnabled {
			log.Error("Invalid database type '%s'. Binary wasn't compiled with SQLite3 support.", app.cfg.Database.Type)
			os.Exit(1)
		}
		if app.cfg.Database.FileName == "" {
			log.Error("SQLite database filename value in config.ini is empty.")
			os.Exit(1)
		}
		db, err = sql.Open("sqlite3_with_regex", app.cfg.Database.FileName+"?parseTime=true&cached=shared")
		db.SetMaxOpenConns(1)
	} else {
		log.Error("Invalid database type '%s'. Only 'mysql' and 'sqlite3' are supported right now.", app.cfg.Database.Type)
		os.Exit(1)
	}
	if err != nil {
		log.Error("%s", err)
		os.Exit(1)
	}
	app.db = &datastore{db, app.cfg.Database.Type}
}

func shutdown(app *App) {
	log.Info("Closing database connection...")
	app.db.Close()
}

// CreateUser creates a new admin or normal user from the given credentials.
func CreateUser(apper Apper, username, password string, isAdmin bool) error {
	// Create an admin user with --create-admin
	apper.LoadConfig()
	connectToDatabase(apper.App())
	defer shutdown(apper.App())

	// Ensure an admin / first user doesn't already exist
	firstUser, _ := apper.App().db.GetUserByID(1)
	if isAdmin {
		// Abort if trying to create admin user, but one already exists
		if firstUser != nil {
			return fmt.Errorf("Admin user already exists (%s). Create a regular user with: writefreely --create-user", firstUser.Username)
		}
	} else {
		// Abort if trying to create regular user, but no admin exists yet
		if firstUser == nil {
			return fmt.Errorf("No admin user exists yet. Create an admin first with: writefreely --create-admin")
		}
	}

	// Create the user
	// Normalize and validate username
	desiredUsername := username
	username = getSlug(username, "")

	usernameDesc := username
	if username != desiredUsername {
		usernameDesc += " (originally: " + desiredUsername + ")"
	}

	if !author.IsValidUsername(apper.App().cfg, username) {
		return fmt.Errorf("Username %s is invalid, reserved, or shorter than configured minimum length (%d characters).", usernameDesc, apper.App().cfg.App.MinUsernameLen)
	}

	// Hash the password
	hashedPass, err := auth.HashPass([]byte(password))
	if err != nil {
		return fmt.Errorf("Unable to hash password: %v", err)
	}

	u := &User{
		Username:   username,
		HashedPass: hashedPass,
		Created:    time.Now().Truncate(time.Second).UTC(),
	}

	userType := "user"
	if isAdmin {
		userType = "admin"
	}
	log.Info("Creating %s %s...", userType, usernameDesc)
	err = apper.App().db.CreateUser(apper.App().Config(), u, desiredUsername)
	if err != nil {
		return fmt.Errorf("Unable to create user: %s", err)
	}
	log.Info("Done!")
	return nil
}

func adminInitDatabase(app *App) error {
	schemaFileName := "schema.sql"
	if app.cfg.Database.Type == driverSQLite {
		schemaFileName = "sqlite.sql"
	}

	schema, err := Asset(schemaFileName)
	if err != nil {
		return fmt.Errorf("Unable to load schema file: %v", err)
	}

	tblReg := regexp.MustCompile("CREATE TABLE (IF NOT EXISTS )?`([a-z_]+)`")

	queries := strings.Split(string(schema), ";\n")
	for _, q := range queries {
		if strings.TrimSpace(q) == "" {
			continue
		}
		parts := tblReg.FindStringSubmatch(q)
		if len(parts) >= 3 {
			log.Info("Creating table %s...", parts[2])
		} else {
			log.Info("Creating table ??? (Weird query) No match in: %v", parts)
		}
		_, err = app.db.Exec(q)
		if err != nil {
			log.Error("%s", err)
		} else {
			log.Info("Created.")
		}
	}

	// Set up migrations table
	log.Info("Initializing appmigrations table...")
	err = migrations.SetInitialMigrations(migrations.NewDatastore(app.db.DB, app.db.driverName))
	if err != nil {
		return fmt.Errorf("Unable to set initial migrations: %v", err)
	}

	log.Info("Running migrations...")
	err = migrations.Migrate(migrations.NewDatastore(app.db.DB, app.db.driverName))
	if err != nil {
		return fmt.Errorf("migrate: %s", err)
	}

	log.Info("Done.")
	return nil
}