package main

import (
	"database/sql"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"strings"
	"text/template"
	"time"

	"github.com/google/uuid"
	_ "github.com/lib/pq"
	"golang.org/x/crypto/bcrypt"
)

// Varibles, constants and basic structures

const (
	hashCost      = 16
	sessionLength = 12000 * time.Second
)

var (
	db               *sql.DB
	sessions         = make(map[string]session)
	fileUploadPath   = "./uploads"
	templateFilePath = "./editor_templates"
	templates        = template.Must(template.ParseGlob("templates/*.html"))
)

type session struct {
	username    string
	expiry      time.Time
	sessionUUID string
}

type Credentials struct {
	Password string `json:"password"`
	Username string `json:"username"`
}

type File struct {
	ID           int
	UserID       uuid.UUID
	Filename     string
	CreationTime int64
	LastEdited   int64
	LastOpened   int64
}

func main() {
	// Retrieve Environment variables
	dbName := "notatio"
	dbHost := getEnvVariable("DB_HOST")
	dbPort := getEnvVariable("PGPORT")
	dbUser := getEnvVariable("DB_USER")
	dbPassword := getEnvVariable("POSTGRES_PASSWORD")
	dbSSLMode := getEnvVariable("DB_SSL_MODE")

	db = connectToDatabase(dbHost, dbPort, dbUser, dbPassword, dbUser, dbSSLMode)
	defer db.Close()

	missingParam := ""
	switch {
	case dbHost == "":
		missingParam = "DB_HOST"
	case dbPort == "":
		missingParam = "PGPORT"
	case dbUser == "":
		missingParam = "DB_USER"
	case dbPassword == "":
		missingParam = "POSTGRES_PASSWORD"
	}

	if missingParam != "" {
		log.Printf("Error: Required PostgreSQL connection environment variable '%s' is not provided.\n", missingParam)
		log.Println("Exiting...")
		os.Exit(10)
	}

	exists := checkDatabaseExists(db, dbName)

	if !exists {
		createDatabase(db, dbName)
	}

	db = connectToNotatioDatabase(dbHost, dbPort, dbUser, dbPassword, dbName, dbSSLMode)
	defer db.Close()

	adminUsername := getEnvVariable("ADMIN_USER")
	adminPassword := getEnvVariable("ADMIN_PASS")
	adminName := getEnvVariable("ADMIN_NAME")
	adminEmail := getEnvVariable("ADMIN_EMAIL")

	createUserTable()
	createFilesTable()

	createUser(adminUsername, adminPassword, adminName, adminEmail)
	log.Println("Done with database checks, starting webserver!")

	// Start webserver
	initHTTPServer()

}

// Web server initializer
func initHTTPServer() {
	http.HandleFunc("/", AboutPage)
	http.HandleFunc("/signup", Signup)
	http.HandleFunc("/login", Login)
	http.HandleFunc("/home", ListFiles)
	http.HandleFunc("/refresh", Refresh)
	http.HandleFunc("/logout", Logout)
	http.HandleFunc("/upload", UploadFile)
	http.HandleFunc("/edit", EditFile)
	http.HandleFunc("/save", SaveFile)
	http.HandleFunc("/create", createNewFile)
	http.HandleFunc("/welcome", newUser)
	http.HandleFunc("/delete", DeleteFiles)
	http.HandleFunc("/export", exportFiles)
	http.HandleFunc("/checkusername", handleUsernameCheck)

	http.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.Dir("static"))))

	// Start the server on port 9991
	fmt.Println("Starting HTTP server on port 9991...")
	log.Fatal(http.ListenAndServe(":9991", nil))
}

func renderTemplate(w http.ResponseWriter, templateName string, data interface{}) {
	err := templates.ExecuteTemplate(w, templateName, data)
	if err != nil {
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		log.Printf("Error rendering template %s: %v", templateName, err)
	}
}

func handleUsernameCheck(w http.ResponseWriter, r *http.Request) {
	// Get the username from the query parameter
	username := r.URL.Query().Get("username")
	// Check if the username is taken (example function)
	isTaken, err := isUsernameTaken(username)
	if err != nil {
		log.Fatal(err)
	}

	// Create a response map to store the availability status
	response := map[string]bool{
		"available": isTaken,
	}

	// Convert the response to JSON format
	jsonResponse, err := json.Marshal(response)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// Set the content type as JSON
	w.Header().Set("Content-Type", "application/json")

	// Write the JSON response to the response writer
	w.Write(jsonResponse)
}

func handleInternalServerError(w http.ResponseWriter, err error) {
	log.Printf("Error: %v", err)
}

func AboutPage(w http.ResponseWriter, r *http.Request) {
	renderTemplate(w, "index.html", nil)
}

func newUser(w http.ResponseWriter, r *http.Request) {
	renderTemplate(w, "newuser.html", nil)
}

func Refresh(w http.ResponseWriter, r *http.Request) {
	userSession, err := validateSession(w, r)
	if err != nil {
		// Handle the error as needed
		return
	}

	// Create a new session token for the current user
	newSessionToken := uuid.NewString()
	expiresAt := time.Now().Add(sessionLength)

	// Store the token in the session map, along with the user whom it represents
	sessions[newSessionToken] = session{
		username: userSession.username,
		expiry:   expiresAt,
	}

	// Delete the older session token
	delete(sessions, userSession.sessionUUID)

	// Set the new token as the user's `session_token` cookie
	http.SetCookie(w, &http.Cookie{
		Name:    "session_token",
		Value:   newSessionToken,
		Expires: expiresAt,
	})

	log.Printf("Session refreshed for user: %s", userSession.username)

	// Redirect to the home page
	http.Redirect(w, r, "/home", http.StatusSeeOther)
}

func (s session) isSessionExpired() bool {
	return s.expiry.Before(time.Now())
}

func validateSession(w http.ResponseWriter, r *http.Request) (session, error) {
	sessionCookie, err := r.Cookie("session_token")
	if err != nil {
		log.Printf("Error getting session cookie: %v", err)
		http.Redirect(w, r, "/?login", http.StatusSeeOther) // Redirect to the login page
		return session{}, err
	}

	sessionToken := sessionCookie.Value
	userSession, exists := sessions[sessionToken]
	if !exists {
		log.Printf("Session not found for token: %s", sessionToken)
		http.Redirect(w, r, "/?login", http.StatusSeeOther) // Redirect to the login page
		return session{}, fmt.Errorf("session not found")
	}

	if userSession.isSessionExpired() {
		delete(sessions, sessionToken)
		log.Printf("Session expired for user: %s", userSession.username)
		http.Redirect(w, r, "/?login", http.StatusSeeOther) // Redirect to the login page
		return session{}, fmt.Errorf("session expired")
	}

	return userSession, nil
}

func createUserTable() {
	// Create User Table
	createUserTable := `
	 CREATE TABLE IF NOT EXISTS users (
		 id SERIAL PRIMARY KEY,
		 username VARCHAR(255) UNIQUE NOT NULL,
		 password VARCHAR(255) NOT NULL,
		 accounttype VARCHAR(255) NOT NULL,
		 uuid VARCHAR(255) NOT NULL,
		 name VARCHAR(255) NOT NULL,
		 email VARCHAR(255) NOT NULL
	 );`

	_, err := db.Exec(createUserTable)
	if err != nil {
		log.Fatal(err)
	}

}

func createFilesTable() {
	// Create File Table
	createFileTable := `
	 CREATE TABLE IF NOT EXISTS files (
	     id SERIAL PRIMARY KEY,
	     user_id UUID NOT NULL,
	     filename VARCHAR(255) NOT NULL,
	     creation_time TIMESTAMP NOT NULL,
	     last_edited TIMESTAMP NOT NULL,
	     last_opened TIMESTAMP NOT NULL
	 );`

	_, err := db.Exec(createFileTable)
	if err != nil {
		log.Fatal(err)
	}
}

func getEnvVariable(name string) string {
	value := os.Getenv(name)
	if value == "" {
		log.Printf("Error: Required environment variable '%s' is not provided.\n", name)
		log.Println("Exiting...")
		os.Exit(10)
	}
	return value
}

func connectToDatabase(dbHost, dbPort, dbUser, dbPassword, dbName, dbSSLMode string) *sql.DB {
	dbConnectionString := fmt.Sprintf("host=%s port=%s user=%s password=%s dbname=%s sslmode=%s", dbHost, dbPort, dbUser, dbPassword, dbName, dbSSLMode)
	db, err := sql.Open("postgres", dbConnectionString)
	if err != nil {
		// Handle the error appropriately
		panic(err)
	}
	return db
}

func checkDatabaseExists(db *sql.DB, dbName string) bool {
	var exists bool
	row := db.QueryRow("SELECT EXISTS (SELECT 1 FROM pg_database WHERE datname = $1)", dbName)
	if err := row.Scan(&exists); err != nil {
		log.Fatal(err)
	}
	return exists
}

func createDatabase(db *sql.DB, dbName string) {
	log.Println("Notatio database does not exist. Creating Database...")
	_, err := db.Exec("CREATE DATABASE notatio")
	if err != nil {
		log.Fatal(err)
	}
}

func connectToNotatioDatabase(dbHost, dbPort, dbUser, dbPassword, dbName, dbSSLMode string) *sql.DB {
	dbConnectionString := fmt.Sprintf("host=%s port=%s user=%s password=%s dbname=%s sslmode=%s", dbHost, dbPort, dbUser, dbPassword, dbName, dbSSLMode)
	db, err := sql.Open("postgres", dbConnectionString)
	if err != nil {
		// Handle the error appropriately
		panic(err)
	}
	return db
}

func createUser(adminUsername string, adminPassword string, adminName string, adminEmail string) {
	adminUsername = strings.ToLower(adminUsername)
	if adminUsername != "" && adminPassword != "" && adminName != "" && adminEmail != "" {
		// Check if the admin user already exists in the database
		_, adminExists := getUserFromDatabase(adminUsername)
		if !adminExists {
			// Admin user doesn't exist, create it
			hashedPassword, err := bcrypt.GenerateFromPassword([]byte(adminPassword), hashCost)
			if err != nil {
				log.Printf("Error hashing admin password: %v", err)
				// Handle the error appropriately
			} else {
				// Generate a UUID for the admin user
				adminUUID := uuid.New()
				createUserFolder(adminUsername)
				// Insert the admin user into the database with the hashed password and UUID
				if err := insertUserIntoDatabase(adminUsername, string(hashedPassword), "admin", adminUUID.String(), adminName, adminEmail); err != nil {
					log.Printf("Error inserting admin user into database: %v", err)
					// Handle the error appropriately
				} else {
					log.Printf("Admin user created and added to the database: %s", adminUsername)
				}
			}
		} else {
			log.Printf("Admin user already exists in the database: %s", adminUsername)
		}
	}
}