core/auth/memberships/main.go

package main

import (
	"database/sql"
	"embed"
	"encoding/json"
	"flag"
	"fmt"
	"html/template"
	"log"
	"net/http"
	"regexp"
	"strings"

	"github.com/ncruces/go-sqlite3"
	_ "github.com/ncruces/go-sqlite3/driver"
	_ "github.com/ncruces/go-sqlite3/embed"

	"github.com/gorilla/mux"
)

var port = flag.Int("port", 8080, "Port to listen on")
var apiPort = flag.Int("api-port", 8081, "Port to listen on for API requests")
var dbPath = flag.String("db-path", "memberships.db", "Path to SQLite file")

//go:embed index.html
var indexHTML string

//go:embed group.html
var groupHTML string

//go:embed static
var staticResources embed.FS

type Store interface {
	// Initializes store with admin user and their groups.
	Init(owner string, groups []string) error
	CreateGroup(owner string, group Group) error
	AddChildGroup(parent, child string) error
	DoesGroupExist(group string) (bool, error)
	GetGroupsOwnedBy(user string) ([]Group, error)
	GetGroupsUserBelongsTo(user string) ([]Group, error)
	IsGroupOwner(user, group string) (bool, error)
	AddGroupMember(user, group string) error
	AddGroupOwner(user, group string) error
	GetGroupOwners(group string) ([]string, error)
	GetGroupMembers(group string) ([]string, error)
	GetGroupDescription(group string) (string, error)
	GetAvailableGroupsAsChild(group string) ([]string, error)
	GetAllTransitiveGroupsForUser(user string) ([]Group, error)
	GetGroupsGroupBelongsTo(group string) ([]Group, error)
	GetDirectChildrenGroups(group string) ([]Group, error)
	GetAllTransitiveGroupsForGroup(group string) ([]Group, error)
	RemoveFromGroupToGroup(parent, child string) error
	RemoveUserFromTable(username, groupName, tableName string) error
}

type Server struct {
	store Store
}

type Group struct {
	Name        string
	Description string
}

type SQLiteStore struct {
	db *sql.DB
}

func NewSQLiteStore(db *sql.DB) (*SQLiteStore, error) {
	_, err := db.Exec(`
        CREATE TABLE IF NOT EXISTS groups (
            name TEXT PRIMARY KEY,
            description TEXT
        );

        CREATE TABLE IF NOT EXISTS owners (
            username TEXT,
            group_name TEXT,
            FOREIGN KEY(group_name) REFERENCES groups(name)
        );

        CREATE TABLE IF NOT EXISTS group_to_group (
            parent_group TEXT,
            child_group TEXT,
            FOREIGN KEY(parent_group) REFERENCES groups(name),
            FOREIGN KEY(child_group) REFERENCES groups(name)
        );

        CREATE TABLE IF NOT EXISTS user_to_group (
            username TEXT,
            group_name TEXT,
            FOREIGN KEY(group_name) REFERENCES groups(name)
        );`)
	if err != nil {
		return nil, err
	}
	return &SQLiteStore{db: db}, nil
}

func (s *SQLiteStore) Init(owner string, groups []string) error {
	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	row := tx.QueryRow("SELECT COUNT(*) FROM groups")
	var count int
	if err := row.Scan(&count); err != nil {
		return err
	}
	if count != 0 {
		return fmt.Errorf("store already initialised")
	}
	for _, g := range groups {
		query := `INSERT INTO groups (name, description) VALUES (?, '')`
		if _, err := tx.Exec(query, g); err != nil {
			return err
		}
		query = `INSERT INTO owners (username, group_name) VALUES (?, ?)`
		if _, err := tx.Exec(query, owner, g); err != nil {
			return err
		}
		query = `INSERT INTO user_to_group (username, group_name) VALUES (?, ?)`
		if _, err := tx.Exec(query, owner, g); err != nil {
			return err
		}
	}
	return tx.Commit()
}

func (s *SQLiteStore) queryGroups(query string, args ...interface{}) ([]Group, error) {
	groups := make([]Group, 0)
	rows, err := s.db.Query(query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	for rows.Next() {
		var group Group
		if err := rows.Scan(&group.Name, &group.Description); err != nil {
			return nil, err
		}
		groups = append(groups, group)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return groups, nil
}

func (s *SQLiteStore) GetGroupsOwnedBy(user string) ([]Group, error) {
	query := `
        SELECT groups.name, groups.description
        FROM groups
        JOIN owners ON groups.name = owners.group_name
        WHERE owners.username = ?`
	return s.queryGroups(query, user)
}

func (s *SQLiteStore) GetGroupsUserBelongsTo(user string) ([]Group, error) {
	query := `
        SELECT groups.name, groups.description
        FROM groups
        JOIN user_to_group ON groups.name = user_to_group.group_name
        WHERE user_to_group.username = ?`
	return s.queryGroups(query, user)
}

func (s *SQLiteStore) CreateGroup(owner string, group Group) error {
	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	query := `INSERT INTO groups (name, description) VALUES (?, ?)`
	if _, err := tx.Exec(query, group.Name, group.Description); err != nil {
		sqliteErr, ok := err.(*sqlite3.Error)
		if ok && sqliteErr.ExtendedCode() == 1555 {
			return fmt.Errorf("Group with the name %s already exists", group.Name)
		}
		return err
	}
	query = `INSERT INTO owners (username, group_name) VALUES (?, ?)`
	if _, err := tx.Exec(query, owner, group.Name); err != nil {
		return err
	}
	return tx.Commit()
}

func (s *SQLiteStore) IsGroupOwner(user, group string) (bool, error) {
	query := `
        SELECT EXISTS (
            SELECT 1
            FROM owners
            WHERE username = ? AND group_name = ?
        )`
	var exists bool
	if err := s.db.QueryRow(query, user, group).Scan(&exists); err != nil {
		return false, err
	}
	return exists, nil
}

func (s *SQLiteStore) userGroupPairExists(tx *sql.Tx, table, user, group string) (bool, error) {
	query := fmt.Sprintf("SELECT EXISTS (SELECT 1 FROM %s WHERE username = ? AND group_name = ?)", table)
	var exists bool
	if err := tx.QueryRow(query, user, group).Scan(&exists); err != nil {
		return false, err
	}
	return exists, nil
}

func (s *SQLiteStore) AddGroupMember(user, group string) error {
	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	existsInUserToGroup, err := s.userGroupPairExists(tx, "user_to_group", user, group)
	if err != nil {
		return err
	}
	if existsInUserToGroup {
		return fmt.Errorf("%s is already a member of group %s", user, group)
	}
	if _, err := tx.Exec(`INSERT INTO user_to_group (username, group_name) VALUES (?, ?)`, user, group); err != nil {
		return err
	}
	if err := tx.Commit(); err != nil {
		return err
	}
	return nil
}

func (s *SQLiteStore) AddGroupOwner(user, group string) error {
	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	existsInOwners, err := s.userGroupPairExists(tx, "owners", user, group)
	if err != nil {
		return err
	}
	if existsInOwners {
		return fmt.Errorf("%s is already an owner of group %s", user, group)
	}
	if _, err = tx.Exec(`INSERT INTO owners (username, group_name) VALUES (?, ?)`, user, group); err != nil {
		return err
	}
	if err := tx.Commit(); err != nil {
		return err
	}
	return nil
}

func (s *SQLiteStore) getUsersByGroup(table, group string) ([]string, error) {
	query := fmt.Sprintf("SELECT username FROM %s WHERE group_name = ?", table)
	rows, err := s.db.Query(query, group)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var users []string
	for rows.Next() {
		var username string
		if err := rows.Scan(&username); err != nil {
			return nil, err
		}
		users = append(users, username)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return users, nil
}

func (s *SQLiteStore) GetGroupOwners(group string) ([]string, error) {
	return s.getUsersByGroup("owners", group)
}

func (s *SQLiteStore) GetGroupMembers(group string) ([]string, error) {
	return s.getUsersByGroup("user_to_group", group)
}

func (s *SQLiteStore) GetGroupDescription(group string) (string, error) {
	var description string
	query := `SELECT description FROM groups WHERE name = ?`
	if err := s.db.QueryRow(query, group).Scan(&description); err != nil {
		return "", err
	}
	return description, nil
}

func (s *SQLiteStore) parentChildGroupPairExists(tx *sql.Tx, parent, child string) (bool, error) {
	query := `SELECT EXISTS (SELECT 1 FROM group_to_group WHERE parent_group = ? AND child_group = ?)`
	var exists bool
	if err := tx.QueryRow(query, parent, child).Scan(&exists); err != nil {
		return false, err
	}
	return exists, nil
}

func (s *SQLiteStore) DoesGroupExist(group string) (bool, error) {
	query := `SELECT EXISTS (SELECT 1 FROM groups WHERE name = ?)`
	var exists bool
	if err := s.db.QueryRow(query, group).Scan(&exists); err != nil {
		return false, err
	}
	return exists, nil
}

func (s *SQLiteStore) AddChildGroup(parent, child string) error {
	if parent == child {
		return fmt.Errorf("parent and child groups can not have same name")
	}
	if _, err := s.DoesGroupExist(parent); err != nil {
		return fmt.Errorf("parent group name %s does not exist", parent)
	}
	if _, err := s.DoesGroupExist(child); err != nil {
		return fmt.Errorf("child group name %s does not exist", child)
	}
	parentGroups, err := s.GetAllTransitiveGroupsForGroup(parent)
	if err != nil {
		return err
	}
	for _, group := range parentGroups {
		if group.Name == child {
			return fmt.Errorf("circular reference detected: group %s is already a parent of group %s", child, parent)
		}
	}
	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	existsInGroupToGroup, err := s.parentChildGroupPairExists(tx, parent, child)
	if err != nil {
		return err
	}
	if existsInGroupToGroup {
		return fmt.Errorf("child group name %s already exists in group %s", child, parent)
	}
	if _, err := tx.Exec(`INSERT INTO group_to_group (parent_group, child_group) VALUES (?, ?)`, parent, child); err != nil {
		return err
	}
	if err := tx.Commit(); err != nil {
		return err
	}
	return nil
}

func (s *SQLiteStore) GetAvailableGroupsAsChild(group string) ([]string, error) {
	// TODO(dtabidze): Might have to add further logic to filter available groups as children.
	query := `
		SELECT name FROM groups
		WHERE name != ? AND name NOT IN (
			SELECT child_group FROM group_to_group WHERE parent_group = ?
		)`
	rows, err := s.db.Query(query, group, group)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var availableGroups []string
	for rows.Next() {
		var groupName string
		if err := rows.Scan(&groupName); err != nil {
			return nil, err
		}
		availableGroups = append(availableGroups, groupName)
	}
	return availableGroups, nil
}

func (s *SQLiteStore) GetAllTransitiveGroupsForUser(user string) ([]Group, error) {
	if groups, err := s.GetGroupsUserBelongsTo(user); err != nil {
		return nil, err
	} else {
		visited := map[string]struct{}{}
		return s.getAllParentGroupsRecursive(groups, visited)
	}
}

func (s *SQLiteStore) GetAllTransitiveGroupsForGroup(group string) ([]Group, error) {
	if p, err := s.GetGroupsGroupBelongsTo(group); err != nil {
		return nil, err
	} else {
		// Mark initial group as visited
		visited := map[string]struct{}{
			group: struct{}{},
		}
		return s.getAllParentGroupsRecursive(p, visited)
	}
}

func (s *SQLiteStore) getAllParentGroupsRecursive(groups []Group, visited map[string]struct{}) ([]Group, error) {
	var ret []Group
	for _, g := range groups {
		if _, ok := visited[g.Name]; ok {
			continue
		}
		visited[g.Name] = struct{}{}
		ret = append(ret, g)
		if p, err := s.GetGroupsGroupBelongsTo(g.Name); err != nil {
			return nil, err
		} else if res, err := s.getAllParentGroupsRecursive(p, visited); err != nil {
			return nil, err
		} else {
			ret = append(ret, res...)
		}
	}
	return ret, nil
}

func (s *SQLiteStore) GetGroupsGroupBelongsTo(group string) ([]Group, error) {
	query := `
        SELECT groups.name, groups.description
        FROM groups
        JOIN group_to_group ON groups.name = group_to_group.parent_group
        WHERE group_to_group.child_group = ?`
	rows, err := s.db.Query(query, group)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var parentGroups []Group
	for rows.Next() {
		var parentGroup Group
		if err := rows.Scan(&parentGroup.Name, &parentGroup.Description); err != nil {
			return nil, err
		}
		parentGroups = append(parentGroups, parentGroup)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return parentGroups, nil
}

func (s *SQLiteStore) GetDirectChildrenGroups(group string) ([]Group, error) {
	query := `
        SELECT groups.name, groups.description
        FROM groups
        JOIN group_to_group ON groups.name = group_to_group.child_group
        WHERE group_to_group.parent_group = ?`
	rows, err := s.db.Query(query, group)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var childrenGroups []Group
	for rows.Next() {
		var childGroup Group
		if err := rows.Scan(&childGroup.Name, &childGroup.Description); err != nil {
			return nil, err
		}
		childrenGroups = append(childrenGroups, childGroup)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return childrenGroups, nil
}

func (s *SQLiteStore) RemoveFromGroupToGroup(parent, child string) error {
	query := `DELETE FROM group_to_group WHERE parent_group = ? AND child_group = ?`
	rowDeleted, err := s.db.Exec(query, parent, child)
	if err != nil {
		return err
	}
	rowDeletedNumber, err := rowDeleted.RowsAffected()
	if err != nil {
		return err
	}
	if rowDeletedNumber == 0 {
		return fmt.Errorf("pair of parent '%s' and child '%s' groups not found", parent, child)
	}
	return nil
}

func (s *SQLiteStore) RemoveUserFromTable(username, groupName, tableName string) error {
	if tableName == "owners" {
		owners, err := s.GetGroupOwners(groupName)
		if err != nil {
			return err
		}
		if len(owners) == 1 {
			return fmt.Errorf("cannot remove the last owner of the group")
		}
	}
	query := fmt.Sprintf("DELETE FROM %s WHERE username = ? AND group_name = ?", tableName)
	rowDeleted, err := s.db.Exec(query, username, groupName)
	if err != nil {
		return err
	}
	rowDeletedNumber, err := rowDeleted.RowsAffected()
	if err != nil {
		return err
	}
	if rowDeletedNumber == 0 {
		return fmt.Errorf("pair of group '%s' and user '%s' not found", groupName, username)
	}
	return nil
}

func getLoggedInUser(r *http.Request) (string, error) {
	if user := r.Header.Get("X-User"); user != "" {
		return user, nil
	} else {
		return "", fmt.Errorf("unauthenticated")
	}
}

type Status int

const (
	Owner Status = iota
	Member
)

func (s *Server) Start() error {
	e := make(chan error)
	go func() {
		r := mux.NewRouter()
		r.PathPrefix("/static/").Handler(http.FileServer(http.FS(staticResources)))
		r.HandleFunc("/group/{group-name}/add-user/", s.addUserToGroupHandler)
		r.HandleFunc("/group/{parent-group}/add-child-group", s.addChildGroupHandler)
		r.HandleFunc("/group/{parent-group}/remove-child-group/{child-group}", s.removeChildGroupHandler)
		r.HandleFunc("/group/{group-name}/remove-owner/{username}", s.removeOwnerFromGroupHandler)
		r.HandleFunc("/group/{group-name}/remove-member/{username}", s.removeMemberFromGroupHandler)
		r.HandleFunc("/group/{group-name}", s.groupHandler)
		r.HandleFunc("/user/{username}", s.userHandler)
		r.HandleFunc("/create-group", s.createGroupHandler)
		r.HandleFunc("/", s.homePageHandler)
		e <- http.ListenAndServe(fmt.Sprintf(":%d", *port), r)
	}()
	go func() {
		r := mux.NewRouter()
		r.HandleFunc("/api/init", s.apiInitHandler)
		r.HandleFunc("/api/user/{username}", s.apiMemberOfHandler)
		e <- http.ListenAndServe(fmt.Sprintf(":%d", *apiPort), r)
	}()
	return <-e
}

type GroupData struct {
	Group      Group
	Membership string
}

func (s *Server) checkIsOwner(w http.ResponseWriter, user, group string) (bool, error) {
	isOwner, err := s.store.IsGroupOwner(user, group)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return false, err
	}
	if !isOwner {
		return false, fmt.Errorf("you are not the owner of the group %s", group)
	}
	return true, nil
}

func (s *Server) homePageHandler(w http.ResponseWriter, r *http.Request) {
	loggedInUser, err := getLoggedInUser(r)
	if err != nil {
		http.Error(w, "User Not Logged In", http.StatusUnauthorized)
		return
	}
	http.Redirect(w, r, "/user/"+loggedInUser, http.StatusSeeOther)
}

func (s *Server) userHandler(w http.ResponseWriter, r *http.Request) {
	loggedInUser, err := getLoggedInUser(r)
	if err != nil {
		http.Error(w, "User Not Logged In", http.StatusUnauthorized)
		return
	}
	vars := mux.Vars(r)
	user := strings.ToLower(vars["username"])
	// TODO(dtabidze): should check if username exists or not.
	loggedInUserPage := loggedInUser == user
	ownerGroups, err := s.store.GetGroupsOwnedBy(user)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	membershipGroups, err := s.store.GetGroupsUserBelongsTo(user)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	tmpl, err := template.New("index").Parse(indexHTML)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	transitiveGroups, err := s.store.GetAllTransitiveGroupsForUser(user)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	data := struct {
		OwnerGroups      []Group
		MembershipGroups []Group
		TransitiveGroups []Group
		LoggedInUserPage bool
		CurrentUser      string
	}{
		OwnerGroups:      ownerGroups,
		MembershipGroups: membershipGroups,
		TransitiveGroups: transitiveGroups,
		LoggedInUserPage: loggedInUserPage,
		CurrentUser:      user,
	}
	w.Header().Set("Content-Type", "text/html")
	if err := tmpl.Execute(w, data); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
}

func (s *Server) createGroupHandler(w http.ResponseWriter, r *http.Request) {
	loggedInUser, err := getLoggedInUser(r)
	if err != nil {
		http.Error(w, "User Not Logged In", http.StatusUnauthorized)
		return
	}
	if r.Method != http.MethodPost {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}
	if err := r.ParseForm(); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	var group Group
	group.Name = r.PostFormValue("group-name")
	if err := isValidGroupName(group.Name); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	group.Description = r.PostFormValue("description")
	if err := s.store.CreateGroup(loggedInUser, group); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	http.Redirect(w, r, "/", http.StatusSeeOther)
}

func (s *Server) groupHandler(w http.ResponseWriter, r *http.Request) {
	_, err := getLoggedInUser(r)
	if err != nil {
		http.Error(w, "User Not Logged In", http.StatusUnauthorized)
		return
	}
	vars := mux.Vars(r)
	groupName := vars["group-name"]
	exists, err := s.store.DoesGroupExist(groupName)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	if !exists {
		errorMsg := fmt.Sprintf("group with the name '%s' not found", groupName)
		http.Error(w, errorMsg, http.StatusNotFound)
		return
	}
	tmpl, err := template.New("group").Parse(groupHTML)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	owners, err := s.store.GetGroupOwners(groupName)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	members, err := s.store.GetGroupMembers(groupName)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	description, err := s.store.GetGroupDescription(groupName)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	availableGroups, err := s.store.GetAvailableGroupsAsChild(groupName)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	transitiveGroups, err := s.store.GetAllTransitiveGroupsForGroup(groupName)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	childGroups, err := s.store.GetDirectChildrenGroups(groupName)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	data := struct {
		GroupName        string
		Description      string
		Owners           []string
		Members          []string
		AvailableGroups  []string
		TransitiveGroups []Group
		ChildGroups      []Group
	}{
		GroupName:        groupName,
		Description:      description,
		Owners:           owners,
		Members:          members,
		AvailableGroups:  availableGroups,
		TransitiveGroups: transitiveGroups,
		ChildGroups:      childGroups,
	}
	if err := tmpl.Execute(w, data); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
}

func (s *Server) removeChildGroupHandler(w http.ResponseWriter, r *http.Request) {
	loggedInUser, err := getLoggedInUser(r)
	if err != nil {
		http.Error(w, "User Not Logged In", http.StatusUnauthorized)
		return
	}
	if r.Method == http.MethodPost {
		vars := mux.Vars(r)
		parentGroup := vars["parent-group"]
		childGroup := vars["child-group"]
		if err := isValidGroupName(parentGroup); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		if err := isValidGroupName(childGroup); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		if _, err := s.checkIsOwner(w, loggedInUser, parentGroup); err != nil {
			http.Error(w, err.Error(), http.StatusUnauthorized)
			return
		}
		err := s.store.RemoveFromGroupToGroup(parentGroup, childGroup)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		http.Redirect(w, r, "/group/"+parentGroup, http.StatusSeeOther)
	}
}

func (s *Server) removeOwnerFromGroupHandler(w http.ResponseWriter, r *http.Request) {
	loggedInUser, err := getLoggedInUser(r)
	if err != nil {
		http.Error(w, "User Not Logged In", http.StatusUnauthorized)
		return
	}
	if r.Method == http.MethodPost {
		vars := mux.Vars(r)
		username := vars["username"]
		groupName := vars["group-name"]
		tableName := "owners"
		if err := isValidGroupName(groupName); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		if _, err := s.checkIsOwner(w, loggedInUser, groupName); err != nil {
			http.Error(w, err.Error(), http.StatusUnauthorized)
			return
		}
		err := s.store.RemoveUserFromTable(username, groupName, tableName)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		http.Redirect(w, r, "/group/"+groupName, http.StatusSeeOther)
	}
}

func (s *Server) removeMemberFromGroupHandler(w http.ResponseWriter, r *http.Request) {
	loggedInUser, err := getLoggedInUser(r)
	if err != nil {
		http.Error(w, "User Not Logged In", http.StatusUnauthorized)
		return
	}
	if r.Method == http.MethodPost {
		vars := mux.Vars(r)
		username := vars["username"]
		groupName := vars["group-name"]
		tableName := "user_to_group"
		if err := isValidGroupName(groupName); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		if _, err := s.checkIsOwner(w, loggedInUser, groupName); err != nil {
			http.Error(w, err.Error(), http.StatusUnauthorized)
			return
		}
		err := s.store.RemoveUserFromTable(username, groupName, tableName)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		http.Redirect(w, r, "/group/"+groupName, http.StatusSeeOther)
	}
}

func (s *Server) addUserToGroupHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}
	loggedInUser, err := getLoggedInUser(r)
	if err != nil {
		http.Error(w, "User Not Logged In", http.StatusUnauthorized)
		return
	}
	vars := mux.Vars(r)
	groupName := vars["group-name"]
	if err := isValidGroupName(groupName); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	username := strings.ToLower(r.FormValue("username"))
	if username == "" {
		http.Error(w, "Username parameter is required", http.StatusBadRequest)
		return
	}
	status, err := convertStatus(r.FormValue("status"))
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	if _, err := s.checkIsOwner(w, loggedInUser, groupName); err != nil {
		http.Error(w, err.Error(), http.StatusUnauthorized)
		return
	}
	switch status {
	case Owner:
		err = s.store.AddGroupOwner(username, groupName)
	case Member:
		err = s.store.AddGroupMember(username, groupName)
	default:
		http.Error(w, "Invalid status", http.StatusBadRequest)
		return
	}
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	http.Redirect(w, r, "/group/"+groupName, http.StatusSeeOther)
}

func (s *Server) addChildGroupHandler(w http.ResponseWriter, r *http.Request) {
	// TODO(dtabidze): In future we might need to make one group OWNER of another and not just a member.
	if r.Method != http.MethodPost {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}
	loggedInUser, err := getLoggedInUser(r)
	if err != nil {
		http.Error(w, "User Not Logged In", http.StatusUnauthorized)
		return
	}
	vars := mux.Vars(r)
	parentGroup := vars["parent-group"]
	if err := isValidGroupName(parentGroup); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	childGroup := r.FormValue("child-group")
	if err := isValidGroupName(childGroup); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	if _, err := s.checkIsOwner(w, loggedInUser, parentGroup); err != nil {
		http.Error(w, err.Error(), http.StatusUnauthorized)
		return
	}
	if err := s.store.AddChildGroup(parentGroup, childGroup); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	http.Redirect(w, r, "/group/"+parentGroup, http.StatusSeeOther)
}

type initRequest struct {
	Owner  string   `json:"owner"`
	Groups []string `json:"groups"`
}

func (s *Server) apiInitHandler(w http.ResponseWriter, r *http.Request) {
	var req initRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	if err := s.store.Init(req.Owner, req.Groups); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
}

type userInfo struct {
	MemberOf []string `json:"memberOf"`
}

func (s *Server) apiMemberOfHandler(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	user, ok := vars["username"]
	if !ok || user == "" {
		http.Error(w, "Username parameter is required", http.StatusBadRequest)
		return
	}
	user = strings.ToLower(user)
	transitiveGroups, err := s.store.GetAllTransitiveGroupsForUser(user)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	var groupNames []string
	for _, group := range transitiveGroups {
		groupNames = append(groupNames, group.Name)
	}
	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(userInfo{groupNames}); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
}

func convertStatus(status string) (Status, error) {
	switch status {
	case "Owner":
		return Owner, nil
	case "Member":
		return Member, nil
	default:
		return Owner, fmt.Errorf("invalid status: %s", status)
	}
}

func isValidGroupName(group string) error {
	if strings.TrimSpace(group) == "" {
		return fmt.Errorf("group name can't be empty or contain only whitespaces")
	}
	validGroupName := regexp.MustCompile(`^[a-z0-9\-_:.\/ ]+$`)
	if !validGroupName.MatchString(group) {
		return fmt.Errorf("group name should contain only lowercase letters, digits, -, _, :, ., /")
	}
	return nil
}

func main() {
	flag.Parse()
	db, err := sql.Open("sqlite3", *dbPath)
	if err != nil {
		panic(err)
	}
	store, err := NewSQLiteStore(db)
	if err != nil {
		panic(err)
	}
	s := Server{store}
	log.Fatal(s.Start())
}