package storage

import (
	"errors"
	"fmt"
)

// ErrLastAdmin protects the server from losing its last administrator.
var ErrLastAdmin = errors.New("Der letzte Server-Administrator kann nicht gelöscht werden. Bitte ernenne vorher ein anderes Konto zum Administrator.")

// PurgeUserData deletes everything the user owns – thoughts and tasks, notes (with blocks, history and
// shares), folders, shared folders, task lists and lists – in one transaction. The account, its
// settings, themes, API keys and group memberships stay. Other people's tasks in the user's task lists
// become their own personal tasks, as when a single list is deleted.
func (s *Store) PurgeUserData(userID string) error {
	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()

	ownDocs := `(SELECT id FROM documents WHERE user_id = ?)`
	ownTaskLists := `(SELECT id FROM task_lists WHERE user_id = ?)`
	ownFolders := `(SELECT id FROM workspace_shared_folders WHERE owner_id = ?)`
	stmts := []struct {
		q    string
		args int // how many times userID is passed
	}{
		// Task lists: keep the tasks of others, drop shares and the lists
		{`UPDATE thoughts SET task_list_id = '' WHERE task_list_id IN ` + ownTaskLists + ` AND user_id != ?`, 2},
		{`DELETE FROM task_list_shares WHERE task_list_id IN ` + ownTaskLists, 1},
		{`DELETE FROM task_lists WHERE user_id = ?`, 1},
		// Tasks of others linked to blocks of the user's notes lose the link
		{`UPDATE thoughts SET converted_type = '', converted_ref_id = '' WHERE converted_type = 'document_block'
		  AND substr(converted_ref_id, 1, instr(converted_ref_id, ':') - 1) IN ` + ownDocs, 1},
		{`DELETE FROM thoughts WHERE user_id = ?`, 1},
		// Shared folders owned by the user
		{`UPDATE documents SET shared_folder_id = '', sub_folder_path = '' WHERE shared_folder_id IN ` + ownFolders, 1},
		{`DELETE FROM workspace_folder_mounts WHERE folder_id IN ` + ownFolders, 1},
		{`DELETE FROM workspace_folder_shares WHERE folder_id IN ` + ownFolders, 1},
		{`DELETE FROM workspace_folders WHERE shared_folder_id IN ` + ownFolders, 1},
		{`DELETE FROM workspace_shared_folders WHERE owner_id = ?`, 1},
		// Notes (history tables cascade with the document)
		{`DELETE FROM blocks WHERE document_id IN ` + ownDocs, 1},
		{`DELETE FROM block_tags WHERE document_id IN ` + ownDocs, 1},
		{`DELETE FROM doc_user_folders WHERE doc_id IN ` + ownDocs, 1},
		{`DELETE FROM doc_team_shares WHERE doc_id IN ` + ownDocs, 1},
		{`DELETE FROM doc_shares WHERE doc_id IN ` + ownDocs, 1},
		{`DELETE FROM documents WHERE user_id = ?`, 1},
		// The user's own placement of notes, folders, pins and tag pages
		{`DELETE FROM doc_user_folders WHERE user_id = ?`, 1},
		{`DELETE FROM doc_pins WHERE user_id = ?`, 1},
		{`DELETE FROM workspace_folders WHERE user_id = ?`, 1},
		{`DELETE FROM tag_pages WHERE user_id = ?`, 1},
		// Lists (items cascade)
		{`DELETE FROM list_shares WHERE list_id IN (SELECT id FROM lists WHERE user_id = ?)`, 1},
		{`DELETE FROM lists WHERE user_id = ?`, 1},
	}
	for _, st := range stmts {
		args := make([]interface{}, st.args)
		for i := range args {
			args[i] = userID
		}
		if _, err := tx.Exec(st.q, args...); err != nil {
			return fmt.Errorf("Daten löschen: %w", err)
		}
	}
	if err := tx.Commit(); err != nil {
		return err
	}
	s.PruneTaskAssignees()
	return nil
}

// IsLastAdmin reports whether userID is an administrator and no other one exists.
func (s *Store) IsLastAdmin(userID string) bool {
	var role string
	if err := s.db.QueryRow(`SELECT role FROM users WHERE id = ?`, userID).Scan(&role); err != nil || role != "admin" {
		return false
	}
	var others int
	_ = s.db.QueryRow(`SELECT COUNT(*) FROM users WHERE role = 'admin' AND id != ?`, userID).Scan(&others)
	return others == 0
}

// DeleteOwnAccount removes the user with all data; refused for the last administrator.
func (s *Store) DeleteOwnAccount(userID string) error {
	if s.IsLastAdmin(userID) {
		return ErrLastAdmin
	}
	return s.DeleteUser(userID)
}