Notes/src/services/consistency_checks.js

"use strict";

const sql = require('./sql');
const sqlInit = require('./sql_init');
const log = require('./log');
const ws = require('./ws');
const syncMutexService = require('./sync_mutex');
const cls = require('./cls');
const entityChangesService = require('./entity_changes');
const optionsService = require('./options');
const BBranch = require('../becca/entities/bbranch');
const revisionService = require('./revisions');
const becca = require('../becca/becca');
const utils = require('../services/utils');
const eraseService = require('../services/erase.js');
const {sanitizeAttributeName} = require('./sanitize_attribute_name');
const noteTypes = require('../services/note_types.js').getNoteTypeNames();

class ConsistencyChecks {
    /**
     * @param autoFix - automatically fix all encountered problems. False is only for debugging during development (fail fast)
     */
    constructor(autoFix) {
        this.autoFix = autoFix;
        this.unrecoveredConsistencyErrors = false;
        this.fixedIssues = false;
        this.reloadNeeded = false;
    }

    findAndFixIssues(query, fixerCb) {
        const results = sql.getRows(query);

        for (const res of results) {
            try {
                sql.transactional(() => fixerCb(res));

                if (this.autoFix) {
                    this.fixedIssues = true;
                } else {
                    this.unrecoveredConsistencyErrors = true;
                }
            } catch (e) {
                logError(`Fixer failed with ${e.message} ${e.stack}`);
                this.unrecoveredConsistencyErrors = true;
            }
        }

        return results;
    }

    checkTreeCycles() {
        const childToParents = {};
        const rows = sql.getRows("SELECT noteId, parentNoteId FROM branches WHERE isDeleted = 0");

        for (const row of rows) {
            const childNoteId = row.noteId;
            const parentNoteId = row.parentNoteId;

            childToParents[childNoteId] = childToParents[childNoteId] || [];
            childToParents[childNoteId].push(parentNoteId);
        }

        /** @returns {boolean} true if cycle was found and we should try again */
        const checkTreeCycle = (noteId, path) => {
            if (noteId === 'root') {
                return false;
            }

            for (const parentNoteId of childToParents[noteId]) {
                if (path.includes(parentNoteId)) {
                    if (this.autoFix) {
                        const branch = becca.getBranchFromChildAndParent(noteId, parentNoteId);
                        branch.markAsDeleted('cycle-autofix');
                        logFix(`Branch '${branch.branchId}' between child '${noteId}' and parent '${parentNoteId}' has been deleted since it was causing a tree cycle.`);

                        return true;
                    }
                    else {
                        logError(`Tree cycle detected at parent-child relationship: '${parentNoteId}' - '${noteId}', whole path: '${path}'`);

                        this.unrecoveredConsistencyErrors = true;
                    }
                } else {
                    const newPath = path.slice();
                    newPath.push(noteId);

                    const retryNeeded = checkTreeCycle(parentNoteId, newPath);

                    if (retryNeeded) {
                        return true;
                    }
                }
            }

            return false;
        };

        const noteIds = Object.keys(childToParents);

        for (const noteId of noteIds) {
            const retryNeeded = checkTreeCycle(noteId, []);

            if (retryNeeded) {
                return true;
            }
        }

        return false;
    }

    checkAndRepairTreeCycles() {
        let treeFixed = false;

        while (this.checkTreeCycles()) {
            // fixing cycle means deleting branches, we might need to create a new branch to recover the note
            this.findExistencyIssues();

            treeFixed = true;
        }

        if (treeFixed) {
            this.reloadNeeded = true;
        }
    }

    findBrokenReferenceIssues() {
        this.findAndFixIssues(`
                    SELECT branchId, branches.noteId
                    FROM branches
                      LEFT JOIN notes USING (noteId)
                    WHERE branches.isDeleted = 0
                      AND notes.noteId IS NULL`,
            ({branchId, noteId}) => {
                if (this.autoFix) {
                    const branch = becca.getBranch(branchId);
                    branch.markAsDeleted();

                    this.reloadNeeded = true;

                    logFix(`Branch '${branchId}' has been deleted since it references missing note '${noteId}'`);
                } else {
                    logError(`Branch '${branchId}' references missing note '${noteId}'`);
                }
            });

        this.findAndFixIssues(`
                    SELECT branchId, branches.parentNoteId AS parentNoteId
                    FROM branches
                      LEFT JOIN notes ON notes.noteId = branches.parentNoteId
                    WHERE branches.isDeleted = 0
                      AND branches.noteId != 'root'
                      AND notes.noteId IS NULL`,
            ({branchId, parentNoteId}) => {
                if (this.autoFix) {
                    // Delete the old branch and recreate it with root as parent.
                    const oldBranch = becca.getBranch(branchId);
                    const noteId = oldBranch.noteId;
                    oldBranch.markAsDeleted("missing-parent");

                    let message = `Branch '${branchId}' was missing parent note '${parentNoteId}', so it was deleted. `;

                    if (becca.getNote(noteId).getParentBranches().length === 0) {
                        const newBranch = new BBranch({
                            parentNoteId: 'root',
                            noteId: noteId,
                            prefix: 'recovered'
                        }).save();

                        message += `${newBranch.branchId} was created in the root instead.`;
                    } else {
                        message += `There is one or more valid branches, so no new one will be created as a replacement.`;
                    }

                    this.reloadNeeded = true;

                    logFix(message);
                } else {
                    logError(`Branch '${branchId}' references missing parent note '${parentNoteId}'`);
                }
            });

        this.findAndFixIssues(`
                    SELECT attributeId, attributes.noteId
                    FROM attributes
                      LEFT JOIN notes USING (noteId)
                    WHERE attributes.isDeleted = 0
                      AND notes.noteId IS NULL`,
            ({attributeId, noteId}) => {
                if (this.autoFix) {
                    const attribute = becca.getAttribute(attributeId);
                    attribute.markAsDeleted();

                    this.reloadNeeded = true;

                    logFix(`Attribute '${attributeId}' has been deleted since it references missing source note '${noteId}'`);
                } else {
                    logError(`Attribute '${attributeId}' references missing source note '${noteId}'`);
                }
            });

        this.findAndFixIssues(`
                    SELECT attributeId, attributes.value AS noteId
                    FROM attributes
                      LEFT JOIN notes ON notes.noteId = attributes.value
                    WHERE attributes.isDeleted = 0
                      AND attributes.type = 'relation'
                      AND notes.noteId IS NULL`,
            ({attributeId, noteId}) => {
                if (this.autoFix) {
                    const attribute = becca.getAttribute(attributeId);
                    attribute.markAsDeleted();

                    this.reloadNeeded = true;

                    logFix(`Relation '${attributeId}' has been deleted since it references missing note '${noteId}'`)
                } else {
                    logError(`Relation '${attributeId}' references missing note '${noteId}'`)
                }
            });

        this.findAndFixIssues(`
                    SELECT attachmentId, attachments.ownerId AS noteId
                    FROM attachments
                    WHERE attachments.ownerId NOT IN (
                            SELECT noteId FROM notes
                            UNION ALL
                            SELECT revisionId FROM revisions
                        )
                      AND attachments.isDeleted = 0`,
            ({attachmentId, ownerId}) => {
                if (this.autoFix) {
                    const attachment = becca.getAttachment(attachmentId);
                    attachment.markAsDeleted();

                    this.reloadNeeded = false;

                    logFix(`Attachment '${attachmentId}' has been deleted since it references missing note/revision '${ownerId}'`);
                } else {
                    logError(`Attachment '${attachmentId}' references missing note/revision '${ownerId}'`);
                }
            });
    }

    findExistencyIssues() {
        // the principle for fixing inconsistencies is that if the note itself is deleted (isDeleted=true) then all related
        // entities should be also deleted (branches, attributes), but if the note is not deleted,
        // then at least one branch should exist.

        // the order here is important - first we might need to delete inconsistent branches, and after that
        // another check might create missing branch
        this.findAndFixIssues(`
                    SELECT branchId,
                           noteId
                    FROM branches
                      JOIN notes USING (noteId)
                    WHERE notes.isDeleted = 1
                      AND branches.isDeleted = 0`,
            ({branchId, noteId}) => {
                if (this.autoFix) {
                    const branch = becca.getBranch(branchId);
                    branch.markAsDeleted();

                    this.reloadNeeded = true;

                    logFix(`Branch '${branchId}' has been deleted since the associated note '${noteId}' is deleted.`);
                } else {
                    logError(`Branch '${branchId}' is not deleted even though the associated note '${noteId}' is deleted.`)
                }
            });

        this.findAndFixIssues(`
            SELECT branchId,
                   parentNoteId
            FROM branches
              JOIN notes AS parentNote ON parentNote.noteId = branches.parentNoteId
            WHERE parentNote.isDeleted = 1
              AND branches.isDeleted = 0
        `, ({branchId, parentNoteId}) => {
            if (this.autoFix) {
                const branch = becca.getBranch(branchId);
                branch.markAsDeleted();

                this.reloadNeeded = true;

                logFix(`Branch '${branchId}' has been deleted since the associated parent note '${parentNoteId}' is deleted.`);
            } else {
                logError(`Branch '${branchId}' is not deleted even though the associated parent note '${parentNoteId}' is deleted.`)
            }
        });

        this.findAndFixIssues(`
            SELECT DISTINCT notes.noteId
            FROM notes
              LEFT JOIN branches ON notes.noteId = branches.noteId AND branches.isDeleted = 0
            WHERE notes.isDeleted = 0
              AND branches.branchId IS NULL
        `, ({noteId}) => {
            if (this.autoFix) {
                const branch = new BBranch({
                    parentNoteId: 'root',
                    noteId: noteId,
                    prefix: 'recovered'
                }).save();

                this.reloadNeeded = true;

                logFix(`Created missing branch '${branch.branchId}' for note '${noteId}'`);
            } else {
                logError(`No undeleted branch found for note '${noteId}'`);
            }
        });

        // there should be a unique relationship between note and its parent
        this.findAndFixIssues(`
                    SELECT noteId,
                           parentNoteId
                    FROM branches
                    WHERE branches.isDeleted = 0
                    GROUP BY branches.parentNoteId,
                             branches.noteId
                    HAVING COUNT(1) > 1`,
            ({noteId, parentNoteId}) => {
                if (this.autoFix) {
                    const branchIds = sql.getColumn(
                            `SELECT branchId
                             FROM branches
                             WHERE noteId = ?
                               and parentNoteId = ?
                               and isDeleted = 0
                             ORDER BY utcDateModified`, [noteId, parentNoteId]);

                    const branches = branchIds.map(branchId => becca.getBranch(branchId));

                    // it's not necessarily "original" branch, it's just the only one which will survive
                    const origBranch = branches[0];

                    // delete all but the first branch
                    for (const branch of branches.slice(1)) {
                        branch.markAsDeleted();

                        logFix(`Removing branch '${branch.branchId}' since it's a parent-child duplicate of branch '${origBranch.branchId}'`);
                    }

                    this.reloadNeeded = true;
                } else {
                    logError(`Duplicate branches for note '${noteId}' and parent '${parentNoteId}'`);
                }
            });

        this.findAndFixIssues(`
                    SELECT attachmentId,
                           attachments.ownerId AS noteId
                    FROM attachments
                      JOIN notes ON notes.noteId = attachments.ownerId
                    WHERE notes.isDeleted = 1
                      AND attachments.isDeleted = 0`,
            ({attachmentId, noteId}) => {
                if (this.autoFix) {
                    const attachment = becca.getAttachment(attachmentId);
                    attachment.markAsDeleted();

                    this.reloadNeeded = false;

                    logFix(`Attachment '${attachmentId}' has been deleted since the associated note '${noteId}' is deleted.`);
                } else {
                    logError(`Attachment '${attachmentId}' is not deleted even though the associated note '${noteId}' is deleted.`)
                }
            });
    }

    findLogicIssues() {
        const noteTypesStr = noteTypes.map(nt => `'${nt}'`).join(", ");

        this.findAndFixIssues(`
                    SELECT noteId, type
                    FROM notes
                    WHERE isDeleted = 0
                      AND type NOT IN (${noteTypesStr})`,
            ({noteId, type}) => {
                if (this.autoFix) {
                    const note = becca.getNote(noteId);
                    note.type = 'file'; // file is a safe option to recover notes if the type is not known
                    note.save();

                    this.reloadNeeded = true;

                    logFix(`Note '${noteId}' type has been change to file since it had invalid type '${type}'`)
                } else {
                    logError(`Note '${noteId}' has invalid type '${type}'`);
                }
            });

        this.findAndFixIssues(`
                    SELECT notes.noteId, notes.isProtected, notes.type, notes.mime
                    FROM notes
                      LEFT JOIN blobs USING (blobId)
                    WHERE blobs.blobId IS NULL
                        AND notes.isDeleted = 0`,
            ({noteId, isProtected, type, mime}) => {
                if (this.autoFix) {
                    // it might be possible that the blob is not available only because of the interrupted
                    // sync, and it will come later. It's therefore important to guarantee that this artificial
                    // record won't overwrite the real one coming from the sync.
                    const fakeDate = "2000-01-01 00:00:00Z";

                    const blankContent = getBlankContent(isProtected, type, mime);
                    const blobId = utils.hashedBlobId(blankContent);
                    const blobAlreadyExists = !!sql.getValue("SELECT 1 FROM blobs WHERE blobId = ?", [blobId]);

                    if (!blobAlreadyExists) {
                        // manually creating row since this can also affect deleted notes
                        sql.upsert("blobs", "blobId", {
                            noteId: noteId,
                            content: blankContent,
                            utcDateModified: fakeDate,
                            dateModified: fakeDate
                        });

                        const hash = utils.hash(utils.randomString(10));

                        entityChangesService.putEntityChange({
                            entityName: 'blobs',
                            entityId: blobId,
                            hash: hash,
                            isErased: false,
                            utcDateChanged: fakeDate,
                            isSynced: true
                        });
                    }

                    sql.execute("UPDATE notes SET blobId = ? WHERE noteId = ?", [blobId, noteId]);

                    this.reloadNeeded = true;

                    logFix(`Note '${noteId}' content was set to empty string since there was no corresponding row`);
                } else {
                    logError(`Note '${noteId}' content row does not exist`);
                }
            });

        if (sqlInit.getDbSize() < 500000) {
            // querying for "content IS NULL" is expensive since content is not indexed. See e.g. https://github.com/zadam/trilium/issues/2887

            this.findAndFixIssues(`
                        SELECT notes.noteId, notes.type, notes.mime
                        FROM notes
                          JOIN blobs USING (blobId)
                        WHERE isDeleted = 0
                          AND isProtected = 0
                          AND content IS NULL`,
                ({noteId, type, mime}) => {
                    if (this.autoFix) {
                        const note = becca.getNote(noteId);
                        const blankContent = getBlankContent(false, type, mime);
                        note.setContent(blankContent);

                        this.reloadNeeded = true;

                        logFix(`Note '${noteId}' content was set to '${blankContent}' since it was null even though it is not deleted`);
                    } else {
                        logError(`Note '${noteId}' content is null even though it is not deleted`);
                    }
                });
        }

        this.findAndFixIssues(`
                    SELECT revisions.revisionId, blobs.blobId
                    FROM revisions
                      LEFT JOIN blobs USING (blobId)
                    WHERE blobs.blobId IS NULL`,
            ({revisionId, blobId}) => {
                if (this.autoFix) {
                    eraseService.eraseRevisions([revisionId]);

                    this.reloadNeeded = true;

                    logFix(`Note revision '${revisionId}' was erased since the referenced blob '${blobId}' did not exist.`);
                } else {
                    logError(`Note revision '${revisionId}' blob '${blobId}' does not exist`);
                }
            });

        this.findAndFixIssues(`
                    SELECT attachments.attachmentId, blobs.blobId
                    FROM attachments
                      LEFT JOIN blobs USING (blobId)
                    WHERE blobs.blobId IS NULL`,
            ({attachmentId, blobId}) => {
                if (this.autoFix) {
                    eraseService.eraseAttachments([attachmentId]);

                    this.reloadNeeded = true;

                    logFix(`Attachment '${attachmentId}' was erased since the referenced blob '${blobId}' did not exist.`);
                } else {
                    logError(`Attachment '${attachmentId}' blob '${blobId}' does not exist`);
                }
            });

        this.findAndFixIssues(`
                    SELECT parentNoteId
                    FROM branches
                      JOIN notes ON notes.noteId = branches.parentNoteId
                    WHERE notes.isDeleted = 0
                      AND notes.type == 'search'
                      AND branches.isDeleted = 0`,
            ({parentNoteId}) => {
                if (this.autoFix) {
                    const branchIds = sql.getColumn(`
                        SELECT branchId
                        FROM branches
                        WHERE isDeleted = 0
                          AND parentNoteId = ?`, [parentNoteId]);

                    const branches = branchIds.map(branchId => becca.getBranch(branchId));

                    for (const branch of branches) {
                        // delete the old wrong branch
                        branch.markAsDeleted("parent-is-search");

                        // create a replacement branch in root parent
                        new BBranch({
                            parentNoteId: 'root',
                            noteId: branch.noteId,
                            prefix: 'recovered'
                        }).save();

                        logFix(`Note '${branch.noteId}' has been moved to root since it was a child of a search note '${parentNoteId}'`)
                    }

                    this.reloadNeeded = true;
                } else {
                    logError(`Search note '${parentNoteId}' has children`);
                }
            });

        this.findAndFixIssues(`
                    SELECT attributeId
                    FROM attributes
                    WHERE isDeleted = 0
                      AND type = 'relation'
                      AND value = ''`,
            ({attributeId}) => {
                if (this.autoFix) {
                    const relation = becca.getAttribute(attributeId);
                    relation.markAsDeleted();

                    this.reloadNeeded = true;

                    logFix(`Removed relation '${relation.attributeId}' of name '${relation.name}' with empty target.`);
                } else {
                    logError(`Relation '${attributeId}' has empty target.`);
                }
            });

        this.findAndFixIssues(`
                    SELECT attributeId,
                           type
                    FROM attributes
                    WHERE isDeleted = 0
                      AND type != 'label'
                      AND type != 'relation'`,
            ({attributeId, type}) => {
                if (this.autoFix) {
                    const attribute = becca.getAttribute(attributeId);
                    attribute.type = 'label';
                    attribute.save();

                    this.reloadNeeded = true;

                    logFix(`Attribute '${attributeId}' type was changed to label since it had invalid type '${type}'`);
                } else {
                    logError(`Attribute '${attributeId}' has invalid type '${type}'`);
                }
            });

        this.findAndFixIssues(`
                    SELECT attributeId,
                           attributes.noteId
                    FROM attributes
                    JOIN notes ON attributes.noteId = notes.noteId
                    WHERE attributes.isDeleted = 0
                      AND notes.isDeleted = 1`,
            ({attributeId, noteId}) => {
                if (this.autoFix) {
                    const attribute = becca.getAttribute(attributeId);
                    attribute.markAsDeleted();

                    this.reloadNeeded = true;

                    logFix(`Removed attribute '${attributeId}' because owning note '${noteId}' is also deleted.`);
                } else {
                    logError(`Attribute '${attributeId}' is not deleted even though owning note '${noteId}' is deleted.`);
                }
            });

        this.findAndFixIssues(`
                    SELECT attributeId,
                           attributes.value AS targetNoteId
                    FROM attributes
                    JOIN notes ON attributes.value = notes.noteId
                    WHERE attributes.type = 'relation'
                      AND attributes.isDeleted = 0
                      AND notes.isDeleted = 1`,
            ({attributeId, targetNoteId}) => {
                if (this.autoFix) {
                    const attribute = becca.getAttribute(attributeId);
                    attribute.markAsDeleted();

                    this.reloadNeeded = true;

                    logFix(`Removed attribute '${attributeId}' because target note '${targetNoteId}' is also deleted.`);
                } else {
                    logError(`Attribute '${attributeId}' is not deleted even though target note '${targetNoteId}' is deleted.`);
                }
            });
    }

    runEntityChangeChecks(entityName, key) {
        this.findAndFixIssues(`
            SELECT ${key} as entityId
            FROM ${entityName}
            LEFT JOIN entity_changes ec ON ec.entityName = '${entityName}' AND ec.entityId = ${entityName}.${key} 
            WHERE ec.id IS NULL`,
            ({entityId}) => {
                const entityRow = sql.getRow(`SELECT * FROM ${entityName} WHERE ${key} = ?`, [entityId]);

                if (this.autoFix) {
                    entityChangesService.putEntityChange({
                        entityName,
                        entityId,
                        hash: utils.randomString(10), // doesn't matter, will force sync, but that's OK
                        isErased: false,
                        utcDateChanged: entityRow.utcDateModified || entityRow.utcDateCreated,
                        isSynced: entityName !== 'options' || entityRow.isSynced
                    });

                    logFix(`Created missing entity change for entityName '${entityName}', entityId '${entityId}'`);
                } else {
                    logError(`Missing entity change for entityName '${entityName}', entityId '${entityId}'`);
                }
            });

        this.findAndFixIssues(`
            SELECT id, entityId
            FROM entity_changes 
            LEFT JOIN ${entityName} ON entityId = ${entityName}.${key} 
            WHERE
              entity_changes.isErased = 0
              AND entity_changes.entityName = '${entityName}' 
              AND ${entityName}.${key} IS NULL`,
                ({id, entityId}) => {
                    if (this.autoFix) {
                        sql.execute("DELETE FROM entity_changes WHERE entityName = ? AND entityId = ?", [entityName, entityId]);

                        logFix(`Deleted extra entity change id '${id}', entityName '${entityName}', entityId '${entityId}'`);
                    } else {
                        logError(`Unrecognized entity change id '${id}', entityName '${entityName}', entityId '${entityId}'`);
                    }
                });

        this.findAndFixIssues(`
            SELECT id, entityId
            FROM entity_changes 
            JOIN ${entityName} ON entityId = ${entityName}.${key} 
            WHERE
              entity_changes.isErased = 1
              AND entity_changes.entityName = '${entityName}'`,
            ({id, entityId}) => {
                if (this.autoFix) {
                    sql.execute(`DELETE FROM ${entityName} WHERE ${key} = ?`, [entityId]);

                    this.reloadNeeded = true;

                    logFix(`Erasing entityName '${entityName}', entityId '${entityId}' since entity change id '${id}' has it as erased.`);
                } else {
                    logError(`Entity change id '${id}' has entityName '${entityName}', entityId '${entityId}' as erased, but it's not.`);
                }
            });
    }

    findEntityChangeIssues() {
        this.runEntityChangeChecks("notes", "noteId");
        this.runEntityChangeChecks("revisions", "revisionId");
        this.runEntityChangeChecks("attachments", "attachmentId");
        this.runEntityChangeChecks("blobs", "blobId");
        this.runEntityChangeChecks("branches", "branchId");
        this.runEntityChangeChecks("attributes", "attributeId");
        this.runEntityChangeChecks("etapi_tokens", "etapiTokenId");
        this.runEntityChangeChecks("options", "name");
    }

    findWronglyNamedAttributes() {
        const attrNames = sql.getColumn(`SELECT DISTINCT name FROM attributes`);

        for (const origName of attrNames) {
            const fixedName = sanitizeAttributeName(origName);

            if (fixedName !== origName) {
                if (this.autoFix) {
                    // there isn't a good way to update this:
                    // - just SQL query will fix it in DB but not notify frontend (or other caches) that it has been fixed
                    // - renaming the attribute would break the invariant that single attribute never changes the name
                    // - deleting the old attribute and creating new will create duplicates across synchronized cluster (specifically in the initial migration)
                    // But in general, we assume there won't be many such problems
                    sql.execute('UPDATE attributes SET name = ? WHERE name = ?', [fixedName, origName]);

                    this.fixedIssues = true;
                    this.reloadNeeded = true;

                    logFix(`Renamed incorrectly named attributes '${origName}' to '${fixedName}'`);
                }
                else {
                    this.unrecoveredConsistencyErrors = true;

                    logFix(`There are incorrectly named attributes '${origName}'`);
                }
            }
        }
    }

    findSyncIssues() {
        const lastSyncedPush = parseInt(sql.getValue("SELECT value FROM options WHERE name = 'lastSyncedPush'"));
        const maxEntityChangeId = sql.getValue("SELECT MAX(id) FROM entity_changes");

        if (lastSyncedPush > maxEntityChangeId) {
            if (this.autoFix) {
                sql.execute("UPDATE options SET value = ? WHERE name = 'lastSyncedPush'", [maxEntityChangeId]);

                this.fixedIssues = true;

                logFix(`Fixed incorrect lastSyncedPush - was ${lastSyncedPush}, needs to be at maximum ${maxEntityChangeId}`);
            }
            else {
                this.unrecoveredConsistencyErrors = true;

                logFix(`Incorrect lastSyncedPush - is ${lastSyncedPush}, needs to be at maximum ${maxEntityChangeId}`);
            }
        }
    }

    runAllChecksAndFixers() {
        this.unrecoveredConsistencyErrors = false;
        this.fixedIssues = false;
        this.reloadNeeded = false;

        this.findEntityChangeIssues();

        this.findBrokenReferenceIssues();

        this.findExistencyIssues();

        this.findLogicIssues();

        this.findWronglyNamedAttributes();

        this.findSyncIssues();

        // root branch should always be expanded
        sql.execute("UPDATE branches SET isExpanded = 1 WHERE noteId = 'root'");

        if (!this.unrecoveredConsistencyErrors) {
            // we run this only if basic checks passed since this assumes basic data consistency

            this.checkAndRepairTreeCycles();
        }

        if (this.reloadNeeded) {
            require('../becca/becca_loader').reload("consistency checks need becca reload");
        }

        return !this.unrecoveredConsistencyErrors;
    }

    runDbDiagnostics() {
        function getTableRowCount(tableName) {
            const count = sql.getValue(`SELECT COUNT(1) FROM ${tableName}`);

            return `${tableName}: ${count}`;
        }

        const tables = [ "notes", "revisions", "attachments", "branches", "attributes", "etapi_tokens", "blobs" ];

        log.info(`Table counts: ${tables.map(tableName => getTableRowCount(tableName)).join(", ")}`);
    }

    async runChecks() {
        let elapsedTimeMs;

        await syncMutexService.doExclusively(() => {
            const startTimeMs = Date.now();

            this.runDbDiagnostics();

            this.runAllChecksAndFixers();

            elapsedTimeMs = Date.now() - startTimeMs;
        });

        if (this.unrecoveredConsistencyErrors) {
            log.info(`Consistency checks failed (took ${elapsedTimeMs}ms)`);

            ws.sendMessageToAllClients({type: 'consistency-checks-failed'});
        } else {
            log.info(`All consistency checks passed ` +
                (this.fixedIssues ? "after some fixes" : "with no errors detected") +
                ` (took ${elapsedTimeMs}ms)`
            );
        }
    }
}

function getBlankContent(isProtected, type, mime) {
    if (isProtected) {
        return null; // this is wrong for protected non-erased notes, but we cannot create a valid value without a password
    }

    if (mime === 'application/json') {
        return '{}';
    }

    return ''; // empty string might be a wrong choice for some note types, but it's the best guess
}

function logFix(message) {
    log.info(`Consistency issue fixed: ${message}`);
}

function logError(message) {
    log.info(`Consistency error: ${message}`);
}

function runPeriodicChecks() {
    const autoFix = optionsService.getOptionBool('autoFixConsistencyIssues');

    const consistencyChecks = new ConsistencyChecks(autoFix);
    consistencyChecks.runChecks();
}

async function runOnDemandChecks(autoFix) {
    const consistencyChecks = new ConsistencyChecks(autoFix);
    await consistencyChecks.runChecks();
}

function runEntityChangesChecks() {
    const consistencyChecks = new ConsistencyChecks(true);
    consistencyChecks.findEntityChangeIssues();
}

sqlInit.dbReady.then(() => {
    setInterval(cls.wrap(runPeriodicChecks), 60 * 60 * 1000);

    // kickoff checks soon after startup (to not block the initial load)
    setTimeout(cls.wrap(runPeriodicChecks), 4 * 1000);
});

module.exports = {
    runOnDemandChecks,
    runEntityChangesChecks
};