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docs/source/technical/storage.rst

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+.. _docs_technical_storage:
+
+******************
+How Data is Stored
+******************
+
+This chapter contains details of how novelWriter stores and handles the project data.
+
+
+Project Structure
+=================
+
+All novelWriter files are written with utf-8 encoding. Since Python automatically converts Unix
+line endings to Windows line endings on Windows systems, novelWriter does not make any adaptations
+to the formatting on Windows systems. This is handled entirely by the Python standard library.
+Python also handles this when working on the same files on both Windows and Unix-based operating
+systems.
+
+
+Main Project File
+-----------------
+
+The project itself requires a dedicated folder for storing its files, where novelWriter will create
+its own "file system" where the project's folder and file hierarchy is described in a project XML
+file. This is the main project file in the project's root folder with the name ``nwProject.nwx``.
+This file also contains all the meta data required for the project (except the index data), and a
+number of related project settings.
+
+If this file is lost or corrupted, the structure of the project is lost, although not the text
+itself. It is important to keep this file backed up, either through the built-in backup tool, or
+your own backup solution.
+
+The project XML file is indent-formatted, and is suitable for diff tools and version control since
+most of the file will stay static, although a timestamp is set in the meta section on line 2, and
+various meta data entries incremented, on each save.
+
+A full project file format specification is available under "More Documents".
+
+
+Project Documents
+=================
+
+All the project documents are saved in a subfolder of the main project folder named ``content``.
+Each document has a file handle based on a 52 bit random number, represented as a hexadecimal
+string. The documents are saved with a filename assembled from this handle and the file extension
+``.nwd``.
+
+If you wish to find the file system location of a document in the project, you can either look it
+up in the project XML file, select **Show File Details** from the **Document** menu when having the
+document open in the editor, or look in the ``ToC.txt`` file in the root of the project folder. The
+``ToC.txt`` file has a list of all documents in the project, referenced by their label, and where
+they are saved.
+
+The reason for this cryptic file naming is to avoid issues with file naming conventions and
+restrictions on different operating systems, and also to have a file name that does not depend on
+what you name the document within the project, or changes it to. This is particularly useful when
+using a versioning system.
+
+Each document file contains a plain text version of the text from the editor. The file can in
+principle be edited in any text editor, and is suitable for diffing and version control if so
+desired. Just make sure the file remains in utf-8 encoding, otherwise unicode characters may
+become mangled when the file is opened in novelWriter again.
+
+Editing these files is generally not recommended. The reason for this is that the index will not be
+automatically updated when doing so, which means novelWriter doesn't know you've altered the file.
+If you *do* edit a file in this manner, you should rebuild the index when you next open the project
+in novelWriter.
+
+The first lines of the file may contain some meta data starting with the characters ``%%~``. These
+lines are mainly there to restore some information if the file is lost from the main project file,
+and the information may be helpful if you do open the file in an external editor as it contains the
+document label and the document class and layout. The lines can be deleted without any consequences
+to the rest of the content of the file, and will be added back the next time the document is saved
+in novelWriter.
+
+
+The File Saving Process
+-----------------------
+
+When saving the project file, or any of the documents, the data is first saved to a temporary file.
+If successful, the old data file is then removed, and the temporary file replaces it. This ensures
+that the previously saved data is only replaced when the new data has been successfully saved to
+the storage medium.
+
+
+Project Meta Data
+=================
+
+The project folder contains a subfolder named ``meta``, containing a number of files. The meta
+folder contains semi-important files. That is, they can be lost with only minor impact to the
+project. All files in this folder are JSON or JSON Lines files, although some other files may
+remain from earlier versions of novelWriter as they haven't all been JSON files in the past.
+
+If you use version control software on your project, you can exclude this folder, although you may
+want to track the session log file and the custom words list.
+
+
+The Project Index
+-----------------
+
+Between writing sessions, the project index is saved in a JSON file in ``meta/index.json``.
+This file is not critical. If it is lost, it can be completely rebuilt from within novelWriter from
+the **Tools** menu.
+
+The index is maintained and updated whenever a document or note is saved in the editor. It contains
+all references and tags in documents and notes, as well as the location of all headers in the
+project, and the word counts within each header section.
+
+The integrity of the index is checked when the file is loaded. It is possible to corrupt the index
+if the file is manually edited and manipulated, so the check is important to avoid sudden crashes
+of novelWriter. If the file contains errors, novelWriter will automatically build it anew. If the
+check somehow fails and novelWriter keeps crashing, you can delete the file manually and rebuild
+the index. If this too fails, you have likely encountered a bug.
+
+
+Build Definitions
+-----------------
+
+The build definitions from the **Manuscript Build** tool are kept in the ``meta/builds.json`` file.
+If this file is lost, all custom build definitions are lost too.
+
+
+Cached GUI Options
+------------------
+
+A file named ``meta/options.json`` contains the latest state of various GUI buttons, switches,
+dialog window sizes, column sizes, etc, from the GUI. These are the GUI settings that are specific
+to the project. Global GUI settings are stored in the main config file.
+
+The file is not critical, but if it is lost, all such GUI options will revert back to their default
+settings.
+
+
+Custom Word List
+----------------
+
+A file named ``meta/userdict.json`` contains all the custom words you've added to the project for
+spell checking purposes. The content of the file can be edited from the **Tools** menu. If you lose
+this file, all your custom spell check words will be lost too.
+
+
+Session Stats
+-------------
+
+The writing progress is saved in the ``meta/sessions.jsonl`` file. This file records the length
+and word counts of each writing session on the given project. The file is used by the **Writing
+Statistics** tool. If this file is lost, the history it contains is also lost, but it has otherwise
+no impact on the project.
+
+Each session is recorded as a JSON object on a single line of the file. Each session record is
+appended tot he file.