From 7ea42e5c2c12be997586362570881219a1055e56 Mon Sep 17 00:00:00 2001
From: Katharina Bogad <katharina@hacked.xyz>
Date: Fri, 11 Jun 2021 20:01:30 +0200
Subject: [PATCH] Grocycode: docs

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+Grocycode
+==========
+
+Grocycode is, in essence, a simple way to reference to arbitrary grocy entities.
+Each grocycode includes a magic, an entitiy identifier, an id and an ordered set of extra data.
+It is supported to be entered anywhere grocy expects one to read a barcode, but can also reference
+grocy-internal properties like specific stock entries, or specific batteries.
+
+Serialization
+----
+
+There are three mandatory parts in a grocycode:
+
+1. The magic `grcy`
+2. An entity identifer matching the regular expression `[a-z]+` (that is, lowercase english alphabet without any fancy accents, minimum length 1 character).
+3. An object identifer matching the regular expression `[0-9]+`
+
+Optionally, any number of further data without format restrictions besides not containing any double colons [0] may be appended.
+
+These parts are then linearly appended, seperated by a double colon `:`.
+
+Entity Identifers
+----
+
+Currently, there are three different entity types defined:
+
+- `p` for Products
+- `b` for Batteries
+- `c` for Chores
+
+Example
+----
+
+In this example, we encode a *Product* with ID *13*, which results in `grcy:p:13` when serialized.
+
+Product Grocycodes
+----
+
+Product Grocycodes extend the data format to include an optional stock id, thus may reference a specific stock entry directly.
+
+Example: `grcy:p:13:60bf8b5244b04`
+
+Battery Grocycodes
+----
+
+Currently, Battery Grocycodes do not define any extra fields.
+
+Chore Grocycodes
+----
+
+Currently, Chore Grocycodes do not define any extra fields.
+
+Visual Encoding
+----
+
+Grocy uses DataMatrix 2D Barcodes to encode grocycodes into a visual representation. In principle, there is no problem with using
+other encoding formats like QR codes; however DataMatrix uses less space for the same information and redundancy and is a bit
+easier read by 2D barcode scanners, especially on non-flat surfaces.
+
+You can pick up cheap-ish used scanners from ebay (about 45€ in germany). Make sure to set them to the correct keyboard emulation,
+so that the double colons get entered correctly.
+
+
+Notes
+---
+[0]: Obviously, it needs to be encoded into some usable visual representation and then read. So probably you only want to encode stuff that can be typed on a keyboard.
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