From a34702dc6c0a8180b01bea813cd5bde0bfa72acf Mon Sep 17 00:00:00 2001
From: Lynne <lynne@bune.city>
Date: Wed, 14 Oct 2020 03:47:33 +1000
Subject: [PATCH] implemented encoding format c, and support for customer
 information 3. i would do 2 as well but it's 0347. next up, unit testing for
 the first time in my stinchin life

---
 .../.idea.auspostcode.dir/.idea/workspace.xml |  93 ++++++------
 Barcode.cs                                    | 141 +++++++++++++-----
 Program.cs                                    |   7 +-
 3 files changed, 161 insertions(+), 80 deletions(-)

diff --git a/.idea/.idea.auspostcode.dir/.idea/workspace.xml b/.idea/.idea.auspostcode.dir/.idea/workspace.xml
index 610d25d..2f12f83 100644
--- a/.idea/.idea.auspostcode.dir/.idea/workspace.xml
+++ b/.idea/.idea.auspostcode.dir/.idea/workspace.xml
@@ -22,7 +22,6 @@
     <list default="true" id="373c5ee6-3f10-450b-8af6-fc4dd99290b0" name="Default Changelist" comment="initial commit, as they say">
       <change beforePath="$PROJECT_DIR$/.idea/.idea.auspostcode.dir/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/.idea.auspostcode.dir/.idea/workspace.xml" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/Barcode.cs" beforeDir="false" afterPath="$PROJECT_DIR$/Barcode.cs" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/BaseConversion.cs" beforeDir="false" afterPath="$PROJECT_DIR$/BaseConversion.cs" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/Program.cs" beforeDir="false" afterPath="$PROJECT_DIR$/Program.cs" afterDir="false" />
     </list>
     <option name="SHOW_DIALOG" value="false" />
@@ -45,6 +44,7 @@
         <option value="$PROJECT_DIR$/BarcodeVersion.cs" />
         <option value="$PROJECT_DIR$/.gitignore" />
         <option value="$PROJECT_DIR$/BaseConversion.cs" />
+        <option value="$APPLICATION_CONFIG_DIR$/scratches/scratch.txt" />
         <option value="$PROJECT_DIR$/Program.cs" />
         <option value="$PROJECT_DIR$/Barcode.cs" />
       </list>
@@ -65,6 +65,7 @@
     <property name="WebServerToolWindowFactoryState" value="false" />
     <property name="XThreadsFramesViewSplitterKey" value="0.7161862" />
     <property name="add_unversioned_files" value="true" />
+    <property name="com.intellij.ide.scratch.LRUPopupBuilder$1/New Scratch File" value="TEXT" />
     <property name="settings.editor.selected.configurable" value="preferences.sourceCode.C#" />
     <property name="vue.rearranger.settings.migration" value="true" />
   </component>
@@ -96,7 +97,7 @@
       <option name="number" value="Default" />
       <option name="presentableId" value="Default" />
       <updated>1602593942454</updated>
-      <workItem from="1602593947835" duration="13843000" />
+      <workItem from="1602593947835" duration="17273000" />
     </task>
     <task id="LOCAL-00001" summary="initial commit, as they say">
       <created>1602597326777</created>
@@ -148,86 +149,86 @@
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
     <state x="727" y="366" width="424" height="478" key="FileChooserDialogImpl/0.0.1920.1054@0.0.1920.1054" timestamp="1602597073977" />
-    <state width="1878" height="374" key="GridCell.Tab.0.bottom" timestamp="1602607646431">
+    <state width="1878" height="374" key="GridCell.Tab.0.bottom" timestamp="1602610374478">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.0.bottom/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646431" />
-    <state width="1878" height="374" key="GridCell.Tab.0.center" timestamp="1602607646431">
+    <state width="1878" height="374" key="GridCell.Tab.0.bottom/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374478" />
+    <state width="1878" height="374" key="GridCell.Tab.0.center" timestamp="1602610374477">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.0.center/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646431" />
-    <state width="1878" height="374" key="GridCell.Tab.0.left" timestamp="1602607646431">
+    <state width="1878" height="374" key="GridCell.Tab.0.center/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374477" />
+    <state width="1878" height="374" key="GridCell.Tab.0.left" timestamp="1602610374476">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.0.left/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646431" />
-    <state width="1878" height="374" key="GridCell.Tab.0.right" timestamp="1602607646431">
+    <state width="1878" height="374" key="GridCell.Tab.0.left/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374476" />
+    <state width="1878" height="374" key="GridCell.Tab.0.right" timestamp="1602610374478">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.0.right/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646431" />
-    <state width="1878" height="374" key="GridCell.Tab.1.bottom" timestamp="1602607646287">
+    <state width="1878" height="374" key="GridCell.Tab.0.right/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374478" />
+    <state width="1878" height="374" key="GridCell.Tab.1.bottom" timestamp="1602610374479">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.1.bottom/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646287" />
-    <state width="1878" height="374" key="GridCell.Tab.1.center" timestamp="1602607646287">
+    <state width="1878" height="374" key="GridCell.Tab.1.bottom/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374479" />
+    <state width="1878" height="374" key="GridCell.Tab.1.center" timestamp="1602610374479">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.1.center/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646287" />
-    <state width="1878" height="374" key="GridCell.Tab.1.left" timestamp="1602607646287">
+    <state width="1878" height="374" key="GridCell.Tab.1.center/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374479" />
+    <state width="1878" height="374" key="GridCell.Tab.1.left" timestamp="1602610374478">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.1.left/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646287" />
-    <state width="1878" height="374" key="GridCell.Tab.1.right" timestamp="1602607646287">
+    <state width="1878" height="374" key="GridCell.Tab.1.left/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374478" />
+    <state width="1878" height="374" key="GridCell.Tab.1.right" timestamp="1602610374479">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.1.right/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646287" />
-    <state width="1878" height="374" key="GridCell.Tab.2.bottom" timestamp="1602607646288">
+    <state width="1878" height="374" key="GridCell.Tab.1.right/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374479" />
+    <state width="1878" height="374" key="GridCell.Tab.2.bottom" timestamp="1602610374481">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.2.bottom/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646288" />
-    <state width="1878" height="374" key="GridCell.Tab.2.center" timestamp="1602607646287">
+    <state width="1878" height="374" key="GridCell.Tab.2.bottom/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374481" />
+    <state width="1878" height="374" key="GridCell.Tab.2.center" timestamp="1602610374480">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.2.center/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646287" />
-    <state width="1878" height="374" key="GridCell.Tab.2.left" timestamp="1602607646287">
+    <state width="1878" height="374" key="GridCell.Tab.2.center/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374480" />
+    <state width="1878" height="374" key="GridCell.Tab.2.left" timestamp="1602610374480">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.2.left/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646287" />
-    <state width="1878" height="374" key="GridCell.Tab.2.right" timestamp="1602607646287">
+    <state width="1878" height="374" key="GridCell.Tab.2.left/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374480" />
+    <state width="1878" height="374" key="GridCell.Tab.2.right" timestamp="1602610374480">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.2.right/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646287" />
-    <state width="1878" height="374" key="GridCell.Tab.3.bottom" timestamp="1602607646288">
+    <state width="1878" height="374" key="GridCell.Tab.2.right/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374480" />
+    <state width="1878" height="374" key="GridCell.Tab.3.bottom" timestamp="1602610374482">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.3.bottom/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646288" />
-    <state width="1878" height="374" key="GridCell.Tab.3.center" timestamp="1602607646288">
+    <state width="1878" height="374" key="GridCell.Tab.3.bottom/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374482" />
+    <state width="1878" height="374" key="GridCell.Tab.3.center" timestamp="1602610374482">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.3.center/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646288" />
-    <state width="1878" height="374" key="GridCell.Tab.3.left" timestamp="1602607646288">
+    <state width="1878" height="374" key="GridCell.Tab.3.center/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374482" />
+    <state width="1878" height="374" key="GridCell.Tab.3.left" timestamp="1602610374481">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.3.left/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646288" />
-    <state width="1878" height="374" key="GridCell.Tab.3.right" timestamp="1602607646288">
+    <state width="1878" height="374" key="GridCell.Tab.3.left/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374481" />
+    <state width="1878" height="374" key="GridCell.Tab.3.right" timestamp="1602610374482">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.3.right/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646288" />
-    <state width="1878" height="374" key="GridCell.Tab.4.bottom" timestamp="1602607646289">
+    <state width="1878" height="374" key="GridCell.Tab.3.right/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374482" />
+    <state width="1878" height="374" key="GridCell.Tab.4.bottom" timestamp="1602610374484">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.4.bottom/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646289" />
-    <state width="1878" height="374" key="GridCell.Tab.4.center" timestamp="1602607646288">
+    <state width="1878" height="374" key="GridCell.Tab.4.bottom/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374484" />
+    <state width="1878" height="374" key="GridCell.Tab.4.center" timestamp="1602610374483">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.4.center/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646288" />
-    <state width="1878" height="374" key="GridCell.Tab.4.left" timestamp="1602607646288">
+    <state width="1878" height="374" key="GridCell.Tab.4.center/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374483" />
+    <state width="1878" height="374" key="GridCell.Tab.4.left" timestamp="1602610374483">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.4.left/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646288" />
-    <state width="1878" height="374" key="GridCell.Tab.4.right" timestamp="1602607646289">
+    <state width="1878" height="374" key="GridCell.Tab.4.left/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374483" />
+    <state width="1878" height="374" key="GridCell.Tab.4.right" timestamp="1602610374484">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state width="1878" height="374" key="GridCell.Tab.4.right/0.0.1920.1054@0.0.1920.1054" timestamp="1602607646289" />
+    <state width="1878" height="374" key="GridCell.Tab.4.right/0.0.1920.1054@0.0.1920.1054" timestamp="1602610374484" />
     <state x="738" y="92" key="SettingsEditor" timestamp="1602603890848">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
@@ -240,6 +241,10 @@
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
     <state x="100" y="99" width="1720" height="855" key="com.intellij.history.integration.ui.views.DirectoryHistoryDialog/0.0.1920.1054@0.0.1920.1054" timestamp="1602597391150" />
+    <state x="482" y="127" width="945" height="793" key="com.intellij.openapi.editor.actions.MultiplePasteAction$ClipboardContentChooser" timestamp="1602607983699">
+      <screen x="0" y="0" width="1920" height="1054" />
+    </state>
+    <state x="482" y="127" width="945" height="793" key="com.intellij.openapi.editor.actions.MultiplePasteAction$ClipboardContentChooser/0.0.1920.1054@0.0.1920.1054" timestamp="1602607983699" />
     <state x="623" y="270" width="673" height="512" key="find.popup" timestamp="1602599001638">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
@@ -248,9 +253,9 @@
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
     <state x="440" y="285" width="1009" height="647" key="org.intellij.images.editor.actions.BackgroundImageDialog/0.0.1920.1054@0.0.1920.1054" timestamp="1602598923528" />
-    <state x="623" y="231" width="672" height="678" key="search.everywhere.popup" timestamp="1602599024210">
+    <state x="623" y="231" width="672" height="678" key="search.everywhere.popup" timestamp="1602608996147">
       <screen x="0" y="0" width="1920" height="1054" />
     </state>
-    <state x="623" y="231" width="672" height="678" key="search.everywhere.popup/0.0.1920.1054@0.0.1920.1054" timestamp="1602599024210" />
+    <state x="623" y="231" width="672" height="678" key="search.everywhere.popup/0.0.1920.1054@0.0.1920.1054" timestamp="1602608996147" />
   </component>
 </project>
\ No newline at end of file
diff --git a/Barcode.cs b/Barcode.cs
index f3d65e7..5c23321 100644
--- a/Barcode.cs
+++ b/Barcode.cs
@@ -5,34 +5,6 @@ using System.Text.RegularExpressions;
 
 namespace AusPostCode {
 	public class Barcode {
-		private readonly struct BarcodeFragment {
-			public EncodingFormat TypicalFormat { get; }
-			public int Length { get;}
-			public int Offset { get; }
-
-			public BarcodeFragment(EncodingFormat typicalFormat, int length, int offset) {
-				TypicalFormat = typicalFormat;
-				Length = length;
-				Offset = offset;
-			}
-		}
-
-		private readonly Dictionary<string, BarcodeFragment> _fragments = new Dictionary<string, BarcodeFragment> {
-			["FormatControlCode"] = new BarcodeFragment(EncodingFormat.N, 4, 2),
-			["SortingCode"] = new BarcodeFragment(EncodingFormat.N, 16, 6),
-			["CustomerInformation2"] = new BarcodeFragment(EncodingFormat.C, 16, 22),
-			["CustomerInformation3"] = new BarcodeFragment(EncodingFormat.C, 31, 22),
-			["ErrorCorrection"] = new BarcodeFragment(EncodingFormat.BarToDecimal, 12, - 16),
-		};
-
-		private enum EncodingFormat {
-			N,
-			C,
-			BarToDecimal,
-		}
-
-		private int _formatCode;
-
 		private readonly Dictionary<int, string> _formatTable = new Dictionary<int, string> {
 			[0] = "Null Customer Barcode",
 			[11] = "Standard Customer Barcode",
@@ -44,6 +16,20 @@ namespace AusPostCode {
 			[77] = "International Business Reply Paid",
 		};
 
+		private readonly Dictionary<string, BarcodeFragment> _fragments = new Dictionary<string, BarcodeFragment> {
+			["FormatControlCode"] = new BarcodeFragment(EncodingFormat.N, 4, 2),
+			["SortingCode"] = new BarcodeFragment(EncodingFormat.N, 16, 6),
+			["CustomerInformation2"] = new BarcodeFragment(EncodingFormat.C, 16, 22),
+			["CustomerInformation3"] = new BarcodeFragment(EncodingFormat.C, 30, 22),
+			["ErrorCorrection"] = new BarcodeFragment(EncodingFormat.BarToDecimal, 12, -16),
+		};
+
+		// TODO: make these consts
+		private readonly char[] _lower = "abcdefghijklmnopqrstuvwxyz".ToCharArray();
+		private readonly char[] _upper = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray();
+
+		private readonly int _formatCode;
+
 		public Barcode(string code) {
 			Code = code;
 			// - check for start and end bars
@@ -68,20 +54,23 @@ namespace AusPostCode {
 			// process Customer Information, if necessary
 			// TODO: actually do this, and get a code to test it on. also, ensure that customer codes are the right length
 			if (_formatCode == 59) {
-				Console.WriteLine("This code has a Customer Information field, but I don't know how to process that yet 0uo");
-			} else if (_formatCode == 62) {
-				Console.WriteLine("This code has a Customer Information field, but I don't know how to process that yet 0uo");
+				Console.WriteLine("This code has a Customer Information 2 field, but I don't know how to process that yet 0uo");
+			}
+			else if (_formatCode == 62) {
+				Console.WriteLine($"Customer info: [{GetFragment(_fragments["CustomerInformation3"])}]");
 			}
 
 			// process Reed-Solomon Error Correction Bars
 			// TODO: actually validate the barcode
 			Console.WriteLine(BaseConversion.FromBase(GetFragment(_fragments["ErrorCorrection"]), 64));
-
 		}
 
 		public int SortingCode { get; set; }
 		public int CustomerInformation { get; set; }
-		public string Format => _formatTable.ContainsKey(_formatCode) ? _formatTable[_formatCode] : $"Unknown ({_formatCode})";
+
+		public string Format =>
+			_formatTable.ContainsKey(_formatCode) ? _formatTable[_formatCode] : $"Unknown ({_formatCode})";
+
 		private List<string> Warnings { get; } = new List<string>();
 		private string Code { get; }
 
@@ -113,14 +102,79 @@ namespace AusPostCode {
 						}
 						else if (chunk.Contains("3")) {
 							// not a ternary number
-							throw new ArgumentException($"{chunk} is not a valid identifier for format {data.ToString()}.");
+							throw new ArgumentException($"{chunk} is not a valid identifier for format {data}.");
 						}
 						else {
 							sb.Append(BaseConversion.FromBase(chunk, 3));
 						}
+
 						break;
 
 					case EncodingFormat.C:
+						// table C is a bit of a doozy.
+						// firstly, check for 222, which is zero.
+						if (chunk == "222") {
+							sb.Append("0");
+						}
+						// if it's any other valid ternary number (only digits 0,1,2), it's a capital letter.
+						else if (!chunk.Contains("3")) {
+							sb.Append(_upper[BaseConversion.FromBase(chunk, 3)]);
+						}
+						// if it starts with a 3, but is otherwise a valid ternary number, it's a digit from 1 through 9.
+						// the sequence is 300, 301, 302, 310, 311...
+						// because it starts at 0 (after stripping the leading 3), we add 1.
+						else if (chunk.StartsWith("3") && !chunk.Substring(1).Contains("3")) {
+							sb.Append(BaseConversion.FromBase(chunk.Substring(1), 3) + 1);
+						}
+						// 003 is space.
+						else if (chunk == "003") {
+							sb.Append(" ");
+						}
+						// 013 is hash.
+						else if (chunk == "013") {
+							sb.Append("#");
+						}
+						// and finally, anything that doesn't fall into any of the above is a lowercase letter.
+						else {
+							// this is by far the most difficult part when it comes to parsing the barcode formats (so far).
+							// i'm really bad at maths, and it took me a while to get this function into something (semi) readable
+							//  down from the multi-cell spreadsheet formula mess that it started out as.
+							// i think this is the first time in my life i've ever done maths in a base other than 10, unless you
+							//  count converting time differences.
+
+							// starting from 023, the lowercase numbers are expressed by a cyclical pattern.
+							// each "cycle" lasts for seven letters. let's use the letters "bcdefgh" as an example.
+							// b is 030 (12 in decimal). c follows at 031, d at 032, and e at 033. this is the first half of the cycle.
+							// during the second half of the cycle, letters are spaced *four* numbers apart,
+							//  instead of one number apart like before.
+							// this means that e (033q == 15d) is *not* followed by f at 100q (16d), but at 103q (19d).
+							// g is found at 113q (23d), and then h is found at 123q (27d).
+							// i follows at 130q (28d), and the cycle repeats.
+							// the cycle resets at multiples of 16, which is very useful.
+
+							// the letters start at 11d, so we subtract 11 to start from zero instead.
+							var x = BaseConversion.FromBase(chunk, 4) - 11;
+
+							// you can tell how many times the cycle has looped by counting how many times 16 divides into the chunk.
+							// because the cycle is seven steps long, we should add 7 for every time 16 goes into the chunk.
+							// additionally, if we add 10 to x (and therefore making it effectively (chunk - 1)),
+							//  we can mod it with 16 to get the repeating sequence '10, 11, 12, 13, 14, 2, 6'.
+							// we can use max() to replace the 2 with a 5, giving us '10, 11, 12, 13, 14, 5, 6'.
+							// if we only keep the units digit (by doing modulo 10), we get '0, 1, 2, 3, 4, 5, 6'.
+							// now we have a way to tell how many times we've completed the cycle (how many 16s go into the chunk),
+							//  and a way to tell what step we're on in the cycle, we can combine these two pieces of knowledge to
+							//  turn the messy letter codes into a set of integers from 0 to 25, increasing linearly by 1.
+							// in other words, when we're given a chunk like "032", we can tell that it refers to the 4th letter of
+							//  the alphabet, and return that.
+
+							// i know the way this function is written is slightly unwieldy, but at the very least, it's better than
+							// wolfram alpha's suggested alternative form:
+							// -10 floor(1/10 max(5, x - 16 floor((x + 10)/16) + 10)) + max(5, -16 floor((x + 10)/16) + x + 10) + 7 floor(x/16)
+							// i guess wolfram really doesn't like the mod function? 0uo
+
+							sb.Append(_lower[x / 16 * 7 + Math.Max((x + 10) % 16, 5) % 10]);
+						}
+
 						break;
 
 					case EncodingFormat.BarToDecimal:
@@ -167,6 +221,7 @@ namespace AusPostCode {
 						else {
 							sb.Append(BaseConversion.FromBase(chunk, 3));
 						}
+
 						break;
 
 					case EncodingFormat.C:
@@ -182,5 +237,23 @@ namespace AusPostCode {
 
 			return sb.ToString();
 		}
+
+		private readonly struct BarcodeFragment {
+			public EncodingFormat TypicalFormat { get; }
+			public int Length { get; }
+			public int Offset { get; }
+
+			public BarcodeFragment(EncodingFormat typicalFormat, int length, int offset) {
+				TypicalFormat = typicalFormat;
+				Length = length;
+				Offset = offset;
+			}
+		}
+
+		private enum EncodingFormat {
+			N,
+			C,
+			BarToDecimal,
+		}
 	}
 }
diff --git a/Program.cs b/Program.cs
index 83835fa..c97ee2c 100644
--- a/Program.cs
+++ b/Program.cs
@@ -29,9 +29,12 @@ namespace AusPostCode {
 			// - a filler bar of 3
 			// - a reed-solomon code of 001101103221 == 10826817
 			// - end bars
-			const string testCode = "1301012112011202120020300110110322113";
+			// const string testCode = "1301012112011202120020300110110322113";
 
-			var barcode = new Barcode(testCode);
+			// const string testCodeCustomer3 = "1320021211120120021201000001002300301302333333333333313133002021313";
+			const string testCodeCustomer3 = "1320021211120120021201003021130003120033203230023003313133002021313";
+
+			var barcode = new Barcode(testCodeCustomer3);
 		}
 
 		public class Options {