Generate operators from unit relations defined in JSON

CodeGen/Generators/QuantityRelationsParser.cs

@@ -0,0 +1,195 @@
+// Licensed under MIT No Attribution, see LICENSE file at the root.
+// Copyright 2013 Andreas Gullberg Larsen ([email protected]). Maintained at https://github.com/angularsen/UnitsNet.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using CodeGen.Exceptions;
+using CodeGen.JsonTypes;
+using Newtonsoft.Json;
+
+namespace CodeGen.Generators
+{
+    /// <summary>
+    ///     Parses the JSON file that defines the relationships (operators) between quantities
+    ///     and applies them to the parsed quantity objects.
+    /// </summary>
+    internal static class QuantityRelationsParser
+    {
+        /// <summary>
+        ///     Parse and apply relations to quantities.
+        ///
+        ///     The relations are defined in UnitRelations.json
+        ///     Each defined relation can be applied multiple times to one or two quantities depending on the operator and the operands.
+        ///
+        ///     The format of a relation definition is "Quantity.Unit operator Quantity.Unit = Quantity.Unit" (See examples below).
+        ///     "double" can be used as a unitless operand.
+        ///     "1" can be used as the left operand to define inverse relations.
+        /// </summary>
+        /// <example>
+        /// [
+        ///     "Power.Watt = ElectricPotential.Volt * ElectricCurrent.Ampere",
+        ///     "Speed.MeterPerSecond = Length.Meter / Duration.Second",
+        ///     "ReciprocalLength.InverseMeter = 1 / Length.Meter"
+        /// ]
+        /// </example>
+        /// <param name="rootDir">Repository root directory.</param>
+        /// <param name="quantities">List of previously parsed Quantity objects.</param>
+        public static void ParseAndApplyRelations(string rootDir, Quantity[] quantities)
+        {
+            var quantityDictionary = quantities.ToDictionary(q => q.Name, q => q);
+
+            // Add double and 1 as pseudo-quantities to validate relations that use them.
+            var pseudoQuantity = new Quantity { Name = null!, Units = [new Unit { SingularName = null! }] };
+            quantityDictionary["double"] = pseudoQuantity with { Name = "double" };
+            quantityDictionary["1"] = pseudoQuantity with { Name = "1" };
+
+            var relations = ParseRelations(rootDir, quantityDictionary);
+
+            // Because multiplication is commutative, we can infer the other operand order.
+            relations.AddRange(relations
+                .Where(r => r.Operator is "*" or "inverse" && r.LeftQuantity != r.RightQuantity)
+                .Select(r => r with
+                {
+                    LeftQuantity = r.RightQuantity,
+                    LeftUnit = r.RightUnit,
+                    RightQuantity = r.LeftQuantity,
+                    RightUnit = r.LeftUnit,
+                })
+                .ToList());
+
+            // We can infer TimeSpan relations from Duration relations.
+            var timeSpanQuantity = pseudoQuantity with { Name = "TimeSpan" };
+            relations.AddRange(relations
+                .Where(r => r.LeftQuantity.Name is "Duration")
+                .Select(r => r with { LeftQuantity = timeSpanQuantity })
+                .ToList());
+            relations.AddRange(relations
+                .Where(r => r.RightQuantity.Name is "Duration")
+                .Select(r => r with { RightQuantity = timeSpanQuantity })
+                .ToList());
+
+            // Sort all relations to keep generated operators in a consistent order.
+            relations.Sort();
+
+            var duplicates = relations
+                .GroupBy(r => r.SortString)
+                .Where(g => g.Count() > 1)
+                .Select(g => g.Key)
+                .ToList();
+
+            if (duplicates.Any())
+            {
+                var list = string.Join("\n  ", duplicates);
+                throw new UnitsNetCodeGenException($"Duplicate inferred relations:\n  {list}");
+            }
+
+            foreach (var quantity in quantities)
+            {
+                var quantityRelations = new List<QuantityRelation>();
+
+                foreach (var relation in relations)
+                {
+                    if (relation.LeftQuantity == quantity)
+                    {
+                        // The left operand of a relation is responsible for generating the operator.
+                        quantityRelations.Add(relation);
+                    }
+                    else if (relation.RightQuantity == quantity && relation.LeftQuantity.Name is "double" or "TimeSpan")
+                    {
+                        // Because we cannot add generated operators to double or TimeSpan, we make the right operand responsible in this case.
+                        quantityRelations.Add(relation);
+                    }
+                }
+
+                quantity.Relations = quantityRelations.ToArray();
+            }
+        }
+
+        private static List<QuantityRelation> ParseRelations(string rootDir, IReadOnlyDictionary<string, Quantity> quantities)
+        {
+            var relationsFileName = Path.Combine(rootDir, "Common/UnitRelations.json");
+
+            try
+            {
+                var text = File.ReadAllText(relationsFileName);
+                var relationStrings = JsonConvert.DeserializeObject<SortedSet<string>>(text) ?? [];
+
+                var parsedRelations = relationStrings.Select(relationString => ParseRelation(relationString, quantities)).ToList();
+
+                // File parsed successfully, save it back to disk in the sorted state.
+                File.WriteAllText(relationsFileName, JsonConvert.SerializeObject(relationStrings, Formatting.Indented));
+
+                return parsedRelations;
+            }
+            catch (Exception e)
+            {
+                throw new UnitsNetCodeGenException($"Error parsing relations file: {relationsFileName}", e);
+            }
+        }
+
+        private static QuantityRelation ParseRelation(string relationString, IReadOnlyDictionary<string, Quantity> quantities)
+        {
+            var segments = relationString.Split(' ');
+
+            if (segments is not [_, "=", _, "*" or "/", _])
+            {
+                throw new Exception($"Invalid relation string: {relationString}");
+            }
+
+            var @operator = segments[3];
+            var left = segments[2].Split('.');
+            var right = segments[4].Split('.');
+            var result = segments[0].Split('.');
+
+            var leftQuantity = GetQuantity(left[0]);
+            var rightQuantity = GetQuantity(right[0]);
+            var resultQuantity = GetQuantity(result[0]);
+
+            var leftUnit = GetUnit(leftQuantity, left.ElementAtOrDefault(1));
+            var rightUnit = GetUnit(rightQuantity, right.ElementAtOrDefault(1));
+            var resultUnit = GetUnit(resultQuantity, result.ElementAtOrDefault(1));
+
+            if (leftQuantity.Name == "1")
+            {
+                @operator = "inverse";
+                leftQuantity = resultQuantity;
+                leftUnit = resultUnit;
+            }
+
+            return new QuantityRelation
+            {
+                Operator = @operator,
+                LeftQuantity = leftQuantity,
+                LeftUnit = leftUnit,
+                RightQuantity = rightQuantity,
+                RightUnit = rightUnit,
+                ResultQuantity = resultQuantity,
+                ResultUnit = resultUnit
+            };
+
+            Quantity GetQuantity(string quantityName)
+            {
+                if (!quantities.TryGetValue(quantityName, out var quantity))
+                {
+                    throw new Exception($"Undefined quantity {quantityName} in relation string: {relationString}");
+                }
+
+                return quantity;
+            }
+
+            Unit GetUnit(Quantity quantity, string? unitName)
+            {
+                try
+                {
+                    return quantity.Units.First(u => u.SingularName == unitName);
+                }
+                catch (InvalidOperationException)
+                {
+                    throw new Exception($"Undefined unit {unitName} in relation string: {relationString}");
+                }
+            }
+        }
+    }
+}

CodeGen/Generators/UnitsNetGen/QuantityGenerator.cs

@@ -39,8 +39,12 @@ public string Generate()
 using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
-using System.Linq;
-using System.Runtime.Serialization;
+using System.Linq;");
+            if (_quantity.Relations.Any(r => r.Operator is "*" or "/"))
+                Writer.WL(@"#if NET7_0_OR_GREATER
+using System.Numerics;
+#endif");
+            Writer.WL(@"using System.Runtime.Serialization;
 using UnitsNet.InternalHelpers;
 using UnitsNet.Units;
 
@@ -67,6 +71,35 @@ namespace UnitsNet
     public readonly partial struct {_quantity.Name} :
         {(_quantity.GenerateArithmetic ? "IArithmeticQuantity" : "IQuantity")}<{_quantity.Name}, {_unitEnumName}, {_quantity.ValueType}>,");
 
+            if (_quantity.Relations.Any(r => r.Operator is "*" or "/"))
+            {
+                Writer.WL(@$"
+#if NET7_0_OR_GREATER");
+                foreach (var relation in _quantity.Relations)
+                {
+                    if (relation.LeftQuantity == _quantity)
+                    {
+                        switch (relation.Operator)
+                        {
+                            case "*":
+                                Writer.W(@"
+        IMultiplyOperators");
+                                break;
+                            case "/":
+                                Writer.W(@"
+        IDivisionOperators");
+                                break;
+                            default:
+                                continue;
+                        }
+                        Writer.WL($"<{relation.LeftQuantity.Name}, {relation.RightQuantity.Name}, {relation.ResultQuantity.Name}>,");
+                    }
+                }
+
+                Writer.WL(@$"
+#endif");
+            }
+
             if (_quantity.ValueType == "decimal") Writer.WL(@$"
         IDecimalQuantity,");
 
@@ -100,6 +133,7 @@ namespace UnitsNet
             GenerateStaticFactoryMethods();
             GenerateStaticParseMethods();
             GenerateArithmeticOperators();
+            GenerateRelationalOperators();
             GenerateEqualityAndComparison();
             GenerateConversionMethods();
             GenerateToString();
@@ -690,6 +724,92 @@ private void GenerateLogarithmicArithmeticOperators()
 " );
         }
 
+        /// <summary>
+        ///     Generates operators that express relations between quantities as applied by <see cref="QuantityRelationsParser" />.
+        /// </summary>
+        private void GenerateRelationalOperators()
+        {
+            if (!_quantity.Relations.Any()) return;
+
+            Writer.WL($@"
+        #region Relational Operators
+");
+
+            foreach (QuantityRelation relation in _quantity.Relations)
+            {
+                if (relation.Operator == "inverse")
+                {
+                    Writer.WL($@"
+        /// <summary>Calculates the inverse of this quantity.</summary>
+        /// <returns>The corresponding inverse quantity, <see cref=""{relation.RightQuantity.Name}""/>.</returns>
+        public {relation.RightQuantity.Name} Inverse()
+        {{
+            return {relation.LeftUnit.PluralName} == 0.0 ? {relation.RightQuantity.Name}.Zero : {relation.RightQuantity.Name}.From{relation.RightUnit.PluralName}(1 / {relation.LeftUnit.PluralName});
+        }}
+");
+                }
+                else
+                {
+                    var leftParameter = relation.LeftQuantity.Name.ToCamelCase();
+                    var leftConversionProperty = relation.LeftUnit.PluralName;
+                    var rightParameter = relation.RightQuantity.Name.ToCamelCase();
+                    var rightConversionProperty = relation.RightUnit.PluralName;
+
+                    if (relation.LeftQuantity.Name is nameof(TimeSpan))
+                    {
+                        leftConversionProperty = "Total" + leftConversionProperty;
+                    }
+
+                    if (relation.RightQuantity.Name is nameof(TimeSpan))
+                    {
+                        rightConversionProperty = "Total" + rightConversionProperty;
+                    }
+
+                    if (leftParameter == rightParameter)
+                    {
+                        leftParameter = "left";
+                        rightParameter = "right";
+                    }
+
+                    var leftPart = $"{leftParameter}.{leftConversionProperty}";
+                    var rightPart = $"{rightParameter}.{rightConversionProperty}";
+
+                    if (leftParameter is "double")
+                    {
+                        leftParameter = leftPart = "value";
+                    }       
+
+                    if (rightParameter is "double")
+                    {
+                        rightParameter = rightPart = "value";
+                    }
+
+                    var leftCast = relation.LeftQuantity.ValueType is "decimal" ? "(double)" : string.Empty;
+                    var rightCast = relation.RightQuantity.ValueType is "decimal" ? "(double)" : string.Empty;
+
+                    var expression = $"{leftCast}{leftPart} {relation.Operator} {rightCast}{rightPart}";
+
+                    if (relation.ResultQuantity.Name is not ("double" or "decimal"))
+                    {
+                        expression = $"{relation.ResultQuantity.Name}.From{relation.ResultUnit.PluralName}({expression})";
+                    }
+
+                    Writer.WL($@"
+        /// <summary>Get <see cref=""{relation.ResultQuantity.Name}""/> from <see cref=""{relation.LeftQuantity.Name}""/> {relation.Operator} <see cref=""{relation.RightQuantity.Name}""/>.</summary>
+        public static {relation.ResultQuantity.Name} operator {relation.Operator}({relation.LeftQuantity.Name} {leftParameter}, {relation.RightQuantity.Name} {rightParameter})
+        {{
+            return {expression};
+        }}
+");
+                }
+            }
+
+            Writer.WL($@"
+
+        #endregion
+");
+        }
+
         private void GenerateEqualityAndComparison()
         {
             Writer.WL($@"

CodeGen/JsonTypes/Quantity.cs

@@ -5,7 +5,7 @@
 
 namespace CodeGen.JsonTypes
 {
-    internal class Quantity
+    internal record Quantity
     {
         // 0649 Field is never assigned to
 #pragma warning disable 0649
@@ -18,6 +18,7 @@ internal class Quantity
         public int LogarithmicScalingFactor = 1;
         public string Name = null!;
         public Unit[] Units = Array.Empty<Unit>();
+        public QuantityRelation[] Relations = Array.Empty<QuantityRelation>();
         public string? XmlDocRemarks;
         public string XmlDocSummary = null!;
         public string? ObsoleteText;