QuantityParser.cs

// Licensed under MIT No Attribution, see LICENSE file at the root.
// Copyright 2013 Andreas Gullberg Larsen (andreas.larsen84@gmail.com). Maintained at https://github.com/angularsen/UnitsNet.

using System.Globalization;
using System.Linq;
using System.Text.RegularExpressions;

// ReSharper disable once CheckNamespace
namespace UnitsNet;

/// <summary>
///     A method signature for creating a quantity given a numeric value and a strongly typed unit, for example 1.0 and
///     <see cref="LengthUnit.Meter" />.
/// </summary>
/// <typeparam name="TQuantity">The type of quantity to create, such as <see cref="Length" />.</typeparam>
/// <typeparam name="TUnitType">
///     The type of unit enum that belongs to this quantity, such as <see cref="LengthUnit" /> for
///     <see cref="Length" />.
/// </typeparam>
public delegate TQuantity QuantityFromDelegate<out TQuantity, in TUnitType>(double value, TUnitType fromUnit)
    where TQuantity : IQuantity
    where TUnitType : struct, Enum;

/// <summary>
///     Parses quantities from strings, such as "1.2 kg" to <see cref="Length" /> or "100 cm" to <see cref="Mass" />.
/// </summary>
public class QuantityParser
{
    /// <summary>
    ///     Allow integer, floating point or exponential number formats.
    /// </summary>
    private const NumberStyles ParseNumberStyles = NumberStyles.Number | NumberStyles.Float | NumberStyles.AllowExponent;

    private readonly UnitParser _unitParser;
    
    /// <summary>
    ///     Initializes a new instance of the <see cref="QuantityParser" /> class using the specified
    ///     <see cref="UnitAbbreviationsCache" />.
    /// </summary>
    /// <param name="unitAbbreviationsCache">
    ///     The cache containing mappings of units to their abbreviations, used for parsing quantities.
    /// </param>
    public QuantityParser(UnitAbbreviationsCache unitAbbreviationsCache)
        : this(new UnitParser(unitAbbreviationsCache))
    {
    }

    /// <summary>
    ///     Initializes a new instance of the <see cref="QuantityParser" /> class using the specified <see cref="UnitParser" />.
    /// </summary>
    /// <param name="unitParser">
    ///     The unit parser to use for parsing units.
    /// </param>
    public QuantityParser(UnitParser unitParser)
    {
        _unitParser = unitParser ?? throw new ArgumentNullException(nameof(unitParser));
    }

    /// <summary>
    ///     The default instance of <see cref="QuantityParser" />, which uses the default
    ///     <see cref="UnitsNetSetup.UnitAbbreviations" /> unit abbreviations.
    /// </summary>
    public static QuantityParser Default
    {
        get => UnitsNetSetup.Default.QuantityParser;
    }

    /// <summary>
    ///     Parses a quantity from a string, such as "1.2 kg" to <see cref="Length" /> or "100 cm" to <see cref="Mass" />.
    /// </summary>
    /// <param name="str">The string to parse, such as "1.2 kg".</param>
    /// <param name="formatProvider">
    ///     The culture for looking up localized unit abbreviations for a language, and for parsing
    ///     the number formatted in this culture. Defaults to <see cref="CultureInfo.CurrentCulture" />.
    /// </param>
    /// <param name="fromDelegate">A function to create a quantity given a numeric value and a unit enum value.</param>
    /// <typeparam name="TQuantity">The type of quantity to create, such as <see cref="Length" />.</typeparam>
    /// <typeparam name="TUnitType">
    ///     The type of unit enum that belongs to this quantity, such as <see cref="LengthUnit" /> for
    ///     <see cref="Length" />.
    /// </typeparam>
    /// <returns>The parsed quantity if successful.</returns>
    /// <exception cref="ArgumentNullException">The string was null.</exception>
    /// <exception cref="FormatException">Failed to parse quantity.</exception>
    public TQuantity Parse<TQuantity, TUnitType>(string str, IFormatProvider? formatProvider, QuantityFromDelegate<TQuantity, TUnitType> fromDelegate)
        where TQuantity : IQuantity
        where TUnitType : struct, Enum
    {
        if (str == null) throw new ArgumentNullException(nameof(str));
        str = str.Trim();

        Regex regex = CreateRegexForQuantity<TUnitType>(formatProvider);

        if (!TryExtractValueAndUnit(regex, str, out var valueString, out var unitString))
        {
            throw new FormatException(
                "Unable to parse quantity. Expected the form \"{value} {unit abbreviation}\", such as \"5.5 m\". The spacing is optional.")
            {
                Data = { ["input"] = str }
            };
        }

        return ParseWithRegex(valueString, unitString, fromDelegate, formatProvider);
    }

    /// <inheritdoc cref="Parse{TQuantity,TUnitType}" />
    internal IQuantity Parse(string str, IFormatProvider? formatProvider, QuantityInfo quantityInfo)
    {
        if (str == null) throw new ArgumentNullException(nameof(str));
        str = str.Trim();

        Regex regex = CreateRegexForQuantity(quantityInfo.UnitType, formatProvider);

        if (!TryExtractValueAndUnit(regex, str, out var valueString, out var unitString))
        {
            throw new FormatException(
                "Unable to parse quantity. Expected the form \"{value} {unit abbreviation}\", such as \"5.5 m\". The spacing is optional.")
            {
                Data = { ["input"] = str }
            };
        }

        return ParseWithRegex(valueString, unitString, quantityInfo.UnitInfos, formatProvider);
    }

    /// <summary>
    ///     Tries to parse a quantity from a string, such as "1.2 kg" to <see cref="Length" /> or "100 cm" to
    ///     <see cref="Mass" />.
    /// </summary>
    /// <param name="str">The string to parse, such as "1.2 kg".</param>
    /// <param name="formatProvider">
    ///     The culture for looking up localized unit abbreviations for a language, and for parsing
    ///     the number formatted in this culture. Defaults to <see cref="CultureInfo.CurrentCulture" />.
    /// </param>
    /// <param name="fromDelegate">A function to create a quantity given a numeric value and a unit enum value.</param>
    /// <param name="result">The parsed quantity if successful, otherwise null.</param>
    /// <typeparam name="TQuantity">The type of quantity to create, such as <see cref="Length" />.</typeparam>
    /// <typeparam name="TUnitType">
    ///     The type of unit enum that belongs to this quantity, such as <see cref="LengthUnit" /> for
    ///     <see cref="Length" />.
    /// </typeparam>
    /// <returns>True if successful.</returns>
    /// <exception cref="ArgumentNullException">The string was null.</exception>
    /// <exception cref="FormatException">Failed to parse quantity.</exception>
    public bool TryParse<TQuantity, TUnitType>(string? str, IFormatProvider? formatProvider, QuantityFromDelegate<TQuantity, TUnitType> fromDelegate,
        [NotNullWhen(true)] out TQuantity? result)
        where TQuantity : IQuantity
        where TUnitType : struct, Enum
    {
        result = default;

        if (string.IsNullOrWhiteSpace(str)) return false;
        str = str!.Trim(); // netstandard2.0 nullable quirk

        Regex regex = CreateRegexForQuantity<TUnitType>(formatProvider);

        return TryExtractValueAndUnit(regex, str, out var valueString, out var unitString) &&
               TryParseWithRegex(valueString, unitString, fromDelegate, formatProvider, out result);
    }

    /// <inheritdoc cref="TryParse{TQuantity,TUnitType}" />
    internal bool TryParse(string? str, IFormatProvider? formatProvider, QuantityInfo quantityInfo, [NotNullWhen(true)] out IQuantity? result)
    {
        result = null;

        if (string.IsNullOrWhiteSpace(str)) return false;
        str = str!.Trim(); // netstandard2.0 nullable quirk

        Regex regex = CreateRegexForQuantity(quantityInfo.UnitType, formatProvider);

        return TryExtractValueAndUnit(regex, str, out var valueString, out var unitString) &&
               TryParseWithRegex(valueString, unitString, quantityInfo.UnitInfos, formatProvider, out result);
    }

    internal string CreateRegexPatternForUnit<TUnitType>(TUnitType unit, IFormatProvider? formatProvider, bool matchEntireString = true)
        where TUnitType : struct, Enum
    {
        IReadOnlyList<string> unitAbbreviations = _unitParser.Abbreviations.GetUnitAbbreviations(unit, formatProvider);
        var pattern = GetRegexPatternForUnitAbbreviations(unitAbbreviations);
        return matchEntireString ? $"^{pattern}$" : pattern;
    }

    private static string GetRegexPatternForUnitAbbreviations(IEnumerable<string> abbreviations)
    {
        var orderedAbbreviations = abbreviations
            .OrderByDescending(s => s.Length) // Important to order by length -- if "m" is before "mm" and the input is "mm", it will match just "m"
            .Select(Regex.Escape) // Escape special regex characters
            .ToArray();

        var abbreviationsPiped = $"{string.Join("|", orderedAbbreviations)}";
        return $@"(?<value>.*?)\s?(?<unit>{abbreviationsPiped})";
    }

    /// <summary>
    ///     Parse a string given a particular regular expression.
    /// </summary>
    /// <exception cref="UnitsNetException">Error parsing string.</exception>
    private TQuantity ParseWithRegex<TQuantity, TUnitType>(string valueString, string unitString, QuantityFromDelegate<TQuantity, TUnitType> fromDelegate,
        IFormatProvider? formatProvider)
        where TQuantity : IQuantity
        where TUnitType : struct, Enum
    {
        var value = double.Parse(valueString, ParseNumberStyles, formatProvider);
        TUnitType parsedUnit = _unitParser.Parse<TUnitType>(unitString, formatProvider);
        return fromDelegate(value, parsedUnit);
    }

    /// <summary>
    ///     Parse a string given a particular regular expression.
    /// </summary>
    /// <exception cref="UnitsNetException">Error parsing string.</exception>
    private IQuantity ParseWithRegex(string valueString, string unitString, IReadOnlyList<UnitInfo> units, IFormatProvider? formatProvider)
    {
        var value = double.Parse(valueString, ParseNumberStyles, formatProvider);
        UnitInfo unitInfo = _unitParser.Parse(unitString, units, formatProvider);
        return unitInfo.From(value);
    }

    /// <summary>
    ///     Parse a string given a particular regular expression.
    /// </summary>
    /// <exception cref="UnitsNetException">Error parsing string.</exception>
    private bool TryParseWithRegex<TQuantity, TUnitType>(string? valueString, string? unitString, QuantityFromDelegate<TQuantity, TUnitType> fromDelegate,
        IFormatProvider? formatProvider, [NotNullWhen(true)] out TQuantity? result)
        where TQuantity : IQuantity
        where TUnitType : struct, Enum
    {
        result = default;

        if (!double.TryParse(valueString, ParseNumberStyles, formatProvider, out var value))
        {
            return false;
        }

        if (!_unitParser.TryParse(unitString, formatProvider, out TUnitType parsedUnit))
        {
            return false;
        }

        result = fromDelegate(value, parsedUnit);
        return true;
    }

    /// <summary>
    ///     Parse a string given a particular regular expression.
    /// </summary>
    /// <exception cref="UnitsNetException">Error parsing string.</exception>
    private bool TryParseWithRegex(string? valueString, string? unitString, IReadOnlyList<UnitInfo> units, IFormatProvider? formatProvider,
        [NotNullWhen(true)] out IQuantity? result)
    {
        result = null;

        if (!double.TryParse(valueString, ParseNumberStyles, formatProvider, out var value))
        {
            return false;
        }

        if (!_unitParser.TryParse(unitString, units, formatProvider, out UnitInfo? parsedUnit))
        {
            return false;
        }

        result = parsedUnit.From(value);
        return true;
    }

    private static bool TryExtractValueAndUnit(Regex regex, string str, [NotNullWhen(true)] out string? valueString, [NotNullWhen(true)] out string? unitString)
    {
        Match match = regex.Match(str);

        // the regex coming in contains all allowed units as strings.
        // That means if the unit in str is not formatted right
        // the regex.Match will either put str or string.empty into Groups[0] and Groups[1]
        // Therefore a mismatch can be detected by comparing the values of this two groups.
        if (match.Groups[0].Value == match.Groups[1].Value)
        {
            str = UnitParser.NormalizeUnitString(str);
            match = regex.Match(str);
        }

        GroupCollection groups = match.Groups;

        Group valueGroup = groups["value"];
        Group unitGroup = groups["unit"];
        if (!valueGroup.Success || !unitGroup.Success)
        {
            valueString = null;
            unitString = null;
            return false;
        }

        valueString = valueGroup.Value;
        unitString = unitGroup.Value;
        return true;
    }

    private string CreateRegexPatternForQuantity(Type unitType, IFormatProvider? formatProvider)
    {
        IReadOnlyList<string> unitAbbreviations = _unitParser.Abbreviations.GetAllUnitAbbreviationsForQuantity(unitType, formatProvider);
        var pattern = GetRegexPatternForUnitAbbreviations(unitAbbreviations);

        // Match entire string exactly
        return $"^{pattern}$";
    }

    private Regex CreateRegexForQuantity(Type unitType, IFormatProvider? formatProvider)
    {
        var pattern = CreateRegexPatternForQuantity(unitType, formatProvider);
        return new Regex(pattern, RegexOptions.Singleline | RegexOptions.IgnoreCase);
    }

    private Regex CreateRegexForQuantity<TUnitType>(IFormatProvider? formatProvider)
        where TUnitType : struct, Enum
    {
        return CreateRegexForQuantity(typeof(TUnitType), formatProvider);
    }
}