using MeterVault.Core.Normalization.Expressions;

namespace MeterVault.Core.Tests;

public sealed class ExpressionEvaluatorTests
{
    private static readonly Dictionary<string, double> Vars = new()
    {
        ["m1"] = 411,
        ["m2"] = 416,
    };

    [Theory]
    [InlineData("1 + 2 * 3", 7)]
    [InlineData("(1 + 2) * 3", 9)]
    [InlineData("-5", -5)]
    [InlineData("10 / 4", 2.5)]
    [InlineData("2 - 3 - 4", -5)]        // left-associative
    [InlineData("m1 - m2", -5)]
    [InlineData("m1 + m2", 827)]
    [InlineData("unknown + 1", 1)]        // unknown identifiers resolve to 0
    public void Evaluates_arithmetic(string expression, double expected)
    {
        var result = ExpressionEvaluator.Compile(expression).Evaluate(Vars);

        Assert.Equal(expected, result, 6);
    }

    [Theory]
    [InlineData("1 +")]
    [InlineData("(1 + 2")]
    [InlineData("1 2")]
    [InlineData("")]
    public void Rejects_malformed_expressions(string expression) =>
        Assert.ThrowsAny<Exception>(() => ExpressionEvaluator.Compile(expression));
}