Program.cs

using AngouriMath;
using ResistorSearch;
using Spectre.Console;
using System.Globalization;
using System.Text.RegularExpressions;
using static AngouriMath.Entity.Set;


const int minOhm = 1000;
const int maxOhm = 1000000;
const int maxResults = 200;





while (true) {
    try {
        AnsiConsole.MarkupLine("* Use [yellow]r1[/], [yellow]r2[/] and [yellow]v[/] in equality");
        AnsiConsole.MarkupLine("* Equality must have a [yellow]=[/] sign");
        AnsiConsole.MarkupLine("* The left and right parts of equality can be swapped, it does not matter");
        AnsiConsole.MarkupLine("* The case does not matter");
        AnsiConsole.WriteLine();
        AnsiConsole.MarkupLine("* Examples of formulas");
        AnsiConsole.MarkupLine("*   For MT3608: [green]v = 0.6 * (1 + (r1 / r2))[/]");
        AnsiConsole.MarkupLine("*   For TPS61088: [green]r1 = ((v - 1.204) * r2) / 1.204[/]");
        AnsiConsole.WriteLine();

        var formula = AnsiConsole.Prompt(
            new TextPrompt<string>("Formula: ")
            .PromptStyle("green")
            .Validate(formula => {
                formula = formula.ToLower().Replace(" ", "");
                string[] parts = formula.Split('=');

                // Check formula structure and balance
                if (parts.Length != 2) {
                    return ValidationResult.Error("[red]Formula must contain one '=' sign[/]");
                }

                // Extract and validate variable usage
                var leftVars = new HashSet<string> { "r1", "r2", "v" }.Where(v => parts[0].Contains(v)).ToHashSet();
                var rightVars = new HashSet<string> { "r1", "r2", "v" }.Where(v => parts[1].Contains(v)).ToHashSet();

                if (!(leftVars.Count == 1 && rightVars.Count == 2) && !(leftVars.Count == 2 && rightVars.Count == 1)) {
                    return ValidationResult.Error("[red]One side must contain one variable and the other side two variables[/]");
                }

                try {
                    (var main, var equality) = Solver.NormalizeFormula(formula);
                    Entity fullFormula = $"{equality} = {main}";
                    fullFormula.Solve("v");
                } catch (Exception ex) {
                    return ValidationResult.Error($"[red]{ex.Message}[/]");
                }
 
                return ValidationResult.Success();
            })
        );

        var voltage = AnsiConsole.Prompt(
            new TextPrompt<double>("Out voltage: ")
            .PromptStyle("green")
            .Validate(voltage => {
                return double.TryParse(voltage.ToString(), NumberStyles.Any, CultureInfo.InvariantCulture, out _)
                            ? ValidationResult.Success()
                            : ValidationResult.Error("[red]That is not a valid number[/]");
            })
        );

        var eSeries = AnsiConsole.Prompt(
            new TextPrompt<int>("E-series (3, 6, 12, 24, 48, 96, 192): ")
            .PromptStyle("green")
            .Validate(eSeries => {
                var validNumbers = new HashSet<int> { 3, 6, 12, 24, 48, 96, 192 };
                return validNumbers.Contains(eSeries)
                    ? ValidationResult.Success()
                    : ValidationResult.Error("[red]Number must be one of the specified values[/]");
            })
        );

        var resistorValues = eSeries switch {
            3 => ResistorValues.E3,
            6 => ResistorValues.E6,
            12 => ResistorValues.E12,
            24 => ResistorValues.E24,
            48 => ResistorValues.E48,
            96 => ResistorValues.E96,
            192 => ResistorValues.E192,
            _ => ResistorValues.E24
        };

        var solver = new Solver() {
            resistorValues = ResistorValues.GetRange(resistorValues, minOhm, maxOhm)
        };


        AnsiConsole.Clear();

        AnsiConsole.MarkupLine("[yellow]Search...[/]");

        var result = solver.SolveAll(formula, voltage);

        AnsiConsole.Clear();

        Utility.WriteInfo(result, maxResults);

    } catch (Exception ex) {
        AnsiConsole.Clear();
        AnsiConsole.MarkupLine($"[red]{ex.Message}[/]");
    }


    AnsiConsole.WriteLine();
    AnsiConsole.MarkupLine("[green]Press any key to restart[/]");

    Console.ReadKey();

    AnsiConsole.Clear();
}