using NUnit.Framework;

using MultiversalDiplomacy.Script;

namespace MultiversalDiplomacyTests;

public class ReplDriver(IScriptHandler initialHandler, bool echo = false)
{
    public IScriptHandler? Handler { get; private set; } = initialHandler;

    private string? LastInput { get; set; } = "";

    /// <summary>
    /// Whether to print the inputs as they are executed. This is primarily a debugging aid.
    /// </summary>
    bool Echo { get; } = echo;

    /// <summary>
    /// Input a multiline string into the repl. Call <see cref="AssertReady"/> or <see cref="AssertClosed"/> at the end so the
    /// statement is valid.
    /// </summary>
    public ReplDriver this[string input] => ExecuteAll(input);

    public ReplDriver ExecuteAll(string multiline)
    {
        var lines = multiline.Split('\n', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
        return lines.Aggregate(this, (repl, line) => repl.Execute(line));
    }

    public ReplDriver Execute(string inputLine)
    {
        if (Handler is null) throw new AssertionException(
            $"Cannot execute \"{inputLine}\", handler quit. Last input was \"{LastInput}\"");
        if (Echo) Console.WriteLine($"{Handler.Prompt}{inputLine}");

        Handler = Handler.HandleInput(inputLine);
        LastInput = inputLine;

        return this;
    }

    public void AssertReady()
    {
        if (Handler is null) Assert.Fail($"Handler terminated after \"{LastInput}\"");
    }

    public void AssertClosed()
    {
        if (Handler is not null) Assert.Fail($"Handler did not terminate after \"{LastInput}\"");
    }
}