using System.Diagnostics;

namespace w4c_workflows.Services.Execution;

/// <summary>
/// Runs a language whose program is a single file executed by an interpreter
/// (shell → sh, python → python3, javascript → node). Input is written to stdin
/// as JSON; output follows the <see cref="ExecutionHelpers"/> stdout contract.
/// </summary>
public class SubprocessScriptExecutor : IScriptExecutor
{
    private readonly string _language;
    private readonly string _executable;
    private readonly TimeSpan _timeout;

    public SubprocessScriptExecutor(string language, string executable, IConfiguration config)
    {
        _language = language;
        _executable = executable;
        _timeout = TimeSpan.FromSeconds(ParseInt(config["Workflows:TaskTimeoutSeconds"], 60));
    }

    public string Language => _language;

    public bool IsAvailable() => ProcessRunner.FindInPath(_executable) != null;

    public async Task<ExecutionResult> ExecuteAsync(TaskInvocation invocation, CancellationToken ct)
    {
        var sw = Stopwatch.StartNew();
        try
        {
            var workingDir = ExecutionHelpers.ResolveWorkingDir(invocation);
            var entryPath = Path.Combine(workingDir, invocation.EntryFile);

            var output = await ProcessRunner.RunAsync(
                _executable,
                new[] { entryPath },
                workingDir,
                ExecutionHelpers.BuildEnvironment(invocation),
                invocation.Input,
                _timeout,
                ct);

            return ExecutionHelpers.ToResult(output, sw.Elapsed);
        }
        catch (Exception ex)
        {
            sw.Stop();
            return new ExecutionResult(false, -1, string.Empty, string.Empty, null, ex.Message, sw.Elapsed);
        }
    }

    private static int ParseInt(string? text, int fallback)
        => int.TryParse(text, out var value) && value > 0 ? value : fallback;
}