73 lines
2.6 KiB
C#
73 lines
2.6 KiB
C#
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using System.Text;
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using Elsa.Expressions.Helpers;
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using Elsa.Expressions.Models;
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using Elsa.Mediator.Contracts;
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using Elsa.Python.Contracts;
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using Elsa.Python.Models;
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using Elsa.Python.Notifications;
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using Python.Runtime;
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namespace Elsa.Python.Services;
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/// <summary>
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/// Evaluates Python expressions using IronPython.
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/// </summary>
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public class PythonNetPythonEvaluator : IPythonEvaluator
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{
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private const string ReturnVarName = "elsa_python_result_variable_name";
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private readonly INotificationSender _notificationSender;
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/// <summary>
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/// Initializes a new instance of the <see cref="PythonNetPythonEvaluator"/> class.
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/// </summary>
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public PythonNetPythonEvaluator(INotificationSender notificationSender)
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{
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_notificationSender = notificationSender;
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}
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/// <inheritdoc />
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public async Task<object?> EvaluateAsync(string expression, Type returnType, ExpressionExecutionContext context, CancellationToken cancellationToken = default)
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{
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using var gil = Py.GIL();
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using var scope = Py.CreateScope();
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var notification = new EvaluatingPython(scope, context);
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scope.Import("System");
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// Add globals.
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scope.Set("execution_context", new ExecutionContextProxy(context));
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scope.Set("input", new InputProxy(context));
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scope.Set("output", new OutputProxy(context));
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scope.Set("outcome", new OutcomeProxy(context));
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await _notificationSender.SendAsync(notification, cancellationToken);
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var wrappedScript = WrapInExecuteScriptFunction(expression);
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scope.Exec(wrappedScript);
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var result = scope.Get<object>(ReturnVarName);
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return result.ConvertTo(returnType);
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}
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/// <summary>
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/// Wraps the user script in a function called execute_script() and returns the result of that function.
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/// </summary>
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private static string WrapInExecuteScriptFunction(string userScript, int indentationLevel = 1)
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{
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var lines = userScript.Split('\n');
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var wrappedScript = new StringBuilder();
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var indentation = new string(' ', 4 * indentationLevel);
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wrappedScript.AppendLine("def execute_script():");
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foreach (var line in lines.Take(lines.Length - 1))
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wrappedScript.AppendLine(indentation + line);
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var lastLine = lines.LastOrDefault() ?? "";
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if (!lastLine.StartsWith("return"))
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lastLine = $"return {lastLine}";
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wrappedScript.AppendLine(indentation + lastLine);
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wrappedScript.AppendLine($"{ReturnVarName} = execute_script()");
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return wrappedScript.ToString();
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}
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}
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