this-sample-workflow-execute-3-steps-in-sequence

# This sample workflow execute 3 steps in sequence.

---
description:
globs:
alwaysApply: false
---
This file provides rules and context for generating or understanding Go code related to a custom Domain Specific Language (DSL) for defining Temporal workflows within this project.

**DSL Overview:**

This project uses a specific Go-based DSL to define Temporal workflows declaratively. The core idea is to represent workflow logic using nested structures rather than imperative Go code directly within the workflow function.

**Core DSL Structures (Defined in `dsl` package):**

*   **`Workflow`**: The top-level structure representing the entire workflow definition.
    *   `Variables map[string]string`: Initial variables available to the workflow. These act as the initial state or input.
    *   `Root Statement`: The starting point of the workflow logic (can be a single activity, a sequence, or parallel steps).
*   **`Statement`**: A building block representing a single step or a composite structure. A `Statement` can contain one of the following:
    *   `Activity *ActivityInvocation`: Represents a call to a Temporal Activity.
    *   `Sequence *Sequence`: Represents a series of statements executed sequentially.
    *   `Parallel *Parallel`: Represents a set of statements executed in parallel.
*   **`Sequence`**: Contains a slice `Elements []*Statement` which are executed one after another.
*   **`Parallel`**: Contains a slice `Branches []*Statement` which are executed concurrently. The parallel execution waits for all branches to complete. If one branch errors, others are cancelled.
*   **`ActivityInvocation`**: Defines how to invoke a specific Temporal Activity.
    *   `Name string`: The registered name of the Temporal Activity to call.
    *   `Arguments []string`: A list of variable names (keys from the `bindings` map) whose values should be passed as arguments to the activity.
    *   `Result string`: The name of the variable (key in the `bindings` map) where the activity's result should be stored.

**Execution Flow (`SimpleDSLWorkflow`):**

*   The entry point for workflows defined using this DSL is the `SimpleDSLWorkflow` function: `func SimpleDSLWorkflow(ctx workflow.Context, dslWorkflow Workflow) ([]byte, error)`.
*   It initializes a `bindings` map from the `dslWorkflow.Variables`.
*   It sets default `workflow.ActivityOptions` (e.g., `StartToCloseTimeout`).
*   It uses `workflow.GetLogger(ctx)` for logging.
*   It recursively calls the `execute` method on the `Root` statement, passing the `ctx` and `bindings` map.

**Data Flow (`bindings`):**

*   The `bindings map[string]string` acts as the shared state or memory for the workflow execution.
*   Initial values come from `Workflow.Variables`.
*   `ActivityInvocation.Arguments` specifies which values from `bindings` to use as input for an activity.
*   `ActivityInvocation.Result` specifies the key in `bindings` where the activity's return value should be stored.
*   The `makeInput` helper function retrieves argument values from the `bindings` map based on the names listed in `ActivityInvocation.Arguments`.

**Concurrency (`Parallel` execution):**

*   The `Parallel.execute` method uses `workflow.Go` to launch each branch concurrently.
*   It uses `workflow.NewSelector` and `Future.Get` to wait for branches to complete.
*   `workflow.WithCancel` is used to cancel pending branches if one branch encounters an error.

**Working with the DSL:**

*   When asked to create or modify workflows, structure the logic using the `Workflow`, `Statement`, `Sequence`, `Parallel`, and `ActivityInvocation` types.
*   Define the flow of execution by nesting `Sequence` and `Parallel` structures within `Statement`s.
*   Specify activity calls using `ActivityInvocation`, ensuring `Name`, `Arguments`, and `Result` are correctly defined based on the available activities and the desired data flow through the `bindings` map.
*   Remember that the actual activity implementation exists separately (see `activities.mdc`) and is invoked by name.
```go
package dsl

import (
	"time"

	"go.temporal.io/sdk/workflow"
)

type (
	// Workflow is the type used to express the workflow definition. Variables are a map of valuables. Variables can be
	// used as input to Activity.
	Workflow struct {
		Variables map[string]string
		Root      Statement
	}

	// Statement is the building block of dsl workflow. A Statement can be a simple ActivityInvocation or it
	// could be a Sequence or Parallel.
	Statement struct {
		Activity *ActivityInvocation
		Sequence *Sequence
		Parallel *Parallel
	}

	// Sequence consist of a collection of Statements that runs in sequential.
	Sequence struct {
		Elements []*Statement
	}

	// Parallel can be a collection of Statements that runs in parallel.
	Parallel struct {
		Branches []*Statement
	}

	// ActivityInvocation is used to express invoking an Activity. The Arguments defined expected arguments as input to
	// the Activity, the result specify the name of variable that it will store the result as which can then be used as
	// arguments to subsequent ActivityInvocation.
	ActivityInvocation struct {
		Name      string
		Arguments []string
		Result    string
	}

	executable interface {
		execute(ctx workflow.Context, bindings map[string]string) error
	}
)

// SimpleDSLWorkflow workflow definition
func SimpleDSLWorkflow(ctx workflow.Context, dslWorkflow Workflow) ([]byte, error) {
	bindings := make(map[string]string)
	//workflowcheck:ignore Only iterates for building another map
	for k, v := range dslWorkflow.Variables {
		bindings[k] = v
	}

	ao := workflow.ActivityOptions{
		StartToCloseTimeout: 10 * time.Second,
	}
	ctx = workflow.WithActivityOptions(ctx, ao)
	logger := workflow.GetLogger(ctx)

	err := dslWorkflow.Root.execute(ctx, bindings)
	if err != nil {
		logger.Error("DSL Workflow failed.", "Error", err)
		return nil, err
	}

	logger.Info("DSL Workflow completed.")
	return nil, err
}

func (b *Statement) execute(ctx workflow.Context, bindings map[string]string) error {
	if b.Parallel != nil {
		err := b.Parallel.execute(ctx, bindings)
		if err != nil {
			return err
		}
	}
	if b.Sequence != nil {
		err := b.Sequence.execute(ctx, bindings)
		if err != nil {
			return err
		}
	}
	if b.Activity != nil {
		err := b.Activity.execute(ctx, bindings)
		if err != nil {
			return err
		}
	}
	return nil
}

func (a ActivityInvocation) execute(ctx workflow.Context, bindings map[string]string) error {
	inputParam := makeInput(a.Arguments, bindings)
	var result string
	err := workflow.ExecuteActivity(ctx, a.Name, inputParam).Get(ctx, &result)
	if err != nil {
		return err
	}
	if a.Result != "" {
		bindings[a.Result] = result
	}
	return nil
}

func (s Sequence) execute(ctx workflow.Context, bindings map[string]string) error {
	for _, a := range s.Elements {
		err := a.execute(ctx, bindings)
		if err != nil {
			return err
		}
	}
	return nil
}

func (p Parallel) execute(ctx workflow.Context, bindings map[string]string) error {
	//
	// You can use the context passed in to activity as a way to cancel the activity like standard GO way.
	// Cancelling a parent context will cancel all the derived contexts as well.
	//

	// In the parallel block, we want to execute all of them in parallel and wait for all of them.
	// if one activity fails then we want to cancel all the rest of them as well.
	childCtx, cancelHandler := workflow.WithCancel(ctx)
	selector := workflow.NewSelector(ctx)
	var activityErr error
	for _, s := range p.Branches {
		f := executeAsync(s, childCtx, bindings)
		selector.AddFuture(f, func(f workflow.Future) {
			err := f.Get(ctx, nil)
			if err != nil {
				// cancel all pending activities
				cancelHandler()
				activityErr = err
			}
		})
	}

	for i := 0; i < len(p.Branches); i++ {
		selector.Select(ctx) // this will wait for one branch
		if activityErr != nil {
			return activityErr
		}
	}

	return nil
}

func executeAsync(exe executable, ctx workflow.Context, bindings map[string]string) workflow.Future {
	future, settable := workflow.NewFuture(ctx)
	workflow.Go(ctx, func(ctx workflow.Context) {
		err := exe.execute(ctx, bindings)
		settable.Set(nil, err)
	})
	return future
}

func makeInput(argNames []string, argsMap map[string]string) []string {
	var args []string
	for _, arg := range argNames {
		args = append(args, argsMap[arg])
	}
	return args
}
```

**Example Workflows:**

Here are some example workflow implementations:

* Serial workflow:

```yaml
# This sample workflow execute 3 steps in sequence.
# 1) sampleActivity1, takes arg1 as input, and put result as result1.
# 2) sampleActivity2, takes result1 as input, and put result as result2.
# 3) sampleActivity3, takes args2 and result2 as input, and put result as result3.
variables:
  arg1: value1
  arg2: value2

root:
  sequence:
    elements:
     - activity:
        name: SampleActivity1
        arguments:
          - arg1
        result: result1
     - activity:
        name: SampleActivity2
        arguments:
          - result1
        result: result2
     - activity:
        name: SampleActivity3
        arguments:
          - arg2
          - result2
        result: result3
```

* Parallel workflow:

```yaml
# This sample workflow execute 3 steps in sequence.
# 1) activity1, takes arg1 as input, and put result as result1.
# 2) it runs a parallel block which runs below sequence branches in parallel
#  2.1) sequence 1
#    2.1.1) activity2, takes result1 as input, and put result as result2
#    2.1.2) activity3, takes arg2 and result2 as input, and put result as result3
#  2.2) sequence 2
#    2.2.1) activity4, takes result1 as input, and put result as result4
#    2.2.2) activity5, takes arg3 and result4 as input, and put result as result5
# 3) activity1, takes result3 and result5 as input, and put result as result6.
variables:
  arg1: value1
  arg2: value2
  arg3: value3

root:
  sequence:
    elements:
      - activity:
         name: SampleActivity1
         arguments:
           - arg1
         result: result1
      - parallel:
          branches:
            - sequence:
                elements:
                 - activity:
                    name: SampleActivity2
                    arguments:
                      - result1
                    result: result2
                 - activity:
                    name: SampleActivity3
                    arguments:
                      - arg2
                      - result2
                    result: result3
            - sequence:
                elements:
                 - activity:
                    name: SampleActivity4
                    arguments:
                      - result1
                    result: result4
                 - activity:
                    name: SampleActivity5
                    arguments:
                      - arg3
                      - result4
                    result: result5
      - activity:
         name: SampleActivity1
         arguments:
           - result3
           - result5
         result: result6
```