149 lines
5.1 KiB
Rust
149 lines
5.1 KiB
Rust
//! # Pattern: Conditional Execution with Data Validation
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//!
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//! This example demonstrates how to implement conditional logic in DAGs by using
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//! simple data transformations rather than traditional Result types.
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//!
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//! ## What You'll Learn
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//! - How to implement validation logic in parallel tasks
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//! - How to use return values for conditional behavior (e.g., 0 for invalid)
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//! - How to categorize and branch based on computed values
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//! - How to aggregate results from multiple conditional branches
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//!
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//! ## Workflow Diagram
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//! ```text
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//! VALIDATE CATEGORIZE SUMMARIZE
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//! ┌─────────────┐ ┌──────────────┐
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//! │ Validate(10)│────20──►│Categorize(25)│────"low"────┐
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//! └─────────────┘ └──────────────┘ │
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//! │
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//! ┌─────────────┐ ┌──────────────┐ │
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//! │ Validate(-5)│────0───►│Categorize(25)│──"invalid"──┼──►┌────────────┐
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//! └─────────────┘ └──────────────┘ │ │ Summarize │
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//! │ └────────────┘
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//! ┌─────────────┐ ┌──────────────┐ │
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//! │ Validate(20)│────40──►│Categorize(25)│────"high"───┘
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//! └─────────────┘ └──────────────┘
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//! ```
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//!
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//! ## Key Concepts
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//! - **Validation as transformation**: Invalid inputs become sentinel values (0)
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//! - **Parallel validation**: All inputs validated simultaneously
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//! - **Data-driven branching**: Categorization based on computed values
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//! - **Type-safe aggregation**: All branches produce the same type (String)
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//!
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//! ## Use Cases
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//! - Input validation pipelines
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//! - Multi-stage data cleaning
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//! - Classification and categorization workflows
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//! - Quality control systems
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//! - Data preprocessing for ML pipelines
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//!
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//! ## Running This Example
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//! ```bash
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//! cargo run --example conditional_workflow
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//! ```
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//!
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//! ## Expected Output
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//! ```text
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//! Processing and categorizing inputs in parallel...
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//!
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//! Valid input 10: doubling to 20
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//! Invalid input -5: returning 0
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//! Valid input 20: doubling to 40
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//!
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//! Final summary: Categories: [low, invalid, high]
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//! Expected: Categories: [low, invalid, high]
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//! ```
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use dagx::{task, DagResult, DagRunner};
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use futures::FutureExt;
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// Task that validates and processes input
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struct ValidateAndDouble {
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value: i32,
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}
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impl ValidateAndDouble {
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fn new(value: i32) -> Self {
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Self { value }
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}
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}
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#[task]
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impl ValidateAndDouble {
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async fn run(&mut self) -> i32 {
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if self.value > 0 {
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println!("Valid input {}: doubling to {}", self.value, self.value * 2);
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self.value * 2
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} else {
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println!("Invalid input {}: returning 0", self.value);
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0 // Return 0 for invalid inputs
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}
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}
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}
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// Task that categorizes a number
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struct Categorize {
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threshold: i32,
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}
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impl Categorize {
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fn new(threshold: i32) -> Self {
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Self { threshold }
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}
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}
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#[task]
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impl Categorize {
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async fn run(&mut self, value: &i32) -> String {
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if *value == 0 {
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"invalid".to_string()
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} else if *value >= self.threshold {
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"high".to_string()
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} else {
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"low".to_string()
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}
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}
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}
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// Task that combines categorization results
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struct SummarizeResults;
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#[task]
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impl SummarizeResults {
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async fn run(cat1: &String, cat2: &String, cat3: &String) -> String {
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format!("Categories: [{}, {}, {}]", cat1, cat2, cat3)
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}
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}
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#[tokio::main]
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async fn main() -> DagResult<()> {
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let dag = DagRunner::new();
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println!("Processing and categorizing inputs in parallel...\n");
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// Validate and process multiple inputs in parallel
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let processed1 = dag.add_task(ValidateAndDouble::new(10)); // Valid: 20
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let processed2 = dag.add_task(ValidateAndDouble::new(-5)); // Invalid: 0
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let processed3 = dag.add_task(ValidateAndDouble::new(20)); // Valid: 40
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// Categorize each result (also parallel, threshold = 25)
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let cat1 = dag.add_task(Categorize::new(25)).depends_on(&processed1); // 20 < 25 = "low"
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let cat2 = dag.add_task(Categorize::new(25)).depends_on(&processed2); // 0 = "invalid"
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let cat3 = dag.add_task(Categorize::new(25)).depends_on(&processed3); // 40 >= 25 = "high"
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// Combine results
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let summary = dag
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.add_task(SummarizeResults)
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.depends_on((&cat1, &cat2, &cat3));
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// Execute
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dag.run(|fut| tokio::spawn(fut).map(Result::unwrap)).await?;
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// Display results
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println!("\nFinal summary: {}", dag.get(summary)?);
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println!("Expected: Categories: [low, invalid, high]");
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Ok(())
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}
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