//! Tests for dependency resolution order and transitive dependencies

use crate::common::task_fn;
use dagx::{task, DagResult, DagRunner, TaskHandle};

use std::sync::{Arc, Mutex};

#[tokio::test]
async fn test_dependency_resolution_order() -> DagResult<()> {
    // Test that dependencies are resolved in the correct order
    let dag = DagRunner::new();

    let execution_log = Arc::new(Mutex::new(Vec::new()));

    struct ATask {
        log: Arc<Mutex<Vec<(&'static str, i32)>>>,
    }

    #[task]
    impl ATask {
        async fn run(&self) -> i32 {
            self.log.lock().unwrap().push(("A_start", 0));
            tokio::time::sleep(tokio::time::Duration::from_millis(10)).await;
            self.log.lock().unwrap().push(("A_end", 1));
            1
        }
    }

    // Create a chain: A -> B -> C -> D -> E
    let a = dag.add_task(ATask {
        log: execution_log.clone(),
    });

    let b = {
        let log = execution_log.clone();
        dag.add_task(task_fn::<i32, _, _>(move |&x: &i32| {
            let log = log.clone();
            log.lock().unwrap().push(("B_start", x));
            assert_eq!(x, 1, "B should receive 1 from A");
            log.lock().unwrap().push(("B_end", x + 1));
            x + 1
        }))
        .depends_on(a)
    };

    let c = {
        let log = execution_log.clone();
        dag.add_task(task_fn::<i32, _, _>(move |&x: &i32| {
            let log = log.clone();
            log.lock().unwrap().push(("C_start", x));
            assert_eq!(x, 2, "C should receive 2 from B");
            log.lock().unwrap().push(("C_end", x + 1));
            x + 1
        }))
        .depends_on(b)
    };

    let d = {
        let log = execution_log.clone();
        dag.add_task(task_fn::<i32, _, _>(move |&x: &i32| {
            let log = log.clone();
            log.lock().unwrap().push(("D_start", x));
            assert_eq!(x, 3, "D should receive 3 from C");
            log.lock().unwrap().push(("D_end", x + 1));
            x + 1
        }))
        .depends_on(c)
    };

    let e = {
        let log = execution_log.clone();
        dag.add_task(task_fn::<i32, _, _>(move |&x: &i32| {
            let log = log.clone();
            log.lock().unwrap().push(("E_start", x));
            assert_eq!(x, 4, "E should receive 4 from D");
            log.lock().unwrap().push(("E_end", x + 1));
            x + 1
        }))
        .depends_on(d)
    };

    dag.run(|fut| async move { tokio::spawn(fut).await.unwrap() })
        .await?;

    assert_eq!(dag.get(e)?, 5);

    // Verify execution order
    let log = execution_log.lock().unwrap();
    let order: Vec<String> = log.iter().map(|(name, _)| name.to_string()).collect();

    // Each task should start after the previous one ends
    let a_end_pos = order.iter().position(|x| x == "A_end").unwrap();
    let b_start_pos = order.iter().position(|x| x == "B_start").unwrap();
    assert!(b_start_pos > a_end_pos, "B should start after A ends");

    let b_end_pos = order.iter().position(|x| x == "B_end").unwrap();
    let c_start_pos = order.iter().position(|x| x == "C_start").unwrap();
    assert!(c_start_pos > b_end_pos, "C should start after B ends");

    Ok(())
}

#[tokio::test]
async fn test_transitive_dependencies() -> DagResult<()> {
    // Test that transitive dependencies work correctly
    // A -> B -> C (creates transitive A -> C relationship)
    let dag = DagRunner::new();

    let a: TaskHandle<_> = dag.add_task(task_fn::<(), _, _>(|_: ()| 10)).into();
    let b = dag
        .add_task(task_fn::<i32, _, _>(|&x: &i32| x * 2))
        .depends_on(a);
    let c = dag
        .add_task(task_fn::<i32, _, _>(|&x: &i32| x + 5))
        .depends_on(b);

    dag.run(|fut| async move { tokio::spawn(fut).await.unwrap() })
        .await?;

    assert_eq!(dag.get(a)?, 10);
    assert_eq!(dag.get(b)?, 20);
    assert_eq!(dag.get(c)?, 25); // 20 + 5

    Ok(())
}

#[tokio::test]
async fn test_deep_chain_50_levels() -> DagResult<()> {
    let dag = DagRunner::new();

    let first = dag.add_task(task_fn::<(), _, _>(|_: ()| 0));
    let mut handles = vec![first.into()];

    for _i in 1..=50 {
        let next = dag
            .add_task(task_fn::<i32, _, _>(move |&x: &i32| x + 1))
            .depends_on(handles.last().unwrap());
        handles.push(next);
    }

    dag.run(|fut| async move { tokio::spawn(fut).await.unwrap() })
        .await?;

    assert_eq!(dag.get(handles.last().unwrap())?, 50);
    Ok(())
}

#[tokio::test]
async fn test_deep_chain_200_levels() -> DagResult<()> {
    let dag = DagRunner::new();

    let first = dag.add_task(task_fn::<(), _, _>(|_: ()| 1));
    let mut current = first.into();

    for _ in 0..200 {
        current = dag
            .add_task(task_fn::<i32, _, _>(|&x: &i32| x + 1))
            .depends_on(current);
    }

    dag.run(|fut| async move { tokio::spawn(fut).await.unwrap() })
        .await?;

    assert_eq!(dag.get(current)?, 201);
    Ok(())
}