qubit-function 0.16.0

Functional programming traits and Box/Rc/Arc adapters for Rust, inspired by Java functional interfaces
// =============================================================================
//    Copyright (c) 2025 - 2026 Haixing Hu.
//
//    SPDX-License-Identifier: Apache-2.0
//
//    Licensed under the Apache License, Version 2.0.
// =============================================================================

//! Unit tests for callable task types.

use std::{
    cell::Cell,
    io,
    rc::Rc,
    sync::{
        Arc,
        atomic::{
            AtomicUsize,
            Ordering,
        },
    },
};

use qubit_function::{
    ArcCallable,
    BoxCallable,
    BoxCallableOnce,
    Callable,
    CallableOnce,
    RcCallable,
    SupplierOnce,
};

#[derive(Clone)]
struct ClonedCallable {
    value: i32,
}

impl Callable<i32, io::Error> for ClonedCallable {
    fn call(&mut self) -> Result<i32, io::Error> {
        Ok(self.value)
    }
}

#[derive(Clone)]
struct SharedCallable {
    count: Rc<Cell<u32>>,
}

impl Callable<u32, io::Error> for SharedCallable {
    fn call(&mut self) -> Result<u32, io::Error> {
        self.count.set(self.count.get() + 1);
        Ok(self.count.get())
    }
}

#[derive(Clone)]
struct SharedCallableForArc {
    count: Arc<AtomicUsize>,
}

impl Callable<u32, io::Error> for SharedCallableForArc {
    fn call(&mut self) -> Result<u32, io::Error> {
        let value = self.count.fetch_add(1, Ordering::SeqCst) + 1;
        Ok(value as u32)
    }
}

#[test]
fn test_callable_closure_call_returns_success_value() {
    let mut task = || Ok::<i32, io::Error>(42);

    assert_eq!(
        Callable::call(&mut task).expect("callable closure should succeed"),
        42
    );
}

#[test]
fn test_callable_closure_call_returns_error() {
    let mut task = || Err::<i32, _>(io::Error::other("failed"));

    let error =
        Callable::call(&mut task).expect_err("callable closure should fail");
    assert_eq!(error.kind(), io::ErrorKind::Other);
    assert_eq!(error.to_string(), "failed");
}

#[test]
fn test_box_callable_new_and_call() {
    let mut task = BoxCallable::new(|| Ok::<i32, io::Error>(21));

    assert_eq!(task.call().expect("box callable should succeed"), 21);
}

#[test]
fn test_box_callable_name_management() {
    let mut task =
        BoxCallable::<i32, io::Error>::new_with_name("compute", || Ok(1));

    assert_eq!(task.name(), Some("compute"));
    assert_eq!(task.to_string(), "BoxCallable(compute)");
    assert!(format!("{task:?}").contains("compute"));

    task.set_name("renamed");
    assert_eq!(task.name(), Some("renamed"));

    task.clear_name();
    assert_eq!(task.name(), None);
    assert_eq!(task.to_string(), "BoxCallable");
}

#[test]
fn test_box_callable_from_supplier() {
    let supplier = || Ok::<i32, io::Error>(34);

    let mut task = BoxCallable::from_supplier(supplier);

    assert_eq!(
        task.call()
            .expect("supplier-backed callable should succeed"),
        34,
    );
}

#[test]
fn test_box_callable_implements_supplier_once() {
    let task = BoxCallableOnce::new(|| Ok::<i32, io::Error>(55));

    let result = SupplierOnce::get(task);

    assert_eq!(result.expect("supplier callable should succeed"), 55);
}

#[test]
fn test_box_callable_map_transforms_success_value() {
    let task =
        BoxCallable::new_with_name("compute", || Ok::<i32, io::Error>(10));

    let mut mapped = task.map(|value| value * 2);

    assert_eq!(mapped.name(), Some("compute"));
    assert_eq!(mapped.call().expect("mapped callable should succeed"), 20);
}

#[test]
fn test_box_callable_map_err_transforms_error_value() {
    let task = BoxCallable::new(|| Err::<i32, _>(io::Error::other("raw")));

    let mut mapped = task.map_err(|error| error.to_string());

    assert_eq!(
        mapped.call().expect_err("mapped callable should fail"),
        "raw",
    );
}

#[test]
fn test_box_callable_and_then_runs_next_on_success() {
    let task = BoxCallable::new(|| Ok::<i32, io::Error>(4));

    let mut chained = task.and_then(|value| Ok(value * 3));

    assert_eq!(chained.call().expect("chained callable should succeed"), 12,);
}

#[test]
fn test_box_callable_and_then_skips_next_on_error() {
    let task = BoxCallable::new(|| Err::<i32, _>(io::Error::other("stop")));

    let mut chained = task.and_then(|_| Ok::<i32, io::Error>(99));

    assert_eq!(
        chained
            .call()
            .expect_err("chained callable should preserve error")
            .to_string(),
        "stop",
    );
}

#[test]
fn test_rc_callable_from_supplier() {
    let count = Rc::new(Cell::new(0));
    let captured = Rc::clone(&count);
    let mut task = RcCallable::from_supplier(move || {
        captured.set(captured.get() + 1);
        Ok::<i32, io::Error>(captured.get())
    });

    assert_eq!(task.call().expect("rc supplier should execute"), 1);
    assert_eq!(task.call().expect("rc supplier should execute again"), 2);
    assert_eq!(count.get(), 2);
}

#[test]
fn test_arc_callable_from_supplier() {
    let count = Arc::new(AtomicUsize::new(0));
    let captured = Arc::clone(&count);
    let mut task = ArcCallable::from_supplier(move || {
        captured.fetch_add(1, Ordering::SeqCst);
        Ok::<i32, io::Error>(captured.load(Ordering::SeqCst) as i32)
    });

    assert_eq!(task.call().expect("arc supplier should execute"), 1);
    assert_eq!(task.call().expect("arc supplier should execute again"), 2);
    assert_eq!(count.load(Ordering::SeqCst), 2);
}

#[derive(Clone)]
struct TextCallable {
    value: String,
}

impl Callable<String, &'static str> for TextCallable {
    fn call(&mut self) -> Result<String, &'static str> {
        Ok(self.value.clone())
    }
}

#[test]
fn test_box_callable_combinators_with_text_error_type() {
    let mut mapped =
        BoxCallable::new(|| Ok::<i32, &'static str>(5)).map(|v| v + 7);
    assert_eq!(mapped.call().expect("map should succeed"), 12);

    let mut mapped_err =
        BoxCallable::new(|| Err::<i32, _>("raw")).map_err(|e| format!("E:{e}"));
    assert_eq!(
        mapped_err
            .call()
            .expect_err("map_err should transform error"),
        "E:raw",
    );

    let mut chained = BoxCallable::new(|| Ok::<i32, &'static str>(3))
        .and_then(|v| Ok::<i32, &'static str>(v * 4));
    assert_eq!(chained.call().expect("and_then should succeed"), 12);
}