cpm-planner 0.2.2

//! Integration tests for the CPM algorithm.
//!
//! These complement the in-module unit tests in `src/algorithm.rs` and
//! exercise the algorithm through the crate's public re-exports.

use cpm_planner::{CpmAlgorithm, Task, TaskKind};

fn make_task(id: &str, effort: f32, deps: Vec<&str>) -> Task {
    Task {
        id: id.to_string(),
        name: format!("Task {id}"),
        kind: TaskKind::Custom {
            description: format!("integration fixture for {id}"),
        },
        effort_hours: effort,
        dependencies: deps.into_iter().map(String::from).collect(),
        ..Default::default()
    }
}

#[test]
fn integration_linear_chain_marks_all_critical() {
    let mut tasks = vec![
        make_task("A", 1.0, vec![]),
        make_task("B", 2.0, vec!["A"]),
        make_task("C", 3.0, vec!["B"]),
    ];

    let result = CpmAlgorithm::calculate(&mut tasks);

    assert_eq!(result.total_tasks, 3);
    assert_eq!(result.critical_path, vec!["A", "B", "C"]);
    assert!((result.critical_path_duration - 6.0).abs() < 0.001);
    assert!((result.optimal_duration_parallel - 6.0).abs() < 0.001);
}

#[test]
fn integration_diamond_es_ef_values() {
    //     B (2h)
    //   /        \
    // A (1h)     D (1h)
    //   \        /
    //     C (4h)
    let mut tasks = vec![
        make_task("A", 1.0, vec![]),
        make_task("B", 2.0, vec!["A"]),
        make_task("C", 4.0, vec!["A"]),
        make_task("D", 1.0, vec!["B", "C"]),
    ];

    let result = CpmAlgorithm::calculate(&mut tasks);

    let by_id = |id: &str| result.tasks.iter().find(|t| t.id == id).expect("task");

    // A starts at 0, finishes at 1
    assert!((by_id("A").earliest_start - 0.0).abs() < 0.001);
    assert!((by_id("A").earliest_finish - 1.0).abs() < 0.001);
    // B starts at 1, finishes at 3
    assert!((by_id("B").earliest_start - 1.0).abs() < 0.001);
    assert!((by_id("B").earliest_finish - 3.0).abs() < 0.001);
    // C starts at 1, finishes at 5
    assert!((by_id("C").earliest_start - 1.0).abs() < 0.001);
    assert!((by_id("C").earliest_finish - 5.0).abs() < 0.001);
    // D starts at 5 (max of B.EF=3, C.EF=5), finishes at 6
    assert!((by_id("D").earliest_start - 5.0).abs() < 0.001);
    assert!((by_id("D").earliest_finish - 6.0).abs() < 0.001);

    // B has slack (C is the long edge); B should not be critical.
    assert!(!by_id("B").is_critical);
    assert!(by_id("A").is_critical);
    assert!(by_id("C").is_critical);
    assert!(by_id("D").is_critical);
}

#[test]
fn integration_parallel_batches_collapse_independent_tasks() {
    // Three independent tasks all start at time 0 -> single batch.
    let mut tasks = vec![
        make_task("X", 1.0, vec![]),
        make_task("Y", 2.0, vec![]),
        make_task("Z", 4.0, vec![]),
    ];
    let result = CpmAlgorithm::calculate(&mut tasks);

    assert_eq!(result.parallelizable_batches.len(), 1);
    let batch = &result.parallelizable_batches[0];
    assert_eq!(batch.tasks.len(), 3);
    // Sequential cost: 7. Parallel cost: max(1,2,4) = 4.
    assert!((batch.duration_hours - 4.0).abs() < 0.001);
    assert!((result.total_duration_sequential - 7.0).abs() < 0.001);
    assert!(result.speedup_factor > 1.7);
}

#[test]
fn integration_bottleneck_roi_ordering() {
    // ROOT blocks N downstream tasks; should top the bottleneck list.
    let mut tasks = vec![
        make_task("ROOT", 1.0, vec![]),
        make_task("L1", 2.0, vec!["ROOT"]),
        make_task("L2", 2.0, vec!["ROOT"]),
        make_task("L3", 2.0, vec!["ROOT"]),
        make_task("L4", 2.0, vec!["ROOT"]),
    ];
    let result = CpmAlgorithm::calculate(&mut tasks);

    let first = result.bottlenecks.first().expect("at least one bottleneck");
    assert_eq!(first.task_id, "ROOT");
    assert_eq!(first.blocks_count, 4);
    // ROI = 8 blocked hours / 1 effort hour = 8
    assert!(first.roi >= 7.9);
}

fn assert_chain_is_prerequisite_path(result: &cpm_planner::task::CriticalPathResult) {
    for pair in result.critical_path.windows(2) {
        let succ = result.tasks.iter().find(|t| t.id == pair[1]).expect("succ");
        assert!(
            succ.dependencies.contains(&pair[0]),
            "{} -> {} is not a prerequisite edge",
            pair[0],
            pair[1]
        );
    }
}

#[test]
fn critical_path_of_parallel_equal_chains_is_one_real_chain() {
    // Two independent, equally long chains: both fully zero-float.
    let mut tasks = vec![
        make_task("P0a", 2.0, vec![]),
        make_task("P0b", 3.0, vec!["P0a"]),
        make_task("P1a", 2.0, vec![]),
        make_task("P1b", 3.0, vec!["P1a"]),
    ];
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert_eq!(result.critical_path, vec!["P0a", "P0b"]);
}

#[test]
fn critical_path_pairs_are_prerequisite_edges_for_parallel_chains() {
    let mut tasks = vec![
        make_task("P0a", 2.0, vec![]),
        make_task("P0b", 3.0, vec!["P0a"]),
        make_task("P1a", 2.0, vec![]),
        make_task("P1b", 3.0, vec!["P1a"]),
    ];
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert_chain_is_prerequisite_path(&result);
}

#[test]
fn critical_path_duration_is_project_length_not_sum_of_zero_float_tasks() {
    let mut tasks = vec![
        make_task("P0a", 2.0, vec![]),
        make_task("P0b", 3.0, vec!["P0a"]),
        make_task("P1a", 2.0, vec![]),
        make_task("P1b", 3.0, vec!["P1a"]),
    ];
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert!((result.critical_path_duration - 5.0).abs() < 1e-3);
}

#[test]
fn critical_ids_lists_every_zero_float_task_by_start_then_id() {
    let mut tasks = vec![
        make_task("P0a", 2.0, vec![]),
        make_task("P0b", 3.0, vec!["P0a"]),
        make_task("P1a", 2.0, vec![]),
        make_task("P1b", 3.0, vec!["P1a"]),
    ];
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert_eq!(result.critical_ids, vec!["P0a", "P1a", "P0b", "P1b"]);
}

#[test]
fn equal_length_chains_prefer_the_later_starting_sink() {
    // X(5) stands alone; Y(1) -> Z(4) also ends at 5h. Sinks tie on EF, so the
    // later-starting sink Z wins and the path is the real chain Y -> Z (X is
    // never chained in).
    let mut tasks = vec![
        make_task("X", 5.0, vec![]),
        make_task("Y", 1.0, vec![]),
        make_task("Z", 4.0, vec!["Y"]),
    ];
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert_eq!(result.critical_path, vec!["Y", "Z"]);
}

#[test]
fn optimal_parallel_duration_is_max_earliest_finish() {
    // A(1) -> B(2), A -> C(4), B,C -> D(1): makespan 6, batches would sum higher.
    let mut tasks = vec![
        make_task("A", 1.0, vec![]),
        make_task("B", 2.0, vec!["A"]),
        make_task("C", 4.0, vec!["A"]),
        make_task("D", 1.0, vec!["B", "C"]),
    ];
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert!((result.optimal_duration_parallel - 6.0).abs() < 1e-3);
}

#[test]
fn duplicate_prerequisite_ids_still_schedule() {
    let mut tasks = vec![
        make_task("A", 1.0, vec![]),
        make_task("B", 2.0, vec!["A", "A"]),
    ];
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert!(result.unscheduled.is_empty());
}

#[test]
fn zero_effort_milestone_stays_on_critical_path() {
    let mut tasks = vec![
        make_task("A", 3.0, vec![]),
        make_task("M", 0.0, vec!["A"]),
        make_task("B", 2.0, vec!["M"]),
    ];
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert_eq!(result.critical_path, vec!["A", "M", "B"]);
}

#[test]
fn tight_predecessor_tie_picks_smallest_id() {
    // B and C both finish at 2 and both feed D.
    let mut tasks = vec![
        make_task("C", 2.0, vec![]),
        make_task("B", 2.0, vec![]),
        make_task("D", 1.0, vec!["C", "B"]),
    ];
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert_eq!(result.critical_path, vec!["B", "D"]);
}

#[test]
fn zero_effort_final_milestone_ends_the_critical_path() {
    let mut tasks = vec![make_task("A", 3.0, vec![]), make_task("M", 0.0, vec!["A"])];
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert_eq!(result.critical_path, vec!["A", "M"]);
}

fn make_task_with_lag(id: &str, effort: f32, deps: Vec<(&str, f32)>) -> Task {
    let mut t = make_task(id, effort, deps.iter().map(|(d, _)| *d).collect());
    t.lag_by_dependency = deps.into_iter().map(|(d, l)| (d.to_string(), l)).collect();
    t
}

fn lagged_pair() -> Vec<Task> {
    vec![
        make_task("a", 2.0, vec![]),
        make_task_with_lag("b", 1.0, vec![("a", 3.0)]),
    ]
}

#[test]
fn lag_delays_successor_start_by_lag() {
    let mut tasks = lagged_pair();
    let result = CpmAlgorithm::calculate(&mut tasks);
    let b = result.tasks.iter().find(|t| t.id == "b").expect("b");
    assert!((b.earliest_start - 5.0).abs() < 0.001);
}

#[test]
fn lag_extends_project_length() {
    let mut tasks = lagged_pair();
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert!((result.critical_path_duration - 6.0).abs() < 0.001);
}

#[test]
fn lag_edge_is_tight_on_critical_path() {
    let mut tasks = lagged_pair();
    let result = CpmAlgorithm::calculate(&mut tasks);
    assert_eq!(result.critical_path, vec!["a", "b"]);
}

#[test]
fn backward_pass_subtracts_lag() {
    // The independent 10h task fixes the project end at 10, so b has slack
    // (LS 9) and a.lf = 9 - 3 = 6; ignoring lag would give 9.
    let mut tasks = lagged_pair();
    tasks.push(make_task("c", 10.0, vec![]));
    let result = CpmAlgorithm::calculate(&mut tasks);
    let a = result.tasks.iter().find(|t| t.id == "a").expect("a");
    assert!((a.latest_finish - 6.0).abs() < 0.001);
}

#[test]
fn calculate_twice_after_shortening_is_correct() {
    let mut tasks = vec![make_task("A", 5.0, vec![]), make_task("B", 2.0, vec!["A"])];
    CpmAlgorithm::calculate(&mut tasks);
    tasks[0].effort_hours = 1.0;
    CpmAlgorithm::calculate(&mut tasks);
    assert_eq!(tasks[1].earliest_start, 1.0);
}