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# LoadBucket

One time bucket of a resource's load profile: when it starts, how much work is booked in it, and how much the resource can take. Buckets come in [`ResourceLoad::buckets`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/resources/resource-load.md>), returned by [`Project::load_profile`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/project/project.md#load_profile>) and [`Project::preview`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/project/project.md#preview>) inside a [`LoadProfile`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/resources/load-profile.md>).

## Declaration

```rust
#[derive(Clone, Debug, PartialEq)]
pub struct LoadBucket {
    pub start: DateTime,
    pub load: f64,
    pub capacity: f64,
    pub tasks: Option<Vec<Id>>,
}
```

With the `serde` feature, `LoadBucket` implements `Serialize` and `Deserialize` with camelCase field names. `tasks` is left out of the output when it's `None`.

## Fields

| Field | Type | Description |
|---|---|---|
| `start` | [`DateTime`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/data/date-time.md>) | Start of the bucket. The bucket length is the profile's [`LoadProfile::basis`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/resources/load-profile.md>). |
| `load` | `f64` | Work booked on the resource in this bucket, in assignment `value` units (`1.0` = 100 %). |
| `capacity` | `f64` | What the resource can take in this bucket, in the same units. [`ResourceLoad::capacity_mode`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/resources/resource-load.md>) says where the value comes from. |
| `tasks` | `Option<Vec<`[`Id`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/data/id.md>)`>>` | Ids of the tasks booked in the bucket, in input order. `None` unless the query's [`ProfileTasks`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/resources/profile-tasks.md>) asks for task lists; `Some` with an empty list when the bucket isn't listed. |

The bucket is overallocated when `load > capacity`.

## Example

```rust
use plen_core::{
    AssignmentData, Basis, DateTime, ProfileQuery, ProfileTasks, Project, ProjectData,
    ResourceData, SolveOptions, TaskData,
};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let day = |d| DateTime::from_ymd_hm(2026, 1, d, 0, 0).ok_or("invalid date");

    let mut task = TaskData::new("a");
    task.start_date = Some(day(5)?);
    task.duration = Some(3.0);

    let data = ProjectData {
        tasks: vec![task],
        resources: vec![ResourceData { id: "dev".into(), capacity: None, calendar_id: None }],
        assignments: vec![AssignmentData {
            id: None,
            task: "a".into(),
            resource: "dev".into(),
            value: 1.0,
            offset: None,
            duration: None,
        }],
        ..Default::default()
    };

    let mut project = Project::default();
    project.solve(Some(data), &SolveOptions::default())?;

    let mut query = ProfileQuery::new(day(5)?, day(10)?);
    query.basis = Some(Basis::Day);
    query.tasks = ProfileTasks::Over;

    let profile = project.load_profile(&query.into())?;
    for resource in &profile.resources {
        for bucket in &resource.buckets {
            if bucket.load > bucket.capacity {
                println!("{:?} overallocated by {}: {:?}", bucket.start, bucket.load - bucket.capacity, bucket.tasks);
            }
        }
    }
    Ok(())
}
```

## Related

- [`ResourceLoad`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/resources/resource-load.md>) - holds the buckets of one resource
- [`CapacityMode`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/resources/capacity-mode.md>) - decides the bucket's `capacity`
- [`ProfileTasks`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/resources/profile-tasks.md>) - decides whether `tasks` is filled
- [Resource Load](<https://docs.dhtmlx.com/planning-engine/rust/resources-and-assignment/resource-load.md#task-lists-per-bucket>) - reads loads and task lists from buckets