The Creation Solver can be used to assign shifts based on a given demand. Additional constraints can be placed on the
problem like limiting inter-shift-start-times, accounting for limited resources used by certain shifts and/or requiring
certain skills. Flexible work is executed as late as possible and user provided preferences and costs can be used by the
solver.

The input of the creation solver consists of two parts:

The possible shifts and their properties
The demands that must be fulfilled by those shifts

The demands can be provided in two different ways, in fixed or flexible format. These cannot be mixed. Based on which
type of demand is provided, the solver will run in fixed or flexible mode, more explanation on this later in the guide.

The output of the solver contains the selected shifts along with the amount of each shift that the solver assigned. The
output is the same for fixed and flexible mode.

The solver can run in two modes: Fixed Mode and Flexible Mode.

Fixed Mode

In Fixed Mode the solver has no choice about when work needs to be done. In this mode, the input specifies how many
people we need at which point in time for what skill.

When a demand block that starts at 9am and ends at 10am has a demand value of 3, that means that 3 people are required
for that skill between 9am and 10am.

Flexible Mode

In Flexible Mode the solver has some freedom over when certain work can be done. In this mode, the input specifies
when volumes of work can be done and when they have to be completed.

When a demand block that starts at 9am and ends at 10am has a min value of 60 and a max value of 120, that means
that a minimum of 60 minutes of work needs to have been done by 10am and that the maximum amount of work that can be
done by 10am is 120 minutes.

This CREATE request schema is used for solving a Shift Creation Problem. It consists of demands and shift templates, options
and weights.

Name	Type	Required	Description
`demands`	[Demand]	true	List of labor demands
`templates`	[Template]	true	List of shift templates
`options`	Options	false	Options for solver configuration
`weights`	Weights	false	Weighting the constraints
`hook`	string(uri)	false	Webhook for getting notified after request is solved.

Demand

The demands are used to specify when shifts of each skill are needed. When using fixed mode only the demand field
needs to be specified. When using flexible mode only the min and max fields of the demands need to be specified. A
solver instance can only contain fixed or flexible demands, not both.

Property	Type	Description
`from`	string (iso DateTime)	Start time of the Demand block.
`to`	string (iso DateTime)	End time of the Demand block.
`skill`	string	The skill that is required to fulfil this demand.
`demand`	integer	The number of people needed during this Demand block. (when using fixed mode)
`min`	integer	The minimum total number of minutes that need to have been assigned to this skill by the end of this Demand block (when using flexible mode).
`max`	integer	The maximum total number of minutes that can be been assigned to this skill by the end of this Demand block (when using flexible mode).

Template

Property	Type	Description
`patterns`	Array of `Pattern`	A list of Patterns defining at what times this shift takes place.
`skill`	string	specifies the employee type that will perform the shift. Should match with a `Demand` skill field.
`min`	integer	Minimum number of people that have to be assigned to this shift. If this is known, provide it to the solver as it will speed up results.
`max`	integer	Maximum number of people that can be assigned to this shift. If this is known, provide it to the solver as it will speed up results.
`resources`	Array of `Resource Requirement`	The different resources and the number of each resource needed to execute this shift for one person (eg. 1 hammer).
`cost`	integer	The cost of assigning a single person to this shift.
`preference`	integer	A number that behaves like the cost of a shift. Used to specify a preference between two shifts that have the same cost.
`value`	integer	This is actually the decision being taken by the solver: the number of shifts to create. Optionally, you can provide a value here to override the solver's decision as a warm start.

Pattern

Property	Type	Description
`from`	string (iso DateTime)	Start time of the shift pattern.
`to`	string (iso DateTime)	End time of the shift pattern.
`breaks`	Array of `Break`	A list of breaks that take place between the `from` and `to` time.

Break

Property	Type	Description
`start`	string (iso DateTime)	Start time of this break.
`end`	string (iso DateTime)	End time of this break.

Resource Requirement

Used to specify that a shift requires a certain resource during the times when the shift takes place.
For example, a shift with skill 'worker' needs 1 hammer.

Property	Type	Description
`resourceName`	string	The name of the required resource. A resource with this name also needs to be present in the resourceAvaliability list.
`value`	integer	The amount of this resource that are needed when assigning 1 person to the shifts that holds this Resource Requirement.

Resource Availability

Used to specify which resources are available at all times and how many there are available of each resource.
An example would be that there are 5 hammers available.

Property	Type	Description
`resourceName`	string	The name of the available resource.
`max`	integer	How many units of the available resource can be used simultaneously.

Example

In the example of Single Day Shift Creation we will be testing a simple demand curve against 2 patterns from 9am to
5pm and 10am to 2pm.

{
  "solver": "CREATE",
  "demands": [
    {
      "from": "2021-10-04T08:15:00",
      "to": "2021-10-04T11:30:00",
      "skill": "mechanic",
      "demand": 3
    },
    {
      "from": "2021-10-04T11:30:00",
      "to": "2021-10-04T15:15:00",
      "skill": "mechanic",
      "demand": 6
    }
  ],
  "resourceAvailabilities": [
    {
      "resourceName": "screwdriver",
      "max": 10
    }
  ],
  "patterns": [
    {
      "name": "MON:9-5",
      "skill": "mechanic",
      "min": 0,
      "max": 10,
      "cost": 80,
      "preference": 10,
      "resourceRequirements": [
        {
          "resourceName": "screwdriver",
          "value": 1
        }
      ],
      "definition": [
        {
          "from": "2021-10-04T09:00:00",
          "to": "2021-10-04T17:00:00",
          "breaks": [
            {
              "start": "2021-10-04T12:00:00",
              "end": "2021-10-04T13:00:00"
            }
          ]
        }
      ]
    },
    {
      "name": "FLEX:10-14",
      "skill": "mechanic",
      "min": 0,
      "max": 10,
      "cost": 45,
      "preference": 0,
      "resourceRequirements": [
        {
          "resourceName": "screwdriver",
          "value": 1
        }
      ],
      "definition": [
        {
          "from": "2021-10-04T10:00:00",
          "to": "2021-10-04T14:00:00"
        }
      ]
    }
  ]
}

{
  "solver": "CREATE",
  "demands": [
    {
      "from": "2021-10-04T08:15:00",
      "to": "2021-10-04T11:30:00",
      "skill": "mechanic",
      "min": 0,
      "max": 180
    },
    {
      "from": "2021-10-04T11:30:00",
      "to": "2021-10-04T15:15:00",
      "skill": "mechanic",
      "min": 120,
      "max": 480
    }
  ],
  "resourceAvailabilities": [
    {
      "resourceName": "screwdriver",
      "max": 10
    }
  ],
  "patterns": [
    {
      "name": "MON:9-5",
      "skill": "mechanic",
      "min": 0,
      "max": 10,
      "cost": 80,
      "preference": 10,
      "resourceRequirements": [
        {
          "resourceName": "screwdriver",
          "value": 1
        }
      ],
      "definition": [
        {
          "from": "2021-10-04T09:00:00",
          "to": "2021-10-04T17:00:00",
          "breaks": [
            {
              "start": "2021-10-04T12:00:00",
              "end": "2021-10-04T13:00:00"
            }
          ]
        }
      ]
    },
    {
      "name": "FLEX:10-14",
      "skill": "mechanic",
      "min": 0,
      "max": 10,
      "cost": 45,
      "preference": 0,
      "resourceRequirements": [
        {
          "resourceName": "screwdriver",
          "value": 1
        }
      ],
      "definition": [
        {
          "from": "2021-10-04T10:00:00",
          "to": "2021-10-04T14:00:00"
        }
      ]
    }
  ]
}