ExerciseDefinition

public struct ExerciseDefinition: Identifiable, Sendable, Hashable, Codable

Everything the engine needs to know about one exercise. Plain data: JSON in, JSON out.

init(
    id: String,
    region: BodyRegion,
    view: CameraView,
    kind: Kind,
    primary: Measure,
    rules: [FormRule] = [],
    defaultTarget: Double
)

Property	Type
id	String	Stable, e.g. "elbow.flexion". Saved with sessions: never rename it.
region	BodyRegion	neck, shoulder, elbow, wrist, back, hip, knee, ankle.
view	CameraView	.side or .front.
kind	Kind	How it’s counted (below).
primary	Measure	The main value: what gets charted and compared with the target.
rules	[FormRule]	Form rules.
defaultTarget	Double	Target in degrees if nobody sets another.

func joints(for side: BodySide) -> [Joint]

Every joint the exercise reads, the primary measure’s first.

Kind

Case
.reps(low: Double, high: Double)	Counts when the value passes high and comes back below low.
.hold(threshold: Double, seconds: Double)	Counts when the value stays above threshold and steady for seconds.

See Reps and holds.

FormRule

public struct FormRule: Sendable, Hashable, Codable {
    init(feedback: FormFeedback, measure: Measure, allowed: ClosedRange<Double>)
}

A condition that must hold while the rep lasts. If the joints of measure aren’t visible, the rule isn’t evaluated.

FormFeedback

keepUpperArmStill, keepThighStill, keepElbowStraight, keepTrunkUpright, keepShouldersLevel, keepKneeStraight, keepHipsLevel.

String, CaseIterable, Codable: the rawValue is stable for translating and storing.

ExerciseLibrary

Member
static let all: [ExerciseDefinition]	The 8 in the catalog.
static let elbowFlexion, kneeFlexionStanding, …	Each exercise by name.
static func definition(id:) -> ExerciseDefinition?	Looks up by id.
static func definitions(for: BodyRegion) -> [ExerciseDefinition]	Filters by region.
static func decode(from: Data) throws -> [ExerciseDefinition]	Reads a JSON array.
static func encode(_: [ExerciseDefinition]) throws -> Data	Writes JSON with sorted keys.