workouts/Workouts/ExerciseFigure/ExerciseMotion.swift

//
// ExerciseMotion.swift
// Workouts
//
// Copyright 2026 Rouslan Zenetl. All Rights Reserved.
//

import Foundation

/// Codable mirror of the Exercise Library's rig data (see `Exercise Library/SYSTEM.md`).
///
/// A **body profile** is a table of bone lengths; a **motion script** is key frames of
/// absolute joint angles (degrees, y-up: 0 = right, 90 = up, −90 = down), a pelvis
/// `root` in 320×180 canvas coordinates, optional IK pins for planted hands/feet, and
/// hold/tween timings. The app bundles verbatim copies exported by
/// `render.py --export` into `Resources/ExerciseMotions/` — `body.json` plus one
/// `<Exercise Name>.motion.json` per library entry.

/// Bone lengths for one figure profile (`neutral` is the default).
struct ExerciseBodyProfile: Codable {
    let headR: Double
    let neck: Double
    let spine1: Double
    let spine2: Double
    let upperArm: Double
    let foreArm: Double
    let thigh: Double
    let shin: Double
    /// Offset separating left-limb attachments visually: `[dx, dy]` in canvas points.
    let leftOffset: [Double]
}

/// One exercise's motion script: key frames plus the parts drawn in the accent color.
struct ExerciseMotion: Codable {
    let name: String
    /// 1-based frame used for the static visual (unused by the animated renderer).
    let primary: Int?
    /// Body-profile override (e.g. `"frontal"`: foreshortened legs for face-on
    /// seated machines). Nil uses the `neutral` profile.
    let figure: String?
    /// Parts (`arm_r`, `leg_l`, `spine`, …) drawn in the working accent color.
    let working: [String]?
    /// Limbs fully occluded in this view — never drawn.
    let hide: [String]?
    /// Equipment layer: scene shapes and cables behind the figure, joint-attached
    /// items (bar/dumbbell/pad) over the limbs. See SYSTEM.md "The props layer".
    let props: [MotionProp]?
    let frames: [MotionKeyFrame]
}

/// A prop's joint reference: one joint (`"hand_r"`, `"knee_l"`, `"elbow_r"`, …)
/// or the midpoint of two (`["foot_r", "foot_l"]`, `["knee_r", "foot_r"]`).
/// Extremity keys match the pin keys; elbows/knees are the mid joints.
enum PropJointRef: Codable {
    case single(String)
    case midpoint([String])

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if let name = try? container.decode(String.self) {
            self = .single(name)
        } else {
            self = .midpoint(try container.decode([String].self))
        }
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        switch self {
        case .single(let name): try container.encode(name)
        case .midpoint(let names): try container.encode(names)
        }
    }

    var names: [String] {
        switch self {
        case .single(let name): [name]
        case .midpoint(let names): names
        }
    }
}

/// One static shape of a `scene` prop, in canvas coordinates.
struct PropSceneShape: Codable {
    let kind: String          // "line" | "circle" | "rect"
    /// line: polyline points; `w` is the stroke width.
    let pts: [[Double]]?
    let w: Double?
    /// circle: center + radius; `fill` false draws an outline.
    let c: [Double]?
    let r: Double?
    let fill: Bool?
    /// rect: origin + size (`w`/`h`), corner radius `r`; always filled.
    let x: Double?
    let y: Double?
    let h: Double?
    /// Optional palette override: `"prop"` for the darker attached-item gray.
    let color: String?
}

/// One equipment prop. `type` selects the flavor; the other fields apply per type
/// (mirroring the reference renderer's `resolve_props`).
struct MotionProp: Codable {
    let type: String          // "scene" | "cable" | "bar" | "dumbbell" | "pad"
    /// scene: the static shapes.
    let shapes: [PropSceneShape]?
    /// cable: fixed anchor `[x, y]` → moving joint `to`.
    let from: [Double]?
    let to: PropJointRef?
    /// bar/dumbbell/pad: the joint(s) the item is centered on.
    let at: PropJointRef?
    /// Fixed world angle (degrees, y-up). Default: bars are horizontal;
    /// dumbbells/pads sit perpendicular to the lower bone.
    let angle: Double?
    let halfLen: Double?
    let w: Double?
    /// End-disc radius (dumbbell plates default 4.5; bars none).
    let plateR: Double?
}

/// A key frame of absolute joint angles. Limbs listed in the motion's `hide` may be
/// absent entirely; a two-element array is `[upper, lower]` bone angles.
struct MotionKeyFrame: Codable {
    /// Seconds held at this key frame (default 0.5).
    let hold: Double?
    /// Seconds animating to the *next* frame (default 0.6); the last frame tweens
    /// back to the first, looping.
    let tween: Double?
    /// Pelvis position, canvas coordinates `[x, y]`.
    let root: [Double]
    /// Pelvis→mid and mid→neck angles.
    let spine: [Double]
    /// Head direction from the neck joint.
    let neck: Double
    /// Nose-tick direction (the belly is on that side). Absent when the figure
    /// faces the viewer — no nose is drawn.
    let gaze: Double?
    let armR: [Double]?
    let armL: [Double]?
    let legR: [Double]?
    let legL: [Double]?
    /// IK targets for planted extremities, keyed `hand_r`/`hand_l`/`foot_r`/`foot_l`.
    /// A pin present in two consecutive key frames stays planted through the tween.
    let pins: [String: [Double]]?

    enum CodingKeys: String, CodingKey {
        case hold, tween, root, spine, neck, gaze, pins
        case armR = "arm_r"
        case armL = "arm_l"
        case legR = "leg_r"
        case legL = "leg_l"
    }
}

/// Finds and decodes the bundled rig resources for an exercise, by exact name match
/// against the exported `<Exercise Name>.motion.json` files.
enum ExerciseMotionLibrary {
    struct Resources {
        let motion: ExerciseMotion
        let body: ExerciseBodyProfile
    }

    /// Every exercise with a bundled motion script, sorted alphabetically. XcodeGen
    /// flattens resource groups, so `<Exercise Name>.motion.json` files land in the
    /// bundle root alongside `body.json` — enumerate all json and filter on the
    /// compound suffix (which `body.json` doesn't match).
    static let exerciseNames: [String] = {
        let urls = Bundle.main.urls(forResourcesWithExtension: "json", subdirectory: nil) ?? []
        return urls
            .map(\.lastPathComponent)
            .filter { $0.hasSuffix(".motion.json") }
            .map { String($0.dropLast(".motion.json".count)) }
            .sorted()
    }()

    /// The motion script plus the neutral body profile for `exerciseName`, or `nil`
    /// when no bundled motion matches (most exercises have none — the caller keeps
    /// its space empty).
    static func resources(for exerciseName: String) -> Resources? {
        guard
            let motionURL = Bundle.main.url(forResource: exerciseName, withExtension: "motion.json"),
            let bodyURL = Bundle.main.url(forResource: "body", withExtension: "json"),
            let motionData = try? Data(contentsOf: motionURL),
            let bodyData = try? Data(contentsOf: bodyURL),
            let motion = try? JSONDecoder().decode(ExerciseMotion.self, from: motionData),
            let profiles = try? JSONDecoder().decode([String: ExerciseBodyProfile].self, from: bodyData),
            let body = profiles[motion.figure ?? "neutral"]
        else { return nil }
        return Resources(motion: motion, body: body)
    }
}