//
// 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?
    /// 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]?
    let frames: [MotionKeyFrame]
}

/// 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).
    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["neutral"]
        else { return nil }
        return Resources(motion: motion, body: body)
    }
}