workouts/Scripts/generate_starter_splits.swift

// Generates the bundled starter-split JSON resources for Workouts.
// Deterministic: fixed ULID timestamp (2020-01-01T00:00:00Z) + SHA256-of-label
// randomness, fixed document timestamps, encoder matching DocumentCoder
// (prettyPrinted + sortedKeys + iso8601). Re-running always emits identical bytes.
import Foundation
import CryptoKit

// MARK: - ULID (Crockford base32, 48-bit ms timestamp + 80 deterministic bits)

let crockford = Array("0123456789ABCDEFGHJKMNPQRSTVWXYZ")

func deterministicULID(label: String) -> String {
    let timestampMS: UInt64 = 1_577_836_800_000 // 2020-01-01T00:00:00Z
    var bytes = [UInt8]()
    for shift in stride(from: 40, through: 0, by: -8) {
        bytes.append(UInt8((timestampMS >> UInt64(shift)) & 0xFF))
    }
    let digest = SHA256.hash(data: Data(label.utf8))
    bytes.append(contentsOf: Array(digest).prefix(10))
    precondition(bytes.count == 16)

    // Encode 128 bits as 26 Crockford base32 chars: big-int division by 32, 26 digits.
    var chars = [Character]()
    var num = bytes
    for _ in 0..<26 {
        var remainder = 0
        var quotient = [UInt8]()
        for byte in num {
            let acc = remainder * 256 + Int(byte)
            quotient.append(UInt8(acc / 32))
            remainder = acc % 32
        }
        chars.append(crockford[remainder])
        num = quotient
    }
    return String(chars.reversed())
}

// MARK: - Document shapes (field names must mirror Shared/Model/Documents.swift)

struct MachineSetting: Codable {
    var name: String
    var value: String
}

struct ExerciseDocument: Codable {
    var id: String
    var name: String
    var order: Int
    var sets: Int
    var reps: Int
    var weight: Int
    var loadType: Int
    var durationSeconds: Int
    var machineSettings: [MachineSetting]? = nil
}

struct SplitDocument: Codable {
    var schemaVersion: Int
    var id: String
    var name: String
    var color: String
    var systemImage: String
    var order: Int
    var createdAt: Date
    var updatedAt: Date
    var exercises: [ExerciseDocument]
    var activityType: Int?
}

// MARK: - Seed data (canonical source for Workouts/Resources/StarterSplits/*.json)

struct Ex { let name: String; var weight = 0; var sets = 4; var reps = 10; var load = 1; var dur = 0 }
struct Sp { let name: String; let color: String; let icon: String; let activity: Int; let ex: [Ex] }

let seeds: [Sp] = [
    Sp(name: "Upper Body", color: "blue", icon: "figure.strengthtraining.traditional", activity: 0, ex: [
        Ex(name: "Lat Pull Down", weight: 110),
        Ex(name: "Seated Row", weight: 90),
        Ex(name: "Shoulder Press", weight: 40),
        Ex(name: "Chest Press", weight: 40),
        Ex(name: "Tricep Press", weight: 100),
        Ex(name: "Arm Curl", weight: 40),
    ]),
    Sp(name: "Core", color: "orange", icon: "figure.core.training", activity: 3, ex: [
        Ex(name: "Abdominal", weight: 40),
        Ex(name: "Rotary", weight: 40),
    ]),
    Sp(name: "Lower Body", color: "green", icon: "figure.run", activity: 0, ex: [
        Ex(name: "Leg Press", weight: 140),
        Ex(name: "Leg Curl", weight: 40),
        Ex(name: "Leg Extension", weight: 80),
        Ex(name: "Abductor", weight: 130),
        Ex(name: "Adductor", weight: 130),
        Ex(name: "Calfs", weight: 100),
    ]),
    Sp(name: "Bodyweight Core", color: "teal", icon: "figure.core.training", activity: 3, ex: [
        Ex(name: "Cat-Cow", sets: 1, reps: 10, load: 0),
        Ex(name: "Dead Bug", sets: 1, reps: 8, load: 0),
        Ex(name: "Bird Dog", sets: 1, reps: 8, load: 0),
        Ex(name: "Plank", sets: 3, reps: 0, load: 2, dur: 45),
        Ex(name: "Hollow Body Hold", sets: 3, reps: 0, load: 2, dur: 30),
        Ex(name: "Side Plank", sets: 3, reps: 0, load: 2, dur: 30),
        Ex(name: "Leg Raises", sets: 3, reps: 12, load: 0),
        Ex(name: "Bird Dog", sets: 3, reps: 8, load: 0),
        Ex(name: "Reverse Crunch", sets: 3, reps: 12, load: 0),
    ]),
]

// MARK: - Emit

let encoder = JSONEncoder()
encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
encoder.dateEncodingStrategy = .iso8601

let fixedDate = ISO8601DateFormatter().date(from: "2020-01-01T00:00:00Z")!
let outDir = URL(fileURLWithPath: CommandLine.arguments[1], isDirectory: true)
try FileManager.default.createDirectory(at: outDir, withIntermediateDirectories: true)

for (order, sp) in seeds.enumerated() {
    let slug = sp.name.lowercased().replacingOccurrences(of: " ", with: "-")
    let doc = SplitDocument(
        schemaVersion: 2,
        id: deterministicULID(label: "starter.\(slug)"),
        name: sp.name, color: sp.color, systemImage: sp.icon, order: order,
        createdAt: fixedDate, updatedAt: fixedDate,
        exercises: sp.ex.enumerated().map { idx, e in
            ExerciseDocument(
                id: deterministicULID(label: "starter.\(slug).ex\(idx)"),
                name: e.name, order: idx, sets: e.sets, reps: e.reps, weight: e.weight,
                loadType: e.load, durationSeconds: e.dur)
        },
        activityType: sp.activity)
    let data = try encoder.encode(doc)
    let file = outDir.appendingPathComponent("\(sp.name).split.json")
    try data.write(to: file)
    print("\(doc.id)  \(sp.name)  (\(sp.ex.count) exercises)")
}