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

import Foundation
import SwiftUI

/// Pure reordering math shared by any list backed by `.onMove` + a `SyncEngine`
/// document write: given the row's current ids and a SwiftUI move gesture, compute
/// the renumbered `order` values and hand back only the ones that actually changed,
/// so a caller writes the smallest possible document diff.
enum RoutineOrdering {
    /// Apply SwiftUI's `.onMove` semantics to `ids` (`Array.move(fromOffsets:toOffset:)`),
    /// renumber the result 0…n-1, and return only the `(id, newOrder)` pairs whose order
    /// differs from `currentOrders[id]`. An id absent from `currentOrders` always comes
    /// back (there's nothing to compare against, so it can't be assumed unchanged).
    ///
    /// Comparing every renumbered position against the stored value — rather than only
    /// the ones the drag actually touched — also normalizes legacy colliding order
    /// values (e.g. two exercises both stored at order 0) the first time the list is
    /// dragged: every row gets its correct 0…n-1 position written, not just the moved one.
    static func changedOrders(
        ids: [String], currentOrders: [String: Int], from source: IndexSet, to destination: Int
    ) -> [(id: String, order: Int)] {
        var reordered = ids
        reordered.move(fromOffsets: source, toOffset: destination)

        return reordered.enumerated().compactMap { index, id in
            currentOrders[id] == index ? nil : (id: id, order: index)
        }
    }
}

/// Naming helper for the "duplicate this routine" action.
enum RoutineNaming {
    /// The next free "«base» Copy" name: `"«base» Copy"` when that's unused, else
    /// `"«base» Copy 2"`, `"«base» Copy 3"`, … — skipping any name already present in
    /// `existing` (case-sensitive match).
    static func uniqueName(base: String, existing: Set<String>) -> String {
        let first = "\(base) Copy"
        guard existing.contains(first) else { return first }

        var suffix = 2
        while existing.contains("\(base) Copy \(suffix)") {
            suffix += 1
        }
        return "\(base) Copy \(suffix)"
    }
}