//
//  PipeRoute.swift
//  GasTankAR
//
//  Created by Dennis Nemec on 28.08.26.
//

import Foundation
import simd

/// Eine Rohrführung als geordnete Folge von Wegpunkten (Welt-Koordinaten), die zu einem
/// zusammenhängenden Pfad verbunden werden – visualisiert die geplante Rohrverlegung.
struct PipeRoute: Codable {
    private(set) var waypoints: [SIMD3<Float>] = []
    private(set) var removedSegmentIndices: Set<Int> = []

    var count: Int { waypoints.count }

    /// Gesamtlänge des Pfads über alle aktiven Segmente in Metern.
    var totalLength: Float {
        guard waypoints.count > 1 else { return 0 }
        return zip(waypoints, waypoints.dropFirst())
            .enumerated()
            .filter { !removedSegmentIndices.contains($0.offset) }
            .reduce(0) { $0 + simd_distance($1.element.0, $1.element.1) }
    }

    func isSegmentRemoved(at index: Int) -> Bool {
        removedSegmentIndices.contains(index)
    }

    mutating func removeSegmentAndOrphanedWaypoints(at index: Int) {
        guard index >= 0, index < waypoints.count - 1 else { return }
        removedSegmentIndices.insert(index)

        var connected = Array(repeating: false, count: waypoints.count)
        for segmentIndex in 0..<(waypoints.count - 1)
            where !removedSegmentIndices.contains(segmentIndex) {
            connected[segmentIndex] = true
            connected[segmentIndex + 1] = true
        }

        let oldToNew = connected.enumerated().reduce(into: [Int: Int]()) { result, item in
            if item.element {
                result[item.offset] = result.count
            }
        }

        let oldRemovedSegments = removedSegmentIndices
        waypoints = waypoints.enumerated()
            .filter { connected[$0.offset] }
            .map(\.element)

        removedSegmentIndices = Set(
            oldRemovedSegments.compactMap { oldIndex in
                guard let newIndex = oldToNew[oldIndex],
                      oldToNew[oldIndex + 1] != nil else {
                    return nil
                }
                return newIndex
            }
        )
    }

    var formattedLength: String {
        String(format: "%.2f m", totalLength)
    }

    mutating func add(_ waypoint: SIMD3<Float>) {
        waypoints.append(waypoint)
    }

    @discardableResult
    mutating func removeLast() -> SIMD3<Float>? {
        guard !waypoints.isEmpty else { return nil }
        let removedIndex = waypoints.count - 2
        removedSegmentIndices.remove(removedIndex)
        removedSegmentIndices = Set(
            removedSegmentIndices.map { index in
                index > removedIndex ? index - 1 : index
            }
        )
        return waypoints.removeLast()
    }

    mutating func clear() {
        waypoints.removeAll()
        removedSegmentIndices.removeAll()
    }
}

/// Ablaufphasen beim Erstellen einer Rohrführung.
enum PipeRoutingPhase: Equatable {
    /// Kein Rohr-Routing aktiv.
    case idle
    /// Wegpunkte werden gesetzt.
    case placing
}