GeoHashを可視化できるアプリを作ってみた

@globalActor
struct ComputationActor {
    actor ActorType {}
    static let shared = ActorType()
}

struct ContentData: Identifiable {
    var bound: [CLLocationCoordinate2D] = []
    var geohash: GeoHash
    
    var id: GeoHash {
        geohash
    }
}

struct ContentView: View {
    
    // ...bodyに関するコード

    // 周囲のジオハッシュを取得するコード
    @ComputationActor
    private func updateBounds(coord: CLLocationCoordinate2D) async {
        var geoHashes = await Deque(
            [
                (
                    GeoHash(
                        latitude: coord.latitude,
                        longitude: coord.longitude,
                        precision: .exact(digits: bitsLength)
                    ),
                    0
                ),
            ]
        )
        var data: [ContentData] = []
        var seen: Set<GeoHash> = []
        while geoHashes.count > 0 {
            guard let (geoHash, depth) = geoHashes.popFirst() else {
                break
            }
            if depth > 4 {
                break
            }
            if seen.contains(geoHash) {
                continue
            }
            seen.insert(geoHash)
            let centerBound = geoHash.getBound().map({
                CLLocationCoordinate2D(latitude: $0.latitude, longitude: $0.longitude)
            })
            data.append(
                .init(
                    bound: centerBound + [centerBound[0]],
                    geohash: geoHash
                )
            )
            for neighbor in geoHash.getNeighbors() {
                if seen.contains(neighbor) {
                    continue
                }
                let neighborBound = neighbor.getBound().map({
                    CLLocationCoordinate2D(latitude: $0.latitude, longitude: $0.longitude)
                })
                data.append(
                    .init(
                        bound: neighborBound + [neighborBound[0]],
                        geohash: neighbor
                    )
                )
                geoHashes.append((neighbor, depth + 1))
            }
        }
        await MainActor.run { [data] in
            self.data = data
        }
    }
}

import Foundation
import OSLog

enum RuntimeWarning {
    static func log(message: StaticString, args: any CVarArg...) {
        #if DEBUG
        var dso: UnsafeRawPointer?
        // ref: https://github.com/pointfreeco/swift-issue-reporting/blob/a3f634d1a409c7979cabc0a71b3f26ffa9fc8af1/Sources/IssueReporting/IssueReporters/RuntimeWarningReporter.swift#L39-L55
        let count = _dyld_image_count()
        for i in 0..<count {
          if let name = _dyld_get_image_name(i) {
            let swiftString = String(cString: name)
            if swiftString.hasSuffix("/SwiftUI") {
              if let header = _dyld_get_image_header(i) {
                dso = UnsafeRawPointer(header)
              }
            }
          }
        }
        guard let dso = dso else {
            assertionFailure("Failed to get DSO")
            return
        }
        os_log(
            .fault,
            dso: dso,
            log: OSLog(
                subsystem: "com.apple.runtime-issues",
                category: "ReportRuntimeWarningSample"
            ),
            message,
            args
        )
        #endif
    }
}

// 利用例
extension GeoHash {
    /// Base32 characters used to hash
    ///
    // a, i, l and o are omitted
    package static var base32Chars: String {
        "0123456789bcdefghjkmnpqrstuvwxyz"
    }

    static func makeBinary(
        from geoHash: String,
        precision: GeoHashBitsPrecision
    ) -> String {
        var binary = ""

        for char in geoHash {
            guard let index = Self.base32Chars.firstIndex(of: char) else {
                // ジオハッシュの文字列に不適切な文字がある場合にRuntimeWarningを出す
                RuntimeWarning.log(
                    message: "Invalid geohash character %s in geoHash: %s",
                    args: String(char), geoHash
                )
                continue
            }