ChunkedListView.swift

import SwiftUI
import SwiftData
import Algorithms

struct EntryListView: View {
    @Query(sort: \Entry.created, order: .reverse) private var entries: [Entry]
    let entryDateFormatter = DateFormatter()
    let sectionDateFormatter = DateFormatter()
    
    init() {
        entryDateFormatter.dateFormat = "EEEE, dd MMM yyyy"
        sectionDateFormatter.dateFormat = "MMM yyyy"
    }
    
    var body: some View {
        List {
            ForEach(sectionedEntries, id: \.self.0) { title, entries in
                Section(title) {
                    ForEach(entries) { entry in
                        VStack(alignment: .leading, spacing: 4) {
                            Text(entry.text)
                            Text(entryDateFormatter.string(from: entry.created))
                        }
                    }
                }
            }
        }
    }
    
    var sectionedEntries: [(String, [Entry])] {
        chunkEntries(entriesToChunk: entries)
    }
    
    func chunkEntries(entriesToChunk: [Entry]) -> [(String, [Entry])] {
        let chunks = entriesToChunk.chunked(on: {
            Calendar.current.dateComponents([.year, .month], from: $0.created)
        })
        return chunks.map {
            let chunkDate = Calendar.current.date(from: $0.0)
            return (sectionDateFormatter.string(from: chunkDate!), Array($0.1))
        }
    }
}