import CoreText
import Foundation
import Synchronization
import SwiftData
import SwiftUI

@MainActor
@Observable
final class FontSize {
    static let shared = FontSize()
    static let range = 9...20

    private(set) var body = PrefsRecord.defaultFontSize

    private init() {
        load()
    }

    func load() {
        body = record()?.fontSize ?? PrefsRecord.defaultFontSize
    }

    func set(_ size: Int) {
        if let r = record() {
            r.fontSize = size
            r.saved = Date()
        } else {
            persistence.insert(PrefsRecord(fontSize: size))
        }
        saveRecords()
        body = size
    }

    private func record() -> PrefsRecord? {
        fetchRecords(FetchDescriptor<PrefsRecord>(sortBy: [SortDescriptor(\.saved, order: .reverse)])).first
    }
}

enum Fonts {
    private static func file(_ subset: String, _ italic: Bool, _ weight: CGFloat) -> CTFontDescriptor {
        let url = Bundle.main.resourceURL!.appending(path: "fonts/atkinson-hyperlegible-mono-\(subset)-wght-\(italic ? "italic" : "normal").woff2")
        let d = (CTFontManagerCreateFontDescriptorsFromURL(url as CFURL) as! [CTFontDescriptor])[0]
        return CTFontDescriptorCreateCopyWithVariation(d, 0x7767_6874 as CFNumber, weight)
    }

    private static func ct(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> CTFont {
        let ext = file("latin-ext", italic, weight)
        let d = CTFontDescriptorCreateCopyWithAttributes(file("latin", italic, weight), [kCTFontCascadeListAttribute: [ext]] as CFDictionary)
        return CTFontCreateWithFontDescriptor(d, size, nil)
    }

    private static let fonts = Mutex<[String: CTFont]>([:])

    // Call sites give sizes relative to a 13pt body; the user's font size shifts them all.
    @MainActor
    private static func cached(_ size: CGFloat, _ weight: CGFloat, _ italic: Bool) -> CTFont {
        let size = size + CGFloat(FontSize.shared.body - 13)
        let key = "\(size) \(weight) \(italic)"
        return fonts.withLock { fonts in
            if let f = fonts[key] {
                return f
            }
            let f = ct(size, weight: weight, italic: italic)
            fonts[key] = f
            return f
        }
    }

    @MainActor
    static func font(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> Font {
        Font(cached(size, weight, italic))
    }

    @MainActor
    static func ns(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> NSFont {
        cached(size, weight, italic) as NSFont
    }
}