//
//  ContentRuleManager.swift
//  Prisme
//
//  Author: Simon-Pierre Boucher <contact@spboucher.ai>
//

import Foundation
import Observation
import WebKit

/// Compiles the bundled blocker rules into a `WKContentRuleList`.
/// Compilation is async and off the rendering critical path: the first page
/// can start loading before rules are ready; the pool applies them to every
/// live web view as soon as compilation finishes.
@MainActor
@Observable
final class ContentRuleManager {
    private static let identifier = "prisme-blocker-v1"

    private(set) var ruleList: WKContentRuleList?

    func compileIfNeeded() async {
        guard ruleList == nil else { return }
        guard let store = WKContentRuleListStore.default() else { return }

        // Reuse a previously compiled list when the bundle hasn't changed.
        if let cached = try? await store.contentRuleList(forIdentifier: Self.identifier) {
            ruleList = cached
            return
        }

        guard
            let url = Bundle.main.url(forResource: "blockerRules", withExtension: "json"),
            let json = try? String(contentsOf: url, encoding: .utf8)
        else {
            assertionFailure("blockerRules.json missing from bundle")
            return
        }

        do {
            ruleList = try await store.compileContentRuleList(
                forIdentifier: Self.identifier,
                encodedContentRuleList: json
            )
        } catch {
            // Blocking is an enhancement, never a gate: browse without it.
            ruleList = nil
        }
    }
}