import Foundation

struct HistoryEntry: Codable, Equatable {
    let role: String
    let text: String
    let timestamp: Date
}

/// Last 50 final transcript entries persisted as JSON in UserDefaults.
///
/// Persistence-only store. The visible transcript is the single canonical
/// collection owned by `TranscriptHandler.events`; this class provides the
/// durable snapshot it initializes from and syncs to. It performs no dedupe —
/// all suppression is source-aware and time-bounded in the handler.
@MainActor
final class TranscriptHistory: ObservableObject {
    @Published private(set) var entries: [HistoryEntry] = []

    static let key = "voice_history"
    static let maxEntries = 50

    init() {
        if let raw = AppPreferences.store.string(forKey: Self.key),
           let data = raw.data(using: .utf8),
           let decoded = try? JSONDecoder().decode([HistoryEntry].self, from: data) {
            entries = Array(decoded.suffix(Self.maxEntries))
        }
    }

    /// Replaces the persisted snapshot with exactly the finals currently in the
    /// canonical visible collection. Called by `TranscriptHandler` after every
    /// change so persistence and the UI never diverge. No dedupe is applied here:
    /// same-source repeats are legitimate entries.
    func sync(finals: [(role: String, text: String, timestamp: Date)]) {
        entries = Array(finals.suffix(Self.maxEntries).map {
            HistoryEntry(role: $0.role, text: $0.text, timestamp: $0.timestamp)
        })
        persist()
    }

    func clear() {
        entries.removeAll()
        persist()
    }

    private func persist() {
        guard let data = try? JSONEncoder().encode(entries) else { return }
        AppPreferences.store.set(String(decoding: data, as: UTF8.self), forKey: Self.key)
    }
}