//
//  WidgetDataProvider.swift
//  FeelsWidget
//
//  Lightweight read-only data provider for widgets.
//  Uses its own ModelContainer to avoid conflicts with the main app.
//

import Foundation
import SwiftData
import os.log

/// Lightweight read-only data provider for widgets
/// Uses its own ModelContainer to avoid SwiftData conflicts with main app
@MainActor
final class WidgetDataProvider {

    static let shared = WidgetDataProvider()

    private static let logger = Logger(subsystem: Bundle.main.bundleIdentifier ?? "com.tt.ifeel", category: "WidgetDataProvider")

    private var _container: ModelContainer?

    private var container: ModelContainer {
        if let existing = _container {
            return existing
        }
        let newContainer = createContainer()
        _container = newContainer
        return newContainer
    }

    /// Creates the ModelContainer for widget data access
    private func createContainer() -> ModelContainer {
        let schema = Schema([MoodEntryModel.self])

        // Try to use shared app group container
        do {
            let storeURL = try getStoreURL()
            let configuration = ModelConfiguration(
                schema: schema,
                url: storeURL,
                cloudKitDatabase: .none
            )
            return try ModelContainer(for: schema, configurations: [configuration])
        } catch {
            Self.logger.warning("Falling back to in-memory storage: \(error.localizedDescription)")
            // Fall back to in-memory storage
            let config = ModelConfiguration(schema: schema, isStoredInMemoryOnly: true)
            do {
                return try ModelContainer(for: schema, configurations: [config])
            } catch {
                Self.logger.critical("Failed to create ModelContainer: \(error.localizedDescription)")
                preconditionFailure("Unable to create ModelContainer: \(error)")
            }
        }
    }

    private func getStoreURL() throws -> URL {
        let appGroupID = Constants.currentGroupShareId
        guard let containerURL = FileManager.default.containerURL(
            forSecurityApplicationGroupIdentifier: appGroupID
        ) else {
            throw NSError(domain: "WidgetDataProvider", code: 1, userInfo: [NSLocalizedDescriptionKey: "App Group not available"])
        }
        #if DEBUG
        return containerURL.appendingPathComponent("Feels-Debug.store")
        #else
        return containerURL.appendingPathComponent("Feels.store")
        #endif
    }

    private var modelContext: ModelContext {
        container.mainContext
    }

    private init() {}

    // MARK: - Data Access

    /// Get a single entry for a specific date
    func getEntry(byDate date: Date) -> MoodEntryModel? {
        let startDate = Calendar.current.startOfDay(for: date)
        let endDate = Calendar.current.date(byAdding: .day, value: 1, to: startDate)!

        var descriptor = FetchDescriptor<MoodEntryModel>(
            predicate: #Predicate { entry in
                entry.forDate >= startDate && entry.forDate <= endDate
            },
            sortBy: [SortDescriptor(\.forDate, order: .forward)]
        )
        descriptor.fetchLimit = 1

        return try? modelContext.fetch(descriptor).first
    }

    /// Get entries within a date range, filtered by weekdays
    func getData(startDate: Date, endDate: Date, includedDays: [Int]) -> [MoodEntryModel] {
        let weekDays = includedDays.isEmpty ? [1, 2, 3, 4, 5, 6, 7] : includedDays

        let descriptor = FetchDescriptor<MoodEntryModel>(
            predicate: #Predicate { entry in
                entry.forDate >= startDate &&
                entry.forDate <= endDate &&
                weekDays.contains(entry.weekDay)
            },
            sortBy: [SortDescriptor(\.forDate, order: .forward)]
        )

        return (try? modelContext.fetch(descriptor)) ?? []
    }

    /// Get the earliest entry in the database
    var earliestEntry: MoodEntryModel? {
        var descriptor = FetchDescriptor<MoodEntryModel>(
            sortBy: [SortDescriptor(\.forDate, order: .forward)]
        )
        descriptor.fetchLimit = 1
        return try? modelContext.fetch(descriptor).first
    }

    /// Get the latest entry in the database
    var latestEntry: MoodEntryModel? {
        var descriptor = FetchDescriptor<MoodEntryModel>(
            sortBy: [SortDescriptor(\.forDate, order: .reverse)]
        )
        descriptor.fetchLimit = 1
        return try? modelContext.fetch(descriptor).first
    }

    // MARK: - Widget-Specific Helpers

    /// Get today's mood entry
    func getTodayEntry() -> MoodEntryModel? {
        getEntry(byDate: Date())
    }

    /// Get the current streak count
    func getCurrentStreak() -> Int {
        let entries = getData(
            startDate: Calendar.current.date(byAdding: .day, value: -365, to: Date())!,
            endDate: Date(),
            includedDays: [1, 2, 3, 4, 5, 6, 7]
        ).sorted { $0.forDate > $1.forDate }

        var streak = 0
        var currentDate = Calendar.current.startOfDay(for: Date())

        for entry in entries {
            let entryDate = Calendar.current.startOfDay(for: entry.forDate)

            if entryDate == currentDate && entry.mood != .missing && entry.mood != .placeholder {
                streak += 1
                currentDate = Calendar.current.date(byAdding: .day, value: -1, to: currentDate)!
            } else if entryDate < currentDate {
                break
            }
        }

        return streak
    }

    /// Invalidate cached container (call when data might have changed)
    func invalidateCache() {
        _container = nil
    }

    // MARK: - Write Operations

    /// Add a new mood entry (simplified version for widget use)
    func add(mood: Mood, forDate date: Date, entryType: EntryType) {
        // Delete existing entry for this date if present
        if let existing = getEntry(byDate: date) {
            modelContext.delete(existing)
            try? modelContext.save()
        }

        let entry = MoodEntryModel(
            forDate: date,
            mood: mood,
            entryType: entryType
        )

        modelContext.insert(entry)
        try? modelContext.save()
    }
}