import Foundation

/// A structure to hold identified numbers and their labels.
struct IdentifiedEntry: Codable {
    let number: Int64
    let label: String
}

/// Service to manage spam and identification numbers in a shared App Group container.
final class SpamDirectoryService {
    static let shared = SpamDirectoryService()
    
    private let appGroupIdentifier = "group.com.frenocorp.kordant"
    private let blockedNumbersFile = "blocked_numbers.bin"
    private let identifiedEntriesFile = "identified_entries.json"
    
    private let fileManager = FileManager.default
    
    private var appGroupURL: URL? {
        fileManager.containerURL(forSecurityApplicationGroupIdentifier: appGroupIdentifier)
    }
    
    private init() {}
    
    // MARK: - Blocked Numbers
    
    func addBlockedNumber(_ number: Int64) throws {
        var blocked = try loadBlockedNumbers()
        if !blocked.contains(number) {
            blocked.append(number)
            blocked.sort()
            try saveBlockedNumbers(blocked)
        }
    }
    
    func removeBlockedNumber(_ number: Int64) throws {
        var blocked = try loadBlockedNumbers()
        if let index = blocked.firstIndex(of: number) {
            blocked.remove(at: index)
            try saveBlockedNumbers(blocked)
        }
    }
    
    func loadBlockedNumbers() throws -> [Int64] {
        guard let url = appGroupURL?.appendingPathComponent(blockedNumbersFile) else {
            return []
        }
        
        if !fileManager.fileExists(atPath: url.path) {
            return []
        }
        
        let data = try Data(contentsOf: url)
        return data.withUnsafeBytes { Array($0.bindMemory(to: Int64.self)) }
    }
    
    private func saveBlockedNumbers(_ numbers: [Int64]) throws {
        guard let url = appGroupURL?.appendingPathComponent(blockedNumbersFile) else { return }
        let data = numbers.withUnsafeBytes { Data($0) }
        try data.write(to: url, options: .atomic)
    }
    
    // MARK: - Identified Numbers
    
    func addIdentifiedNumber(_ number: Int64, label: String) throws {
        var entries = try loadIdentifiedEntries()
        if let index = entries.firstIndex(where: { $0.number == number }) {
            entries[index] = IdentifiedEntry(number: number, label: label)
        } else {
            entries.append(IdentifiedEntry(number: number, label: label))
        }
        // Sort by number to satisfy CallKit requirement
        entries.sort { $0.number < $1.number }
        try saveIdentifiedEntries(entries)
    }
    
    func removeIdentifiedNumber(_ number: Int64) throws {
        var entries = try loadIdentifiedEntries()
        entries.removeAll { $0.number == number }
        try saveIdentifiedEntries(entries)
    }
    
    func loadIdentifiedEntries() throws -> [IdentifiedEntry] {
        guard let url = appGroupURL?.appendingPathComponent(identifiedEntriesFile) else {
            return []
        }
        
        if !fileManager.fileExists(atPath: url.path) {
            return []
        }
        
        let data = try Data(contentsOf: url)
        return try JSONDecoder().decode([IdentifiedEntry].self, from: data)
    }
    
    private func saveIdentifiedEntries(_ entries: [IdentifiedEntry]) throws {
        guard let url = appGroupURL?.appendingPathComponent(identifiedEntriesFile) else { return }
        let data = try JSONEncoder().encode(entries)
        try data.write(to: url, options: .atomic)
    }
    
    // MARK: - Sync and Management
    
    /// Clears all data. Useful for testing or resetting.
    func clearAll() throws {
        guard let url = appGroupURL else { return }
        let blockedURL = url.appendingPathComponent(blockedNumbersFile)
        let identifiedURL = url.appendingPathComponent(identifiedEntriesFile)
        
        if fileManager.fileExists(atPath: blockedURL.path) {
            try fileManager.removeItem(at: blockedURL)
        }
        if fileManager.fileExists(atPath: identifiedURL.path) {
            try fileManager.removeItem(at: identifiedURL)
        }
    }
}