import Foundation

#if canImport(FoundationNetworking)
	import FoundationNetworking
#endif

public actor OpenFoodFactsClient {
	private let config: OpenFoodFactsConfig
	private let session: URLSession

	public init(config: OpenFoodFactsConfig, session: URLSession = .shared) {
		self.config = config
		self.session = session
	}

	// MARK: - API V2 Implementation

	/// Fetch a product by barcode.
	/// - Parameters:
	///   - barcode: The product barcode.
	///   - fields: Optional list of fields to fetch (optimizes network usage).
	public func product(barcode: String, fields: [ProductField]? = nil)
		async throws -> Product?
	{
		var url = config.apiURL.appendingPathComponent("/product/\(barcode)")

		// Append fields parameter if present
		if let fields = fields, !fields.isEmpty {
			let fieldString = fields.map { $0.rawValue }.joined(separator: ",")
			if var components = URLComponents(
				url: url, resolvingAgainstBaseURL: true)
			{
				components.queryItems = [
					URLQueryItem(name: "fields", value: fieldString)
				]
				if let newUrl = components.url { url = newUrl }
			}
		}

		let request = buildRequest(url: url)
		let (data, response) = try await session.data(for: request)

		guard let httpResponse = response as? HTTPURLResponse,
			(200...299).contains(httpResponse.statusCode)
		else {
			throw OFFError.invalidResponse
		}

		let envelope = try JSONDecoder().decode(
			ProductResponseEnvelope.self, from: data)
		return envelope.product
	}

	/// Search for products using V2 API.
	public func search(
		_ parameters: SearchParameter..., fields: [ProductField]? = nil
	) async throws -> [Product] {
		guard
			var components = URLComponents(
				url: config.apiURL.appendingPathComponent("/search"),
				resolvingAgainstBaseURL: true)
		else {
			throw OFFError.invalidURL
		}

		var queryItems: [URLQueryItem] = []

		// Add requested fields
		if let fields = fields, !fields.isEmpty {
			let fieldVal = fields.map { $0.rawValue }.joined(separator: ",")
			queryItems.append(URLQueryItem(name: "fields", value: fieldVal))
		}

		let parameters = Set(parameters)
		// Add search parameters
		for param in parameters {
			switch param {
			case .query(let q):
				queryItems.append(URLQueryItem(name: "search_terms", value: q))
			case .tag(let tag, let value):
				// V2 allows dynamic tags like `brands_tags=coca`
				queryItems.append(
					URLQueryItem(name: "\(tag.rawValue)_tags", value: value))
			case .page(let p):
				queryItems.append(URLQueryItem(name: "page", value: String(p)))
			case .pageSize(let s):
				queryItems.append(
					URLQueryItem(name: "page_size", value: String(s)))
			case .sort(let s):
				queryItems.append(
					URLQueryItem(name: "sort_by", value: s.rawValue))
			}
		}

		components.queryItems = queryItems
		guard let url = components.url else { throw OFFError.invalidURL }

		let request = buildRequest(url: url)
		let (data, response) = try await session.data(for: request)

		guard let httpResponse = response as? HTTPURLResponse,
			(200...299).contains(httpResponse.statusCode)
		else {
			throw OFFError.invalidResponse
		}

		let envelope = try JSONDecoder().decode(
			SearchResponseEnvelope.self, from: data)
		return envelope.products ?? []
	}

	// MARK: - Private Helpers

	private func buildRequest(url: URL) -> URLRequest {
		var request = URLRequest(url: url)
		request.setValue(
			config.userAgent.description, forHTTPHeaderField: "User-Agent")
		request.setValue("application/json", forHTTPHeaderField: "Accept")
		return request
	}
}

public enum OFFError: Error {
	case invalidURL, invalidResponse
}

// Internal Envelopes for Decoding
struct ProductResponseEnvelope: Decodable {
	let code: String?
	let product: Product?
	let status: Int?
}

struct SearchResponseEnvelope: Decodable {
	let count: Int?
	let products: [Product]?
}