//
// Copyright 2026 Element Creations Ltd.
//
// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
// Please see LICENSE files in the repository root for full details.
//

import Foundation

/// The client for the HealthChat backend (member directory, own profile, invitations).
/// Authenticates with an OpenID token that the backend verifies against the homeserver.
final class HealthChatAPIService: HealthChatAPIServiceProtocol {
    private enum Method: String {
        case get = "GET"
        case put = "PUT"
        case post = "POST"
    }
    
    private let baseURL: URL
    private let tokenProvider: HealthChatOpenIDTokenProviderProtocol
    private let urlSession: URLSession
    
    init(baseURL: URL = HealthChatSettings.apiBaseURL,
         tokenProvider: HealthChatOpenIDTokenProviderProtocol,
         urlSession: URLSession = .shared) {
        self.baseURL = baseURL
        self.tokenProvider = tokenProvider
        self.urlSession = urlSession
    }
    
    func members(searchQuery: String?) async -> Result<HealthChatMembersResponse, HealthChatAPIError> {
        var queryItems = [URLQueryItem]()
        if let searchQuery, !searchQuery.isEmpty {
            queryItems.append(.init(name: "search", value: searchQuery))
        }
        return await request(.get, path: "api/usermatrix/users", queryItems: queryItems)
    }
    
    func ownProfile() async -> Result<HealthChatMember, HealthChatAPIError> {
        await request(.get, path: "api/usermatrix/profile")
    }
    
    func updateOwnProfile(_ update: HealthChatProfileUpdate) async -> Result<Void, HealthChatAPIError> {
        guard let body = try? JSONEncoder().encode(update) else {
            return .failure(.decodingFailure)
        }
        return await send(.put, path: "api/usermatrix/profile", body: body).map { _ in }
    }
    
    func profileCompleteness() async -> Result<HealthChatProfileCompleteness, HealthChatAPIError> {
        await request(.get, path: "api/usermatrix/profile/completeness")
    }
    
    func inviteMember(email: String, personalNote: String) async -> Result<Void, HealthChatAPIError> {
        struct InvitationRequest: Encodable {
            let email: String
            let personalNote: String
        }
        
        guard let body = try? JSONEncoder().encode(InvitationRequest(email: email, personalNote: personalNote)) else {
            return .failure(.decodingFailure)
        }
        return await send(.post, path: "api/usermatrix/invite", body: body).map { _ in }
    }
    
    // MARK: - Private
    
    private func request<Response: Decodable>(_ method: Method,
                                              path: String,
                                              queryItems: [URLQueryItem] = [],
                                              body: Data? = nil) async -> Result<Response, HealthChatAPIError> {
        switch await send(method, path: path, queryItems: queryItems, body: body) {
        case .success(let data):
            do {
                return try .success(JSONDecoder().decode(Response.self, from: data))
            } catch {
                MXLog.error("Failed decoding the HealthChat API response from \(path) with error: \(error)")
                return .failure(.decodingFailure)
            }
        case .failure(let error):
            return .failure(error)
        }
    }
    
    private func send(_ method: Method,
                      path: String,
                      queryItems: [URLQueryItem] = [],
                      body: Data? = nil) async -> Result<Data, HealthChatAPIError> {
        for attempt in 0...1 {
            let token: String
            switch await tokenProvider.validToken() {
            case .success(let validToken):
                token = validToken
            case .failure(let error):
                return .failure(error)
            }
            
            var url = baseURL.appending(path: path)
            if !queryItems.isEmpty {
                url.append(queryItems: queryItems)
            }
            
            var request = URLRequest(url: url)
            request.httpMethod = method.rawValue
            request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
            if let body {
                request.httpBody = body
                request.setValue("application/json", forHTTPHeaderField: "Content-Type")
            }
            
            let data: Data
            let response: URLResponse
            do {
                (data, response) = try await urlSession.data(for: request)
            } catch {
                MXLog.error("The HealthChat API request to \(path) failed with error: \(error)")
                return .failure(.networkFailure)
            }
            
            guard let httpResponse = response as? HTTPURLResponse else {
                return .failure(.networkFailure)
            }
            
            switch httpResponse.statusCode {
            case 200...299:
                return .success(data)
            case 401 where attempt == 0:
                // The cached OpenID token may have expired server-side — retry once with a fresh one.
                tokenProvider.invalidateToken()
            case 401:
                return .failure(.unauthorized)
            default:
                MXLog.error("The HealthChat API request to \(path) failed with status: \(httpResponse.statusCode)")
                return .failure(.httpStatus(httpResponse.statusCode))
            }
        }
        
        return .failure(.unauthorized)
    }
}