//
//  FervorClient.swift
//  Fervor
//
//  Created by Shadowfacts on 11/25/21.
//

import Foundation

public class FervorClient {
    
    let instanceURL: URL
    let session: URLSession
    public var accessToken: String?
    
    private let decoder = JSONDecoder()
    
    public init(instanceURL: URL, accessToken: String?, session: URLSession = .shared) {
        self.instanceURL = instanceURL
        self.accessToken = accessToken
        self.session = session
    }
    
    private func buildURL(path: String) -> URL {
        var components = URLComponents(url: instanceURL, resolvingAgainstBaseURL: false)!
        components.path = path
        return components.url!
    }
    
    private func performRequest<T: Decodable>(_ request: URLRequest) async throws -> T {
        var request = request
        if let accessToken = accessToken {
            request.addValue("Bearer \(accessToken)", forHTTPHeaderField: "Authorization")
        }
        let (data, _) = try await session.data(for: request, delegate: nil)
        let decoded = try decoder.decode(T.self, from: data)
        return decoded
    }
    
    public func register(clientName: String, website: URL? = nil, redirectURI: URL) async throws -> ClientRegistration {
        var request = URLRequest(url: buildURL(path: "/api/v1/register"))
        request.httpMethod = "POST"
        request.setURLEncodedBody(params: [
            "client_name": clientName,
            "website": website?.absoluteString,
            "redirect_uri": redirectURI.absoluteString,
        ])
        return try await performRequest(request)
    }
    
    public func token(authCode: String, redirectURI: URL, clientID: String, clientSecret: String) async throws -> Token {
        var request = URLRequest(url: buildURL(path: "/oauth/token"))
        request.httpMethod = "POST"
        request.setURLEncodedBody(params: [
            "grant_type": "authorization_code",
            "authorization_code": authCode,
            "redirect_uri": redirectURI.absoluteString,
            "client_id": clientID,
            "client_secret": clientSecret,
        ])
        return try await performRequest(request)
    }
    
    public struct Auth {
        public let accessToken: String
        public let refreshToken: String?
    }
    
    public enum Error: Swift.Error {
        case urlSession(Swift.Error)
        case decode(Swift.Error)
    }
    
}