package org.jetbrains.plugins.github.api;

import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import com.google.gson.JsonParser;
import com.intellij.openapi.application.ApplicationManager;
import com.intellij.openapi.diagnostic.Logger;
import com.intellij.openapi.util.text.StringUtil;
import com.intellij.util.net.HttpConfigurable;
import com.intellij.util.net.ssl.CertificateManager;
import org.apache.http.*;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.Credentials;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.*;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.config.ConnectionConfig;
import org.apache.http.conn.ssl.X509HostnameVerifier;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.auth.BasicScheme;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicHeader;
import org.apache.http.protocol.HttpContext;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import org.jetbrains.annotations.TestOnly;
import org.jetbrains.plugins.github.exceptions.*;
import org.jetbrains.plugins.github.util.GithubAuthData;
import org.jetbrains.plugins.github.util.GithubSettings;
import org.jetbrains.plugins.github.util.GithubUrlUtil;
import org.jetbrains.plugins.github.util.GithubUtil;
import sun.security.validator.ValidatorException;

import javax.net.ssl.SSLHandshakeException;
import java.awt.*;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.util.*;
import java.util.List;

import static org.jetbrains.plugins.github.api.GithubApiUtil.createDataFromRaw;
import static org.jetbrains.plugins.github.api.GithubApiUtil.fromJson;

public class GithubConnection {
  private static final Logger LOG = GithubUtil.LOG;

  private static final HttpRequestInterceptor PREEMPTIVE_BASIC_AUTH = new PreemptiveBasicAuthInterceptor();

  @NotNull private final String myHost;
  @NotNull private final CloseableHttpClient myClient;
  private final boolean myReusable;

  private volatile HttpUriRequest myRequest;
  private volatile boolean myAborted;

  @TestOnly
  public GithubConnection(@NotNull GithubAuthData auth) {
    this(auth, false);
  }

  public GithubConnection(@NotNull GithubAuthData auth, boolean reusable) {
    myHost = auth.getHost();
    myClient = createClient(auth);
    myReusable = reusable;
  }

  private enum HttpVerb {
    GET, POST, DELETE, HEAD, PATCH
  }

  @Nullable
  public JsonElement getRequest(@NotNull String path,
                                @NotNull Header... headers) throws IOException {
    return request(path, null, Arrays.asList(headers), HttpVerb.GET).getJsonElement();
  }

  @Nullable
  public JsonElement postRequest(@NotNull String path,
                                 @Nullable String requestBody,
                                 @NotNull Header... headers) throws IOException {
    return request(path, requestBody, Arrays.asList(headers), HttpVerb.POST).getJsonElement();
  }

  @Nullable
  public JsonElement patchRequest(@NotNull String path,
                                  @Nullable String requestBody,
                                  @NotNull Header... headers) throws IOException {
    return request(path, requestBody, Arrays.asList(headers), HttpVerb.PATCH).getJsonElement();
  }

  @Nullable
  public JsonElement deleteRequest(@NotNull String path,
                                   @NotNull Header... headers) throws IOException {
    return request(path, null, Arrays.asList(headers), HttpVerb.DELETE).getJsonElement();
  }

  @NotNull
  public Header[] headRequest(@NotNull String path,
                              @NotNull Header... headers) throws IOException {
    return request(path, null, Arrays.asList(headers), HttpVerb.HEAD).getHeaders();
  }

  public void abort() {
    if (myAborted) return;
    myAborted = true;

    HttpUriRequest request = myRequest;
    if (request != null) request.abort();
  }

  public void close() throws IOException {
    myClient.close();
  }

  @NotNull
  private static CloseableHttpClient createClient(@NotNull GithubAuthData auth) {
    HttpClientBuilder builder = HttpClients.custom();

    return builder
      .setDefaultRequestConfig(createRequestConfig(auth))
      .setDefaultConnectionConfig(createConnectionConfig(auth))
      .setDefaultCredentialsProvider(createCredentialsProvider(auth))
      .setDefaultHeaders(createHeaders(auth))
      .addInterceptorFirst(PREEMPTIVE_BASIC_AUTH)
      .setSslcontext(CertificateManager.getInstance().getSslContext())
      .setHostnameVerifier((X509HostnameVerifier)CertificateManager.HOSTNAME_VERIFIER)
      .build();
  }

  @NotNull
  private static RequestConfig createRequestConfig(@NotNull GithubAuthData auth) {
    RequestConfig.Builder builder = RequestConfig.custom();

    int timeout = GithubSettings.getInstance().getConnectionTimeout();
    builder
      .setConnectTimeout(timeout)
      .setSocketTimeout(timeout);

    final HttpConfigurable proxySettings = HttpConfigurable.getInstance();
    if (auth.isUseProxy() && proxySettings.USE_HTTP_PROXY && !StringUtil.isEmptyOrSpaces(proxySettings.PROXY_HOST)) {
      builder
        .setProxy(new HttpHost(proxySettings.PROXY_HOST, proxySettings.PROXY_PORT));
    }

    return builder.build();
  }

  @NotNull
  private static ConnectionConfig createConnectionConfig(@NotNull GithubAuthData auth) {
    return ConnectionConfig.custom()
      .setCharset(Consts.UTF_8)
      .build();
  }


  @NotNull
  private static CredentialsProvider createCredentialsProvider(@NotNull GithubAuthData auth) {
    CredentialsProvider provider = new BasicCredentialsProvider();
    // Basic authentication
    GithubAuthData.BasicAuth basicAuth = auth.getBasicAuth();
    if (basicAuth != null) {
      provider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(basicAuth.getLogin(), basicAuth.getPassword()));
    }

    final HttpConfigurable proxySettings = HttpConfigurable.getInstance();
    //proxySettings.USE_HTTP_PROXY
    if (auth.isUseProxy() && proxySettings.USE_HTTP_PROXY && !StringUtil.isEmptyOrSpaces(proxySettings.PROXY_HOST)) {
      if (proxySettings.PROXY_AUTHENTICATION) {
        provider.setCredentials(new AuthScope(proxySettings.PROXY_HOST, proxySettings.PROXY_PORT),
                                new UsernamePasswordCredentials(proxySettings.PROXY_LOGIN, proxySettings.getPlainProxyPassword()));
      }
    }
    return provider;
  }

  @NotNull
  private static Collection<? extends Header> createHeaders(@NotNull GithubAuthData auth) {
    List<Header> headers = new ArrayList<Header>();
    GithubAuthData.TokenAuth tokenAuth = auth.getTokenAuth();
    if (tokenAuth != null) {
      headers.add(new BasicHeader("Authorization", "token " + tokenAuth.getToken()));
    }
    GithubAuthData.BasicAuth basicAuth = auth.getBasicAuth();
    if (basicAuth != null && basicAuth.getCode() != null) {
      headers.add(new BasicHeader("X-GitHub-OTP", basicAuth.getCode()));
    }
    return headers;
  }

  @NotNull
  private ResponsePage request(@NotNull String path,
                               @Nullable String requestBody,
                               @NotNull Collection<Header> headers,
                               @NotNull HttpVerb verb) throws IOException {
    if (myAborted) throw new GithubOperationCanceledException();

    if (EventQueue.isDispatchThread() && !ApplicationManager.getApplication().isUnitTestMode()) {
      LOG.warn("Network operation in EDT"); // TODO: fix
    }

    CloseableHttpResponse response = null;
    try {
      String uri = GithubUrlUtil.getApiUrl(myHost) + path;
      response = doREST(uri, requestBody, headers, verb);

      if (myAborted) throw new GithubOperationCanceledException();

      checkStatusCode(response, requestBody);

      HttpEntity entity = response.getEntity();
      if (entity == null) {
        return createResponse(response);
      }

      JsonElement ret = parseResponse(entity.getContent());
      if (ret.isJsonNull()) {
        return createResponse(response);
      }

      String newPath = null;
      Header pageHeader = response.getFirstHeader("Link");
      if (pageHeader != null) {
        for (HeaderElement element : pageHeader.getElements()) {
          NameValuePair rel = element.getParameterByName("rel");
          if (rel != null && "next".equals(rel.getValue())) {
            String urlString = element.toString();
            int begin = urlString.indexOf('<');
            int end = urlString.lastIndexOf('>');
            if (begin == -1 || end == -1) {
              LOG.error("Invalid 'Link' header", "{" + pageHeader.toString() + "}");
              break;
            }

            String url = urlString.substring(begin + 1, end);
            String newUrl = GithubUrlUtil.removeProtocolPrefix(url);
            int index = newUrl.indexOf('/');
            newPath = newUrl.substring(index);
            break;
          }
        }
      }

      return createResponse(ret, newPath, response);
    }
    catch (SSLHandshakeException e) { // User canceled operation from CertificateManager
      if (e.getCause() instanceof ValidatorException) {
        LOG.info("Host SSL certificate is not trusted", e);
        throw new GithubOperationCanceledException("Host SSL certificate is not trusted", e);
      }
      throw e;
    }
    catch (IOException e) {
      if (myAborted) throw new GithubOperationCanceledException("Operation canceled", e);
      throw e;
    }
    finally {
      myRequest = null;
      if (response != null) {
        response.close();
      }
      if (!myReusable) {
        myClient.close();
      }
    }
  }

  @NotNull
  private CloseableHttpResponse doREST(@NotNull final String uri,
                                       @Nullable final String requestBody,
                                       @NotNull final Collection<Header> headers,
                                       @NotNull final HttpVerb verb) throws IOException {
    HttpRequestBase request;
    switch (verb) {
      case POST:
        request = new HttpPost(uri);
        if (requestBody != null) {
          ((HttpPost)request).setEntity(new StringEntity(requestBody, ContentType.APPLICATION_JSON));
        }
        break;
      case PATCH:
        request = new HttpPatch(uri);
        if (requestBody != null) {
          ((HttpPatch)request).setEntity(new StringEntity(requestBody, ContentType.APPLICATION_JSON));
        }
        break;
      case GET:
        request = new HttpGet(uri);
        break;
      case DELETE:
        request = new HttpDelete(uri);
        break;
      case HEAD:
        request = new HttpHead(uri);
        break;
      default:
        throw new IllegalStateException("Unknown HttpVerb: " + verb.toString());
    }

    for (Header header : headers) {
      request.addHeader(header);
    }

    myRequest = request;
    return myClient.execute(request);
  }

  private static void checkStatusCode(@NotNull CloseableHttpResponse response, @Nullable String body) throws IOException {
    int code = response.getStatusLine().getStatusCode();
    switch (code) {
      case HttpStatus.SC_OK:
      case HttpStatus.SC_CREATED:
      case HttpStatus.SC_ACCEPTED:
      case HttpStatus.SC_NO_CONTENT:
        return;
      case HttpStatus.SC_UNAUTHORIZED:
      case HttpStatus.SC_PAYMENT_REQUIRED:
      case HttpStatus.SC_FORBIDDEN:
        String message = getErrorMessage(response);

        Header headerOTP = response.getFirstHeader("X-GitHub-OTP");
        if (headerOTP != null) {
          for (HeaderElement element : headerOTP.getElements()) {
            if ("required".equals(element.getName())) {
              throw new GithubTwoFactorAuthenticationException(message);
            }
          }
        }

        if (message.contains("API rate limit exceeded")) {
          throw new GithubRateLimitExceededException(message);
        }

        throw new GithubAuthenticationException("Request response: " + message);
      case HttpStatus.SC_BAD_REQUEST:
      case HttpStatus.SC_UNPROCESSABLE_ENTITY:
        if (body != null) {
          LOG.info(body);
        }
        throw new GithubStatusCodeException(code + ": " + getErrorMessage(response), code);
      default:
        throw new GithubStatusCodeException(code + ": " + getErrorMessage(response), code);
    }
  }

  @NotNull
  private static String getErrorMessage(@NotNull CloseableHttpResponse response) {
    try {
      HttpEntity entity = response.getEntity();
      if (entity != null) {
        GithubErrorMessageRaw error = fromJson(parseResponse(entity.getContent()), GithubErrorMessageRaw.class);
        return response.getStatusLine().getReasonPhrase() + " - " + error.getMessage();
      }
    }
    catch (IOException e) {
      LOG.info(e);
    }
    return response.getStatusLine().getReasonPhrase();
  }

  @NotNull
  private static JsonElement parseResponse(@NotNull InputStream githubResponse) throws IOException {
    Reader reader = new InputStreamReader(githubResponse, "UTF-8");
    try {
      return new JsonParser().parse(reader);
    }
    catch (JsonParseException jse) {
      throw new GithubJsonException("Couldn't parse GitHub response", jse);
    }
    finally {
      reader.close();
    }
  }

  public static class PagedRequest<T> {
    @Nullable private String myNextPage;
    @NotNull private final Collection<Header> myHeaders;
    @NotNull private final Class<T> myResult;
    @NotNull private final Class<? extends DataConstructor[]> myRawArray;

    @SuppressWarnings("NullableProblems")
    public PagedRequest(@NotNull String path,
                        @NotNull Class<T> result,
                        @NotNull Class<? extends DataConstructor[]> rawArray,
                        @NotNull Header... headers) {
      myNextPage = path;
      myResult = result;
      myRawArray = rawArray;
      myHeaders = Arrays.asList(headers);
    }

    @NotNull
    public List<T> next(@NotNull GithubConnection connection) throws IOException {
      if (myNextPage == null) {
        throw new NoSuchElementException();
      }

      String page = myNextPage;
      myNextPage = null;

      ResponsePage response = connection.request(page, null, myHeaders, HttpVerb.GET);

      if (response.getJsonElement() == null) {
        throw new GithubConfusingException("Empty response");
      }

      if (!response.getJsonElement().isJsonArray()) {
        throw new GithubJsonException("Wrong json type: expected JsonArray", new Exception(response.getJsonElement().toString()));
      }

      myNextPage = response.getNextPage();

      List<T> result = new ArrayList<T>();
      for (DataConstructor raw : fromJson(response.getJsonElement().getAsJsonArray(), myRawArray)) {
        result.add(createDataFromRaw(raw, myResult));
      }
      return result;
    }

    public boolean hasNext() {
      return myNextPage != null;
    }

    @NotNull
    public List<T> getAll(@NotNull GithubConnection connection) throws IOException {
      List<T> result = new ArrayList<T>();
      while (hasNext()) {
        result.addAll(next(connection));
      }
      return result;
    }
  }

  private ResponsePage createResponse(@NotNull CloseableHttpResponse response) throws GithubOperationCanceledException {
    if (myAborted) throw new GithubOperationCanceledException();

    return new ResponsePage(null, null, response.getAllHeaders());
  }

  private ResponsePage createResponse(@NotNull JsonElement ret, @Nullable String path, @NotNull CloseableHttpResponse response)
    throws GithubOperationCanceledException {
    if (myAborted) throw new GithubOperationCanceledException();

    return new ResponsePage(ret, path, response.getAllHeaders());
  }

  private static class ResponsePage {
    @Nullable private final JsonElement myResponse;
    @Nullable private final String myNextPage;
    @NotNull private final Header[] myHeaders;

    public ResponsePage(@Nullable JsonElement response, @Nullable String next, @NotNull Header[] headers) {
      myResponse = response;
      myNextPage = next;
      myHeaders = headers;
    }

    @Nullable
    public JsonElement getJsonElement() {
      return myResponse;
    }

    @Nullable
    public String getNextPage() {
      return myNextPage;
    }

    @NotNull
    public Header[] getHeaders() {
      return myHeaders;
    }
  }

  private static class PreemptiveBasicAuthInterceptor implements HttpRequestInterceptor {
    @Override
    public void process(HttpRequest request, HttpContext context) throws HttpException, IOException {
      CredentialsProvider provider = (CredentialsProvider)context.getAttribute(HttpClientContext.CREDS_PROVIDER);
      Credentials credentials = provider.getCredentials(AuthScope.ANY);
      if (credentials != null) {
        request.addHeader(new BasicScheme(Consts.UTF_8).authenticate(credentials, request, context));
      }
    }
  }
}