package jalview.analytics;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.lang.invoke.MethodHandles;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
import java.util.AbstractMap;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import jalview.bin.Cache;
import jalview.bin.Console;
import jalview.util.ChannelProperties;

public class Plausible
{
  private static final String USER_AGENT = ChannelProperties
          .getProperty("app_name", "Jalview") + " "
          + Cache.getDefault("VERSION", "Unknown") + " "
          + MethodHandles.lookup().lookupClass() + " help@jalview.org";

  private static final String JALVIEW_ID = "Jalview Desktop";

  private static final String DOMAIN = "jalview.org";

  private static final String BASE_URL = "https://plausible.io/api/event";

  public static final String APPLICATION_BASE_URL = "desktop://localhost";

  private List<Map.Entry<String, String>> queryStringValues;

  private List<Map.Entry<String, Object>> jsonObject;

  private List<Event> events;

  private List<Map.Entry<String, String>> cookieValues;

  private static boolean ENABLED = false;

  private static Plausible instance = null;

  private static final Map<String, String> defaultParams;

  static
  {
    defaultParams = new HashMap<>();
    defaultParams.put("app_name",
            ChannelProperties.getProperty("app_name") + " Desktop");
    defaultParams.put("version", Cache.getProperty("VERSION"));
    defaultParams.put("build_date",
            Cache.getDefault("BUILD_DATE", "unknown"));
    defaultParams.put("java_version", System.getProperty("java.version"));
    String val = System.getProperty("sys.install4jVersion");
    if (val != null)
    {
      defaultParams.put("install4j_version", val);
    }
    val = System.getProperty("installer_template_version");
    if (val != null)
    {
      defaultParams.put("install4j_template_version", val);
    }
    val = System.getProperty("launcher_version");
    if (val != null)
    {
      defaultParams.put("launcher_version", val);
    }
    defaultParams.put("java_arch",
            System.getProperty("os.arch") + " "
                    + System.getProperty("os.name") + " "
                    + System.getProperty("os.version"));
  }

  private Plausible()
  {
    this.resetLists();
  }

  public static void setEnabled(boolean b)
  {
    ENABLED = b;
  }

  public void sendAnalytics(String eventName, String... paramsStrings)
  {
    sendAnalytics(eventName, false, paramsStrings);
  }

  /**
   * The simplest way to send an analytic event.
   * 
   * @param eventName
   *          The event name. To emulate a webpage view use "page_view" and set
   *          a "page_location" parameter. See
   *          https://developers.google.com/analytics/devguides/collection/ga4/events?client_type=gtag
   * @param sendDefaultParams
   *          Flag whether to add the default params about the application.
   * @param paramsStrings
   *          Optional multiple Strings in key, value pairs (there should be an
   *          even number of paramsStrings) to be set as parameters of the
   *          event. To emulate a webpage view use "page_location" as the URL in
   *          a "page_view" event.
   */
  public void sendAnalytics(String eventName, boolean sendDefaultParams,
          String... paramsStrings)
  {
    // clear out old lists
    this.resetLists();

    if (!ENABLED)
    {
      Console.debug("Plausible not enabled.");
      return;
    }
    Map<String, String> params = new HashMap<>();

    // add these to all events from this application instance
    if (sendDefaultParams)
    {
      params.putAll(defaultParams);
    }

    // add (and overwrite with) the passed in params
    if (paramsStrings != null && paramsStrings.length > 0)
    {
      if (paramsStrings.length % 2 != 0)
      {
        Console.warn(
                "Cannot addEvent with odd number of paramsStrings.  Ignoring the last one.");
      }
      for (int i = 0; i < paramsStrings.length - 1; i += 2)
      {
        String key = paramsStrings[i];
        String value = paramsStrings[i + 1];
        params.put(key, value);
      }
    }

    addEvent(eventName, params);
    addQueryStringValue("measurement_id", MEASUREMENT_ID);
    addQueryStringValue("api_secret", API_SECRET);
    addQueryStringValue("_geo", "1");
    addQueryStringValue("ep.anonymize_ip", "false");
    addJsonValue("client_id", CLIENT_ID);
    addJsonValues("events", Event.toObjectList(events));
    StringBuilder urlSb = new StringBuilder();
    urlSb.append(BASE_URL);
    urlSb.append('?');
    urlSb.append(buildQueryString());
    try
    {
      URL url = new URL(urlSb.toString());
      URLConnection urlConnection = url.openConnection();
      HttpURLConnection httpURLConnection = (HttpURLConnection) urlConnection;
      httpURLConnection.setRequestMethod("POST");
      httpURLConnection.setDoOutput(true);

      String jsonString = buildJson();

      Console.debug("GA4: HTTP Request is: '" + urlSb.toString() + "'");
      Console.debug("GA4: POSTed JSON is:\n" + jsonString);

      byte[] jsonBytes = jsonString.getBytes(StandardCharsets.UTF_8);
      int jsonLength = jsonBytes.length;

      httpURLConnection.setFixedLengthStreamingMode(jsonLength);
      httpURLConnection.setRequestProperty("Content-Type",
              "application/json; charset=UTF-8");
      httpURLConnection.connect();
      try (OutputStream os = httpURLConnection.getOutputStream())
      {
        os.write(jsonBytes);
      }
      int responseCode = httpURLConnection.getResponseCode();
      String responseMessage = httpURLConnection.getResponseMessage();

      if (responseCode < 200 || responseCode > 299)
      {
        Console.warn("Plausible connection failed: '" + responseCode + " "
                + responseMessage + "'");
      }
      else
      {
        Console.debug("Plausible connection succeeded: '" + responseCode
                + " " + responseMessage + "'");
      }

      if (DEBUG)
      {
        BufferedReader br = new BufferedReader(new InputStreamReader(
                (httpURLConnection.getInputStream())));
        StringBuilder sb = new StringBuilder();
        String response;
        while ((response = br.readLine()) != null)
        {
          sb.append(response);
        }
        String body = sb.toString();
        Console.debug("Plausible response content; " + body);
      }
    } catch (MalformedURLException e)
    {
      Console.debug(
              "Somehow the Plausible BASE_URL and queryString is malformed: '"
                      + urlSb.toString() + "'",
              e);
      return;
    } catch (IOException e)
    {
      Console.debug(
              "Connection to Plausible BASE_URL '" + BASE_URL + "' failed.",
              e);
    } catch (ClassCastException e)
    {
      Console.debug(
              "Couldn't cast URLConnection to HttpURLConnection in Plausible.",
              e);
    }
  }

  public void addEvent(String name, Map<String, String> params)
  {
    Event event = new Event(name);
    if (params != null && params.size() > 0)
    {
      for (String key : params.keySet())
      {
        String value = params.get(key);
        event.addParam(key, value);
      }
    }
    events.add(event);
  }

  private void addJsonObject(String key,
          List<Map.Entry<String, Object>> object)
  {
    jsonObject.add(objectEntry(key, object));
  }

  private void addJsonValues(String key, List<Object> values)
  {
    jsonObject.add(objectEntry(key, values));
  }

  private void addJsonValue(String key, String value)
  {
    jsonObject.add(objectEntry(key, value));
  }

  private void addJsonValue(String key, int value)
  {
    jsonObject.add(objectEntry(key, Integer.valueOf(value)));
  }

  private void addJsonValue(String key, boolean value)
  {
    jsonObject.add(objectEntry(key, Boolean.valueOf(value)));
  }

  private void addQueryStringValue(String key, String value)
  {
    queryStringValues.add(stringEntry(key, value));
  }

  private void addCookieValue(String key, String value)
  {
    cookieValues.add(stringEntry(key, value));
  }

  private void resetLists()
  {
    jsonObject = new ArrayList<>();
    events = new ArrayList<Event>();
    queryStringValues = new ArrayList<>();
    cookieValues = new ArrayList<>();
  }

  public static Plausible getInstance()
  {
    if (instance == null)
    {
      instance = new Plausible();
    }
    return instance;
  }

  public static void reset()
  {
    getInstance().resetLists();
  }

  private String buildQueryString()
  {
    StringBuilder sb = new StringBuilder();
    for (Map.Entry<String, String> entry : queryStringValues)
    {
      if (sb.length() > 0)
      {
        sb.append('&');
      }
      try
      {
        sb.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
      } catch (UnsupportedEncodingException e)
      {
        sb.append(entry.getKey());
      }
      sb.append('=');
      try
      {
        sb.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
      } catch (UnsupportedEncodingException e)
      {
        sb.append(entry.getValue());
      }
    }
    return sb.toString();
  }

  private void buildCookieHeaders()
  {
    // TODO not needed yet
  }

  private String buildJson()
  {
    StringBuilder sb = new StringBuilder();
    addJsonObject(sb, 0, jsonObject);
    return sb.toString();
  }

  private void addJsonObject(StringBuilder sb, int indent,
          List<Map.Entry<String, Object>> entries)
  {
    indent(sb, indent);
    sb.append('{');
    newline(sb);
    Iterator<Map.Entry<String, Object>> entriesI = entries.iterator();
    while (entriesI.hasNext())
    {
      Map.Entry<String, Object> entry = entriesI.next();
      String key = entry.getKey();
      // TODO sensibly escape " characters in key
      Object value = entry.getValue();
      indent(sb, indent + 1);
      sb.append('"').append(quoteEscape(key)).append('"').append(':');
      space(sb);
      if (value != null && value instanceof List)
      {
        newline(sb);
      }
      addJsonValue(sb, indent + 2, value);
      if (entriesI.hasNext())
      {
        sb.append(',');
      }
      newline(sb);
    }
    indent(sb, indent);
    sb.append('}');
  }

  private void addJsonValue(StringBuilder sb, int indent, Object value)
  {
    if (value == null)
    {
      return;
    }
    try
    {
      if (value instanceof Map.Entry)
      {
        Map.Entry<String, Object> entry = (Map.Entry<String, Object>) value;
        List<Map.Entry<String, Object>> object = new ArrayList<>();
        object.add(entry);
        addJsonObject(sb, indent, object);
      }
      else if (value instanceof List)
      {
        // list of Map.Entries or list of values?
        List<Object> valueList = (List<Object>) value;
        if (valueList.size() > 0 && valueList.get(0) instanceof Map.Entry)
        {
          // entries
          // indent(sb, indent);
          List<Map.Entry<String, Object>> entryList = (List<Map.Entry<String, Object>>) value;
          addJsonObject(sb, indent, entryList);
        }
        else
        {
          // values
          indent(sb, indent);
          sb.append('[');
          newline(sb);
          Iterator<Object> valueListI = valueList.iterator();
          while (valueListI.hasNext())
          {
            Object v = valueListI.next();
            addJsonValue(sb, indent + 1, v);
            if (valueListI.hasNext())
            {
              sb.append(',');
            }
            newline(sb);
          }
          indent(sb, indent);
          sb.append("]");
        }
      }
      else if (value instanceof String)
      {
        sb.append('"').append(quoteEscape((String) value)).append('"');
      }
      else if (value instanceof Integer)
      {
        sb.append(((Integer) value).toString());
      }
      else if (value instanceof Boolean)
      {
        sb.append('"').append(((Boolean) value).toString()).append('"');
      }
    } catch (ClassCastException e)
    {
      Console.debug(
              "Could not deal with type of json Object " + value.toString(),
              e);
    }
  }

  private static String quoteEscape(String s)
  {
    if (s == null)
    {
      return null;
    }
    // this escapes quotation marks (") that aren't already escaped (in the
    // string) ready to go into a quoted JSON string value
    return s.replaceAll("((?<!\\\\)(?:\\\\{2})*)\"", "$1\\\\\"");
  }

  private static void prettyWhitespace(StringBuilder sb, String whitespace,
          int repeat)
  {
    // only add whitespace if we're in DEBUG mode
    if (!Console.getLogger().isDebugEnabled())
    {
      return;
    }
    if (repeat >= 0 && whitespace != null)
    {
      // sb.append(whitespace.repeat(repeat));
      sb.append(String.join("", Collections.nCopies(repeat, whitespace)));

    }
    else
    {
      sb.append(whitespace);
    }
  }

  private static void indent(StringBuilder sb, int indent)
  {
    prettyWhitespace(sb, "  ", indent);
  }

  private static void newline(StringBuilder sb)
  {
    prettyWhitespace(sb, "\n", -1);
  }

  private static void space(StringBuilder sb)
  {
    prettyWhitespace(sb, " ", -1);
  }

  protected static Map.Entry<String, Object> objectEntry(String s, Object o)
  {
    return new AbstractMap.SimpleEntry<String, Object>(s, o);
  }

  protected static Map.Entry<String, String> stringEntry(String s, String v)
  {
    return new AbstractMap.SimpleEntry<String, String>(s, v);
  }

  private static class Event
  {
    private String name;

    private List<Map.Entry<String, String>> params;

    @SafeVarargs
    public Event(String name, Map.Entry<String, String>... paramEntries)
    {
      this.name = name;
      this.params = new ArrayList<Map.Entry<String, String>>();
      for (Map.Entry<String, String> paramEntry : paramEntries)
      {
        if (paramEntry == null)
        {
          continue;
        }
        params.add(paramEntry);
      }
    }

    public void addParam(String param, String value)
    {
      params.add(Plausible.stringEntry(param, value));
    }

    protected List<Map.Entry<String, Object>> toObject()
    {
      List<Map.Entry<String, Object>> object = new ArrayList<>();
      object.add(Plausible.objectEntry("name", (Object) name));
      if (params.size() > 0)
      {
        object.add(Plausible.objectEntry("params", (Object) params));
      }
      return object;
    }

    protected static List<Object> toObjectList(List<Event> events)
    {
      List<Object> eventObjectList = new ArrayList<>();
      for (Event event : events)
      {
        eventObjectList.add((Object) event.toObject());
      }
      return eventObjectList;
    }
  }

}