(function () {
  "use strict";

  var UPLOAD_URL = "/api/upload";

  function $(id) {
    return document.getElementById(id);
  }

  function setStatus(message) {
    var status = $("status");
    status.textContent = message || "";
  }

  function setError(message) {
    var error = $("error");
    error.textContent = message || "";
  }

  function clearResult() {
    var result = $("result");
    var rowsInfo = $("rows-info");
    var tableOutput = $("table-output");
    rowsInfo.textContent = "";
    tableOutput.textContent = "";
    result.hidden = true;
  }

  function showResult(rows, table) {
    var result = $("result");
    var rowsInfo = $("rows-info");
    var tableOutput = $("table-output");
    rowsInfo.textContent = "Rows: " + rows;
    tableOutput.textContent = table || "";
    result.hidden = false;
  }

  function uploadFile(file) {
    var formData = new FormData();
    formData.append("csv", file);

    return fetch(UPLOAD_URL, {
      method: "POST",
      body: formData
    }).then(function (response) {
      return response.json().then(function (data) {
        return { ok: response.ok, status: response.status, data: data };
      });
    });
  }

  function handleSubmit(event) {
    event.preventDefault();

    setError("");
    clearResult();

    var fileInput = $("csv");
    if (!fileInput.files || fileInput.files.length === 0) {
      setError("Please choose a CSV file before uploading.");
      return;
    }

    var file = fileInput.files[0];
    var button = $("upload-button");
    button.disabled = true;
    setStatus("Uploading " + file.name + "...");

    uploadFile(file).then(function (result) {
      button.disabled = false;

      if (!result.ok) {
        setStatus("");
        var serverMsg = result.data && result.data.error ? result.data.error : "";
        var msg = "Upload failed (HTTP " + result.status + ").";
        if (serverMsg) {
          msg += " " + serverMsg;
        }
        setError(msg);
        return;
      }

      if (result.data && typeof result.data.error === "string" && result.data.error.length > 0) {
        setStatus("");
        setError(result.data.error);
        return;
      }

      var table = result.data && typeof result.data.table === "string" ? result.data.table : "";
      var rows = result.data && typeof result.data.rows === "number" ? result.data.rows : 0;

      setStatus("Upload complete.");
      showResult(rows, table);
    }).catch(function (err) {
      button.disabled = false;
      setStatus("");
      var msg = err && err.message ? err.message : String(err);
      setError("Network error while uploading: " + msg);
    });
  }

  document.addEventListener("DOMContentLoaded", function () {
    var form = $("upload-form");
    if (form) {
      form.addEventListener("submit", handleSubmit);
    }
  });
})();