function sendConfirmationEmail(
  name,
  email,
  dish,
  event,
  signature
) {

  const subject =
    "Your " + event + " Signup Confirmation";

  const body = `
Hi ${name},
Thank you for signing up to bring a dish to ${event}.

The dish (12 - 15 servings) your Household is bringing to Friendsgiving is:
  ${dish}

Friday, December 4th is our Annual Friendsgiving Holiday Potluck Dinner General Meeting -- SAME meeting location, the Eagles Lodge -- DIFFERENT start time: 6:30 pm -- PLEASE plan on being there by 6:00 pm with your food item since we will start promptly at 6:30 pm. Social hour starts at 5:30 pm. The chapter will be providing our traditional fried or roasted chicken as the main entree. 

${signature}
`;

  MailApp.sendEmail({
    to: email,
    subject: subject,
    body: body
  });
}


function doGet(e) {

  const spreadsheetId = e.parameter.spreadsheetId;

  if (!spreadsheetId) {

    return ContentService
      .createTextOutput(
        JSON.stringify({
          error: "Missing spreadsheetId"
        })
      )
      .setMimeType(ContentService.MimeType.JSON);
  }

  const ss =
    SpreadsheetApp.openById(spreadsheetId);

  const dishSheet =
    ss.getSheetByName("Friendsgiving_Dish");

  const logSheet =
    ss.getSheetByName("Log");

  const action =
    e.parameter.action || "loadSlots";


  // Return existing signups by phone
  if (action === "fetchSignups") {

    const logData =
      logSheet.getDataRange().getValues();

    const results =
      logData.slice(1).map(function(row) {

        return {
          timestamp: row[0],
          name: row[1],
          email: row[2],
          phone: row[3],
          dish: row[4]
        };

      });

    return ContentService
      .createTextOutput(
        JSON.stringify(results)
      )
      .setMimeType(
        ContentService.MimeType.JSON
      );
  }


  const dishes =
    dishSheet.getDataRange().getValues();

  const logs =
    logSheet.getDataRange().getValues();

  const counts = {};

  logs.slice(1).forEach(function(row) {

    const dish = row[4];

    if (!dish) return;

    counts[dish] =
      (counts[dish] || 0) + 1;
  });


  const available = [];

  dishes.slice(1).forEach(function(row) {

    const dish = row[0];

    const maxQty =
      Number(row[1]) || 0;

    const current =
      counts[dish] || 0;

    if (current < maxQty) {

      available.push({

        dish: dish,

        remaining:
          maxQty - current

      });

    }

  });

  return ContentService
    .createTextOutput(
      JSON.stringify(available)
    )
    .setMimeType(
      ContentService.MimeType.JSON
    );
}



function doPost(e) {

  const lock =
    LockService.getScriptLock();

  lock.waitLock(30000);

  try {

    const spreadsheetId =
      e.parameter.spreadsheetId;

    if (!spreadsheetId) {

      return ContentService
        .createTextOutput(
          "Missing spreadsheetId"
        );
    }

    const ss =
      SpreadsheetApp.openById(
        spreadsheetId
      );

    const dishSheet =
      ss.getSheetByName(
        "Friendsgiving_Dish"
      );

    const logSheet =
      ss.getSheetByName(
        "Log"
      );


    const dish =
      (e.parameter.slot || "")
      .trim();

    const name =
      (e.parameter.name || "")
      .trim();

    const email =
      (e.parameter.email || "")
      .trim();

    const phone =
      (e.parameter.phone || "")
      .trim();

    const event =
      e.parameter.event ||
      "Friendsgiving";

    const signature =
      e.parameter.signature || "";


    const dishRows =
      dishSheet
      .getDataRange()
      .getValues();


    const dishRow =
      dishRows
      .slice(1)
      .find(function(row) {

        return row[0] === dish;

      });


    if (!dishRow) {

      return ContentService
        .createTextOutput(
          "Invalid Dish"
        );
    }


    const maxQty =
      Number(dishRow[1]) || 0;


    const logRows =
      logSheet
      .getDataRange()
      .getValues();


    const currentCount =
      logRows
      .slice(1)
      .filter(function(row) {

        return row[4] === dish;

      })
      .length;


    if (currentCount >= maxQty) {

      return ContentService
        .createTextOutput(
          "Dish Full"
        );
    }


    logSheet.appendRow([
      new Date(),
      name,
      email,
      phone,
      dish
    ]);


    sendConfirmationEmail(
      name,
      email,
      dish,
      event,
      signature
    );


    return ContentService
      .createTextOutput(
        "Success"
      );

  }
  catch (err) {

    Logger.log(err);

    return ContentService
      .createTextOutput(
        "Error: " +
        err.message
      );

  }
  finally {

    lock.releaseLock();

  }
}