const body = document.body;
const form = document.querySelector("#roster-form");
const fileInput = document.querySelector("#roster-file");
const dropZone = document.querySelector("#drop-zone");
const dropTitle = document.querySelector("#drop-title");
const dropCopy = document.querySelector("#drop-copy");
const monthInput = document.querySelector("#month");
const suggestedMonthButton = document.querySelector("#suggested-month");
const resetLayoutButton = document.querySelector("#reset-layout");
const factoryLayoutButton = document.querySelector("#factory-layout");
const saveLayoutDefaultsButton = document.querySelector("#save-layout-defaults");
const layoutMessage = document.querySelector("#layout-message");
const layoutInputs = [...document.querySelectorAll("[data-layout-input]")];
const defaultsStatus = document.querySelector("#defaults-status");
const themeChoiceButtons = [...document.querySelectorAll("[data-theme-choice]")];
const formMessage = document.querySelector("#form-message");
const formatButton = document.querySelector("#format-button");
const buttonLabel = formatButton.querySelector(".button-label");
const resultCard = document.querySelector("#result-card");
const resultPreview = document.querySelector("#result-preview");
const resultName = document.querySelector("#result-name");
const downloadResult = document.querySelector("#download-result");
const formatAnother = document.querySelector("#format-another");
const historyList = document.querySelector("#history-list");
const refreshHistoryButton = document.querySelector("#refresh-history");
const retentionNote = document.querySelector("#retention-note");

const defaultMonth = body.dataset.defaultMonth;
const retentionMonths = Number(body.dataset.retentionMonths);
const maximumUploadMb = Number(body.dataset.maxUploadMb);
const maximumUploadBytes = maximumUploadMb * 1024 * 1024;
let selectedFile = null;
let resultUrl = null;

const themeChoices = new Set(["system", "light", "dark"]);

function setThemeChoice(choice, persist = true) {
  const selected = themeChoices.has(choice) ? choice : "system";
  document.documentElement.dataset.theme = selected;
  themeChoiceButtons.forEach((button) => {
    button.setAttribute("aria-pressed", String(button.dataset.themeChoice === selected));
  });
  if (persist) {
    try {
      localStorage.setItem("roster-theme", selected);
    } catch {
      // The theme still works when browser storage is unavailable.
    }
  }
}

function setFile(file) {
  selectedFile = file || null;
  if (!selectedFile) {
    fileInput.value = "";
    dropZone.classList.remove("has-file");
    dropTitle.textContent = "Choose your roster PDF";
    dropCopy.textContent = `or drag it here · one-page landscape Letter · up to ${maximumUploadMb} MB`;
    return;
  }

  dropZone.classList.add("has-file");
  dropTitle.textContent = selectedFile.name;
  dropCopy.textContent = `${formatFileSize(selectedFile.size)} · ready to format`;
}

function formatFileSize(bytes) {
  if (bytes < 1024 * 1024) {
    return `${Math.max(1, Math.round(bytes / 1024))} KB`;
  }
  return `${(bytes / (1024 * 1024)).toFixed(1)} MB`;
}

function showError(message) {
  formMessage.textContent = message;
  formMessage.hidden = false;
}

function clearError() {
  formMessage.textContent = "";
  formMessage.hidden = true;
}

function showLayoutMessage(message, isError = false) {
  layoutMessage.textContent = message;
  layoutMessage.classList.toggle("is-error", isError);
  layoutMessage.hidden = false;
}

function clearLayoutMessage() {
  layoutMessage.textContent = "";
  layoutMessage.classList.remove("is-error");
  layoutMessage.hidden = true;
}

function setBusy(busy) {
  body.classList.toggle("is-busy", busy);
  form.setAttribute("aria-busy", String(busy));
  formatButton.disabled = busy;
  buttonLabel.textContent = busy ? "Formatting…" : "Format roster";
}

function updateDefaultsStatus() {
  const custom = layoutInputs.some((input) => {
    if (input.value.trim() === "") {
      return true;
    }
    return Number(input.value) !== Number(input.dataset.default);
  });
  defaultsStatus.textContent = custom ? "Unsaved layout" : "Saved defaults";
  defaultsStatus.classList.toggle("is-custom", custom);
}

async function saveLayoutDefaults() {
  const invalidInput = layoutInputs.find((input) => !input.checkValidity());
  if (invalidInput) {
    invalidInput.reportValidity();
    invalidInput.focus();
    return;
  }

  const values = Object.fromEntries(layoutInputs.map((input) => [input.name, input.value]));
  const originalLabel = saveLayoutDefaultsButton.textContent;
  saveLayoutDefaultsButton.disabled = true;
  saveLayoutDefaultsButton.textContent = "Saving…";
  clearLayoutMessage();

  try {
    const response = await fetch("/api/layout-defaults", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify(values),
    });
    let payload = {};
    try {
      payload = await response.json();
    } catch {
      // Use the safe fallback below if the server returns an unexpected response.
    }
    if (!response.ok) {
      throw new Error(payload.error || "The layout defaults could not be saved.");
    }
    if (!payload.defaults || typeof payload.defaults !== "object") {
      throw new Error("The server returned an invalid defaults response.");
    }

    const canonicalValues = layoutInputs.map((input) => {
      const savedValue = payload.defaults[input.name];
      if (savedValue === undefined) {
        throw new Error("The server returned an incomplete defaults response.");
      }
      return String(savedValue);
    });
    layoutInputs.forEach((input, index) => {
      input.value = canonicalValues[index];
      input.dataset.default = canonicalValues[index];
    });
    updateDefaultsStatus();
    showLayoutMessage("Saved. These values will prefill future rosters.");
  } catch (error) {
    showLayoutMessage(error.message || "The layout defaults could not be saved.", true);
  } finally {
    saveLayoutDefaultsButton.disabled = false;
    saveLayoutDefaultsButton.textContent = originalLabel;
  }
}

function responseFilename(response) {
  const disposition = response.headers.get("Content-Disposition") || "";
  const match = disposition.match(/filename="([^"]+)"/i);
  return match ? match[1] : "Formatted Roster.png";
}

function createHistoryItem(item) {
  const link = document.createElement("a");
  link.className = "history-item";
  link.href = item.url;
  link.download = item.filename;

  const file = document.createElement("span");
  file.className = "history-file";
  const name = document.createElement("strong");
  name.textContent = item.filename;
  const details = document.createElement("small");
  details.textContent = `${formatFileSize(item.size)} · PNG`;
  file.append(name, details);

  const icon = document.createElement("span");
  icon.className = "history-download";
  icon.setAttribute("aria-hidden", "true");
  icon.textContent = "↓";
  link.append(file, icon);
  return link;
}

async function loadHistory() {
  refreshHistoryButton.disabled = true;
  try {
    const response = await fetch("/api/history", { cache: "no-store" });
    if (!response.ok) {
      throw new Error("History could not be loaded.");
    }
    const payload = await response.json();
    historyList.replaceChildren();
    if (!payload.items.length) {
      const empty = document.createElement("p");
      empty.className = "empty-state";
      empty.textContent = "Your formatted rosters will appear here.";
      historyList.append(empty);
      return;
    }
    payload.items.forEach((item) => historyList.append(createHistoryItem(item)));
  } catch (error) {
    const empty = document.createElement("p");
    empty.className = "empty-state";
    empty.textContent = error.message;
    historyList.replaceChildren(empty);
  } finally {
    refreshHistoryButton.disabled = false;
  }
}

fileInput.addEventListener("change", () => {
  setFile(fileInput.files[0] || null);
  clearError();
});

["dragenter", "dragover"].forEach((eventName) => {
  dropZone.addEventListener(eventName, (event) => {
    event.preventDefault();
    dropZone.classList.add("is-dragging");
  });
});

["dragleave", "drop"].forEach((eventName) => {
  dropZone.addEventListener(eventName, (event) => {
    event.preventDefault();
    dropZone.classList.remove("is-dragging");
  });
});

dropZone.addEventListener("drop", (event) => {
  const file = [...event.dataTransfer.files].find(
    (candidate) => candidate.type === "application/pdf" || candidate.name.toLowerCase().endsWith(".pdf"),
  );
  if (!file) {
    showError("Drop a PDF file here.");
    return;
  }
  setFile(file);
  clearError();
});

window.addEventListener("dragover", (event) => event.preventDefault());
window.addEventListener("drop", (event) => event.preventDefault());

suggestedMonthButton.addEventListener("click", () => {
  monthInput.value = defaultMonth;
});

themeChoiceButtons.forEach((button) => {
  button.addEventListener("click", () => setThemeChoice(button.dataset.themeChoice));
});

layoutInputs.forEach((input) => {
  input.addEventListener("input", () => {
    updateDefaultsStatus();
    clearLayoutMessage();
  });
});

resetLayoutButton.addEventListener("click", () => {
  layoutInputs.forEach((input) => {
    input.value = input.dataset.default;
  });
  updateDefaultsStatus();
  showLayoutMessage("Restored the saved defaults.");
});

factoryLayoutButton.addEventListener("click", () => {
  layoutInputs.forEach((input) => {
    input.value = input.dataset.factory;
  });
  updateDefaultsStatus();
  showLayoutMessage("Original production values loaded. Save them to make them the defaults.");
});

saveLayoutDefaultsButton.addEventListener("click", saveLayoutDefaults);

form.addEventListener("submit", async (event) => {
  event.preventDefault();
  clearError();

  if (!selectedFile) {
    showError("Choose a roster PDF first.");
    fileInput.focus();
    return;
  }
  if (!selectedFile.name.toLowerCase().endsWith(".pdf")) {
    showError("The roster filename must end in .pdf.");
    return;
  }
  if (selectedFile.size > maximumUploadBytes) {
    showError(`The roster PDF must be ${maximumUploadMb} MB or smaller.`);
    return;
  }
  if (!form.reportValidity()) {
    return;
  }

  const formData = new FormData(form);
  formData.delete("roster");
  formData.append("roster", selectedFile, selectedFile.name);
  setBusy(true);

  try {
    const response = await fetch("/format", {
      method: "POST",
      body: formData,
    });
    if (!response.ok) {
      let message = "The roster could not be formatted.";
      try {
        const payload = await response.json();
        message = payload.error || message;
      } catch {
        // Keep the safe fallback for an unexpected non-JSON response.
      }
      throw new Error(message);
    }

    const blob = await response.blob();
    const filename = responseFilename(response);
    const saved = response.headers.get("X-Roster-Saved") === "true";
    if (resultUrl) {
      URL.revokeObjectURL(resultUrl);
    }
    resultUrl = URL.createObjectURL(blob);
    resultPreview.src = resultUrl;
    downloadResult.href = resultUrl;
    downloadResult.download = filename;
    resultName.textContent = saved
      ? `${filename} · saved in output/`
      : `${filename} · available for download (outside retention window)`;
    resultCard.hidden = false;
    await loadHistory();
    resultCard.focus({ preventScroll: true });
    resultCard.scrollIntoView({ behavior: "smooth", block: "start" });
  } catch (error) {
    showError(error.message || "The roster could not be formatted.");
    formMessage.scrollIntoView({ behavior: "smooth", block: "center" });
  } finally {
    setBusy(false);
  }
});

formatAnother.addEventListener("click", () => {
  setFile(null);
  resultCard.hidden = true;
  clearError();
  dropZone.scrollIntoView({ behavior: "smooth", block: "center" });
});

refreshHistoryButton.addEventListener("click", loadHistory);

if (retentionMonths === 0) {
  retentionNote.textContent = "Automatic roster cleanup is disabled.";
}

setThemeChoice(document.documentElement.dataset.theme, false);
updateDefaultsStatus();
loadHistory();