// Storefront widget for the Theme App Extension. Vanilla TS, no framework
// (IMPLEMENTATION_PLAN.md §1 sanctions "Preact or vanilla TS" — vanilla
// keeps the bundle tiny and avoids a runtime dependency for something this
// small). Bundled to ../assets/datetime-widget.js via esbuild
// (`npm run build:widget` at the repo root) — Theme App Extensions ship
// static assets as-is, there's no CLI build step for this extension type.
//
// The widget only *collects* a selection and writes it to cart attributes.
// It never enforces anything — that's the Validation Function's job
// (Phase 4), per CLAUDE.md's non-negotiable that enforcement is
// server-side. Losing network, JS, or an ad-blocker here should degrade to
// "no slot picked" (which the Function then rejects at checkout), not to a
// bypass.

type Method = "SHIPPING" | "LOCAL_DELIVERY" | "PICKUP";

interface SlotDto {
  date: string;
  startMin: number;
  endMin: number;
  capacity: number;
  remainingCapacity: number;
}

interface AvailabilityResponse {
  locationId: string;
  locationName: string;
  timezone: string;
  method: Method;
  dates: Record<string, SlotDto[]>;
  error?: string;
}

interface WidgetConfig {
  root: HTMLElement;
  heading: string;
  locationId: string | null;
  methods: Array<{ value: Method; label: string; attrLabel: string }>;
  labels: {
    chooseDate: string;
    chooseTime: string;
    noDates: string;
    confirmed: string;
    change: string;
    loading: string;
    error: string;
  };
}

const PROXY_BASE = "/apps/scheduling";

function minutesToDisplayTime(minutes: number): string {
  const h24 = Math.floor(minutes / 60);
  const m = minutes % 60;
  const period = h24 < 12 ? "AM" : "PM";
  const h12 = h24 % 12 === 0 ? 12 : h24 % 12;
  return `${h12}:${m.toString().padStart(2, "0")} ${period}`;
}

function formatDateLabel(dateIso: string): string {
  // Parsed as a plain calendar date (no timezone conversion) — this string
  // already represents the location-local calendar day from the API.
  const [year, month, day] = dateIso.split("-").map(Number);
  const date = new Date(Date.UTC(year, month - 1, day));
  return date.toLocaleDateString(undefined, { weekday: "short", month: "short", day: "numeric", timeZone: "UTC" });
}

function readConfig(root: HTMLElement): WidgetConfig {
  const d = root.dataset;
  const methods: WidgetConfig["methods"] = [];
  if (d.showShipping === "true") {
    methods.push({ value: "SHIPPING", label: d.labelShipping || "Shipping", attrLabel: d.attrLabelShipping || "Shipping date" });
  }
  if (d.showLocalDelivery === "true") {
    methods.push({
      value: "LOCAL_DELIVERY",
      label: d.labelLocalDelivery || "Local delivery",
      attrLabel: d.attrLabelLocalDelivery || "Delivery date",
    });
  }
  if (d.showPickup === "true") {
    methods.push({ value: "PICKUP", label: d.labelPickup || "Pickup", attrLabel: d.attrLabelPickup || "Pickup date" });
  }

  return {
    root,
    heading: d.heading || "",
    locationId: d.locationId || null,
    methods,
    labels: {
      chooseDate: d.labelChooseDate || "Choose a date",
      chooseTime: d.labelChooseTime || "Choose a time",
      noDates: d.labelNoDates || "No dates are available right now.",
      confirmed: d.labelConfirmed || "Confirmed for",
      change: d.labelChange || "Change",
      loading: d.labelLoading || "Loading available dates…",
      error: d.labelError || "Couldn't load available dates. Please try again.",
    },
  };
}

async function fetchAvailability(method: Method, locationId: string | null): Promise<AvailabilityResponse> {
  const params = new URLSearchParams({ method, days: "14" });
  if (locationId) params.set("locationId", locationId);
  const res = await fetch(`${PROXY_BASE}/availability?${params.toString()}`, {
    headers: { Accept: "application/json" },
  });
  const body = (await res.json()) as AvailabilityResponse;
  if (!res.ok) throw new Error(body.error || `Request failed (${res.status})`);
  return body;
}

interface HoldResponse {
  success: boolean;
  expiresAt?: number;
  error?: string;
}

async function getCartToken(): Promise<string> {
  const res = await fetch("/cart.js", { headers: { Accept: "application/json" } });
  const cart = (await res.json()) as { token: string };
  return cart.token;
}

async function requestHold(params: {
  intent: "create" | "release";
  locationId: string;
  method: Method;
  date: string;
  startMin: number;
  cartToken: string;
}): Promise<HoldResponse> {
  const res = await fetch(`${PROXY_BASE}/hold`, {
    method: "POST",
    headers: { "Content-Type": "application/json", Accept: "application/json" },
    body: JSON.stringify(params),
  });
  const body = (await res.json()) as HoldResponse;
  if (!res.ok && params.intent === "create") return { success: false, error: body.error || "Slot unavailable" };
  return body;
}

async function writeCartAttribute(key: string, machine: Record<string, string>, display: string): Promise<void> {
  await fetch("/cart/update.js", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ attributes: { [key]: display, ...machine } }),
  });
}

class DateTimeWidget {
  private config: WidgetConfig;
  private el = {
    heading: document.createElement("h3"),
    methodRow: document.createElement("div"),
    dateRow: document.createElement("div"),
    timeRow: document.createElement("div"),
    status: document.createElement("p"),
    confirmation: document.createElement("div"),
  };
  private selectedMethod: WidgetConfig["methods"][number] | null = null;
  private selectedDate: string | null = null;
  private availability: AvailabilityResponse | null = null;
  private heldSlot: { locationId: string; method: Method; date: string; startMin: number; cartToken: string } | null =
    null;

  constructor(config: WidgetConfig) {
    this.config = config;
  }

  mount() {
    const { root, heading, methods } = this.config;
    root.classList.add("dd-widget--ready");
    root.innerHTML = "";

    if (methods.length === 0) return; // merchant disabled every method — render nothing

    if (heading) {
      this.el.heading.className = "dd-widget__heading";
      this.el.heading.textContent = heading;
      root.appendChild(this.el.heading);
    }

    this.el.methodRow.className = "dd-widget__row dd-widget__methods";
    this.el.dateRow.className = "dd-widget__row dd-widget__dates";
    this.el.timeRow.className = "dd-widget__row dd-widget__times";
    this.el.status.className = "dd-widget__status";
    this.el.confirmation.className = "dd-widget__confirmation";
    this.el.confirmation.hidden = true;

    root.append(this.el.confirmation, this.el.methodRow, this.el.dateRow, this.el.timeRow, this.el.status);

    if (methods.length === 1) {
      this.selectMethod(methods[0]);
    } else {
      this.renderMethods();
    }
  }

  private renderMethods() {
    this.el.methodRow.innerHTML = "";
    for (const method of this.config.methods) {
      const button = document.createElement("button");
      button.type = "button";
      button.className = "dd-widget__pill";
      button.textContent = method.label;
      button.setAttribute("aria-pressed", String(this.selectedMethod?.value === method.value));
      button.addEventListener("click", () => this.selectMethod(method));
      this.el.methodRow.appendChild(button);
    }
  }

  private async selectMethod(method: WidgetConfig["methods"][number]) {
    this.selectedMethod = method;
    this.selectedDate = null;
    this.el.timeRow.innerHTML = "";
    this.el.confirmation.hidden = true;
    if (this.config.methods.length > 1) this.renderMethods();

    this.el.status.textContent = this.config.labels.loading;
    this.el.dateRow.innerHTML = "";

    try {
      this.availability = await fetchAvailability(method.value, this.config.locationId);
      this.renderDates();
    } catch {
      this.el.status.textContent = this.config.labels.error;
    }
  }

  private renderDates() {
    const dates = Object.keys(this.availability?.dates ?? {}).sort();
    this.el.dateRow.innerHTML = "";

    if (dates.length === 0) {
      this.el.status.textContent = this.config.labels.noDates;
      return;
    }

    this.el.status.textContent = this.config.labels.chooseDate;
    for (const date of dates) {
      const button = document.createElement("button");
      button.type = "button";
      button.className = "dd-widget__pill";
      button.textContent = formatDateLabel(date);
      button.setAttribute("aria-pressed", String(this.selectedDate === date));
      button.addEventListener("click", () => this.selectDate(date));
      this.el.dateRow.appendChild(button);
    }
  }

  private selectDate(date: string) {
    this.selectedDate = date;
    for (const child of Array.from(this.el.dateRow.children)) {
      child.setAttribute("aria-pressed", String(child.textContent === formatDateLabel(date)));
    }

    const slots = this.availability?.dates[date] ?? [];
    this.el.timeRow.innerHTML = "";
    this.el.status.textContent = this.config.labels.chooseTime;

    for (const slot of slots) {
      const button = document.createElement("button");
      button.type = "button";
      button.className = "dd-widget__pill";
      button.textContent = `${minutesToDisplayTime(slot.startMin)}–${minutesToDisplayTime(slot.endMin)}`;
      button.addEventListener("click", () => this.selectSlot(date, slot));
      this.el.timeRow.appendChild(button);
    }
  }

  private async selectSlot(date: string, slot: SlotDto) {
    const method = this.selectedMethod!;
    const availability = this.availability!;
    const display = `${formatDateLabel(date)}, ${minutesToDisplayTime(slot.startMin)}–${minutesToDisplayTime(slot.endMin)}`;

    this.el.status.textContent = this.config.labels.loading;

    try {
      const cartToken = await getCartToken();

      // Reserve capacity FIRST. Writing the cart attribute alone would just
      // be two shoppers racing to write the same free-text field — nothing
      // would stop both checkouts from completing for the last slot. The
      // hold is what the Validation Function (Phase 4) actually enforces
      // against at checkout.
      const hold = await requestHold({
        intent: "create",
        locationId: availability.locationId,
        method: method.value,
        date,
        startMin: slot.startMin,
        cartToken,
      });

      if (!hold.success) {
        this.el.status.textContent = this.config.labels.error;
        // The slot we just tried is gone — refresh so the list reflects reality.
        await this.selectMethod(method);
        return;
      }

      this.heldSlot = { locationId: availability.locationId, method: method.value, date, startMin: slot.startMin, cartToken };

      await writeCartAttribute(
        method.attrLabel,
        {
          dd_method: method.value,
          dd_date: date,
          dd_start_min: String(slot.startMin),
          dd_end_min: String(slot.endMin),
          dd_location_id: availability.locationId,
        },
        display,
      );

      this.el.status.textContent = "";
      this.el.methodRow.hidden = true;
      this.el.dateRow.hidden = true;
      this.el.timeRow.hidden = true;
      this.el.confirmation.hidden = false;
      this.el.confirmation.innerHTML = "";

      const summary = document.createElement("p");
      summary.textContent = `${this.config.labels.confirmed} ${display}`;
      const changeButton = document.createElement("button");
      changeButton.type = "button";
      changeButton.className = "dd-widget__link";
      changeButton.textContent = this.config.labels.change;
      changeButton.addEventListener("click", () => {
        if (this.heldSlot) {
          void requestHold({ intent: "release", ...this.heldSlot });
          this.heldSlot = null;
        }
        this.el.methodRow.hidden = false;
        this.el.dateRow.hidden = false;
        this.el.timeRow.hidden = false;
        this.el.confirmation.hidden = true;
      });

      this.el.confirmation.append(summary, changeButton);
    } catch {
      this.el.status.textContent = this.config.labels.error;
    }
  }
}

function init() {
  const roots = document.querySelectorAll<HTMLElement>("[data-dd-widget]");
  roots.forEach((root) => {
    new DateTimeWidget(readConfig(root)).mount();
  });
}

if (document.readyState === "loading") {
  document.addEventListener("DOMContentLoaded", init);
} else {
  init();
}