export function timeSince(dateString: string): string {
  if (!dateString) {
    return "";
  }

  const d = new Date(dateString.endsWith("Z") ? dateString : `${dateString}Z`);
  if (Number.isNaN(d.getTime())) {
    return "";
  }

  const diffMs = Date.now() - d.getTime();
  const mins = Math.floor(diffMs / 60000);

  if (mins < 1) {
    return "just now";
  }
  if (mins < 60) {
    return `${mins}m ago`;
  }

  const hours = Math.floor(mins / 60);
  if (hours < 24) {
    return `${hours}h ago`;
  }

  const days = Math.floor(hours / 24);
  if (days < 7) {
    return `${days}d ago`;
  }

  return `${Math.floor(days / 7)}w ago`;
}

export function timeBetween(startStr: string, endStr: string): string {
  if (!startStr || !endStr) {
    return "";
  }

  const start = new Date(startStr.endsWith("Z") ? startStr : `${startStr}Z`);
  const end = new Date(endStr.endsWith("Z") ? endStr : `${endStr}Z`);

  if (Number.isNaN(start.getTime()) || Number.isNaN(end.getTime())) {
    return "";
  }

  const diffMs = end.getTime() - start.getTime();
  const mins = Math.floor(diffMs / 60000);

  if (mins < 60) {
    return `${mins}m`;
  }

  const hours = Math.floor(mins / 60);
  if (hours < 24) {
    return `${hours}h`;
  }

  return `${Math.floor(hours / 24)}d`;
}

export function waitTimeColor(dateString: string): "green" | "yellow" | "red" | "" {
  if (!dateString) {
    return "";
  }

  const d = new Date(dateString.endsWith("Z") ? dateString : `${dateString}Z`);
  const hours = (Date.now() - d.getTime()) / 3600000;

  if (hours < 4) {
    return "green";
  }
  if (hours < 24) {
    return "yellow";
  }

  return "red";
}

export function formatDateTime(value: string): string {
  if (!value) {
    return "";
  }

  const normalized = value.endsWith("Z") ? value : `${value}Z`;
  const date = new Date(normalized);

  if (Number.isNaN(date.getTime())) {
    return value;
  }

  const datePart = date.toLocaleDateString("en-CA");
  const timePart = date.toLocaleTimeString(undefined, {
    hour: "2-digit",
    minute: "2-digit",
    hour12: false,
  });
  const tz = date.toLocaleTimeString(undefined, { timeZoneName: "short" }).split(" ").pop();

  return `${datePart} ${timePart} ${tz ?? ""}`.trim();
}

export function getWaitTimeTextClass(color: "green" | "yellow" | "red" | ""): string | undefined {
  if (color === "green") {
    return "text-green-600";
  }
  if (color === "yellow") {
    return "text-yellow-600";
  }
  if (color === "red") {
    return "text-red-600";
  }
  return undefined;
}

export function toDateInputValue(value: string | null | undefined): string {
  if (!value) {
    return "";
  }
  return value.split("T")[0] ?? value;
}

export function toDateTimeLocalInputValue(value: string | null | undefined): string {
  if (!value) {
    return "";
  }

  const date = new Date(value);
  if (Number.isNaN(date.getTime())) {
    return "";
  }

  const pad = (part: number) => String(part).padStart(2, "0");

  return [
    date.getFullYear(),
    "-",
    pad(date.getMonth() + 1),
    "-",
    pad(date.getDate()),
    "T",
    pad(date.getHours()),
    ":",
    pad(date.getMinutes()),
  ].join("");
}