import { ClassValue, clsx } from "clsx";
import { twMerge } from "tailwind-merge";
import { SetLog } from "@prisma/client";

/**
 * Merge classnames using clsx and tailwind-merge
 */
export function cn(...inputs: ClassValue[]): string {
  return twMerge(clsx(inputs));
}

/**
 * Format a date to a readable string (e.g., "Feb 16, 2026")
 */
export function formatDate(date: Date | string): string {
  const dateObj = typeof date === "string" ? new Date(date) : date;
  return dateObj.toLocaleDateString("en-US", {
    year: "numeric",
    month: "short",
    day: "numeric",
  });
}

/**
 * Format weight with unit (e.g., "150 lbs")
 */
export function formatWeight(weight: number, unit: string): string {
  return `${weight} ${unit}`;
}

/**
 * Calculate total volume (sets * reps * weight)
 */
export function calculateVolume(sets: SetLog[]): number {
  return sets.reduce((total, set) => {
    const reps = set.reps || 0;
    const weight = set.weight || 0;
    return total + reps * weight;
  }, 0);
}

/**
 * Calculate estimated 1-rep max using Epley formula
 * 1RM = weight * (1 + reps / 30)
 */
export function calculateE1RM(weight: number, reps: number): number {
  if (reps === 1) return weight;
  return Math.round(weight * (1 + reps / 30) * 100) / 100;
}

/**
 * Get the start and end of a week for a given date
 */
export function getWeekRange(date: Date): { start: Date; end: Date } {
  const d = new Date(date);
  const day = d.getDay();
  const diff = d.getDate() - day + (day === 0 ? -6 : 1); // Adjust to Monday

  const start = new Date(d.setDate(diff));
  start.setHours(0, 0, 0, 0);

  const end = new Date(start);
  end.setDate(end.getDate() + 6);
  end.setHours(23, 59, 59, 999);

  return { start, end };
}

/**
 * Generate a random UUID
 */
export function generateId(): string {
  return crypto.randomUUID();
}