import { db } from "@epicure/db";
import { tierDefinitions, userUsage } from "@epicure/db";
import { eq, and, sql } from "@epicure/db";

function currentMonth() {
  const now = new Date();
  return `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, "0")}`;
}

export type LimitKey = "recipe" | "aiCall" | "storage";

export class TierLimitError extends Error {
  constructor(public readonly limit: LimitKey, public readonly tier: string) {
    super(`Tier limit reached: ${limit} (tier: ${tier})`);
    this.name = "TierLimitError";
  }
}

export async function checkTierLimit(
  userId: string,
  userTier: "free" | "pro",
  key: LimitKey
): Promise<void> {
  const [tierDef] = await db
    .select()
    .from(tierDefinitions)
    .where(eq(tierDefinitions.tier, userTier));

  if (!tierDef) return;

  const month = currentMonth();
  const [usage] = await db
    .select()
    .from(userUsage)
    .where(and(eq(userUsage.userId, userId), eq(userUsage.month, month)));

  const current = usage ?? {
    aiCallsUsed: 0,
    recipeCount: 0,
    storageUsedMb: 0,
  };

  if (key === "recipe" && current.recipeCount >= tierDef.maxRecipes) {
    throw new TierLimitError("recipe", userTier);
  }
  if (key === "aiCall" && current.aiCallsUsed >= tierDef.aiCallsPerMonth) {
    throw new TierLimitError("aiCall", userTier);
  }
}

export async function incrementUsage(
  userId: string,
  key: LimitKey,
  amount = 1
): Promise<void> {
  const month = currentMonth();
  const id = `${userId}-${month}`;

  const initialValues = {
    id,
    userId,
    month,
    aiCallsUsed: key === "aiCall" ? amount : 0,
    recipeCount: key === "recipe" ? amount : 0,
    storageUsedMb: key === "storage" ? amount : 0,
  };

  const incrementSet =
    key === "aiCall"
      ? { aiCallsUsed: sql`${userUsage.aiCallsUsed} + ${amount}` }
      : key === "recipe"
        ? { recipeCount: sql`${userUsage.recipeCount} + ${amount}` }
        : { storageUsedMb: sql`${userUsage.storageUsedMb} + ${amount}` };

  await db
    .insert(userUsage)
    .values(initialValues)
    .onConflictDoUpdate({
      target: [userUsage.userId, userUsage.month],
      set: incrementSet,
    });
}