import type { HabitService } from "../habits/service";
import type { Schedule } from "../habits/contracts";

export type TodayHabit = ReturnType<HabitService["day"]>;
export type TodayResponse = {
  date: string;
  timezone: string;
  habits: TodayHabit[];
  due: number;
  completed: number;
};

export async function habitRequest<T>(
  path: string,
  options?: RequestInit,
): Promise<T> {
  const response = await fetch(`/api${path}`, options);
  if (!response.ok) {
    if (response.status === 401)
      throw new Error("Your session has expired. Sign in again to continue.");
    const body = await response.json().catch(() => null);
    throw new Error(
      (body?.error || "Could not reach your workspace. Please try again.") + (response.status >= 500 && body?.requestId ? ` Reference: ${body.requestId}` : ""),
    );
  }
  return response.status === 204
    ? (undefined as T)
    : (response.json() as Promise<T>);
}

export function scheduleLabel(schedule?: Schedule) {
  if (!schedule || schedule.type === "daily") return "Every day";
  if (schedule.type === "weekdays")
    return schedule.days
      .map((day) => ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"][day])
      .join(", ");
  if (schedule.type === "interval") return `Every ${schedule.every} days`;
  return `Every ${schedule.every === 1 ? "week" : `${schedule.every} weeks`} · ${["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"][schedule.weekday]}`;
}

export function formatTrackingDate(date: string) {
  return new Date(`${date}T12:00:00Z`).toLocaleDateString("en", {
    weekday: "long",
    month: "long",
    day: "numeric",
    timeZone: "UTC",
  });
}

/** Preserve unchanged row references when a background refresh returns new JSON objects. */
export function reconcileToday(current: TodayResponse | null, next: TodayResponse): TodayResponse {
  if (!current || current.date !== next.date || current.timezone !== next.timezone) return next;
  const previous = new Map(current.habits.map(habit => [habit.habitId, habit]));
  const habits = next.habits.map(habit => {
    const old = previous.get(habit.habitId);
    return old && JSON.stringify(old) === JSON.stringify(habit) ? old : habit;
  });
  if (current.due === next.due && current.completed === next.completed && habits.length === current.habits.length && habits.every((habit, index) => habit === current.habits[index])) return current;
  return { ...next, habits };
}