import type { TimeInterval } from "../models/common";
import { addDays, addMonths, addYears, formatDate, startOfDay, startOfMonth, startOfWeek, startOfYear } from "./date";

export default function parseInterval(s: string, date: Date): TimeInterval<Date> {
  const [verb, args] = s.split(":")
  
  switch (verb) {
    case "":
    case "all_time":
      return null;
    case "next": {
      const [amount, unit] = unitNumber(args);
      switch (unit) {
        case "d": case "days":
          return {display: "days", min: startOfDay(date), max: startOfDay(addDays(date, amount))}
        case "w": case "weeks":
          return {display: "days", min: startOfDay(date), max: startOfDay(addDays(date, amount * 7))}
        case "m": case "months":
          return {display: "days", min: startOfDay(date), max: startOfDay(addMonths(date, amount))}
        case "y": case "years":
          return {display: "none", min: startOfDay(date), max: startOfDay(addYears(date, amount))}
      }
    }
    case "last": {
      const [amount, unit] = unitNumber(args);
      switch (unit) {
        case "d": case "days":
          return {display: "days", min: startOfDay(addDays(date, -amount)), max: startOfDay(addDays(date, 1))}
        case "w": case "weeks":
          return {display: "weeks", min: startOfDay(addDays(date, -amount * 7)), max: startOfDay(addDays(date, 1))}
        case "m": case "months":
          return {display: "days", min: startOfDay(addMonths(date, -amount)), max: startOfDay(addDays(date, 1))}
        case "y": case "years":
          return {display: "none", min: startOfDay(addYears(date, -amount)), max: startOfDay(addDays(date, 1))}
      }
    }
    case "today":
      return {display: "none", min: startOfDay(date), max: startOfDay(addDays(date, 1))}
    case "next_week":
      return {display: "weeks", min: startOfWeek(addDays(date, 7)), max: startOfWeek(addDays(date, 14))}  
    case "this_week":
      return {display: "weeks", min: startOfWeek(date), max: startOfWeek(addDays(date, 7))}
    case "last_week":
      return {display: "weeks", min: startOfWeek(addDays(date, -7)), max: startOfWeek(date)}  
    case "next_month":
      return {display: "month", min: startOfMonth(addMonths(date, 1)), max: startOfMonth(addMonths(date, 2))}
    case "this_month":
      return {display: "month", min: startOfMonth(date), max: startOfMonth(addMonths(date, 1))}
    case "last_month":
      return {display: "month", min: startOfMonth(addMonths(date, -1)), max: startOfMonth(date)}
    case "next_year":
      return {display: "year", min: startOfYear(addYears(date, 1)), max: startOfYear(addYears(date, 2))}
    case "this_year":
      return {display: "year", min: startOfYear(date), max: startOfYear(addYears(date, 1))}
    case "last_year":
      return {display: "year", min: startOfYear(addYears(date, -1)), max: startOfYear(date)}
  }
}

export function intervalLabel(s: string): string {
  const [verb, args] = s.split(":")
  
  switch (verb) {
    case "":
      return "All time";
    case "next":
    case "last": {
      const [amount, unit] = unitNumber(args);
      switch (unit) {
        case "d": case "days":
          return `${capitalize(verb)} ${amount} ${amount !== 1 ? "days" : "day"}`
        case "w": case "weeks":
          return `${capitalize(verb)} ${amount} ${amount !== 1 ? "weeks" : "week"}`
        case "m": case "months":
          return `${capitalize(verb)} ${amount} ${amount !== 1 ? "months" : "month"}`
        case "y": case "years":
          return `${capitalize(verb)} ${amount} ${amount !== 1 ? "years" : "year"}`
      }
    }
    case "today":
      return verb;
    case "all_time":
    case "next_week":
    case "this_week":
    case "last_week":
    case "next_month":
    case "this_month":
    case "last_month":
    case "next_year":
    case "this_year":
    case "last_year":
      return capitalize(verb.replace("_", " "));
  }
}

export function datesOf(interval: TimeInterval<string | Date>): TimeInterval<string> {
  if (interval == null) {
    return void(0)
  }
  
  return {min: formatDate(interval.min), max: formatDate(interval.max)}
}

function capitalize(s: string) {
  return `${s.charAt(0).toLocaleUpperCase()}${s.slice(1)}`
}

function unitNumber(s: string): [number, string] {  
  for (let i = 0; i < s.length; ++i) {
    const ch = s.charAt(i);

    if (ch < '0' || ch > '9') {
      return [parseInt(s.slice(0, i)), s.slice(i)]
    }
  }

  return [parseInt(s), ""];
}