export function renderDatetime(template: string, value: DatetimeData, locale: LocaleData) {
  if (value === undefined) {
    return undefined;
  }

  const tokens: string[] = [];
  let hasText = false;
  FORMAT_KEYS.forEach((format, index) => {
    if (template.indexOf(format.f) > -1) {
      const token = '{' + index + '}';
      const text = renderTextFormat(format.f, (value as any)[format.k], value, locale);

      if (!hasText && text && (value as any)[format.k]) {
        hasText = true;
      }

      tokens.push(token, text);

      template = template.replace(format.f, token);
    }
  });

  if (!hasText) {
    return undefined;
  }

  for (let i = 0; i < tokens.length; i += 2) {
    template = template.replace(tokens[i], tokens[i + 1]);
  }

  return template;
}


export function renderTextFormat(format: string, value: any, date: DatetimeData|null, locale: LocaleData): string {

  if ((format === FORMAT_DDDD || format === FORMAT_DDD)) {
    try {
      value = (new Date(date!.year!, date!.month! - 1, date!.day)).getDay();

      if (format === FORMAT_DDDD) {
        return (locale.dayNames ? locale.dayNames : DAY_NAMES)[value];
      }

      return (locale.dayShortNames ? locale.dayShortNames : DAY_SHORT_NAMES)[value];

    } catch (e) {
      // ignore
    }

    return '';
  }

  if (format === FORMAT_A) {
    return date && date.hour ? date.hour < 12 ? 'AM' : 'PM' : value ? value.toUpperCase() : '';
  }

  if (format === FORMAT_a) {
    return date && date.hour ? date.hour < 12 ? 'am' : 'pm' : value ? value : '';
  }

  if (value == null) {
    return '';
  }

  if (format === FORMAT_YY || format === FORMAT_MM ||
      format === FORMAT_DD || format === FORMAT_HH ||
      format === FORMAT_mm || format === FORMAT_ss) {
    return twoDigit(value);
  }

  if (format === FORMAT_YYYY) {
    return fourDigit(value);
  }

  if (format === FORMAT_MMMM) {
    return (locale.monthNames ? locale.monthNames : MONTH_NAMES)[value - 1];
  }

  if (format === FORMAT_MMM) {
    return (locale.monthShortNames ? locale.monthShortNames : MONTH_SHORT_NAMES)[value - 1];
  }

  if (format === FORMAT_hh || format === FORMAT_h) {
    if (value === 0) {
      return '12';
    }
    if (value > 12) {
      value -= 12;
    }
    if (format === FORMAT_hh && value < 10) {
      return ('0' + value);
    }
  }

  return value.toString();
}


export function dateValueRange(format: string, min: DatetimeData, max: DatetimeData): any[] {
  const opts: any[] = [];

  if (format === FORMAT_YYYY || format === FORMAT_YY) {
    // year
    if (!max.year || !min.year) {
      throw new Error('min and max year is undefined');
    }

    for (let i = max.year - 1; i >= min.year; i--) {
      opts.push(i);
    }

  } else if (format === FORMAT_MMMM || format === FORMAT_MMM ||
             format === FORMAT_MM || format === FORMAT_M ||
             format === FORMAT_hh || format === FORMAT_h) {

    // month or 12-hour
    for (let i = 1; i < 13; i++) {
      opts.push(i);
    }

  } else if (format === FORMAT_DDDD || format === FORMAT_DDD ||
             format === FORMAT_DD || format === FORMAT_D) {
    // day
    for (let i = 1; i < 32; i++) {
      opts.push(i);
    }

  } else if (format === FORMAT_HH || format === FORMAT_H) {
    // 24-hour
    for (let i = 0; i < 24; i++) {
      opts.push(i);
    }

  } else if (format === FORMAT_mm || format === FORMAT_m) {
    // minutes
    for (let i = 0; i < 60; i++) {
      opts.push(i);
    }

  } else if (format === FORMAT_ss || format === FORMAT_s) {
    // seconds
    for (let i = 0; i < 60; i++) {
      opts.push(i);
    }

  } else if (format === FORMAT_A || format === FORMAT_a) {
    // AM/PM
    opts.push('am', 'pm');
  }

  return opts;
}

export function dateSortValue(year: number|undefined, month: number|undefined, day: number|undefined, hour = 0, minute = 0): number {
  return parseInt(`1${fourDigit(year)}${twoDigit(month)}${twoDigit(day)}${twoDigit(hour)}${twoDigit(minute)}`, 10);
}

export function dateDataSortValue(data: DatetimeData): number {
  if (data) {
    return dateSortValue(data.year, data.month, data.day, data.hour, data.minute);
  }
  return -1;
}

export function daysInMonth(month: number, year: number): number {
  return (month === 4 || month === 6 || month === 9 || month === 11) ? 30 : (month === 2) ? isLeapYear(year) ? 29 : 28 : 31;
}

export function isLeapYear(year: number): boolean {
  return (year % 4 === 0 && year % 100 !== 0) || (year % 400 === 0);
}


const ISO_8601_REGEXP = /^(\d{4}|[+\-]\d{6})(?:-(\d{2})(?:-(\d{2}))?)?(?:T(\d{2}):(\d{2})(?::(\d{2})(?:\.(\d{3}))?)?(?:(Z)|([+\-])(\d{2})(?::(\d{2}))?)?)?$/;
const TIME_REGEXP = /^((\d{2}):(\d{2})(?::(\d{2})(?:\.(\d{3}))?)?(?:(Z)|([+\-])(\d{2})(?::(\d{2}))?)?)?$/;

export function parseDate(val: any): DatetimeData|null {
  // manually parse IS0 cuz Date.parse cannot be trusted
  // ISO 8601 format: 1994-12-15T13:47:20Z
  let parse: any[]|null = null;

  if (val && val !== '') {
    // try parsing for just time first, HH:MM
    parse = TIME_REGEXP.exec(val);
    if (parse) {
      // adjust the array so it fits nicely with the datetime parse
      parse.unshift(undefined, undefined);
      parse[2] = parse[3] = undefined;

    } else {
      // try parsing for full ISO datetime
      parse = ISO_8601_REGEXP.exec(val);
    }
  }

  if (parse == null) {
    // wasn't able to parse the ISO datetime
    return null;
  }

  // ensure all the parse values exist with at least 0
  for (let i = 1; i < 8; i++) {
    parse[i] = (parse[i] !== undefined ? parseInt(parse[i], 10) : null);
  }

  let tzOffset = 0;
  if (parse[9] && parse[10]) {
    // hours
    tzOffset = parseInt(parse[10], 10) * 60;
    if (parse[11]) {
      // minutes
      tzOffset += parseInt(parse[11], 10);
    }
    if (parse[9] === '-') {
      // + or -
      tzOffset *= -1;
    }
  }

  return {
    year: parse[1],
    month: parse[2],
    day: parse[3],
    hour: parse[4],
    minute: parse[5],
    second: parse[6],
    millisecond: parse[7],
    tzOffset: tzOffset,
  };
}


export function updateDate(existingData: DatetimeData, newData: any): boolean {
  if (newData && newData !== '') {

    if (typeof newData === 'string') {
      // new date is a string, and hopefully in the ISO format
      // convert it to our DatetimeData if a valid ISO
      newData = parseDate(newData);
      if (newData) {
        // successfully parsed the ISO string to our DatetimeData
        Object.assign(existingData, newData);
        return true;
      }

    } else if ((newData.year || newData.hour || newData.month || newData.day || newData.minute || newData.second)) {
      // newData is from of a datetime picker's selected values
      // update the existing DatetimeData data with the new values

      // do some magic for 12-hour values
      if (newData.ampm && newData.hour) {
        newData.hour.value = (newData.ampm.value === 'pm')
          ? (newData.hour.value === 12 ? 12 : newData.hour.value + 12)
          : (newData.hour.value === 12 ? 0 : newData.hour.value);
      }

      // merge new values from the picker's selection
      // to the existing DatetimeData values
      for (const k in newData) {
        (existingData as any)[k] = newData[k].value;
      }

      return true;
    }

    // eww, invalid data
    console.warn(`Error parsing date: "${newData}". Please provide a valid ISO 8601 datetime format: https://www.w3.org/TR/NOTE-datetime`);

  } else {
    // blank data, clear everything out
    for (const k in existingData) {
      delete (existingData as any)[k];
    }
  }
  return false;
}


export function parseTemplate(template: string): string[] {
  const formats: string[] = [];

  template = template.replace(/[^\w\s]/gi, ' ');

  FORMAT_KEYS.forEach(format => {
    if (format.f.length > 1 && template.indexOf(format.f) > -1 && template.indexOf(format.f + format.f.charAt(0)) < 0) {
      template = template.replace(format.f, ' ' + format.f + ' ');
    }
  });

  const words = template.split(' ').filter(w => w.length > 0);
  words.forEach((word, i) => {
    FORMAT_KEYS.forEach(format => {
      if (word === format.f) {
        if (word === FORMAT_A || word === FORMAT_a) {
          // this format is an am/pm format, so it's an "a" or "A"
          if ((formats.indexOf(FORMAT_h) < 0 && formats.indexOf(FORMAT_hh) < 0) ||
              VALID_AMPM_PREFIX.indexOf(words[i - 1]) === -1) {
            // template does not already have a 12-hour format
            // or this am/pm format doesn't have a hour, minute, or second format immediately before it
            // so do not treat this word "a" or "A" as the am/pm format
            return;
          }
        }
        formats.push(word);
      }
    });
  });

  return formats;
}


export function getValueFromFormat(date: DatetimeData, format: string) {
  if (format === FORMAT_A || format === FORMAT_a) {
    return (date.hour! < 12 ? 'am' : 'pm');
  }
  if (format === FORMAT_hh || format === FORMAT_h) {
    return (date.hour! > 12 ? date.hour! - 12 : date.hour);
  }
  return (date as any)[convertFormatToKey(format)!];
}


export function convertFormatToKey(format: string): string|null {
  for (const k in FORMAT_KEYS) {
    if (FORMAT_KEYS[k].f === format) {
      return FORMAT_KEYS[k].k;
    }
  }
  return null;
}


export function convertDataToISO(data: DatetimeData): string {
  // https://www.w3.org/TR/NOTE-datetime
  let rtn = '';

  if (data) {
    if (data.year) {
      // YYYY
      rtn = fourDigit(data.year);

      if (data.month) {
        // YYYY-MM
        rtn += '-' + twoDigit(data.month);

        if (data.day) {
          // YYYY-MM-DD
          rtn += '-' + twoDigit(data.day);

          if (data.hour) {
            // YYYY-MM-DDTHH:mm:SS
            rtn += `T${twoDigit(data.hour)}:${twoDigit(data.minute)}:${twoDigit(data.second)}`;

            if (data.millisecond! > 0) {
              // YYYY-MM-DDTHH:mm:SS.SSS
              rtn += '.' + threeDigit(data.millisecond);
            }

            if (data.tzOffset == null || data.tzOffset === 0) {
              // YYYY-MM-DDTHH:mm:SSZ
              rtn += 'Z';

            } else {
              // YYYY-MM-DDTHH:mm:SS+/-HH:mm
              rtn += (data.tzOffset > 0 ? '+' : '-') + twoDigit(Math.floor(data.tzOffset / 60)) + ':' + twoDigit(data.tzOffset % 60);
            }
          }
        }
      }

    } else if (data.hour) {
      // HH:mm
      rtn = twoDigit(data.hour) + ':' + twoDigit(data.minute);

      if (data.second) {
        // HH:mm:SS
        rtn += ':' + twoDigit(data.second);

        if (data.millisecond) {
          // HH:mm:SS.SSS
          rtn += '.' + threeDigit(data.millisecond);
        }
      }
    }
  }

  return rtn;
}


/**
 * Use to convert a string of comma separated strings or
 * an array of strings, and clean up any user input
 */
export function convertToArrayOfStrings(input: string | string[] | undefined | null, type: string): string[]|undefined {
  if (!input) {
    return undefined;
  }

  if (typeof input === 'string') {
    // convert the string to an array of strings
    // auto remove any [] characters
    input = input.replace(/\[|\]/g, '').split(',');
  }

  let values: string[] | undefined = undefined;
  if (Array.isArray(input)) {
    // trim up each string value
    values = input.map(val => val.toString().trim());
  }

  if (!values || !values.length) {
    console.warn(`Invalid "${type}Names". Must be an array of strings, or a comma separated string.`);
  }

  return values;
}


/**
 * Use to convert a string of comma separated numbers or
 * an array of numbers, and clean up any user input
 */
export function convertToArrayOfNumbers(input: any[] | string | number, type: string): number[] {
  if (typeof input === 'string') {
    // convert the string to an array of strings
    // auto remove any whitespace and [] characters
    input = input.replace(/\[|\]|\s/g, '').split(',');
  }

  let values: number[];
  if (Array.isArray(input)) {
    // ensure each value is an actual number in the returned array
    values = input
      .map((num: any) => parseInt(num, 10))
      .filter(isFinite);
  } else {
    values = [input];
  }

  if (!values || !values.length) {
    console.warn(`Invalid "${type}Values". Must be an array of numbers, or a comma separated string of numbers.`);
  }

  return values;
}


function twoDigit(val: number | undefined): string {
  return ('0' + (val ? Math.abs(val) : '0')).slice(-2);
}

function threeDigit(val: number | undefined): string {
  return ('00' + (val ? Math.abs(val) : '0')).slice(-3);
}

function fourDigit(val: number | undefined): string {
  return ('000' + (val ? Math.abs(val) : '0')).slice(-4);
}


export interface DatetimeData {
  [key: string]: any;
  year?: number;
  month?: number;
  day?: number;
  hour?: number;
  minute?: number;
  second?: number;
  millisecond?: number;
  tzOffset?: number;
}


export interface LocaleData {
  monthNames?: string[];
  monthShortNames?: string[];
  dayNames?: string[];
  dayShortNames?: string[];
}


const FORMAT_YYYY = 'YYYY';
const FORMAT_YY = 'YY';
const FORMAT_MMMM = 'MMMM';
const FORMAT_MMM = 'MMM';
const FORMAT_MM = 'MM';
const FORMAT_M = 'M';
const FORMAT_DDDD = 'DDDD';
const FORMAT_DDD = 'DDD';
const FORMAT_DD = 'DD';
const FORMAT_D = 'D';
const FORMAT_HH = 'HH';
const FORMAT_H = 'H';
const FORMAT_hh = 'hh';
const FORMAT_h = 'h';
const FORMAT_mm = 'mm';
const FORMAT_m = 'm';
const FORMAT_ss = 'ss';
const FORMAT_s = 's';
const FORMAT_A = 'A';
const FORMAT_a = 'a';

const FORMAT_KEYS = [
  { f: FORMAT_YYYY, k: 'year' },
  { f: FORMAT_MMMM, k: 'month' },
  { f: FORMAT_DDDD, k: 'day' },
  { f: FORMAT_MMM, k: 'month' },
  { f: FORMAT_DDD, k: 'day' },
  { f: FORMAT_YY, k: 'year' },
  { f: FORMAT_MM, k: 'month' },
  { f: FORMAT_DD, k: 'day' },
  { f: FORMAT_HH, k: 'hour' },
  { f: FORMAT_hh, k: 'hour' },
  { f: FORMAT_mm, k: 'minute' },
  { f: FORMAT_ss, k: 'second' },
  { f: FORMAT_M, k: 'month' },
  { f: FORMAT_D, k: 'day' },
  { f: FORMAT_H, k: 'hour' },
  { f: FORMAT_h, k: 'hour' },
  { f: FORMAT_m, k: 'minute' },
  { f: FORMAT_s, k: 'second' },
  { f: FORMAT_A, k: 'ampm' },
  { f: FORMAT_a, k: 'ampm' },
];

const DAY_NAMES = [
  'Sunday',
  'Monday',
  'Tuesday',
  'Wednesday',
  'Thursday',
  'Friday',
  'Saturday',
];

const DAY_SHORT_NAMES = [
  'Sun',
  'Mon',
  'Tue',
  'Wed',
  'Thu',
  'Fri',
  'Sat',
];

const MONTH_NAMES = [
  'January',
  'February',
  'March',
  'April',
  'May',
  'June',
  'July',
  'August',
  'September',
  'October',
  'November',
  'December',
];

const MONTH_SHORT_NAMES = [
  'Jan',
  'Feb',
  'Mar',
  'Apr',
  'May',
  'Jun',
  'Jul',
  'Aug',
  'Sep',
  'Oct',
  'Nov',
  'Dec',
];

const VALID_AMPM_PREFIX = [
  FORMAT_hh, FORMAT_h, FORMAT_mm, FORMAT_m, FORMAT_ss, FORMAT_s
];