import 'dart:core';

// Run in console on http://www.kumamotokokufu-h.ed.jp/kumamoto/bungaku/nengoui.html
// Array.from(document.querySelectorAll('table')[1].querySelectorAll('tr')).slice(1).map(row => `DateTime(${row.children[3 + (row.children.length == 7)].innerHTML.replace(/～.*/, '')}, ${row.children[4 + (row.children.length == 7)].innerHTML.replace('/', ', ')}): '${row.children[2 + (row.children.length == 7)].innerHTML}'`).join('\n')

const Map<(int, int, int), String> periodsBeforeNanbokuchou = {
  (645, 6, 19): '大化',
  (650, 2, 15): '白雉',
  (686, 7, 20): '朱鳥',
  (701, 3, 21): '大宝',
  (704, 5, 10): '慶雲',
  (708, 1, 11): '和銅',
  (715, 9, 2): '霊亀',
  (717, 11, 17): '養老',
  (724, 2, 4): '神亀',
  (729, 8, 5): '天平',
  (749, 4, 14): '天平感宝',
  (749, 7, 2): '天平勝宝',
  (757, 8, 18): '天平宝字',
  (765, 1, 7): '天平神護',
  (767, 8, 16): '神護景雲',
  (770, 10, 1): '宝亀',
  (781, 1, 1): '天応',
  (782, 8, 19): '延暦',
  (806, 5, 18): '大同',
  (810, 9, 19): '弘仁',
  (824, 1, 5): '天長',
  (834, 1, 3): '承和',
  (848, 6, 13): '嘉祥',
  (851, 4, 28): '仁寿',
  (854, 11, 30): '斎衡',
  (857, 2, 21): '天安',
  (859, 4, 15): '貞観',
  (877, 4, 16): '元慶',
  (885, 2, 21): '仁和',
  (889, 4, 27): '寛平',
  (898, 4, 26): '昌泰',
  (901, 7, 15): '延喜',
  (923, 4, 11): '延長',
  (931, 4, 26): '承平',
  (938, 5, 22): '天慶',
  (947, 4, 22): '天暦',
  (957, 10, 27): '天徳',
  (961, 2, 16): '応和',
  (964, 7, 10): '康保',
  (968, 8, 13): '安和',
  (970, 3, 25): '天禄',
  (973, 12, 20): '天延',
  (976, 7, 13): '貞元',
  (978, 11, 29): '天元',
  (983, 4, 15): '永観',
  (985, 4, 27): '寛和',
  (987, 4, 5): '永延',
  (989, 8, 8): '永祚',
  (990, 11, 7): '正暦',
  (995, 2, 22): '長徳',
  (999, 1, 13): '長保',
  (1004, 7, 20): '寛弘',
  (1012, 12, 25): '長和',
  (1017, 4, 23): '寛仁',
  (1021, 2, 2): '治安',
  (1024, 7, 13): '万寿',
  (1028, 7, 25): '長元',
  (1037, 4, 21): '長暦',
  (1040, 11, 10): '長久',
  (1044, 11, 24): '寛徳',
  (1046, 4, 14): '永承',
  (1053, 1, 11): '天喜',
  (1058, 8, 29): '康平',
  (1065, 8, 2): '治暦',
  (1069, 4, 13): '延久',
  (1074, 8, 23): '承保',
  (1077, 11, 17): '承暦',
  (1081, 2, 10): '永保',
  (1084, 2, 7): '応徳',
  (1087, 4, 7): '寛治',
  (1094, 12, 15): '嘉保',
  (1096, 12, 17): '永長',
  (1097, 11, 21): '承徳',
  (1099, 8, 28): '康和',
  (1104, 2, 10): '長治',
  (1106, 4, 9): '嘉承',
  (1108, 8, 3): '天仁',
  (1110, 7, 13): '天永',
  (1113, 7, 13): '永久',
  (1118, 4, 3): '元永',
  (1120, 4, 10): '保安',
  (1124, 4, 3): '天治',
  (1126, 1, 22): '大治',
  (1131, 1, 29): '天承',
  (1132, 8, 11): '長承',
  (1135, 4, 27): '保延',
  (1141, 7, 10): '永治',
  (1142, 4, 28): '康治',
  (1144, 2, 23): '天養',
  (1145, 7, 22): '久安',
  (1151, 1, 26): '仁平',
  (1154, 10, 28): '久寿',
  (1156, 4, 27): '保元',
  (1159, 4, 20): '平治',
  (1160, 1, 10): '永暦',
  (1161, 9, 4): '応保',
  (1163, 3, 29): '長寛',
  (1165, 6, 5): '永万',
  (1166, 8, 27): '仁安',
  (1169, 4, 8): '嘉応',
  (1171, 4, 21): '承安',
  (1175, 7, 28): '安元',
  (1177, 8, 4): '治承',
  (1181, 7, 14): '養和',
  (1182, 5, 27): '寿永',
  (1184, 4, 16): '元暦',
  (1185, 8, 14): '文治',
  (1190, 4, 11): '建久',
  (1199, 4, 27): '正治',
  (1201, 2, 13): '建仁',
  (1204, 2, 20): '元久',
  (1206, 4, 27): '建永',
  (1207, 10, 25): '承元',
  (1211, 3, 9): '建暦',
  (1213, 12, 6): '建保',
  (1219, 4, 12): '承久',
  (1222, 4, 13): '貞応',
  (1224, 11, 20): '元仁',
  (1225, 4, 20): '嘉禄',
  (1227, 12, 10): '安貞',
  (1229, 3, 5): '寛喜',
  (1232, 4, 2): '貞永',
  (1233, 4, 15): '天福',
  (1234, 11, 5): '文暦',
  (1235, 9, 19): '嘉禎',
  (1238, 11, 23): '暦仁',
  (1239, 2, 7): '延応',
  (1240, 7, 16): '仁治',
  (1243, 2, 26): '寛元',
  (1247, 2, 28): '宝治',
  (1249, 3, 18): '建長',
  (1256, 10, 5): '康元',
  (1257, 3, 14): '正嘉',
  (1259, 3, 26): '正元',
  (1260, 4, 13): '文応',
  (1261, 2, 20): '弘長',
  (1264, 2, 28): '文永',
  (1275, 4, 25): '建治',
  (1278, 2, 29): '弘安',
  (1288, 4, 28): '正応',
  (1293, 8, 5): '永仁',
  (1299, 4, 25): '正安',
  (1302, 11, 21): '乾元',
  (1303, 8, 5): '嘉元',
  (1306, 12, 14): '徳治',
  (1308, 10, 9): '延慶',
  (1311, 4, 28): '応長',
  (1312, 3, 20): '正和',
  (1317, 2, 3): '文保',
  (1319, 4, 28): '元応',
  (1321, 2, 23): '元亨',
  (1324, 12, 9): '正中',
  (1326, 4, 26): '嘉暦',
};

const Map<(int, int, int), String> periodsNanbokuchouNorth = {
  (1329, 8, 29): '元徳',
  (1332, 4, 28): '正慶',
  (1334, 1, 29): '建武',
  (1338, 8, 28): '暦応',
  (1342, 4, 27): '康永',
  (1345, 10, 21): '貞和',
  (1350, 2, 27): '観応',
  (1352, 9, 27): '文和',
  (1356, 3, 28): '延文',
  (1361, 3, 29): '康安',
  (1362, 9, 23): '貞治',
  (1368, 2, 18): '応安',
  (1375, 2, 27): '永和',
  (1379, 3, 22): '康暦',
  (1381, 2, 24): '永徳',
  (1384, 2, 27): '至徳',
  (1387, 8, 23): '嘉慶',
  (1389, 2, 9): '康応',
  (1390, 3, 26): '明徳',
};

const Map<(int, int, int), String> periodsNanbokuchouSouth = {
  (1329, 8, 29): '元徳',
  (1331, 8, 9): '元弘',
  (1334, 1, 29): '建武',
  (1336, 2, 29): '延元',
  (1340, 4, 28): '興国',
  (1346, 12, 8): '正平',
  (1370, 7, 24): '建徳',
  (1372, 4, 4): '文中',
  (1375, 5, 27): '天授',
  (1381, 2, 10): '弘和',
  (1384, 4, 28): '元中',
};

const Map<(int, int, int), String> periodsAfterNanbokuchou = {
  // (1392, ): '室町時代',
  (1394, 7, 5): '応永',
  (1428, 4, 27): '正長',
  (1429, 9, 5): '永享',
  (1441, 2, 17): '嘉吉',
  (1444, 2, 5): '文安',
  (1449, 7, 28): '宝徳',
  (1452, 7, 25): '享徳',
  (1455, 7, 25): '康正',
  (1457, 9, 28): '長禄',
  (1460, 12, 21): '寛正',
  (1466, 2, 28): '文正',
  (1467, 3, 5): '応仁',
  (1469, 4, 28): '文明',
  (1487, 7, 20): '長享',
  (1489, 8, 21): '延徳',
  (1492, 7, 19): '明応',
  (1501, 2, 29): '文亀',
  (1504, 2, 30): '永正',
  (1521, 8, 23): '大永',
  (1528, 8, 20): '享禄',
  (1532, 7, 29): '天文',
  (1555, 10, 23): '弘治',
  (1558, 2, 28): '永禄',
  (1570, 4, 23): '元亀',
  (1573, 7, 28): '天正',
  (1592, 12, 8): '文禄',
  (1596, 10, 27): '慶長',
  (1615, 7, 13): '元和',
  (1624, 2, 30): '寛永',
  (1644, 12, 16): '正保',
  (1648, 2, 15): '慶安',
  (1652, 9, 18): '承応',
  (1655, 4, 13): '明暦',
  (1658, 7, 23): '万治',
  (1661, 4, 25): '寛文',
  (1673, 9, 21): '延宝',
  (1681, 9, 29): '天和',
  (1684, 2, 21): '貞享',
  (1688, 9, 30): '元禄',
  (1704, 3, 13): '宝永',
  (1711, 4, 25): '正徳',
  (1716, 6, 22): '享保',
  (1736, 4, 28): '元文',
  (1741, 2, 27): '寛保',
  (1744, 2, 21): '延享',
  (1748, 7, 12): '寛延',
  (1751, 10, 27): '宝暦',
  (1764, 6, 2): '明和',
  (1772, 11, 16): '安永',
  (1781, 4, 2): '天明',
  (1789, 1, 25): '寛政',
  (1801, 2, 5): '享和',
  (1804, 2, 11): '文化',
  (1818, 4, 22): '文政',
  (1830, 12, 10): '天保',
  (1844, 12, 2): '弘化',
  (1848, 2, 28): '嘉永',
  (1854, 11, 27): '安政',
  (1860, 3, 18): '万延',
  (1861, 2, 19): '文久',
  (1864, 2, 20): '元治',
  (1865, 4, 7): '慶応',
  (1868, 9, 8): '明治',
  (1912, 7, 30): '大正',
  (1926, 12, 25): '昭和',
  (1989, 1, 8): '平成',
  (2019, 5, 1): '令和',
};

extension on DateTime {
  /// Note: In the years between 1336 and 1392, Japan was split in two
  /// because of an ongoing conflict. As a result, Japan has two timelines
  /// during these years. Unless you turn off [nanbokuchouPeriodUsesNorth],
  /// function will give you the timeline from the northern part of Japan
  /// as a default.
  ///
  /// See more info here:
  /// - https://en.wikipedia.org/wiki/Nanboku-ch%C5%8D_period
  /// - http://www.kumamotokokufu-h.ed.jp/kumamoto/bungaku/nengoui.html
  String? japaneseEra() {
    throw UnimplementedError('This function is not implemented yet.');

    if (year < 645) {
      return null;
    }

    if (year < periodsNanbokuchouNorth.keys.first.$1) {
      // TODO: find first where year <= this.year and jump one period back.
    }
  }

  String get japaneseWeekdayPrefix =>
      ['月', '火', '水', '木', '金', '土', '日'][weekday - 1];

  /// Returns the date in Japanese format.
  String japaneseDate({bool showWeekday = false}) =>
      '$month月$day日${showWeekday ? '（$japaneseWeekdayPrefix）' : ''}';
}