defmodule PrefectureJp do
    @moduledoc """
    PrefectureJp is a library for converting the Japanese prefecture code and
    Japanese prefecture name.
    """

    defmodule Prefecture do
        @moduledoc """
        A struct responsible to hold prefecture information.
        """

        defstruct code: nil, name: nil, name_e: nil, name_h: nil, name_k: nil, area: nil
        @type t :: %__MODULE__{
            code: String.t, name: String.t, name_e: String.t,
            name_h: String.t, name_k: String.t, area: String.t
        }
    end

    @doc false
    defmacro __using__(colmun) do
        quote do
            @spec prefecture(PrefectureJp.Prefecture.t, String.t) :: any
            def prefecture(struct, key) do
                Map.fetch!(struct, unquote(colmun))
                |> PrefectureJp.find
                |> Map.fetch!(key)
            end
        end
    end

    @doc ~S"""
    ## Examples

        iex> PrefectureJp.find("13").name
        "東京都"

        iex> PrefectureJp.find(code: "13").name
        "東京都"

        iex> PrefectureJp.find(name: "東京都").code
        "13"

        iex> PrefectureJp.find(name: "TOKYO").code
        "13"

        iex> PrefectureJp.find(name: "tokyo").code
        "13"

        iex> PrefectureJp.find(name: "トウキョウト").code
        "13"

        iex> PrefectureJp.find(name: "とうきょうと").code
        "13"

        iex> PrefectureJp.find("48")
        nil

        iex> PrefectureJp.find(code: "48")
        nil

        iex> PrefectureJp.find(name: "ワシントン")
        nil
    """
    @spec find(String.t) :: any
    def find(code) when is_binary(code) do
        all
        |> Enum.find(fn(pref) -> pref.code == code end)
    end

    @spec find([{atom, String.t}]) :: any
    def find([{:code, code}|_]) when is_binary(code) do
        find code
    end

    @spec find([{atom, String.t}]) :: any
    def find([{:name, name}|_]) when is_binary(name) do
        dname = String.downcase(name)

        all
        |> Enum.find(fn(pref) ->
            Enum.any? [
                String.starts_with?(pref.name,   dname),
                String.starts_with?(pref.name_e, dname),
                String.starts_with?(pref.name_h, dname),
                String.starts_with?(pref.name_k, dname),
            ]
        end)
    end

    @spec find(any) :: any
    def find(_) do
        nil
    end

    @spec all() :: [struct]
    def all do
        [
            %Prefecture {
                code: "01",
                name: "北海道",
                name_e: "hokkaido",
                name_h: "ほっかいどう",
                name_k: "ホッカイドウ",
                area: "北海道"
            },
            %Prefecture {
                code: "02",
                name: "青森県",
                name_e: "aomori",
                name_h: "あおもりけん",
                name_k: "アオモリケン",
                area: "東北"
            },
            %Prefecture {
                code: "03",
                name: "岩手県",
                name_e: "iwate",
                name_h: "いわてけん",
                name_k: "イワテケン",
                area: "東北"
            },
            %Prefecture {
                code: "04",
                name: "宮城県",
                name_e: "miyagi",
                name_h: "みやぎけん",
                name_k: "ミヤギケン",
                area: "東北"
            },
            %Prefecture {
                code: "05",
                name: "秋田県",
                name_e: "akita",
                name_h: "あきたけん",
                name_k: "アキタケン",
                area: "東北"
            },
            %Prefecture {
                code: "06",
                name: "山形県",
                name_e: "yamagata",
                name_h: "やまがたけん",
                name_k: "ヤマガタケン",
                area: "東北"
            },
            %Prefecture {
                code: "07",
                name: "福島県",
                name_e: "fukushima",
                name_h: "ふくしまけん",
                name_k: "フクシマケン",
                area: "東北"
            },
            %Prefecture {
                code: "08",
                name: "茨城県",
                name_e: "ibaraki",
                name_h: "いばらきけん",
                name_k: "イバラキケン",
                area: "関東"
            },
            %Prefecture {
                code: "09",
                name: "栃木県",
                name_e: "tochigi",
                name_h: "とちぎけん",
                name_k: "トチギケン",
                area: "関東"
            },
            %Prefecture {
                code: "10",
                name: "群馬県",
                name_e: "gunma",
                name_h: "ぐんまけん",
                name_k: "グンマケン",
                area: "関東"
            },
            %Prefecture {
                code: "11",
                name: "埼玉県",
                name_e: "saitama",
                name_h: "さいたまけん",
                name_k: "サイタマケン",
                area: "関東"
            },
            %Prefecture {
                code: "12",
                name: "千葉県",
                name_e: "chiba",
                name_h: "ちばけん",
                name_k: "チバケン",
                area: "関東"
            },
            %Prefecture {
                code: "13",
                name: "東京都",
                name_e: "tokyo",
                name_h: "とうきょうと",
                name_k: "トウキョウト",
                area: "関東"
            },
            %Prefecture {
                code: "14",
                name: "神奈川県",
                name_e: "kanagawa",
                name_h: "かながわけん",
                name_k: "カナガワケン",
                area: "関東"
            },
            %Prefecture {
                code: "15",
                name: "新潟県",
                name_e: "niigata",
                name_h: "にいがたけん",
                name_k: "ニイガタケン",
                area: "中部"
            },
            %Prefecture {
                code: "16",
                name: "富山県",
                name_e: "toyama",
                name_h: "とやまけん",
                name_k: "トヤマケン",
                area: "中部"
            },
            %Prefecture {
                code: "17",
                name: "石川県",
                name_e: "ishikawa",
                name_h: "いしかわけん",
                name_k: "イシカワケン",
                area: "中部"
            },
            %Prefecture {
                code: "18",
                name: "福井県",
                name_e: "fukui",
                name_h: "ふくいけん",
                name_k: "フクイケン",
                area: "中部"
            },
            %Prefecture {
                code: "19",
                name: "山梨県",
                name_e: "yamanashi",
                name_h: "やまなしけん",
                name_k: "ヤマナシケン",
                area: "中部"
            },
            %Prefecture {
                code: "20",
                name: "長野県",
                name_e: "nagano",
                name_h: "ながのけん",
                name_k: "ナガノケン",
                area: "中部"
            },
            %Prefecture {
                code: "21",
                name: "岐阜県",
                name_e: "gifu",
                name_h: "ぎふけん",
                name_k: "ギフケン",
                area: "中部"
            },
            %Prefecture {
                code: "22",
                name: "静岡県",
                name_e: "shizuoka",
                name_h: "しずおかけん",
                name_k: "シズオカケン",
                area: "中部"
            },
            %Prefecture {
                code: "23",
                name: "愛知県",
                name_e: "aichi",
                name_h: "あいちけん",
                name_k: "アイチケン",
                area: "中部"
            },
            %Prefecture {
                code: "24",
                name: "三重県",
                name_e: "mie",
                name_h: "みえけん",
                name_k: "ミエケン",
                area: "関西"
            },
            %Prefecture {
                code: "25",
                name: "滋賀県",
                name_e: "shiga",
                name_h: "しがけん",
                name_k: "シガケン",
                area: "関西"
            },
            %Prefecture {
                code: "26",
                name: "京都府",
                name_e: "kyoto",
                name_h: "きょうとふ",
                name_k: "キョウトフ",
                area: "関西"
            },
            %Prefecture {
                code: "27",
                name: "大阪府",
                name_e: "osaka",
                name_h: "おおさかふ",
                name_k: "オオサカフ",
                area: "関西"
            },
            %Prefecture {
                code: "28",
                name: "兵庫県",
                name_e: "hyogo",
                name_h: "ひょうごけん",
                name_k: "ヒョウゴケン",
                area: "関西"
            },
            %Prefecture {
                code: "29",
                name: "奈良県",
                name_e: "nara",
                name_h: "ならけん",
                name_k: "ナラケン",
                area: "関西"
            },
            %Prefecture {
                code: "30",
                name: "和歌山県",
                name_e: "wakayama",
                name_h: "わかやまけん",
                name_k: "ワカヤマケン",
                area: "関西"
            },
            %Prefecture {
                code: "31",
                name: "鳥取県",
                name_e: "tottori",
                name_h: "とっとりけん",
                name_k: "トットリケン",
                area: "中国"
            },
            %Prefecture {
                code: "32",
                name: "島根県",
                name_e: "shimane",
                name_h: "しまねけん",
                name_k: "シマネケン",
                area: "中国"
            },
            %Prefecture {
                code: "33",
                name: "岡山県",
                name_e: "okayama",
                name_h: "おかやまけん",
                name_k: "オカヤマケン",
                area: "中国"
            },
            %Prefecture {
                code: "34",
                name: "広島県",
                name_e: "hiroshima",
                name_h: "ひろしまけん",
                name_k: "ヒロシマケン",
                area: "中国"
            },
            %Prefecture {
                code: "35",
                name: "山口県",
                name_e: "yamaguchi",
                name_h: "やまぐちけん",
                name_k: "ヤマグチケン",
                area: "中国"
            },
            %Prefecture {
                code: "36",
                name: "徳島県",
                name_e: "tokushima",
                name_h: "とくしまけん",
                name_k: "トクシマケン",
                area: "四国"
            },
            %Prefecture {
                code: "37",
                name: "香川県",
                name_e: "kagawa",
                name_h: "かがわけん",
                name_k: "カガワケン",
                area: "四国"
            },
            %Prefecture {
                code: "38",
                name: "愛媛県",
                name_e: "ehime",
                name_h: "えひめけん",
                name_k: "エヒメケン",
                area: "四国"
            },
            %Prefecture {
                code: "39",
                name: "高知県",
                name_e: "kochi",
                name_h: "こうちけん",
                name_k: "コウチケン",
                area: "四国"
            },
            %Prefecture {
                code: "40",
                name: "福岡県",
                name_e: "fukuoka",
                name_h: "ふくおかけん",
                name_k: "フクオカケン",
                area: "九州"
            },
            %Prefecture {
                code: "41",
                name: "佐賀県",
                name_e: "saga",
                name_h: "さがけん",
                name_k: "サガケン",
                area: "九州"
            },
            %Prefecture {
                code: "42",
                name: "長崎県",
                name_e: "nagasaki",
                name_h: "ながさきけん",
                name_k: "ナガサキケン",
                area: "九州"
            },
            %Prefecture {
                code: "43",
                name: "熊本県",
                name_e: "kumamoto",
                name_h: "くまもとけん",
                name_k: "クマモトケン",
                area: "九州"
            },
            %Prefecture {
                code: "44",
                name: "大分県",
                name_e: "oita",
                name_h: "おおいたけん",
                name_k: "オオイタケン",
                area: "九州"
            },
            %Prefecture {
                code: "45",
                name: "宮崎県",
                name_e: "miyazaki",
                name_h: "みやざきけん",
                name_k: "ミヤザキケン",
                area: "九州"
            },
            %Prefecture {
                code: "46",
                name: "鹿児島県",
                name_e: "kagoshima",
                name_h: "かごしまけん",
                name_k: "カゴシマケン",
                area: "九州"
            },
            %Prefecture {
                code: "47",
                name: "沖縄県",
                name_e: "okinawa",
                name_h: "おきなわけん",
                name_k: "オキナワケン",
                area: "九州"
            }
        ]
    end
end