############################################################
# Batak GSUB features for the Medan font.
#
# For full documentation, see
# https://lindenbergsoftware.com/en/notes/constructing-fonts-for-batak/
#
#
# © 2020 Lindenberg Software LLC.
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
############################################################


############################################################
# Language systems.
#
############################################################


languagesystem batk dflt;
languagesystem batk BTX;
languagesystem batk BTM;


############################################################
# Glyph classes.
#
############################################################


@consonant_batak = [
    # Variant glyphs are not needed here.
    a-batak
    aSima-batak
    ha-batak
    haSima-batak
    haMandai-batak
    ba-batak
    baKaro-batak
    pa-batak
    paSima-batak
    na-batak
    naMandai-batak
    wa-batak
    waSima-batak
    waPak-batak
    ga-batak
    gaSima-batak
    ja-batak
    da-batak
    ra-batak
    raSima-batak
    ma-batak
    maSima-batak
    taSouth-batak
    taNorth-batak
    sa-batak
    saSima-batak
    saMandai-batak
    ya-batak
    yaSima-batak
    nga-batak
    la-batak
    laSima-batak
    nya-batak
    ca-batak
    nda-batak
    mba-batak
];

@vowelAbove_batak = [
    eSignPak-batak
    eeSign-batak
    uSignSima-batak
    oSignKaro-batak
];

@vowelBelow_batak = [
    uSign-batak
    uSign-batak.paMandai
    uSign-batak.simple
];

@vowelPost_batak = [
    eSign-batak
    iSign-batak
    iSignKaro-batak
    oSign-batak
];

@vowelSign_batak = [
    @vowelAbove_batak
    @vowelBelow_batak
    @vowelPost_batak
];

@consonantSign_batak = [
    ngSign-batak
    hSign-batak
];

@virama_batak = [
    pangolat-batak
    panongonan-batak
];

@vowelOrConsonantMark = [
    @vowelAbove_batak
    @vowelBelow_batak
    @consonantSign_batak
];

@below_base_batak = [
    @vowelBelow_batak
];

@post_base_batak = [
    @vowelPost_batak
    @virama_batak
];


############################################################
# Validation.
#
# The Universal Shaping Engine does basic validation, but an additional check is necessary
# to enforce the rule that virama signs can’t follow dependent vowels.
############################################################


lookup insert_dotted_circle_batak {
    lookupflag 0;

    sub pangolat-batak by dottedCircle pangolat-batak;
    sub panongonan-batak by dottedCircle panongonan-batak;
} insert_dotted_circle_batak;

feature ccmp {

    lookup validate_batak {
        lookupflag 0;

        sub @vowelSign_batak @virama_batak' lookup insert_dotted_circle_batak;
    } validate_batak;

} ccmp;


############################################################
# Reordering.
#
# If a dependent vowel precedes a sequence of consonant and virama, then the
# dependent vowel has to move to after the consonant.
# Since OpenType doesn’t have a reordering substitution, we do this by copying the
# dependent vowel to before the virama, and deleting it from before the consonant.
# This can’t be done in the USE’s feature application I phase, as it only operates on individual
# clusters, and the USE treats the consonant-virama sequence as a separate cluster.
# It therefore has to be done in the feature application II phase. Of the features applied in
# that phase, rclt seems the least inappropriate.
############################################################


lookup remove_vowel_batak {
    lookupflag 0;

    sub @vowelSign_batak by __.invisible;
} remove_vowel_batak;

lookup insert_eSign_batak {
    lookupflag 0;

    sub pangolat-batak by eSign-batak pangolat-batak;
    sub panongonan-batak by eSign-batak panongonan-batak;
} insert_eSign_batak;

lookup insert_eSignPak_batak {
    lookupflag 0;

    sub pangolat-batak by eSignPak-batak pangolat-batak;
    sub panongonan-batak by eSignPak-batak panongonan-batak;
} insert_eSignPak_batak;

lookup insert_eeSign_batak {
    lookupflag 0;

    sub pangolat-batak by eeSign-batak pangolat-batak;
    sub panongonan-batak by eeSign-batak panongonan-batak;
} insert_eeSign_batak;

lookup insert_iSign_batak {
    lookupflag 0;

    sub pangolat-batak by iSign-batak pangolat-batak;
    sub panongonan-batak by iSign-batak panongonan-batak;
} insert_iSign_batak;

lookup insert_iSignKaro_batak {
    lookupflag 0;

    sub pangolat-batak by iSignKaro-batak pangolat-batak;
    sub panongonan-batak by iSignKaro-batak panongonan-batak;
} insert_iSignKaro_batak;

lookup insert_oSign_batak {
    lookupflag 0;

    sub pangolat-batak by oSign-batak pangolat-batak;
    sub panongonan-batak by oSign-batak panongonan-batak;
} insert_oSign_batak;

lookup insert_oSignKaro_batak {
    lookupflag 0;

    sub pangolat-batak by oSignKaro-batak pangolat-batak;
    sub panongonan-batak by oSignKaro-batak panongonan-batak;
} insert_oSignKaro_batak;

lookup insert_uSign_batak {
    lookupflag 0;

    sub pangolat-batak by uSign-batak pangolat-batak;
    sub panongonan-batak by uSign-batak panongonan-batak;
} insert_uSign_batak;

lookup insert_uSignSima_batak {
    lookupflag 0;

    sub pangolat-batak by uSignSima-batak pangolat-batak;
    sub panongonan-batak by uSignSima-batak panongonan-batak;
} insert_uSignSima_batak;

feature rclt {

    lookup reorder_batak {
        lookupflag UseMarkFilteringSet @vowelOrConsonantMark;

        sub eSign-batak' lookup remove_vowel_batak @consonant_batak' @virama_batak' lookup insert_eSign_batak;
        sub eSignPak-batak' lookup remove_vowel_batak @consonant_batak' @virama_batak' lookup insert_eSignPak_batak;
        sub eeSign-batak' lookup remove_vowel_batak @consonant_batak' @virama_batak' lookup insert_eeSign_batak;
        sub iSign-batak' lookup remove_vowel_batak @consonant_batak' @virama_batak' lookup insert_iSign_batak;
        sub iSignKaro-batak' lookup remove_vowel_batak @consonant_batak' @virama_batak' lookup insert_iSignKaro_batak;
        sub oSign-batak' lookup remove_vowel_batak @consonant_batak' @virama_batak' lookup insert_oSign_batak;
        sub oSignKaro-batak' lookup remove_vowel_batak @consonant_batak' @virama_batak' lookup insert_oSignKaro_batak;
        sub uSign-batak' lookup remove_vowel_batak @consonant_batak' @virama_batak' lookup insert_uSign_batak;
        sub uSignSima-batak' lookup remove_vowel_batak @consonant_batak' @virama_batak' lookup insert_uSignSima_batak;
    } reorder_batak;
} rclt;


############################################################
# Localized forms.
#
# Karo prefers a symmetric form of ja.
# The below-base vowel u below pa is mirrored in Mandailing.
############################################################


feature rclt {

    script batk;

    language BTX;

    lookup karo_ja_batak {
        lookupflag 0;

        sub ja-batak by ja-batak.v1;
    } karo_ja_batak;

    language BTM;

    lookup flip_uSign_batak {
        lookupflag UseMarkFilteringSet @below_base_batak;

        sub pa-batak uSign-batak' by uSign-batak.paMandai;
    } flip_uSign_batak;
} rclt;


############################################################
# Ligatures.
#
# The below-base vowel u forms ligatures with a number of consonants, and uses
# contextual forms with others.
############################################################


feature liga {

    lookup liga_uSign_batak {
        lookupflag UseMarkFilteringSet @below_base_batak;

        sub a-batak uSign-batak by a_uSign-batak;
        sub ha-batak uSign-batak by ha_uSign-batak;
        sub haMandai-batak uSign-batak by haMandai_uSign-batak;
        sub ba-batak uSign-batak by ba_uSign-batak;
        sub na-batak uSign-batak by na_uSign-batak;
        sub naMandai-batak uSign-batak by naMandai_uSign-batak;
        sub wa-batak uSign-batak by wa_uSign-batak;
        sub ga-batak uSign-batak by ga_uSign-batak;
        sub ja-batak uSign-batak by ja_uSign-batak;
        sub ja-batak.v1 uSign-batak by ja_uSign-batak.v1;
        sub da-batak uSign-batak by da_uSign-batak;
        sub ra-batak uSign-batak by ra_uSign-batak;
        sub ma-batak uSign-batak by ma_uSign-batak;
        sub maSima-batak uSign-batak by maSima_uSign-batak;
        sub taSouth-batak uSign-batak by taSouth_uSign-batak;
        sub taNorth-batak uSign-batak by taNorth_uSign-batak;
        sub saMandai-batak uSign-batak by saMandai_uSign-batak;
        sub nga-batak uSign-batak by nga_uSign-batak;
        sub la-batak uSign-batak by la_uSign-batak;
        sub nya-batak uSign-batak by nya_uSign-batak;
    } liga_uSign_batak;

    lookup simple_uSign_batak {
        lookupflag UseMarkFilteringSet @below_base_batak;

        sub [aSima-batak haSima-batak waSima-batak gaSima-batak raSima-batak maSima-batak] uSign-batak' by uSign-batak.simple;
    } simple_uSign_batak;
} liga;


############################################################
# Character variants.
#
# Several characters have variant glyphs. We enable them separately per character.
############################################################


feature cv01 {

    sub a-batak from [a-batak.v1];
} cv01;

feature cv02 {

    sub ha-batak from [ha-batak.v1];
} cv02;

feature cv03 {

    lookup flip_uSign_batak;
} cv03;

feature cv04 {

    sub na-batak from [na-batak.v1];
    sub na_uSign-batak from [na_uSign-batak.v1];
} cv04;

feature cv05 {

    lookup waSima_variant_batak {
        lookupflag UseMarkFilteringSet @below_base_batak;

        sub waSima-batak uSign-batak.simple by waSima_uSign-batak.v1;
    } waSima_variant_batak;
} cv05;

feature cv06 {

    sub ja-batak from [ja-batak.v1];
    sub ja_uSign-batak from [ja_uSign-batak.v1];
} cv06;

feature cv07 {

    sub ra-batak from [ra-batak.v1];
} cv07;

feature cv08 {

    sub ma-batak from [ma-batak.v1 ma-batak.v2];
    sub ma_uSign-batak from [ma_uSign-batak.v1 ma_uSign-batak.v2];
} cv08;

feature cv09 {

    sub sa-batak from [sa-batak.v1 sa-batak.v2 sa-batak.v3 sa-batak.v4];
} cv09;

feature cv10 {

    sub la_uSign-batak by la-batak uSign-batak;
} cv10;

feature cv11 {

    sub ca-batak from [ca-batak.v1];
} cv11;

feature cv12 {

    sub nda-batak from [nda-batak.v1 nda-batak.v2 nda-batak.v3];
} cv12;

feature cv13 {

    sub mba-batak from [mba-batak.v1];
} cv13;