# Copyright (C) 2022 RozK
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from pathlib import Path

from engine import load_shader

#TODO: preprocessing (at least includes)

def _cleanup(line):
    return line.partition('//')[0].strip()

def _filter(line):
    return line

def _subst(line):
    if line.startswith('#include '):
        path = Path('.') / 'game' / 'shaders'
        lines = []
        for name in line.split()[1:]:
            lines.extend(_load_source(path / name.strip('"')))
        return lines
    return [line]

def _load_source(_path):
    assert _path.exists()
    lines = filter(_filter, map(_cleanup, open(_path, 'rt')))
    source = []
    for line in lines:
        source.extend(_subst(line))
    return source

def _convert(line):
    return bytes(line, 'utf-8') + b'\n'

def load(vert_name, frag_name = ''):
    path = Path('.') / 'game' / 'shaders'
    if not frag_name:
        frag_name = vert_name
    print("Loading vertex shader", vert_name)
    vert_lines = list(map(_convert, _load_source(path / (vert_name + '_opengles.vert'))))
    assert vert_lines
    print("Loading fragment shader", frag_name)
    frag_lines = list(map(_convert, _load_source(path / (frag_name + '_opengles.frag'))))
    assert frag_lines
    return load_shader(vert_lines, frag_lines)