# 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 create_shader, resolve_input, select_shader, unselect_shader, destroy_shader

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 _parse(shader, vert_lines, frag_lines):
    uniforms = []
    for line in vert_lines:
        if line.startswith('uniform '):
            uniforms.append(line.split()[-1].strip(';'))
    for line in frag_lines:
        if line.startswith('uniform '):
            name = line.split()[-1].strip(';')
            if name not in uniforms:
                uniforms.append(name)
    for name in uniforms:
        setattr(shader, name, resolve_input(shader._shader, bytes(name, 'utf-8')))

class Shader:
    __slots__ = '_shader', '__dict__'

    def __init__(self, vert_name, frag_name = ''):
        path = Path('.') / 'game' / 'shaders'
        assert path.exists()
        if not frag_name:
            frag_name = vert_name
        print("Loading vertex shader", vert_name)
        vert_lines = _load_source(path / (vert_name + '_opengles.vert'))
        assert vert_lines
        print("Loading fragment shader", frag_name)
        frag_lines = _load_source(path / (frag_name + '_opengles.frag'))
        assert frag_lines
        self._shader = create_shader(list(map(_convert, vert_lines)), list(map(_convert, frag_lines)))
        _parse(self, vert_lines, frag_lines)

    def __del__(self):
        destroy_shader(self._shader)

    def select(self):
        select_shader(self._shader)

    def unselect(self):
        unselect_shader(self._shader)