/*
    wearechat - generic multiplayer game with voip
    Copyright (C) 2025 metamuffin

    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, version 3 of the License only.

    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 <https://www.gnu.org/licenses/>.
*/
use super::{
    ScenePreparer,
    meshops::{generate_normals, generate_tangents, generate_texcoords},
};
use anyhow::Result;
use log::debug;
use std::{sync::Arc, time::Instant};
use wgpu::{
    BufferUsages,
    util::{BufferInitDescriptor, DeviceExt},
};

impl ScenePreparer {
    pub fn update_vertex_buffers(&self, num_done: &mut usize) -> Result<()> {
        for pres in self.index_buffers.needed() {
            let start = Instant::now();
            if let Some(buf) = self.downloader.try_get(pres.clone())? {
                let buffer = self.device.create_buffer_init(&BufferInitDescriptor {
                    label: Some("index"),
                    contents: bytemuck::cast_slice(buf.as_slice()),
                    usage: BufferUsages::INDEX | BufferUsages::COPY_DST,
                });
                self.index_buffers.insert(
                    pres.clone(),
                    (Arc::new(buffer), (buf.len() * 3) as u32),
                    buf.len() * size_of::<u32>() * 3,
                );
                debug!(
                    "index buffer created (len={}, took {:?}) {pres}",
                    buf.len() / size_of::<u32>(),
                    start.elapsed(),
                );
                *num_done += 1;
            }
        }
        for pres in self.vertex_buffers.needed() {
            let start = Instant::now();
            if let Some(buf) = self.downloader.try_get(pres.clone())? {
                let buffer = self.device.create_buffer_init(&BufferInitDescriptor {
                    contents: bytemuck::cast_slice(buf.as_slice()),
                    label: Some("vertex attribute"),
                    usage: BufferUsages::VERTEX | BufferUsages::COPY_DST,
                });
                self.vertex_buffers.insert(
                    pres.clone(),
                    Arc::new(buffer),
                    buf.len() * size_of::<f32>(),
                );
                debug!(
                    "vertex attribute buffer created (len={}, took {:?}) {pres}",
                    buf.len() / size_of::<f32>(),
                    start.elapsed()
                );
                *num_done += 1;
            }
        }

        for spec in self.generated_tangent_buffers.needed() {
            if let (Some(index), Some(position), texcoord) = (
                self.downloader.try_get(spec.index.clone())?,
                self.downloader.try_get(spec.position.clone())?,
                spec.texcoord
                    .clone()
                    .map(|r| self.downloader.try_get(r))
                    .transpose()?,
            ) {
                let texcoord = match texcoord {
                    Some(Some(x)) => Some(x),
                    Some(None) => continue, // tangents provided but still loading
                    None => None,
                };
                let texcoord = texcoord.unwrap_or_else(|| generate_texcoords(&index, &position));
                let tangents = generate_tangents(&index, &position, &texcoord);
                let buffer = self.device.create_buffer_init(&BufferInitDescriptor {
                    label: Some("generated tangent"),
                    usage: BufferUsages::COPY_DST | BufferUsages::VERTEX,
                    contents: bytemuck::cast_slice(tangents.as_slice()),
                });
                self.generated_tangent_buffers.insert(
                    spec,
                    Arc::new(buffer),
                    size_of::<f32>() * tangents.len() * 3,
                );
            }
        }
        for spec in self.generated_normal_buffers.needed() {
            if let (Some(index), Some(position)) = (
                self.downloader.try_get(spec.index.clone())?,
                self.downloader.try_get(spec.position.clone())?,
            ) {
                let normals = generate_normals(&index, &position);
                let buffer = self.device.create_buffer_init(&BufferInitDescriptor {
                    label: Some("generated normal"),
                    usage: BufferUsages::COPY_DST | BufferUsages::VERTEX,
                    contents: bytemuck::cast_slice(normals.as_slice()),
                });
                self.generated_normal_buffers.insert(
                    spec,
                    Arc::new(buffer),
                    size_of::<f32>() * normals.len() * 3,
                );
            }
        }
        for spec in self.generated_texcoord_buffers.needed() {
            if let (Some(index), Some(position)) = (
                self.downloader.try_get(spec.index.clone())?,
                self.downloader.try_get(spec.position.clone())?,
            ) {
                let texcoords = generate_texcoords(&index, &position);
                let buffer = self.device.create_buffer_init(&BufferInitDescriptor {
                    label: Some("generated texcoord"),
                    usage: BufferUsages::COPY_DST | BufferUsages::VERTEX,
                    contents: bytemuck::cast_slice(texcoords.as_slice()),
                });
                self.generated_texcoord_buffers.insert(
                    spec,
                    Arc::new(buffer),
                    size_of::<f32>() * texcoords.len() * 3,
                );
            }
        }

        Ok(())
    }
}