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// Copyright (C) 2019 Oscar Shrimpton
//
// This file is part of stockton-bsp.
//
// stockton-bsp is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// stockton-bsp 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with stockton-bsp.  If not, see <http://www.gnu.org/licenses/>.

//! Parses the brushes & brushsides lumps from a bsp file

/// The size of one brush record.
const BRUSH_SIZE: usize = (4 * 3);

/// The size of one brushsize record
const SIDE_SIZE: usize = (4 * 2);

use crate::lumps::helpers::slice_to_i32;
use crate::lumps::planes::PlanesLump;
use crate::lumps::textures::TexturesLump;
use crate::types::Result;

/// A brushes lump from a bsp file.
/// BrushSides are also stored inside here.
#[derive(Debug, Clone)]
pub struct BrushesLump {
    pub brushes: Box<[Brush]>,
}

/// One brush record. Used for collision detection.
/// "Each brush describes a convex volume as defined by its surrounding surfaces."
#[derive(Debug, Clone, PartialEq)]
pub struct Brush {
    pub sides: Box<[BrushSide]>,
    pub texture_idx: usize,
}

/// Bounding surface for brush.
#[derive(Debug, Clone, PartialEq)]
pub struct BrushSide {
    pub plane_idx: usize,
    pub texture_idx: usize,
    pub is_opposing: bool,
}

impl BrushesLump {
    /// Parse the brushes & brushsides lump from a bsp file.
    pub fn from_lump(
        brushes_lump: &[u8],
        brush_sides_lump: &[u8],
        textures_lump: &TexturesLump,
        planes_lump: &PlanesLump
    ) -> Result<BrushesLump> {
        if brushes_lump.len() % BRUSH_SIZE != 0 || brush_sides_lump.len() % SIDE_SIZE != 0 {
            return Err(invalid_error!("BrushesLump is incorrectly sized"));
        }
        let length = brushes_lump.len() / BRUSH_SIZE;

        let mut brushes = Vec::with_capacity(length as usize);
        for n in 0..length {
            let offset = n * BRUSH_SIZE;
            let brush = &brushes_lump[offset..offset + BRUSH_SIZE];

            let texture_idx = slice_to_i32(&brush[8..12]) as usize;
            if texture_idx >= textures_lump.textures.len() {
                return Err(invalid_error!("Brushes references a texture that doesn't exist"));
            }

            brushes.push(Brush {
                sides: BrushesLump::get_sides(
                    brush_sides_lump,
                    slice_to_i32(&brush[0..4]),
                    slice_to_i32(&brush[4..8]),
                    textures_lump,
                    planes_lump,
                )?,
                texture_idx
            });
        }

        Ok(BrushesLump {
            brushes: brushes.into_boxed_slice(),
        })
    }

    /// Internal function to get the relevant brushsides for a brush from the data in the brush lump.
    fn get_sides(
        brush_sides_lump: &[u8],
        start: i32,
        length: i32,
        textures_lump: &TexturesLump,
        planes_lump: &PlanesLump,
    ) -> Result<Box<[BrushSide]>> {
        let mut sides = Vec::with_capacity(length as usize);

        if length > 0 {
            for n in start..start + length {
                let offset = n as usize * SIDE_SIZE;
                let brush = &brush_sides_lump[offset..offset + SIDE_SIZE];

                let plane_idx = slice_to_i32(&brush[0..4]) as usize;
                if plane_idx / 2 >= planes_lump.planes.len() {
                    return Err(invalid_error!("BrushSide references a plane that doesn't exist"));
                }

                let is_opposing = plane_idx % 2 != 0;

                let texture_idx = slice_to_i32(&brush[4..8]) as usize;
                if texture_idx >= textures_lump.textures.len() {
                    return Err(invalid_error!("BrushSide references a texture that doesn't exist"));
                }

                sides.push(BrushSide {
                    plane_idx,
                    texture_idx,
                    is_opposing
                });
            }
        }

        Ok(sides.into_boxed_slice())
    }
}