// SPDX-License-Identifier: AGPL-3.0-only

use renderer::mesh::Vertex;
use shared::world::{BlockId, CHUNK_SIZE, Chunk};

#[expect(
    clippy::cast_precision_loss,
    clippy::cast_possible_truncation,
    clippy::too_many_lines
)]
pub fn generate_mesh(chunk: &Chunk) -> (Vec<Vertex>, Vec<u32>) {
    let mut vertices = Vec::new();
    let mut indices = Vec::new();

    for x in 0..CHUNK_SIZE {
        for y in 0..CHUNK_SIZE {
            for z in 0..CHUNK_SIZE {
                let block = chunk.get(x, y, z);

                if block == BlockId::AIR {
                    continue;
                }

                let fx = x as f32;
                let fy = y as f32;
                let fz = z as f32;

                if y == CHUNK_SIZE - 1 || chunk.get(x, y + 1, z) == BlockId::AIR {
                    let base_idx = vertices.len() as u32;

                    vertices.push(Vertex {
                        position: [fx - 0.5, fy + 0.5, fz + 0.5],
                        color: [0.2, 0.8, 0.2],
                    });
                    vertices.push(Vertex {
                        position: [fx + 0.5, fy + 0.5, fz + 0.5],
                        color: [0.2, 0.8, 0.2],
                    });
                    vertices.push(Vertex {
                        position: [fx + 0.5, fy + 0.5, fz - 0.5],
                        color: [0.2, 0.8, 0.2],
                    });
                    vertices.push(Vertex {
                        position: [fx - 0.5, fy + 0.5, fz - 0.5],
                        color: [0.2, 0.8, 0.2],
                    });

                    indices.extend_from_slice(&[
                        base_idx,
                        base_idx + 1,
                        base_idx + 2,
                        base_idx + 2,
                        base_idx + 3,
                        base_idx,
                    ]);
                }

                if y == 0 || chunk.get(x, y - 1, z) == BlockId::AIR {
                    let base_idx = vertices.len() as u32;

                    vertices.push(Vertex {
                        position: [fx - 0.5, fy - 0.5, fz - 0.5],
                        color: [0.1, 0.4, 0.1],
                    });
                    vertices.push(Vertex {
                        position: [fx + 0.5, fy - 0.5, fz - 0.5],
                        color: [0.1, 0.4, 0.1],
                    });
                    vertices.push(Vertex {
                        position: [fx + 0.5, fy - 0.5, fz + 0.5],
                        color: [0.1, 0.4, 0.1],
                    });
                    vertices.push(Vertex {
                        position: [fx - 0.5, fy - 0.5, fz + 0.5],
                        color: [0.1, 0.4, 0.1],
                    });
                    indices.extend_from_slice(&[
                        base_idx,
                        base_idx + 1,
                        base_idx + 2,
                        base_idx + 2,
                        base_idx + 3,
                        base_idx,
                    ]);
                }

                if x == CHUNK_SIZE - 1 || chunk.get(x + 1, y, z) == BlockId::AIR {
                    let base_idx = vertices.len() as u32;

                    vertices.push(Vertex {
                        position: [fx + 0.5, fy - 0.5, fz + 0.5],
                        color: [0.15, 0.6, 0.15],
                    });
                    vertices.push(Vertex {
                        position: [fx + 0.5, fy - 0.5, fz - 0.5],
                        color: [0.15, 0.6, 0.15],
                    });
                    vertices.push(Vertex {
                        position: [fx + 0.5, fy + 0.5, fz - 0.5],
                        color: [0.15, 0.6, 0.15],
                    });
                    vertices.push(Vertex {
                        position: [fx + 0.5, fy + 0.5, fz + 0.5],
                        color: [0.15, 0.6, 0.15],
                    });
                    indices.extend_from_slice(&[
                        base_idx,
                        base_idx + 1,
                        base_idx + 2,
                        base_idx + 2,
                        base_idx + 3,
                        base_idx,
                    ]);
                }

                if x == 0 || chunk.get(x - 1, y, z) == BlockId::AIR {
                    let base_idx = vertices.len() as u32;

                    vertices.push(Vertex {
                        position: [fx - 0.5, fy - 0.5, fz - 0.5],
                        color: [0.15, 0.6, 0.15],
                    });
                    vertices.push(Vertex {
                        position: [fx - 0.5, fy - 0.5, fz + 0.5],
                        color: [0.15, 0.6, 0.15],
                    });
                    vertices.push(Vertex {
                        position: [fx - 0.5, fy + 0.5, fz + 0.5],
                        color: [0.15, 0.6, 0.15],
                    });
                    vertices.push(Vertex {
                        position: [fx - 0.5, fy + 0.5, fz - 0.5],
                        color: [0.15, 0.6, 0.15],
                    });
                    indices.extend_from_slice(&[
                        base_idx,
                        base_idx + 1,
                        base_idx + 2,
                        base_idx + 2,
                        base_idx + 3,
                        base_idx,
                    ]);
                }

                if z == CHUNK_SIZE - 1 || chunk.get(x, y, z + 1) == BlockId::AIR {
                    let base_idx = vertices.len() as u32;

                    vertices.push(Vertex {
                        position: [fx - 0.5, fy - 0.5, fz + 0.5],
                        color: [0.18, 0.7, 0.18],
                    });
                    vertices.push(Vertex {
                        position: [fx + 0.5, fy - 0.5, fz + 0.5],
                        color: [0.18, 0.7, 0.18],
                    });
                    vertices.push(Vertex {
                        position: [fx + 0.5, fy + 0.5, fz + 0.5],
                        color: [0.18, 0.7, 0.18],
                    });
                    vertices.push(Vertex {
                        position: [fx - 0.5, fy + 0.5, fz + 0.5],
                        color: [0.18, 0.7, 0.18],
                    });
                    indices.extend_from_slice(&[
                        base_idx,
                        base_idx + 1,
                        base_idx + 2,
                        base_idx + 2,
                        base_idx + 3,
                        base_idx,
                    ]);
                }

                if z == 0 || chunk.get(x, y, z - 1) == BlockId::AIR {
                    let base_idx = vertices.len() as u32;

                    vertices.push(Vertex {
                        position: [fx + 0.5, fy - 0.5, fz - 0.5],
                        color: [0.18, 0.7, 0.18],
                    });
                    vertices.push(Vertex {
                        position: [fx - 0.5, fy - 0.5, fz - 0.5],
                        color: [0.18, 0.7, 0.18],
                    });
                    vertices.push(Vertex {
                        position: [fx - 0.5, fy + 0.5, fz - 0.5],
                        color: [0.18, 0.7, 0.18],
                    });
                    vertices.push(Vertex {
                        position: [fx + 0.5, fy + 0.5, fz - 0.5],
                        color: [0.18, 0.7, 0.18],
                    });
                    indices.extend_from_slice(&[
                        base_idx,
                        base_idx + 1,
                        base_idx + 2,
                        base_idx + 2,
                        base_idx + 3,
                        base_idx,
                    ]);
                }
            }
        }
    }

    (vertices, indices)
}