#import bevy_pbr::prepass_bindings
#import bevy_pbr::mesh_functions
#import bevy_pbr::skinning
#import bevy_pbr::morph
#import bevy_pbr::mesh_bindings mesh

// Most of these attributes are not used in the default prepass fragment shader, but they are still needed so we can
// pass them to custom prepass shaders like pbr_prepass.wgsl.
struct Vertex {
    @location(0) position: vec3<f32>,

#ifdef VERTEX_UVS
    @location(1) uv: vec2<f32>,
#endif // VERTEX_UVS

#ifdef NORMAL_PREPASS
    @location(2) normal: vec3<f32>,
#ifdef VERTEX_TANGENTS
    @location(3) tangent: vec4<f32>,
#endif // VERTEX_TANGENTS
#endif // NORMAL_PREPASS

#ifdef SKINNED
    @location(4) joint_indices: vec4<u32>,
    @location(5) joint_weights: vec4<f32>,
#endif // SKINNED

#ifdef MORPH_TARGETS
    @builtin(vertex_index) index: u32,
#endif // MORPH_TARGETS
}

struct VertexOutput {
    @builtin(position) clip_position: vec4<f32>,

#ifdef VERTEX_UVS
    @location(0) uv: vec2<f32>,
#endif // VERTEX_UVS

#ifdef NORMAL_PREPASS
    @location(1) world_normal: vec3<f32>,
#ifdef VERTEX_TANGENTS
    @location(2) world_tangent: vec4<f32>,
#endif // VERTEX_TANGENTS
#endif // NORMAL_PREPASS

#ifdef MOTION_VECTOR_PREPASS
    @location(3) world_position: vec4<f32>,
    @location(4) previous_world_position: vec4<f32>,
#endif // MOTION_VECTOR_PREPASS

#ifdef DEPTH_CLAMP_ORTHO
    @location(5) clip_position_unclamped: vec4<f32>,
#endif // DEPTH_CLAMP_ORTHO
}

#ifdef MORPH_TARGETS
fn morph_vertex(vertex_in: Vertex) -> Vertex {
    var vertex = vertex_in;
    let weight_count = layer_count();
    for (var i: u32 = 0u; i < weight_count; i ++) {
        let weight = weight_at(i);
        if weight == 0.0 {
            continue;
        }
        vertex.position += weight * morph(vertex.index, position_offset, i);
#ifdef VERTEX_NORMALS
        vertex.normal += weight * morph(vertex.index, normal_offset, i);
#endif
#ifdef VERTEX_TANGENTS
        vertex.tangent += vec4(weight * morph(vertex.index, tangent_offset, i), 0.0);
#endif
    }
    return vertex;
}
#endif

@vertex
fn vertex(vertex_no_morph: Vertex) -> VertexOutput {
    var out: VertexOutput;

#ifdef MORPH_TARGETS
    var vertex = morph_vertex(vertex_no_morph);
#else
    var vertex = vertex_no_morph;
#endif

#ifdef SKINNED
    var model = bevy_pbr::skinning::skin_model(vertex.joint_indices, vertex.joint_weights);
#else // SKINNED
    var model = mesh.model;
#endif // SKINNED

    out.clip_position = bevy_pbr::mesh_functions::mesh_position_local_to_clip(model, vec4(vertex.position, 1.0));
#ifdef DEPTH_CLAMP_ORTHO
    out.clip_position_unclamped = out.clip_position;
    out.clip_position.z = min(out.clip_position.z, 1.0);
#endif // DEPTH_CLAMP_ORTHO

#ifdef VERTEX_UVS
    out.uv = vertex.uv;
#endif // VERTEX_UVS

#ifdef NORMAL_PREPASS
#ifdef SKINNED
    out.world_normal = bevy_pbr::skinning::skin_normals(model, vertex.normal);
#else // SKINNED
    out.world_normal = bevy_pbr::mesh_functions::mesh_normal_local_to_world(vertex.normal);
#endif // SKINNED

#ifdef VERTEX_TANGENTS
    out.world_tangent = bevy_pbr::mesh_functions::mesh_tangent_local_to_world(model, vertex.tangent);
#endif // VERTEX_TANGENTS
#endif // NORMAL_PREPASS

#ifdef MOTION_VECTOR_PREPASS
    out.world_position = bevy_pbr::mesh_functions::mesh_position_local_to_world(model, vec4<f32>(vertex.position, 1.0));
    out.previous_world_position = bevy_pbr::mesh_functions::mesh_position_local_to_world(mesh.previous_model, vec4<f32>(vertex.position, 1.0));
#endif // MOTION_VECTOR_PREPASS

    return out;
}

#ifdef PREPASS_FRAGMENT
struct FragmentInput {
#ifdef VERTEX_UVS
    @location(0) uv: vec2<f32>,
#endif // VERTEX_UVS

#ifdef NORMAL_PREPASS
    @location(1) world_normal: vec3<f32>,
#endif // NORMAL_PREPASS

#ifdef MOTION_VECTOR_PREPASS
    @location(3) world_position: vec4<f32>,
    @location(4) previous_world_position: vec4<f32>,
#endif // MOTION_VECTOR_PREPASS

#ifdef DEPTH_CLAMP_ORTHO
    @location(5) clip_position_unclamped: vec4<f32>,
#endif // DEPTH_CLAMP_ORTHO
}

struct FragmentOutput {
#ifdef NORMAL_PREPASS
    @location(0) normal: vec4<f32>,
#endif // NORMAL_PREPASS

#ifdef MOTION_VECTOR_PREPASS
    @location(1) motion_vector: vec2<f32>,
#endif // MOTION_VECTOR_PREPASS

#ifdef DEPTH_CLAMP_ORTHO
    @builtin(frag_depth) frag_depth: f32,
#endif // DEPTH_CLAMP_ORTHO
}

@fragment
fn fragment(in: FragmentInput) -> FragmentOutput {
    var out: FragmentOutput;

#ifdef NORMAL_PREPASS
    out.normal = vec4(in.world_normal * 0.5 + vec3(0.5), 1.0);
#endif

#ifdef DEPTH_CLAMP_ORTHO
    out.frag_depth = in.clip_position_unclamped.z;
#endif // DEPTH_CLAMP_ORTHO

#ifdef MOTION_VECTOR_PREPASS
    let clip_position_t = bevy_pbr::prepass_bindings::view.unjittered_view_proj * in.world_position;
    let clip_position = clip_position_t.xy / clip_position_t.w;
    let previous_clip_position_t = bevy_pbr::prepass_bindings::previous_view_proj * in.previous_world_position;
    let previous_clip_position = previous_clip_position_t.xy / previous_clip_position_t.w;
    // These motion vectors are used as offsets to UV positions and are stored
    // in the range -1,1 to allow offsetting from the one corner to the
    // diagonally-opposite corner in UV coordinates, in either direction.
    // A difference between diagonally-opposite corners of clip space is in the
    // range -2,2, so this needs to be scaled by 0.5. And the V direction goes
    // down where clip space y goes up, so y needs to be flipped.
    out.motion_vector = (clip_position - previous_clip_position) * vec2(0.5, -0.5);
#endif // MOTION_VECTOR_PREPASS

    return out;
}
#endif // PREPASS_FRAGMENT