use std::any::type_name;
use std::borrow::Cow;
use std::collections::HashMap;
use std::fmt::Debug;
use std::path::Path;
use std::str::Utf8Error;

use bitflags::bitflags;
use ecs::pair::{ChildOf, Pair};
use ecs::phase::{Phase, START as START_PHASE};
use ecs::sole::Single;
use ecs::{Component, Sole, declare_entity};
use shader_slang::{
    Blob as SlangBlob,
    ComponentType as SlangComponentType,
    DebugInfoLevel as SlangDebugInfoLevel,
    EntryPoint as SlangEntryPoint,
    GlobalSession as SlangGlobalSession,
    Module as SlangModule,
    ParameterCategory as SlangParameterCategory,
    Session as SlangSession,
    TypeKind as SlangTypeKind,
};

use crate::asset::{
    Assets,
    Event as AssetEvent,
    HANDLE_ASSETS_PHASE,
    Handle as AssetHandle,
    Id as AssetId,
    Submitter as AssetSubmitter,
};
use crate::builder;
use crate::renderer::PRE_RENDER_PHASE;
use crate::shader::default::{
    ASSET_LABEL,
    enqueue_set_shader_bindings as default_shader_enqueue_set_shader_bindings,
};

pub mod cursor;
pub mod default;

#[derive(Debug, Clone, Component)]
pub struct Shader
{
    pub asset_handle: AssetHandle<ModuleSource>,
}

/// Shader module.
#[derive(Debug)]
pub struct ModuleSource
{
    pub name: Cow<'static, str>,
    pub file_path: Cow<'static, Path>,
    pub source: Cow<'static, str>,
    pub link_entrypoints: EntrypointFlags,
}

bitflags! {
    #[derive(Debug, Clone, Copy, Default)]
    pub struct EntrypointFlags: usize
    {
        const FRAGMENT = 1 << 0;
        const VERTEX = 1 << 1;
    }
}

pub struct Module
{
    inner: SlangModule,
}

impl Module
{
    pub fn entry_points(&self) -> impl ExactSizeIterator<Item = EntryPoint>
    {
        self.inner
            .entry_points()
            .map(|entry_point| EntryPoint { inner: entry_point })
    }

    pub fn get_entry_point(&self, entry_point: &str) -> Option<EntryPoint>
    {
        let entry_point = self.inner.find_entry_point_by_name(entry_point)?;

        Some(EntryPoint { inner: entry_point })
    }
}

pub struct EntryPoint
{
    inner: SlangEntryPoint,
}

impl EntryPoint
{
    pub fn function_name(&self) -> Option<&str>
    {
        self.inner.function_reflection().name()
    }
}

pub struct EntryPointReflection<'a>
{
    inner: &'a shader_slang::reflection::EntryPoint,
}

impl<'a> EntryPointReflection<'a>
{
    pub fn name(&self) -> Option<&str>
    {
        self.inner.name()
    }

    pub fn name_override(&self) -> Option<&str>
    {
        self.inner.name_override()
    }

    pub fn stage(&self) -> Stage
    {
        Stage::from_slang_stage(self.inner.stage())
    }

    pub fn parameters(&self) -> impl ExactSizeIterator<Item = VariableLayout<'a>>
    {
        self.inner
            .parameters()
            .map(|param| VariableLayout { inner: param })
    }

    pub fn var_layout(&self) -> Option<VariableLayout<'a>>
    {
        Some(VariableLayout { inner: self.inner.var_layout()? })
    }
}

#[derive(Clone)]
pub struct Program
{
    inner: SlangComponentType,
}

impl Program
{
    pub fn link(&self) -> Result<Program, Error>
    {
        let linked_program = self.inner.link()?;

        Ok(Program { inner: linked_program })
    }

    pub fn get_entry_point_code(&self, entry_point_index: u32) -> Result<Blob, Error>
    {
        let blob = self.inner.entry_point_code(entry_point_index.into(), 0)?;

        Ok(Blob { inner: blob })
    }

    pub fn reflection(&self, target: u32) -> Result<ProgramReflection<'_>, Error>
    {
        let reflection = self.inner.layout(target as i64)?;

        Ok(ProgramReflection { inner: reflection })
    }
}

impl Debug for Program
{
    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
    {
        formatter
            .debug_struct(type_name::<Self>())
            .finish_non_exhaustive()
    }
}

pub struct ProgramReflection<'a>
{
    inner: &'a shader_slang::reflection::Shader,
}

impl<'a> ProgramReflection<'a>
{
    pub fn get_entry_point_by_index(&self, index: u32)
    -> Option<EntryPointReflection<'a>>
    {
        Some(EntryPointReflection {
            inner: self.inner.entry_point_by_index(index)?,
        })
    }

    pub fn get_entry_point_by_name(&self, name: &str)
    -> Option<EntryPointReflection<'a>>
    {
        Some(EntryPointReflection {
            inner: self.inner.find_entry_point_by_name(name)?,
        })
    }

    pub fn entry_points(&self)
    -> impl ExactSizeIterator<Item = EntryPointReflection<'a>>
    {
        self.inner
            .entry_points()
            .map(|entry_point| EntryPointReflection { inner: entry_point })
    }

    pub fn global_params_type_layout(&self) -> Option<TypeLayout<'a>>
    {
        Some(TypeLayout {
            inner: self.inner.global_params_type_layout()?,
        })
    }

    pub fn global_params_var_layout(&self) -> Option<VariableLayout<'a>>
    {
        Some(VariableLayout {
            inner: self.inner.global_params_var_layout()?,
        })
    }

    pub fn get_type(&self, name: &str) -> Option<TypeReflection<'a>>
    {
        Some(TypeReflection {
            inner: self.inner.find_type_by_name(name)?,
        })
    }

    pub fn get_type_layout(&self, ty: &TypeReflection<'a>) -> Option<TypeLayout<'a>>
    {
        Some(TypeLayout {
            inner: self
                .inner
                .type_layout(&ty.inner, shader_slang::LayoutRules::Default)?,
        })
    }
}

#[derive(Clone, Copy)]
pub struct VariableLayout<'a>
{
    inner: &'a shader_slang::reflection::VariableLayout,
}

impl<'a> VariableLayout<'a>
{
    pub fn name(&self) -> Option<&str>
    {
        self.inner.name()
    }

    pub fn semantic_name(&self) -> Option<&str>
    {
        self.inner.semantic_name()
    }

    pub fn binding_index(&self) -> u32
    {
        self.inner
            .offset(shader_slang::ParameterCategory::DescriptorTableSlot) as u32

        // self.inner.binding_index()
    }

    pub fn binding_space(&self) -> u32
    {
        self.inner.binding_space()
    }

    pub fn semantic_index(&self) -> usize
    {
        self.inner.semantic_index()
    }

    pub fn offset(&self) -> usize
    {
        self.inner.offset(shader_slang::ParameterCategory::Uniform)
    }

    pub fn ty(&self) -> Option<TypeReflection<'a>>
    {
        self.inner.ty().map(|ty| TypeReflection { inner: ty })
    }

    pub fn type_layout(&self) -> Option<TypeLayout<'a>>
    {
        Some(TypeLayout { inner: self.inner.type_layout()? })
    }
}

#[derive(Clone, Copy)]
pub struct TypeLayout<'a>
{
    inner: &'a shader_slang::reflection::TypeLayout,
}

impl<'a> TypeLayout<'a>
{
    pub fn get_field_by_name(&self, name: &str) -> Option<VariableLayout<'a>>
    {
        let index = self.inner.find_field_index_by_name(name);

        if index < 0 {
            return None;
        }

        let index = u32::try_from(index.cast_unsigned()).expect("Should not happend");

        let field = self.inner.field_by_index(index)?;

        Some(VariableLayout { inner: field })
    }

    pub fn binding_range_descriptor_set_index(&self, index: i64) -> i64
    {
        self.inner.binding_range_descriptor_set_index(index)
    }

    pub fn get_field_binding_range_offset_by_name(&self, name: &str) -> Option<u64>
    {
        let field_index = self.inner.find_field_index_by_name(name);

        if field_index < 0 {
            return None;
        }

        let field_binding_range_offset =
            self.inner.field_binding_range_offset(field_index);

        if field_binding_range_offset < 0 {
            return None;
        }

        Some(field_binding_range_offset.cast_unsigned())
    }

    pub fn ty(&self) -> Option<TypeReflection<'a>>
    {
        self.inner.ty().map(|ty| TypeReflection { inner: ty })
    }

    pub fn fields(&self) -> impl ExactSizeIterator<Item = VariableLayout<'a>>
    {
        self.inner
            .fields()
            .map(|field| VariableLayout { inner: field })
    }

    pub fn field_cnt(&self) -> u32
    {
        self.inner.field_count()
    }

    pub fn element_type_layout(&self) -> Option<TypeLayout<'a>>
    {
        self.inner
            .element_type_layout()
            .map(|type_layout| TypeLayout { inner: type_layout })
    }

    pub fn element_var_layout(&self) -> Option<VariableLayout<'a>>
    {
        self.inner
            .element_var_layout()
            .map(|var_layout| VariableLayout { inner: var_layout })
    }

    pub fn container_var_layout(&self) -> Option<VariableLayout<'a>>
    {
        self.inner
            .container_var_layout()
            .map(|var_layout| VariableLayout { inner: var_layout })
    }

    pub fn uniform_size(&self) -> Option<usize>
    {
        // tracing::debug!(
        //     "uniform_size: {:?} categories: {:?}",
        //     self.inner.name(),
        //     self.inner.categories().collect::<Vec<_>>(),
        // );

        if !self
            .inner
            .categories()
            .any(|category| category == SlangParameterCategory::Uniform)
        {
            return None;
        }

        // let category = self.inner.categories().next().unwrap();

        // println!(
        //     "AARGH size Category: {category:?}   Category count: {}",
        //     self.inner.category_count()
        // );

        // Some(self.inner.size(category))

        Some(self.inner.size(SlangParameterCategory::Uniform))
    }

    pub fn stride(&self) -> usize
    {
        self.inner.stride(self.inner.categories().next().unwrap())
    }
}

pub struct TypeReflection<'a>
{
    inner: &'a shader_slang::reflection::Type,
}

impl TypeReflection<'_>
{
    pub fn kind(&self) -> TypeKind
    {
        TypeKind::from_slang_type_kind(self.inner.kind())
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[non_exhaustive]
pub enum TypeKind
{
    None,
    Struct,
    Enum,
    Array,
    Matrix,
    Vector,
    Scalar,
    ConstantBuffer,
    Resource,
    SamplerState,
    TextureBuffer,
    ShaderStorageBuffer,
    ParameterBlock,
    GenericTypeParameter,
    Interface,
    OutputStream,
    MeshOutput,
    Specialized,
    Feedback,
    Pointer,
    DynamicResource,
    Count,
}

impl TypeKind
{
    fn from_slang_type_kind(type_kind: SlangTypeKind) -> Self
    {
        match type_kind {
            SlangTypeKind::None => Self::None,
            SlangTypeKind::Struct => Self::Struct,
            SlangTypeKind::Enum => Self::Enum,
            SlangTypeKind::Array => Self::Array,
            SlangTypeKind::Matrix => Self::Matrix,
            SlangTypeKind::Vector => Self::Vector,
            SlangTypeKind::Scalar => Self::Scalar,
            SlangTypeKind::ConstantBuffer => Self::ConstantBuffer,
            SlangTypeKind::Resource => Self::Resource,
            SlangTypeKind::SamplerState => Self::SamplerState,
            SlangTypeKind::TextureBuffer => Self::TextureBuffer,
            SlangTypeKind::ShaderStorageBuffer => Self::ShaderStorageBuffer,
            SlangTypeKind::ParameterBlock => Self::ParameterBlock,
            SlangTypeKind::GenericTypeParameter => Self::GenericTypeParameter,
            SlangTypeKind::Interface => Self::Interface,
            SlangTypeKind::OutputStream => Self::OutputStream,
            SlangTypeKind::MeshOutput => Self::MeshOutput,
            SlangTypeKind::Specialized => Self::Specialized,
            SlangTypeKind::Feedback => Self::Feedback,
            SlangTypeKind::Pointer => Self::Pointer,
            SlangTypeKind::DynamicResource => Self::DynamicResource,
            SlangTypeKind::Count => Self::Count,
        }
    }
}

pub struct Blob
{
    inner: SlangBlob,
}

impl Blob
{
    pub fn as_bytes(&self) -> &[u8]
    {
        self.inner.as_slice()
    }

    pub fn as_str(&self) -> Result<&str, Utf8Error>
    {
        self.inner.as_str()
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[non_exhaustive]
pub enum Stage
{
    None,
    Vertex,
    Hull,
    Domain,
    Geometry,
    Fragment,
    Compute,
    RayGeneration,
    Intersection,
    AnyHit,
    ClosestHit,
    Miss,
    Callable,
    Mesh,
    Amplification,
    Dispatch,
    Count,
}

impl Stage
{
    fn from_slang_stage(stage: shader_slang::Stage) -> Self
    {
        match stage {
            shader_slang::Stage::None => Self::None,
            shader_slang::Stage::Vertex => Self::Vertex,
            shader_slang::Stage::Hull => Self::Hull,
            shader_slang::Stage::Domain => Self::Domain,
            shader_slang::Stage::Geometry => Self::Geometry,
            shader_slang::Stage::Fragment => Self::Fragment,
            shader_slang::Stage::Compute => Self::Compute,
            shader_slang::Stage::RayGeneration => Self::RayGeneration,
            shader_slang::Stage::Intersection => Self::Intersection,
            shader_slang::Stage::AnyHit => Self::AnyHit,
            shader_slang::Stage::ClosestHit => Self::ClosestHit,
            shader_slang::Stage::Miss => Self::Miss,
            shader_slang::Stage::Callable => Self::Callable,
            shader_slang::Stage::Mesh => Self::Mesh,
            shader_slang::Stage::Amplification => Self::Amplification,
            shader_slang::Stage::Dispatch => Self::Dispatch,
            shader_slang::Stage::Count => Self::Count,
        }
    }
}

builder! {
#[builder(name = SettingsBuilder, derives=(Debug))]
#[derive(Debug)]
#[non_exhaustive]
pub struct Settings
{
    link_entrypoints: EntrypointFlags,
}
}

#[derive(Sole)]
pub struct Context
{
    _global_session: SlangGlobalSession,
    session: SlangSession,
    modules: HashMap<AssetId, Module>,
    programs: HashMap<AssetId, Program>,
}

impl Context
{
    pub fn get_module(&self, asset_id: &AssetId) -> Option<&Module>
    {
        self.modules.get(asset_id)
    }

    pub fn get_program(&self, asset_id: &AssetId) -> Option<&Program>
    {
        self.programs.get(asset_id)
    }

    pub fn compose_into_program(
        &self,
        modules: &[&Module],
        entry_points: &[&EntryPoint],
    ) -> Result<Program, Error>
    {
        let components =
            modules
                .iter()
                .map(|module| SlangComponentType::from(module.inner.clone()))
                .chain(entry_points.iter().map(|entry_point| {
                    SlangComponentType::from(entry_point.inner.clone())
                }))
                .collect::<Vec<_>>();

        let program = self.session.create_composite_component_type(&components)?;

        Ok(Program { inner: program })
    }
}

#[derive(Debug, thiserror::Error)]
#[error(transparent)]
pub struct Error(#[from] shader_slang::Error);

pub(crate) fn add_asset_importers(assets: &mut Assets)
{
    assets.set_importer::<_, _>(["slang"], import_slang_asset);
}

fn import_slang_asset(
    asset_submitter: &mut AssetSubmitter<'_>,
    file_path: &Path,
    settings: Option<&'_ Settings>,
) -> Result<(), ImportError>
{
    let file_name = file_path
        .file_name()
        .ok_or(ImportError::NoPathFileName)?
        .to_str()
        .ok_or(ImportError::PathFileNameNotUtf8)?;

    let file_path_canonicalized = file_path
        .canonicalize()
        .map_err(ImportError::CanonicalizePathFailed)?;

    asset_submitter.submit_store(ModuleSource {
        name: file_name.to_owned().into(),
        file_path: file_path_canonicalized.into(),
        source: std::fs::read_to_string(file_path)
            .map_err(ImportError::ReadFileFailed)?
            .into(),
        link_entrypoints: settings
            .map(|settings| settings.link_entrypoints)
            .unwrap_or_default(),
    });

    Ok(())
}

#[derive(Debug, thiserror::Error)]
enum ImportError
{
    #[error("Failed to read file")]
    ReadFileFailed(#[source] std::io::Error),

    #[error("Asset path does not have a file name")]
    NoPathFileName,

    #[error("Asset path file name is not valid UTF8")]
    PathFileNameNotUtf8,

    #[error("Failed to canonicalize asset path")]
    CanonicalizePathFailed(#[source] std::io::Error),
}

declare_entity!(
    IMPORT_SHADERS_PHASE,
    (
        Phase,
        Pair::builder()
            .relation::<ChildOf>()
            .target_id(*HANDLE_ASSETS_PHASE)
            .build()
    )
);

pub(crate) struct Extension;

impl ecs::extension::Extension for Extension
{
    fn collect(self, mut collector: ecs::extension::Collector<'_>)
    {
        let Some(global_session) = SlangGlobalSession::new() else {
            tracing::error!("Unable to create global shader-slang session");
            return;
        };

        let session_options = shader_slang::CompilerOptions::default()
            .optimization(shader_slang::OptimizationLevel::None)
            .matrix_layout_column(true)
            .debug_information(SlangDebugInfoLevel::Maximal)
            .no_mangle(true);

        let target_desc = shader_slang::TargetDesc::default()
            .format(shader_slang::CompileTarget::Glsl)
            // .format(shader_slang::CompileTarget::Spirv)
            .profile(global_session.find_profile("glsl_330"));
        // .profile(global_session.find_profile("spirv_1_5"));

        let targets = [target_desc];

        let session_desc = shader_slang::SessionDesc::default()
            .targets(&targets)
            .search_paths(&[""])
            .options(&session_options);

        let Some(session) = global_session.create_session(&session_desc) else {
            tracing::error!("Failed to create shader-slang session");
            return;
        };

        collector
            .add_sole(Context {
                _global_session: global_session,
                session,
                modules: HashMap::new(),
                programs: HashMap::new(),
            })
            .ok();

        collector.add_declared_entity(&IMPORT_SHADERS_PHASE);

        collector.add_system(*START_PHASE, initialize);
        collector.add_system(*IMPORT_SHADERS_PHASE, load_modules);

        collector.add_system(
            *PRE_RENDER_PHASE,
            default_shader_enqueue_set_shader_bindings,
        );
    }
}

fn initialize(mut assets: Single<Assets>)
{
    assets.store_with_label(
        ASSET_LABEL.clone(),
        ModuleSource {
            name: "default_shader.slang".into(),
            file_path: Path::new("@engine/default_shader").into(),
            source: include_str!("../res/default_shader.slang").into(),
            link_entrypoints: EntrypointFlags::VERTEX | EntrypointFlags::FRAGMENT,
        },
    );
}

#[tracing::instrument(skip_all)]
fn load_modules(mut context: Single<Context>, assets: Single<Assets>)
{
    for AssetEvent::Stored(asset_id, asset_label) in assets.events().last_tick_events() {
        let asset_handle = AssetHandle::<ModuleSource>::from_id(*asset_id);

        if !assets.is_loaded_and_has_type(&asset_handle) {
            continue;
        }

        let Some(module_source) = assets.get(&asset_handle) else {
            unreachable!();
        };

        tracing::debug!(asset_label=?asset_label, "Loading shader module");

        let module = match load_module(&context.session, module_source) {
            Ok(module) => module,
            Err(err) => {
                tracing::error!("Failed to load shader module: {err}");
                continue;
            }
        };

        if !module_source.link_entrypoints.is_empty() {
            assert!(context.programs.get(asset_id).is_none());

            let Some(vertex_shader_entry_point) = module.get_entry_point("vertex_main")
            else {
                tracing::error!(
                    "Shader module does not contain a vertex shader entry point"
                );
                continue;
            };

            let Some(fragment_shader_entry_point) =
                module.get_entry_point("fragment_main")
            else {
                tracing::error!(
                    "Shader module don't contain a fragment_main entry point"
                );
                continue;
            };

            let shader_program = match context.compose_into_program(
                &[&module],
                &[&vertex_shader_entry_point, &fragment_shader_entry_point],
            ) {
                Ok(shader_program) => shader_program,
                Err(err) => {
                    tracing::error!("Failed to compose shader into program: {err}");
                    continue;
                }
            };

            let linked_shader_program = match shader_program.link() {
                Ok(linked_shader_program) => linked_shader_program,
                Err(err) => {
                    tracing::error!("Failed to link shader: {err}");
                    continue;
                }
            };

            context.programs.insert(*asset_id, linked_shader_program);
        }

        context.modules.insert(*asset_id, module);
    }
}

fn load_module(
    session: &SlangSession,
    module_source: &ModuleSource,
) -> Result<Module, Error>
{
    let module = session.load_module_from_source_string(
        &module_source.name,
        &module_source.file_path.to_string_lossy(),
        &module_source.source,
    )?;

    Ok(Module { inner: module })
}