use super::ShaderDefVal;
use crate::define_atomic_id;
use bevy_asset::{AssetLoader, AssetPath, Handle, LoadContext, LoadedAsset};
use bevy_reflect::{TypePath, TypeUuid};
use bevy_utils::{tracing::error, BoxedFuture};

use std::{borrow::Cow, marker::Copy};
use thiserror::Error;

define_atomic_id!(ShaderId);

#[derive(Error, Debug)]
pub enum ShaderReflectError {
    #[error(transparent)]
    WgslParse(#[from] naga::front::wgsl::ParseError),
    #[cfg(feature = "shader_format_glsl")]
    #[error("GLSL Parse Error: {0:?}")]
    GlslParse(Vec<naga::front::glsl::Error>),
    #[cfg(feature = "shader_format_spirv")]
    #[error(transparent)]
    SpirVParse(#[from] naga::front::spv::Error),
    #[error(transparent)]
    Validation(#[from] naga::WithSpan<naga::valid::ValidationError>),
}
/// A shader, as defined by its [`ShaderSource`](wgpu::ShaderSource) and [`ShaderStage`](naga::ShaderStage)
/// This is an "unprocessed" shader. It can contain preprocessor directives.
#[derive(Debug, Clone, TypeUuid, TypePath)]
#[uuid = "d95bc916-6c55-4de3-9622-37e7b6969fda"]
pub struct Shader {
    pub path: String,
    pub source: Source,
    pub import_path: ShaderImport,
    pub imports: Vec<ShaderImport>,
    // extra imports not specified in the source string
    pub additional_imports: Vec<naga_oil::compose::ImportDefinition>,
    // any shader defs that will be included when this module is used
    pub shader_defs: Vec<ShaderDefVal>,
}

impl Shader {
    fn preprocess(source: &str, path: &str) -> (ShaderImport, Vec<ShaderImport>) {
        let (import_path, imports, _) = naga_oil::compose::get_preprocessor_data(source);

        let import_path = import_path
            .map(ShaderImport::Custom)
            .unwrap_or_else(|| ShaderImport::AssetPath(path.to_owned()));

        let imports = imports
            .into_iter()
            .map(|import| {
                if import.import.starts_with('\"') {
                    let import = import
                        .import
                        .chars()
                        .skip(1)
                        .take_while(|c| *c != '\"')
                        .collect();
                    ShaderImport::AssetPath(import)
                } else {
                    ShaderImport::Custom(import.import)
                }
            })
            .collect();

        (import_path, imports)
    }

    pub fn from_wgsl(source: impl Into<Cow<'static, str>>, path: impl Into<String>) -> Shader {
        let source = source.into();
        let path = path.into();
        let (import_path, imports) = Shader::preprocess(&source, &path);
        Shader {
            path,
            imports,
            import_path,
            source: Source::Wgsl(source),
            additional_imports: Default::default(),
            shader_defs: Default::default(),
        }
    }

    pub fn from_wgsl_with_defs(
        source: impl Into<Cow<'static, str>>,
        path: impl Into<String>,
        shader_defs: Vec<ShaderDefVal>,
    ) -> Shader {
        Self {
            shader_defs,
            ..Self::from_wgsl(source, path)
        }
    }

    pub fn from_glsl(
        source: impl Into<Cow<'static, str>>,
        stage: naga::ShaderStage,
        path: impl Into<String>,
    ) -> Shader {
        let source = source.into();
        let path = path.into();
        let (import_path, imports) = Shader::preprocess(&source, &path);
        Shader {
            path,
            imports,
            import_path,
            source: Source::Glsl(source, stage),
            additional_imports: Default::default(),
            shader_defs: Default::default(),
        }
    }

    pub fn from_spirv(source: impl Into<Cow<'static, [u8]>>, path: impl Into<String>) -> Shader {
        let path = path.into();
        Shader {
            path: path.clone(),
            imports: Vec::new(),
            import_path: ShaderImport::AssetPath(path),
            source: Source::SpirV(source.into()),
            additional_imports: Default::default(),
            shader_defs: Default::default(),
        }
    }

    pub fn set_import_path<P: Into<String>>(&mut self, import_path: P) {
        self.import_path = ShaderImport::Custom(import_path.into());
    }

    #[must_use]
    pub fn with_import_path<P: Into<String>>(mut self, import_path: P) -> Self {
        self.set_import_path(import_path);
        self
    }

    #[inline]
    pub fn import_path(&self) -> &ShaderImport {
        &self.import_path
    }

    pub fn imports(&self) -> impl ExactSizeIterator<Item = &ShaderImport> {
        self.imports.iter()
    }
}

impl<'a> From<&'a Shader> for naga_oil::compose::ComposableModuleDescriptor<'a> {
    fn from(shader: &'a Shader) -> Self {
        let shader_defs = shader
            .shader_defs
            .iter()
            .map(|def| match def {
                ShaderDefVal::Bool(name, b) => {
                    (name.clone(), naga_oil::compose::ShaderDefValue::Bool(*b))
                }
                ShaderDefVal::Int(name, i) => {
                    (name.clone(), naga_oil::compose::ShaderDefValue::Int(*i))
                }
                ShaderDefVal::UInt(name, i) => {
                    (name.clone(), naga_oil::compose::ShaderDefValue::UInt(*i))
                }
            })
            .collect();

        let as_name = match &shader.import_path {
            ShaderImport::AssetPath(asset_path) => Some(format!("\"{asset_path}\"")),
            ShaderImport::Custom(_) => None,
        };

        naga_oil::compose::ComposableModuleDescriptor {
            source: shader.source.as_str(),
            file_path: &shader.path,
            language: (&shader.source).into(),
            additional_imports: &shader.additional_imports,
            shader_defs,
            as_name,
        }
    }
}

impl<'a> From<&'a Shader> for naga_oil::compose::NagaModuleDescriptor<'a> {
    fn from(shader: &'a Shader) -> Self {
        naga_oil::compose::NagaModuleDescriptor {
            source: shader.source.as_str(),
            file_path: &shader.path,
            shader_type: (&shader.source).into(),
            ..Default::default()
        }
    }
}

#[derive(Debug, Clone)]
pub enum Source {
    Wgsl(Cow<'static, str>),
    Glsl(Cow<'static, str>, naga::ShaderStage),
    SpirV(Cow<'static, [u8]>),
    // TODO: consider the following
    // PrecompiledSpirVMacros(HashMap<HashSet<String>, Vec<u32>>)
    // NagaModule(Module) ... Module impls Serialize/Deserialize
}

impl Source {
    pub fn as_str(&self) -> &str {
        match self {
            Source::Wgsl(s) | Source::Glsl(s, _) => s,
            Source::SpirV(_) => panic!("spirv not yet implemented"),
        }
    }
}

impl From<&Source> for naga_oil::compose::ShaderLanguage {
    fn from(value: &Source) -> Self {
        match value {
            Source::Wgsl(_) => naga_oil::compose::ShaderLanguage::Wgsl,
            Source::Glsl(_, _) => naga_oil::compose::ShaderLanguage::Glsl,
            Source::SpirV(_) => panic!("spirv not yet implemented"),
        }
    }
}

impl From<&Source> for naga_oil::compose::ShaderType {
    fn from(value: &Source) -> Self {
        match value {
            Source::Wgsl(_) => naga_oil::compose::ShaderType::Wgsl,
            Source::Glsl(_, naga::ShaderStage::Vertex) => naga_oil::compose::ShaderType::GlslVertex,
            Source::Glsl(_, naga::ShaderStage::Fragment) => {
                naga_oil::compose::ShaderType::GlslFragment
            }
            Source::Glsl(_, naga::ShaderStage::Compute) => {
                panic!("glsl compute not yet implemented")
            }
            Source::SpirV(_) => panic!("spirv not yet implemented"),
        }
    }
}

#[derive(Default)]
pub struct ShaderLoader;

impl AssetLoader for ShaderLoader {
    fn load<'a>(
        &'a self,
        bytes: &'a [u8],
        load_context: &'a mut LoadContext,
    ) -> BoxedFuture<'a, Result<(), anyhow::Error>> {
        Box::pin(async move {
            let ext = load_context.path().extension().unwrap().to_str().unwrap();

            let shader = match ext {
                "spv" => {
                    Shader::from_spirv(Vec::from(bytes), load_context.path().to_string_lossy())
                }
                "wgsl" => Shader::from_wgsl(
                    String::from_utf8(Vec::from(bytes))?,
                    load_context.path().to_string_lossy(),
                ),
                "vert" => Shader::from_glsl(
                    String::from_utf8(Vec::from(bytes))?,
                    naga::ShaderStage::Vertex,
                    load_context.path().to_string_lossy(),
                ),
                "frag" => Shader::from_glsl(
                    String::from_utf8(Vec::from(bytes))?,
                    naga::ShaderStage::Fragment,
                    load_context.path().to_string_lossy(),
                ),
                "comp" => Shader::from_glsl(
                    String::from_utf8(Vec::from(bytes))?,
                    naga::ShaderStage::Compute,
                    load_context.path().to_string_lossy(),
                ),
                _ => panic!("unhandled extension: {ext}"),
            };

            // collect file dependencies
            let dependencies = shader
                .imports
                .iter()
                .flat_map(|import| {
                    if let ShaderImport::AssetPath(asset_path) = import {
                        Some(asset_path.clone())
                    } else {
                        None
                    }
                })
                .collect::<Vec<_>>();

            let mut asset = LoadedAsset::new(shader);
            for dependency in dependencies {
                asset.add_dependency(dependency.into());
            }

            load_context.set_default_asset(asset);
            Ok(())
        })
    }

    fn extensions(&self) -> &[&str] {
        &["spv", "wgsl", "vert", "frag", "comp"]
    }
}

#[derive(Debug, PartialEq, Eq, Clone, Hash)]
pub enum ShaderImport {
    AssetPath(String),
    Custom(String),
}

impl ShaderImport {
    pub fn module_name(&self) -> Cow<'_, String> {
        match self {
            ShaderImport::AssetPath(s) => Cow::Owned(format!("\"{s}\"")),
            ShaderImport::Custom(s) => Cow::Borrowed(s),
        }
    }
}

/// A reference to a shader asset.
pub enum ShaderRef {
    /// Use the "default" shader for the current context.
    Default,
    /// A handle to a shader stored in the [`Assets<Shader>`](bevy_asset::Assets) resource
    Handle(Handle<Shader>),
    /// An asset path leading to a shader
    Path(AssetPath<'static>),
}

impl From<Handle<Shader>> for ShaderRef {
    fn from(handle: Handle<Shader>) -> Self {
        Self::Handle(handle)
    }
}

impl From<AssetPath<'static>> for ShaderRef {
    fn from(path: AssetPath<'static>) -> Self {
        Self::Path(path)
    }
}

impl From<&'static str> for ShaderRef {
    fn from(path: &'static str) -> Self {
        Self::Path(AssetPath::from(path))
    }
}