//
// Wildland Project
//
// Copyright © 2022 Golem Foundation,
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 3 as published by
// the Free Software Foundation.
//
// This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.

use std::fmt::Display;

use convert_case::{Case, Casing};
use syn::punctuated::Punctuated;
use syn::token::Comma;
use syn::{Field, ItemEnum, Variant};

use super::templates::TargetLanguageTypeName;
use crate::binding_types::RustWrapperType;
use crate::cpp::FunctionVirtualTranslator;
use crate::enum_helpers::{
    enum_tag_name,
    field_name,
    get_fields,
    is_ignored_variant,
    is_many_fields_variant,
    is_primitive_enum,
    variant_wrapper_ident,
};
use crate::extern_module_translator::ExternModuleTranslator;

const WASM_EXCEPTION_CLASS_NAME: &str = "RustException";
const CPP_WASM_EXCEPTION_CLASS_NAME: &str = "WasmException";

pub fn create_wasm_module(extern_module_translator: &ExternModuleTranslator) -> String {
    let enum_classes = translate_enums(extern_module_translator);
    let user_classes = create_user_classes(extern_module_translator);
    let rust_wrappers = create_rust_wrappers(extern_module_translator);
    let abstract_classes_wrappers: String = create_custom_traits_wrappers(extern_module_translator);
    let abstract_classes_gluecode = create_custom_traits_gluecode(extern_module_translator);
    let classes: String = rust_wrappers
        .chain(user_classes)
        .chain(abstract_classes_gluecode)
        .collect();
    let global_functions: String = extern_module_translator
        .global_functions
        .iter()
        .map(|f| global_def_template(&f.name.to_string()))
        .collect();
    let exception_class_enum = enum_class_bindings(
        "ExceptionClass",
        extern_module_translator.exception_names.iter(),
    );
    let exception_trait_methods = extern_module_translator
        .exception_trait_methods
        .iter()
        .map(|fun| class_method(&fun.name, CPP_WASM_EXCEPTION_CLASS_NAME))
        .collect::<Vec<_>>()
        .join("\n");
    let exception_class = class_template(
        CPP_WASM_EXCEPTION_CLASS_NAME,
        &(class_constructor("unsigned")
            + &class_method("exception_class", CPP_WASM_EXCEPTION_CLASS_NAME)
            + &class_method("what", CPP_WASM_EXCEPTION_CLASS_NAME)
            + &exception_trait_methods),
        WASM_EXCEPTION_CLASS_NAME,
    );
    generate_cpp_code_for_wasm(
        &abstract_classes_wrappers,
        &classes,
        &global_functions,
        &enum_classes,
        &exception_class_enum,
        &exception_class,
    )
}

fn translate_enums(emt: &ExternModuleTranslator) -> String {
    let (fieldless_enums, data_enums): (Vec<&ItemEnum>, Vec<&ItemEnum>) = emt
        .shared_enums
        .iter()
        .partition(|enum_item| is_primitive_enum(enum_item));
    let fieldless_enums_bindings = fieldless_enums
        .into_iter()
        .map(|enum_item| {
            enum_class_bindings(
                &enum_item.ident,
                enum_item.variants.iter().map(|variant| &variant.ident),
            )
        })
        .collect::<String>();
    let data_enums_bindings = data_enums
        .into_iter()
        .map(data_enum_emscripten_bindings)
        .collect::<String>();
    format!(
        "{fieldless_enums_bindings}
{data_enums_bindings}"
    )
}

fn data_enum_emscripten_bindings(enum_item: &ItemEnum) -> String {
    let tag_enum = tag_enum_bindings(enum_item);
    let payload_object_values = create_variant_object_values(enum_item);
    let enum_struct = enum_object_class_bindings(enum_item);

    format!("{enum_struct}{payload_object_values}{tag_enum}")
}

fn create_variant_object_values(enum_item: &ItemEnum) -> String {
    let enum_name = &enum_item.ident;
    enum_item
        .variants
        .iter()
        .filter(|v| is_many_fields_variant(v))
        .map(|v| create_variant_object_value(v, &variant_wrapper_ident(enum_name, &v.ident)))
        .collect::<Vec<String>>()
        .join("\n")
}

fn create_variant_object_value(
    variant: &Variant,
    variant_wrapper_name: impl Display + Copy,
) -> String {
    let field_getters = field_getters(get_fields(variant).unwrap(), variant_wrapper_name);
    format!(
        "
EMSCRIPTEN_BINDINGS({variant_wrapper_name}) {{
    emscripten::class_<{variant_wrapper_name}>(\"{variant_wrapper_name}\")
{field_getters}
        ;
}}
"
    )
}

fn field_getters(fields: &Punctuated<Field, Comma>, struct_name: impl Display) -> String {
    fields
        .iter()
        .enumerate()
        .map(|(idx, field)| {
            let field_name = field_name(field).unwrap_or(format!("_{idx}"));
            let field_name = if let Some(stripped) = field_name.strip_prefix('_') {
                stripped
            } else {
                &field_name
            };
            format!("        .function(\"get_{field_name}\", &{struct_name}::get_{field_name})")
        })
        .collect::<Vec<_>>()
        .join("\n")
}

fn enum_object_class_bindings(enum_item: &ItemEnum) -> String {
    let enum_name = &enum_item.ident;
    let variant_getters = create_enum_variant_getters(enum_item);
    format!(
        "
EMSCRIPTEN_BINDINGS({enum_name}) {{
    emscripten::class_<{enum_name}>(\"{enum_name}\")
        .function(\"get_tag\", &{enum_name}::get_tag)
{variant_getters}
        ;
}}
"
    )
}

fn create_enum_variant_getters(enum_item: &ItemEnum) -> String {
    let enum_name = enum_item.ident.to_string();
    enum_item
        .variants
        .iter()
        .filter_map(|v| create_enum_variant_getter(v, &enum_name))
        .collect::<Vec<_>>()
        .join("\n")
}

fn create_enum_variant_getter(variant: &Variant, enum_name: &str) -> Option<String> {
    match get_fields(variant) {
        Some(_) if !is_ignored_variant(variant) => {
            let variant_name = &variant.ident.to_string().to_case(Case::Snake);
            Some(format!(
                "        .function(\"get_{variant_name}\", &{enum_name}::get_{variant_name})"
            ))
        }
        _ => None,
    }
}

fn tag_enum_bindings(enum_item: &ItemEnum) -> String {
    let enum_name_tag = enum_tag_name(enum_item.ident.to_string().as_str());
    let variants = enum_item
        .variants
        .iter()
        .map(|variant| {
            let variant_ident = &variant.ident;
            format!("        .value(\"{variant_ident}\", {enum_name_tag}::{variant_ident})")
        })
        .collect::<Vec<_>>()
        .join("\n");
    format!(
        "
EMSCRIPTEN_BINDINGS({enum_name_tag}) {{
    emscripten::enum_<{enum_name_tag}>(\"{enum_name_tag}\")
{variants}
        ;
}}
"
    )
}

fn enum_class_bindings<T: Display, U: Display>(
    enum_name: T,
    variants: impl Iterator<Item = U>,
) -> String {
    let variants = variants
        .map(|v| format!("        .value(\"{v}\", {enum_name}::{v})"))
        .collect::<Vec<String>>()
        .join("\n");
    format!(
        "
EMSCRIPTEN_BINDINGS({enum_name}) {{
    emscripten::enum_<{enum_name}>(\"{enum_name}\")
{variants}
        ;
}}
"
    )
}

fn create_user_classes(
    extern_module_translator: &ExternModuleTranslator,
) -> impl Iterator<Item = String> + '_ {
    extern_module_translator
        .user_custom_types
        .iter()
        .map(|(wrapper, functions)| {
            let class_name = wrapper.wrapper_name.to_string();
            let functions: String = functions
                .iter()
                .map(|f| class_method(&f.name.to_string(), &class_name))
                .collect();
            class_template(&class_name, &functions, &class_name)
        })
}

fn create_rust_wrappers(
    extern_module_translator: &ExternModuleTranslator,
) -> impl Iterator<Item = String> + '_ {
    extern_module_translator
        .rust_types_wrappers
        .unordered_iter()
        .map(|wrapper| match &wrapper.rust_type {
            RustWrapperType::Option(inner_type) => {
                let inner_type_generics = inner_type.get_name();
                let inner_type = inner_type.wrapper_name.to_string();
                let class_name = format!("Optional<{inner_type_generics}>");
                let target_name = format!("Optional{inner_type}");
                let functions = [
                    class_constructor(""),
                    class_constructor(&inner_type_generics),
                    class_method("unwrap", &class_name),
                    class_method("is_some", &class_name),
                ]
                .join("");
                class_template(&class_name, &functions, &target_name)
            }
            RustWrapperType::Vector(inner_type) => {
                let inner_type_generics = inner_type.get_name();
                let inner_type = inner_type.wrapper_name.to_string();
                let class_name = format!("RustVec<{inner_type_generics}>");
                let target_name = format!("Vec{inner_type}");
                let functions = [
                    class_constructor(""),
                    class_method("at", &class_name),
                    class_method("size", &class_name),
                    class_method("push", &class_name),
                ]
                .join("");
                class_template(&class_name, &functions, &target_name)
            }
            RustWrapperType::Result(_, _) => {
                let class_name = &wrapper.wrapper_name;
                let functions = [
                    class_function("from_ok", class_name),
                    class_function("from_err", class_name),
                ]
                .join("");
                class_template(class_name, &functions, class_name)
            }
            _ => "".to_owned(),
        })
}

fn create_custom_traits_wrappers(extern_module_translator: &ExternModuleTranslator) -> String {
    extern_module_translator
        .user_traits
        .iter()
        .map(|(wrapper, functions)| {
            let class_name = wrapper.wrapper_name.to_string();
            let functions_calls: String = functions
                .iter()
                .map(|f| FunctionVirtualTranslator::from_virtual_function(f, &class_name))
                .map(|f_helper| {
                    let return_type_string = if let Some(ref wrapper) = f_helper.return_type {
                        wrapper.get_name_for_abstract_method()
                    } else {
                        "void".to_owned()
                    };
                    let function_name = f_helper.function_name;
                    let function_signature = f_helper.generated_virtual_function_signature;
                    let args: String = f_helper.arg_names[1..]
                        .iter()
                        .map(|arg| format!("std::move({arg})"))
                        .collect::<Vec<String>>()
                        .join(", ");
                    virtual_method_call(
                        &function_name,
                        &return_type_string,
                        &function_signature,
                        &args,
                    )
                })
                .collect();
            abstract_class_wrapper(&class_name, &functions_calls)
        })
        .collect()
}

fn create_custom_traits_gluecode(
    extern_module_translator: &ExternModuleTranslator,
) -> impl Iterator<Item = String> + '_ {
    extern_module_translator
        .user_traits
        .iter()
        .map(|(wrapper, functions)| {
            let class_name = wrapper.wrapper_name.to_string();
            let virtual_functions: String = functions
                .iter()
                .map(|function| virtual_function(&function.name.to_string(), &class_name))
                .collect();
            abstract_class(&wrapper.wrapper_name.to_string(), &virtual_functions)
        })
}

fn virtual_method_call(
    function_name: &str,
    return_type: &str,
    function_signature: &str,
    args: &str,
) -> String {
    if args.is_empty() {
        format!(
            "    {return_type} {function_name}({function_signature}) {{
            return call<{return_type}>(\"{function_name}\");
        }}\n"
        )
    } else {
        format!(
            "    {return_type} {function_name}({function_signature}) {{
            return call<{return_type}>(\"{function_name}\", {args});
        }}\n"
        )
    }
}

fn virtual_function(function_name: &str, class_name: &str) -> String {
    format!("    .function(\"{function_name}\", &{class_name}::{function_name}, emscripten::pure_virtual())\n")
}

fn abstract_class_wrapper(class_name: &str, functions_calls: &str) -> String {
    format!(
        "
    struct {class_name}Wrapper : public emscripten::wrapper<{class_name}> {{
        EMSCRIPTEN_WRAPPER({class_name}Wrapper);
{functions_calls}
    }};\n"
    )
}

fn abstract_class(class_name: &str, virtual_functions: &str) -> String {
    format!(
        "
    emscripten::class_<{class_name}>(\"{class_name}\")
{virtual_functions}
        .allow_subclass<{class_name}Wrapper>(\"{class_name}Wrapper\")
    ;\n"
    )
}

fn generate_cpp_code_for_wasm(
    abstract_classes_wrappers: &str,
    classes: &str,
    global_functions: &str,
    enum_classes: &str,
    exception_class_enum: &str,
    exception_class: &str,
) -> String {
    format!(
        "
#ifdef WASM
#include <emscripten/bind.h>
#include <utility>
{exception_class_enum}
{enum_classes}
{abstract_classes_wrappers}

EMSCRIPTEN_BINDINGS(WasmModule) {{
    emscripten::class_<String>(\"String\")
        .constructor<std::string>()
        .function(\"to_string\", &String::to_string)
        ;
{exception_class}
{classes}
{global_functions}
}}
#endif
"
    )
}

fn class_template(class_name: &str, functions: &str, target_name: &str) -> String {
    format!("    emscripten::class_<{class_name}>(\"{target_name}\")\n{functions}    ;\n")
}

fn class_method(function_name: &str, class_name: &str) -> String {
    format!("        .function(\"{function_name}\", &{class_name}::{function_name})\n")
}

fn class_function(function_name: &str, class_name: &str) -> String {
    format!("        .class_function(\"{function_name}\", &{class_name}::{function_name})\n")
}

fn class_constructor(args: &str) -> String {
    format!("        .constructor<{args}>()\n")
}

fn global_def_template(function_name: &str) -> String {
    format!("    emscripten::function(\"{function_name}\", &{function_name});\n")
}

#[cfg(test)]
mod tests {
    use pretty_assertions::assert_eq;

    use super::*;
    use crate::utils::helpers;

    #[test]
    fn test_enum_class_emscripten_bindings() {
        let enum_item = helpers::get_enum_item();
        let emscripten_binding =
            enum_class_bindings(enum_item.ident, enum_item.variants.iter().map(|i| &i.ident));
        let expected = "
EMSCRIPTEN_BINDINGS(En1) {
    emscripten::enum_<En1>(\"En1\")
        .value(\"V1\", En1::V1)
        .value(\"V2\", En1::V2)
        ;
}
";
        assert_eq!(emscripten_binding, expected);
    }
}