#![cfg(target_arch = "wasm32")]

/*
    Copyright 2022 Loophole Labs

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

           http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
*/

use crate::context::Context;
use crate::http_signature::{Decode, Encode, HttpContext};
use crate::request::Request;
use crate::response::Response;
use scale_signature::{Context as ContextTrait, GuestContext as GuestContextTrait};
use std::io::Cursor;

pub static mut READ_BUFFER: Vec<u8> = Vec::new();
pub static mut WRITE_BUFFER: Vec<u8> = Vec::new();

pub type GuestContext = Context;

impl ContextTrait for Context {
    fn guest_context(&mut self) -> &mut dyn GuestContextTrait {
        self
    }
}

impl GuestContextTrait for GuestContext {
    unsafe fn to_write_buffer(&mut self) -> (u32, u32) {
        let mut cursor = Cursor::new(Vec::new());
        cursor = match HttpContext::encode(&self.generated, &mut cursor) {
            Ok(_) => cursor,
            Err(err) => return self.error_write_buffer(err),
        };

        let vec = cursor.into_inner();

        WRITE_BUFFER.resize(vec.len() as usize, 0);
        WRITE_BUFFER.copy_from_slice(&vec);

        return (WRITE_BUFFER.as_ptr() as u32, WRITE_BUFFER.len() as u32);
    }

    unsafe fn error_write_buffer(&mut self, error: Box<dyn std::error::Error>) -> (u32, u32) {
        let mut cursor = Cursor::new(Vec::new());
        Encode::internal_error(&self.generated, &mut cursor, error);

        let vec = cursor.into_inner();

        WRITE_BUFFER.resize(vec.len() as usize, 0);
        WRITE_BUFFER.copy_from_slice(&vec);

        return (WRITE_BUFFER.as_ptr() as u32, WRITE_BUFFER.len() as u32);
    }

    unsafe fn from_read_buffer(&mut self) -> Option<Box<dyn std::error::Error>> {
        let mut cursor = Cursor::new(&mut READ_BUFFER);
        let result = HttpContext::decode(&mut cursor);
        return match result {
            Ok(context) => {
                self.generated = context.unwrap();
                None
            }
            Err(e) => Some(e),
        };
    }
}

impl Context {
    pub fn next(&mut self) -> Result<&mut Self, Box<dyn std::error::Error>> {
        unsafe {
            let (ptr, len) = self.to_write_buffer();
            _next(ptr, len);
            return match self.from_read_buffer() {
                Some(err) => Err(err),
                None => Ok(self),
            };
        }
    }

    pub fn request(&mut self) -> &mut Request {
        &mut self.generated.request as &mut Request
    }

    pub fn response(&mut self) -> &mut Response {
        &mut self.generated.response as &mut Response
    }
}

pub unsafe fn resize(size: u32) -> *const u8 {
    READ_BUFFER.resize(size as usize, 0);
    return READ_BUFFER.as_ptr();
}

#[link(wasm_import_module = "env")]
extern "C" {
    #[link_name = "next"]
    fn _next(ptr: u32, size: u32);
}