extern crate wasmer_runtime;
extern crate wasmer_runtime_core;

use libc::{c_char, c_int, int32_t, int64_t, uint32_t, uint8_t};
use std::cell::RefCell;
use std::error::Error;
use std::ffi::CStr;
use std::fmt;
use std::slice;
use std::str;
use std::sync::Arc;
use std::{ffi::c_void, mem, ptr};
use wasmer_runtime::{Ctx, Global, ImportObject, Instance, Memory, Table, Value};
use wasmer_runtime_core::export::{Context, Export, FuncPointer};
use wasmer_runtime_core::import::{LikeNamespace, Namespace};
use wasmer_runtime_core::types::{
    ElementType, FuncSig, GlobalDescriptor, MemoryDescriptor, TableDescriptor, Type,
};
use wasmer_runtime_core::units::{Bytes, Pages};

#[allow(non_camel_case_types)]
pub struct wasmer_import_object_t();

#[allow(non_camel_case_types)]
pub struct wasmer_instance_t();

#[allow(non_camel_case_types)]
pub struct wasmer_instance_context_t();

#[allow(non_camel_case_types)]
#[no_mangle]
#[repr(C)]
pub enum wasmer_result_t {
    WASMER_OK = 1,
    WASMER_ERROR = 2,
}

#[repr(u32)]
#[derive(Clone)]
pub enum wasmer_value_tag {
    WASM_I32,
    WASM_I64,
    WASM_F32,
    WASM_F64,
}

#[repr(C)]
#[derive(Clone, Copy)]
pub union wasmer_value {
    I32: int32_t,
    I64: int64_t,
    F32: f32,
    F64: f64,
}

#[repr(C)]
#[derive(Clone)]
pub struct wasmer_value_t {
    tag: wasmer_value_tag,
    value: wasmer_value,
}

#[repr(C)]
#[derive(Clone)]
pub struct wasmer_global_descriptor_t {
    mutable: bool,
    kind: wasmer_value_tag,
}

#[repr(C)]
#[derive(Clone)]
pub struct wasmer_memory_t();

#[repr(C)]
#[derive(Clone)]
pub struct wasmer_table_t();

#[repr(C)]
#[derive(Clone)]
pub struct wasmer_global_t();

#[repr(C)]
pub struct wasmer_limits_t {
    pub min: uint32_t,
    pub max: uint32_t,
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub unsafe extern "C" fn wasmer_validate(
    wasm_bytes: *mut uint8_t,
    wasm_bytes_len: uint32_t,
) -> bool {
    if wasm_bytes.is_null() {
        return false;
    }
    let bytes: &[u8] =
        unsafe { ::std::slice::from_raw_parts_mut(wasm_bytes, wasm_bytes_len as usize) };
    wasmer_runtime_core::validate(bytes)
}

#[no_mangle]
pub extern "C" fn wasmer_import_object_new() -> *mut wasmer_import_object_t {
    Box::into_raw(Box::new(ImportObject::new())) as *mut wasmer_import_object_t
}

#[no_mangle]
pub unsafe extern "C" fn wasmer_memory_new(
    mut memory: *mut *mut wasmer_memory_t,
    limits: wasmer_limits_t,
) -> wasmer_result_t {
    let desc = MemoryDescriptor {
        minimum: Pages(limits.min),
        maximum: Some(Pages(limits.max)),
        shared: false,
    };
    let result = Memory::new(desc);
    let new_memory = match result {
        Ok(memory) => memory,
        Err(error) => {
            update_last_error(error);
            return wasmer_result_t::WASMER_ERROR;
        }
    };
    unsafe { *memory = Box::into_raw(Box::new(new_memory)) as *mut wasmer_memory_t };
    wasmer_result_t::WASMER_OK
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_memory_grow(
    memory: *mut wasmer_memory_t,
    delta: uint32_t,
) -> wasmer_result_t {
    let memory = unsafe { Box::from_raw(memory as *mut Memory) };
    let maybe_delta = memory.grow(Pages(delta));
    Box::into_raw(memory);
    if let Some(_delta) = maybe_delta {
        wasmer_result_t::WASMER_OK
    } else {
        update_last_error(CApiError {
            msg: "unable to grow memory".to_string(),
        });
        wasmer_result_t::WASMER_ERROR
    }
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_memory_length(memory: *mut wasmer_memory_t) -> uint32_t {
    let memory = unsafe { Box::from_raw(memory as *mut Memory) };
    let Pages(len) = memory.size();
    Box::into_raw(memory);
    len
}

#[no_mangle]
pub unsafe extern "C" fn wasmer_table_new(
    mut table: *mut *mut wasmer_table_t,
    limits: wasmer_limits_t,
) -> wasmer_result_t {
    let desc = TableDescriptor {
        element: ElementType::Anyfunc,
        minimum: limits.min,
        maximum: Some(limits.max),
    };
    let result = Table::new(desc);
    let new_table = match result {
        Ok(table) => table,
        Err(error) => {
            update_last_error(error);
            return wasmer_result_t::WASMER_ERROR;
        }
    };
    unsafe { *table = Box::into_raw(Box::new(new_table)) as *mut wasmer_table_t };
    wasmer_result_t::WASMER_OK
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_table_grow(
    table: *mut wasmer_table_t,
    delta: uint32_t,
) -> wasmer_result_t {
    let table = unsafe { Box::from_raw(table as *mut Table) };
    let maybe_delta = table.grow(delta);
    Box::into_raw(table);
    if let Some(_delta) = maybe_delta {
        wasmer_result_t::WASMER_OK
    } else {
        update_last_error(CApiError {
            msg: "unable to grow table".to_string(),
        });
        wasmer_result_t::WASMER_ERROR
    }
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_table_length(table: *mut wasmer_table_t) -> uint32_t {
    let table = unsafe { Box::from_raw(table as *mut Table) };
    let len = table.size();
    Box::into_raw(table);
    len
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_table_destroy(table: *mut wasmer_table_t) {
    if !table.is_null() {
        drop(unsafe { Box::from_raw(table as *mut Table) });
    }
}

#[no_mangle]
pub unsafe extern "C" fn wasmer_global_new(
    value: wasmer_value_t,
    mutable: bool,
) -> *mut wasmer_global_t {
    let global = if mutable {
        Global::new_mutable(value.into())
    } else {
        Global::new(value.into())
    };
    unsafe { Box::into_raw(Box::new(global)) as *mut wasmer_global_t }
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_global_get(global: *mut wasmer_global_t) -> wasmer_value_t {
    let global = unsafe { Box::from_raw(global as *mut Global) };
    let value: wasmer_value_t = global.get().into();
    Box::into_raw(global);
    value
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_global_set(global: *mut wasmer_global_t, value: wasmer_value_t) {
    let global = unsafe { Box::from_raw(global as *mut Global) };
    global.set(value.into());
    Box::into_raw(global);
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_global_get_descriptor(
    global: *mut wasmer_global_t,
) -> wasmer_global_descriptor_t {
    let global = unsafe { Box::from_raw(global as *mut Global) };
    let descriptor = global.descriptor();
    let desc = wasmer_global_descriptor_t {
        mutable: descriptor.mutable,
        kind: descriptor.ty.into(),
    };
    Box::into_raw(global);
    desc
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_global_destroy(global: *mut wasmer_global_t) {
    if !global.is_null() {
        drop(unsafe { Box::from_raw(global as *mut Global) });
    }
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_import_object_destroy(import_object: *mut wasmer_import_object_t) {
    if !import_object.is_null() {
        drop(unsafe { Box::from_raw(import_object as *mut ImportObject) });
    }
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_memory_destroy(memory: *mut wasmer_memory_t) {
    if !memory.is_null() {
        drop(unsafe { Box::from_raw(memory as *mut Memory) });
    }
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub unsafe extern "C" fn wasmer_instantiate(
    mut instance: *mut *mut wasmer_instance_t,
    wasm_bytes: *mut uint8_t,
    wasm_bytes_len: uint32_t,
    import_object: *mut wasmer_import_object_t,
) -> wasmer_result_t {
    let import_object = unsafe { Box::from_raw(import_object as *mut ImportObject) };
    if wasm_bytes.is_null() {
        update_last_error(CApiError {
            msg: "wasm bytes ptr is null".to_string(),
        });
        return wasmer_result_t::WASMER_ERROR;
    }
    let bytes: &[u8] =
        unsafe { ::std::slice::from_raw_parts_mut(wasm_bytes, wasm_bytes_len as usize) };
    let result = wasmer_runtime::instantiate(bytes, &*import_object);
    let new_instance = match result {
        Ok(instance) => instance,
        Err(error) => {
            // TODO the trait bound `wasmer_runtime::error::Error: std::error::Error` is not satisfied
            //update_last_error(error);
            update_last_error(CApiError {
                msg: "error instantiating".to_string(),
            });
            return wasmer_result_t::WASMER_ERROR;
        }
    };
    unsafe { *instance = Box::into_raw(Box::new(new_instance)) as *mut wasmer_instance_t };
    Box::into_raw(import_object);
    wasmer_result_t::WASMER_OK
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub unsafe extern "C" fn wasmer_instance_call(
    instance: *mut wasmer_instance_t,
    name: *const c_char,
    params: *const wasmer_value_t,
    params_len: c_int,
    results: *mut wasmer_value_t,
    results_len: c_int,
) -> wasmer_result_t {
    if instance.is_null() {
        update_last_error(CApiError {
            msg: "instance ptr is null".to_string(),
        });
        return wasmer_result_t::WASMER_ERROR;
    }
    if name.is_null() {
        update_last_error(CApiError {
            msg: "name ptr is null".to_string(),
        });
        return wasmer_result_t::WASMER_ERROR;
    }
    if params.is_null() {
        update_last_error(CApiError {
            msg: "params ptr is null".to_string(),
        });
        return wasmer_result_t::WASMER_ERROR;
    }

    let params: &[wasmer_value_t] = slice::from_raw_parts(params, params_len as usize);
    let params: Vec<Value> = params.iter().cloned().map(|x| x.into()).collect();

    let func_name_c = unsafe { CStr::from_ptr(name) };
    let func_name_r = func_name_c.to_str().unwrap();
    let instance = unsafe { Box::from_raw(instance as *mut Instance) };

    let results: &mut [wasmer_value_t] = slice::from_raw_parts_mut(results, results_len as usize);
    let result = instance.call(func_name_r, &params[..]);
    Box::into_raw(instance);
    match result {
        Ok(results_vec) => {
            println!("Call Res: {:?}", results_vec);
            if results_vec.len() > 0 {
                let ret = match results_vec[0] {
                    Value::I32(x) => wasmer_value_t {
                        tag: wasmer_value_tag::WASM_I32,
                        value: wasmer_value { I32: x },
                    },
                    Value::I64(x) => wasmer_value_t {
                        tag: wasmer_value_tag::WASM_I64,
                        value: wasmer_value { I64: x },
                    },
                    Value::F32(x) => wasmer_value_t {
                        tag: wasmer_value_tag::WASM_F32,
                        value: wasmer_value { F32: x },
                    },
                    Value::F64(x) => wasmer_value_t {
                        tag: wasmer_value_tag::WASM_F64,
                        value: wasmer_value { F64: x },
                    },
                };
                results[0] = ret;
            }
            wasmer_result_t::WASMER_OK
        }
        Err(err) => {
            update_last_error(err);
            wasmer_result_t::WASMER_ERROR
        }
    }
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub unsafe extern "C" fn wasmer_imports_set_import_func(
    import_object: *mut wasmer_import_object_t,
    namespace: *const c_char,
    name: *const c_char,
    func: extern "C" fn(data: *mut c_void),
    params: *const wasmer_value_tag,
    params_len: c_int,
    returns: *const wasmer_value_tag,
    returns_len: c_int,
) {
    let mut import_object = unsafe { Box::from_raw(import_object as *mut ImportObject) };
    let namespace_c = unsafe { CStr::from_ptr(namespace) };
    let namespace_r = namespace_c.to_str().unwrap();
    let name_c = unsafe { CStr::from_ptr(name) };
    let name_r = name_c.to_str().unwrap();

    let params: &[wasmer_value_tag] = slice::from_raw_parts(params, params_len as usize);
    let params: Vec<Type> = params.iter().cloned().map(|x| x.into()).collect();
    let returns: &[wasmer_value_tag] = slice::from_raw_parts(returns, returns_len as usize);
    let returns: Vec<Type> = returns.iter().cloned().map(|x| x.into()).collect();

    let export = Export::Function {
        func: unsafe { FuncPointer::new(func as _) },
        ctx: Context::Internal,
        signature: Arc::new(FuncSig::new(params, returns)),
    };

    // TODO handle existing namespace
    //    let maybe_namespace = import_object.get_namespace(namespace_r);
    //    if let Some(n) = maybe_namespace {
    //        n.insert(name_r, export);
    //    } else {
    let mut namespace = Namespace::new();
    namespace.insert(name_r, export);
    import_object.register(namespace_r, namespace);
    Box::into_raw(import_object);
    //    };
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_instance_context_memory(
    ctx: *mut wasmer_instance_context_t,
    memory_idx: uint32_t,
) -> *const wasmer_memory_t {
    let mut ctx = unsafe { Box::from_raw(ctx as *mut Ctx) };
    let memory = ctx.memory(0);
    memory as *const Memory as *const wasmer_memory_t
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_memory_data(mem: *mut wasmer_memory_t) -> *mut uint8_t {
    let memory = mem as *mut Memory;
    use std::cell::Cell;
    unsafe { ((*memory).view::<u8>()[..]).as_ptr() as *mut Cell<u8> as *mut u8 }
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_memory_data_length(mem: *mut wasmer_memory_t) -> uint32_t {
    let memory = mem as *mut Memory;
    let Bytes(len) = unsafe { (*memory).size().bytes() };
    len as uint32_t
}

#[allow(clippy::cast_ptr_alignment)]
#[no_mangle]
pub extern "C" fn wasmer_instance_destroy(instance: *mut wasmer_instance_t) {
    if !instance.is_null() {
        drop(unsafe { Box::from_raw(instance as *mut Instance) });
    }
}

impl From<wasmer_value_t> for Value {
    fn from(v: wasmer_value_t) -> Self {
        unsafe {
            match v {
                wasmer_value_t {
                    tag: WASM_I32,
                    value: wasmer_value { I32 },
                } => Value::I32(I32),
                wasmer_value_t {
                    tag: WASM_I64,
                    value: wasmer_value { I64 },
                } => Value::I64(I64),
                wasmer_value_t {
                    tag: WASM_F32,
                    value: wasmer_value { F32 },
                } => Value::F32(F32),
                wasmer_value_t {
                    tag: WASM_F64,
                    value: wasmer_value { F64 },
                } => Value::F64(F64),
                _ => panic!("not implemented"),
            }
        }
    }
}

impl From<Value> for wasmer_value_t {
    fn from(val: Value) -> Self {
        match val {
            Value::I32(x) => wasmer_value_t {
                tag: wasmer_value_tag::WASM_I32,
                value: wasmer_value { I32: x },
            },
            Value::I64(x) => wasmer_value_t {
                tag: wasmer_value_tag::WASM_I64,
                value: wasmer_value { I64: x },
            },
            Value::F32(x) => wasmer_value_t {
                tag: wasmer_value_tag::WASM_F32,
                value: wasmer_value { F32: x },
            },
            Value::F64(x) => wasmer_value_t {
                tag: wasmer_value_tag::WASM_F64,
                value: wasmer_value { F64: x },
            },
        }
    }
}

impl From<Type> for wasmer_value_tag {
    fn from(ty: Type) -> Self {
        match ty {
            Type::I32 => wasmer_value_tag::WASM_I32,
            Type::I64 => wasmer_value_tag::WASM_I64,
            Type::F32 => wasmer_value_tag::WASM_F32,
            Type::F64 => wasmer_value_tag::WASM_F64,
            _ => panic!("not implemented"),
        }
    }
}

impl From<wasmer_value_tag> for Type {
    fn from(v: wasmer_value_tag) -> Self {
        unsafe {
            match v {
                wasmer_value_tag::WASM_I32 => Type::I32,
                wasmer_value_tag::WASM_I64 => Type::I64,
                wasmer_value_tag::WASM_F32 => Type::F32,
                wasmer_value_tag::WASM_F64 => Type::F64,
                _ => panic!("not implemented"),
            }
        }
    }
}

// Error reporting

thread_local! {
    static LAST_ERROR: RefCell<Option<Box<Error>>> = RefCell::new(None);
}

fn update_last_error<E: Error + 'static>(err: E) {
    LAST_ERROR.with(|prev| {
        *prev.borrow_mut() = Some(Box::new(err));
    });
}

/// Retrieve the most recent error, clearing it in the process.
fn take_last_error() -> Option<Box<Error>> {
    LAST_ERROR.with(|prev| prev.borrow_mut().take())
}

#[no_mangle]
pub extern "C" fn wasmer_last_error_length() -> c_int {
    LAST_ERROR.with(|prev| match *prev.borrow() {
        Some(ref err) => err.to_string().len() as c_int + 1,
        None => 0,
    })
}

#[no_mangle]
pub unsafe extern "C" fn wasmer_last_error_message(buffer: *mut c_char, length: c_int) -> c_int {
    if buffer.is_null() {
        // buffer pointer is null
        return -1;
    }

    let last_error = match take_last_error() {
        Some(err) => err,
        None => return 0,
    };

    let error_message = last_error.to_string();

    let buffer = slice::from_raw_parts_mut(buffer as *mut u8, length as usize);

    if error_message.len() >= buffer.len() {
        // buffer to small for err  message
        return -1;
    }

    ptr::copy_nonoverlapping(
        error_message.as_ptr(),
        buffer.as_mut_ptr(),
        error_message.len(),
    );

    // Add a trailing null so people using the string as a `char *` don't
    // accidentally read into garbage.
    buffer[error_message.len()] = 0;

    error_message.len() as c_int
}

#[derive(Debug)]
struct CApiError {
    msg: String,
}

impl fmt::Display for CApiError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", &self.msg)
    }
}

impl Error for CApiError {}