use std::ops::{Deref, DerefMut};
use std::ptr;
use std::slice;

use super::{JsObject, NapiValue, Value, ValueType};
use crate::error::check_status;
use crate::{sys, Result};

#[derive(Clone, Copy, Debug)]
pub struct JsBuffer {
  pub value: JsObject,
  pub data: *const u8,
  pub len: u64,
}

impl NapiValue for JsBuffer {
  fn raw_value(&self) -> sys::napi_value {
    self.value.0.value
  }

  fn from_raw(env: sys::napi_env, value: sys::napi_value) -> Result<Self> {
    let mut data = ptr::null_mut();
    let mut len: u64 = 0;
    let status = unsafe { sys::napi_get_buffer_info(env, value, &mut data, &mut len) };
    check_status(status)?;
    Ok(JsBuffer {
      value: JsObject(Value {
        env,
        value,
        value_type: ValueType::Object,
      }),
      data: data as *const u8,
      len,
    })
  }

  fn from_raw_unchecked(env: sys::napi_env, value: sys::napi_value) -> Self {
    Self {
      value: JsObject(Value {
        env,
        value,
        value_type: ValueType::Object,
      }),
      data: ptr::null(),
      len: 0,
    }
  }
}

impl AsRef<[u8]> for JsBuffer {
  fn as_ref(&self) -> &[u8] {
    self.deref()
  }
}

impl Deref for JsBuffer {
  type Target = [u8];

  fn deref(&self) -> &[u8] {
    unsafe { slice::from_raw_parts(self.data, self.len as usize) }
  }
}

impl DerefMut for JsBuffer {
  fn deref_mut(&mut self) -> &mut [u8] {
    unsafe { slice::from_raw_parts_mut(self.data as *mut _, self.len as usize) }
  }
}