// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.

use crate::error::type_error;
use crate::error::AnyError;
use crate::gotham_state::GothamState;
use crate::BufVec;
use crate::ZeroCopyBuf;
use futures::Future;
use indexmap::IndexMap;
use serde_json::Value;
use std::cell::RefCell;
use std::collections::HashMap;
use std::iter::once;
use std::ops::Deref;
use std::ops::DerefMut;
use std::pin::Pin;
use std::rc::Rc;

pub type OpAsyncFuture = Pin<Box<dyn Future<Output = Box<[u8]>>>>;
pub type OpFn = dyn Fn(Rc<RefCell<OpState>>, BufVec) -> Op + 'static;
pub type OpId = usize;

pub enum Op {
  Sync(Box<[u8]>),
  Async(OpAsyncFuture),
  /// AsyncUnref is the variation of Async, which doesn't block the program
  /// exiting.
  AsyncUnref(OpAsyncFuture),
  NotFound,
}

pub struct OpState {
  pub resource_table: crate::ResourceTable,
  pub op_table: OpTable,
  pub get_error_class_fn: crate::runtime::GetErrorClassFn,
  gotham_state: GothamState,
}

impl Default for OpState {
  // TODO(ry) Only deno_core should be able to construct an OpState. But I don't
  // know how to make default private. Maybe rename to
  //   pub(crate) fn new() -> OpState
  fn default() -> OpState {
    OpState {
      resource_table: crate::ResourceTable::default(),
      op_table: OpTable::default(),
      get_error_class_fn: &|_| "Error",
      gotham_state: GothamState::default(),
    }
  }
}

impl Deref for OpState {
  type Target = GothamState;

  fn deref(&self) -> &Self::Target {
    &self.gotham_state
  }
}

impl DerefMut for OpState {
  fn deref_mut(&mut self) -> &mut Self::Target {
    &mut self.gotham_state
  }
}

/// Collection for storing registered ops. The special 'get_op_catalog'
/// op with OpId `0` is automatically added when the OpTable is created.
pub struct OpTable(IndexMap<String, Rc<OpFn>>);

impl OpTable {
  pub fn register_op<F>(&mut self, name: &str, op_fn: F) -> OpId
  where
    F: Fn(Rc<RefCell<OpState>>, BufVec) -> Op + 'static,
  {
    let (op_id, prev) = self.0.insert_full(name.to_owned(), Rc::new(op_fn));
    assert!(prev.is_none());
    op_id
  }

  pub fn route_op(
    op_id: OpId,
    state: Rc<RefCell<OpState>>,
    bufs: BufVec,
  ) -> Op {
    if op_id == 0 {
      let ops: HashMap<String, OpId> =
        state.borrow().op_table.0.keys().cloned().zip(0..).collect();
      let buf = serde_json::to_vec(&ops).map(Into::into).unwrap();
      Op::Sync(buf)
    } else {
      let op_fn = state
        .borrow()
        .op_table
        .0
        .get_index(op_id)
        .map(|(_, op_fn)| op_fn.clone());
      match op_fn {
        Some(f) => (f)(state, bufs),
        None => Op::NotFound,
      }
    }
  }
}

impl Default for OpTable {
  fn default() -> Self {
    fn dummy(_state: Rc<RefCell<OpState>>, _bufs: BufVec) -> Op {
      unreachable!()
    }
    Self(once(("ops".to_owned(), Rc::new(dummy) as _)).collect())
  }
}

#[test]
fn op_table() {
  let state = Rc::new(RefCell::new(OpState::default()));

  let foo_id;
  let bar_id;
  {
    let op_table = &mut state.borrow_mut().op_table;
    foo_id = op_table.register_op("foo", |_, _| Op::Sync(b"oof!"[..].into()));
    assert_eq!(foo_id, 1);
    bar_id = op_table.register_op("bar", |_, _| Op::Sync(b"rab!"[..].into()));
    assert_eq!(bar_id, 2);
  }

  let foo_res = OpTable::route_op(foo_id, state.clone(), Default::default());
  assert!(matches!(foo_res, Op::Sync(buf) if &*buf == b"oof!"));
  let bar_res = OpTable::route_op(bar_id, state.clone(), Default::default());
  assert!(matches!(bar_res, Op::Sync(buf) if &*buf == b"rab!"));

  let catalog_res = OpTable::route_op(0, state, Default::default());
  let mut catalog_entries = match catalog_res {
    Op::Sync(buf) => serde_json::from_slice::<HashMap<String, OpId>>(&buf)
      .map(|map| map.into_iter().collect::<Vec<_>>())
      .unwrap(),
    _ => panic!("unexpected `Op` variant"),
  };
  catalog_entries.sort_by(|(_, id1), (_, id2)| id1.partial_cmp(id2).unwrap());
  assert_eq!(
    catalog_entries,
    vec![
      ("ops".to_owned(), 0),
      ("foo".to_owned(), 1),
      ("bar".to_owned(), 2)
    ]
  )
}

pub fn json_op_sync<F>(op_fn: F) -> Box<OpFn>
where
  F: Fn(&mut OpState, Value, &mut [ZeroCopyBuf]) -> Result<Value, AnyError>
    + 'static,
{
  Box::new(move |state: Rc<RefCell<OpState>>, mut bufs: BufVec| -> Op {
    let result = serde_json::from_slice(&bufs[0])
      .map_err(AnyError::from)
      .and_then(|args| op_fn(&mut state.borrow_mut(), args, &mut bufs[1..]));
    let buf =
      json_serialize_op_result(None, result, state.borrow().get_error_class_fn);
    Op::Sync(buf)
  })
}

pub fn json_op_async<F, R>(op_fn: F) -> Box<OpFn>
where
  F: Fn(Rc<RefCell<OpState>>, Value, BufVec) -> R + 'static,
  R: Future<Output = Result<Value, AnyError>> + 'static,
{
  let try_dispatch_op =
    move |state: Rc<RefCell<OpState>>, bufs: BufVec| -> Result<Op, AnyError> {
      let args: Value = serde_json::from_slice(&bufs[0])?;
      let promise_id = args
        .get("promiseId")
        .and_then(Value::as_u64)
        .ok_or_else(|| type_error("missing or invalid `promiseId`"))?;
      let bufs = bufs[1..].into();
      use crate::futures::FutureExt;
      let fut = op_fn(state.clone(), args, bufs).map(move |result| {
        json_serialize_op_result(
          Some(promise_id),
          result,
          state.borrow().get_error_class_fn,
        )
      });
      Ok(Op::Async(Box::pin(fut)))
    };

  Box::new(move |state: Rc<RefCell<OpState>>, bufs: BufVec| -> Op {
    match try_dispatch_op(state.clone(), bufs) {
      Ok(op) => op,
      Err(err) => Op::Sync(json_serialize_op_result(
        None,
        Err(err),
        state.borrow().get_error_class_fn,
      )),
    }
  })
}

fn json_serialize_op_result(
  promise_id: Option<u64>,
  result: Result<serde_json::Value, AnyError>,
  get_error_class_fn: crate::runtime::GetErrorClassFn,
) -> Box<[u8]> {
  let value = match result {
    Ok(v) => serde_json::json!({ "ok": v, "promiseId": promise_id }),
    Err(err) => serde_json::json!({
      "promiseId": promise_id ,
      "err": {
        "className": (get_error_class_fn)(&err),
        "message": err.to_string(),
      }
    }),
  };
  serde_json::to_vec(&value).unwrap().into_boxed_slice()
}