// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.

use crate::error::bad_resource_id;
use crate::error::type_error;
use crate::error::AnyError;
use crate::gotham_state::GothamState;
use crate::resources::ResourceId;
use crate::resources::ResourceTable;
use crate::runtime::GetErrorClassFn;
use crate::ZeroCopyBuf;
use futures::Future;
use indexmap::IndexMap;
use rusty_v8 as v8;
use serde::de::DeserializeOwned;
use serde::Serialize;
use std::cell::RefCell;
use std::iter::once;
use std::ops::Deref;
use std::ops::DerefMut;
use std::pin::Pin;
use std::rc::Rc;

pub type PromiseId = u64;
pub type OpAsyncFuture = Pin<Box<dyn Future<Output = (PromiseId, OpResponse)>>>;
pub type OpFn =
  dyn Fn(Rc<RefCell<OpState>>, OpPayload, Option<ZeroCopyBuf>) -> Op + 'static;
pub type OpId = usize;

pub struct OpPayload<'a, 'b, 'c> {
  pub(crate) scope: Option<&'a mut v8::HandleScope<'b>>,
  pub(crate) value: Option<v8::Local<'c, v8::Value>>,
  pub(crate) promise_id: PromiseId,
}

impl<'a, 'b, 'c> OpPayload<'a, 'b, 'c> {
  pub fn new(
    scope: &'a mut v8::HandleScope<'b>,
    value: v8::Local<'c, v8::Value>,
    promise_id: PromiseId,
  ) -> Self {
    Self {
      scope: Some(scope),
      value: Some(value),
      promise_id,
    }
  }

  pub fn empty() -> Self {
    Self {
      scope: None,
      value: None,
      promise_id: 0,
    }
  }

  pub fn deserialize<T: DeserializeOwned>(self) -> Result<T, AnyError> {
    serde_v8::from_v8(self.scope.unwrap(), self.value.unwrap())
      .map_err(AnyError::from)
      .map_err(|e| type_error(format!("Error parsing args: {}", e)))
  }
}

pub enum OpResponse {
  Value(OpResult),
  Buffer(Box<[u8]>),
}

pub enum Op {
  Sync(OpResponse),
  Async(OpAsyncFuture),
  /// AsyncUnref is the variation of Async, which doesn't block the program
  /// exiting.
  AsyncUnref(OpAsyncFuture),
  NotFound,
}

pub enum OpResult {
  Ok(serde_v8::SerializablePkg),
  Err(OpError),
}

impl OpResult {
  pub fn to_v8<'a>(
    &self,
    scope: &mut v8::HandleScope<'a>,
  ) -> Result<v8::Local<'a, v8::Value>, serde_v8::Error> {
    match self {
      Self::Ok(x) => x.to_v8(scope),
      Self::Err(err) => serde_v8::to_v8(scope, err),
    }
  }
}

#[derive(Serialize)]
#[serde(rename_all = "camelCase")]
pub struct OpError {
  #[serde(rename = "$err_class_name")]
  class_name: &'static str,
  message: String,
}

pub fn serialize_op_result<R: Serialize + 'static>(
  result: Result<R, AnyError>,
  state: Rc<RefCell<OpState>>,
) -> OpResponse {
  OpResponse::Value(match result {
    Ok(v) => OpResult::Ok(v.into()),
    Err(err) => OpResult::Err(OpError {
      class_name: (state.borrow().get_error_class_fn)(&err),
      message: err.to_string(),
    }),
  })
}

/// Maintains the resources and ops inside a JS runtime.
pub struct OpState {
  pub resource_table: ResourceTable,
  pub op_table: OpTable,
  pub get_error_class_fn: GetErrorClassFn,
  gotham_state: GothamState,
}

impl OpState {
  pub(crate) fn new() -> OpState {
    OpState {
      resource_table: Default::default(),
      op_table: OpTable::default(),
      get_error_class_fn: &|_| "Error",
      gotham_state: Default::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>>, OpPayload, Option<ZeroCopyBuf>) -> 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 op_entries(state: Rc<RefCell<OpState>>) -> Vec<(String, OpId)> {
    state.borrow().op_table.0.keys().cloned().zip(0..).collect()
  }

  pub fn route_op(
    op_id: OpId,
    state: Rc<RefCell<OpState>>,
    payload: OpPayload,
    buf: Option<ZeroCopyBuf>,
  ) -> Op {
    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, payload, buf),
      None => Op::NotFound,
    }
  }
}

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

/// Return map of resources with id as key
/// and string representation as value.
///
/// This op must be wrapped in `op_sync`.
pub fn op_resources(
  state: &mut OpState,
  _args: (),
  _zero_copy: Option<ZeroCopyBuf>,
) -> Result<Vec<(ResourceId, String)>, AnyError> {
  let serialized_resources = state
    .resource_table
    .names()
    .map(|(rid, name)| (rid, name.to_string()))
    .collect();
  Ok(serialized_resources)
}

/// Remove a resource from the resource table.
///
/// This op must be wrapped in `op_sync`.
pub fn op_close(
  state: &mut OpState,
  rid: Option<ResourceId>,
  _zero_copy: Option<ZeroCopyBuf>,
) -> Result<(), AnyError> {
  // TODO(@AaronO): drop Option after improving type-strictness balance in serde_v8
  let rid = rid.ok_or_else(|| type_error("missing or invalid `rid`"))?;
  state
    .resource_table
    .close(rid)
    .ok_or_else(bad_resource_id)?;

  Ok(())
}

#[cfg(test)]
mod tests {
  use super::*;

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

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

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

    let mut catalog_entries = OpTable::op_entries(state);
    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)
      ]
    );
  }
}