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

use crate::ast;
use crate::ast::TokenOrComment;
use crate::colors;
use crate::media_type::MediaType;
use crate::program_state::ProgramState;
use deno_core::error::AnyError;
use deno_core::futures::FutureExt;
use deno_core::serde_json::json;
use deno_core::serde_json::Value;
use deno_core::LocalInspectorSession;
use deno_runtime::worker::MainWorker;
use rustyline::completion::Completer;
use rustyline::error::ReadlineError;
use rustyline::highlight::Highlighter;
use rustyline::validate::ValidationContext;
use rustyline::validate::ValidationResult;
use rustyline::validate::Validator;
use rustyline::Context;
use rustyline::Editor;
use rustyline_derive::{Helper, Hinter};
use std::borrow::Cow;
use std::path::PathBuf;
use std::sync::mpsc::channel;
use std::sync::mpsc::sync_channel;
use std::sync::mpsc::Receiver;
use std::sync::mpsc::Sender;
use std::sync::mpsc::SyncSender;
use std::sync::Arc;
use std::sync::Mutex;
use swc_ecmascript::parser::token::{Token, Word};
use tokio::pin;

// Provides helpers to the editor like validation for multi-line edits, completion candidates for
// tab completion.
#[derive(Helper, Hinter)]
struct EditorHelper {
  context_id: u64,
  message_tx: SyncSender<(String, Option<Value>)>,
  response_rx: Receiver<Result<Value, AnyError>>,
}

impl EditorHelper {
  fn post_message(
    &self,
    method: &str,
    params: Option<Value>,
  ) -> Result<Value, AnyError> {
    self.message_tx.send((method.to_string(), params))?;
    self.response_rx.recv()?
  }
}

fn is_word_boundary(c: char) -> bool {
  if c == '.' {
    false
  } else {
    char::is_ascii_whitespace(&c) || char::is_ascii_punctuation(&c)
  }
}

impl Completer for EditorHelper {
  type Candidate = String;

  fn complete(
    &self,
    line: &str,
    pos: usize,
    _ctx: &Context<'_>,
  ) -> Result<(usize, Vec<String>), ReadlineError> {
    let start = line[..pos].rfind(is_word_boundary).map_or_else(|| 0, |i| i);
    let end = line[pos..]
      .rfind(is_word_boundary)
      .map_or_else(|| pos, |i| pos + i);

    let word = &line[start..end];
    let word = word.strip_prefix(is_word_boundary).unwrap_or(word);
    let word = word.strip_suffix(is_word_boundary).unwrap_or(word);

    let fallback = format!(".{}", word);

    let (prefix, suffix) = match word.rfind('.') {
      Some(index) => word.split_at(index),
      None => ("globalThis", fallback.as_str()),
    };

    let evaluate_response = self
      .post_message(
        "Runtime.evaluate",
        Some(json!({
          "contextId": self.context_id,
          "expression": prefix,
          "throwOnSideEffect": true,
          "timeout": 200,
        })),
      )
      .unwrap();

    if evaluate_response.get("exceptionDetails").is_some() {
      let candidates = Vec::new();
      return Ok((pos, candidates));
    }

    if let Some(result) = evaluate_response.get("result") {
      if let Some(object_id) = result.get("objectId") {
        let get_properties_response = self.post_message(
          "Runtime.getProperties",
          Some(json!({
            "objectId": object_id,
          })),
        );

        if let Ok(get_properties_response) = get_properties_response {
          if let Some(result) = get_properties_response.get("result") {
            let candidates = result
              .as_array()
              .unwrap()
              .iter()
              .filter_map(|r| {
                let name = r.get("name").unwrap().as_str().unwrap().to_string();

                if name.starts_with("Symbol(") {
                  return None;
                }

                if name.starts_with(&suffix[1..]) {
                  return Some(name);
                }

                None
              })
              .collect();

            return Ok((pos - (suffix.len() - 1), candidates));
          }
        }
      }
    }

    Ok((pos, Vec::new()))
  }
}

impl Validator for EditorHelper {
  fn validate(
    &self,
    ctx: &mut ValidationContext,
  ) -> Result<ValidationResult, ReadlineError> {
    let mut stack: Vec<Token> = Vec::new();
    let mut in_template = false;

    for item in ast::lex("", ctx.input(), &MediaType::JavaScript) {
      if let TokenOrComment::Token(token) = item.inner {
        match token {
          Token::BackQuote => in_template = !in_template,
          Token::LParen
          | Token::LBracket
          | Token::LBrace
          | Token::DollarLBrace => stack.push(token),
          Token::RParen | Token::RBracket | Token::RBrace => {
            match (stack.pop(), token) {
              (Some(Token::LParen), Token::RParen)
              | (Some(Token::LBracket), Token::RBracket)
              | (Some(Token::LBrace), Token::RBrace)
              | (Some(Token::DollarLBrace), Token::RBrace) => {}
              (Some(left), _) => {
                return Ok(ValidationResult::Invalid(Some(format!(
                  "Mismatched pairs: {:?} is not properly closed",
                  left
                ))))
              }
              (None, _) => {
                // While technically invalid when unpaired, it should be V8's task to output error instead.
                // Thus marked as valid with no info.
                return Ok(ValidationResult::Valid(None));
              }
            }
          }
          _ => {}
        }
      }
    }

    if !stack.is_empty() || in_template {
      return Ok(ValidationResult::Incomplete);
    }

    Ok(ValidationResult::Valid(None))
  }
}

impl Highlighter for EditorHelper {
  fn highlight_hint<'h>(&self, hint: &'h str) -> Cow<'h, str> {
    hint.into()
  }

  fn highlight_candidate<'c>(
    &self,
    candidate: &'c str,
    _completion: rustyline::CompletionType,
  ) -> Cow<'c, str> {
    self.highlight(candidate, 0)
  }

  fn highlight_char(&self, line: &str, _: usize) -> bool {
    !line.is_empty()
  }

  fn highlight<'l>(&self, line: &'l str, _: usize) -> Cow<'l, str> {
    let mut out_line = String::from(line);

    for item in ast::lex("", line, &MediaType::JavaScript) {
      // Adding color adds more bytes to the string,
      // so an offset is needed to stop spans falling out of sync.
      let offset = out_line.len() - line.len();
      let span = item.span_as_range();

      out_line.replace_range(
        span.start + offset..span.end + offset,
        &match item.inner {
          TokenOrComment::Token(token) => match token {
            Token::Str { .. } | Token::Template { .. } | Token::BackQuote => {
              colors::green(&line[span]).to_string()
            }
            Token::Regex(_, _) => colors::red(&line[span]).to_string(),
            Token::Num(_) | Token::BigInt(_) => {
              colors::yellow(&line[span]).to_string()
            }
            Token::Word(word) => match word {
              Word::True | Word::False | Word::Null => {
                colors::yellow(&line[span]).to_string()
              }
              Word::Keyword(_) => colors::cyan(&line[span]).to_string(),
              Word::Ident(ident) => {
                if ident == *"undefined" {
                  colors::gray(&line[span]).to_string()
                } else if ident == *"Infinity" || ident == *"NaN" {
                  colors::yellow(&line[span]).to_string()
                } else if ident == *"async" || ident == *"of" {
                  colors::cyan(&line[span]).to_string()
                } else {
                  line[span].to_string()
                }
              }
            },
            _ => line[span].to_string(),
          },
          TokenOrComment::Comment { .. } => {
            colors::gray(&line[span]).to_string()
          }
        },
      );
    }

    out_line.into()
  }
}

#[derive(Clone)]
struct ReplEditor {
  inner: Arc<Mutex<Editor<EditorHelper>>>,
  history_file_path: PathBuf,
}

impl ReplEditor {
  pub fn new(helper: EditorHelper, history_file_path: PathBuf) -> Self {
    let mut editor = Editor::new();
    editor.set_helper(Some(helper));
    editor.load_history(&history_file_path).unwrap_or(());

    ReplEditor {
      inner: Arc::new(Mutex::new(editor)),
      history_file_path,
    }
  }

  pub fn readline(&self) -> Result<String, ReadlineError> {
    self.inner.lock().unwrap().readline("> ")
  }

  pub fn add_history_entry(&self, entry: String) {
    self.inner.lock().unwrap().add_history_entry(entry);
  }

  pub fn save_history(&self) -> Result<(), AnyError> {
    std::fs::create_dir_all(self.history_file_path.parent().unwrap())?;

    self
      .inner
      .lock()
      .unwrap()
      .save_history(&self.history_file_path)?;
    Ok(())
  }
}

static PRELUDE: &str = r#"
Object.defineProperty(globalThis, "_", {
  configurable: true,
  get: () => Deno[Deno.internal].lastEvalResult,
  set: (value) => {
   Object.defineProperty(globalThis, "_", {
     value: value,
     writable: true,
     enumerable: true,
     configurable: true,
   });
   console.log("Last evaluation result is no longer saved to _.");
  },
});

Object.defineProperty(globalThis, "_error", {
  configurable: true,
  get: () => Deno[Deno.internal].lastThrownError,
  set: (value) => {
   Object.defineProperty(globalThis, "_error", {
     value: value,
     writable: true,
     enumerable: true,
     configurable: true,
   });

   console.log("Last thrown error is no longer saved to _error.");
  },
});
"#;

struct ReplSession {
  worker: MainWorker,
  session: LocalInspectorSession,
  pub context_id: u64,
}

impl ReplSession {
  pub async fn initialize(mut worker: MainWorker) -> Result<Self, AnyError> {
    let mut session = worker.create_inspector_session().await;

    worker
      .with_event_loop(
        session.post_message("Runtime.enable", None).boxed_local(),
      )
      .await?;

    // Enabling the runtime domain will always send trigger one executionContextCreated for each
    // context the inspector knows about so we grab the execution context from that since
    // our inspector does not support a default context (0 is an invalid context id).
    let mut context_id: u64 = 0;
    for notification in session.notifications() {
      let method = notification.get("method").unwrap().as_str().unwrap();
      let params = notification.get("params").unwrap();

      if method == "Runtime.executionContextCreated" {
        context_id = params
          .get("context")
          .unwrap()
          .get("id")
          .unwrap()
          .as_u64()
          .unwrap();
      }
    }

    let mut repl_session = ReplSession {
      worker,
      session,
      context_id,
    };

    // inject prelude
    repl_session.evaluate_expression(PRELUDE).await?;

    Ok(repl_session)
  }

  pub async fn is_closing(&mut self) -> Result<bool, AnyError> {
    let closed = self
      .evaluate_expression("(globalThis.closed)")
      .await?
      .get("result")
      .unwrap()
      .get("value")
      .unwrap()
      .as_bool()
      .unwrap();

    Ok(closed)
  }

  pub async fn post_message_with_event_loop(
    &mut self,
    method: &str,
    params: Option<Value>,
  ) -> Result<Value, AnyError> {
    self
      .worker
      .with_event_loop(self.session.post_message(method, params).boxed_local())
      .await
  }

  pub async fn run_event_loop(&mut self) -> Result<(), AnyError> {
    self.worker.run_event_loop(false).await
  }

  pub async fn evaluate_line(&mut self, line: &str) -> Result<Value, AnyError> {
    // It is a bit unexpected that { "foo": "bar" } is interpreted as a block
    // statement rather than an object literal so we interpret it as an expression statement
    // to match the behavior found in a typical prompt including browser developer tools.
    let wrapped_line = if line.trim_start().starts_with('{')
      && !line.trim_end().ends_with(';')
    {
      format!("({})", &line)
    } else {
      line.to_string()
    };

    let evaluate_response = self
      .evaluate_expression(&format!("'use strict'; void 0;\n{}", &wrapped_line))
      .await?;

    // If that fails, we retry it without wrapping in parens letting the error bubble up to the
    // user if it is still an error.
    let evaluate_response =
      if evaluate_response.get("exceptionDetails").is_some()
        && wrapped_line != line
      {
        self
          .evaluate_expression(&format!("'use strict'; void 0;\n{}", &line))
          .await?
      } else {
        evaluate_response
      };

    Ok(evaluate_response)
  }

  pub async fn set_last_thrown_error(
    &mut self,
    error: &Value,
  ) -> Result<(), AnyError> {
    self.post_message_with_event_loop(
      "Runtime.callFunctionOn",
      Some(json!({
        "executionContextId": self.context_id,
        "functionDeclaration": "function (object) { Deno[Deno.internal].lastThrownError = object; }",
        "arguments": [
          error,
        ],
      })),
    ).await?;
    Ok(())
  }

  pub async fn set_last_eval_result(
    &mut self,
    evaluate_result: &Value,
  ) -> Result<(), AnyError> {
    self.post_message_with_event_loop(
      "Runtime.callFunctionOn",
      Some(json!({
        "executionContextId": self.context_id,
        "functionDeclaration": "function (object) { Deno[Deno.internal].lastEvalResult = object; }",
        "arguments": [
          evaluate_result,
        ],
      })),
    ).await?;
    Ok(())
  }

  pub async fn get_eval_value(
    &mut self,
    evaluate_result: &Value,
  ) -> Result<String, AnyError> {
    // TODO(caspervonb) we should investigate using previews here but to keep things
    // consistent with the previous implementation we just get the preview result from
    // Deno.inspectArgs.
    let inspect_response = self.post_message_with_event_loop(
      "Runtime.callFunctionOn",
      Some(json!({
        "executionContextId": self.context_id,
        "functionDeclaration": "function (object) { return Deno[Deno.internal].inspectArgs(['%o', object], { colors: !Deno.noColor }); }",
        "arguments": [
          evaluate_result,
        ],
      })),
    ).await?;

    let inspect_result = inspect_response.get("result").unwrap();
    let value = inspect_result.get("value").unwrap().as_str().unwrap();

    Ok(value.to_string())
  }

  async fn evaluate_expression(
    &mut self,
    expression: &str,
  ) -> Result<Value, AnyError> {
    self
      .post_message_with_event_loop(
        "Runtime.evaluate",
        Some(json!({
          "expression": expression,
          "contextId": self.context_id,
          "replMode": true,
        })),
      )
      .await
  }
}

async fn read_line_and_poll(
  repl_session: &mut ReplSession,
  message_rx: &Receiver<(String, Option<Value>)>,
  response_tx: &Sender<Result<Value, AnyError>>,
  editor: ReplEditor,
) -> Result<String, ReadlineError> {
  let mut line = tokio::task::spawn_blocking(move || editor.readline());

  let mut poll_worker = true;

  loop {
    for (method, params) in message_rx.try_iter() {
      let result = repl_session
        .post_message_with_event_loop(&method, params)
        .await;
      response_tx.send(result).unwrap();
    }

    // Because an inspector websocket client may choose to connect at anytime when we have an
    // inspector server we need to keep polling the worker to pick up new connections.
    // TODO(piscisaureus): the above comment is a red herring; figure out if/why
    // the event loop isn't woken by a waker when a websocket client connects.
    let timeout = tokio::time::sleep(tokio::time::Duration::from_millis(100));
    pin!(timeout);

    tokio::select! {
      result = &mut line => {
        return result.unwrap();
      }
      _ = repl_session.run_event_loop(), if poll_worker => {
        poll_worker = false;
      }
      _ = timeout => {
        poll_worker = true
      }
    }
  }
}

pub async fn run(
  program_state: &ProgramState,
  worker: MainWorker,
) -> Result<(), AnyError> {
  let mut repl_session = ReplSession::initialize(worker).await?;
  let (message_tx, message_rx) = sync_channel(1);
  let (response_tx, response_rx) = channel();

  let helper = EditorHelper {
    context_id: repl_session.context_id,
    message_tx,
    response_rx,
  };

  let history_file_path = program_state.dir.root.join("deno_history.txt");
  let editor = ReplEditor::new(helper, history_file_path);

  println!("Deno {}", crate::version::deno());
  println!("exit using ctrl+d or close()");

  loop {
    let line = read_line_and_poll(
      &mut repl_session,
      &message_rx,
      &response_tx,
      editor.clone(),
    )
    .await;
    match line {
      Ok(line) => {
        let evaluate_response = repl_session.evaluate_line(&line).await?;

        // We check for close and break here instead of making it a loop condition to get
        // consistent behavior in when the user evaluates a call to close().
        if repl_session.is_closing().await? {
          break;
        }

        let evaluate_result = evaluate_response.get("result").unwrap();
        let evaluate_exception_details =
          evaluate_response.get("exceptionDetails");

        if evaluate_exception_details.is_some() {
          repl_session.set_last_thrown_error(evaluate_result).await?;
        } else {
          repl_session.set_last_eval_result(evaluate_result).await?;
        }

        let value = repl_session.get_eval_value(evaluate_result).await?;
        let output = match evaluate_exception_details {
          Some(_) => format!("Uncaught {}", value),
          None => value,
        };

        println!("{}", output);

        editor.add_history_entry(line);
      }
      Err(ReadlineError::Interrupted) => {
        println!("exit using ctrl+d or close()");
        continue;
      }
      Err(ReadlineError::Eof) => {
        break;
      }
      Err(err) => {
        println!("Error: {:?}", err);
        break;
      }
    }
  }

  editor.save_history()?;

  Ok(())
}