use std::sync::Arc;
use std::collections::HashSet;

use crate::language::{ProgrammingLanguageInterface,
ComputationRequest, LangMetaResponse, LangMetaRequest};

mod command_tree;
use self::command_tree::CommandTree;
mod repl_options;
use repl_options::ReplOptions;
mod directive_actions;
mod directives;
use directives::directives_from_pass_names;
mod help;
mod response;
use response::ReplResponse;

const HISTORY_SAVE_FILE: &'static str = ".schala_history";
const OPTIONS_SAVE_FILE: &'static str = ".schala_repl";

type InterpreterDirectiveOutput = Option<String>;

pub struct Repl {
  pub interpreter_directive_sigil: char,
  line_reader: ::linefeed::interface::Interface<::linefeed::terminal::DefaultTerminal>,
  language_states: Vec<Box<dyn ProgrammingLanguageInterface>>,
  options: ReplOptions,
}

#[derive(Clone)]
enum PromptStyle {
  Normal,
  Multiline
}

impl Repl {
  pub fn new(initial_states: Vec<Box<dyn ProgrammingLanguageInterface>>) -> Repl {
    use linefeed::Interface;
    let line_reader = Interface::new("schala-repl").unwrap();
    let interpreter_directive_sigil = ':';

    Repl {
      interpreter_directive_sigil,
      line_reader,
      language_states: initial_states,
      options: ReplOptions::new(),
    }
  }

  pub fn run_repl(&mut self) {
    println!("Schala MetaInterpreter version {}", crate::VERSION_STRING);
    println!("Type {}help for help with the REPL", self.interpreter_directive_sigil);
    self.load_options();
    self.handle_repl_loop();
    self.save_before_exit();
    println!("Exiting...");
  }

  fn load_options(&mut self) {
    self.line_reader.load_history(HISTORY_SAVE_FILE).unwrap_or(());
    match ReplOptions::load_from_file(OPTIONS_SAVE_FILE) {
      Ok(options) => {
        self.options = options;
      },
      Err(()) => ()
    };
  }

  fn handle_repl_loop(&mut self) {
    use linefeed::ReadResult::*;
    let sigil = self.interpreter_directive_sigil;

    'main: loop {
      macro_rules! match_or_break {
        ($line:expr) => {
          match $line {
            Err(e) => {
              println!("readline IO Error: {}", e);
              break 'main;
            },
            Ok(Eof) | Ok(Signal(_)) => break 'main,
            Ok(Input(ref input)) => input,
          }
        }
      }
      self.update_line_reader();
      let line = self.line_reader.read_line();
      let input: &str = match_or_break!(line);

      self.line_reader.add_history_unique(input.to_string());
      let mut chars = input.chars().peekable();
      let repl_responses = match chars.nth(0) {
        Some(ch) if ch == sigil => {
          if chars.peek() == Some(&'{') {
            let mut buf = String::new();
            buf.push_str(input.get(2..).unwrap());
            'multiline: loop {
              self.set_prompt(PromptStyle::Multiline);
              let new_line = self.line_reader.read_line();
              let new_input = match_or_break!(new_line);
              if new_input.starts_with(":}") {
                break 'multiline;
              } else {
                buf.push_str(new_input);
                buf.push_str("\n");
              }
            }
            self.handle_input(&buf)
          } else {
            match self.handle_interpreter_directive(input) {
              Some(directive_output) => println!("<> {}", directive_output),
              None => (),
            }
            continue
          }
        },
        _ => self.handle_input(input)
      };

      for repl_response in repl_responses.iter() {
        println!("{}", repl_response);
      }
    }
  }

  fn update_line_reader(&mut self) {
    let tab_complete_handler = TabCompleteHandler::new(self.interpreter_directive_sigil, self.get_directives());
    self.line_reader.set_completer(Arc::new(tab_complete_handler)); //TODO fix this here
    self.set_prompt(PromptStyle::Normal);
  }

  fn set_prompt(&mut self, prompt_style: PromptStyle) {
    let prompt_str = match prompt_style {
      PromptStyle::Normal => ">> ".to_string(),
      PromptStyle::Multiline => ">| ".to_string(),
    };

    self.line_reader.set_prompt(&prompt_str).unwrap();
  }

  fn save_before_exit(&self) {
    self.line_reader.save_history(HISTORY_SAVE_FILE).unwrap_or(());
    self.options.save_to_file(OPTIONS_SAVE_FILE);
  }

  fn handle_interpreter_directive(&mut self, input: &str) -> InterpreterDirectiveOutput {
    let mut iter = input.chars();
    iter.next();
    let arguments: Vec<&str> = iter
      .as_str()
      .split_whitespace()
      .collect();

    if arguments.len() < 1 {
      return None;
    }

    let directives = self.get_directives();
    directives.perform(self, &arguments)
  }

  fn get_cur_language_state(&mut self) -> &mut Box<dyn ProgrammingLanguageInterface> {
    //TODO this is obviously not complete
    &mut self.language_states[0]
  }

  fn handle_input(&mut self, input: &str) -> Vec<ReplResponse> {
    let mut debug_requests = HashSet::new();
    for ask in self.options.debug_asks.iter() {
      debug_requests.insert(ask.clone());
    }

    let request = ComputationRequest { source: input, debug_requests };
    let ref mut language_state = self.get_cur_language_state();
    let response = language_state.run_computation(request);
    response::handle_computation_response(response, &self.options)
  }

  fn get_directives(&mut self) -> CommandTree {
    let language_state = self.get_cur_language_state();
    let pass_names = match language_state.request_meta(LangMetaRequest::StageNames) {
      LangMetaResponse::StageNames(names) => names,
      _ => vec![],
    };

    directives_from_pass_names(&pass_names)
  }
}


struct TabCompleteHandler {
  sigil: char,
  top_level_commands: CommandTree,
}

use linefeed::complete::{Completion, Completer};
use linefeed::terminal::Terminal;

impl TabCompleteHandler {
  fn new(sigil: char, top_level_commands: CommandTree) -> TabCompleteHandler {
    TabCompleteHandler {
      top_level_commands,
      sigil,
    }
  }
}

impl<T: Terminal> Completer<T> for TabCompleteHandler {
  fn complete(&self, word: &str, prompter: &::linefeed::prompter::Prompter<T>, start: usize, _end: usize) -> Option<Vec<Completion>> {
    let line = prompter.buffer();

    if !line.starts_with(self.sigil) {
      return None;
    }

    let mut words = line[1..(if start == 0 { 1 } else { start })].split_whitespace();
    let mut completions = Vec::new();
    let mut command_tree: Option<&CommandTree> = Some(&self.top_level_commands);

    loop {
      match words.next() {
        None => {
          let top = match command_tree {
            Some(CommandTree::Top(_)) => true,
            _ => false
          };
          let word = if top { word.get(1..).unwrap() } else { word };
          for cmd in command_tree.map(|x| x.get_subcommands()).unwrap_or(vec![]).into_iter() {
            if cmd.starts_with(word) {
              completions.push(Completion {
                completion: format!("{}{}", if top { ":" } else { "" }, cmd),
                display: Some(cmd.to_string()),
                suffix: ::linefeed::complete::Suffix::Some(' ')
              })
            }
          }
          break;
        },
        Some(s) => {
          let new_ptr: Option<&CommandTree> = command_tree.and_then(|cm| match cm {
            CommandTree::Top(children) => children.iter().find(|c| c.get_cmd() == s),
            CommandTree::NonTerminal { children, .. } => children.iter().find(|c| c.get_cmd() == s),
            CommandTree::Terminal { children, .. } => children.iter().find(|c| c.get_cmd() == s),
          });
          command_tree = new_ptr;
        }
      }
    }
    Some(completions)
  }
}