/* relish: versatile lisp shell
 * Copyright (C) 2021 Aidan Hahn
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

use {
    relish::{
        ast::{
            eval, lex, run,
            Ctr, Seg, SymTable, Symbol,
        },
        stdlib::{
            static_stdlib, dynamic_stdlib, load_defaults,
            load_environment,
            CONSOLE_XDIM_VNAME, CONSOLE_YDIM_VNAME, CFG_FILE_VNAME,
            L_PROMPT_VNAME, R_PROMPT_VNAME, PROMPT_DELIM_VNAME,
        },
        aux::{ShellState, check_jobs},
    },
    std::{
        cell::RefCell,
        rc::Rc,
        borrow::Cow,
        env,
        env::current_dir,
        path::{PathBuf, Path},
    },
    reedline::{
        FileBackedHistory, DefaultHinter, DefaultValidator,
        Reedline, Signal, Prompt, PromptEditMode, PromptHistorySearch,
        PromptHistorySearchStatus, Completer, Suggestion, Span,
        KeyModifiers, KeyCode, ReedlineEvent, Keybindings,
        ColumnarMenu, Emacs, ReedlineMenu,
        default_emacs_keybindings,
    },
    nix::unistd,
    nu_ansi_term::{Color, Style},
    dirs::home_dir,
    termion::terminal_size,
};

#[derive(Clone)]
pub struct CustomPrompt(String, String, String);
#[derive(Clone)]
pub struct CustomCompleter(Vec<String>);

impl Prompt for CustomPrompt {
    fn render_prompt_left(&self) -> Cow<str> {
        {
            Cow::Owned(self.0.to_owned())
        }
    }

    fn render_prompt_right(&self) -> Cow<str> {
        {
            Cow::Owned(self.1.to_owned())
        }
    }

    fn render_prompt_indicator(&self, _edit_mode: PromptEditMode) -> Cow<str> {
        Cow::Owned(self.2.to_owned())
    }

    fn render_prompt_multiline_indicator(&self) -> Cow<str> {
        Cow::Borrowed("++++")
    }

    fn render_prompt_history_search_indicator(
        &self,
        history_search: PromptHistorySearch,
    ) -> Cow<str> {
        let prefix = match history_search.status {
            PromptHistorySearchStatus::Passing => "",
            PromptHistorySearchStatus::Failing => "failing ",
        };

        Cow::Owned(format!(
            "({}reverse-search: {}) ",
            prefix, history_search.term
        ))
    }
}

impl Completer for CustomCompleter {
    fn complete(&mut self, line: &str, pos: usize) -> Vec<Suggestion> {
        let current_dir_path = current_dir()
            .expect("current dir bad?");
        let (tok, is_str, start) = get_token_to_complete(line, pos);
        let mut sugg = vec![];
        if !is_str {
            let mut offcenter_match = vec![];
            for sym in &self.0 {
                if sym.starts_with(tok.as_str()) {
                    sugg.push(Suggestion {
                        value: sym.clone(),
                        description: None,
                        extra: None,
                        append_whitespace: false,
                        span: Span {
                            start,
                            end: pos
                        }
                    });
                }

                if sym.contains(tok.as_str()) {
                    offcenter_match.push(sym.clone());
                }
            }

            for i in offcenter_match {
                sugg.push(Suggestion {
                    value: i.clone(),
                    description: None,
                    extra: None,
                    append_whitespace: false,
                    span: Span {
                        start,
                        end: pos
                    }
                });
            }
        } else {
            let mut path: PathBuf = Path::new(&tok).to_path_buf();
            if path.is_relative() {
                path = current_dir_path.join(path);
            }

            if let Ok(npath) = path.canonicalize() {
                path = npath;
            }

            if path.exists() && path.is_dir() {
                if let Ok(entries) = path.read_dir() {
                    for entry in entries {
                        if let Ok(e) = entry {
                            sugg.push(Suggestion {
                                value: e.path()
                                    .as_os_str()
                                    .to_str()
                                    .expect("bad dir somehow?")
                                    .to_owned() + "/",
                                description: None,
                                extra: None,
                                span: Span {
                                    start,
                                    end: pos
                                },
                                append_whitespace: false
                            });
                        }
                    }
                }
            } else {
                // check parent to autocomplete path
                if let Some(parent) = path.parent() {
                    if let Ok(entries) = parent.read_dir() {
                        for entry in entries {
                            if let Ok(e) = entry {
                                if e.file_name()
                                    .to_string_lossy()
                                    .starts_with(path.file_name()
                                                 .expect("bad file somehow?")
                                                 .to_string_lossy()
                                                 .to_mut()
                                                 .as_str()
                                    ) {
                                        sugg.push(Suggestion {
                                            value: e.path()
                                                .as_os_str()
                                                .to_str()
                                                .expect("bad dir somehow?")
                                                .to_owned(),
                                            description: None,
                                            extra: None,
                                            append_whitespace: false,
                                            span: Span {
                                                start,
                                                end: pos
                                            }
                                        });
                                    }
                            }
                        }
                    }
                }
            }
        }
        sugg
    }
}

fn add_menu_keybindings(keybindings: &mut Keybindings) {
    keybindings.add_binding(
        KeyModifiers::NONE,
        KeyCode::Tab,
        ReedlineEvent::UntilFound(vec![
            ReedlineEvent::Menu("completion_menu".to_string()),
            ReedlineEvent::MenuNext,
        ]),
    );
}

fn main() {
    const HIST_FILE: &str = "/.relish_hist";
    const CONFIG_FILE_DEFAULT: &str = "/.relishrc";

    // default config file dirs
    let home_dir = home_dir().unwrap().to_str().unwrap().to_owned();
    let hist_file_name = home_dir.clone() + HIST_FILE;
    let cfg_file_name = home_dir + CONFIG_FILE_DEFAULT;

    // TODO: the next two decls should probably be conditional on CFG_RELISH_POSIX
    // but in both cases the data must live for the whole program
    let shell_state_bindings = Rc::new(RefCell::from(ShellState {
        parent_pid: unistd::Pid::from_raw(0),
        parent_sid: unistd::Pid::from_raw(0),
        children: vec![],
        last_exit_code: 0,
        attr: None,
    }));
    let prompt_ss = shell_state_bindings.clone();

    // setup symtable
    let mut syms = SymTable::new();
    load_defaults(&mut syms);
    load_environment(&mut syms);
    static_stdlib(&mut syms).unwrap_or_else(|err: String| eprintln!("{}", err));
    // reload this later with the state bindings
    dynamic_stdlib(&mut syms, None).unwrap_or_else(|err: String| eprintln!("{}", err));

    // if there are args those are scripts, run them and exit
    if env::args().count() > 1 {
        let mut iter = env::args();
        iter.next();
        for i in iter {
            run(i, &mut syms).unwrap();
        }

        return
    }

    // this is a user shell. attempt to load configuration
    {
        // scope the below borrow of syms
        let cfg_file = env::var(CFG_FILE_VNAME).unwrap_or(cfg_file_name);
        run(cfg_file.clone(), &mut syms)
            .unwrap_or_else(|err: String| eprintln!("failed to load script {}\n{}", cfg_file, err));
    }
    dynamic_stdlib(&mut syms, Some(shell_state_bindings)).unwrap_or_else(|err: String| eprintln!("{}", err));

    // setup readline

    let completion_menu = Box::new(ColumnarMenu::default().with_name("completion_menu"));
    let mut keybindings = default_emacs_keybindings();
    add_menu_keybindings(&mut keybindings);
    let edit_mode = Box::new(Emacs::new(keybindings));
    let mut rl = Reedline::create()
        .with_menu(ReedlineMenu::EngineCompleter(completion_menu))
        .with_edit_mode(edit_mode)
        .with_quick_completions(true)
        .with_partial_completions(true)
        .with_ansi_colors(true);

    let maybe_hist: Box<FileBackedHistory>;
    if !hist_file_name.is_empty() {
        maybe_hist = Box::new(
            FileBackedHistory::with_file(5000, hist_file_name.into())
                .expect("error reading history!")
        );
        rl = rl.with_history(maybe_hist);
    }
    rl = rl.with_hinter(Box::new(
        DefaultHinter::default()
            .with_style(Style::new().italic().fg(Color::LightGray)),
    )).with_validator(Box::new(DefaultValidator));

    let mut xdimension: u16 = 0;
    let mut ydimension: u16 = 0;
    loop {
        {
            // update state
            check_jobs(&mut prompt_ss.borrow_mut());
        }
        let readline_prompt = make_prompt(&mut syms);
        let completer = make_completer(&mut syms);
        // realloc with each loop because syms can change
        rl = rl.with_completer(Box::new(completer));
        let user_doc = rl.read_line(&readline_prompt).unwrap();

        // doing this update here prevents needing to update twice before dimensions take effect
        (xdimension, ydimension) =
            check_and_update_console_dimensions(&mut syms, xdimension, ydimension);

        match user_doc {
            Signal::Success(line) => {
                println!(""); // add a new line before output gets printed
                let l = line.as_str().to_owned();
                match lex(&l) {
                    Ok(a) => match eval(&a, &mut syms) {
                        Ok(a) => println!("{}", a),
                        Err(s) => println!("{}", s),
                    },
                    Err(s) => println!("{}", s),
                }
            },

            Signal::CtrlD  => {
                println!("EOF!");
                return
            },

            Signal::CtrlC => {
                println!("Interrupted!");
            },
        }
    }
}

fn make_prompt(syms: &mut SymTable) -> CustomPrompt {
    let l_ctr = *syms
        .call_symbol(&L_PROMPT_VNAME.to_string(), &Seg::new(), true)
        .unwrap_or_else(|err: String| {
            eprintln!("{}", err);
            Box::new(Ctr::String("<prompt broken!>".to_string()))
        });
    let r_ctr = *syms
        .call_symbol(&R_PROMPT_VNAME.to_string(), &Seg::new(), true)
        .unwrap_or_else(|err: String| {
            eprintln!("{}", err);
            Box::new(Ctr::String("<prompt broken!>".to_string()))
        });
    let d_ctr = *syms
        .call_symbol(&PROMPT_DELIM_VNAME.to_string(), &Seg::new(), true)
        .unwrap_or_else(|err: String| {
            eprintln!("{}", err);
            Box::new(Ctr::String("<prompt broken!>".to_string()))
        });

    let l_str: String;
    let r_str: String;
    let d_str: String;
    if let Ctr::String(s) = l_ctr {
        l_str = s;
    } else {
        l_str = l_ctr.to_string();
    }
    if let Ctr::String(s) = r_ctr {
        r_str = s;
    } else {
        r_str = r_ctr.to_string();
    }
    if let Ctr::String(s) = d_ctr {
        d_str = s;
    } else {
        d_str = d_ctr.to_string();
    }

    CustomPrompt(l_str, r_str, d_str)
}

fn make_completer(syms: &mut SymTable) -> CustomCompleter {
    let mut toks = vec![];
    for i in syms.keys(){
        toks.push(i.clone());
    }
    CustomCompleter(toks)
}

fn get_token_to_complete(line: &str, pos: usize) -> (String, bool, usize) {
    let mut res = String::with_capacity(1);
    let mut doc = line.chars().rev();
    for _ in pos..line.len() {
        doc.next();
    }
    let mut is_str = false;
    let mut start_idx = pos;
    for idx in (0..pos).rev() {
        let iter = doc.next()
            .expect(format!("AC: no idx {}", idx)
                    .as_str());
        match iter {
            ' ' | '(' | '\n' => {
                break
            },
            '\'' | '"' => {
                is_str = true;
                break
            },
            _ => {
                start_idx = idx;
                res.insert(0, iter);
            }
        }
    }

    return (res, is_str, start_idx)
}

/* It was considered that a SIGWINCH handler would be a more
 * elegant solution to this. Such a solution would need to
 * modify the current libc based approach to use a state-enclosing
 * closure as a signal handler. As of May 2023 there is no clear
 * way of doing such a thing.
 *
 * Luckily this data is only used within Relish, so we can simply
 * rely on it only being read during the evaluation phase of the REPL.
 * This method will at least work for that. (ava)
 */
fn check_and_update_console_dimensions(
    syms: &mut SymTable,
    last_xdim: u16,
    last_ydim: u16
) -> (u16, u16) {
    let (xdim, ydim) = terminal_size().expect("Couldnt get console dimensions");

    if xdim != last_xdim {
        syms.insert(
            String::from(CONSOLE_XDIM_VNAME),
            Symbol::from_ast(
                &String::from(CONSOLE_XDIM_VNAME),
                &String::from("Length of current console"),
                &Seg::from_mono(Box::new(Ctr::Integer(xdim.into()))),
                None,
            )
        );
    }

    if ydim != last_ydim {
        syms.insert(
            String::from(CONSOLE_YDIM_VNAME),
            Symbol::from_ast(
                &String::from(CONSOLE_YDIM_VNAME),
                &String::from("Height of current console"),
                &Seg::from_mono(Box::new(Ctr::Integer(ydim.into()))),
                None,
            )
        );
    }

    (xdim, ydim)
}