#![allow(non_snake_case)]

use std::rc::Rc;
//use std::collections::HashMap;
use fnv::FnvHashMap;
use itertools::Itertools;

#[macro_use]
extern crate lazy_static;
extern crate fnv;
extern crate itertools;
extern crate regex;

extern crate rustyline;
use rustyline::error::ReadlineError;
use rustyline::Editor;

#[macro_use]
mod types;
use crate::types::MalErr::{ErrMalVal, ErrString};
use crate::types::MalVal::{Bool, Func, Hash, List, MalFunc, Nil, Str, Sym, Vector};
use crate::types::{error, format_error, MalArgs, MalErr, MalRet, MalVal};
mod env;
mod printer;
mod reader;
use crate::env::{env_bind, env_find, env_get, env_new, env_set, env_sets, Env};
#[macro_use]
mod core;

// read
fn read(str: &str) -> MalRet {
    reader::read_str(str.to_string())
}

// eval
fn quasiquote(ast: &MalVal) -> MalVal {
    match ast {
        List(ref v, _) | Vector(ref v, _) if v.len() > 0 => {
            let a0 = &v[0];
            match a0 {
                Sym(ref s) if s == "unquote" => v[1].clone(),
                _ => match a0 {
                    List(ref v0, _) | Vector(ref v0, _) if v0.len() > 0 => match v0[0] {
                        Sym(ref s) if s == "splice-unquote" => list![
                            Sym("concat".to_string()),
                            v0[1].clone(),
                            quasiquote(&list!(v[1..].to_vec()))
                        ],
                        _ => list![
                            Sym("cons".to_string()),
                            quasiquote(a0),
                            quasiquote(&list!(v[1..].to_vec()))
                        ],
                    },
                    _ => list![
                        Sym("cons".to_string()),
                        quasiquote(a0),
                        quasiquote(&list!(v[1..].to_vec()))
                    ],
                },
            }
        }
        _ => list![Sym("quote".to_string()), ast.clone()],
    }
}

fn is_macro_call(ast: &MalVal, env: &Env) -> Option<(MalVal, MalArgs)> {
    match ast {
        List(v, _) => match v[0] {
            Sym(ref s) => match env_find(env, s) {
                Some(e) => match env_get(&e, &v[0]) {
                    Ok(f @ MalFunc { is_macro: true, .. }) => Some((f, v[1..].to_vec())),
                    _ => None,
                },
                _ => None,
            },
            _ => None,
        },
        _ => None,
    }
}

fn macroexpand(mut ast: MalVal, env: &Env) -> (bool, MalRet) {
    let mut was_expanded = false;
    while let Some((mf, args)) = is_macro_call(&ast, env) {
        //println!("macroexpand 1: {:?}", ast);
        ast = match mf.apply(args) {
            Err(e) => return (false, Err(e)),
            Ok(a) => a,
        };
        //println!("macroexpand 2: {:?}", ast);
        was_expanded = true;
    }
    ((was_expanded, Ok(ast)))
}

fn eval_ast(ast: &MalVal, env: &Env) -> MalRet {
    match ast {
        Sym(_) => Ok(env_get(&env, &ast)?),
        List(v, _) => {
            let mut lst: MalArgs = vec![];
            for a in v.iter() {
                lst.push(eval(a.clone(), env.clone())?)
            }
            Ok(list!(lst))
        }
        Vector(v, _) => {
            let mut lst: MalArgs = vec![];
            for a in v.iter() {
                lst.push(eval(a.clone(), env.clone())?)
            }
            Ok(vector!(lst))
        }
        Hash(hm, _) => {
            let mut new_hm: FnvHashMap<String, MalVal> = FnvHashMap::default();
            for (k, v) in hm.iter() {
                new_hm.insert(k.to_string(), eval(v.clone(), env.clone())?);
            }
            Ok(Hash(Rc::new(new_hm), Rc::new(Nil)))
        }
        _ => Ok(ast.clone()),
    }
}

fn eval(mut ast: MalVal, mut env: Env) -> MalRet {
    let ret: MalRet;

    'tco: loop {
        ret = match ast.clone() {
            List(l, _) => {
                if l.len() == 0 {
                    return Ok(ast);
                }
                match macroexpand(ast.clone(), &env) {
                    (true, Ok(new_ast)) => {
                        ast = new_ast;
                        continue 'tco;
                    }
                    (_, Err(e)) => return Err(e),
                    _ => (),
                }

                if l.len() == 0 {
                    return Ok(ast);
                }
                let a0 = &l[0];
                match a0 {
                    Sym(ref a0sym) if a0sym == "def!" => {
                        env_set(&env, l[1].clone(), eval(l[2].clone(), env.clone())?)
                    }
                    Sym(ref a0sym) if a0sym == "let*" => {
                        env = env_new(Some(env.clone()));
                        let (a1, a2) = (l[1].clone(), l[2].clone());
                        match a1 {
                            List(ref binds, _) | Vector(ref binds, _) => {
                                for (b, e) in binds.iter().tuples() {
                                    match b {
                                        Sym(_) => {
                                            let _ = env_set(
                                                &env,
                                                b.clone(),
                                                eval(e.clone(), env.clone())?,
                                            );
                                        }
                                        _ => {
                                            return error("let* with non-Sym binding");
                                        }
                                    }
                                }
                            }
                            _ => {
                                return error("let* with non-List bindings");
                            }
                        };
                        ast = a2;
                        continue 'tco;
                    }
                    Sym(ref a0sym) if a0sym == "quote" => Ok(l[1].clone()),
                    Sym(ref a0sym) if a0sym == "quasiquote" => {
                        ast = quasiquote(&l[1]);
                        continue 'tco;
                    }
                    Sym(ref a0sym) if a0sym == "defmacro!" => {
                        let (a1, a2) = (l[1].clone(), l[2].clone());
                        let r = eval(a2, env.clone())?;
                        match r {
                            MalFunc {
                                eval,
                                ast,
                                env,
                                params,
                                ..
                            } => Ok(env_set(
                                &env,
                                a1.clone(),
                                MalFunc {
                                    eval: eval,
                                    ast: ast.clone(),
                                    env: env.clone(),
                                    params: params.clone(),
                                    is_macro: true,
                                    meta: Rc::new(Nil),
                                },
                            )?),
                            _ => error("set_macro on non-function"),
                        }
                    }
                    Sym(ref a0sym) if a0sym == "macroexpand" => {
                        match macroexpand(l[1].clone(), &env) {
                            (_, Ok(new_ast)) => Ok(new_ast),
                            (_, e) => return e,
                        }
                    }
                    Sym(ref a0sym) if a0sym == "try*" => match eval(l[1].clone(), env.clone()) {
                        Err(ref e) if l.len() >= 3 => {
                            let exc = match e {
                                ErrMalVal(mv) => mv.clone(),
                                ErrString(s) => Str(s.to_string()),
                            };
                            match l[2].clone() {
                                List(c, _) => {
                                    let catch_env = env_bind(
                                        Some(env.clone()),
                                        list!(vec![c[1].clone()]),
                                        vec![exc],
                                    )?;
                                    eval(c[2].clone(), catch_env)
                                }
                                _ => error("invalid catch block"),
                            }
                        }
                        res => res,
                    },
                    Sym(ref a0sym) if a0sym == "do" => {
                        match eval_ast(&list!(l[1..l.len() - 1].to_vec()), &env)? {
                            List(_, _) => {
                                ast = l.last().unwrap_or(&Nil).clone();
                                continue 'tco;
                            }
                            _ => error("invalid do form"),
                        }
                    }
                    Sym(ref a0sym) if a0sym == "if" => {
                        let cond = eval(l[1].clone(), env.clone())?;
                        match cond {
                            Bool(false) | Nil if l.len() >= 4 => {
                                ast = l[3].clone();
                                continue 'tco;
                            }
                            Bool(false) | Nil => Ok(Nil),
                            _ if l.len() >= 3 => {
                                ast = l[2].clone();
                                continue 'tco;
                            }
                            _ => Ok(Nil),
                        }
                    }
                    Sym(ref a0sym) if a0sym == "fn*" => {
                        let (a1, a2) = (l[1].clone(), l[2].clone());
                        Ok(MalFunc {
                            eval: eval,
                            ast: Rc::new(a2),
                            env: env,
                            params: Rc::new(a1),
                            is_macro: false,
                            meta: Rc::new(Nil),
                        })
                    }
                    Sym(ref a0sym) if a0sym == "eval" => {
                        ast = eval(l[1].clone(), env.clone())?;
                        while let Some(ref e) = env.clone().outer {
                            env = e.clone();
                        }
                        continue 'tco;
                    }
                    _ => match eval_ast(&ast, &env)? {
                        List(ref el, _) => {
                            let ref f = el[0].clone();
                            let args = el[1..].to_vec();
                            match f {
                                Func(_, _) => f.apply(args),
                                MalFunc {
                                    ast: mast,
                                    env: menv,
                                    params,
                                    ..
                                } => {
                                    let a = &**mast;
                                    let p = &**params;
                                    env = env_bind(Some(menv.clone()), p.clone(), args)?;
                                    ast = a.clone();
                                    continue 'tco;
                                }
                                _ => error("attempt to call non-function"),
                            }
                        }
                        _ => error("expected a list"),
                    },
                }
            }
            _ => eval_ast(&ast, &env),
        };

        break;
    } // end 'tco loop

    ret
}

// print
fn print(ast: &MalVal) -> String {
    ast.pr_str(true)
}

fn rep(str: &str, env: &Env) -> Result<String, MalErr> {
    let ast = read(str)?;
    let exp = eval(ast, env.clone())?;
    Ok(print(&exp))
}

fn main() {
    let mut args = std::env::args();
    let arg1 = args.nth(1);

    // `()` can be used when no completer is required
    let mut rl = Editor::<()>::new();
    if rl.load_history(".mal-history").is_err() {
        eprintln!("No previous history.");
    }

    // core.rs: defined using rust
    let repl_env = env_new(None);
    for (k, v) in core::ns() {
        env_sets(&repl_env, k, v);
    }
    env_sets(&repl_env, "*ARGV*", list!(args.map(Str).collect()));

    // core.mal: defined using the language itself
    let _ = rep("(def! *host-language* \"rust\")", &repl_env);
    let _ = rep("(def! not (fn* (a) (if a false true)))", &repl_env);
    let _ = rep(
        "(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \"\nnil)\")))))",
        &repl_env,
    );
    let _ = rep("(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))", &repl_env);

    // Invoked with arguments
    if let Some(f) = arg1 {
        match rep(&format!("(load-file \"{}\")", f), &repl_env) {
            Ok(_) => std::process::exit(0),
            Err(e) => {
                println!("Error: {}", format_error(e));
                std::process::exit(1);
            }
        }
    }

    // main repl loop
    let _ = rep("(println (str \"Mal [\" *host-language* \"]\"))", &repl_env);
    loop {
        let readline = rl.readline("user> ");
        match readline {
            Ok(line) => {
                rl.add_history_entry(&line);
                rl.save_history(".mal-history").unwrap();
                if line.len() > 0 {
                    match rep(&line, &repl_env) {
                        Ok(out) => println!("{}", out),
                        Err(e) => println!("Error: {}", format_error(e)),
                    }
                }
            }
            Err(ReadlineError::Interrupted) => continue,
            Err(ReadlineError::Eof) => break,
            Err(err) => {
                println!("Error: {:?}", err);
                break;
            }
        }
    }
}