use std::{time::{SystemTime, UNIX_EPOCH}, rc::Rc, cell::RefCell};

use complexpr::{value::{Value, func::Func}, RuntimeError, env::Environment};

use crate::declare_fn;

pub fn load(env: &mut Environment) {
    declare_fn!(env, "type", fn_type, 1);
    declare_fn!(env, type_eq, 1);
    declare_fn!(env, copy, 1);
    declare_fn!(env, str, 1);
    declare_fn!(env, repr, 1);
    declare_fn!(env, ord, 1); 
    declare_fn!(env, chr, 1); 
    declare_fn!(env, has, 2); 
    declare_fn!(env, len, 1); 
    declare_fn!(env, args, 0); 
    declare_fn!(env, time, 0); 
    declare_fn!(env, list, 1);
    declare_fn!(env, push, 2);
    declare_fn!(env, pop, 1);
    declare_fn!(env, append, 2);
    declare_fn!(env, insert, 3);
    declare_fn!(env, remove, 2);
    
}

fn fn_type(args: Vec<Value>) -> Result<Value, RuntimeError> {
    Ok(Value::Type(args[0].get_type()))
}

fn fn_type_eq(args: Vec<Value>) -> Result<Value, RuntimeError> {
    Ok(Value::Bool(if args[0].get_type() != args[1].get_type() {
        false
    } else {
        args[0] == args[1]
    }))
}

fn fn_copy(args: Vec<Value>) -> Result<Value, RuntimeError> {
    Ok(match &args[0] {
        Value::List(l) => Value::from(l.borrow().clone()),
        Value::Map(m) => Value::from(m.borrow().clone()),
        // Value::Func(f) => Value::Func(f.make_copy()) // TODO copy functions
        Value::Struct(_) => todo!(),
        a => a.clone(),
    })
}

fn fn_str(args: Vec<Value>) -> Result<Value, RuntimeError> {
    Ok(Value::from(args[0].to_string()))
}

fn fn_repr(args: Vec<Value>) -> Result<Value, RuntimeError> {
    Ok(Value::from(args[0].repr()))
}

fn fn_ord(args: Vec<Value>) -> Result<Value, RuntimeError> {
    if let Value::Char(c) = args[0] {
        Ok(Value::from(c as u32))
    } else {
        Err("Argument to ord must be a char".into())
    }
}

fn fn_chr(args: Vec<Value>) -> Result<Value, RuntimeError> {
    if let Value::Int(i) = args[0] {
        if i >= 0 && i < (u32::MAX as i64) {
            if let Some(c) = char::from_u32(i as u32) {
                return Ok(Value::from(c))
            }
        }
        Err("Out of range".into())
    } else {
        Err("Argument to chr must be an integer".into())
    }
}
fn fn_len(args: Vec<Value>) -> Result<Value, RuntimeError> {
    Ok(Value::Int(args[0].len().map_err(RuntimeError::new_no_pos)? as i64))
}

fn fn_has(args: Vec<Value>) -> Result<Value, RuntimeError> {
    match &args[0] {
        Value::Map(m) => Ok(Value::from(m.borrow().contains_key(&args[1]))),
        v => Err(format!("Argument to has must be a map, got {:?} ", v).into())
    }
}

fn fn_args(_: Vec<Value>) -> Result<Value, RuntimeError> {
    let mut args = std::env::args();
    args.next();
    let args = RefCell::new(args);
    Ok(Value::Func(Func::BuiltinClosure {
        arg_count: 0,
        func: Rc::new(move |_| {
            match args.borrow_mut().next() {
                Some(s) => Ok(Value::from(s)),
                None => Ok(Value::Nil)
            }
        })
    }))
}

fn fn_time(_: Vec<Value>) -> Result<Value, RuntimeError> {
    let time = SystemTime::now().duration_since(UNIX_EPOCH).map_err(|e| e.to_string())?;
    Ok(Value::from(time.as_secs_f64()))
}

fn fn_list(args: Vec<Value>) -> Result<Value, RuntimeError> {
    let a = args[0].iter()?;
    let mut res = Vec::new();
    for v in a { res.push(v?); }
    Ok(Value::from(res))
}

fn fn_push(args: Vec<Value>) -> Result<Value, RuntimeError> {
    if let Value::List(l) = &args[0] {
        l.as_ref().borrow_mut().push(args[1].clone());
        Ok(Value::Nil)
    } else{
        Err("First argument to push must be a list".into())
    }
}

fn fn_pop(args: Vec<Value>) -> Result<Value, RuntimeError> {
    if let Value::List(l) = &args[0] {
        l.as_ref().borrow_mut().pop().ok_or_else(|| "Pop on empty list".into())
    } else{
        Err("First argument to pop must be a list".into())
    }
}

fn fn_append(args: Vec<Value>) -> Result<Value, RuntimeError> {
    match (&args[0], &args[1]) {
        (Value::List(a), Value::List(b)) => {
            let mut newvals = b.borrow().clone();
            a.borrow_mut().append(&mut newvals);
            Ok(Value::Nil)
        },
        _ => Err("Both arguments to append must be lists".into())
    }
}

fn fn_insert(args: Vec<Value>) -> Result<Value, RuntimeError> {
    match (&args[0], &args[1]) {
        (Value::List(a), Value::Int(i)) => {
            if *i < 0 {
                return Err(format!("List index {} cannot be negative", i).into())
            }
            if *i > a.borrow().len() as i64 {
                return Err(format!("List index {} not valid for list of length {}", i, a.borrow().len()).into())
            }
            a.borrow_mut().insert(*i as usize, args[2].clone());
            Ok(Value::Nil)
        },
        (Value::Map(a), b) => {
            Ok(a.borrow_mut().insert(b.clone(), args[3].clone()).unwrap_or(Value::Nil))
        },
        (Value::List(_), _) => Err("Second argument to insert must be an integer when the first is a list".into()),
        _ => Err("First argument to insert must be a list or map".into()),
    }
}

fn fn_remove(args: Vec<Value>) -> Result<Value, RuntimeError> {
    match (&args[0], &args[1]) {
        (Value::List(a), Value::Int(i)) => {
            if *i < 0 {
                return Err(format!("List index {} cannot be negative", i).into())
            }
            if *i >= a.borrow().len() as i64 {
                return Err(format!("List index {} not valid for list of length {}", i, a.borrow().len()).into())
            }
            Ok(a.borrow_mut().remove(*i as usize))
        },
        (Value::Map(a), b) => {
            Ok(a.borrow_mut().remove(b).unwrap_or(Value::Nil))
        },
        (Value::List(_), _) => Err("Second argument to remove must be an integer when the first is a list".into()),
        _ => Err("First argument to remove must be a list or map".into()),
    }
}