use std::hash::{DefaultHasher, Hasher};
use rand::Rng;
use matrix_lang::prelude::*;
use matrix_macros::native_func;
use crate::{VmArgs, next, error, unpack_args, unpack_varargs};

fn to_radix(r: i64, mut n: i64) -> String {
    let mut result = String::new();
    let mut idx = 0;
    if n == 0 {
        result.push('0');
        return result
    } else if n < 0 {
        n = -n;
        idx = 1;
        result.push('-');
    }
    while n != 0 {
        let c = std::char::from_digit((n % r) as u32, r as u32).unwrap();
        result.insert(idx, c);
        n /= r;
    }
    result
}

#[native_func(1)]
fn bin(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [value] = unpack_args!(args);
    match value {
        Value::Int(n) => Ok(Value::String(to_radix(2, n).into())),
        _ => error!("bin requires a integer agument")
    }
}

#[native_func(1)]
fn sex(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [value] = unpack_args!(args);
    match value {
        Value::Int(n) => Ok(Value::String(to_radix(6, n).into())),
        _ => error!("sex requires a integer agument")
    }
}

#[native_func(1)]
fn oct(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [value] = unpack_args!(args);
    match value {
        Value::Int(n) => Ok(Value::String(to_radix(8, n).into())),
        _ => error!("oct requires a integer agument")
    }
}

#[native_func(1)]
fn hex(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [value] = unpack_args!(args);
    match value {
        Value::Int(n) => Ok(Value::String(to_radix(16, n).into())),
        _ => error!("hex requires a integer agument")
    }
}

#[native_func(2)]
fn radix(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [radix, value] = unpack_args!(args);
    match (radix, value) {
        (Value::Int(r), Value::Int(n)) => Ok(Value::String(to_radix(r, n).into())),
        _ => error!("radix requires two integer aguments")
    }
}

#[native_func(1..)]
fn append(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let ([list], args) = unpack_varargs!(args);
    let Value::List(mut list) = list else {
        return error!("append requires a list")
    };
    for arg in args {
        list.push(arg);
    };
    Ok(Value::List(list))
}

#[native_func(2)]
fn push(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [list, value] = unpack_args!(args);
    let Value::List(mut list) = list else {
        return error!("push requires a list")
    };
    list.push(value);
    Ok(Value::List(list))
}

#[native_func(1)]
fn pop(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [list] = unpack_args!(args);
    let Value::List(mut list) = list else {
        return error!("pop requires a list")
    };
    match list.pop() {
        Some(v) => Ok(v),
        None => Ok(Value::Nil)
    }
}

#[native_func(2)]
fn remove(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [list, index] = unpack_args!(args);
    let Value::List(mut list) = list else {
        return error!("remove requires a list")
    };
    let Value::Int(i) = index else {
        return error!("remove reuqires a int index");
    };
    if i < 0 || i as usize >= list.len() {
        Ok(Value::Nil)
    } else {
        Ok(list.remove(i as usize))
    }
}

#[native_func(1)]
fn hash(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [value] = unpack_args!(args);
    let mut hasher = DefaultHasher::new();
    value.try_hash(&mut hasher)?;
    let fin = hasher.finish();
    Ok(Value::Int(fin as u32 as i64))
}

#[native_func(1)]
fn ord(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [value] = unpack_args!(args);
    let Value::String(str) = value else {
        return error!("ord requires a 1 length string")
    };
    if str.len() != 1 {
        return error!("ord requires a 1 length string")
    }
    let char = str.chars().next().unwrap();
    Ok(Value::Int(char as i64))
}

#[native_func(1)]
fn chr(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [value] = unpack_args!(args);
    let Value::Int(i) = value else {
        return error!("chr requires an int")
    };
    match char::from_u32(i as u32) {
        Some(c) => Ok(Value::String(String::from(c).into())),
        None => error!("unable to get char from: {}", i as u32)
    }
}

#[native_func(1)]
fn str(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [value] = unpack_args!(args);
    Ok(Value::String(format!("{value}").into()))
}

fn partition(list: &mut [Value], lo: usize, hi: usize) -> (usize, usize) {
    let pivot = list[(lo + hi) / 2].clone();
    let mut lt = lo;
    let mut eq = lo;
    let mut gt = hi;

    while eq <= gt {
        if list[eq] < pivot {
            list.swap(eq, lt);
            lt += 1;
            eq += 1;
        } else if list[eq] > pivot {
            list.swap(eq, gt);
            gt -= 1;
        } else {
            eq += 1;
        }
    }

    (lt, gt)
}

fn quicksort(list: &mut [Value], lo: usize, hi: usize) {
    if lo < hi {
        let (lt, gt) = partition(list, lo, hi);
        if lt > 0 {
            quicksort(list, lo, lt - 1);
        }
        quicksort(list, gt + 1, hi);
    }
}

#[native_func(1)]
fn sort(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    let [value] = unpack_args!(args);
    let Value::List(mut list) = value else {
        return error!("sort requires a list")
    };
    if list.len() > 1 {
        let hi = list.len() - 1;
        quicksort(list.as_mut(), 0, hi);
    }
    Ok(Value::List(list))
}

#[native_func(0)]
fn rand(_: VmArgs, _: Vec<Value>) -> Result<Value> {
    let mut rng = rand::thread_rng();
    Ok(Value::Float(rng.gen()))
}

#[native_func(0..)]
fn rand_range(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    use Value as V;
    let ([], varargs) = unpack_varargs!(args);
    let (min, max, step) = match varargs.as_slice() {
        [V::Int(max)] => {
            (0, *max, 1)
        },
        [V::Int(min), V::Int(max)] => {
            (*min, *max, 1)
        },
        [V::Int(min), V::Int(max), V::Int(step)] => {
            (*min, *max, *step)
        },
        _ => return error!("rand_range takes 1 to 3 [Int]'s")
    };
    if max <= min {
        return Ok(Value::Int(min))
    }
    let count = ((max - 1 - min) / step) + 1;
    let rng = (rand::thread_rng().gen::<u32>() % (count as u32)) as i64;
    let i = min + (rng * step);
    Ok(Value::Int(i))
}

#[native_func(2)]
fn rand_int(_: VmArgs, args: Vec<Value>) -> Result<Value> {
    use Value as V;
    let (min, max) = match args.as_slice() {
        [V::Int(min), V::Int(max)] => {
            (*min, *max + 1)
        },
        _ => return error!("rand_int takes 2 [Int]'s")
    };
    if max <= min {
        return Ok(Value::Int(min))
    }

    let count = max - min;
    let rng = (rand::thread_rng().gen::<u32>() % (count as u32)) as i64;
    let i = min + rng;
    Ok(Value::Int(i))
}

#[native_func(1)]
fn rand_in((vm, frame): VmArgs, args: Vec<Value>) -> Result<Value> {
    let [iter] = unpack_args!(args);
    let iter = iter.into_iter_fn()?;
    let mut vals = Vec::new();
    loop {
        let val = next!(vm, frame, iter)?;
        if val == Value::Nil { break }
        vals.push(val);
    }
    if vals.is_empty() {
        return Ok(Value::Nil)
    }
    let idx = rand::thread_rng().gen::<usize>() % vals.len();
    Ok(vals[idx].clone())
}

pub fn load(vm: &mut Vm) {
    vm.load_global_fn(bin(), "bin");
    vm.load_global_fn(sex(), "sex");
    vm.load_global_fn(oct(), "oct");
    vm.load_global_fn(hex(), "hex");
    vm.load_global_fn(radix(), "radix");
    vm.load_global_fn(str(), "str");

    vm.load_global_fn(append(), "append");
    vm.load_global_fn(push(), "push");
    vm.load_global_fn(pop(), "pop");
    vm.load_global_fn(remove(), "remove");

    vm.load_global_fn(hash(), "hash");
    vm.load_global_fn(ord(), "ord");
    vm.load_global_fn(chr(), "chr");

    vm.load_global_fn(sort(), "sort");
    vm.load_global_fn(rand(), "rand");
    vm.load_global_fn(rand_range(), "rand_range");
    vm.load_global_fn(rand_int(), "rand_int");
    vm.load_global_fn(rand_in(), "rand_in");
}