use bytemuck::TransparentWrapper;

use std::borrow::{Cow, Borrow};
use std::cmp::Ordering;
use std::fmt::Debug;
use std::hash::{Hash, Hasher};
use std::vec::Vec;

pub use std::collections::BTreeSet as Set;
pub use std::collections::BTreeMap as Map;

pub mod float;
pub mod signed_integer;

pub use float::Float;
pub use float::Double;
pub use signed_integer::SignedInteger;

/// The kinds of `Value` from the specification.
#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub enum ValueClass {
    Atomic(AtomClass),
    Compound(CompoundClass),
    Embedded,
}

/// The kinds of `Atom` from the specification.
#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub enum AtomClass {
    Boolean,
    Float,
    Double,
    SignedInteger,
    String,
    ByteString,
    Symbol,
}

/// The kinds of `Compound` from the specification.
#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub enum CompoundClass {
    Record,
    Sequence,
    Set,
    Dictionary,
}

pub trait Domain: Debug + Eq + Hash + Ord + Clone {}

#[derive(Debug)]
pub struct OutOfRange;

pub trait Value<D: Domain>: Debug {
    fn value_class(&self) -> ValueClass;

    fn as_boolean(&self) -> Option<bool> { None }
    fn as_float(&self) -> Option<f32> { None }
    fn as_double(&self) -> Option<f64> { None }

    fn is_signed_integer(&self) -> bool { false }
    fn as_signed_integer(&self) -> Option<SignedInteger> { None }

    fn as_string(&self) -> Option<Cow<'_, str>> { None }
    fn as_bytestring(&self) -> Option<Cow<'_, [u8]>> { None }
    fn as_symbol(&self) -> Option<Cow<'_, str>> { None }

    fn is_record(&self) -> bool { false }
    fn label(&self) -> &dyn Value<D> { panic!("Not a record") }

    fn is_sequence(&self) -> bool { false }
    fn len(&self) -> usize { panic!("Has no length") }
    fn index(&self, _i: usize) -> &dyn Value<D> { panic!("Not indexable") }
    fn iter(&self) -> Box<dyn Iterator<Item = &dyn Value<D>> + '_> { panic!("Not iterable") }

    fn is_set(&self) -> bool { false }
    fn has(&self, _v: &dyn Value<D>) -> bool { false }

    fn is_dictionary(&self) -> bool { false }
    fn get(&self, _k: &dyn Value<D>) -> Option<&dyn Value<D>> { None }
    fn entries(&self) -> Box<dyn Iterator<Item = (&dyn Value<D>, &dyn Value<D>)> + '_> { panic!("Not a dictionary") }

    fn is_embedded(&self) -> bool { false }
    fn embedded(&self) -> Cow<'_, D> { panic!("Not an embedded value") }

    fn annotations(&self) -> Option<&[Box<dyn Value<D>>]> { None }
}

pub fn value<D: Domain, V: Value<D>>(v: &V) -> &dyn Value<D> {
    v
}

pub fn owned<D: Domain, V: Value<D> + 'static>(v: V) -> Box<dyn Value<D>> {
    Box::new(v)
}

impl<'a, D: Domain, V: Value<D> + ?Sized> Value<D> for &'a V {
    fn value_class(&self) -> ValueClass { (*self).value_class() }
    fn as_boolean(&self) -> Option<bool> { (*self).as_boolean() }
    fn as_float(&self) -> Option<f32> { (*self).as_float() }
    fn as_double(&self) -> Option<f64> { (*self).as_double() }
    fn is_signed_integer(&self) -> bool { (*self).is_signed_integer() }
    fn as_signed_integer(&self) -> Option<SignedInteger> { (*self).as_signed_integer() }
    fn as_string(&self) -> Option<Cow<'_, str>> { (*self).as_string() }
    fn as_bytestring(&self) -> Option<Cow<'_, [u8]>> { (*self).as_bytestring() }
    fn as_symbol(&self) -> Option<Cow<'_, str>> { (*self).as_symbol() }
    fn is_record(&self) -> bool { (*self).is_record() }
    fn label(&self) -> &dyn Value<D> { (*self).label() }
    fn is_sequence(&self) -> bool { (*self).is_sequence() }
    fn len(&self) -> usize { (*self).len() }
    fn index(&self, i: usize) -> &dyn Value<D> { (*self).index(i) }
    fn iter(&self) -> Box<dyn Iterator<Item = &dyn Value<D>> + '_> { (*self).iter() }
    fn is_set(&self) -> bool { (*self).is_set() }
    fn has(&self, v: &dyn Value<D>) -> bool { (*self).has(v) }
    fn is_dictionary(&self) -> bool { (*self).is_dictionary() }
    fn get(&self, k: &dyn Value<D>) -> Option<&dyn Value<D>> { (*self).get(k) }
    fn entries(&self) -> Box<dyn Iterator<Item = (&dyn Value<D>, &dyn Value<D>)> + '_> { (*self).entries() }
    fn is_embedded(&self) -> bool { (*self).is_embedded() }
    fn embedded(&self) -> Cow<'_, D> { (*self).embedded() }
    fn annotations(&self) -> Option<&[Box<dyn Value<D>>]> { (*self).annotations() }
}

impl<D: Domain> Value<D> for Box<dyn Value<D>> {
    fn value_class(&self) -> ValueClass { self.as_ref().value_class() }
    fn as_boolean(&self) -> Option<bool> { self.as_ref().as_boolean() }
    fn as_float(&self) -> Option<f32> { self.as_ref().as_float() }
    fn as_double(&self) -> Option<f64> { self.as_ref().as_double() }
    fn is_signed_integer(&self) -> bool { self.as_ref().is_signed_integer() }
    fn as_signed_integer(&self) -> Option<SignedInteger> { self.as_ref().as_signed_integer() }
    fn as_string(&self) -> Option<Cow<'_, str>> { self.as_ref().as_string() }
    fn as_bytestring(&self) -> Option<Cow<'_, [u8]>> { self.as_ref().as_bytestring() }
    fn as_symbol(&self) -> Option<Cow<'_, str>> { self.as_ref().as_symbol() }
    fn is_record(&self) -> bool { self.as_ref().is_record() }
    fn label(&self) -> &dyn Value<D> { self.as_ref().label() }
    fn is_sequence(&self) -> bool { self.as_ref().is_sequence() }
    fn len(&self) -> usize { self.as_ref().len() }
    fn index(&self, i: usize) -> &dyn Value<D> { self.as_ref().index(i) }
    fn iter(&self) -> Box<dyn Iterator<Item = &dyn Value<D>> + '_> { self.as_ref().iter() }
    fn is_set(&self) -> bool { self.as_ref().is_set() }
    fn has(&self, v: &dyn Value<D>) -> bool { self.as_ref().has(v) }
    fn is_dictionary(&self) -> bool { self.as_ref().is_dictionary() }
    fn get(&self, k: &dyn Value<D>) -> Option<&dyn Value<D>> { self.as_ref().get(k) }
    fn entries(&self) -> Box<dyn Iterator<Item = (&dyn Value<D>, &dyn Value<D>)> + '_> { self.as_ref().entries() }
    fn is_embedded(&self) -> bool { self.as_ref().is_embedded() }
    fn embedded(&self) -> Cow<'_, D> { self.as_ref().embedded() }
    fn annotations(&self) -> Option<&[Box<dyn Value<D>>]> { self.as_ref().annotations() }
}

impl<'a, D: Domain> Hash for dyn Value<D> + 'a {
    fn hash<H: Hasher>(&self, state: &mut H) {
        match self.value_class() {
            ValueClass::Atomic(a) => match a {
                AtomClass::Boolean => self.as_boolean().unwrap().hash(state),
                AtomClass::Float => self.as_float().unwrap().to_bits().hash(state),
                AtomClass::Double => self.as_double().unwrap().to_bits().hash(state),
                AtomClass::SignedInteger => self.as_signed_integer().unwrap().hash(state),
                AtomClass::String => self.as_string().unwrap().hash(state),
                AtomClass::ByteString => self.as_bytestring().unwrap().hash(state),
                AtomClass::Symbol => self.as_symbol().unwrap().hash(state),
            }
            ValueClass::Compound(c) => match c {
                CompoundClass::Sequence |
                CompoundClass::Set => {
                    state.write_usize(self.len());
                    for v in self.iter() { v.hash(state) }
                }
                CompoundClass::Record => {
                    self.label().hash(state);
                    state.write_usize(self.len());
                    for v in self.iter() { v.hash(state) }
                }
                CompoundClass::Dictionary => {
                    state.write_usize(self.len());
                    for (k, v) in self.entries() {
                        k.hash(state);
                        v.hash(state);
                    }
                }
            }
            ValueClass::Embedded => self.embedded().hash(state),
        }
    }
}

fn iters_eq<'a, D: Domain>(
    mut i1: Box<dyn Iterator<Item = &dyn Value<D>> + 'a>,
    mut i2: Box<dyn Iterator<Item = &dyn Value<D>> + 'a>,
) -> bool {
    loop {
        match i1.next() {
            None => return i2.next().is_none(),
            Some(v1) => match i2.next() {
                None => return false,
                Some(v2) => if v1 != v2 { return false; },
            }
        }
    }
}

impl<'a, D: Domain> PartialEq for dyn Value<D> + 'a {
    fn eq(&self, other: &Self) -> bool {
        let cls = self.value_class();
        if cls != other.value_class() { return false; }
        match cls {
            ValueClass::Atomic(a) => match a {
                AtomClass::Boolean =>
                    self.as_boolean().unwrap() == other.as_boolean().unwrap(),
                AtomClass::Float =>
                    Float(self.as_float().unwrap()) == Float(other.as_float().unwrap()),
                AtomClass::Double =>
                    Double(self.as_double().unwrap()) == Double(other.as_double().unwrap()),
                AtomClass::SignedInteger =>
                    self.as_signed_integer().unwrap() == other.as_signed_integer().unwrap(),
                AtomClass::String =>
                    self.as_string().unwrap() == other.as_string().unwrap(),
                AtomClass::ByteString =>
                    self.as_bytestring().unwrap() == other.as_bytestring().unwrap(),
                AtomClass::Symbol =>
                    self.as_symbol().unwrap() == other.as_symbol().unwrap(),
            }
            ValueClass::Compound(c) => match c {
                CompoundClass::Record => {
                    if self.label() != other.label() { return false; }
                    iters_eq(self.iter(), other.iter())
                }
                CompoundClass::Sequence => {
                    iters_eq(self.iter(), other.iter())
                }
                CompoundClass::Set => {
                    let s1 = self.iter().collect::<Set<_>>();
                    let s2 = other.iter().collect::<Set<_>>();
                    s1 == s2
                }
                CompoundClass::Dictionary => {
                    let d1 = self.entries().collect::<Map<_, _>>();
                    let d2 = other.entries().collect::<Map<_, _>>();
                    d1 == d2
                }
            }
            ValueClass::Embedded => self.embedded() == other.embedded(),
        }
    }
}

fn iters_cmp<'a, D: Domain>(
    mut i1: Box<dyn Iterator<Item = &dyn Value<D>> + 'a>,
    mut i2: Box<dyn Iterator<Item = &dyn Value<D>> + 'a>,
) -> Ordering {
    loop {
        match i1.next() {
            None => match i2.next() {
                None => return Ordering::Equal,
                Some(_) => return Ordering::Less,
            }
            Some(v1) => match i2.next() {
                None => return Ordering::Greater,
                Some(v2) => match v1.cmp(v2) {
                    Ordering::Equal => (),
                    other => return other,
                }
            }
        }
    }
}

impl<'a, D: Domain> Ord for dyn Value<D> + 'a {
    fn cmp(&self, other: &Self) -> Ordering {
        let cls = self.value_class();
        cls.cmp(&other.value_class()).then_with(|| match cls {
            ValueClass::Atomic(a) => match a {
                AtomClass::Boolean =>
                    self.as_boolean().cmp(&other.as_boolean()),
                AtomClass::Float =>
                    Float(self.as_float().unwrap()).cmp(&Float(other.as_float().unwrap())),
                AtomClass::Double =>
                    Double(self.as_double().unwrap()).cmp(&Double(other.as_double().unwrap())),
                AtomClass::SignedInteger =>
                    self.as_signed_integer().cmp(&other.as_signed_integer()),
                AtomClass::String =>
                    self.as_string().cmp(&other.as_string()),
                AtomClass::ByteString =>
                    self.as_bytestring().cmp(&other.as_bytestring()),
                AtomClass::Symbol =>
                    self.as_symbol().cmp(&other.as_symbol()),
            },
            ValueClass::Compound(c) => match c {
                CompoundClass::Record =>
                    self.label().cmp(other.label()).then_with(
                        || iters_cmp(self.iter(), other.iter())),
                CompoundClass::Sequence => iters_cmp(self.iter(), other.iter()),
                CompoundClass::Set => {
                    let s1 = self.iter().collect::<Set<_>>();
                    let s2 = other.iter().collect::<Set<_>>();
                    s1.cmp(&s2)
                }
                CompoundClass::Dictionary => {
                    let d1 = self.entries().collect::<Map<_, _>>();
                    let d2 = other.entries().collect::<Map<_, _>>();
                    d1.cmp(&d2)
                }
            },
            ValueClass::Embedded => self.embedded().cmp(&other.embedded()),
        })
    }
}

impl<'a, D: Domain> Eq for dyn Value<D> + 'a {}

impl<'a, D: Domain> PartialOrd for dyn Value<D> + 'a {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub enum NoValue {}

impl Domain for NoValue {}

impl<D: Domain> Value<D> for NoValue {
    fn value_class(&self) -> ValueClass { unreachable!() }
}

impl<D: Domain> Value<D> for bool {
    fn value_class(&self) -> ValueClass { ValueClass::Atomic(AtomClass::Boolean) }
    fn as_boolean(&self) -> Option<bool> { Some(*self) }
}

impl<D: Domain> Value<D> for u64 {
    fn value_class(&self) -> ValueClass { ValueClass::Atomic(AtomClass::SignedInteger) }
    fn as_signed_integer(&self) -> Option<SignedInteger> {
        Some((*self).into())
    }
}

impl<D: Domain> Value<D> for Float {
    fn value_class(&self) -> ValueClass { ValueClass::Atomic(AtomClass::Float) }
    fn as_float(&self) -> Option<f32> { Some(self.0) }
    fn as_double(&self) -> Option<f64> { Some(self.0 as f64) }
}

impl<D: Domain> Value<D> for str {
    fn value_class(&self) -> ValueClass { ValueClass::Atomic(AtomClass::String) }
    fn as_string(&self) -> Option<Cow<'_, str>> { Some(Cow::Borrowed(self)) }
}

impl<D: Domain> Value<D> for String {
    fn value_class(&self) -> ValueClass { ValueClass::Atomic(AtomClass::String) }
    fn as_string(&self) -> Option<Cow<'_, str>> { Some(Cow::Borrowed(self)) }
}

impl<D: Domain, V: Value<D>> Value<D> for Vec<V> {
    fn value_class(&self) -> ValueClass { ValueClass::Compound(CompoundClass::Sequence) }
    fn is_sequence(&self) -> bool { true }
    fn len(&self) -> usize { self.len() }
    fn index(&self, i: usize) -> &dyn Value<D> { &self[i] }
    fn iter(&self) -> Box<dyn Iterator<Item = &dyn Value<D>> + '_> {
        Box::new(self[..].iter().map(value))
    }
}

impl<D: Domain, V: Value<D>> Value<D> for [V] {
    fn value_class(&self) -> ValueClass { ValueClass::Compound(CompoundClass::Sequence) }
    fn is_sequence(&self) -> bool { true }
    fn len(&self) -> usize { self.len() }
    fn index(&self, i: usize) -> &dyn Value<D> { &self[i] }
    fn iter(&self) -> Box<dyn Iterator<Item = &dyn Value<D>> + '_> {
        Box::new(self[..].iter().map(value))
    }
}

impl<D: Domain> Value<D> for Set<Box<dyn Value<D>>> {
    fn value_class(&self) -> ValueClass { ValueClass::Compound(CompoundClass::Set) }
    fn is_set(&self) -> bool { true }
    fn len(&self) -> usize { self.len() }
    fn has(&self, v: &dyn Value<D>) -> bool { self.contains(v) }
    fn iter(&self) -> Box<dyn Iterator<Item = &dyn Value<D>> + '_> {
        Box::new(self.iter().map(value))
    }
}

#[derive(PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
struct Key<'a, D: Domain>(dyn Value<D> + 'a);

// Many thanks to SkiFire13 and the other participants in
// https://users.rust-lang.org/t/is-the-lifetime-of-a-btreemap-get-result-attached-to-the-key-as-well-as-the-map/83568/7
// for the idea of using TransparentWrapper here.
//
unsafe impl<'a, D: Domain> TransparentWrapper<dyn Value<D> + 'a> for Key<'a, D> {}
impl<'a, 'b: 'a, D: Domain> Borrow<Key<'a, D>> for Box<dyn Value<D> + 'b> {
    fn borrow(&self) -> &Key<'a, D> {
        Key::wrap_ref(&**self)
    }
}

impl<D: Domain, V: Value<D>> Value<D> for Map<Box<dyn Value<D>>, V> {
    fn value_class(&self) -> ValueClass { ValueClass::Compound(CompoundClass::Dictionary) }
    fn is_dictionary(&self) -> bool { true }
    fn len(&self) -> usize { self.len() }
    fn has(&self, v: &dyn Value<D>) -> bool { self.contains_key(v) }
    fn get(&self, k: &dyn Value<D>) -> Option<&dyn Value<D>> {
        match Map::get(self, Key::wrap_ref(&k)) {
            Some(v) => Some(v),
            None => None,
        }
    }
    fn entries(&self) -> Box<dyn Iterator<Item = (&dyn Value<D>, &dyn Value<D>)> + '_> {
        Box::new(self.iter().map(|(k,v)| (value(k), value(v))))
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct Record<V>(Vec<V> /* at least one element, for the label */);

impl<V> Record<V> {
    pub fn new(label: V, mut fields: Vec<V>) -> Self {
        fields.insert(0, label);
        Record(fields)
    }
}

impl<D: Domain, V: Value<D>> Value<D> for Record<V> {
    fn value_class(&self) -> ValueClass { ValueClass::Compound(CompoundClass::Record) }
    fn is_record(&self) -> bool { true }
    fn label(&self) -> &dyn Value<D> { &self.0[0] }
    fn len(&self) -> usize { self.0.len() - 1 }
    fn index(&self, i: usize) -> &dyn Value<D> { &self.0[i + 1] }
    fn iter(&self) -> Box<dyn Iterator<Item = &dyn Value<D>> + '_> {
        Box::new(self.0[1..].iter().map(value))
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct Symbol<T: AsRef<str> + Debug>(T);

impl<T: AsRef<str> + Debug, D: Domain> Value<D> for Symbol<T> {
    fn value_class(&self) -> ValueClass { ValueClass::Atomic(AtomClass::Symbol) }
    fn as_symbol(&self) -> Option<Cow<'_, str>> { Some(Cow::Borrowed(self.0.as_ref())) }
}

#[derive(Debug)]
pub struct Annotations<D: Domain, V: Value<D>>(V, Vec<Box<dyn Value<D>>>);

impl<D: Domain, V: Value<D>> Annotations<D, V> {
    pub fn value(&self) -> &dyn Value<D> {
        &self.0
    }
}

impl<D: Domain, V: Value<D>> Value<D> for Annotations<D, V> {
    fn value_class(&self) -> ValueClass { self.value().value_class() }
    fn as_boolean(&self) -> Option<bool> { self.value().as_boolean() }
    fn as_float(&self) -> Option<f32> { self.value().as_float() }
    fn as_double(&self) -> Option<f64> { self.value().as_double() }
    fn is_signed_integer(&self) -> bool { self.value().is_signed_integer() }
    fn as_signed_integer(&self) -> Option<SignedInteger> { self.value().as_signed_integer() }
    fn as_string(&self) -> Option<Cow<'_, str>> { self.value().as_string() }
    fn as_bytestring(&self) -> Option<Cow<'_, [u8]>> { self.value().as_bytestring() }
    fn as_symbol(&self) -> Option<Cow<'_, str>> { self.value().as_symbol() }
    fn is_record(&self) -> bool { self.value().is_record() }
    fn label(&self) -> &dyn Value<D> { self.value().label() }
    fn is_sequence(&self) -> bool { self.value().is_sequence() }
    fn len(&self) -> usize { self.value().len() }
    fn index(&self, i: usize) -> &dyn Value<D> { self.value().index(i) }
    fn iter(&self) -> Box<dyn Iterator<Item = &dyn Value<D>> + '_> { self.value().iter() }
    fn is_set(&self) -> bool { self.value().is_set() }
    fn has(&self, v: &dyn Value<D>) -> bool { self.value().has(v) }
    fn is_dictionary(&self) -> bool { self.value().is_dictionary() }
    fn get(&self, k: &dyn Value<D>) -> Option<&dyn Value<D>> { self.value().get(k) }
    fn entries(&self) -> Box<dyn Iterator<Item = (&dyn Value<D>, &dyn Value<D>)> + '_> { self.value().entries() }
    fn is_embedded(&self) -> bool { self.value().is_embedded() }
    fn embedded(&self) -> Cow<'_, D> { self.value().embedded() }
    fn annotations(&self) -> Option<&[Box<dyn Value<D>>]> { Some(&self.1) }
}

impl<D: Domain, V: Value<D>> PartialEq for Annotations<D, V> {
    fn eq(&self, other: &Self) -> bool {
        self.value().eq(&other.value())
    }
}

impl<D: Domain, V: Value<D>> Eq for Annotations<D, V> {}

impl<D: Domain, V: Value<D>> Hash for Annotations<D, V> {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.value().hash(state);
    }
}

impl<D: Domain, V: Value<D>> PartialOrd for Annotations<D, V> {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl<D: Domain, V: Value<D>> Ord for Annotations<D, V> {
    fn cmp(&self, other: &Self) -> Ordering {
        self.value().cmp(&other.value())
    }
}

#[cfg(test)]
mod demo {
    use crate::*;

    fn getit<'a>(d: &'a dyn Value<NoValue>, k: &str) -> Option<&'a dyn Value<NoValue>> {
        d.get(&k)
    }

    #[test] fn a() {
        let l = Symbol("label");
        let r = Record::new(owned::<NoValue, _>(l.clone()), vec![owned(1), owned(2), owned(3)]);
        let r2 = Record::new(owned::<NoValue, _>(l), vec![owned(1), owned(2), owned(4)]);

        let mut v: Map<Box<dyn Value<NoValue>>, String> = Map::new();
        v.insert(Box::new("abc"), "def".to_owned());
        v.insert(Box::new(123), "xyz".to_owned());
        v.insert(Box::new(vec![1, 2, 3]), "www".to_owned());
        v.insert(Box::new(r2), "bbb".to_owned());
        v.insert(Box::new(r), "aaa".to_owned());
        let w: &dyn Value<NoValue> = &v;
        println!("GETw abc {:?}", w.get(&"abc"));
        println!("GETw 123 {:?}", w.get(&123));
        println!("GETw qqq {:?}", w.get(&"qqq"));
        println!("GETv abc {:?}", v.get(value(&"abc")));
        println!("GETv 123 {:?}", v.get(value(&123)));
        println!("GETv qqq {:?}", v.get(value(&"qqq")));
        for (kk, vv) in w.entries() {
            println!("{:?} {:?} ==> {:?} {:?}", kk.value_class(), kk, vv.value_class(), vv);
        }

        // {
        //     use std::io::BufRead;
        //     for line in std::io::stdin().lock().lines() {
        //         let line = line.unwrap();
        //         let val = w.get(&line);
        //         println!("{:?} ==> {:?} == {:?}", line, val, getit(&v, &line));
        //     }
        // }
    }
}