use crate::js::{
    function::{Function, NativeFunction, NativeFunctionData},
    object::{ObjectData, ObjectKind, Property, INSTANCE_PROTOTYPE, PROTOTYPE},
};
use gc::{Gc, GcCell};
use gc_derive::{Finalize, Trace};
use serde_json::{map::Map, Number as JSONNumber, Value as JSONValue};
use std::{
    f64::NAN,
    fmt::{self, Display},
    ops::{Add, BitAnd, BitOr, BitXor, Deref, DerefMut, Div, Mul, Not, Rem, Shl, Shr, Sub},
    str::FromStr,
};

#[must_use]
/// The result of a Javascript expression is represented like this so it can succeed (`Ok`) or fail (`Err`)
pub type ResultValue = Result<Value, Value>;
/// A Garbage-collected Javascript value as represented in the interpreter
pub type Value = Gc<ValueData>;

/// A Javascript value
#[derive(Trace, Finalize, Debug, Clone)]
pub enum ValueData {
    /// `null` - A null value, for when a value doesn't exist
    Null,
    /// `undefined` - An undefined value, for when a field or index doesn't exist
    Undefined,
    /// `boolean` - A `true` / `false` value, for if a certain criteria is met
    Boolean(bool),
    /// `String` - A UTF-8 string, such as `"Hello, world"`
    String(String),
    /// `Number` - A 64-bit floating point number, such as `3.1415`
    Number(f64),
    /// `Number` - A 32-bit integer, such as `42`
    Integer(i32),
    /// `Object` - An object, such as `Math`, represented by a binary tree of string keys to Javascript values
    Object(GcCell<ObjectData>),
    /// `Function` - A runnable block of code, such as `Math.sqrt`, which can take some variables and return a useful value or act upon an object
    Function(Box<GcCell<Function>>),
}

impl ValueData {
    /// Returns a new empty object
    pub fn new_obj(global: Option<&Value>) -> Value {
        let mut obj = ObjectData::default();

        if global.is_some() {
            let obj_proto = global
                .unwrap()
                .get_field_slice("Object")
                .get_field_slice(PROTOTYPE);
            obj.properties
                .insert(INSTANCE_PROTOTYPE.to_string(), Property::new(obj_proto));
        }
        Gc::new(ValueData::Object(GcCell::new(obj)))
    }

    /// Similar to `new_obj`, but you can pass a prototype to create from
    pub fn new_obj_from_prototype(proto: Value) -> Value {
        let mut obj = ObjectData::default();

        obj.internal_slots
            .insert(INSTANCE_PROTOTYPE.to_string(), proto);
        Gc::new(ValueData::Object(GcCell::new(obj)))
    }

    /// This will tell us if we can exten an object or not, not properly implemented yet, for now always returns true
    /// For scalar types it should be false, for objects check the private field for extensibilaty. By default true
    /// <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/seal would turn extensible to false/>
    /// <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze would also turn extensible to false/>
    pub fn is_extensible(&self) -> bool {
        true
    }

    /// Returns true if the value is an object
    pub fn is_object(&self) -> bool {
        match *self {
            ValueData::Object(_) => true,
            _ => false,
        }
    }

    /// Returns true if the value is a function
    pub fn is_function(&self) -> bool {
        match *self {
            ValueData::Function(_) => true,
            _ => false,
        }
    }

    /// Returns true if the value is undefined
    pub fn is_undefined(&self) -> bool {
        match *self {
            ValueData::Undefined => true,
            _ => false,
        }
    }

    /// Returns true if the value is null
    pub fn is_null(&self) -> bool {
        match *self {
            ValueData::Null => true,
            _ => false,
        }
    }

    /// Returns true if the value is null or undefined
    pub fn is_null_or_undefined(&self) -> bool {
        match *self {
            ValueData::Null | ValueData::Undefined => true,
            _ => false,
        }
    }

    /// Returns true if the value is a 64-bit floating-point number
    pub fn is_double(&self) -> bool {
        match *self {
            ValueData::Number(_) => true,
            _ => false,
        }
    }

    /// Returns true if the value is a string
    pub fn is_string(&self) -> bool {
        match *self {
            ValueData::String(_) => true,
            _ => false,
        }
    }

    /// Returns true if the value is true
    /// [toBoolean](https://tc39.github.io/ecma262/#sec-toboolean)
    pub fn is_true(&self) -> bool {
        match *self {
            ValueData::Object(_) => true,
            ValueData::String(ref s) if !s.is_empty() => true,
            ValueData::Number(n) if n != 0.0 && !n.is_nan() => true,
            ValueData::Integer(n) if n != 0 => true,
            ValueData::Boolean(v) => v,
            _ => false,
        }
    }

    /// Converts the value into a 64-bit floating point number
    pub fn to_num(&self) -> f64 {
        match *self {
            ValueData::Object(_) | ValueData::Undefined | ValueData::Function(_) => NAN,
            ValueData::String(ref str) => match FromStr::from_str(str) {
                Ok(num) => num,
                Err(_) => NAN,
            },
            ValueData::Number(num) => num,
            ValueData::Boolean(true) => 1.0,
            ValueData::Boolean(false) | ValueData::Null => 0.0,
            ValueData::Integer(num) => f64::from(num),
        }
    }

    /// Converts the value into a 32-bit integer
    pub fn to_int(&self) -> i32 {
        match *self {
            ValueData::Object(_)
            | ValueData::Undefined
            | ValueData::Null
            | ValueData::Boolean(false)
            | ValueData::Function(_) => 0,
            ValueData::String(ref str) => match FromStr::from_str(str) {
                Ok(num) => num,
                Err(_) => 0,
            },
            ValueData::Number(num) => num as i32,
            ValueData::Boolean(true) => 1,
            ValueData::Integer(num) => num,
        }
    }

    /// remove_prop removes a property from a Value object.
    /// It will return a boolean based on if the value was removed, if there was no value to remove false is returned
    pub fn remove_prop(&self, field: &str) {
        match *self {
            ValueData::Object(ref obj) => obj.borrow_mut().deref_mut().properties.remove(field),
            // Accesing .object on borrow() seems to automatically dereference it, so we don't need the *
            ValueData::Function(ref func) => match func.borrow_mut().deref_mut() {
                Function::NativeFunc(ref mut func) => func.object.properties.remove(field),
                Function::RegularFunc(ref mut func) => func.object.properties.remove(field),
            },
            _ => None,
        };
    }

    /// Resolve the property in the object
    /// Returns a copy of the Property
    pub fn get_prop(&self, field: &str) -> Option<Property> {
        // Spidermonkey has its own GetLengthProperty: https://searchfox.org/mozilla-central/source/js/src/vm/Interpreter-inl.h#154
        // This is only for primitive strings, String() objects have their lengths calculated in string.rs
        if self.is_string() && field == "length" {
            if let ValueData::String(ref s) = *self {
                return Some(Property::new(to_value(s.len() as i32)));
            }
        }

        let obj: ObjectData = match *self {
            ValueData::Object(ref obj) => {
                let hash = obj.clone();
                // TODO: This will break, we should return a GcCellRefMut instead
                // into_inner will consume the wrapped value and remove it from the hashmap
                hash.into_inner()
            }
            // Accesing .object on borrow() seems to automatically dereference it, so we don't need the *
            ValueData::Function(ref func) => match func.clone().into_inner() {
                Function::NativeFunc(ref func) => func.object.clone(),
                Function::RegularFunc(ref func) => func.object.clone(),
            },
            _ => return None,
        };

        match obj.properties.get(field) {
            Some(val) => Some(val.clone()),
            None => match obj.properties.get(&INSTANCE_PROTOTYPE.to_string()) {
                Some(prop) => prop.value.get_prop(field),
                None => None,
            },
        }
    }

    /// update_prop will overwrite individual [Property] fields, unlike
    /// Set_prop, which will overwrite prop with a new Property
    /// Mostly used internally for now
    pub fn update_prop(
        &self,
        field: &str,
        value: Option<Value>,
        enumerable: Option<bool>,
        writable: Option<bool>,
        configurable: Option<bool>,
    ) {
        let obj: Option<ObjectData> = match self {
            ValueData::Object(ref obj) => Some(obj.borrow_mut().deref_mut().clone()),
            // Accesing .object on borrow() seems to automatically dereference it, so we don't need the *
            ValueData::Function(ref func) => match func.borrow_mut().deref_mut() {
                Function::NativeFunc(ref mut func) => Some(func.object.clone()),
                Function::RegularFunc(ref mut func) => Some(func.object.clone()),
            },
            _ => None,
        };

        if let Some(mut obj_data) = obj {
            // Use value, or walk up the prototype chain
            if let Some(ref mut prop) = obj_data.properties.get_mut(field) {
                prop.value = value.unwrap_or_else(|| prop.value.clone());
                prop.enumerable = enumerable.unwrap_or(prop.enumerable);
                prop.writable = writable.unwrap_or(prop.writable);
                prop.configurable = configurable.unwrap_or(prop.configurable);
            }
        }
    }

    /// Resolve the property in the object
    /// Returns a copy of the Property
    pub fn get_internal_slot(&self, field: &str) -> Value {
        let obj: ObjectData = match *self {
            ValueData::Object(ref obj) => {
                let hash = obj.clone();
                hash.into_inner()
            }
            _ => return Gc::new(ValueData::Undefined),
        };

        match obj.internal_slots.get(field) {
            Some(val) => val.clone(),
            None => Gc::new(ValueData::Undefined),
        }
    }

    /// Resolve the property in the object and get its value, or undefined if this is not an object or the field doesn't exist
    /// get_field recieves a Property from get_prop(). It should then return the [[Get]] result value if that's set, otherwise fall back to [[Value]]
    pub fn get_field(&self, field: &str) -> Value {
        match self.get_prop(field) {
            Some(prop) => {
                // If the Property has [[Get]] set to a function, we should run that and return the Value
                let prop_getter = match *prop.get {
                    ValueData::Function(ref v) => match *v.borrow() {
                        Function::NativeFunc(ref _ntv) => {
                            None // this never worked properly anyway
                        }
                        _ => None,
                    },
                    _ => None,
                };

                // If the getter is populated, use that. If not use [[Value]] instead
                match prop_getter {
                    Some(val) => val,
                    None => prop.value.clone(),
                }
            }
            None => Gc::new(ValueData::Undefined),
        }
    }

    /// Check to see if the Value has the field, mainly used by environment records
    pub fn has_field(&self, field: &str) -> bool {
        self.get_prop(field).is_some()
    }

    /// Resolve the property in the object and get its value, or undefined if this is not an object or the field doesn't exist
    pub fn get_field_slice(&self, field: &str) -> Value {
        self.get_field(field)
    }

    /// Set the field in the value
    pub fn set_field(&self, field: String, val: Value) -> Value {
        match *self {
            ValueData::Object(ref obj) => {
                obj.borrow_mut()
                    .properties
                    .insert(field, Property::new(val.clone()));
            }
            ValueData::Function(ref func) => {
                match *func.borrow_mut().deref_mut() {
                    Function::NativeFunc(ref mut f) => f
                        .object
                        .properties
                        .insert(field, Property::new(val.clone())),
                    Function::RegularFunc(ref mut f) => f
                        .object
                        .properties
                        .insert(field, Property::new(val.clone())),
                };
            }
            _ => (),
        }
        val
    }

    /// Set the field in the value
    pub fn set_field_slice<'a>(&self, field: &'a str, val: Value) -> Value {
        self.set_field(field.to_string(), val)
    }

    /// Set the private field in the value
    pub fn set_internal_slot(&self, field: &str, val: Value) -> Value {
        if let ValueData::Object(ref obj) = *self {
            obj.borrow_mut()
                .internal_slots
                .insert(field.to_string(), val.clone());
        }
        val
    }

    /// Set the kind of an object
    pub fn set_kind(&self, kind: ObjectKind) -> ObjectKind {
        if let ValueData::Object(ref obj) = *self {
            obj.borrow_mut().kind = kind.clone();
        }
        kind
    }

    /// Set the property in the value
    pub fn set_prop(&self, field: String, prop: Property) -> Property {
        match *self {
            ValueData::Object(ref obj) => {
                obj.borrow_mut().properties.insert(field, prop.clone());
            }
            ValueData::Function(ref func) => {
                match *func.borrow_mut().deref_mut() {
                    Function::NativeFunc(ref mut f) => {
                        f.object.properties.insert(field, prop.clone())
                    }
                    Function::RegularFunc(ref mut f) => {
                        f.object.properties.insert(field, prop.clone())
                    }
                };
            }
            _ => (),
        }
        prop
    }

    /// Set the property in the value
    pub fn set_prop_slice<'t>(&self, field: &'t str, prop: Property) -> Property {
        self.set_prop(field.to_string(), prop)
    }

    /// Convert from a JSON value to a JS value
    pub fn from_json(json: JSONValue) -> Self {
        match json {
            JSONValue::Number(v) => ValueData::Number(v.as_f64().unwrap()),
            JSONValue::String(v) => ValueData::String(v),
            JSONValue::Bool(v) => ValueData::Boolean(v),
            JSONValue::Array(vs) => {
                let mut new_obj = ObjectData::default();
                for (idx, json) in vs.iter().enumerate() {
                    new_obj
                        .properties
                        .insert(idx.to_string(), Property::new(to_value(json.clone())));
                }
                new_obj.properties.insert(
                    "length".to_string(),
                    Property::new(to_value(vs.len() as i32)),
                );
                ValueData::Object(GcCell::new(new_obj))
            }
            JSONValue::Object(obj) => {
                let mut new_obj = ObjectData::default();
                for (key, json) in obj.iter() {
                    new_obj
                        .properties
                        .insert(key.clone(), Property::new(to_value(json.clone())));
                }

                ValueData::Object(GcCell::new(new_obj))
            }
            JSONValue::Null => ValueData::Null,
        }
    }

    pub fn to_json(&self) -> JSONValue {
        match *self {
            ValueData::Null | ValueData::Undefined | ValueData::Function(_) => JSONValue::Null,
            ValueData::Boolean(b) => JSONValue::Bool(b),
            ValueData::Object(ref obj) => {
                let mut new_obj = Map::new();
                for (k, v) in obj.borrow().properties.iter() {
                    if k != INSTANCE_PROTOTYPE {
                        new_obj.insert(k.clone(), v.value.to_json());
                    }
                }
                JSONValue::Object(new_obj)
            }
            ValueData::String(ref str) => JSONValue::String(str.clone()),
            ValueData::Number(num) => JSONValue::Number(JSONNumber::from_f64(num).unwrap()),
            ValueData::Integer(val) => JSONValue::Number(JSONNumber::from(val)),
        }
    }

    /// Get the type of the value
    pub fn get_type(&self) -> &'static str {
        match *self {
            ValueData::Number(_) | ValueData::Integer(_) => "number",
            ValueData::String(_) => "string",
            ValueData::Boolean(_) => "boolean",
            ValueData::Null => "null",
            ValueData::Undefined => "undefined",
            _ => "object",
        }
    }
}

impl Display for ValueData {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            ValueData::Null => write!(f, "null"),
            ValueData::Undefined => write!(f, "undefined"),
            ValueData::Boolean(v) => write!(f, "{}", v),
            ValueData::String(ref v) => write!(f, "{}", v),
            ValueData::Number(v) => write!(
                f,
                "{}",
                match v {
                    _ if v.is_nan() => "NaN".to_string(),
                    _ if v.is_infinite() && v.is_sign_negative() => "-Infinity".to_string(),
                    _ if v.is_infinite() => "Infinity".to_string(),
                    _ => v.to_string(),
                }
            ),
            ValueData::Object(ref v) => {
                write!(f, "{{")?;
                // Print public properties
                if let Some((last_key, _)) = v.borrow().properties.iter().last() {
                    for (key, val) in v.borrow().properties.iter() {
                        write!(f, "{}: {}", key, val.value.clone())?;
                        if key != last_key {
                            write!(f, ", ")?;
                        }
                    }
                };

                // Print internal slots
                if let Some((last_key, _)) = v.borrow().internal_slots.iter().last() {
                    for (key, val) in v.borrow().internal_slots.iter() {
                        write!(f, "[[{}]]: {}", key, &val)?;
                        if key != last_key {
                            write!(f, ", ")?;
                        }
                    }
                };
                write!(f, "}}")
            }
            ValueData::Integer(v) => write!(f, "{}", v),
            ValueData::Function(ref v) => match *v.borrow() {
                Function::NativeFunc(_) => write!(f, "function() {{ [native code] }}"),
                Function::RegularFunc(ref rf) => {
                    write!(f, "function({}){}", rf.args.join(", "), rf.expr)
                }
            },
        }
    }
}

impl PartialEq for ValueData {
    fn eq(&self, other: &Self) -> bool {
        match (self.clone(), other.clone()) {
            // TODO: fix this
            // _ if self.ptr.to_inner() == &other.ptr.to_inner() => true,
            _ if self.is_null_or_undefined() && other.is_null_or_undefined() => true,
            (ValueData::String(_), _) | (_, ValueData::String(_)) => {
                self.to_string() == other.to_string()
            }
            (ValueData::Boolean(a), ValueData::Boolean(b)) if a == b => true,
            (ValueData::Number(a), ValueData::Number(b))
                if a == b && !a.is_nan() && !b.is_nan() =>
            {
                true
            }
            (ValueData::Number(a), _) if a == other.to_num() => true,
            (_, ValueData::Number(a)) if a == self.to_num() => true,
            (ValueData::Integer(a), ValueData::Integer(b)) if a == b => true,
            _ => false,
        }
    }
}

impl Add for ValueData {
    type Output = Self;
    fn add(self, other: Self) -> Self {
        match (self, other) {
            (ValueData::String(ref s), ref o) => ValueData::String(s.clone() + &o.to_string()),
            (ref s, ValueData::String(ref o)) => ValueData::String(s.to_string() + o),
            (ref s, ref o) => ValueData::Number(s.to_num() + o.to_num()),
        }
    }
}
impl Sub for ValueData {
    type Output = Self;
    fn sub(self, other: Self) -> Self {
        ValueData::Number(self.to_num() - other.to_num())
    }
}
impl Mul for ValueData {
    type Output = Self;
    fn mul(self, other: Self) -> Self {
        ValueData::Number(self.to_num() * other.to_num())
    }
}
impl Div for ValueData {
    type Output = Self;
    fn div(self, other: Self) -> Self {
        ValueData::Number(self.to_num() / other.to_num())
    }
}
impl Rem for ValueData {
    type Output = Self;
    fn rem(self, other: Self) -> Self {
        ValueData::Number(self.to_num() % other.to_num())
    }
}
impl BitAnd for ValueData {
    type Output = Self;
    fn bitand(self, other: Self) -> Self {
        ValueData::Integer(self.to_int() & other.to_int())
    }
}
impl BitOr for ValueData {
    type Output = Self;
    fn bitor(self, other: Self) -> Self {
        ValueData::Integer(self.to_int() | other.to_int())
    }
}
impl BitXor for ValueData {
    type Output = Self;
    fn bitxor(self, other: Self) -> Self {
        ValueData::Integer(self.to_int() ^ other.to_int())
    }
}
impl Shl for ValueData {
    type Output = Self;
    fn shl(self, other: Self) -> Self {
        ValueData::Integer(self.to_int() << other.to_int())
    }
}
impl Shr for ValueData {
    type Output = Self;
    fn shr(self, other: Self) -> Self {
        ValueData::Integer(self.to_int() >> other.to_int())
    }
}
impl Not for ValueData {
    type Output = Self;
    fn not(self) -> Self {
        ValueData::Boolean(!self.is_true())
    }
}

/// Conversion to Javascript values from Rust values
pub trait ToValue {
    /// Convert this value to a Rust value
    fn to_value(&self) -> Value;
}
/// Conversion to Rust values from Javascript values
pub trait FromValue {
    /// Convert this value to a Javascript value
    fn from_value(value: Value) -> Result<Self, &'static str>
    where
        Self: Sized;
}

impl ToValue for String {
    fn to_value(&self) -> Value {
        Gc::new(ValueData::String(self.clone()))
    }
}

impl FromValue for String {
    fn from_value(v: Value) -> Result<Self, &'static str> {
        Ok(v.to_string())
    }
}

impl<'s> ToValue for &'s str {
    fn to_value(&self) -> Value {
        Gc::new(ValueData::String(String::from_str(*self).unwrap()))
    }
}

impl ToValue for char {
    fn to_value(&self) -> Value {
        Gc::new(ValueData::String(self.to_string()))
    }
}
impl FromValue for char {
    fn from_value(v: Value) -> Result<Self, &'static str> {
        Ok(v.to_string().chars().next().unwrap())
    }
}

impl ToValue for f64 {
    fn to_value(&self) -> Value {
        Gc::new(ValueData::Number(*self))
    }
}
impl FromValue for f64 {
    fn from_value(v: Value) -> Result<Self, &'static str> {
        Ok(v.to_num())
    }
}

impl ToValue for i32 {
    fn to_value(&self) -> Value {
        Gc::new(ValueData::Integer(*self))
    }
}
impl FromValue for i32 {
    fn from_value(v: Value) -> Result<Self, &'static str> {
        Ok(v.to_int())
    }
}

impl ToValue for usize {
    fn to_value(&self) -> Value {
        Gc::new(ValueData::Integer(*self as i32))
    }
}
impl FromValue for usize {
    fn from_value(v: Value) -> Result<Self, &'static str> {
        Ok(v.to_int() as usize)
    }
}

impl ToValue for bool {
    fn to_value(&self) -> Value {
        Gc::new(ValueData::Boolean(*self))
    }
}
impl FromValue for bool {
    fn from_value(v: Value) -> Result<Self, &'static str> {
        Ok(v.is_true())
    }
}

impl<'s, T: ToValue> ToValue for &'s [T] {
    fn to_value(&self) -> Value {
        let mut arr = ObjectData::default();
        for (i, item) in self.iter().enumerate() {
            arr.properties
                .insert(i.to_string(), Property::new(item.to_value()));
        }
        to_value(arr)
    }
}
impl<T: ToValue> ToValue for Vec<T> {
    fn to_value(&self) -> Value {
        let mut arr = ObjectData::default();
        for (i, item) in self.iter().enumerate() {
            arr.properties
                .insert(i.to_string(), Property::new(item.to_value()));
        }
        to_value(arr)
    }
}

impl<T: FromValue> FromValue for Vec<T> {
    fn from_value(v: Value) -> Result<Self, &'static str> {
        let len = v.get_field_slice("length").to_int();
        let mut vec = Self::with_capacity(len as usize);
        for i in 0..len {
            vec.push(from_value(v.get_field(&i.to_string()))?)
        }
        Ok(vec)
    }
}

impl ToValue for ObjectData {
    fn to_value(&self) -> Value {
        Gc::new(ValueData::Object(GcCell::new(self.clone())))
    }
}

impl FromValue for ObjectData {
    fn from_value(v: Value) -> Result<Self, &'static str> {
        match *v {
            ValueData::Object(ref obj) => Ok(obj.clone().into_inner()),
            ValueData::Function(ref func) => Ok(match *func.borrow().deref() {
                Function::NativeFunc(ref data) => data.object.clone(),
                Function::RegularFunc(ref data) => data.object.clone(),
            }),
            _ => Err("Value is not a valid object"),
        }
    }
}

impl ToValue for JSONValue {
    fn to_value(&self) -> Value {
        Gc::new(ValueData::from_json(self.clone()))
    }
}

impl FromValue for JSONValue {
    fn from_value(v: Value) -> Result<Self, &'static str> {
        Ok(v.to_json())
    }
}

impl ToValue for () {
    fn to_value(&self) -> Value {
        Gc::new(ValueData::Null)
    }
}
impl FromValue for () {
    fn from_value(_: Value) -> Result<(), &'static str> {
        Ok(())
    }
}

impl<T: ToValue> ToValue for Option<T> {
    fn to_value(&self) -> Value {
        match *self {
            Some(ref v) => v.to_value(),
            None => Gc::new(ValueData::Null),
        }
    }
}
impl<T: FromValue> FromValue for Option<T> {
    fn from_value(value: Value) -> Result<Self, &'static str> {
        Ok(if value.is_null_or_undefined() {
            None
        } else {
            Some(FromValue::from_value(value)?)
        })
    }
}

impl ToValue for NativeFunctionData {
    fn to_value(&self) -> Value {
        Gc::new(ValueData::Function(Box::new(GcCell::new(
            Function::NativeFunc(NativeFunction::new(*self)),
        ))))
    }
}
impl FromValue for NativeFunctionData {
    fn from_value(v: Value) -> Result<Self, &'static str> {
        match *v {
            ValueData::Function(ref func) => match *func.borrow() {
                Function::NativeFunc(ref data) => Ok(data.data),
                _ => Err("Value is not a native function"),
            },
            _ => Err("Value is not a function"),
        }
    }
}

/// A utility function that just calls `FromValue::from_value`
pub fn from_value<A: FromValue>(v: Value) -> Result<A, &'static str> {
    FromValue::from_value(v)
}

/// A utility function that just calls `ToValue::to_value`
pub fn to_value<A: ToValue>(v: A) -> Value {
    v.to_value()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn check_is_object() {
        let val = ValueData::new_obj(None);
        assert_eq!(val.is_object(), true);
    }

    #[test]
    fn check_string_to_value() {
        let s = String::from("Hello");
        let v = s.to_value();
        assert_eq!(v.is_string(), true);
        assert_eq!(v.is_null(), false);
    }

    #[test]
    fn check_undefined() {
        let u = ValueData::Undefined;
        assert_eq!(u.get_type(), "undefined");
        assert_eq!(u.to_string(), "undefined");
    }

    #[test]
    fn check_get_set_field() {
        let obj = ValueData::new_obj(None);
        // Create string and convert it to a Value
        let s = String::from("bar").to_value();
        obj.set_field_slice("foo", s);
        assert_eq!(obj.get_field_slice("foo").to_string(), "bar");
    }

    #[test]
    fn check_integer_is_true() {
        assert_eq!(1.to_value().is_true(), true);
        assert_eq!(0.to_value().is_true(), false);
        assert_eq!((-1).to_value().is_true(), true);
    }

    #[test]
    fn check_number_is_true() {
        assert_eq!(1.0.to_value().is_true(), true);
        assert_eq!(0.1.to_value().is_true(), true);
        assert_eq!(0.0.to_value().is_true(), false);
        assert_eq!((-0.0).to_value().is_true(), false);
        assert_eq!((-1.0).to_value().is_true(), true);
        assert_eq!(NAN.to_value().is_true(), false);
    }

}