//! Default AVM2 object impl

use crate::avm2::function::{Avm2ClassEntry, Executable};
use crate::avm2::names::{Namespace, QName};
use crate::avm2::object::{Object, ObjectPtr, TObject};
use crate::avm2::property::Property;
use crate::avm2::return_value::ReturnValue;
use crate::avm2::scope::Scope;
use crate::avm2::slot::Slot;
use crate::avm2::value::Value;
use crate::avm2::{Avm2, Error};
use crate::context::UpdateContext;
use gc_arena::{Collect, GcCell, MutationContext};
use std::collections::HashMap;
use std::fmt::Debug;
use std::rc::Rc;
use swf::avm2::types::{AbcFile, Trait as AbcTrait, TraitKind as AbcTraitKind};

/// Default implementation of `avm2::Object`.
#[derive(Clone, Collect, Debug, Copy)]
#[collect(no_drop)]
pub struct ScriptObject<'gc>(GcCell<'gc, ScriptObjectData<'gc>>);

/// Information necessary for a script object to have a class attached to it.
///
/// Classes can be attached to a `ScriptObject` such that the class's traits
/// are instantiated on-demand. Either class or instance traits can be
/// instantiated.
///
/// Trait instantiation obeys prototyping rules: prototypes provide their
/// instances with classes to pull traits from.
#[derive(Clone, Collect, Debug)]
#[collect(no_drop)]
pub enum ScriptObjectClass<'gc> {
    /// Instantiate instance traits, for prototypes.
    InstancePrototype(Avm2ClassEntry, Option<GcCell<'gc, Scope<'gc>>>),

    /// Instantiate class traits, for class constructors.
    ClassConstructor(Avm2ClassEntry, Option<GcCell<'gc, Scope<'gc>>>),

    /// Do not instantiate any class or instance traits.
    NoClass,
}

/// Base data common to all `TObject` implementations.
///
/// Host implementations of `TObject` should embed `ScriptObjectData` and
/// forward any trait method implementations it does not overwrite to this
/// struct.
#[derive(Clone, Collect, Debug)]
#[collect(no_drop)]
pub struct ScriptObjectData<'gc> {
    /// Properties stored on this object.
    values: HashMap<QName, Property<'gc>>,

    /// Slots stored on this object.
    slots: Vec<Slot<'gc>>,

    /// Methods stored on this object.
    methods: Vec<Option<Object<'gc>>>,

    /// Implicit prototype of this script object.
    proto: Option<Object<'gc>>,

    /// The class that this script object represents.
    class: ScriptObjectClass<'gc>,

    /// Enumeratable property names.
    enumerants: Vec<QName>,
}

impl<'gc> TObject<'gc> for ScriptObject<'gc> {
    fn get_property_local(
        self,
        reciever: Object<'gc>,
        name: &QName,
        avm: &mut Avm2<'gc>,
        context: &mut UpdateContext<'_, 'gc, '_>,
    ) -> Result<ReturnValue<'gc>, Error> {
        self.0
            .read()
            .get_property_local(reciever, name, avm, context)
    }

    fn set_property_local(
        self,
        reciever: Object<'gc>,
        name: &QName,
        value: Value<'gc>,
        avm: &mut Avm2<'gc>,
        context: &mut UpdateContext<'_, 'gc, '_>,
    ) -> Result<ReturnValue<'gc>, Error> {
        self.0
            .write(context.gc_context)
            .set_property_local(reciever, name, value, avm, context)
    }

    fn init_property_local(
        self,
        reciever: Object<'gc>,
        name: &QName,
        value: Value<'gc>,
        avm: &mut Avm2<'gc>,
        context: &mut UpdateContext<'_, 'gc, '_>,
    ) -> Result<ReturnValue<'gc>, Error> {
        self.0
            .write(context.gc_context)
            .init_property_local(reciever, name, value, avm, context)
    }

    fn is_property_overwritable(self, gc_context: MutationContext<'gc, '_>, name: &QName) -> bool {
        self.0.write(gc_context).is_property_overwritable(name)
    }

    fn delete_property(&self, gc_context: MutationContext<'gc, '_>, name: &QName) -> bool {
        self.0.write(gc_context).delete_property(name)
    }

    fn get_slot(self, id: u32) -> Result<Value<'gc>, Error> {
        self.0.read().get_slot(id)
    }

    fn set_slot(
        self,
        id: u32,
        value: Value<'gc>,
        mc: MutationContext<'gc, '_>,
    ) -> Result<(), Error> {
        self.0.write(mc).set_slot(id, value, mc)
    }

    fn init_slot(
        self,
        id: u32,
        value: Value<'gc>,
        mc: MutationContext<'gc, '_>,
    ) -> Result<(), Error> {
        self.0.write(mc).init_slot(id, value, mc)
    }

    fn get_method(self, id: u32) -> Option<Object<'gc>> {
        self.0.read().get_method(id)
    }

    fn get_trait(self, name: &QName) -> Result<Vec<AbcTrait>, Error> {
        self.0.read().get_trait(name)
    }

    fn get_scope(self) -> Option<GcCell<'gc, Scope<'gc>>> {
        self.0.read().get_scope()
    }

    fn get_abc(self) -> Option<Rc<AbcFile>> {
        self.0.read().get_abc()
    }

    fn resolve_any(self, local_name: &str) -> Option<Namespace> {
        self.0.read().resolve_any(local_name)
    }

    fn has_own_property(self, name: &QName) -> Result<bool, Error> {
        self.0.read().has_own_property(name)
    }

    fn has_trait(self, name: &QName) -> Result<bool, Error> {
        self.0.read().has_trait(name)
    }

    fn has_own_trait(self, name: &QName) -> Result<bool, Error> {
        self.0.read().has_own_trait(name)
    }

    fn has_instantiated_property(self, name: &QName) -> bool {
        self.0.read().has_instantiated_property(name)
    }

    fn has_own_virtual_getter(self, name: &QName) -> bool {
        self.0.read().has_own_virtual_getter(name)
    }

    fn has_own_virtual_setter(self, name: &QName) -> bool {
        self.0.read().has_own_virtual_setter(name)
    }

    fn proto(&self) -> Option<Object<'gc>> {
        self.0.read().proto
    }

    fn get_enumerant_name(&self, index: u32) -> Option<QName> {
        self.0.read().get_enumerant_name(index)
    }

    fn as_ptr(&self) -> *const ObjectPtr {
        self.0.as_ptr() as *const ObjectPtr
    }

    fn construct(
        &self,
        _avm: &mut Avm2<'gc>,
        context: &mut UpdateContext<'_, 'gc, '_>,
        _args: &[Value<'gc>],
    ) -> Result<Object<'gc>, Error> {
        let this: Object<'gc> = Object::ScriptObject(*self);
        Ok(ScriptObject::object(context.gc_context, this))
    }

    fn derive(
        &self,
        _avm: &mut Avm2<'gc>,
        context: &mut UpdateContext<'_, 'gc, '_>,
        class: Avm2ClassEntry,
        scope: Option<GcCell<'gc, Scope<'gc>>>,
    ) -> Result<Object<'gc>, Error> {
        let this: Object<'gc> = Object::ScriptObject(*self);
        Ok(ScriptObject::prototype(
            context.gc_context,
            this,
            class,
            scope,
        ))
    }

    fn install_method(
        &mut self,
        mc: MutationContext<'gc, '_>,
        name: QName,
        disp_id: u32,
        function: Object<'gc>,
    ) {
        self.0.write(mc).install_method(name, disp_id, function)
    }

    fn install_getter(
        &mut self,
        mc: MutationContext<'gc, '_>,
        name: QName,
        disp_id: u32,
        function: Object<'gc>,
    ) -> Result<(), Error> {
        self.0.write(mc).install_getter(name, disp_id, function)
    }

    fn install_setter(
        &mut self,
        mc: MutationContext<'gc, '_>,
        name: QName,
        disp_id: u32,
        function: Object<'gc>,
    ) -> Result<(), Error> {
        self.0.write(mc).install_setter(name, disp_id, function)
    }

    fn install_dynamic_property(
        &mut self,
        mc: MutationContext<'gc, '_>,
        name: QName,
        value: Value<'gc>,
    ) -> Result<(), Error> {
        self.0.write(mc).install_dynamic_property(name, value)
    }

    fn install_slot(
        &mut self,
        mc: MutationContext<'gc, '_>,
        name: QName,
        id: u32,
        value: Value<'gc>,
    ) {
        self.0.write(mc).install_slot(name, id, value)
    }

    fn install_const(
        &mut self,
        mc: MutationContext<'gc, '_>,
        name: QName,
        id: u32,
        value: Value<'gc>,
    ) {
        self.0.write(mc).install_const(name, id, value)
    }
}

impl<'gc> ScriptObject<'gc> {
    /// Construct a bare object with no base class.
    ///
    /// This is *not* the same thing as an object literal, which actually does
    /// have a base class: `Object`.
    pub fn bare_object(mc: MutationContext<'gc, '_>) -> Object<'gc> {
        ScriptObject(GcCell::allocate(
            mc,
            ScriptObjectData::base_new(None, ScriptObjectClass::NoClass),
        ))
        .into()
    }

    /// Construct an object with a prototype.
    pub fn object(mc: MutationContext<'gc, '_>, proto: Object<'gc>) -> Object<'gc> {
        ScriptObject(GcCell::allocate(
            mc,
            ScriptObjectData::base_new(Some(proto), ScriptObjectClass::NoClass),
        ))
        .into()
    }

    /// Construct a prototype for an ES4 class.
    pub fn prototype(
        mc: MutationContext<'gc, '_>,
        proto: Object<'gc>,
        class: Avm2ClassEntry,
        scope: Option<GcCell<'gc, Scope<'gc>>>,
    ) -> Object<'gc> {
        let script_class = ScriptObjectClass::InstancePrototype(class, scope);

        ScriptObject(GcCell::allocate(
            mc,
            ScriptObjectData::base_new(Some(proto), script_class),
        ))
        .into()
    }
}

/// Given a list of traits from an ABC file, find the one that matches this
/// name.
///
/// This function adds it's result onto the list of known traits, with the
/// caveat that duplicate entries will be replaced (if allowed). As such, this
/// function should be run on the class hierarchy from top to bottom.
///
/// If a given trait has an invalid name, attempts to override a final trait,
/// or overlaps an existing trait without being an override, then this function
/// returns an error.
///
/// TODO: This is an O(n^2) algorithm, it sucks.
fn do_trait_lookup(
    name: &QName,
    known_traits: &mut Vec<AbcTrait>,
    abc: Rc<AbcFile>,
    traits: &[AbcTrait],
) -> Result<(), Error> {
    for trait_entry in traits.iter() {
        let trait_name = QName::from_abc_multiname(&abc, trait_entry.name.clone())?;

        if name == &trait_name {
            for known_trait in known_traits.iter() {
                match (&trait_entry.kind, &known_trait.kind) {
                    (AbcTraitKind::Getter { .. }, AbcTraitKind::Setter { .. }) => continue,
                    (AbcTraitKind::Setter { .. }, AbcTraitKind::Getter { .. }) => continue,
                    _ => {}
                };

                if known_trait.is_final {
                    return Err("Attempting to override a final definition".into());
                }

                if !trait_entry.is_override {
                    return Err("Definition override is not marked as override".into());
                }
            }

            known_traits.push(trait_entry.clone());
        }
    }

    Ok(())
}

impl<'gc> ScriptObjectData<'gc> {
    pub fn base_new(proto: Option<Object<'gc>>, trait_source: ScriptObjectClass<'gc>) -> Self {
        ScriptObjectData {
            values: HashMap::new(),
            slots: Vec::new(),
            methods: Vec::new(),
            proto,
            class: trait_source,
            enumerants: Vec::new(),
        }
    }

    pub fn get_property_local(
        &self,
        reciever: Object<'gc>,
        name: &QName,
        avm: &mut Avm2<'gc>,
        context: &mut UpdateContext<'_, 'gc, '_>,
    ) -> Result<ReturnValue<'gc>, Error> {
        let prop = self.values.get(name);

        if let Some(prop) = prop {
            prop.get(
                avm,
                context,
                reciever,
                avm.current_stack_frame()
                    .and_then(|sf| sf.read().base_proto())
                    .or(self.proto),
            )
        } else {
            Ok(Value::Undefined.into())
        }
    }

    pub fn set_property_local(
        &mut self,
        reciever: Object<'gc>,
        name: &QName,
        value: Value<'gc>,
        avm: &mut Avm2<'gc>,
        context: &mut UpdateContext<'_, 'gc, '_>,
    ) -> Result<ReturnValue<'gc>, Error> {
        if let Some(prop) = self.values.get_mut(name) {
            if let Some(slot_id) = prop.slot_id() {
                self.set_slot(slot_id, value, context.gc_context)?;
                Ok(Value::Undefined.into())
            } else {
                let proto = self.proto;
                prop.set(
                    avm,
                    context,
                    reciever,
                    avm.current_stack_frame()
                        .and_then(|sf| sf.read().base_proto())
                        .or(proto),
                    value,
                )
            }
        } else {
            //TODO: Not all classes are dynamic like this
            self.enumerants.push(name.clone());
            self.values
                .insert(name.clone(), Property::new_dynamic_property(value));

            Ok(Value::Undefined.into())
        }
    }

    pub fn init_property_local(
        &mut self,
        reciever: Object<'gc>,
        name: &QName,
        value: Value<'gc>,
        avm: &mut Avm2<'gc>,
        context: &mut UpdateContext<'_, 'gc, '_>,
    ) -> Result<ReturnValue<'gc>, Error> {
        if let Some(prop) = self.values.get_mut(name) {
            if let Some(slot_id) = prop.slot_id() {
                self.init_slot(slot_id, value, context.gc_context)?;
                Ok(Value::Undefined.into())
            } else {
                let proto = self.proto;
                prop.init(
                    avm,
                    context,
                    reciever,
                    avm.current_stack_frame()
                        .and_then(|sf| sf.read().base_proto())
                        .or(proto),
                    value,
                )
            }
        } else {
            //TODO: Not all classes are dynamic like this
            self.values
                .insert(name.clone(), Property::new_dynamic_property(value));

            Ok(Value::Undefined.into())
        }
    }

    pub fn is_property_overwritable(&self, name: &QName) -> bool {
        self.values
            .get(name)
            .map(|p| p.is_overwritable())
            .unwrap_or(true)
    }

    pub fn delete_property(&mut self, name: &QName) -> bool {
        let can_delete = if let Some(prop) = self.values.get(name) {
            prop.can_delete()
        } else {
            false
        };

        if can_delete {
            self.values.remove(name);
        }

        can_delete
    }

    pub fn get_slot(&self, id: u32) -> Result<Value<'gc>, Error> {
        //TODO: slot inheritance, I think?
        self.slots
            .get(id as usize)
            .cloned()
            .ok_or_else(|| format!("Slot index {} out of bounds!", id).into())
            .map(|slot| slot.get().unwrap_or(Value::Undefined))
    }

    /// Set a slot by it's index.
    pub fn set_slot(
        &mut self,
        id: u32,
        value: Value<'gc>,
        _mc: MutationContext<'gc, '_>,
    ) -> Result<(), Error> {
        if let Some(slot) = self.slots.get_mut(id as usize) {
            slot.set(value)
        } else {
            Err(format!("Slot index {} out of bounds!", id).into())
        }
    }

    /// Set a slot by it's index.
    pub fn init_slot(
        &mut self,
        id: u32,
        value: Value<'gc>,
        _mc: MutationContext<'gc, '_>,
    ) -> Result<(), Error> {
        if let Some(slot) = self.slots.get_mut(id as usize) {
            slot.init(value)
        } else {
            Err(format!("Slot index {} out of bounds!", id).into())
        }
    }

    /// Retrieve a method from the method table.
    pub fn get_method(&self, id: u32) -> Option<Object<'gc>> {
        self.methods.get(id as usize).and_then(|v| *v)
    }

    pub fn get_trait(&self, name: &QName) -> Result<Vec<AbcTrait>, Error> {
        let mut known_traits = if let Some(proto) = self.proto {
            proto.get_trait(name)?
        } else {
            vec![]
        };

        match &self.class {
            ScriptObjectClass::ClassConstructor(class, ..) => {
                do_trait_lookup(name, &mut known_traits, class.abc(), &class.class().traits)?
            }
            ScriptObjectClass::InstancePrototype(class, ..) => do_trait_lookup(
                name,
                &mut known_traits,
                class.abc(),
                &class.instance().traits,
            )?,
            ScriptObjectClass::NoClass => {}
        };

        Ok(known_traits)
    }

    pub fn has_trait(&self, name: &QName) -> Result<bool, Error> {
        if let Some(proto) = self.proto {
            if proto.has_trait(name)? {
                return Ok(true);
            }
        }

        self.has_own_trait(name)
    }

    pub fn has_own_trait(&self, name: &QName) -> Result<bool, Error> {
        match &self.class {
            ScriptObjectClass::ClassConstructor(class, ..) => {
                for trait_entry in class.class().traits.iter() {
                    let trait_name =
                        QName::from_abc_multiname(&class.abc(), trait_entry.name.clone())?;

                    if name == &trait_name {
                        return Ok(true);
                    }
                }
            }
            ScriptObjectClass::InstancePrototype(class, ..) => {
                for trait_entry in class.instance().traits.iter() {
                    let trait_name =
                        QName::from_abc_multiname(&class.abc(), trait_entry.name.clone())?;

                    if name == &trait_name {
                        return Ok(true);
                    }
                }
            }
            ScriptObjectClass::NoClass => {}
        };

        Ok(false)
    }

    pub fn get_scope(&self) -> Option<GcCell<'gc, Scope<'gc>>> {
        match &self.class {
            ScriptObjectClass::ClassConstructor(_class, scope) => *scope,
            ScriptObjectClass::InstancePrototype(_class, scope) => *scope,
            ScriptObjectClass::NoClass => self.proto().and_then(|proto| proto.get_scope()),
        }
    }

    pub fn get_abc(&self) -> Option<Rc<AbcFile>> {
        match &self.class {
            ScriptObjectClass::ClassConstructor(class, ..) => Some(class.abc()),
            ScriptObjectClass::InstancePrototype(class, ..) => Some(class.abc()),
            ScriptObjectClass::NoClass => self.proto().and_then(|proto| proto.get_abc()),
        }
    }

    pub fn resolve_any(&self, local_name: &str) -> Option<Namespace> {
        for (key, _value) in self.values.iter() {
            if key.local_name() == local_name {
                return Some(key.namespace().clone());
            }
        }

        None
    }

    pub fn has_own_property(&self, name: &QName) -> Result<bool, Error> {
        Ok(self.values.get(name).is_some() || self.has_trait(name)?)
    }

    pub fn has_instantiated_property(&self, name: &QName) -> bool {
        self.values.get(name).is_some()
    }

    pub fn has_own_virtual_getter(&self, name: &QName) -> bool {
        match self.values.get(name) {
            Some(Property::Virtual { get: Some(_), .. }) => true,
            _ => false,
        }
    }

    pub fn has_own_virtual_setter(&self, name: &QName) -> bool {
        match self.values.get(name) {
            Some(Property::Virtual { set: Some(_), .. }) => true,
            _ => false,
        }
    }

    pub fn proto(&self) -> Option<Object<'gc>> {
        self.proto
    }

    pub fn get_enumerant_name(&self, index: u32) -> Option<QName> {
        // NOTE: AVM2 object enumeration is one of the weakest parts of an
        // otherwise well-designed VM. Notably, because of the way they
        // implemented `hasnext` and `hasnext2`, all enumerants start from ONE.
        // Hence why we have to `checked_sub` here in case some miscompiled
        // code doesn't check for the zero index, which is actually a failure
        // sentinel.
        let true_index = (index as usize).checked_sub(1)?;

        self.enumerants.get(true_index).cloned()
    }

    /// Install a method into the object.
    pub fn install_method(&mut self, name: QName, disp_id: u32, function: Object<'gc>) {
        if disp_id > 0 {
            if self.methods.len() <= disp_id as usize {
                self.methods
                    .resize_with(disp_id as usize + 1, Default::default);
            }

            *self.methods.get_mut(disp_id as usize).unwrap() = Some(function);
        }

        self.values.insert(name, Property::new_method(function));
    }

    /// Install a getter into the object.
    ///
    /// This is a little more complicated than methods, since virtual property
    /// slots can be installed in two parts. Thus, we need to support
    /// installing them in either order.
    pub fn install_getter(
        &mut self,
        name: QName,
        disp_id: u32,
        function: Object<'gc>,
    ) -> Result<(), Error> {
        let executable: Result<Executable<'gc>, Error> = function
            .as_executable()
            .ok_or_else(|| "Attempted to install getter without a valid method".into());
        let executable = executable?;

        if disp_id > 0 {
            if self.methods.len() <= disp_id as usize {
                self.methods
                    .resize_with(disp_id as usize + 1, Default::default);
            }

            *self.methods.get_mut(disp_id as usize).unwrap() = Some(function);
        }

        if !self.values.contains_key(&name) {
            self.values.insert(name.clone(), Property::new_virtual());
        }

        self.values
            .get_mut(&name)
            .unwrap()
            .install_virtual_getter(executable)
    }

    /// Install a setter into the object.
    ///
    /// This is a little more complicated than methods, since virtual property
    /// slots can be installed in two parts. Thus, we need to support
    /// installing them in either order.
    pub fn install_setter(
        &mut self,
        name: QName,
        disp_id: u32,
        function: Object<'gc>,
    ) -> Result<(), Error> {
        let executable: Result<Executable<'gc>, Error> = function
            .as_executable()
            .ok_or_else(|| "Attempted to install setter without a valid method".into());
        let executable = executable?;

        if disp_id > 0 {
            if self.methods.len() <= disp_id as usize {
                self.methods
                    .resize_with(disp_id as usize + 1, Default::default);
            }

            *self.methods.get_mut(disp_id as usize).unwrap() = Some(function);
        }

        if !self.values.contains_key(&name) {
            self.values.insert(name.clone(), Property::new_virtual());
        }

        self.values
            .get_mut(&name)
            .unwrap()
            .install_virtual_setter(executable)
    }

    pub fn install_dynamic_property(
        &mut self,
        name: QName,
        value: Value<'gc>,
    ) -> Result<(), Error> {
        self.values
            .insert(name, Property::new_dynamic_property(value));

        Ok(())
    }

    /// Install a slot onto the object.
    ///
    /// Slot number zero indicates a slot ID that is unknown and should be
    /// allocated by the VM - as far as I know, there is no way to discover
    /// slot IDs, so we don't allocate a slot for them at all.
    pub fn install_slot(&mut self, name: QName, id: u32, value: Value<'gc>) {
        if id == 0 {
            self.values.insert(name, Property::new_stored(value));
        } else {
            self.values.insert(name, Property::new_slot(id));
            if self.slots.len() < id as usize + 1 {
                self.slots.resize_with(id as usize + 1, Default::default);
            }

            if let Some(slot) = self.slots.get_mut(id as usize) {
                *slot = Slot::new(value);
            }
        }
    }

    /// Install a const onto the object.
    ///
    /// Slot number zero indicates a slot ID that is unknown and should be
    /// allocated by the VM - as far as I know, there is no way to discover
    /// slot IDs, so we don't allocate a slot for them at all.
    pub fn install_const(&mut self, name: QName, id: u32, value: Value<'gc>) {
        if id == 0 {
            self.values.insert(name, Property::new_const(value));
        } else {
            self.values.insert(name, Property::new_slot(id));
            if self.slots.len() < id as usize + 1 {
                self.slots.resize_with(id as usize + 1, Default::default);
            }

            if let Some(slot) = self.slots.get_mut(id as usize) {
                *slot = Slot::new_const(value);
            }
        }
    }
}