use libquickjs_ng_sys::{JSContext, JSValue};
use serde::{ser, Serialize};

use crate::utils::{
    create_bigint, create_bool, create_empty_array, create_empty_object, create_float, create_int,
    create_null, create_string, create_undefined, own_raw_value,
};
use crate::value::{OwnedJsArray, OwnedJsObject, OwnedJsValue};

use super::error::{Error, Result};

const MAX_SAFE_INTEGER: u64 = 9007199254740991;

/// A structure that serializes Rust values into JS values.
pub struct Serializer {
    context: *mut JSContext,
    root: OwnedJsValue,
    paths: Vec<OwnedJsValue>,
    current: Option<OwnedJsValue>,
    current_is_key: bool,
    current_key: Option<String>,
}

/// convert from rust type to OwnedJsValue
pub fn to_js<T>(context: *mut JSContext, value: &T) -> Result<OwnedJsValue>
where
    T: Serialize,
{
    let root = own_raw_value(context, create_undefined());
    let mut serializer = Serializer {
        context,
        root,
        paths: Vec::new(),
        current: None,
        current_is_key: false,
        current_key: None,
    };
    value.serialize(&mut serializer)?;

    Ok(serializer.root)
}

impl Serializer {
    #[inline]
    pub(self) fn set_node_value(&mut self, value: JSValue) -> Result<()> {
        // if current is None, then set root value
        if let Some(current) = self.current.as_mut() {
            if current.is_undefined() {
                current.replace(value);
            } else if current.is_array() {
                let current = OwnedJsArray::try_from_value(current.clone())?;
                current.push(OwnedJsValue::new(self.context, value))?;
            } else if current.is_object() {
                if let Some(key) = self.current_key.take() {
                    let current = OwnedJsObject::try_from_value(current.clone())?;
                    current.set_property(&key, OwnedJsValue::new(self.context, value))?;
                } else {
                    #[cfg(debug_assertions)]
                    {
                        let v = OwnedJsValue::new(self.context, value);
                        println!("tag: {:?}", v.tag());
                        println!("tag: {}", v.to_json_string(0)?);
                    }
                    return Err(Error::Message("current key is None".to_string()));
                }
            } else {
                #[cfg(debug_assertions)]
                {
                    println!("current tag: {:?}", current.tag());
                    println!("current value: {}", current.to_json_string(0)?);
                }
                return Err(Error::Message(
                    "current is not undefined, object or array.".to_string(),
                ));
            }
        } else {
            self.root.replace(value);
            // this only increase the ref count
            let current = self.root.clone();
            self.current = Some(current);
        }

        Ok(())
    }

    #[inline]
    pub(self) fn push_object(&mut self) -> Result<()> {
        let value = create_empty_object(self.context).unwrap();
        self.set_node_value(value)?;

        if let Some(current) = self.current.take() {
            self.paths.push(current);
        }

        self.current = Some(OwnedJsValue::own(self.context, &value));

        Ok(())
    }

    #[inline]
    pub(self) fn push_array(&mut self) -> Result<()> {
        let value = create_empty_array(self.context).unwrap();
        self.set_node_value(value)?;

        if let Some(current) = self.current.take() {
            self.paths.push(current);
        }

        self.current = Some(OwnedJsValue::own(self.context, &value));

        Ok(())
    }

    #[inline]
    pub(self) fn pop(&mut self) -> Result<()> {
        self.current = self.paths.pop();
        Ok(())
    }
}

impl<'a> ser::Serializer for &'a mut Serializer {
    // The output type produced by this `Serializer` during successful
    // serialization. Most serializers that produce text or binary output should
    // set `Ok = ()` and serialize into an `io::Write` or buffer contained
    // within the `Serializer` instance, as happens here. Serializers that build
    // in-memory data structures may be simplified by using `Ok` to propagate
    // the data structure around.
    type Ok = ();

    // The error type when some error occurs during serialization.
    type Error = Error;

    // Associated types for keeping track of additional state while serializing
    // compound data structures like sequences and maps. In this case no
    // additional state is required beyond what is already stored in the
    // Serializer struct.
    type SerializeSeq = Self;
    type SerializeTuple = Self;
    type SerializeTupleStruct = Self;
    type SerializeTupleVariant = Self;
    type SerializeMap = Self;
    type SerializeStruct = Self;
    type SerializeStructVariant = Self;

    // Here we go with the simple methods. The following 12 methods receive one
    // of the primitive types of the data model and map it to JSON by appending
    // into the output string.
    fn serialize_bool(self, v: bool) -> Result<()> {
        let value = create_bool(self.context, v);
        self.set_node_value(value)
    }

    // JSON does not distinguish between different sizes of integers, so all
    // signed integers will be serialized the same and all unsigned integers
    // will be serialized the same. Other formats, especially compact binary
    // formats, may need independent logic for the different sizes.
    fn serialize_i8(self, v: i8) -> Result<()> {
        self.serialize_i32(i32::from(v))
    }

    fn serialize_i16(self, v: i16) -> Result<()> {
        self.serialize_i32(i32::from(v))
    }

    fn serialize_i32(self, v: i32) -> Result<()> {
        let value = create_int(self.context, v as i32);
        self.set_node_value(value)
    }

    // Not particularly efficient but this is example code anyway. A more
    // performant approach would be to use the `itoa` crate.
    fn serialize_i64(self, v: i64) -> Result<()> {
        if v > MAX_SAFE_INTEGER as i64 {
            let value = create_bigint(self.context, (v as i64).into())?;
            self.set_node_value(value)
        } else if v > i32::MAX as i64 {
            let value = create_float(self.context, v as f64);
            self.set_node_value(value)
        } else {
            let value = create_int(self.context, v as i32);
            self.set_node_value(value)
        }
    }

    fn serialize_u8(self, v: u8) -> Result<()> {
        self.serialize_i32(i32::from(v))
    }

    fn serialize_u16(self, v: u16) -> Result<()> {
        self.serialize_i32(i32::from(v))
    }

    fn serialize_u32(self, v: u32) -> Result<()> {
        if v > i32::MAX as u32 {
            let value = create_float(self.context, v as f64);
            self.set_node_value(value)
        } else {
            let value = create_int(self.context, v as i32);
            self.set_node_value(value)
        }
    }

    fn serialize_u64(self, v: u64) -> Result<()> {
        if v > i64::MAX as u64 {
            let value = create_bigint(self.context, num_bigint::BigInt::from(v).into())?;
            self.set_node_value(value)
        } else if v > MAX_SAFE_INTEGER {
            let value = create_bigint(self.context, (v as i64).into())?;
            self.set_node_value(value)
        } else if v > i32::MAX as u64 {
            let value = create_float(self.context, v as f64);
            self.set_node_value(value)
        } else {
            let value = create_int(self.context, v as i32);
            self.set_node_value(value)
        }
    }

    fn serialize_f32(self, v: f32) -> Result<()> {
        self.serialize_f64(f64::from(v))
    }

    fn serialize_f64(self, v: f64) -> Result<()> {
        let value = create_float(self.context, v);
        self.set_node_value(value)
    }

    // Serialize a char as a single-character string. Other formats may
    // represent this differently.
    fn serialize_char(self, v: char) -> Result<()> {
        self.serialize_str(&v.to_string())
    }

    // This only works for strings that don't require escape sequences but you
    // get the idea. For example it would emit invalid JSON if the input string
    // contains a '"' character.
    fn serialize_str(self, v: &str) -> Result<()> {
        if self.current_is_key {
            self.current_key = Some(v.to_string());
            self.current_is_key = false;
            Ok(())
        } else {
            let value = create_string(self.context, v).unwrap();
            self.set_node_value(value)
        }
    }

    // Serialize a byte array as an array of bytes. Could also use a base64
    // string here. Binary formats will typically represent byte arrays more
    // compactly.
    fn serialize_bytes(self, v: &[u8]) -> Result<()> {
        use serde::ser::SerializeSeq;
        let mut seq = self.serialize_seq(Some(v.len()))?;
        for byte in v {
            seq.serialize_element(byte)?;
        }
        seq.end()
    }

    // An absent optional is represented as the JSON `null`.
    fn serialize_none(self) -> Result<()> {
        self.serialize_unit()
    }

    // A present optional is represented as just the contained value. Note that
    // this is a lossy representation. For example the values `Some(())` and
    // `None` both serialize as just `null`. Unfortunately this is typically
    // what people expect when working with JSON. Other formats are encouraged
    // to behave more intelligently if possible.
    fn serialize_some<T>(self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(self)
    }

    // In Serde, unit means an anonymous value containing no data. Map this to
    // JSON as `null`.
    fn serialize_unit(self) -> Result<()> {
        let value = create_null();
        self.set_node_value(value)
    }

    // Unit struct means a named value containing no data. Again, since there is
    // no data, map this to JSON as `null`. There is no need to serialize the
    // name in most formats.
    fn serialize_unit_struct(self, _name: &'static str) -> Result<()> {
        self.serialize_unit()
    }

    // When serializing a unit variant (or any other kind of variant), formats
    // can choose whether to keep track of it by index or by name. Binary
    // formats typically use the index of the variant and human-readable formats
    // typically use the name.
    fn serialize_unit_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
    ) -> Result<()> {
        self.serialize_str(variant)
    }

    // As is done here, serializers are encouraged to treat newtype structs as
    // insignificant wrappers around the data they contain.
    fn serialize_newtype_struct<T>(self, _name: &'static str, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(self)
    }

    // Note that newtype variant (and all of the other variant serialization
    // methods) refer exclusively to the "externally tagged" enum
    // representation.
    //
    // Serialize this to JSON in externally tagged form as `{ NAME: VALUE }`.
    fn serialize_newtype_variant<T>(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
        value: &T,
    ) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        self.push_object()?;

        self.current_is_key = true;
        variant.serialize(&mut *self)?;
        value.serialize(&mut *self)?;

        self.pop()?;

        Ok(())
    }

    // Now we get to the serialization of compound types.
    //
    // The start of the sequence, each value, and the end are three separate
    // method calls. This one is responsible only for serializing the start,
    // which in JSON is `[`.
    //
    // The length of the sequence may or may not be known ahead of time. This
    // doesn't make a difference in JSON because the length is not represented
    // explicitly in the serialized form. Some serializers may only be able to
    // support sequences for which the length is known up front.
    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq> {
        self.push_array()?;
        Ok(self)
    }

    // Tuples look just like sequences in JSON. Some formats may be able to
    // represent tuples more efficiently by omitting the length, since tuple
    // means that the corresponding `Deserialize implementation will know the
    // length without needing to look at the serialized data.
    fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple> {
        self.serialize_seq(Some(len))
    }

    // Tuple structs look just like sequences in JSON.
    fn serialize_tuple_struct(
        self,
        _name: &'static str,
        len: usize,
    ) -> Result<Self::SerializeTupleStruct> {
        self.serialize_seq(Some(len))
    }

    // Tuple variants are represented in JSON as `{ NAME: [DATA...] }`. Again
    // this method is only responsible for the externally tagged representation.
    fn serialize_tuple_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeTupleVariant> {
        self.push_object()?;
        self.current_is_key = true;
        variant.serialize(&mut *self)?;
        self.push_array()?;
        Ok(self)
    }

    // Maps are represented in JSON as `{ K: V, K: V, ... }`.
    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap> {
        self.push_object()?;
        Ok(self)
    }

    // Structs look just like maps in JSON. In particular, JSON requires that we
    // serialize the field names of the struct. Other formats may be able to
    // omit the field names when serializing structs because the corresponding
    // Deserialize implementation is required to know what the keys are without
    // looking at the serialized data.
    fn serialize_struct(self, _name: &'static str, len: usize) -> Result<Self::SerializeStruct> {
        self.serialize_map(Some(len))
    }

    // Struct variants are represented in JSON as `{ NAME: { K: V, ... } }`.
    // This is the externally tagged representation.
    fn serialize_struct_variant(
        self,
        _name: &'static str,
        _variant_index: u32,
        variant: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeStructVariant> {
        self.push_object()?;
        self.current_is_key = true;
        variant.serialize(&mut *self)?;
        self.push_object()?;

        Ok(self)
    }
}

// The following 7 impls deal with the serialization of compound types like
// sequences and maps. Serialization of such types is begun by a Serializer
// method and followed by zero or more calls to serialize individual elements of
// the compound type and one call to end the compound type.
//
// This impl is SerializeSeq so these methods are called after `serialize_seq`
// is called on the Serializer.
impl<'a> ser::SerializeSeq for &'a mut Serializer {
    // Must match the `Ok` type of the serializer.
    type Ok = ();
    // Must match the `Error` type of the serializer.
    type Error = Error;

    // Serialize a single element of the sequence.
    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(&mut **self)
    }

    // Close the sequence.
    fn end(self) -> Result<()> {
        self.pop()?;
        Ok(())
    }
}

// Same thing but for tuples.
impl<'a> ser::SerializeTuple for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.pop()?;
        Ok(())
    }
}

// Same thing but for tuple structs.
impl<'a> ser::SerializeTupleStruct for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.pop()?;
        Ok(())
    }
}

// Tuple variants are a little different. Refer back to the
// `serialize_tuple_variant` method above:
//
//    self.output += "{";
//    variant.serialize(&mut *self)?;
//    self.output += ":[";
//
// So the `end` method in this impl is responsible for closing both the `]` and
// the `}`.
impl<'a> ser::SerializeTupleVariant for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.pop()?;
        self.pop()?;
        Ok(())
    }
}

// Some `Serialize` types are not able to hold a key and value in memory at the
// same time so `SerializeMap` implementations are required to support
// `serialize_key` and `serialize_value` individually.
//
// There is a third optional method on the `SerializeMap` trait. The
// `serialize_entry` method allows serializers to optimize for the case where
// key and value are both available simultaneously. In JSON it doesn't make a
// difference so the default behavior for `serialize_entry` is fine.
impl<'a> ser::SerializeMap for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    // The Serde data model allows map keys to be any serializable type. JSON
    // only allows string keys so the implementation below will produce invalid
    // JSON if the key serializes as something other than a string.
    //
    // A real JSON serializer would need to validate that map keys are strings.
    // This can be done by using a different Serializer to serialize the key
    // (instead of `&mut **self`) and having that other serializer only
    // implement `serialize_str` and return an error on any other data type.
    fn serialize_key<T>(&mut self, key: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        if self.current_key.is_none() {
            self.current_is_key = true;
        } else {
            return Err(Error::Message(
                "Cannot serialize map with more than one key".to_string(),
            ));
        }

        key.serialize(&mut **self)
    }

    // It doesn't make a difference whether the colon is printed at the end of
    // `serialize_key` or at the beginning of `serialize_value`. In this case
    // the code is a bit simpler having it here.
    fn serialize_value<T>(&mut self, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.pop()?;
        Ok(())
    }
}

// Structs are like maps in which the keys are constrained to be compile-time
// constant strings.
impl<'a> ser::SerializeStruct for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        if self.current_key.is_none() {
            self.current_is_key = true;
        } else {
            return Err(Error::Message(
                "Cannot serialize map with more than one key".to_string(),
            ));
        }
        key.serialize(&mut **self)?;
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.pop()?;
        Ok(())
    }
}

// Similar to `SerializeTupleVariant`, here the `end` method is responsible for
// closing both of the curly braces opened by `serialize_struct_variant`.
impl<'a> ser::SerializeStructVariant for &'a mut Serializer {
    type Ok = ();
    type Error = Error;

    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
    where
        T: ?Sized + Serialize,
    {
        if self.current_key.is_none() {
            self.current_is_key = true;
        } else {
            return Err(Error::Message(
                "Cannot serialize map with more than one key".to_string(),
            ));
        }
        key.serialize(&mut **self)?;
        value.serialize(&mut **self)
    }

    fn end(self) -> Result<()> {
        self.pop()?;
        self.pop()?;
        Ok(())
    }
}

////////////////////////////////////////////////////////////////////////////////
