use crate::array_default::ArrayDefault;
use crate::prelude::*;
use serde::de::Visitor;
use serde::ser::SerializeSeq;

use serde::{Deserialize, Deserializer, Serialize, Serializer};

impl<
        PRECISION: Precision + WordType<BITS>,
        const BITS: usize,
        const N: usize,
    > Serialize for HyperLogLogArray<PRECISION, BITS, N>
{
    #[inline(always)]
    /// Serializes the HyperLogLog counter using the given serializer.
    ///
    /// This method is part of the `Serialize` trait implementation for the HyperLogLog struct,
    /// allowing the counter to be serialized into a format supported by the serializer.
    ///
    /// # Arguments
    /// * `serializer`: The serializer used to serialize the HyperLogLog counter.
    ///
    /// # Returns
    /// The serialization result, indicating success or failure.
    ///
    /// # Example
    /// In this example, we serialize an array of HyperLogLog counters into a JSON string.
    /// The resulting string is then deserialized back into an array of HyperLogLog counters.
    ///
    /// Since we cannot implement these traits for array, we need to wrap the array in a struct,
    /// which in this case is `HyperLogLogArray`.
    ///
    /// ```rust
    /// use serde::Serialize;
    /// use serde_json::Serializer;
    /// use hyperloglog_rs::prelude::*;
    ///
    /// let mut hll_array = HyperLogLogArray::<Precision12, 6, 3>::new();
    /// hll_array[0].insert(&1);
    /// hll_array[1].insert(&2);
    /// hll_array[2].insert(&3);
    /// let mut serializer = Serializer::new(Vec::new());
    /// let result = hll_array.serialize(&mut serializer);
    /// assert!(result.is_ok(), "Serialization failed, error: {:?}", result.err());
    /// let hll_array_str = String::from_utf8(serializer.into_inner()).unwrap();
    /// let hll_array_deserialized = serde_json::from_str(&hll_array_str);
    /// assert!(hll_array_deserialized.is_ok(), "Deserialization failed, error: {:?}", hll_array_deserialized.err());
    /// let hll_array_deserialized = hll_array_deserialized.unwrap();
    /// assert_eq!(hll_array, hll_array_deserialized, "Deserialized array does not match original array");
    /// ```
    ///
    fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
        let mut seq = serializer.serialize_seq(Some(self.as_ref().len()))?;
        for counter in self.as_ref() {
            seq.serialize_element(&counter)?;
        }
        seq.end()
    }
}

impl<
        'de,
        PRECISION: Precision + WordType<BITS>,
        const BITS: usize,
        const N: usize,
    > Deserialize<'de> for HyperLogLogArray<PRECISION, BITS, N>
{
    #[inline(always)]
    /// Deserializes the HyperLogLog counter using the given deserializer.
    ///
    /// This method is part of the `Deserialize` trait implementation for the HyperLogLog struct,
    /// allowing the counter to be deserialized from a format supported by the deserializer.
    ///
    /// # Arguments
    /// * `deserializer`: The deserializer used to deserialize the HyperLogLog counter.
    ///
    /// # Returns
    /// The deserialization result, indicating success or failure.
    ///
    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
        Ok(Self::from(
            deserializer.deserialize_seq(HLLArrayVisitor::default())?,
        ))
    }
}

/// Struct to deserialize a vector of u32
pub struct HLLArrayVisitor<
    PRECISION: Precision + WordType<BITS>,
    const BITS: usize,
    const N: usize,
> {
    _precision: core::marker::PhantomData<PRECISION>,
}

impl<PRECISION: Precision + WordType<BITS>, const BITS: usize, const N: usize>
    HLLArrayVisitor<PRECISION, BITS, N>
{
    /// Creates a new HLLArrayVisitor
    pub fn new() -> Self {
        Self {
            _precision: core::marker::PhantomData,
        }
    }
}

impl<PRECISION: Precision + WordType<BITS>, const BITS: usize, const N: usize>
    Default for HLLArrayVisitor<PRECISION, BITS, N>
{
    fn default() -> Self {
        Self::new()
    }
}

/// A visitor implementation used for deserializing an array of HLL into a fixed-size array
///
/// This visitor is used internally by the `serde` deserialization process for the HyperLogLog struct.
/// It converts the deserialized sequence of HLL values into a fixed-size array.
///
/// # Generic Parameters
///
/// * `'de`: Lifetime specifier for the deserialization process.
/// * `PRECISION`: The precision parameter of the HyperLogLog counter.
/// * `BITS`: The number of bits used for each register in the HyperLogLog counter.
///
///
/// # Associated Types
///
/// * `Value`: The type of the resulting fixed-size array.
///
/// # Methods
///
/// ## expecting
///
/// Sets the error message for the expectation of an array of HLL.
///
/// ### Arguments
///
/// * `formatter`: A mutable reference to the formatter used to format the error message.
///
/// ### Returns
/// A `core::fmt::Result` indicating the success or failure of the formatting operation.
///
/// ## visit_seq
/// Processes the deserialized sequence and converts it into a fixed-size array of HLL values.
///
/// ### Arguments
/// * `seq`: The sequence access object used to iterate over the deserialized elements.
///
/// ### Returns
/// The resulting fixed-size array of u32 values, or an error if the deserialization failed.
impl<
        'de,
        PRECISION: Precision + WordType<BITS>,
        const BITS: usize,
        const N: usize,
    > Visitor<'de> for HLLArrayVisitor<PRECISION, BITS, N>
{
    type Value = [HyperLogLog<PRECISION, BITS>; N];

    fn expecting(&self, formatter: &mut core::fmt::Formatter) -> core::fmt::Result {
        formatter.write_str("an array of HLL")
    }

    fn visit_seq<A: serde::de::SeqAccess<'de>>(self, mut seq: A) -> Result<Self::Value, A::Error> {
        let mut hll_array = [HyperLogLog::new(); N];
        let mut hll_array_iter = hll_array.iter_mut();
        while let Some(value) = seq.next_element()? {
            if let Some(target) = hll_array_iter.next() {
                *target = value;
            } else {
                return Err(serde::de::Error::invalid_length(hll_array.len(), &self));
            }
        }
        Ok(hll_array)
    }
}

impl<PRECISION: Precision + WordType<BITS>, const BITS: usize> Serialize
    for HyperLogLog<PRECISION, BITS>
{
    #[inline(always)]
    /// Serializes the HyperLogLog counter using the given serializer.
    ///
    /// This method is part of the `Serialize` trait implementation for the HyperLogLog struct,
    /// allowing the counter to be serialized into a format supported by the serializer.
    ///
    /// # Arguments
    /// * `serializer`: The serializer used to serialize the HyperLogLog counter.
    ///
    /// # Returns
    /// The serialization result, indicating success or failure.
    ///
    /// # Example
    ///
    /// ```
    /// use serde::Serialize;
    /// use serde_json::Serializer;
    /// use hyperloglog_rs::prelude::*;
    ///
    /// let hll = HyperLogLog::<Precision12, 6>::new();
    /// let mut serializer = Serializer::new(Vec::new());
    /// let result = hll.serialize(&mut serializer);
    /// assert!(result.is_ok(), "Serialization failed, error: {:?}", result.err());
    /// ```
    fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
        let mut seq = serializer.serialize_seq(Some(self.words.len()))?;
        for word in self.words.iter_elements() {
            seq.serialize_element(word)?;
        }
        seq.end()
    }
}

impl<'de, PRECISION: Precision + WordType<BITS>, const BITS: usize>
    Deserialize<'de> for HyperLogLog<PRECISION, BITS>
{
    #[inline(always)]
    /// Deserializes the HyperLogLog counter using the given deserializer.
    ///
    /// This method is part of the `Deserialize` trait implementation for the HyperLogLog struct,
    /// allowing the counter to be deserialized from a format supported by the deserializer.
    ///
    /// # Arguments
    /// * `deserializer`: The deserializer used to deserialize the HyperLogLog counter.
    ///
    /// # Returns
    /// The deserialization result, indicating success or failure.
    ///
    /// # Example
    ///
    /// ```
    /// use serde::de::Deserialize;
    /// use serde_json::Deserializer;
    /// use hyperloglog_rs::prelude::*;
    ///
    /// let words = [0, 0, 0, 0, 5, 0, 4, 0, 0, 3, 0, 0, 0];
    /// let words_str = "[0, 0, 0, 0, 5, 0, 4, 0, 0, 3, 0, 0, 0]";
    /// let mut deserializer = Deserializer::from_str(words_str);
    /// let result = HyperLogLog::<Precision6, 6>::deserialize(&mut deserializer);
    /// assert!(result.is_ok(), "Deserialization failed, error: {:?}", result.err());
    /// let hll = result.unwrap();
    /// hll.get_words().iter().zip(words.iter()).for_each(|(a, b)| assert_eq!(a, b, "Deserialized words do not match, expected: {}, actual: {}", b, a));
    /// ```
    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
        let words: PRECISION::Words =
            deserializer.deserialize_seq(WordsVisitor::<PRECISION, BITS>::default())?;

        Ok(Self::from_words(&words))
    }
}

#[derive(Default)]
/// Struct to deserialize a vector of u32
pub struct WordsVisitor<PRECISION: Precision + WordType<BITS>, const BITS: usize> {
    _precision: core::marker::PhantomData<PRECISION>,
}

/// A visitor implementation used for deserializing an array of u32 into a fixed-size array.
///
/// This visitor is used internally by the `serde` deserialization process for the HyperLogLog struct.
/// It converts the deserialized sequence of u32 values into a fixed-size array.
///
/// # Generic Parameters
///
/// * `'de`: Lifetime specifier for the deserialization process.
/// * `PRECISION`: The precision parameter of the HyperLogLog counter.
/// * `BITS`: The number of bits used for each register in the HyperLogLog counter.
///
/// # Associated Types
///
/// * `Value`: The type of the resulting fixed-size array.
///
/// # Methods
///
/// ## expecting
///
/// Sets the error message for the expectation of an array of u32.
///
/// ### Arguments
///
/// * `formatter`: A mutable reference to the formatter used to format the error message.
///
/// ### Returns
/// A `core::fmt::Result` indicating the success or failure of the formatting operation.
///
/// ## visit_seq
/// Processes the deserialized sequence and converts it into a fixed-size array of u32 values.
///
/// ### Arguments
/// * `seq`: The sequence access object used to iterate over the deserialized elements.
///
/// ### Returns
/// The resulting fixed-size array of u32 values, or an error if the deserialization failed.
impl<'de, PRECISION: Precision + WordType<BITS>, const BITS: usize> Visitor<'de>
    for WordsVisitor<PRECISION, BITS>
{
    type Value = PRECISION::Words;

    fn expecting(&self, formatter: &mut core::fmt::Formatter) -> core::fmt::Result {
        formatter.write_str("a tuple with an array of u32 and a u32 scalar")
    }

    fn visit_seq<A: serde::de::SeqAccess<'de>>(self, mut seq: A) -> Result<Self::Value, A::Error> {
        let mut words_array = PRECISION::Words::default_array();
        let number_of_elements = words_array.len();
        {
            let mut words_array_iter = words_array.iter_elements_mut();
            while let Some(value) = seq.next_element()? {
                if let Some(target) = words_array_iter.next() {
                    *target = value;
                } else {
                    return Err(serde::de::Error::invalid_length(number_of_elements, &self));
                }
            }
        }
        Ok(words_array)
    }
}