use crate::elements::*;
use crate::iter::*;
use crate::Error;

use alloc::string::ToString;
use core::result::Result as CoreResult;
use serde::de::{DeserializeSeed, Deserializer, IntoDeserializer, MapAccess, SeqAccess, Visitor};
use serde::forward_to_deserialize_any;

type Result<T> = CoreResult<T, Error>;

/// A deserializer for a ListInfo DAT.
pub struct DatDocumentDeserializer<'de> {
    iter: SliceIter<'de, EntryFragment<'de>>,
    value: Option<&'de [EntryFragment<'de>]>,
}

impl<'de> DatDocumentDeserializer<'de> {
    pub(crate) fn new(iter: SliceIter<'de, EntryFragment<'de>>) -> Self {
        DatDocumentDeserializer { iter, value: None }
    }

    /// Creates a DAT deserializer from a parsed document.
    pub fn from_document(doc: &'de DatDocument<'de>) -> Self {
        Self::new(doc.iter())
    }
}

impl<'de> MapAccess<'de> for DatDocumentDeserializer<'de> {
    type Error = Error;

    fn next_key_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
    where
        T: DeserializeSeed<'de>,
    {
        match self.iter.next() {
            Some((key, value)) => {
                self.value = Some(value);
                let key_de = key.into_deserializer();
                seed.deserialize(key_de).map(Some)
            }
            None => Ok(None),
        }
    }

    fn next_value_seed<T>(&mut self, seed: T) -> Result<T::Value>
    where
        T: DeserializeSeed<'de>,
    {
        match self.value.take() {
            Some(value) => seed.deserialize(FragmentSliceDeserializer::new(value)),
            None => Err(crate::Error::SerdeError("value is missing".to_string())),
        }
    }

    fn size_hint(&self) -> Option<usize> {
        match self.iter.size_hint() {
            (lower, Some(upper)) if lower == upper => Some(upper),
            _ => None,
        }
    }
}

type FragmentSliceIter<'a> = core::slice::Iter<'a, EntryFragment<'a>>;
struct FragmentSliceDeserializer<'a> {
    iter: FragmentSliceIter<'a>,
    item: &'a EntryFragment<'a>,
}

impl<'a> FragmentSliceDeserializer<'a> {
    pub(crate) fn new(n: &'a [EntryFragment<'a>]) -> Self {
        FragmentSliceDeserializer {
            iter: n.iter(),
            item: n.first().unwrap(),
        }
    }
}

impl<'de> SeqAccess<'de> for FragmentSliceDeserializer<'de> {
    type Error = crate::Error;

    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
    where
        T: DeserializeSeed<'de>,
    {
        match self.iter.next() {
            Some(fragment) => seed
                .deserialize(fragment.into_deserializer())
                .map(Some),
            None => Ok(None),
        }
    }

    fn size_hint(&self) -> Option<usize> {
        match self.iter.size_hint() {
            (lower, Some(upper)) if lower == upper => Some(upper),
            _ => None,
        }
    }
}

impl<'de> Deserializer<'de> for FragmentSliceDeserializer<'de> {
    type Error = crate::Error;

    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
    where
        V: Visitor<'de>,
    {
        self.deserialize_seq(visitor)
    }

    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value>
    where
        V: Visitor<'de>,
    {
        visitor.visit_seq(self)
    }

    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value>
    where
        V: Visitor<'de>,
    {
        visitor.visit_map(self.item.into_deserializer())
    }

    fn deserialize_struct<V>(
        self,
        _name: &'static str,
        _fields: &'static [&'static str],
        visitor: V,
    ) -> Result<V::Value>
    where
        V: Visitor<'de>,
    {
        self.deserialize_map(visitor)
    }

    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value>
    where
        V: Visitor<'de>,
    {
        visitor.visit_some(self)
    }

    fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value>
    where
        V: Visitor<'de>,
    {
        visitor.visit_unit()
    }

    fn deserialize_unit_struct<V>(self, _name: &'static str, visitor: V) -> Result<V::Value>
    where
        V: Visitor<'de>,
    {
        self.deserialize_unit(visitor)
    }

    fn deserialize_newtype_struct<V>(self, _name: &'static str, visitor: V) -> Result<V::Value>
    where
        V: Visitor<'de>,
    {
        visitor.visit_newtype_struct(self)
    }

    fn deserialize_tuple<V>(self, _len: usize, visitor: V) -> Result<V::Value>
    where
        V: Visitor<'de>,
    {
        self.deserialize_seq(visitor)
    }

    fn deserialize_tuple_struct<V>(
        self,
        _name: &'static str,
        _len: usize,
        visitor: V,
    ) -> Result<V::Value>
    where
        V: Visitor<'de>,
    {
        self.deserialize_seq(visitor)
    }

    forward_to_deserialize_any! {
        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
        bytes byte_buf enum identifier ignored_any
    }
}

impl<'de> Deserializer<'de> for DatDocumentDeserializer<'de> {
    type Error = crate::Error;

    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
    where
        V: Visitor<'de>,
    {
        visitor.visit_map(self)
    }

    forward_to_deserialize_any! {
        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
        bytes byte_buf option unit unit_struct newtype_struct seq tuple
        tuple_struct struct map enum identifier ignored_any
    }
}