#![allow(unused_variables)]

use crate::schema;
use microrm::prelude::*;

use super::Config;

struct ValueToStringSerializer {}

impl<'l> serde::Serializer for &'l ValueToStringSerializer {
    type Ok = Option<String>;
    type Error = ConfigError;

    type SerializeSeq = serde::ser::Impossible<Self::Ok, Self::Error>;
    type SerializeMap = serde::ser::Impossible<Self::Ok, Self::Error>;
    type SerializeTuple = serde::ser::Impossible<Self::Ok, Self::Error>;
    type SerializeStruct = serde::ser::Impossible<Self::Ok, Self::Error>;
    type SerializeTupleStruct = serde::ser::Impossible<Self::Ok, Self::Error>;
    type SerializeTupleVariant = serde::ser::Impossible<Self::Ok, Self::Error>;
    type SerializeStructVariant = serde::ser::Impossible<Self::Ok, Self::Error>;

    fn serialize_bool(self, v: bool) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_i8(self, v: i8) -> Result<Self::Ok, Self::Error> {
        self.serialize_i64(v as i64)
    }
    fn serialize_i16(self, v: i16) -> Result<Self::Ok, Self::Error> {
        self.serialize_i64(v as i64)
    }
    fn serialize_i32(self, v: i32) -> Result<Self::Ok, Self::Error> {
        self.serialize_i64(v as i64)
    }
    fn serialize_i64(self, v: i64) -> Result<Self::Ok, Self::Error> {
        Ok(Some(v.to_string()))
    }
    fn serialize_i128(self, v: i128) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_u8(self, v: u8) -> Result<Self::Ok, Self::Error> {
        self.serialize_u64(v as u64)
    }
    fn serialize_u16(self, v: u16) -> Result<Self::Ok, Self::Error> {
        self.serialize_u64(v as u64)
    }
    fn serialize_u32(self, v: u32) -> Result<Self::Ok, Self::Error> {
        self.serialize_u64(v as u64)
    }
    fn serialize_u64(self, v: u64) -> Result<Self::Ok, Self::Error> {
        Ok(Some(v.to_string()))
    }
    fn serialize_u128(self, v: u128) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_f32(self, v: f32) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }
    fn serialize_f64(self, v: f64) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_char(self, v: char) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_bytes(self, v: &[u8]) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_str(self, v: &str) -> Result<Self::Ok, Self::Error> {
        Ok(Some(v.into()))
    }

    fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
        Ok(None)
    }

    fn serialize_some<T: ?Sized + serde::Serialize>(
        self,
        value: &T,
    ) -> Result<Self::Ok, Self::Error> {
        value.serialize(self)
    }

    fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
        unreachable!()
    }
    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
        unreachable!()
    }
    fn serialize_tuple(self, _len: usize) -> Result<Self::SerializeTuple, Self::Error> {
        unreachable!()
    }
    fn serialize_struct(
        self,
        _name: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeStruct, Self::Error> {
        unreachable!()
    }

    fn serialize_unit_struct(self, name: &'static str) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_unit_variant(
        self,
        name: &'static str,
        variant_index: u32,
        variant: &'static str,
    ) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_tuple_struct(
        self,
        name: &'static str,
        len: usize,
    ) -> Result<Self::SerializeTupleStruct, Self::Error> {
        unreachable!()
    }

    fn serialize_tuple_variant(
        self,
        name: &'static str,
        variant_index: u32,
        variant: &'static str,
        len: usize,
    ) -> Result<Self::SerializeTupleVariant, Self::Error> {
        todo!()
    }

    fn serialize_newtype_struct<T: ?Sized + serde::Serialize>(
        self,
        name: &'static str,
        value: &T,
    ) -> Result<Self::Ok, Self::Error> {
        todo!()
    }

    fn serialize_struct_variant(
        self,
        name: &'static str,
        variant_index: u32,
        variant: &'static str,
        len: usize,
    ) -> Result<Self::SerializeStructVariant, Self::Error> {
        todo!()
    }

    fn serialize_newtype_variant<T: ?Sized + serde::Serialize>(
        self,
        name: &'static str,
        variant_index: u32,
        variant: &'static str,
        value: &T,
    ) -> Result<Self::Ok, Self::Error> {
        todo!()
    }
}

pub struct ConfigSerializer<'r, 's> {
    pub config: &'r Config,
    pub db: &'s schema::UIDCDatabase,
    pub prefix: String,
}

impl<'r, 's> ConfigSerializer<'r, 's> {
    fn update(&self, key: &str, value: String) {
        // TODO: delete old config value
        // self.db.persistent_config.delete(schema::PersistentConfig { key: key.into(), value }).expect("couldn't update config");
        self.db
            .persistent_config
            .insert(schema::PersistentConfig {
                key: key.into(),
                value,
            })
            .expect("couldn't update config");
    }
}

impl<'r, 's> serde::ser::SerializeStruct for ConfigSerializer<'r, 's> {
    type Ok = ();
    type Error = ConfigError;

    fn serialize_field<T: ?Sized + serde::Serialize>(
        &mut self,
        key: &'static str,
        value: &T,
    ) -> Result<(), Self::Error> {
        let key = format!("{}{}", self.prefix, key);

        let value = value.serialize(&ValueToStringSerializer {})?;
        if let Some(value) = value {
            log::trace!("saving config {} = {}", key, value);
            self.update(key.as_str(), value);
        }

        Ok(())
    }

    fn end(self) -> Result<Self::Ok, Self::Error> {
        Ok(())
    }
}

impl<'r, 's> serde::Serializer for &'r ConfigSerializer<'r, 's> {
    type Ok = ();
    type Error = ConfigError;

    type SerializeSeq = serde::ser::Impossible<Self::Ok, Self::Error>;
    type SerializeMap = serde::ser::Impossible<Self::Ok, Self::Error>;
    type SerializeTuple = serde::ser::Impossible<Self::Ok, Self::Error>;
    type SerializeStruct = ConfigSerializer<'r, 's>;
    type SerializeTupleStruct = serde::ser::Impossible<Self::Ok, Self::Error>;
    type SerializeTupleVariant = serde::ser::Impossible<Self::Ok, Self::Error>;
    type SerializeStructVariant = serde::ser::Impossible<Self::Ok, Self::Error>;

    fn serialize_bool(self, v: bool) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_i8(self, v: i8) -> Result<Self::Ok, Self::Error> {
        self.serialize_i64(v as i64)
    }
    fn serialize_i16(self, v: i16) -> Result<Self::Ok, Self::Error> {
        self.serialize_i64(v as i64)
    }
    fn serialize_i32(self, v: i32) -> Result<Self::Ok, Self::Error> {
        self.serialize_i64(v as i64)
    }
    fn serialize_i64(self, v: i64) -> Result<Self::Ok, Self::Error> {
        todo!()
    }
    fn serialize_i128(self, v: i128) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_u8(self, v: u8) -> Result<Self::Ok, Self::Error> {
        self.serialize_u64(v as u64)
    }
    fn serialize_u16(self, v: u16) -> Result<Self::Ok, Self::Error> {
        self.serialize_u64(v as u64)
    }
    fn serialize_u32(self, v: u32) -> Result<Self::Ok, Self::Error> {
        self.serialize_u64(v as u64)
    }
    fn serialize_u64(self, v: u64) -> Result<Self::Ok, Self::Error> {
        todo!()
    }
    fn serialize_u128(self, v: u128) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_f32(self, v: f32) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }
    fn serialize_f64(self, v: f64) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_char(self, v: char) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_bytes(self, v: &[u8]) -> Result<Self::Ok, Self::Error> {
        todo!()
    }

    fn serialize_str(self, v: &str) -> Result<Self::Ok, Self::Error> {
        todo!()
    }

    fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
        Ok(())
    }

    fn serialize_some<T: ?Sized + serde::Serialize>(
        self,
        value: &T,
    ) -> Result<Self::Ok, Self::Error> {
        todo!()
    }

    fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
        unreachable!()
    }

    fn serialize_seq(self, len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
        todo!()
    }
    fn serialize_map(self, len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
        todo!()
    }
    fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple, Self::Error> {
        todo!()
    }
    fn serialize_struct(
        self,
        name: &'static str,
        _len: usize,
    ) -> Result<Self::SerializeStruct, Self::Error> {
        log::trace!("name: {name}");

        let new_prefix =
            // are we at the root?
            if name == "Config" {
                String::new()
            }
            else {
                format!("{}{}.", self.prefix, name)
            };

        let subser = ConfigSerializer {
            config: self.config,
            db: self.db,
            prefix: new_prefix,
        };

        Ok(subser)
    }

    fn serialize_unit_struct(self, name: &'static str) -> Result<Self::Ok, Self::Error> {
        todo!()
    }

    fn serialize_unit_variant(
        self,
        name: &'static str,
        variant_index: u32,
        variant: &'static str,
    ) -> Result<Self::Ok, Self::Error> {
        todo!()
    }

    fn serialize_tuple_struct(
        self,
        name: &'static str,
        len: usize,
    ) -> Result<Self::SerializeTupleStruct, Self::Error> {
        todo!()
    }

    fn serialize_tuple_variant(
        self,
        name: &'static str,
        variant_index: u32,
        variant: &'static str,
        len: usize,
    ) -> Result<Self::SerializeTupleVariant, Self::Error> {
        todo!()
    }

    fn serialize_newtype_struct<T: ?Sized + serde::Serialize>(
        self,
        name: &'static str,
        value: &T,
    ) -> Result<Self::Ok, Self::Error> {
        todo!()
    }

    fn serialize_struct_variant(
        self,
        name: &'static str,
        variant_index: u32,
        variant: &'static str,
        len: usize,
    ) -> Result<Self::SerializeStructVariant, Self::Error> {
        todo!()
    }

    fn serialize_newtype_variant<T: ?Sized + serde::Serialize>(
        self,
        name: &'static str,
        variant_index: u32,
        variant: &'static str,
        value: &T,
    ) -> Result<Self::Ok, Self::Error> {
        todo!()
    }
}

pub struct ConfigDeserializer<'de> {
    pub config_map: &'de std::collections::HashMap<String, String>,
    pub prefix: String,
}

#[derive(Debug)]
pub enum ConfigError {
    Missing(String),
    InvalidType(String),
    CustomError(String),
}

impl std::fmt::Display for ConfigError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Missing(what) => f.write_fmt(format_args!(
                "Missing required config entry: {}",
                what.as_str()
            )),
            Self::InvalidType(what) => f.write_fmt(format_args!(
                "Could not parse config entry '{}'",
                what.as_str()
            )),
            Self::CustomError(what) => {
                f.write_fmt(format_args!("Custom error '{}'", what.as_str()))
            }
        }
    }
}

impl std::error::Error for ConfigError {}

impl serde::ser::Error for ConfigError {
    fn custom<T>(msg: T) -> Self
    where
        T: std::fmt::Display,
    {
        Self::CustomError(msg.to_string())
    }
}

impl serde::de::Error for ConfigError {
    fn custom<T>(msg: T) -> Self
    where
        T: std::fmt::Display,
    {
        Self::CustomError(msg.to_string())
    }

    fn invalid_type(_unexp: serde::de::Unexpected, _exp: &dyn serde::de::Expected) -> Self {
        Self::InvalidType("".into())
    }

    fn missing_field(field: &'static str) -> Self {
        Self::Missing(field.into())
    }
}

impl<'de> serde::Deserializer<'de> for &'de mut ConfigDeserializer<'de> {
    type Error = ConfigError;

    fn deserialize_any<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'de>,
    {
        unreachable!("deserialize_any needs context")
    }

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

    fn deserialize_seq<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'de>,
    {
        todo!("deserialize_seq")
    }

    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'de>,
    {
        let mut map_access = ConfigDeserializerIterator {
            it: self
                .config_map
                .iter()
                .filter(|e| {
                    e.0.starts_with(&self.prefix) && !e.0[self.prefix.len()..].contains('.')
                })
                .peekable(),
        };

        visitor.visit_map(&mut map_access)
    }

    fn deserialize_enum<V>(
        self,
        _name: &'static str,
        _variants: &'static [&'static str],
        _visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'de>,
    {
        todo!("deserialize_enum")
    }

    fn deserialize_tuple<V>(self, _len: usize, _visitor: V) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'de>,
    {
        todo!("deserialize_tuple")
    }

    fn deserialize_tuple_struct<V>(
        self,
        _name: &'static str,
        _len: usize,
        _visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'de>,
    {
        todo!("deserialize_tuple_struct")
    }

    serde::forward_to_deserialize_any!(
        i8 u8 i16 u16 i32 u32 i64 u64 i128 u128 str string bytes
        bool f32 f64 char byte_buf option unit unit_struct
        newtype_struct identifier ignored_any
    );
}

struct AtomicForwarder<'de> {
    to_fwd: &'de str,
}

impl<'de> serde::Deserializer<'de> for AtomicForwarder<'de> {
    type Error = ConfigError;
    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'de>,
    {
        visitor.visit_unit()
    }

    fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'de>,
    {
        visitor.visit_u64(
            self.to_fwd
                .parse()
                .map_err(|_| ConfigError::InvalidType(String::new()))?,
        )
    }

    fn deserialize_str<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'de>,
    {
        visitor.visit_str(self.to_fwd)
    }

    fn deserialize_string<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'de>,
    {
        visitor.visit_str(self.to_fwd)
    }

    fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: serde::de::Visitor<'de>,
    {
        visitor.visit_str(self.to_fwd)
    }

    serde::forward_to_deserialize_any!(
        i8 u8 i16 u16 i32 u32 i64 i128 u128 bytes
        bool f32 f64 char byte_buf unit unit_struct option
        newtype_struct ignored_any struct tuple tuple_struct
        seq map enum
    );
}

struct ConfigDeserializerIterator<'de, I: Iterator<Item = (&'de String, &'de String)>> {
    it: std::iter::Peekable<I>,
}

impl<'de, I: Iterator<Item = (&'de String, &'de String)>> serde::de::MapAccess<'de>
    for ConfigDeserializerIterator<'de, I>
{
    type Error = ConfigError;

    fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error>
    where
        K: serde::de::DeserializeSeed<'de>,
    {
        if let Some(e) = self.it.peek() {
            let de = AtomicForwarder {
                to_fwd: e.0.as_str(),
            };
            Ok(seed.deserialize(de).ok())
        } else {
            Ok(None)
        }
    }

    fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Self::Error>
    where
        V: serde::de::DeserializeSeed<'de>,
    {
        let value = self.it.next().unwrap();

        let de = AtomicForwarder {
            to_fwd: value.1.as_str(),
        };

        seed.deserialize(de)
            .map_err(|e| ConfigError::InvalidType(e.to_string()))
    }
}