use std::{borrow::Cow, fmt::Display};

use serde::{de::Visitor, Deserialize, Serialize};
use sqlx::{
    encode::IsNull,
    sqlite::{SqliteArgumentValue, SqliteValueRef},
    Decode, Encode, Sqlite,
};
use ulid::Ulid;

#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct DbId(pub Ulid);

impl From<Ulid> for DbId {
    fn from(value: Ulid) -> Self {
        DbId(value)
    }
}

impl sqlx::Type<sqlx::Sqlite> for DbId {
    fn type_info() -> <sqlx::Sqlite as sqlx::Database>::TypeInfo {
        <&[u8] as sqlx::Type<sqlx::Sqlite>>::type_info()
    }
}

impl<'q> Encode<'q, Sqlite> for DbId {
    fn encode(self, args: &mut Vec<SqliteArgumentValue<'q>>) -> IsNull {
        args.push(SqliteArgumentValue::Blob(Cow::Owned(self.bytes().to_vec())));
        IsNull::No
    }

    fn encode_by_ref(&self, args: &mut Vec<SqliteArgumentValue<'q>>) -> IsNull {
        args.push(SqliteArgumentValue::Blob(Cow::Owned(self.bytes().to_vec())));

        IsNull::No
    }

    fn produces(&self) -> Option<<Sqlite as sqlx::Database>::TypeInfo> {
        // `produces` is inherently a hook to allow database drivers to produce
        // value-dependent type information; if the driver doesn't need this, it
        // can leave this as `None`
        None
    }

    fn size_hint(&self) -> usize {
        std::mem::size_of_val(self)
    }
}

impl<'r> Decode<'r, Sqlite> for DbId {
    fn decode(value: SqliteValueRef<'r>) -> Result<Self, sqlx::error::BoxDynError> {
        let bytes = <&[u8] as Decode<Sqlite>>::decode(value)?;
        let bytes: [u8; 16] = bytes.try_into().unwrap_or_default();
        let id: Ulid = u128::from_ne_bytes(bytes).into();
        Ok(id.into())
    }
}

impl Display for DbId {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0.to_string())
    }
}

impl DbId {
    pub fn bytes(&self) -> [u8; 16] {
        self.0 .0.to_ne_bytes()
    }

    pub fn is_nil(&self) -> bool {
        self.0.is_nil()
    }

    pub fn new() -> Self {
        let id = Ulid::new();
        Self(id)
    }
}

impl Serialize for DbId {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        serializer.serialize_bytes(&self.0 .0.to_ne_bytes())
    }
}

struct IdVisitor;

impl<'de> Visitor<'de> for IdVisitor {
    type Value = DbId;

    fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
        formatter.write_str("a 128-bit number")
    }

    fn visit_i128<E>(self, v: i128) -> Result<Self::Value, E>
    where
        E: serde::de::Error,
    {
        Ok(DbId(Ulid(v as u128)))
    }

    fn visit_u128<E>(self, v: u128) -> Result<Self::Value, E>
    where
        E: serde::de::Error,
    {
        Ok(DbId(Ulid(v)))
    }

    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
    where
        E: serde::de::Error,
    {
        match std::convert::TryInto::<[u8; 16]>::try_into(v) {
            Ok(v) => Ok(DbId(Ulid(u128::from_ne_bytes(v)))),
            Err(_) => Err(serde::de::Error::invalid_length(v.len(), &self)),
        }
    }

    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
    where
        E: serde::de::Error,
    {
        match Ulid::from_string(&v) {
            Ok(v) => Ok(DbId(v)),
            Err(_) => Err(serde::de::Error::invalid_value(
                serde::de::Unexpected::Str(&format!("could not convert {v} to a ULID")),
                &self,
            )),
        }
    }
}

impl<'de> Deserialize<'de> for DbId {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        deserializer.deserialize_bytes(IdVisitor)
    }
}