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

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

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

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

    pub fn to_be_bytes(self) -> [u8; 16] {
        self.0 .0.to_be_bytes()
    }

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

    pub fn new() -> Self {
        Self(Ulid::new())
    }

    pub fn from_str(s: &str) -> Result<Self, ulid::DecodeError> {
        let id = Ulid::from_string(s)?;
        Ok(id.into())
    }

    pub fn as_string(&self) -> String {
        self.0.to_string()
    }
}

//-************************************************************************
// standard trait impls
//-************************************************************************

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

impl Debug for DbId {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_tuple("DbId").field(&self.bytes()).finish()
    }
}

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

impl From<u128> for DbId {
    fn from(value: u128) -> Self {
        DbId(value.into())
    }
}

//-************************************************************************
// sqlx traits for going in and out of the db
//-************************************************************************

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_by_ref(&self, args: &mut Vec<SqliteArgumentValue<'q>>) -> IsNull {
        args.push(SqliteArgumentValue::Blob(Cow::Owned(self.bytes().to_vec())));
        IsNull::No
    }
}

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

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

struct DbIdVisitor;

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

    fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
        formatter.write_str("16 bytes")
    }

    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(u128::from_be_bytes(v).into()),
            Err(_) => Err(serde::de::Error::invalid_length(v.len(), &self)),
        }
    }

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

    fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
    where
        A: serde::de::SeqAccess<'de>,
    {
        let mut raw_bytes_from_db = [0u8; 16];
        let size = seq.size_hint().unwrap_or(0);
        let mut count = 0;
        while let Some(val) = seq.next_element()? {
            if count > 15 {
                break;
            }
            raw_bytes_from_db[count] = val;
            count += 1;
        }
        if count != 16 || size > 16 {
            let sz = if count < 16 { count } else { size };
            Err(serde::de::Error::invalid_length(sz, &self))
        } else {
            Ok(u128::from_be_bytes(raw_bytes_from_db).into())
        }
    }
}

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

//-************************************************************************
// serialization tests
//-************************************************************************

#[cfg(test)]
mod test {
    use serde_test::{assert_tokens, Token};

    use super::*;

    #[test]
    fn test_ser_de() {
        let bytes: [u8; 16] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
        let id: DbId = u128::from_be_bytes(bytes).into();

        assert_tokens(
            &id,
            &[Token::Bytes(&[
                0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
            ])],
        );
    }
}