use serde::Deserialize;
use serde_json::Value;
use sqlx_core::{
    decode::Decode,
    encode::{Encode, IsNull},
    error::BoxDynError,
    types::Type,
};

use crate::{
    arguments::ExaBuffer,
    database::Exasol,
    type_info::{Decimal, ExaDataType, ExaTypeInfo},
    value::ExaValueRef,
};

/// Numbers below this threshold must be serialized/deserialized as integers.
/// The ones above must be treated as strings.
const MAX_U64_NUMERIC: u64 = 1_000_000_000_000_000_000;
const MAX_U128_NUMERIC: u128 = 1_000_000_000_000_000_000;

impl Type<Exasol> for u8 {
    fn type_info() -> ExaTypeInfo {
        ExaDataType::Decimal(Decimal::new(Decimal::MAX_8BIT_PRECISION, 0)).into()
    }

    fn compatible(ty: &ExaTypeInfo) -> bool {
        <Self as Type<Exasol>>::type_info().compatible(ty)
    }
}

impl Encode<'_, Exasol> for u8 {
    fn encode_by_ref(&self, buf: &mut ExaBuffer) -> Result<IsNull, BoxDynError> {
        buf.append(self)?;
        Ok(IsNull::No)
    }

    fn produces(&self) -> Option<ExaTypeInfo> {
        let precision = self.checked_ilog10().unwrap_or_default() + 1;
        Some(ExaDataType::Decimal(Decimal::new(precision, 0)).into())
    }

    fn size_hint(&self) -> usize {
        Decimal::MAX_8BIT_PRECISION as usize
    }
}

impl Decode<'_, Exasol> for u8 {
    fn decode(value: ExaValueRef<'_>) -> Result<Self, BoxDynError> {
        <Self as Deserialize>::deserialize(value.value).map_err(From::from)
    }
}

impl Type<Exasol> for u16 {
    fn type_info() -> ExaTypeInfo {
        ExaDataType::Decimal(Decimal::new(Decimal::MAX_16BIT_PRECISION, 0)).into()
    }

    fn compatible(ty: &ExaTypeInfo) -> bool {
        <Self as Type<Exasol>>::type_info().compatible(ty)
    }
}

impl Encode<'_, Exasol> for u16 {
    fn encode_by_ref(&self, buf: &mut ExaBuffer) -> Result<IsNull, BoxDynError> {
        buf.append(self)?;
        Ok(IsNull::No)
    }

    fn produces(&self) -> Option<ExaTypeInfo> {
        let precision = self.checked_ilog10().unwrap_or_default() + 1;
        Some(ExaDataType::Decimal(Decimal::new(precision, 0)).into())
    }

    fn size_hint(&self) -> usize {
        Decimal::MAX_16BIT_PRECISION as usize
    }
}

impl Decode<'_, Exasol> for u16 {
    fn decode(value: ExaValueRef<'_>) -> Result<Self, BoxDynError> {
        <Self as Deserialize>::deserialize(value.value).map_err(From::from)
    }
}

impl Type<Exasol> for u32 {
    fn type_info() -> ExaTypeInfo {
        ExaDataType::Decimal(Decimal::new(Decimal::MAX_32BIT_PRECISION, 0)).into()
    }

    fn compatible(ty: &ExaTypeInfo) -> bool {
        <Self as Type<Exasol>>::type_info().compatible(ty)
    }
}

impl Encode<'_, Exasol> for u32 {
    fn encode_by_ref(&self, buf: &mut ExaBuffer) -> Result<IsNull, BoxDynError> {
        buf.append(self)?;
        Ok(IsNull::No)
    }

    fn produces(&self) -> Option<ExaTypeInfo> {
        let precision = self.checked_ilog10().unwrap_or_default() + 1;
        Some(ExaDataType::Decimal(Decimal::new(precision, 0)).into())
    }

    fn size_hint(&self) -> usize {
        Decimal::MAX_32BIT_PRECISION as usize
    }
}

impl Decode<'_, Exasol> for u32 {
    fn decode(value: ExaValueRef<'_>) -> Result<Self, BoxDynError> {
        <Self as Deserialize>::deserialize(value.value).map_err(From::from)
    }
}

impl Type<Exasol> for u64 {
    fn type_info() -> ExaTypeInfo {
        ExaDataType::Decimal(Decimal::new(Decimal::MAX_64BIT_PRECISION, 0)).into()
    }

    fn compatible(ty: &ExaTypeInfo) -> bool {
        <Self as Type<Exasol>>::type_info().compatible(ty)
    }
}

impl Encode<'_, Exasol> for u64 {
    fn encode_by_ref(&self, buf: &mut ExaBuffer) -> Result<IsNull, BoxDynError> {
        if self < &MAX_U64_NUMERIC {
            buf.append(self)?;
        } else {
            // Large numbers get serialized as strings
            buf.append(format_args!("{self}"))?;
        };

        Ok(IsNull::No)
    }

    fn produces(&self) -> Option<ExaTypeInfo> {
        let precision = self.checked_ilog10().unwrap_or_default() + 1;
        Some(ExaDataType::Decimal(Decimal::new(precision, 0)).into())
    }

    fn size_hint(&self) -> usize {
        Decimal::MAX_64BIT_PRECISION as usize
    }
}

impl Decode<'_, Exasol> for u64 {
    fn decode(value: ExaValueRef<'_>) -> Result<Self, BoxDynError> {
        match value.value {
            Value::Number(n) => <Self as Deserialize>::deserialize(n).map_err(From::from),
            Value::String(s) => serde_json::from_str(s).map_err(From::from),
            v => Err(format!("invalid u64 value: {v}").into()),
        }
    }
}

impl Type<Exasol> for u128 {
    fn type_info() -> ExaTypeInfo {
        ExaDataType::Decimal(Decimal::new(Decimal::MAX_128BIT_PRECISION, 0)).into()
    }

    fn compatible(ty: &ExaTypeInfo) -> bool {
        <Self as Type<Exasol>>::type_info().compatible(ty)
    }
}

impl Encode<'_, Exasol> for u128 {
    fn encode_by_ref(&self, buf: &mut ExaBuffer) -> Result<IsNull, BoxDynError> {
        if self < &MAX_U128_NUMERIC {
            buf.append(self)?;
        } else {
            // Large numbers get serialized as strings
            buf.append(format_args!("{self}"))?;
        };

        Ok(IsNull::No)
    }

    fn produces(&self) -> Option<ExaTypeInfo> {
        let precision = self.checked_ilog10().unwrap_or_default() + 1;
        Some(ExaDataType::Decimal(Decimal::new(precision, 0)).into())
    }

    fn size_hint(&self) -> usize {
        Decimal::MAX_128BIT_PRECISION as usize
    }
}

impl Decode<'_, Exasol> for u128 {
    fn decode(value: ExaValueRef<'_>) -> Result<Self, BoxDynError> {
        match value.value {
            Value::Number(n) => <Self as Deserialize>::deserialize(n).map_err(From::from),
            Value::String(s) => serde_json::from_str(s).map_err(From::from),
            v => Err(format!("invalid u128 value: {v}").into()),
        }
    }
}