use crate::table::column::{ColumnType, ColumnKind, ColumnData, FromDataError};

use std::time::{SystemTime, UNIX_EPOCH};
use std::fmt;
use std::str::FromStr;
use std::borrow::Cow;

use rand::{RngCore, rngs::OsRng};
use base64::engine::{Engine, general_purpose::URL_SAFE_NO_PAD};
use base64::DecodeError;

use serde::{Serialize, Deserialize};
use serde::ser::Serializer;
use serde::de::{Deserializer, Error};

/// A UniqueId that can be used within a database. 
/// Is not cryptographically secure and could be bruteforced.
///
/// Contains 10bytes
/// - 0..5 are seconds since the UNIX_EPOCH 
/// - 5..10 are random
#[derive(Clone, Copy, PartialEq, Eq, Hash)]
pub struct UniqueId([u8; 10]);

impl UniqueId {
	pub fn new() -> Self {
		let secs_bytes = SystemTime::now()
			.duration_since(UNIX_EPOCH)
			.expect("SystemTime before UNIX EPOCH!")
			.as_secs()
			.to_be_bytes();

		let mut bytes = [0u8; 10];
		bytes[..5].copy_from_slice(&secs_bytes[3..8]);

		OsRng.fill_bytes(&mut bytes[5..]);

		Self(bytes)
	}

	/// This creates a unique id with it's raw content
	/// making it able to be called in a const context.
	pub const fn from_raw(inner: [u8; 10]) -> Self {
		Self(inner)
	}

	pub fn from_slice_unchecked(slice: &[u8]) -> Self {
		let mut bytes = [0u8; 10];
		bytes.copy_from_slice(slice);
		Self(bytes)
	}

	pub fn to_b64(&self) -> String {
		URL_SAFE_NO_PAD.encode(self.0)
	}

	// this panics if b64 has not a length of 14
	pub fn parse_from_b64<T>(b64: T) -> Result<Self, DecodeError>
	where T: AsRef<[u8]> {
		let mut bytes = [0u8; 10];
		URL_SAFE_NO_PAD.decode_slice_unchecked(b64, &mut bytes)
			.map(|n| assert_eq!(n, bytes.len()))
			.map(|_| Self(bytes))
	}

	pub fn from_bytes(bytes: [u8; 10]) -> Self {
		Self(bytes)
	}

	pub fn into_bytes(self) -> [u8; 10] {
		self.0
	}

	pub fn since_unix_secs(&self) -> u64 {
		let mut bytes = [0u8; 8];
		bytes[3..].copy_from_slice(&self.0[..5]);
		u64::from_be_bytes(bytes)
	}

	pub fn as_slice(&self) -> &[u8] {
		&self.0
	}
}

impl fmt::Debug for UniqueId {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		f.debug_tuple("UniqueId")
			.field(&self.to_b64())
			.finish()
	}
}

impl fmt::Display for UniqueId {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		self.to_b64().fmt(f)
	}
}

impl FromStr for UniqueId {
	type Err = DecodeError;

	fn from_str(s: &str) -> Result<Self, Self::Err> {
		Self::parse_from_b64(s)
	}
}

impl From<DecodeError> for FromDataError {
	fn from(e: DecodeError) -> Self {
		Self::CustomString(format!("uniqueid decode error {:?}", e))
	}
}

impl ColumnType for UniqueId {

	fn column_kind() -> ColumnKind {
		ColumnKind::FixedText(14)
	}

	fn to_data(&self) -> ColumnData<'_> {
		ColumnData::Text(self.to_b64().into())
	}

	fn from_data(data: ColumnData) -> Result<Self, FromDataError> {
		match data {
			ColumnData::Text(s) if s.len() == 14 => Ok(Self::parse_from_b64(s.as_str())?),
			_ => Err(FromDataError::ExpectedType("char with 14 chars for unique id"))
		}
	}

}
// SERDE

impl Serialize for UniqueId {
	fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
	where S: Serializer {
		serializer.serialize_str(&self.to_b64())
	}
}

impl<'de> Deserialize<'de> for UniqueId {
	fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
	where D: Deserializer<'de> {
		let s: Cow<'_, str> = Deserialize::deserialize(deserializer)?;
		let s = s.as_ref();
		if s.len() == 14 {
			UniqueId::parse_from_b64(s)
				.map_err(D::Error::custom)
		} else {
			Err(D::Error::custom("expected string with exactly 14 characters"))
		}
	}
}

#[cfg(feature = "protobuf")]
mod protobuf {
	use super::*;

	use fire_protobuf::{
		WireType,
		encode::{
			EncodeMessage, MessageEncoder, FieldOpt, SizeBuilder, EncodeError
		},
		decode::{DecodeMessage, FieldKind, DecodeError},
		bytes::BytesWrite
	};

	impl EncodeMessage for UniqueId {
		const WIRE_TYPE: WireType = WireType::Len;

		fn is_default(&self) -> bool {
			false
		}

		fn encoded_size(
			&mut self,
			field: Option<FieldOpt>,
			builder: &mut SizeBuilder
		) -> Result<(), EncodeError> {
			self.0.encoded_size(field, builder)
		}

		fn encode<B>(
			&mut self,
			field: Option<FieldOpt>,
			encoder: &mut MessageEncoder<B>
		) -> Result<(), EncodeError>
		where B: BytesWrite {
			self.0.encode(field, encoder)
		}
	}

	impl<'m> DecodeMessage<'m> for UniqueId {
		const WIRE_TYPE: WireType = WireType::Len;

		fn decode_default() -> Self {
			Self::from_raw([0; 10])
		}

		fn merge(
			&mut self,
			kind: FieldKind<'m>,
			is_field: bool
		) -> Result<(), DecodeError> {
			self.0.merge(kind, is_field)
		}
	}
}

#[cfg(feature = "graphql")]
mod graphql {
	use super::*;

	use juniper::{graphql_scalar, Value};

	#[graphql_scalar]
	impl<S> GraphQlScalar for UniqueId
	where S: ScalarValue {
		fn resolve(&self) -> Value {
			Value::scalar(self.to_string())
		}

		fn from_input_value(value: &InputValue) -> Option<UniqueId> {
			value.as_string_value().and_then(|s| s.parse().ok())
		}

		fn from_str<'a>(
			value: ScalarToken<'a>
		) -> juniper::ParseScalarResult<'a, S> {
			<String as juniper::ParseScalarValue<S>>::from_str(value)
		}
	}
}

#[cfg(test)]
mod tests {

	use super::*;
	use serde_json::{Value, from_value, from_str};

	// abcdefghijklmnopqrstuvwxyz

	#[test]
	fn serde_test() {
		let s = "\"AGCGeWIDTlipbg\"";
		let d: UniqueId = from_str(s).unwrap();
		assert_eq!(d.to_string(), "AGCGeWIDTlipbg");

		let v = Value::String("AGCGeWIDTlipbg".into());
		let d: UniqueId = from_value(v).unwrap();
		assert_eq!(d.to_string(), "AGCGeWIDTlipbg");
	}

}