// Copyright 2021 IOTA Stiftung
// SPDX-License-Identifier: Apache-2.0

use alloc::{boxed::Box, vec::Vec};

use derive_more::{Deref, DerefMut};
use hashbrown::HashMap;
use iterator_sorted::is_unique_sorted;
use packable::{bounded::BoundedU8, prefix::BoxedSlicePrefix, Packable};
use primitive_types::U256;

use crate::{output::TokenId, Error};

///
#[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Packable)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[packable(unpack_error = Error)]
pub struct NativeToken {
    // Identifier of the native token.
    token_id: TokenId,
    // Amount of native tokens.
    #[packable(verify_with = verify_amount)]
    amount: U256,
}

impl NativeToken {
    /// Creates a new [`NativeToken`].
    #[inline(always)]
    pub fn new(token_id: TokenId, amount: U256) -> Result<Self, Error> {
        verify_amount::<true>(&amount)?;

        Ok(Self { token_id, amount })
    }

    /// Returns the token ID of the [`NativeToken`].
    #[inline(always)]
    pub fn token_id(&self) -> &TokenId {
        &self.token_id
    }

    /// Returns the amount of the [`NativeToken`].
    #[inline(always)]
    pub fn amount(&self) -> &U256 {
        &self.amount
    }
}

#[inline]
fn verify_amount<const VERIFY: bool>(amount: &U256) -> Result<(), Error> {
    if VERIFY && amount.is_zero() {
        Err(Error::NativeTokensNullAmount)
    } else {
        Ok(())
    }
}

/// A builder for [`NativeTokens`].
#[derive(Clone, Default, Debug, Deref, DerefMut)]
#[must_use]
pub struct NativeTokensBuilder(HashMap<TokenId, U256>);

impl NativeTokensBuilder {
    /// Creates a new [`NativeTokensBuilder`].
    #[inline(always)]
    pub fn new() -> Self {
        Self::default()
    }

    /// Adds the given [`NativeToken`].
    pub fn add_native_token(&mut self, native_token: NativeToken) -> Result<(), Error> {
        let entry = self.0.entry(*native_token.token_id()).or_default();
        *entry = entry
            .checked_add(*native_token.amount())
            .ok_or(Error::NativeTokensOverflow)?;

        Ok(())
    }

    /// Adds the given [`NativeTokens`].
    pub fn add_native_tokens(&mut self, native_tokens: NativeTokens) -> Result<(), Error> {
        for native_token in native_tokens {
            self.add_native_token(native_token)?;
        }

        Ok(())
    }

    /// Merges another [`NativeTokensBuilder`] into this one.
    pub fn merge(&mut self, other: NativeTokensBuilder) -> Result<(), Error> {
        for (token_id, amount) in other.0.into_iter() {
            self.add_native_token(NativeToken::new(token_id, amount)?)?;
        }

        Ok(())
    }

    /// Finishes the [`NativeTokensBuilder`] into [`NativeTokens`].
    pub fn finish(self) -> Result<NativeTokens, Error> {
        NativeTokens::try_from(
            self.0
                .into_iter()
                .map(|(token_id, amount)| NativeToken::new(token_id, amount))
                .collect::<Result<Vec<_>, _>>()?,
        )
    }
}

impl From<NativeTokens> for NativeTokensBuilder {
    fn from(native_tokens: NativeTokens) -> Self {
        let mut builder = NativeTokensBuilder::new();

        // PANIC: safe as `native_tokens` was already built and then valid.
        builder.add_native_tokens(native_tokens).unwrap();
        builder
    }
}

pub(crate) type NativeTokenCount = BoundedU8<0, { NativeTokens::COUNT_MAX }>;

///
#[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Deref, Packable)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[packable(unpack_error = Error, with = |e| e.unwrap_item_err_or_else(|p| Error::InvalidNativeTokenCount(p.into())))]
pub struct NativeTokens(
    #[packable(verify_with = verify_unique_sorted)] BoxedSlicePrefix<NativeToken, NativeTokenCount>,
);

impl TryFrom<Vec<NativeToken>> for NativeTokens {
    type Error = Error;

    #[inline(always)]
    fn try_from(native_tokens: Vec<NativeToken>) -> Result<Self, Self::Error> {
        Self::new(native_tokens)
    }
}

impl IntoIterator for NativeTokens {
    type Item = NativeToken;
    type IntoIter = alloc::vec::IntoIter<Self::Item>;

    fn into_iter(self) -> Self::IntoIter {
        Vec::from(Into::<Box<[NativeToken]>>::into(self.0)).into_iter()
    }
}

impl NativeTokens {
    /// Maximum number of different native tokens that can be referenced in one transaction.
    pub const COUNT_MAX: u8 = 64;

    /// Creates a new [`NativeTokens`].
    pub fn new(native_tokens: Vec<NativeToken>) -> Result<Self, Error> {
        let mut native_tokens =
            BoxedSlicePrefix::<NativeToken, NativeTokenCount>::try_from(native_tokens.into_boxed_slice())
                .map_err(Error::InvalidNativeTokenCount)?;

        native_tokens.sort_by(|a, b| a.token_id().cmp(b.token_id()));
        // Sort is obviously fine now but uniqueness still needs to be checked.
        verify_unique_sorted::<true>(&native_tokens)?;

        Ok(Self(native_tokens))
    }

    /// Creates a new [`NativeTokensBuilder`].
    #[inline(always)]
    pub fn build() -> NativeTokensBuilder {
        NativeTokensBuilder::new()
    }
}

#[inline]
fn verify_unique_sorted<const VERIFY: bool>(native_tokens: &[NativeToken]) -> Result<(), Error> {
    if VERIFY && !is_unique_sorted(native_tokens.iter().map(NativeToken::token_id)) {
        Err(Error::NativeTokensNotUniqueSorted)
    } else {
        Ok(())
    }
}

#[cfg(feature = "dto")]
#[allow(missing_docs)]
pub mod dto {
    use serde::{Deserialize, Serialize};

    use super::*;
    use crate::{dto::U256Dto, error::dto::DtoError, output::token_id::dto::TokenIdDto};

    /// Describes a native token.
    #[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
    pub struct NativeTokenDto {
        // Identifier of the native token.
        #[serde(rename = "id")]
        pub token_id: TokenIdDto,
        // Amount of native tokens hex encoded.
        pub amount: U256Dto,
    }

    impl From<&NativeToken> for NativeTokenDto {
        fn from(value: &NativeToken) -> Self {
            Self {
                token_id: TokenIdDto(value.token_id().to_string()),
                amount: value.amount().into(),
            }
        }
    }

    impl TryFrom<&NativeTokenDto> for NativeToken {
        type Error = DtoError;

        fn try_from(value: &NativeTokenDto) -> Result<Self, Self::Error> {
            Self::new(
                (&value.token_id).try_into()?,
                U256::try_from(&value.amount).map_err(|_| DtoError::InvalidField("amount"))?,
            )
            .map_err(|_| DtoError::InvalidField("nativeTokens"))
        }
    }
}