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use std::ops::{Deref, DerefMut};

use proc_macro2::TokenStream;

use crate::token_store::{AddTokens, TokenLevel, TokenStore};

/// Data passed between stages during generation of [`Generatable`](crate::generatable::Generatable) types.
#[derive(Debug, Default)]
pub struct PassedData<T> {
    /// The tokens returned by the stage
    tokens: Option<TokenStream>,
    /// The data passed
    data: T,
}

impl<T> Eq for PassedData<T> where T: Eq {}

impl<T> PartialEq for PassedData<T>
where
    T: Eq,
{
    fn eq(&self, other: &Self) -> bool {
        let data_is_equal = self.data == other.data;

        let self_string_tokens = self.tokens.as_ref().map(ToString::to_string);
        let other_string_tokens = other.tokens.as_ref().map(ToString::to_string);

        let tokens_are_equal = self_string_tokens == other_string_tokens;

        data_is_equal && tokens_are_equal
    }
}

impl<T> From<PassedData<T>> for TokenStream {
    fn from(passed_data: PassedData<T>) -> Self {
        passed_data.tokens.unwrap_or_default()
    }
}

impl<T> PassedData<T> {
    /// Create new passed data from tokens
    pub fn tokens(tokens: TokenStream) -> Self
    where
        T: Default,
    {
        Self {
            tokens: Some(tokens),
            data: T::default(),
        }
    }

    /// Create new passed data from the data.
    pub fn data(data: T) -> Self {
        Self { tokens: None, data }
    }

    /// Remove the data from `Self`.
    pub fn without_data(self) -> PassedData<()> {
        PassedData {
            tokens: self.tokens,
            data: (),
        }
    }

    /// Change tokens of `Self` to `tokens`.
    pub fn with_tokens(self, tokens: TokenStream) -> Self {
        Self {
            data: self.data,
            tokens: Some(tokens),
        }
    }

    /// Seperate tokens into a [`TokenStore`](crate::token_store::TokenStore), and return the passed data.
    pub(crate) fn seperate_tokens_into(
        self,
        token_level: TokenLevel,
        token_store: &mut TokenStore,
    ) -> T {
        token_store.add_tokens(token_level, self.tokens);

        self.data
    }
}

/// Add some data to some tokens, wrapping them into [`PassedData`].
pub trait WithData {
    fn with_data<T>(self, data: T) -> PassedData<T>;
}

impl WithData for TokenStream {
    fn with_data<T>(self, data: T) -> PassedData<T> {
        PassedData {
            tokens: Some(self),
            data,
        }
    }
}

impl<T> Deref for PassedData<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.data
    }
}

impl<T> DerefMut for PassedData<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.data
    }
}