use crate::{IdentFragment, ToTokens, TokenStreamExt};
use std::fmt;
use std::ops::BitOr;

pub use proc_macro2::*;

pub struct HasIterator; // True
pub struct ThereIsNoIteratorInRepetition; // False

impl BitOr<ThereIsNoIteratorInRepetition> for ThereIsNoIteratorInRepetition {
    type Output = ThereIsNoIteratorInRepetition;
    fn bitor(self, _rhs: ThereIsNoIteratorInRepetition) -> ThereIsNoIteratorInRepetition {
        ThereIsNoIteratorInRepetition
    }
}

impl BitOr<ThereIsNoIteratorInRepetition> for HasIterator {
    type Output = HasIterator;
    fn bitor(self, _rhs: ThereIsNoIteratorInRepetition) -> HasIterator {
        HasIterator
    }
}

impl BitOr<HasIterator> for ThereIsNoIteratorInRepetition {
    type Output = HasIterator;
    fn bitor(self, _rhs: HasIterator) -> HasIterator {
        HasIterator
    }
}

impl BitOr<HasIterator> for HasIterator {
    type Output = HasIterator;
    fn bitor(self, _rhs: HasIterator) -> HasIterator {
        HasIterator
    }
}

/// Extension traits used by the implementation of `quote!`. These are defined
/// in separate traits, rather than as a single trait due to ambiguity issues.
///
/// These traits expose a `quote_into_iter` method which should allow calling
/// whichever impl happens to be applicable. Calling that method repeatedly on
/// the returned value should be idempotent.
pub mod ext {
    use super::RepInterp;
    use super::{HasIterator as HasIter, ThereIsNoIteratorInRepetition as DoesNotHaveIter};
    use crate::ToTokens;
    use std::collections::btree_set::{self, BTreeSet};
    use std::slice;

    /// Extension trait providing the `quote_into_iter` method on iterators.
    pub trait RepIteratorExt: Iterator + Sized {
        fn quote_into_iter(self) -> (Self, HasIter) {
            (self, HasIter)
        }
    }

    impl<T: Iterator> RepIteratorExt for T {}

    /// Extension trait providing the `quote_into_iter` method for
    /// non-iterable types. These types interpolate the same value in each
    /// iteration of the repetition.
    pub trait RepToTokensExt {
        /// Pretend to be an iterator for the purposes of `quote_into_iter`.
        /// This allows repeated calls to `quote_into_iter` to continue
        /// correctly returning DoesNotHaveIter.
        fn next(&self) -> Option<&Self> {
            Some(self)
        }

        fn quote_into_iter(&self) -> (&Self, DoesNotHaveIter) {
            (self, DoesNotHaveIter)
        }
    }

    impl<T: ToTokens + ?Sized> RepToTokensExt for T {}

    /// Extension trait providing the `quote_into_iter` method for types that
    /// can be referenced as an iterator.
    pub trait RepAsIteratorExt<'q> {
        type Iter: Iterator;

        fn quote_into_iter(&'q self) -> (Self::Iter, HasIter);
    }

    impl<'q, 'a, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &'a T {
        type Iter = T::Iter;

        fn quote_into_iter(&'q self) -> (Self::Iter, HasIter) {
            <T as RepAsIteratorExt>::quote_into_iter(*self)
        }
    }

    impl<'q, 'a, T: RepAsIteratorExt<'q> + ?Sized> RepAsIteratorExt<'q> for &'a mut T {
        type Iter = T::Iter;

        fn quote_into_iter(&'q self) -> (Self::Iter, HasIter) {
            <T as RepAsIteratorExt>::quote_into_iter(*self)
        }
    }

    impl<'q, T: 'q> RepAsIteratorExt<'q> for [T] {
        type Iter = slice::Iter<'q, T>;

        fn quote_into_iter(&'q self) -> (Self::Iter, HasIter) {
            (self.iter(), HasIter)
        }
    }

    impl<'q, T: 'q> RepAsIteratorExt<'q> for Vec<T> {
        type Iter = slice::Iter<'q, T>;

        fn quote_into_iter(&'q self) -> (Self::Iter, HasIter) {
            (self.iter(), HasIter)
        }
    }

    impl<'q, T: 'q> RepAsIteratorExt<'q> for BTreeSet<T> {
        type Iter = btree_set::Iter<'q, T>;

        fn quote_into_iter(&'q self) -> (Self::Iter, HasIter) {
            (self.iter(), HasIter)
        }
    }

    macro_rules! array_rep_slice {
        ($($l:tt)*) => {
            $(
                impl<'q, T: 'q> RepAsIteratorExt<'q> for [T; $l] {
                    type Iter = slice::Iter<'q, T>;

                    fn quote_into_iter(&'q self) -> (Self::Iter, HasIter) {
                        (self.iter(), HasIter)
                    }
                }
            )*
        }
    }

    array_rep_slice!(
        0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
        17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
    );

    impl<'q, T: RepAsIteratorExt<'q>> RepAsIteratorExt<'q> for RepInterp<T> {
        type Iter = T::Iter;

        fn quote_into_iter(&'q self) -> (Self::Iter, HasIter) {
            self.0.quote_into_iter()
        }
    }
}

// Helper type used within interpolations to allow for repeated binding names.
// Implements the relevant traits, and exports a dummy `next()` method.
#[derive(Copy, Clone)]
pub struct RepInterp<T>(pub T);

impl<T> RepInterp<T> {
    // This method is intended to look like `Iterator::next`, and is called when
    // a name is bound multiple times, as the previous binding will shadow the
    // original `Iterator` object. This allows us to avoid advancing the
    // iterator multiple times per iteration.
    pub fn next(self) -> Option<T> {
        Some(self.0)
    }
}

impl<T: Iterator> Iterator for RepInterp<T> {
    type Item = T::Item;

    fn next(&mut self) -> Option<Self::Item> {
        self.0.next()
    }
}

impl<T: ToTokens> ToTokens for RepInterp<T> {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        self.0.to_tokens(tokens);
    }
}

fn is_ident_start(c: u8) -> bool {
    (b'a' <= c && c <= b'z') || (b'A' <= c && c <= b'Z') || c == b'_'
}

fn is_ident_continue(c: u8) -> bool {
    (b'a' <= c && c <= b'z') || (b'A' <= c && c <= b'Z') || c == b'_' || (b'0' <= c && c <= b'9')
}

fn is_ident(token: &str) -> bool {
    let mut iter = token.bytes();
    let first_ok = iter.next().map(is_ident_start).unwrap_or(false);

    first_ok && iter.all(is_ident_continue)
}

pub fn parse(tokens: &mut TokenStream, span: Span, s: &str) {
    if is_ident(s) {
        // Fast path, since idents are the most common token.
        tokens.append(Ident::new(s, span));
    } else {
        let s: TokenStream = s.parse().expect("invalid token stream");
        tokens.extend(s.into_iter().map(|mut t| {
            t.set_span(span);
            t
        }));
    }
}

macro_rules! push_punct {
    ($name:ident $char1:tt) => {
        pub fn $name(tokens: &mut TokenStream, span: Span) {
            let mut punct = Punct::new($char1, Spacing::Alone);
            punct.set_span(span);
            tokens.append(punct);
        }
    };
    ($name:ident $char1:tt $char2:tt) => {
        pub fn $name(tokens: &mut TokenStream, span: Span) {
            let mut punct = Punct::new($char1, Spacing::Joint);
            punct.set_span(span);
            tokens.append(punct);
            let mut punct = Punct::new($char2, Spacing::Alone);
            punct.set_span(span);
            tokens.append(punct);
        }
    };
    ($name:ident $char1:tt $char2:tt $char3:tt) => {
        pub fn $name(tokens: &mut TokenStream, span: Span) {
            let mut punct = Punct::new($char1, Spacing::Joint);
            punct.set_span(span);
            tokens.append(punct);
            let mut punct = Punct::new($char2, Spacing::Joint);
            punct.set_span(span);
            tokens.append(punct);
            let mut punct = Punct::new($char3, Spacing::Alone);
            punct.set_span(span);
            tokens.append(punct);
        }
    };
}

push_punct!(push_add '+');
push_punct!(push_add_eq '+' '=');
push_punct!(push_and '&');
push_punct!(push_and_and '&' '&');
push_punct!(push_and_eq '&' '=');
push_punct!(push_at '@');
push_punct!(push_bang '!');
push_punct!(push_caret '^');
push_punct!(push_caret_eq '^' '=');
push_punct!(push_colon ':');
push_punct!(push_colon2 ':' ':');
push_punct!(push_comma ',');
push_punct!(push_div '/');
push_punct!(push_div_eq '/' '=');
push_punct!(push_dot '.');
push_punct!(push_dot2 '.' '.');
push_punct!(push_dot3 '.' '.' '.');
push_punct!(push_dot_dot_eq '.' '.' '=');
push_punct!(push_eq '=');
push_punct!(push_eq_eq '=' '=');
push_punct!(push_ge '>' '=');
push_punct!(push_gt '>');
push_punct!(push_le '<' '=');
push_punct!(push_lt '<');
push_punct!(push_mul_eq '*' '=');
push_punct!(push_ne '!' '=');
push_punct!(push_or '|');
push_punct!(push_or_eq '|' '=');
push_punct!(push_or_or '|' '|');
push_punct!(push_pound '#');
push_punct!(push_question '?');
push_punct!(push_rarrow '-' '>');
push_punct!(push_larrow '<' '-');
push_punct!(push_rem '%');
push_punct!(push_rem_eq '%' '=');
push_punct!(push_fat_arrow '=' '>');
push_punct!(push_semi ';');
push_punct!(push_shl '<' '<');
push_punct!(push_shl_eq '<' '<' '=');
push_punct!(push_shr '>' '>');
push_punct!(push_shr_eq '>' '>' '=');
push_punct!(push_star '*');
push_punct!(push_sub '-');
push_punct!(push_sub_eq '-' '=');

// Helper method for constructing identifiers from the `format_ident!` macro,
// handling `r#` prefixes.
//
// Directly parsing the input string may produce a valid identifier,
// although the input string was invalid, due to ignored characters such as
// whitespace and comments. Instead, we always create a non-raw identifier
// to validate that the string is OK, and only parse again if needed.
//
// The `is_ident` method defined above is insufficient for validation, as it
// will reject non-ASCII identifiers.
pub fn mk_ident(id: &str, span: Option<Span>) -> Ident {
    let span = span.unwrap_or_else(Span::call_site);

    let is_raw = id.starts_with("r#");
    let unraw = Ident::new(if is_raw { &id[2..] } else { id }, span);
    if !is_raw {
        return unraw;
    }

    // At this point, the identifier is raw, and the unraw-ed version of it was
    // successfully converted into an identifier. Try to produce a valid raw
    // identifier by running the `TokenStream` parser, and unwrapping the first
    // token as an `Ident`.
    //
    // FIXME: When `Ident::new_raw` becomes stable, this method should be
    // updated to call it when available.
    match id.parse::<TokenStream>() {
        Ok(ts) => {
            let mut iter = ts.into_iter();
            match (iter.next(), iter.next()) {
                (Some(TokenTree::Ident(mut id)), None) => {
                    id.set_span(span);
                    id
                }
                _ => unreachable!("valid raw ident fails to parse"),
            }
        }
        Err(_) => unreachable!("valid raw ident fails to parse"),
    }
}

// Adapts from `IdentFragment` to `fmt::Display` for use by the `format_ident!`
// macro, and exposes span information from these fragments.
//
// This struct also has forwarding implementations of the formatting traits
// `Octal`, `LowerHex`, `UpperHex`, and `Binary` to allow for their use within
// `format_ident!`.
#[derive(Copy, Clone)]
pub struct IdentFragmentAdapter<T: IdentFragment>(pub T);

impl<T: IdentFragment> IdentFragmentAdapter<T> {
    pub fn span(&self) -> Option<Span> {
        self.0.span()
    }
}

impl<T: IdentFragment> fmt::Display for IdentFragmentAdapter<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        IdentFragment::fmt(&self.0, f)
    }
}

impl<T: IdentFragment + fmt::Octal> fmt::Octal for IdentFragmentAdapter<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Octal::fmt(&self.0, f)
    }
}

impl<T: IdentFragment + fmt::LowerHex> fmt::LowerHex for IdentFragmentAdapter<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::LowerHex::fmt(&self.0, f)
    }
}

impl<T: IdentFragment + fmt::UpperHex> fmt::UpperHex for IdentFragmentAdapter<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::UpperHex::fmt(&self.0, f)
    }
}

impl<T: IdentFragment + fmt::Binary> fmt::Binary for IdentFragmentAdapter<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Binary::fmt(&self.0, f)
    }
}