use lib::fmt;

use error::{ParseError, StreamError};
use stream::{FullRangeStream, IteratorStream, Positioned, RangeStreamOnce, Resetable, SliceStream,
             StreamErrorFor, StreamOnce};

#[cfg(feature = "std")]
use stream::ReadStream;

/// Trait for tracking the current position of a `Stream`.
pub trait Positioner<Item> {
    /// The type which keeps track of the position
    type Position: Clone + Ord;
    /// Returns the current position
    fn position(&self) -> Self::Position;
    /// Updates the position given that `item` has been taken from the stream
    fn update(&mut self, item: &Item);
}

/// Trait for tracking the current position of a `RangeStream`.
pub trait RangePositioner<Item, Range>: Positioner<Item> {
    /// Updates the position given that `range` has been taken from the stream
    fn update_range(&mut self, range: &Range);
}

/// Defines a default `Positioner` type for a particular `Stream` type.
pub trait DefaultPositioned {
    type Positioner: Default;
}

impl<'a> DefaultPositioned for &'a str {
    type Positioner = SourcePosition;
}

impl<'a, T> DefaultPositioned for &'a [T] {
    type Positioner = IndexPositioner;
}

impl<'a, T> DefaultPositioned for SliceStream<'a, T> {
    type Positioner = IndexPositioner;
}

impl<T> DefaultPositioned for IteratorStream<T> {
    type Positioner = IndexPositioner;
}

#[cfg(feature = "std")]
impl<R> DefaultPositioned for ReadStream<R> {
    type Positioner = IndexPositioner;
}

/// The `State<I>` struct maintains the current position in the stream `I` using
/// the `Positioner` trait to track the position.
///
/// ```
/// # #![cfg(feature = "std")]
/// # extern crate combine;
/// # use combine::{token, Parser};
/// # use combine::stream::easy;
/// # use combine::stream::state::State;
/// # fn main() {
///     let result = token(b'9')
///         .message("Not a nine")
///         .easy_parse(State::new(&b"8"[..]));
///     assert_eq!(result, Err(easy::Errors {
///         position: 0,
///         errors: vec![
///             easy::Error::Unexpected(b'8'.into()),
///             easy::Error::Expected(b'9'.into()),
///             easy::Error::Message("Not a nine".into())
///         ]
///     }));
/// # }
/// ```
#[derive(Clone, Debug, PartialEq)]
pub struct State<I, X> {
    /// The input stream used when items are requested
    pub input: I,
    /// The positioner used to update the current position
    pub positioner: X,
}

impl<I, X> State<I, X>
where
    I: StreamOnce,
    X: Positioner<I::Item>,
{
    /// Creates a new `State<I, X>` from an input stream and a positioner.
    pub fn with_positioner(input: I, positioner: X) -> State<I, X> {
        State { input, positioner }
    }
}

impl<I> State<I, I::Positioner>
where
    I: StreamOnce + DefaultPositioned,
    I::Positioner: Positioner<I::Item>,
{
    /// Creates a new `State<I, X>` from an input stream and its default positioner.
    pub fn new(input: I) -> State<I, I::Positioner> {
        State::with_positioner(input, I::Positioner::default())
    }
}

impl<I, X, E> Positioned for State<I, X>
where
    I: StreamOnce,
    X: Positioner<I::Item>,
    E: StreamError<I::Item, I::Range>,
    I::Error: ParseError<I::Item, I::Range, X::Position, StreamError = E>,
    I::Error: ParseError<I::Item, I::Range, I::Position, StreamError = E>,
{
    #[inline(always)]
    fn position(&self) -> Self::Position {
        self.positioner.position()
    }
}

impl<I, X, S> StreamOnce for State<I, X>
where
    I: StreamOnce,
    X: Positioner<I::Item>,
    S: StreamError<I::Item, I::Range>,
    I::Error: ParseError<I::Item, I::Range, X::Position, StreamError = S>,
    I::Error: ParseError<I::Item, I::Range, I::Position, StreamError = S>,
{
    type Item = I::Item;
    type Range = I::Range;
    type Position = X::Position;
    type Error = I::Error;

    #[inline]
    fn uncons(&mut self) -> Result<I::Item, StreamErrorFor<Self>> {
        self.input.uncons().map(|c| {
            self.positioner.update(&c);
            c
        })
    }
}

/// The `IndexPositioner<Item, Range>` struct maintains the current index into the stream `I`.  The
/// initial index is index 0.  Each `Item` consumed increments the index by 1; each `range` consumed
/// increments the position by `range.len()`.
#[derive(Clone, Debug, Default, PartialEq)]
pub struct IndexPositioner(usize);

clone_resetable!{ () IndexPositioner }

impl<Item> Positioner<Item> for IndexPositioner
where
    Item: PartialEq + Clone,
{
    type Position = usize;

    #[inline(always)]
    fn position(&self) -> usize {
        self.0
    }

    #[inline]
    fn update(&mut self, _item: &Item) {
        self.0 += 1
    }
}

impl IndexPositioner {
    pub fn new() -> IndexPositioner {
        IndexPositioner::new_with_position(0)
    }

    pub fn new_with_position(position: usize) -> IndexPositioner {
        IndexPositioner(position)
    }
}

impl<Item, Range> RangePositioner<Item, Range> for IndexPositioner
where
    Item: PartialEq + Clone,
    Range: PartialEq + Clone + ::stream::Range,
{
    fn update_range(&mut self, range: &Range) {
        self.0 += range.len()
    }
}

/// Struct which represents a position in a source file.
#[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd)]
pub struct SourcePosition {
    /// Current line of the input
    pub line: i32,
    /// Current column of the input
    pub column: i32,
}

clone_resetable!{ () SourcePosition }

impl Default for SourcePosition {
    fn default() -> Self {
        SourcePosition { line: 1, column: 1 }
    }
}

impl fmt::Display for SourcePosition {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "line: {}, column: {}", self.line, self.column)
    }
}

impl SourcePosition {
    pub fn new() -> Self {
        SourcePosition::default()
    }
}

impl Positioner<char> for SourcePosition {
    type Position = SourcePosition;

    #[inline(always)]
    fn position(&self) -> SourcePosition {
        self.clone()
    }

    #[inline]
    fn update(&mut self, item: &char) {
        self.column += 1;
        if *item == '\n' {
            self.column = 1;
            self.line += 1;
        }
    }
}

impl<'a> RangePositioner<char, &'a str> for SourcePosition {
    fn update_range(&mut self, range: &&'a str) {
        for c in range.chars() {
            self.update(&c);
        }
    }
}

impl<I, X, S> RangeStreamOnce for State<I, X>
where
    I: RangeStreamOnce,
    X: Resetable + RangePositioner<I::Item, I::Range>,
    S: StreamError<I::Item, I::Range>,
    I::Error: ParseError<I::Item, I::Range, X::Position, StreamError = S>,
    I::Error: ParseError<I::Item, I::Range, I::Position, StreamError = S>,
    I::Position: Clone + Ord,
{
    #[inline]
    fn uncons_range(&mut self, size: usize) -> Result<I::Range, StreamErrorFor<Self>> {
        self.input.uncons_range(size).map(|range| {
            self.positioner.update_range(&range);
            range
        })
    }

    #[inline]
    fn uncons_while<F>(&mut self, mut predicate: F) -> Result<I::Range, StreamErrorFor<Self>>
    where
        F: FnMut(I::Item) -> bool,
    {
        let positioner = &mut self.positioner;
        self.input.uncons_while(|t| {
            if predicate(t.clone()) {
                positioner.update(&t);
                true
            } else {
                false
            }
        })
    }

    #[inline]
    fn distance(&self, end: &Self::Checkpoint) -> usize {
        self.input.distance(&end.input)
    }
}

impl<I, X> Resetable for State<I, X>
where
    I: Resetable,
    X: Resetable,
{
    type Checkpoint = State<I::Checkpoint, X::Checkpoint>;
    fn checkpoint(&self) -> Self::Checkpoint {
        State {
            input: self.input.checkpoint(),
            positioner: self.positioner.checkpoint(),
        }
    }
    fn reset(&mut self, checkpoint: Self::Checkpoint) {
        self.input.reset(checkpoint.input);
        self.positioner.reset(checkpoint.positioner);
    }
}

impl<I, X, E> FullRangeStream for State<I, X>
where
    I: FullRangeStream + Resetable,
    I::Position: Clone + Ord,
    E: StreamError<I::Item, I::Range>,
    I::Error: ParseError<I::Item, I::Range, X::Position, StreamError = E>,
    I::Error: ParseError<I::Item, I::Range, I::Position, StreamError = E>,
    X: Resetable + RangePositioner<I::Item, I::Range>,
{
    fn range(&self) -> Self::Range {
        self.input.range()
    }
}

#[cfg(all(feature = "std", test))]
mod tests {
    use super::*;
    use Parser;

    #[test]
    fn test_positioner() {
        let input = ["a".to_string(), "b".to_string()];
        let mut parser = ::any();
        let result = parser.parse(State::new(&input[..]));
        assert_eq!(
            result,
            Ok((
                "a".to_string(),
                State::with_positioner(
                    &["b".to_string()][..],
                    IndexPositioner::new_with_position(1)
                )
            ))
        );
    }

    #[test]
    fn test_range_positioner() {
        let input = ["a".to_string(), "b".to_string(), "c".to_string()];
        let mut parser = ::parser::range::take(2);
        let result = parser.parse(State::new(&input[..]));
        assert_eq!(
            result,
            Ok((
                &["a".to_string(), "b".to_string()][..],
                State::with_positioner(
                    &["c".to_string()][..],
                    IndexPositioner::new_with_position(2)
                )
            ))
        );
    }
}