use crate::buffer::BufferID;
use crate::selection::{Selection, VectoriseError};
use crate::state::EditorState;
use thiserror::Error;

#[derive(Error, Debug)]
pub enum SFError {
    #[error("Could not find buffer {0}")]
    BufferNotFound(BufferID),
    #[error("Function {0} has no dyadic form")]
    NoDyadicForm(&'static str),
}

pub enum SFArguments<'a> {
    Niladic {
        es: &'a EditorState,
    },
    Monadic {
        es: &'a EditorState,
        left: Selection,
    },
    Dyadic {
        es: &'a EditorState,
        left: Selection,
        right: Selection,
    },
}

type SFResult = Result<Selection, VectoriseError<SFError>>;

fn rust_has_an_annoying_issue(r: Result<Selection, SFError>) -> SFResult {
    r.map_err(Into::into)
}

macro_rules! selection_function {
    (
        name: $name:ident,
        niladic: $niladic_body:expr,
        monadic_rank0: $monadic_rank0_body:expr,
        monadic_rank1: $monadic_rank1_body:expr
    ) => {
        pub fn $name(arg: SFArguments) -> SFResult {
            match arg {
                SFArguments::Niladic { es } => rust_has_an_annoying_issue({ $niladic_body(es) }),
                SFArguments::Monadic { es, left } => {
                    left.vectorise(es, $monadic_rank0_body, $monadic_rank1_body)
                }
                SFArguments::Dyadic { .. } => Err(SFError::NoDyadicForm(stringify!($name)).into()),
            }
        }
    };
}

// ----------------------------------------------------------------

pub fn empty_sequential(_: SFArguments) -> SFResult {
    Ok(Selection::empty())
}

pub fn empy_structural(_: SFArguments) -> SFResult {
    Ok(Selection::empty())
}

selection_function! {
    name: end_sequential,
    niladic: |es: &EditorState| {
        es.current_buffer().map(|buf| Selection::Position {
            buffer_id: es.current_buffer_id,
            pos: buf.max_pos()
        }).ok_or(SFError::BufferNotFound(es.current_buffer_id))
    },
    monadic_rank0: |_, buffer_id, pos| {
        Ok(Selection::Position { buffer_id, pos })
    },
    monadic_rank1: |_, buffer_id, interval| {
        Ok(Selection::Position {
            buffer_id,
            pos: interval.end,
        })
    }
}

selection_function! {
    name: end_structural,
    niladic: |es: &EditorState| {
            if let Some(buf) = es.current_buffer() {
                Ok(Selection::Position {
                    buffer_id: es.current_buffer_id,
                    pos: buf.max_pos(),
                })
            } else {
                Err(SFError::BufferNotFound(es.current_buffer_id).into())
            }
    },
    monadic_rank0: |_, buffer_id, pos | Ok(Selection::Position { buffer_id, pos }),
    monadic_rank1: |_, buffer_id, int |         Ok(Selection::Position {
            buffer_id,
            pos: int.end,
        })
}

// pub fn transform_conditional(sf: Self) -> Self {
//     fn condition(mut pred: Selection, res: Selection) -> Selection {
//         if pred.is_empty() {
//             pred
//         } else {
//             res
//         }
//     }

//     let dyadic: Option<Box<dyn Fn(&EditorState, &Selection, &Selection) -> Result<_, _>>> =
//         if let Some(dyadic) = sf.dyadic {
//             Some(Box::new(move |es, left, right| {
//                 Ok(condition((dyadic)(es, left, right)?, left.clone()))
//             }))
//         } else {
//             None
//         };

//     let monadic: Box<dyn Fn(&EditorState, &Selection) -> Result<_, _>> =
//         Box::new(move |es, left| Ok(condition((sf.monadic)(es, left)?, left.clone())));

//     SelectionFunction {
//         niladic: sf.niladic,
//         monadic,
//         dyadic,
//     }
// }

// pub fn complement_transform(sf: Self) -> Self {
//     fn complement_rank0(
//         es: &EditorState,
//         buffer_id: BufferID,
//         pos: usize,
//     ) -> Result<Selection, SFError> {
//         if let Some(buf) = es.get_buffer(buffer_id) {
//             let mut ranges = Vec::new();
//             if pos > 0 {
//                 ranges.push(Interval::new(0, pos));
//             }
//             let max_pos = buf.max_pos();
//             if pos + 1 < max_pos {
//                 ranges.push(Interval::new(pos + 1, max_pos));
//             }
//             Ok(Selection::Ranges { buffer_id, ranges })
//         } else {
//             Err(SFError::BufferNotFound(buffer_id))
//         }
//     }

//     fn complement_rank1(
//         es: &EditorState,
//         buffer_id: BufferID,
//         interval: &Interval,
//     ) -> Result<Selection, SFError> {
//         if let Some(buf) = es.get_buffer(buffer_id) {
//             let max_pos = buf.max_pos();
//             if interval.start == 0 && interval.end >= max_pos {
//                 return Ok(Selection::empty());
//             }

//             let mut ranges = Vec::new();
//             if interval.start == 0 {
//                 if interval.end < max_pos {
//                     ranges.push(Interval::new(interval.end, max_pos));
//                 }
//             } else if interval.end == max_pos {
//                 ranges.push(Interval::new(0, interval.start));
//             } else {
//                 ranges.push(Interval::new(0, interval.start));
//                 ranges.push(Interval::new(interval.end, max_pos));
//             }
//             Ok(Selection::Ranges { buffer_id, ranges })
//         } else {
//             Err(SFError::BufferNotFound(buffer_id))
//         }
//     }

//     fn complement(
//         es: &EditorState,
//         selection: Selection,
//     ) -> Result<Selection, VectoriseError<SFError>> {
//         Selection::vectorise(complement_rank0, complement_rank1, es, &selection)
//     }

//     let dyadic: Option<Box<dyn Fn(&EditorState, &Selection, &Selection) -> Result<_, _>>> =
//         if let Some(dyadic) = sf.dyadic {
//             Some(Box::new(move |es, left, right| {
//                 complement(es, (dyadic)(es, left, right)?)
//             }))
//         } else {
//             None
//         };

//     let monadic: Box<dyn Fn(&EditorState, &Selection) -> Result<_, _>> =
//         Box::new(move |es, left| complement(es, (sf.monadic)(es, left)?));

//     let niladic: Box<dyn Fn(&EditorState) -> Result<_, _>> =
//         Box::new(move |es| complement(es, (sf.niladic)(es)?));

//     SelectionFunction {
//         niladic,
//         monadic,
//         dyadic,
//     }
// }