use crate::buffer::BufferID;
use crate::selection::{Interval, 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()),
            }
        }
    };
}

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

// ----------------------------------------------------------------
pub fn complement_transform(es: &EditorState, result: Selection, _: &SFArguments) -> SFResult {
    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))
        }
    }

    result.vectorise(es, complement_rank0, complement_rank1)
}

pub fn conditional_transform(
    _: &EditorState,
    mut result: Selection,
    arg: &SFArguments,
) -> SFResult {
    if !result.is_empty() {
        Ok(match arg {
            // TODO: think about this niladic case?
            SFArguments::Niladic { .. } => Selection::empty(),
            SFArguments::Monadic { es: _, left } => left.clone(),
            SFArguments::Dyadic {
                es: _,
                left,
                right: _,
            } => left.clone(),
        })
    } else {
        Ok(result)
    }
}

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

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,
        })
}

selection_function_param! {
    name: character_structural,
    param_type: usize,
    niladic: |(param, es): (usize, &EditorState)| {
        if let Some(buf) = es.current_buffer() {
                Ok(Selection::Position {
                    buffer_id: es.current_buffer_id,
                    pos: usize::min(param, 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: |(param, _), buffer_id, int| Ok(Selection::Position {buffer_id, pos: usize::min(int.end, *param)})
}

selection_function_param! {
    name: character_sequential,
    param_type: usize,
    niladic: |(param, es): (usize, &EditorState)| {
        if let Some(buf) = es.current_buffer() {
                Ok(Selection::Position {
                    buffer_id: es.current_buffer_id,
                    pos: usize::min(param, buf.max_pos()),
                })
            } else {
                Err(SFError::BufferNotFound(es.current_buffer_id).into())
            }
    },
    monadic_rank0: |(param, es), buffer_id, pos| {
        if let Some(buf) = es.get_buffer(buffer_id) {
            Ok(Selection::Position {buffer_id, pos: usize::min(pos+*param, buf.max_pos())})
        } else {
            Err(SFError::BufferNotFound(buffer_id).into())
        }
    },
    monadic_rank1: |(param, es), buffer_id, int| {
        if let Some(buf) = es.get_buffer(buffer_id) {
            Ok(Selection::Position {buffer_id, pos: usize::min(int.end+*param, buf.max_pos())})
        } else {
            Err(SFError::BufferNotFound(buffer_id).into())
        }
    }
}