//#![feature(adt_const_params)]
//#![feature(type_alias_impl_trait)]
#![feature(if_let_guard)]
#![feature(impl_trait_in_fn_trait_return)]
#![feature(const_precise_live_drops)]
#![feature(type_alias_impl_trait)]
extern crate const_panic;
use const_panic::PanicFmt;
use std::fmt::Debug;
pub(crate) use ::{
    std::sync::Arc,
    std::error::Error,
    konst::iter::for_each,
    konst::string::{str_from, str_range, char_indices},
    thiserror::Error,
    tengri_core::*
};
pub(crate) use self::DslError::*;
mod dsl_error; pub use self::dsl_error::*;
mod dsl_ns;    pub use self::dsl_ns::*;
mod dsl_word;  pub use self::dsl_word::*;
mod dsl_expr;  pub use self::dsl_expr::*;
mod dsl_text;  pub use self::dsl_text::*;
#[cfg(test)] mod dsl_test;

// Trait that designates any string-like as potentially parsable DSL.
pub trait Dsl: Debug + Send + Sync {
    fn src (&self) -> DslPerhaps<&str> { unreachable!("Dsl::src default impl") }
}
impl<'x> Dsl for &'x str {
    fn src (&self) -> DslPerhaps<&str> { Ok(Some(self)) }
}
impl Dsl for Arc<str> {
    fn src (&self) -> DslPerhaps<&str> { Ok(Some(self.as_ref())) }
}
impl<D: Dsl> Dsl for &D {
    fn src (&self) -> DslPerhaps<&str> { (*self).src() }
}
impl<D: Dsl> Dsl for &mut D {
    fn src (&self) -> DslPerhaps<&str> { (**self).src() }
}
impl<D: Dsl> Dsl for Option<D> {
    fn src (&self) -> DslPerhaps<&str> {Ok(if let Some(dsl) = self { dsl.src()? } else { None })}
}
impl<D: Dsl> Dsl for Result<D, DslError> {
    fn src (&self) -> DslPerhaps<&str> {match self {Ok(dsl) => Ok(dsl.src()?), Err(e) => Err(*e)}}
}

/// DSL-specific result type.
pub type DslResult<T> = Result<T, DslError>;

/// DSL-specific optional result type.
pub type DslPerhaps<T> = Result<Option<T>, DslError>;

pub const fn peek (src: &str) -> DslPerhaps<&str> {
    Ok(Some(if let Ok(Some(expr)) = expr_peek(src) { expr } else
            if let Ok(Some(word)) = word_peek(src) { word } else
            if let Ok(Some(text)) = text_peek(src) { text } else
            if let Err(e) = no_trailing_non_space(src, 0, Some("peek")) { return Err(e) }
            else { return Ok(None) }))
}

pub const fn seek (src: &str) -> DslPerhaps<(usize, usize)> {
    Ok(Some(if let Ok(Some(expr)) = expr_seek(src) { expr } else
            if let Ok(Some(word)) = word_seek(src) { word } else
            if let Ok(Some(text)) = text_seek(src) { text } else
            if let Err(e) = no_trailing_non_space(src, 0, Some("seek")) { return Err(e) }
            else { return Ok(None) }))
}

pub const fn peek_tail (src: &str) -> DslPerhaps<&str> {
    match seek(src) {
        Err(e) => Err(e),
        Ok(None) => Ok(None),
        Ok(Some((start, length))) => {
            let tail = str_range(src, start + length, src.len());
            for_each!((_i, c) in char_indices(tail) => if !is_space(c) { return Ok(Some(tail)) });
            Ok(None)
        },
    }
}

pub const fn expr_peek_inner (src: &str) -> DslPerhaps<&str> {
    match expr_peek(src) {
        Ok(Some(peeked)) => {
            let len = peeked.len();
            let start = if len > 0 { 1 } else { 0 };
            Ok(Some(str_range(src, start, start + len.saturating_sub(2))))
        },
        e => e
    }
}

pub const fn expr_peek_inner_only (src: &str) -> DslPerhaps<&str> {
    match expr_seek(src) {
        Err(e) => Err(e),
        Ok(None) => Ok(None),
        Ok(Some((start, length))) => {
            if let Err(e) = no_trailing_non_space(src, start + length, Some("expr_peek_inner_only")) {
                Err(e)
            } else {
                let peeked = str_range(src, start, start + length);
                let len = peeked.len();
                let start = if len > 0 { 1 } else { 0 };
                Ok(Some(str_range(peeked, start, start + len.saturating_sub(2))))
            }
        },
    }
}

pub const fn is_space (c: char) -> bool {
    matches!(c, ' '|'\n'|'\r'|'\t')
}

pub const fn no_trailing_non_space (
    src: &str, offset: usize, context: Option<&'static str>
) -> DslResult<()> {
    Ok(for_each!((i, c) in char_indices(str_range(src, offset, src.len())) => if !is_space(c) {
        return Err(Unexpected(c, Some(offset + i), if let Some(context) = context {
            Some(context)
        } else {
            Some("trailing non-space")
        }))
    }))
}

pub const fn is_word_char (c: char) -> bool {
    matches!(c, 'a'..='z'|'A'..='Z'|'0'..='9'|'-'|'/'|'@'|':')
}

pub const fn is_word_end (c: char) -> bool {
    is_space(c) || is_expr_end(c)
}

pub const fn is_text_start (c: char) -> bool {
    matches!(c, '"')
}

pub const fn is_text_end (c: char) -> bool {
    matches!(c, '"')
}

pub const fn is_expr_start (c: char) -> bool {
    c == '('
}

pub const fn is_expr_end (c: char) -> bool {
    c == ')'
}

pub const fn is_digit (c: char) -> bool {
    matches!(c, '0'..='9')
}

pub const fn to_number (digits: &str) -> Result<usize, DslError> {
    let mut iter = char_indices(digits);
    let mut value = 0;
    while let Some(((_, c), next)) = iter.next() {
        match to_digit(c) {
            Ok(digit) => value = 10 * value + digit,
            Err(e) => return Err(e),
        }
        iter = next;
    }
    Ok(value)
}

pub const fn to_digit (c: char) -> Result<usize, DslError> {
    Ok(match c {
        '0' => 0, '1' => 1, '2' => 2, '3' => 3, '4' => 4,
        '5' => 5, '6' => 6, '7' => 7, '8' => 8, '9' => 9,
        _ => return Err(Unexpected(c, None, Some("parse digit")))
    })
}

pub(crate) fn ok_flat <T> (x: Option<DslPerhaps<T>>) -> DslPerhaps<T> {
    Ok(x.transpose()?.flatten())
}

#[macro_export] macro_rules! dsl_type (($T:ident { $($trait:tt)* } {
    pub const fn $peek:ident      $($_1:tt)?;
    pub const fn $peek_only:ident $($_2:tt)?;
    pub const fn $seek:ident      $($_3:tt)?;
    pub const fn $seek_start:ident  ($source1:ident) $body1:block
    pub const fn $seek_length:ident ($source2:ident) $body2:block
})=>{
    pub trait $T: Dsl { $($trait)* }
    impl<D: Dsl + ?Sized> $T for D {}
    pub const fn $seek_start  ($source1: &str) -> DslPerhaps<usize> $body1
    pub const fn $seek_length ($source2: &str) -> DslPerhaps<usize> $body2
    /// Find a start and length corresponding to a syntax token.
    pub const fn $seek (source: &str) -> DslPerhaps<(usize, usize)> {
        match $seek_start(source) {
            Err(e) => Err(e),
            Ok(None) => Ok(None),
            Ok(Some(start)) => match $seek_length(str_from(source, start)) {
                Ok(Some(length)) => Ok(Some((start, length))),
                Ok(None) => Ok(None),
                Err(e) => Err(e),
            },
        }
    }
    /// Find a slice corrensponding to a syntax token.
    pub const fn $peek (source: &str) -> DslPerhaps<&str> {
        match $seek(source) {
            Err(e) => Err(e),
            Ok(None) => Ok(None),
            Ok(Some((start, length))) => Ok(Some(str_range(source, start, start + length))),
        }
    }
    /// Find a slice corrensponding to a syntax token
    /// but return an error if it isn't the only thing
    /// in the source.
    pub const fn $peek_only (source: &str) -> DslPerhaps<&str> {
        match $seek(source) {
            Err(e) => Err(e),
            Ok(None) => Ok(None),
            Ok(Some((start, length))) => {
                if let Err(e) = no_trailing_non_space(source, start + length, Some("peek_only")) {
                    Err(e)
                } else {
                    Ok(Some(str_range(source, start, start + length)))
                }
            }
        }
    }
});

#[deprecated]
/// `T` + [Dsl] -> `Self`.
pub trait FromDsl<T>: Sized {
    fn from_dsl (state: &T, dsl: &impl Dsl) -> Perhaps<Self>;
    fn from_dsl_or (state: &T, dsl: &impl Dsl, err: Box<dyn Error>) -> Usually<Self> {
        Self::from_dsl(state, dsl)?.ok_or(err)
    }
    fn from_dsl_or_else (state: &T, dsl: &impl Dsl, err: impl Fn()->Box<dyn Error>) -> Usually<Self> {
        Self::from_dsl(state, dsl)?.ok_or_else(err)
    }
}

#[deprecated]
/// `self` + [Dsl] -> `T`
pub trait DslInto<T> {
    fn dsl_into (&self, dsl: &impl Dsl) -> Perhaps<T>;
    fn dsl_into_or (&self, dsl: &impl Dsl, err: Box<dyn Error>) -> Usually<T> {
        self.dsl_into(dsl)?.ok_or(err)
    }
    fn dsl_into_or_else (&self, dsl: &impl Dsl, err: impl Fn()->Box<dyn Error>) -> Usually<T> {
        self.dsl_into(dsl)?.ok_or_else(err)
    }
}