//#![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)]
extern crate const_panic;
use const_panic::PanicFmt;
use std::fmt::Debug;
pub(crate) use std::{error::Error, sync::Arc};
pub(crate) use konst::{iter::for_each, string::{str_from, str_range, char_indices}};
pub(crate) use thiserror::Error;
pub(crate) use ::tengri_core::*;
pub(crate) use self::DslError::*;
mod dsl_conv; pub use self::dsl_conv::*;
#[cfg(test)] mod dsl_test;
/// DSL-specific result type.
pub type DslResult<T> = Result<T, DslError>;
/// DSL-specific optional result type.
pub type DslPerhaps<T> = Result<Option<T>, DslError>;
// Some things that can be DSL source:
impl     Dsl for String   { fn src (&self) -> DslPerhaps<&str> { Ok(Some(self.as_ref())) } }
impl     Dsl for Arc<str> { fn src (&self) -> DslPerhaps<&str> { Ok(Some(self.as_ref())) } }
impl<'s> Dsl for &'s str  { fn src (&self) -> DslPerhaps<&str> { Ok(Some(self.as_ref())) } }
// Designates a string as parsable DSL.
flex_trait!(Dsl: Debug + Send + Sync + Sized {
    fn src (&self) -> DslPerhaps<&str> { unreachable!("Dsl::src default impl") }
});
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)}}
}
impl<D: Dsl> DslText for D {} pub trait DslText: Dsl {
    fn text (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(text_peek_only))}
}
impl<D: Dsl> DslSym for D {} pub trait DslSym: Dsl {
    fn sym  (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(sym_peek_only))}
}
impl<D: Dsl> DslKey for D {} pub trait DslKey: Dsl {
    fn key  (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(key_peek_only))}
}
impl<D: Dsl> DslNum for D {} pub trait DslNum: Dsl {
    fn num  (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(num_peek_only))}
}
impl<D: Dsl> DslExp for D {} pub trait DslExp: Dsl {
    fn exp  (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(exp_peek_inner_only))}
    fn head (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(peek))}
    fn tail (&self) -> DslPerhaps<&str> {ok_flat(self.src()?.map(peek_tail))}
    /// my other car is a cdr :<
    fn each (&self, mut cb: impl FnMut(&str)->Usually<()>) -> Usually<()> {
        Ok(if let Some(head) = self.head()? {
            cb(head)?;
            if let Some(tail) = self.tail()? {
                tail.each(cb)?;
            }
        })
    }
}
pub const fn peek (src: &str) -> DslPerhaps<&str> {
    Ok(Some(if let Ok(Some(exp))  = exp_peek(src)  { exp  } else
            if let Ok(Some(sym))  = sym_peek(src)  { sym  } else
            if let Ok(Some(key))  = key_peek(src)  { key  } else
            if let Ok(Some(num))  = num_peek(src)  { num  } 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(exp))  = exp_seek(src)  { exp  } else
            if let Ok(Some(sym))  = sym_seek(src)  { sym  } else
            if let Ok(Some(key))  = key_seek(src)  { key  } else
            if let Ok(Some(num))  = num_seek(src)  { num  } 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)
        },
    }
}
/// DSL-specific error codes.
#[derive(Error, Debug, Copy, Clone, PartialEq, PanicFmt)]
pub enum DslError {
    #[error("parse failed: not implemented")] Unimplemented,
    #[error("parse failed: empty")] Empty,
    #[error("parse failed: incomplete")] Incomplete,
    #[error("parse failed: unexpected character '{0}'")] Unexpected(char, Option<usize>, Option<&'static str>),
    #[error("parse failed: error #{0}")] Code(u8),
    #[error("end reached")] End
}
fn ok_flat <T> (x: Option<DslPerhaps<T>>) -> DslPerhaps<T> { Ok(x.transpose()?.flatten()) }
pub const fn is_space (c: char) -> bool {
    matches!(c, ' '|'\n'|'\r'|'\t')
}
pub const fn no_trailing_non_space (source: &str, offset: usize, context: Option<&'static str>) -> DslResult<()> {
    Ok(for_each!((i, c) in char_indices(str_range(source, offset, source.len())) => if !is_space(c) {
        return Err(Unexpected(c, Some(offset + i), if let Some(context) = context {
            Some(context)
        } else {
            Some("trailing non-space")
        }))
    }))
}
macro_rules! def_peek_seek(($peek:ident, $peek_only:ident, $seek:ident, $seek_start:ident, $seek_length:ident)=>{
    /// 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")) { return Err(e) }
                Ok(Some(str_range(source, start, start + length)))
            }
        }
    }
    /// 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),
            },
        }
    }
});
def_peek_seek!(exp_peek, exp_peek_only, exp_seek, exp_seek_start, exp_seek_length);
pub const fn exp_peek_inner (source: &str) -> DslPerhaps<&str> {
    match exp_peek(source) {
        Ok(Some(peeked)) => {
            let len = peeked.len();
            let start = if len > 0 { 1 } else { 0 };
            Ok(Some(str_range(source, start, start + len.saturating_sub(2))))
        },
        e => e
    }
}
pub const fn exp_peek_inner_only (source: &str) -> DslPerhaps<&str> {
    match exp_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("exp_peek_inner_only")) { return Err(e) }
            let peeked = str_range(source, 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_exp_start (c: char) -> bool { c == '(' }
pub const fn is_exp_end (c: char) -> bool { c == ')' }
pub const fn exp_seek_start (source: &str) -> DslPerhaps<usize> {
    for_each!((i, c) in char_indices(source) => if is_exp_start(c) {
        return Ok(Some(i))
    } else if !is_space(c) {
        return Err(Unexpected(c, Some(i), Some("expected expression start")))
    });
    Ok(None)
}
pub const fn exp_seek_length (source: &str) -> DslPerhaps<usize> {
    let mut depth = 0;
    for_each!((i, c) in char_indices(source) => if is_exp_start(c) {
        depth += 1;
    } else if is_exp_end(c) {
        if depth == 0 {
            return Err(Unexpected(c, Some(i), Some("expected expression end")))
        } else if depth == 1 {
            return Ok(Some(i + 1))
        } else {
            depth -= 1;
        }
    });
    Err(Incomplete)
}
def_peek_seek!(sym_peek, sym_peek_only, sym_seek, sym_seek_start, sym_seek_length);
pub const fn is_sym_start (c: char) -> bool { matches!(c, ':'|'@') }
pub const fn is_sym_char (c: char) -> bool { is_sym_start(c) || matches!(c, 'a'..='z'|'A'..='Z'|'0'..='9'|'-'|'/') }
pub const fn is_sym_end (c: char) -> bool { is_space(c) || matches!(c, ')') }
pub const fn sym_seek_start (source: &str) -> DslPerhaps<usize> {
    for_each!((i, c) in char_indices(source) => if is_sym_start(c) {
        return Ok(Some(i))
    } else if !is_space(c) {
        return Err(Unexpected(c, Some(i), Some("sym_seek_start")))
    });
    Ok(None)
}
pub const fn sym_seek_length (source: &str) -> DslPerhaps<usize> {
    for_each!((i, c) in char_indices(source) => if is_sym_end(c) {
        return Ok(Some(i))
    } else if !is_sym_char(c) {
        return Err(Unexpected(c, Some(i), Some("sym_seek_length")))
    });
    Ok(Some(source.len()))
}
def_peek_seek!(key_peek, key_peek_only, key_seek, key_seek_start, key_seek_length);
pub const fn is_key_start (c: char) -> bool { matches!(c, '/'|('a'..='z')) }
pub const fn is_key_char (c: char) -> bool { matches!(c, 'a'..='z'|'0'..='9'|'-'|'/') }
pub const fn is_key_end (c: char) -> bool { is_space(c) || matches!(c, ')') }
pub const fn key_seek_start (source: &str) -> DslPerhaps<usize> {
    for_each!((i, c) in char_indices(source) => if is_key_start(c) {
        return Ok(Some(i))
    } else if !is_space(c) {
        return Err(Unexpected(c, Some(i), None))
    });
    Ok(None)
}
pub const fn key_seek_length (source: &str) -> DslPerhaps<usize> {
    for_each!((i, c) in char_indices(source) => if is_key_end(c) {
        return Ok(Some(i))
    } else if !is_key_char(c) {
        return Err(Unexpected(c, Some(i), None))
    });
    Ok(Some(source.len()))
}
def_peek_seek!(text_peek, text_peek_only, text_seek, text_seek_start, text_seek_length);
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 text_seek_start (source: &str) -> DslPerhaps<usize> {
    for_each!((i, c) in char_indices(source) => if is_text_start(c) {
        return Ok(Some(i))
    } else if !is_space(c) {
        return Err(Unexpected(c, Some(i), None))
    });
    Ok(None)
}
pub const fn text_seek_length (source: &str) -> DslPerhaps<usize> {
    for_each!((i, c) in char_indices(source) => if is_text_end(c) { return Ok(Some(i)) });
    Ok(None)
}
def_peek_seek!(num_peek, num_peek_only, num_seek, num_seek_start, num_seek_length);
pub const fn num_seek_start (source: &str) -> DslPerhaps<usize> {
    for_each!((i, c) in char_indices(source) => if is_digit(c) {
        return Ok(Some(i));
    } else if !is_space(c) {
        return Err(Unexpected(c, Some(i), None))
    });
    Ok(None)
}
pub const fn num_seek_length (source: &str) -> DslPerhaps<usize> {
    for_each!((i, c) in char_indices(source) => if is_num_end(c) {
        return Ok(Some(i))
    } else if !is_digit(c) {
        return Err(Unexpected(c, Some(i), None))
    });
    Ok(None)
}
pub const fn is_digit (c: char) -> bool { matches!(c, '0'..='9') }
pub const fn is_num_end (c: char) -> bool { matches!(c, ' '|'\n'|'\r'|'\t'|')') }
pub const fn to_number <D: Dsl> (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")))
    })
}