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#![doc(html_root_url = "https://docs.rs/col_proc_macros_impl/0.1.0/")]

//! Implementation crate of macros built with the [`proc_macro_hack`],see the declaration crate
//! [`col_proc_macros`](https://docs.rs/col_proc_macros/0.1.0/).

extern crate proc_macro;

use core::fmt::Write;
use core::ptr;
use proc_macro::TokenStream;
use proc_macro_hack::proc_macro_hack;
use unicode_xid::UnicodeXID;

#[proc_macro_hack]
pub fn vector(input: TokenStream) -> TokenStream {
    // code expanded after the contents of the array
    static CODE: &str = "]);\
let mut temp_vec = Vector::with_capacity(arr.len());\
core::ptr::copy_nonoverlapping(arr.as_ptr(), temp_vec.as_mut_ptr(), arr.len());\
temp_vec.set_len(arr.len());\
temp_vec\
}";

    let input = input.to_string();
    let input_t = input.trim();

    let mut delimiters_count = 0;
    let mut expansion = String::with_capacity(512);

    expansion.push_str(
        "unsafe {\
let arr = core::mem::ManuallyDrop::new([",
    );

    if let Some(i) = input_t.find(|c: char| {
        if c == '[' || c == '{' || c == '(' || c == '<' {
            delimiters_count += 1;
            return false;
        }

        if c == ']' || c == '}' || c == ')' || c == '>' {
            delimiters_count -= 1;
            return false;
        }

        delimiters_count == 0 && c == ';'
    }) {
        let elem = (&input_t[..i]).trim();
        let wheels = (&input_t[i + 1..])
            .trim()
            .parse::<usize>()
            .expect("The length it's not a valid usize");

        if wheels > 0 {
            let mut b = false;

            // this checks if the element it's not an identifier actually this is pretty is strict and
            // does not take in count macros as `concat_idents`,at the time there's no other standard solution
            // to return identifiers so this is fine.
            if elem
                .find(|c: char| if b {
                            !c.is_xid_continue()
                        } else {
                            b = true;
                            !c.is_xid_start()
                        }
                )
                .is_some()
            {
                expansion.reserve_exact((wheels * (elem.len() + 1)).next_power_of_two());

                for _ in 0..wheels {
                    write!(expansion, "{},", elem).unwrap()
                }
            } else {
                expansion.reserve_exact((wheels * (elem.len() + 9)).next_power_of_two());

                for _ in 1..wheels {
                    write!(expansion, "{}.clone(),", elem).unwrap()
                }

                expansion.push_str(elem);
            }
        }
    } else {
        for mut e in input_t.split(|c: char| {
            if c == '[' || c == '{' || c == '(' || c == '<' {
                delimiters_count += 1;
                return false;
            }

            if c == ']' || c == '}' || c == ')' || c == '>' {
                delimiters_count -= 1;
                return false;
            }

            delimiters_count == 0 && c == ','
        }) {
            e = e.trim();

            if e != "" {
                write!(expansion, "{},", e).unwrap();
            }
        }
    }

    // removing the last comma for rigth find the pen-last later and avoid traversing the entire string
    if expansion.ends_with(',') {
        let len = expansion.len();

        // it's verbose saying a comma it's one-byte character,here goes anyways
        unsafe {
            ptr::drop_in_place(expansion.as_mut_vec().as_mut_ptr().add(len));
            expansion.as_mut_vec().set_len(len - 1);
        }
    }

    if let Some(i) = expansion.rfind(|c: char| {
        if c == '[' || c == '{' || c == '(' || c == '<' {
            delimiters_count += 1;
            return false;
        }

        if c == ']' || c == '}' || c == ')' || c == '>' {
            delimiters_count -= 1;
            return false;
        }

        delimiters_count == 0 && (c == ':' || c == ',')
    }) {
        if expansion.as_bytes()[i] == b':' {
            let index = input.len() - expansion[i..].len() + 1;

            unsafe {
                // SAFETY: `i` it's known to be a valid char boundary
                expansion.as_mut_vec().truncate(i)
            }

            write!(
                expansion,
                "]);\
let mut temp_vec = <Vector<{}>>::with_capacity(arr.len());\
core::ptr::copy_nonoverlapping(arr.as_ptr(), temp_vec.as_mut_ptr(), arr.len());\
temp_vec.set_len(arr.len());\
temp_vec\
}}",
                unsafe { input.get_unchecked(index..) }
            )
            .unwrap();
        } else {
            expansion.push_str(CODE);
        }
    } else {
        expansion.push_str(CODE);
    }

    expansion.parse().unwrap()
}