#![doc(html_root_url = "https://docs.rs/compile_ops/0.1.3/")]
#![no_std]
/*!
This crate provides macros that expand to the result of operations like addition,substraction,division,multiplication or power and a
macro for join them all.

All the macros support exclusion of expressions thought '!' before they,useful when you cannot prevent code
to expand inside the tokens passed;nowadays only possible thought the MBE expansion bucles.

This crate is **no_std**.

# Examples

```
#![feature(proc_macro_hygiene)]

use compile_ops::*;

assert_eq!(2, add!(1!5, !5, 1)); // five it is not invited...
assert_eq!(2, sub!(3, 1));
assert_eq!(2, mul!(2, 1));
assert_eq!(2, div!(4, 2));
assert_eq!(2, rem!(11, 3));

assert_eq!(2, ops!(2 % 2 + 2 * 2 ^ 1 / 1 - 2)); 
```
*/

extern crate proc_macro;
extern crate alloc;

use proc_macro::TokenStream;
use core::hint::unreachable_unchecked;
use alloc::{ string::{String, ToString}, vec::Vec, format };

/// Performs a compile-time addition between comma-separated values,excluding that is prefixed with ! from they.
#[proc_macro]
pub fn add(input: TokenStream) -> TokenStream {
    let input = input.to_string();

    let mut err = String::with_capacity(64);

    let mut it: Vec<String> = input.split(',').map(|e| {
        let mut trigger = false;
        let mut string = String::with_capacity(e.len()+1);

        string.push('0');

        string.extend(e.chars().filter(|c| {
            if *c == '!' {
                trigger = true;
            }

            c.is_numeric() && !trigger
        }));

        string
    }).collect();

    let mut result: usize = it[0].parse().unwrap_or_else(|_| {
        err.push_str("compile_error!(\"Error at parsing first operand.\")");
        0
    });

    if err != "" {
        return err.parse().unwrap();
    }

    for (i, e) in it.drain(1..).enumerate() {
        let e: usize = e.parse().unwrap_or_else(|_| {
            err.push_str("compile_error!(\"Error at parsing operand number ");
            err.push_str(i.to_string().as_ref());
            err.push_str(".\")");
            0
        });

        if err != "" {
            return err.parse().unwrap();
        }

        result += e;        
    }

    result.to_string().parse().unwrap()
}

/// Performs a compile-time substraction between comma-separated values,excluding that is prefixed with ! from they.
#[proc_macro]
pub fn sub(input: TokenStream) -> TokenStream {
    let input = input.to_string();
    let mut err = String::with_capacity(64);

    let mut it: Vec<String> = input.split(',').map(|e| {
        let mut trigger = false;
        let mut string = String::with_capacity(e.len()+1);

        string.push('0');

        string.extend(e.chars().filter(|c| {
            if *c == '!' {
                trigger = true;
            }

            c.is_numeric() && !trigger
        }));

        string
    }).collect();

    let mut result: isize = it[0].parse().unwrap_or_else(|_| {
        err.push_str("compile_error!(\"Error at parsing first operand.\")");
        0
    });

    if err != "" {
        return err.parse().unwrap();
    }

    for (i, e) in it.drain(1..).enumerate() {

        if e == "" {
            return ("compile_error!(\"Error at parsing operand number ".to_string() + 
            i.to_string().as_ref() + 
            ".\")").parse().unwrap()
        }

        let e: isize = e.parse().unwrap_or_else(|_| unsafe { unreachable_unchecked() });

        if err != "" {
            return err.parse().unwrap();
        }

        result -= e;        
    }

    result.to_string().parse().unwrap()
}

/// Performs a compile-time product between comma-separated values,excluding that is prefixed with ! from they.
#[proc_macro]
pub fn mul(input: TokenStream) -> TokenStream {
    let input = input.to_string();
    let mut err = String::with_capacity(64);

    let mut it: Vec<String> = input.split(',').map(|e| {
        let mut trigger = false;
        let mut string = String::with_capacity(e.len()+1);

        string.push('0');

        string.extend(e.chars().filter(|c| {
            if *c == '!' {
                trigger = true;
            }

            c.is_numeric() && !trigger
        }));

        string
    }).collect();

    let mut result: usize = it[0].parse().unwrap_or_else(|_| {
        err.push_str("compile_error!(\"Error at parsing first operand.\")");
        0
    });

    if err != "" {
        return err.parse().unwrap();
    }

    for (i, e) in it.drain(1..).enumerate() {
        if e == "" {
            return ("compile_error!(\"Error at parsing operand number ".to_string() + 
            i.to_string().as_ref() + 
            ".\")").parse().unwrap()
        }

        let e: usize = e.parse().unwrap_or_else(|_| unsafe { unreachable_unchecked() });

        if err != "" {
            return err.parse().unwrap();
        }

        result *= e;        
    }

    result.to_string().parse().unwrap()
}

/// Performs a compile-time division between comma-separated values,excluding that is prefixed with ! from they.
#[proc_macro]
pub fn div(input: TokenStream) -> TokenStream {
    let input = input.to_string();
    let mut err = String::with_capacity(64);

    let mut it: Vec<String> = input.split(',').map(|e| {
        let mut trigger = false;
        let mut string = String::with_capacity(e.len()+1);

        string.push('0');

        string.extend(e.chars().filter(|c| {
            if *c == '!' {
                trigger = true;
            }

            c.is_numeric() && !trigger
        }));

        string
    }).collect();

    let mut result: usize = it[0].parse().unwrap_or_else(|_| {
        err.push_str("compile_error!(\"Error at parsing first operand.\")");
        0
    });

    if err != "" {
        return err.parse().unwrap();
    }

    for (i, e) in it.drain(1..).enumerate() {
        if e == "" {
            return ("compile_error!(\"Error at parsing operand number ".to_string() + 
            i.to_string().as_ref() + 
            ".\")").parse().unwrap()
        }

        let e: usize = e.parse().unwrap_or_else(|_| unsafe { unreachable_unchecked() });

        result /= e;        
    }

    result.to_string().parse().unwrap()
}

/// Performs a compile-time remainder between comma-separated values,excluding that is prefixed with ! from they.
#[proc_macro]
pub fn rem(input: TokenStream) -> TokenStream {
    let input = input.to_string();
    let mut err = String::with_capacity(64);

    let mut it: Vec<String> = input.split(',').map(|e| {
        let mut trigger = false;
        let mut string = String::with_capacity(e.len()+1);

        string.push('0');

        string.extend(e.chars().filter(|c| {
            if *c == '!' {
                trigger = true;
            }

            c.is_numeric() && !trigger
        }));

        string
    }).collect();

    let mut result: usize = it[0].parse().unwrap_or_else(|_| {
        err.push_str("compile_error!(\"Error at parsing first operand.\")");
        0
    });

    if err != "" {
        return err.parse().unwrap();
    }

    for (i, e) in it.drain(1..).enumerate() {
        if e == "" {
            return ("compile_error!(\"Error at parsing operand number ".to_string() + 
            i.to_string().as_ref() + 
            ".\")").parse().unwrap()
        }

        let e: usize = e.parse().unwrap_or_else(|_| unsafe { unreachable_unchecked() });

        result %= e;        
    }

    result.to_string().parse().unwrap()
}

/// Performs a compile-time power between comma-separated values,excluding that is prefixed with ! from they.
#[proc_macro]
pub fn pow(input: TokenStream) -> TokenStream {
    let input = input.to_string();
    let mut err = String::with_capacity(64);

    let mut it: Vec<String> = input.split(',').map(|e| {
        let mut trigger = false;
        let mut string = String::with_capacity(e.len()+1);

        string.push('0');

        string.extend(e.chars().filter(|c| {
            if *c == '!' {
                trigger = true;
            }

            c.is_numeric() && !trigger
        }));

        string
    }).collect();

    let mut result: usize = it[0].parse().unwrap_or_else(|_| {
        err.push_str("compile_error!(\"Error at parsing first operand.\")");
        0
    });

    if err != "" {
        return err.parse().unwrap();
    }

    for (i, e) in it.drain(1..).enumerate() {
        if e == "" {
            return ("compile_error!(\"Error at parsing operand number ".to_string() + 
            i.to_string().as_ref() + 
            ".\")").parse().unwrap()
        }

        let e: u32 = e.parse().unwrap_or_else(|_| unsafe { unreachable_unchecked() });

        result = result.pow(e);        
    }

    result.to_string().parse().unwrap()
}

/// Performs any of the mathematical operations in Rust with their respective operator,`^` for power.
/// This macro also excludes anything that is prefixed with ! from the values.
/// 
/// The precedence is not applied,meaning that the operations are evaluated left to rigth.
#[proc_macro]
pub fn ops(input: TokenStream) -> TokenStream {
    let input = input.to_string();

    let mut operators = String::with_capacity(input.len());
    let mut err = String::with_capacity(64);

    let mut it: Vec<String> = input.split(|c: char| {
        match c {
            '+' => {operators.push('+'); true},
            '-' => {operators.push('-'); true},
            '*' => {operators.push('*'); true},
            '/' => {operators.push('/'); true},
            '%' => {operators.push('%'); true},
            '^' => {operators.push('^'); true},
            _ => false   
        }
    }).map(|e| {
        let mut trigger = false;
        let mut string = String::with_capacity(e.len()+1);

        string.push('0');

        string.extend(e.chars().filter(|c| {
            if *c == '!' {
                trigger = true;
            }

            c.is_numeric() && !trigger
        }));

        string
    }).collect();

    let mut result: isize = it[0].parse().unwrap_or_else(|_| {
        err.push_str("compile_error!(\"Error at parsing first operand.\")");
        0
    });

    if err != "" {
        return err.parse().unwrap();
    }

    for (i, (e, op)) in it.drain(1..).zip(operators.chars()).enumerate() {

        if e == "" {
            return format!("compile_error!(\"Error at parsing operand number {}.\")", i+1).parse().unwrap()
        }

        let e: isize = match e.parse() {
            Ok(i) => i,
            Err(_) => return format!("compile_error!(\"Error operand number {} overflows an isize.\")", i+1).parse().unwrap(),
        };

        match op {
            '+' => result = match result.checked_add(e) {
                Some(i) => i,
                None => return format!("compile_error!(\"operation number {} failed.\")", i+1).parse().unwrap(),
            },

            '-' => result = match result.checked_sub(e) {
                Some(i) => i,
                None => return format!("compile_error!(\"operation number {} failed.\")", i+1).parse().unwrap(),
            },

            '*' => result = match result.checked_mul(e) {
                Some(i) => i,
                None => return format!("compile_error!(\"operation number {} failed.\")", i+1).parse().unwrap(),
            },

            '/' => result = match result.checked_div(e) {
                Some(i) => i,
                None => return format!("compile_error!(\"operation number {} failed.\")", i+1).parse().unwrap(),
            },

            '%' => result = match result.checked_rem(e) {
                Some(i) => i,
                None => return format!("compile_error!(\"operation number {} failed.\")", i+1).parse().unwrap(),
            },

            '^' => result = match result.checked_pow(e as u32) {
                Some(i) => i,
                None => return format!("compile_error!(\"operation number {} failed.\")", i+1).parse().unwrap(),
            },

            _ => ()
        }        
    }

    result.to_string().parse().unwrap()
}

/// Ternary operations with `$bool:expr ? $code:expr $(! else_code)?` syntax for shorter and more legible conditionals.
/// 
/// This macro expand to `if bool_expr { code } else { else_code }` so does not prevent you for declaring
/// new scopes,take it count in position-sensitive code,because inner blocks can access outer ones this is not
/// typically a problem for safe code.
/// 
/// Because procedural macros does not expand if them are inside the arguments of another,you can't nest
/// ternary as you can do with normal `if` statements.
/// 
/// # Examples
/// 
/// ```
/// #![feature(proc_macro_hygiene)] // needed here due to the use in let
///                                 // statements but generally unneccesary
/// use compile_ops::ternary;
/// 
/// let mut one = 1;
/// let mut two = ternary!(one == 1 ? 2 ! 3);
/// 
/// assert_eq!(two, 2);
/// 
/// one = 2;
/// two = ternary!(one == 1 ? 2 ! 3);
/// 
/// ternary!(two == 3 ? one = 1);
/// 
/// assert_eq!(two, 3);
/// assert_eq!(one, 1);
/// ```
#[proc_macro]
pub fn ternary(input: TokenStream) -> TokenStream {
    let input = input.to_string();
    let mut expansion = String::with_capacity(input.len()+16);

    let mut index = input.find('?').unwrap_or_else(|| { expansion.push_str("compile_error!(\"Question mark character(?) not found in ternary operation.\")"); 0});

    if expansion != "" {
        return expansion.parse().unwrap();
    }

    if index == 0 {
        return "compile_error!(\"Missing boolean expresion behind the question mark character(?).\")".to_string().parse().unwrap();
    }

    let mut else_case = true;
    let (bool_expr, mut other) = input.split_at(index);
    
    other = &other[1..];

    index = other.rfind('!').unwrap_or_else(|| {else_case = false; 0});

    let (code, mut else_code) = if else_case { other.split_at(index) } else { (other, "") };

    if else_case {
        else_code = &else_code[1..];
    }

    expansion.push_str("if ");
    expansion.push_str(bool_expr);
    expansion.push_str(" {");
    expansion.push_str(code);
    expansion.push_str(" }");

    if else_case {
        expansion.push_str(" else { ");
        expansion.push_str(else_code);
        expansion.push_str(" }");
    }

    expansion.parse().unwrap()
}