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//! Plural operands in compliance with [CLDR Plural Rules](http://unicode.org/reports/tr35/tr35-numbers.html#Language_Plural_Rules).
//!
//! See [full operands description](http://unicode.org/reports/tr35/tr35-numbers.html#Operands).
//!
//! # Examples
//!
//! From int
//!
//! ```
//! use intl_pluralrules::operands::*;
//! assert_eq!(Ok(PluralOperands {
//!    n: 2_f64,
//!    i: 2,
//!    v: 0,
//!    w: 0,
//!    f: 0,
//!    t: 0,
//! }), PluralOperands::from(2))
//! ```
//!
//! From float
//!
//! ```
//! use intl_pluralrules::operands::*;
//! assert_eq!(Ok(PluralOperands {
//!    n: 1234.567_f64,
//!    i: 1234,
//!    v: 3,
//!    w: 3,
//!    f: 567,
//!    t: 567,
//! }), PluralOperands::from("-1234.567"))
//! ```
//!
//! From &str
//!
//! ```
//! use intl_pluralrules::operands::*;
//! assert_eq!(Ok(PluralOperands {
//!    n: 123.45_f64,
//!    i: 123,
//!    v: 2,
//!    w: 2,
//!    f: 45,
//!    t: 45,
//! }), PluralOperands::from(123.45))
//! ```
use std::isize;
use std::str::FromStr;

/// A full plural operands representation of a number. See [CLDR Plural Rules](http://unicode.org/reports/tr35/tr35-numbers.html#Language_Plural_Rules) for complete operands description.
#[derive(Debug, PartialEq)]
pub struct PluralOperands {
    /// Absolute value of input
    pub n: f64,
    /// Integer value of input
    pub i: isize,
    /// Number of visible fraction digits with trailing zeros
    pub v: isize,
    /// Number of visible fraction digits without trailing zeros
    pub w: isize,
    /// Visible fraction digits with trailing zeros
    pub f: isize,
    /// Visible fraction digits without trailing zeros
    pub t: isize,
}

impl PluralOperands {
    /// Given numerical input (as numeric type or reference), returns the PluralOperands representation of the input.
    ///
    /// # Example
    ///
    /// ```
    /// use intl_pluralrules::operands::*;
    /// assert_eq!(Ok(PluralOperands {
    ///    n: 123.45_f64,
    ///    i: 123,
    ///    v: 2,
    ///    w: 2,
    ///    f: 45,
    ///    t: 45,
    /// }), PluralOperands::from(123.45))
    /// ```
    pub fn from<S: ToString>(num: S) -> Result<Self, &'static str> {
        let str_num = num.to_string();

        let abs_str = if str_num.starts_with("-") {
            &str_num[1..]
        } else {
            &str_num
        };

        let absolute_value = f64::from_str(&abs_str).map_err(|_| "Incorrect number passed!")?;

        let integer_digits;
        let num_fraction_digits0;
        let num_fraction_digits;
        let fraction_digits0;
        let fraction_digits;

        if let Some(dec_pos) = abs_str.find('.') {
            let int_str = &abs_str[..dec_pos];
            let dec_str = &abs_str[(dec_pos + 1)..];

            integer_digits =
                isize::from_str(&int_str).map_err(|_| "Could not convert string to integer!")?;

            let backtrace = dec_str.trim_right_matches('0');

            num_fraction_digits0 = dec_str.chars().count() as isize;
            num_fraction_digits = backtrace.chars().count() as isize;
            fraction_digits0 =
                isize::from_str(dec_str).map_err(|_| "Could not convert string to integer!")?;
            fraction_digits = isize::from_str(backtrace).unwrap_or(0);
        } else {
            integer_digits = absolute_value as isize;
            num_fraction_digits0 = 0;
            num_fraction_digits = 0;
            fraction_digits0 = 0;
            fraction_digits = 0;
        }

        Ok(PluralOperands {
            n: absolute_value,
            i: integer_digits,
            v: num_fraction_digits0,
            w: num_fraction_digits,
            f: fraction_digits0,
            t: fraction_digits,
        })
    }
}