//! This crate provides a `const` FNV32 hasher for the purpose of supporting the ESPHome/Home Assistant protocol where required.
//!
//! ```
//! use sachy_fnv::fnv32_hash;
//!
//! let hash = fnv32_hash("water_pump_1");
//!
//! assert_eq!(hash, 3557162331);
//! ```
#![no_std]

const FNV_OFFSET_BASIS_32: u32 = 0x811c9dc5;
const FNV_PRIME_32: u32 = 0x01000193;

/// `const` FNV32 hasher. Takes a `&str` and returns a `u32` hash.
pub const fn fnv32_hash(str: &str) -> u32 {
    let bytes = str.as_bytes();

    let mut hash = FNV_OFFSET_BASIS_32;
    let mut i = 0;
    let len = bytes.len();

    while i < len {
        hash = hash.wrapping_mul(FNV_PRIME_32);
        hash ^= bytes[i] as u32;
        i += 1;
    }

    hash
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn it_works() {
        let result = fnv32_hash("water_pump_1");
        assert_eq!(result, 3557162331);
        let result = fnv32_hash("pump_1_duration");
        assert_eq!(result, 931766070);
    }
}