use std::hash::{DefaultHasher, Hash, Hasher};

use crate::component::{
    IsOptional as ComponentIsOptional,
    Metadata as ComponentMetadata,
};

/// Archetype ID.
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
pub struct Id
{
    hash: u64,
}

impl Id
{
    pub fn from_components_metadata(
        components_metadata: &impl AsRef<[ComponentMetadata]>,
    ) -> Self
    {
        if components_metadata.as_ref().len() == 0 {
            return Self { hash: 0 };
        }

        debug_assert!(
            components_metadata
                .as_ref()
                .is_sorted_by_key(|comp_metadata| comp_metadata.id),
            "Cannot create archetype ID from a unsorted component metadata list"
        );

        let component_ids =
            components_metadata
                .as_ref()
                .iter()
                .filter_map(|component_metadata| {
                    if component_metadata.is_optional == ComponentIsOptional::Yes {
                        return None;
                    }

                    Some(component_metadata.id)
                });

        let mut hasher = DefaultHasher::new();

        for component_id in component_ids {
            component_id.hash(&mut hasher);
        }

        let hash = hasher.finish();

        assert_ne!(
            hash, 0,
            "Archetype ID 0 is reserved for a archetype with zero components"
        );

        Self { hash }
    }
}