itsgoin/crates/core/src/content.rs

use crate::types::{Post, PostId};

/// Compute the content ID (BLAKE3 hash) of a post.
/// This is deterministic: same post data always produces the same ID.
pub fn compute_post_id(post: &Post) -> PostId {
    let bytes = serde_json::to_vec(post).expect("post serialization should not fail");
    *blake3::hash(&bytes).as_bytes()
}

/// Verify that a post's content matches the claimed ID
pub fn verify_post_id(id: &PostId, post: &Post) -> bool {
    &compute_post_id(post) == id
}

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

    #[test]
    fn test_deterministic_hashing() {
        let post = Post {
            author: [1u8; 32],
            content: "hello world".to_string(),
            attachments: vec![],
            timestamp_ms: 1000,
        };
        let id1 = compute_post_id(&post);
        let id2 = compute_post_id(&post);
        assert_eq!(id1, id2);
    }

    #[test]
    fn test_different_content_different_id() {
        let post1 = Post {
            author: [1u8; 32],
            content: "hello".to_string(),
            attachments: vec![],
            timestamp_ms: 1000,
        };
        let post2 = Post {
            author: [1u8; 32],
            content: "world".to_string(),
            attachments: vec![],
            timestamp_ms: 1000,
        };
        assert_ne!(compute_post_id(&post1), compute_post_id(&post2));
    }

    #[test]
    fn test_verify() {
        let post = Post {
            author: [1u8; 32],
            content: "test".to_string(),
            attachments: vec![],
            timestamp_ms: 1000,
        };
        let id = compute_post_id(&post);
        assert!(verify_post_id(&id, &post));
        assert!(!verify_post_id(&[0u8; 32], &post));
    }
}