use ed25519_dalek::{Signer, Verifier};

use crate::types::{DirectoryEntry, DirectoryEntryPayload, NodeId, Signature};

// ─── Keypair ────────────────────────────────────────────────────────────────

/// Node identity keypair — wraps ed25519-dalek.
pub struct Keypair {
    inner: ed25519_dalek::SigningKey,
}

impl Keypair {
    /// Generate a new random keypair.
    pub fn generate() -> Self {
        let mut csprng = rand_core::OsRng;
        Self {
            inner: ed25519_dalek::SigningKey::generate(&mut csprng),
        }
    }

    /// Reconstruct from raw secret key bytes (32 bytes).
    pub fn from_bytes(secret: &[u8; 32]) -> Self {
        Self {
            inner: ed25519_dalek::SigningKey::from_bytes(secret),
        }
    }

    /// The public key as a `NodeId`.
    pub fn node_id(&self) -> NodeId {
        NodeId(self.inner.verifying_key().to_bytes())
    }

    /// Raw secret key bytes.
    pub fn secret_bytes(&self) -> [u8; 32] {
        self.inner.to_bytes()
    }

    /// Sign arbitrary bytes.
    pub fn sign(&self, msg: &[u8]) -> Signature {
        let sig = self.inner.sign(msg);
        Signature(sig.to_bytes())
    }

    /// Sign a directory entry payload, returning a complete `DirectoryEntry`.
    pub fn sign_directory_entry(
        &self,
        actor_addr: swactor::actor::ActorAddress,
        generation: u64,
    ) -> DirectoryEntry {
        let payload = DirectoryEntryPayload {
            actor_addr,
            node_id: self.node_id(),
            generation,
        };
        let bytes = serde_json::to_vec(&payload).expect("DirectoryEntryPayload is always serializable");
        let signature = self.sign(&bytes);
        DirectoryEntry {
            actor_addr,
            node_id: self.node_id(),
            generation,
            signature,
        }
    }
}

// ─── Verification ───────────────────────────────────────────────────────────

/// Verify a signature against a `NodeId` (public key) and message bytes.
pub fn verify(node_id: &NodeId, msg: &[u8], sig: &Signature) -> bool {
    let Ok(vk) = ed25519_dalek::VerifyingKey::from_bytes(&node_id.0) else {
        return false;
    };
    let signature = ed25519_dalek::Signature::from_bytes(&sig.0);
    vk.verify(msg, &signature).is_ok()
}

/// Verify a `DirectoryEntry`'s signature against its embedded `node_id`.
pub fn verify_directory_entry(entry: &DirectoryEntry) -> bool {
    let payload = entry.payload();
    let Ok(bytes) = serde_json::to_vec(&payload) else {
        return false;
    };
    verify(&entry.node_id, &bytes, &entry.signature)
}