//! Operation types for did:plc (genesis, update, tombstone)

use crate::crypto::{SigningKey, VerifyingKey};
use crate::document::ServiceEndpoint;
use crate::encoding::{base64url_decode, compute_cid, dag_cbor_encode};
use crate::error::{PlcError, Result};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;

/// Represents a PLC operation (genesis, update, or tombstone)
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(tag = "type")]
pub enum Operation {
    /// Standard PLC operation (genesis or update)
    #[serde(rename = "plc_operation")]
    PlcOperation {
        /// Rotation keys (1-5 did:key strings)
        #[serde(rename = "rotationKeys")]
        rotation_keys: Vec<String>,

        /// Verification methods (max 10 entries)
        #[serde(rename = "verificationMethods")]
        verification_methods: HashMap<String, String>,

        /// Also-known-as URIs
        #[serde(rename = "alsoKnownAs")]
        also_known_as: Vec<String>,

        /// Service endpoints
        services: HashMap<String, ServiceEndpoint>,

        /// Previous operation CID (null for genesis)
        #[serde(skip_serializing_if = "Option::is_none")]
        prev: Option<String>,

        /// Base64url-encoded signature
        sig: String,
    },

    /// Tombstone operation (marks DID as deleted)
    #[serde(rename = "plc_tombstone")]
    PlcTombstone {
        /// Previous operation CID (never null for tombstone)
        prev: String,

        /// Base64url-encoded signature
        sig: String,
    },

    /// Legacy create operation (for backwards compatibility)
    #[serde(rename = "create")]
    LegacyCreate {
        /// Signing key (did:key format)
        #[serde(rename = "signingKey")]
        signing_key: String,

        /// Recovery key (did:key format)
        #[serde(rename = "recoveryKey")]
        recovery_key: String,

        /// Handle (e.g., "alice.bsky.social")
        handle: String,

        /// Service endpoint URL
        service: String,

        /// Previous operation CID
        #[serde(skip_serializing_if = "Option::is_none")]
        prev: Option<String>,

        /// Base64url-encoded signature
        sig: String,
    },
}

impl Operation {
    /// Create a new unsigned genesis operation
    pub fn new_genesis(
        rotation_keys: Vec<String>,
        verification_methods: HashMap<String, String>,
        also_known_as: Vec<String>,
        services: HashMap<String, ServiceEndpoint>,
    ) -> UnsignedOperation {
        UnsignedOperation::PlcOperation {
            rotation_keys,
            verification_methods,
            also_known_as,
            services,
            prev: None,
        }
    }

    /// Create a new unsigned update operation
    pub fn new_update(
        rotation_keys: Vec<String>,
        verification_methods: HashMap<String, String>,
        also_known_as: Vec<String>,
        services: HashMap<String, ServiceEndpoint>,
        prev: String,
    ) -> UnsignedOperation {
        UnsignedOperation::PlcOperation {
            rotation_keys,
            verification_methods,
            also_known_as,
            services,
            prev: Some(prev),
        }
    }

    /// Create a new unsigned tombstone operation
    pub fn new_tombstone(prev: String) -> UnsignedOperation {
        UnsignedOperation::PlcTombstone { prev }
    }

    /// Get the previous operation CID, if any
    pub fn prev(&self) -> Option<&str> {
        match self {
            Operation::PlcOperation { prev, .. } => prev.as_deref(),
            Operation::PlcTombstone { prev, .. } => Some(prev),
            Operation::LegacyCreate { prev, .. } => prev.as_deref(),
        }
    }

    /// Get the signature as a base64url string
    pub fn signature(&self) -> &str {
        match self {
            Operation::PlcOperation { sig, .. } => sig,
            Operation::PlcTombstone { sig, .. } => sig,
            Operation::LegacyCreate { sig, .. } => sig,
        }
    }

    /// Check if this is a genesis operation (prev is None)
    pub fn is_genesis(&self) -> bool {
        self.prev().is_none()
    }

    /// Compute the CID of this operation
    ///
    /// # Errors
    ///
    /// Returns an error if DAG-CBOR encoding fails
    pub fn cid(&self) -> Result<String> {
        let encoded = dag_cbor_encode(self)?;
        compute_cid(&encoded)
    }

    /// Verify the signature on this operation using the provided rotation keys
    ///
    /// # Errors
    ///
    /// Returns `PlcError::SignatureVerificationFailed` if verification fails
    pub fn verify(&self, rotation_keys: &[VerifyingKey]) -> Result<()> {
        if rotation_keys.is_empty() {
            return Err(PlcError::InvalidRotationKeys(
                "At least one rotation key is required for verification".to_string(),
            ));
        }

        // Get the unsigned operation data
        let unsigned_data = self.unsigned_data()?;

        // Decode signature
        let signature = base64url_decode(self.signature())?;

        // Try to verify with each rotation key
        let mut last_error = None;
        for key in rotation_keys {
            match key.verify(&unsigned_data, &signature) {
                Ok(_) => return Ok(()), // Success!
                Err(e) => last_error = Some(e),
            }
        }

        // If we get here, none of the keys verified the signature
        Err(last_error.unwrap_or(PlcError::SignatureVerificationFailed))
    }

    /// Get the unsigned data that was signed
    fn unsigned_data(&self) -> Result<Vec<u8>> {
        let unsigned = match self {
            Operation::PlcOperation {
                rotation_keys,
                verification_methods,
                also_known_as,
                services,
                prev,
                ..
            } => UnsignedOperation::PlcOperation {
                rotation_keys: rotation_keys.clone(),
                verification_methods: verification_methods.clone(),
                also_known_as: also_known_as.clone(),
                services: services.clone(),
                prev: prev.clone(),
            },
            Operation::PlcTombstone { prev, .. } => UnsignedOperation::PlcTombstone {
                prev: prev.clone(),
            },
            Operation::LegacyCreate {
                signing_key,
                recovery_key,
                handle,
                service,
                prev,
                ..
            } => UnsignedOperation::LegacyCreate {
                signing_key: signing_key.clone(),
                recovery_key: recovery_key.clone(),
                handle: handle.clone(),
                service: service.clone(),
                prev: prev.clone(),
            },
        };

        dag_cbor_encode(&unsigned)
    }

    /// Get the rotation keys from this operation, if any
    pub fn rotation_keys(&self) -> Option<&[String]> {
        match self {
            Operation::PlcOperation { rotation_keys, .. } => Some(rotation_keys),
            _ => None,
        }
    }
}

/// An unsigned operation that needs to be signed
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(tag = "type")]
pub enum UnsignedOperation {
    /// Standard PLC operation (genesis or update)
    #[serde(rename = "plc_operation")]
    PlcOperation {
        /// Rotation keys for signing future operations
        #[serde(rename = "rotationKeys")]
        rotation_keys: Vec<String>,

        /// Verification methods for authentication
        #[serde(rename = "verificationMethods")]
        verification_methods: HashMap<String, String>,

        /// Also-known-as URIs (aliases)
        #[serde(rename = "alsoKnownAs")]
        also_known_as: Vec<String>,

        /// Service endpoints
        services: HashMap<String, ServiceEndpoint>,

        /// CID of previous operation (None for genesis)
        #[serde(skip_serializing_if = "Option::is_none")]
        prev: Option<String>,
    },

    /// Tombstone operation
    #[serde(rename = "plc_tombstone")]
    PlcTombstone {
        /// CID of previous operation
        prev: String,
    },

    /// Legacy create operation
    #[serde(rename = "create")]
    LegacyCreate {
        /// Signing key for the DID
        #[serde(rename = "signingKey")]
        signing_key: String,

        /// Recovery key for the DID
        #[serde(rename = "recoveryKey")]
        recovery_key: String,

        /// Handle for the DID
        handle: String,

        /// Service endpoint
        service: String,

        /// CID of previous operation (None for genesis)
        #[serde(skip_serializing_if = "Option::is_none")]
        prev: Option<String>,
    },
}

impl UnsignedOperation {
    /// Sign this operation with the provided signing key
    ///
    /// # Errors
    ///
    /// Returns an error if signing or encoding fails
    pub fn sign(self, key: &SigningKey) -> Result<Operation> {
        // Serialize to DAG-CBOR
        let data = dag_cbor_encode(&self)?;

        // Sign the data
        let signature = key.sign_base64url(&data)?;

        // Create the signed operation
        let operation = match self {
            UnsignedOperation::PlcOperation {
                rotation_keys,
                verification_methods,
                also_known_as,
                services,
                prev,
            } => Operation::PlcOperation {
                rotation_keys,
                verification_methods,
                also_known_as,
                services,
                prev,
                sig: signature,
            },
            UnsignedOperation::PlcTombstone { prev } => Operation::PlcTombstone {
                prev,
                sig: signature,
            },
            UnsignedOperation::LegacyCreate {
                signing_key,
                recovery_key,
                handle,
                service,
                prev,
            } => Operation::LegacyCreate {
                signing_key,
                recovery_key,
                handle,
                service,
                prev,
                sig: signature,
            },
        };

        Ok(operation)
    }

    /// Compute the CID of this unsigned operation
    ///
    /// This is used to derive the DID from the genesis operation
    pub fn cid(&self) -> Result<String> {
        let encoded = dag_cbor_encode(self)?;
        compute_cid(&encoded)
    }
}

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

    #[test]
    fn test_genesis_operation() {
        let key = SigningKey::generate_p256();
        let did_key = key.to_did_key();

        let unsigned = Operation::new_genesis(
            vec![did_key.clone()],
            HashMap::new(),
            vec![],
            HashMap::new(),
        );

        let signed = unsigned.sign(&key).unwrap();
        assert!(signed.is_genesis());
        assert_eq!(signed.prev(), None);
    }

    #[test]
    fn test_update_operation() {
        let key = SigningKey::generate_p256();
        let did_key = key.to_did_key();

        let unsigned = Operation::new_update(
            vec![did_key],
            HashMap::new(),
            vec![],
            HashMap::new(),
            "bafyreib2rxk3rybk3aobmv5msrxগত7h4b4kfzxx4wxltyqu7e7vgq".to_string(),
        );

        let signed = unsigned.sign(&key).unwrap();
        assert!(!signed.is_genesis());
        assert!(signed.prev().is_some());
    }

    #[test]
    fn test_tombstone_operation() {
        let key = SigningKey::generate_p256();

        let unsigned = Operation::new_tombstone(
            "bafyreib2rxk3rybk3aobmv5msrxhgt7h4b4kfzxx4wxltyqu7e7vgq".to_string(),
        );

        let signed = unsigned.sign(&key).unwrap();
        assert!(!signed.is_genesis());
        assert!(signed.prev().is_some());
    }

    #[test]
    fn test_sign_and_verify() {
        let key = SigningKey::generate_p256();
        let did_key = key.to_did_key();

        let unsigned = Operation::new_genesis(
            vec![did_key.clone()],
            HashMap::new(),
            vec![],
            HashMap::new(),
        );

        let signed = unsigned.sign(&key).unwrap();

        // Parse the rotation key to get verifying key
        let verifying_key = VerifyingKey::from_did_key(&did_key).unwrap();

        // Verify should succeed
        assert!(signed.verify(&[verifying_key]).is_ok());

        // Verify with wrong key should fail
        let wrong_key = SigningKey::generate_p256();
        let wrong_verifying_key = wrong_key.verifying_key();
        assert!(signed.verify(&[wrong_verifying_key]).is_err());
    }

    #[test]
    fn test_operation_cid() {
        let key = SigningKey::generate_p256();
        let did_key = key.to_did_key();

        let unsigned = Operation::new_genesis(
            vec![did_key],
            HashMap::new(),
            vec![],
            HashMap::new(),
        );

        let signed = unsigned.sign(&key).unwrap();
        let cid = signed.cid().unwrap();

        // CID should start with 'b' (CIDv1 in base32)
        assert!(cid.starts_with('b'));
    }
}