//! Zero-Knowledge Proof Module
//!
//! Provides zero-knowledge proof capabilities for sensitive KMS operations,
//! enabling privacy-preserving authentication and verification.

use std::collections::HashMap;

use async_trait::async_trait;

use crate::kms::error::KmsError;
use crate::kms::traits::ZkpProvider;
use crate::kms::types::{HealthStatus, ZkpConfig, ZkpSystem};

/// Zero-knowledge proof provider factory
pub struct ZkpProviderFactory;

impl ZkpProviderFactory {
    /// Create ZKP provider based on configuration
    pub async fn create(config: &ZkpConfig) -> Result<Box<dyn ZkpProvider>, KmsError> {
        if !config.enabled {
            return Err(KmsError::zkp("factory", "ZKP support is disabled"));
        }

        match config.proof_system {
            ZkpSystem::Groth16 => Ok(Box::new(Groth16Provider::new(config).await?)),
            ZkpSystem::Plonk => Ok(Box::new(PlonkProvider::new(config).await?)),
            ZkpSystem::Bulletproofs => Ok(Box::new(BulletproofsProvider::new(config).await?)),
        }
    }
}

/// Groth16 zero-knowledge proof provider
#[allow(dead_code)]
struct Groth16Provider {
    config: ZkpConfig,
}

impl Groth16Provider {
    async fn new(config: &ZkpConfig) -> Result<Self, KmsError> {
        Ok(Self {
            config: config.clone(),
        })
    }
}

#[async_trait]
impl ZkpProvider for Groth16Provider {
    async fn initialize(&mut self) -> Result<(), KmsError> {
        // TODO: Initialize Groth16 proving system
        // Load trusted setup parameters, verification keys, etc.
        Ok(())
    }

    async fn generate_access_proof(
        &self,
        _key_id: &str,
        _context: &HashMap<String, String>,
    ) -> Result<Vec<u8>, KmsError> {
        // TODO: Implement Groth16 access proof generation
        // This would generate a proof that the client has the right to access the key
        // without revealing the key or the client's identity
        Err(KmsError::zkp(
            "groth16",
            "Access proof generation not yet implemented",
        ))
    }

    async fn verify_access_proof(
        &self,
        _proof: &[u8],
        _key_id: &str,
        _context: &HashMap<String, String>,
    ) -> Result<bool, KmsError> {
        // TODO: Implement Groth16 access proof verification
        Err(KmsError::zkp(
            "groth16",
            "Access proof verification not yet implemented",
        ))
    }

    async fn generate_operation_proof(
        &self,
        _operation: &str,
        _key_id: &str,
        _data: &[u8],
    ) -> Result<Vec<u8>, KmsError> {
        // TODO: Implement Groth16 operation proof generation
        // This would generate a proof that an operation was performed correctly
        // without revealing the operation details
        Err(KmsError::zkp(
            "groth16",
            "Operation proof generation not yet implemented",
        ))
    }

    async fn verify_operation_proof(
        &self,
        _proof: &[u8],
        _operation: &str,
        _key_id: &str,
        _data: &[u8],
    ) -> Result<bool, KmsError> {
        // TODO: Implement Groth16 operation proof verification
        Err(KmsError::zkp(
            "groth16",
            "Operation proof verification not yet implemented",
        ))
    }

    async fn get_verification_key(&self) -> Result<Vec<u8>, KmsError> {
        // TODO: Return the verification key for this proving system
        Err(KmsError::zkp(
            "groth16",
            "Verification key retrieval not yet implemented",
        ))
    }

    async fn health_check(&self) -> Result<HealthStatus, KmsError> {
        Ok(HealthStatus::healthy("Groth16 ZKP provider operational"))
    }
}

/// PLONK zero-knowledge proof provider
#[allow(dead_code)]
struct PlonkProvider {
    config: ZkpConfig,
}

impl PlonkProvider {
    async fn new(config: &ZkpConfig) -> Result<Self, KmsError> {
        Ok(Self {
            config: config.clone(),
        })
    }
}

#[async_trait]
impl ZkpProvider for PlonkProvider {
    async fn initialize(&mut self) -> Result<(), KmsError> {
        // TODO: Initialize PLONK proving system
        Err(KmsError::zkp("plonk", "PLONK not yet implemented"))
    }

    async fn generate_access_proof(
        &self,
        _key_id: &str,
        _context: &HashMap<String, String>,
    ) -> Result<Vec<u8>, KmsError> {
        Err(KmsError::zkp("plonk", "PLONK not yet implemented"))
    }

    async fn verify_access_proof(
        &self,
        _proof: &[u8],
        _key_id: &str,
        _context: &HashMap<String, String>,
    ) -> Result<bool, KmsError> {
        Err(KmsError::zkp("plonk", "PLONK not yet implemented"))
    }

    async fn generate_operation_proof(
        &self,
        _operation: &str,
        _key_id: &str,
        _data: &[u8],
    ) -> Result<Vec<u8>, KmsError> {
        Err(KmsError::zkp("plonk", "PLONK not yet implemented"))
    }

    async fn verify_operation_proof(
        &self,
        _proof: &[u8],
        _operation: &str,
        _key_id: &str,
        _data: &[u8],
    ) -> Result<bool, KmsError> {
        Err(KmsError::zkp("plonk", "PLONK not yet implemented"))
    }

    async fn get_verification_key(&self) -> Result<Vec<u8>, KmsError> {
        Err(KmsError::zkp("plonk", "PLONK not yet implemented"))
    }

    async fn health_check(&self) -> Result<HealthStatus, KmsError> {
        Ok(HealthStatus::healthy("PLONK ZKP provider operational"))
    }
}

/// Bulletproofs zero-knowledge proof provider
#[allow(dead_code)]
struct BulletproofsProvider {
    config: ZkpConfig,
}

impl BulletproofsProvider {
    async fn new(config: &ZkpConfig) -> Result<Self, KmsError> {
        Ok(Self {
            config: config.clone(),
        })
    }
}

#[async_trait]
impl ZkpProvider for BulletproofsProvider {
    async fn initialize(&mut self) -> Result<(), KmsError> {
        // TODO: Initialize Bulletproofs proving system
        Err(KmsError::zkp(
            "bulletproofs",
            "Bulletproofs not yet implemented",
        ))
    }

    async fn generate_access_proof(
        &self,
        _key_id: &str,
        _context: &HashMap<String, String>,
    ) -> Result<Vec<u8>, KmsError> {
        Err(KmsError::zkp(
            "bulletproofs",
            "Bulletproofs not yet implemented",
        ))
    }

    async fn verify_access_proof(
        &self,
        _proof: &[u8],
        _key_id: &str,
        _context: &HashMap<String, String>,
    ) -> Result<bool, KmsError> {
        Err(KmsError::zkp(
            "bulletproofs",
            "Bulletproofs not yet implemented",
        ))
    }

    async fn generate_operation_proof(
        &self,
        _operation: &str,
        _key_id: &str,
        _data: &[u8],
    ) -> Result<Vec<u8>, KmsError> {
        Err(KmsError::zkp(
            "bulletproofs",
            "Bulletproofs not yet implemented",
        ))
    }

    async fn verify_operation_proof(
        &self,
        _proof: &[u8],
        _operation: &str,
        _key_id: &str,
        _data: &[u8],
    ) -> Result<bool, KmsError> {
        Err(KmsError::zkp(
            "bulletproofs",
            "Bulletproofs not yet implemented",
        ))
    }

    async fn get_verification_key(&self) -> Result<Vec<u8>, KmsError> {
        Err(KmsError::zkp(
            "bulletproofs",
            "Bulletproofs not yet implemented",
        ))
    }

    async fn health_check(&self) -> Result<HealthStatus, KmsError> {
        Ok(HealthStatus::healthy(
            "Bulletproofs ZKP provider operational",
        ))
    }
}

/// Zero-knowledge proof circuits and utilities
pub mod circuits {
    #[allow(unused_imports)]
    use super::*;

    /// Circuit for proving key access authorization
    pub struct KeyAccessCircuit {
        // Circuit implementation would go here
        // This would define the constraints for proving authorized key access
    }

    /// Circuit for proving operation correctness
    pub struct OperationCircuit {
        // Circuit implementation would go here
        // This would define the constraints for proving an operation was performed correctly
    }

    /// Circuit for proving key derivation
    pub struct KeyDerivationCircuit {
        // Circuit implementation would go here
        // This would define the constraints for proving key derivation without revealing inputs
    }
}

/// Zero-knowledge proof utilities
pub mod utils {
    use super::*;

    /// Generate trusted setup parameters for a circuit
    pub async fn generate_setup_params(_circuit: &str) -> Result<Vec<u8>, KmsError> {
        // TODO: Implement trusted setup generation
        Err(KmsError::zkp(
            "utils",
            "Setup generation not yet implemented",
        ))
    }

    /// Verify setup parameters integrity
    pub async fn verify_setup_params(_params: &[u8]) -> Result<bool, KmsError> {
        // TODO: Implement setup verification
        Err(KmsError::zkp(
            "utils",
            "Setup verification not yet implemented",
        ))
    }

    /// Convert proof to portable format
    pub fn serialize_proof(_proof: &[u8]) -> Result<String, KmsError> {
        // TODO: Implement proof serialization
        Err(KmsError::zkp(
            "utils",
            "Proof serialization not yet implemented",
        ))
    }

    /// Convert proof from portable format
    pub fn deserialize_proof(_proof_str: &str) -> Result<Vec<u8>, KmsError> {
        // TODO: Implement proof deserialization
        Err(KmsError::zkp(
            "utils",
            "Proof deserialization not yet implemented",
        ))
    }
}
