communitas-core 0.1.18

//! Forward Error Correction Storage (Stub Implementation)
//!
//! This module will implement resilient storage using Reed-Solomon erasure coding.
//! Currently a placeholder until we integrate with the existing reed_solomon_manager.

use anyhow::Result;
use std::path::{Path, PathBuf};
use tokio::fs;

/// FEC storage manager for resilient data storage
pub struct FecStorage {
    base_path: PathBuf,
    /// Default redundancy level for FEC encoding (reserved for future FEC operations)
    #[allow(dead_code)]
    default_redundancy: f32,
}

impl FecStorage {
    /// Create a new FEC storage manager
    pub async fn new(base_path: &Path, default_redundancy: f32) -> Result<Self> {
        let fec_path = base_path.join("fec");
        fs::create_dir_all(&fec_path).await?;

        Ok(Self {
            base_path: fec_path,
            default_redundancy,
        })
    }

    /// Store data with Forward Error Correction
    pub async fn store_with_fec(
        &self,
        key: &str,
        data: &[u8],
        _redundancy: f32,
    ) -> Result<Vec<PathBuf>> {
        // For now, just store the data directly without FEC
        // This will be replaced with actual Reed-Solomon encoding
        let key_dir = self.base_path.join(key);
        fs::create_dir_all(&key_dir).await?;

        let data_path = key_dir.join("data.enc");
        fs::write(&data_path, data).await?;

        // Store metadata
        let metadata = FecMetadata {
            original_size: data.len(),
            checksum: blake3::hash(data).as_bytes().to_vec(),
        };

        let metadata_path = key_dir.join("metadata.json");
        let metadata_json = serde_json::to_vec(&metadata)?;
        fs::write(metadata_path, metadata_json).await?;

        Ok(vec![data_path])
    }

    /// Retrieve data from FEC shards
    pub async fn retrieve_from_fec(&self, shard_paths: &[PathBuf]) -> Result<Vec<u8>> {
        if shard_paths.is_empty() {
            return Err(anyhow::anyhow!("No shard paths provided"));
        }

        // For now, just read the data directly
        // This will be replaced with actual Reed-Solomon decoding
        let data_path = &shard_paths[0];
        let data = fs::read(data_path).await?;

        // Verify checksum
        let key_dir = data_path
            .parent()
            .ok_or_else(|| anyhow::anyhow!("Invalid shard path"))?;
        let metadata_path = key_dir.join("metadata.json");
        let metadata_json = fs::read(metadata_path).await?;
        let metadata: FecMetadata = serde_json::from_slice(&metadata_json)?;

        let checksum = blake3::hash(&data);
        if checksum.as_bytes() != metadata.checksum.as_slice() {
            return Err(anyhow::anyhow!("Data integrity check failed"));
        }

        Ok(data)
    }

    /// Repair missing or corrupted shards (stub)
    pub async fn repair_shards(&self, _key: &str) -> Result<usize> {
        // Placeholder implementation
        Ok(0)
    }

    /// Delete FEC storage for a key
    pub async fn delete(&self, key: &str) -> Result<()> {
        let key_dir = self.base_path.join(key);
        if key_dir.exists() {
            fs::remove_dir_all(key_dir).await?;
        }
        Ok(())
    }

    /// Get storage statistics
    pub async fn get_stats(&self, key: &str) -> Result<FecStats> {
        let key_dir = self.base_path.join(key);

        let metadata_path = key_dir.join("metadata.json");
        let metadata_json = fs::read(metadata_path).await?;
        let metadata: FecMetadata = serde_json::from_slice(&metadata_json)?;

        let data_path = key_dir.join("data.enc");
        let data_size = if data_path.exists() {
            fs::metadata(&data_path).await?.len() as usize
        } else {
            0
        };

        Ok(FecStats {
            original_size: metadata.original_size,
            total_shards: 1, // Stub implementation has only one "shard"
            healthy_shards: 1,
            corrupted_shards: 0,
            redundancy: 1.0,
            storage_overhead: (data_size as f32) / (metadata.original_size as f32),
            can_recover: true,
        })
    }
}

#[derive(Debug, serde::Serialize, serde::Deserialize)]
struct FecMetadata {
    original_size: usize,
    checksum: Vec<u8>,
}

#[derive(Debug, Clone)]
pub struct FecStats {
    pub original_size: usize,
    pub total_shards: usize,
    pub healthy_shards: usize,
    pub corrupted_shards: usize,
    pub redundancy: f32,
    pub storage_overhead: f32,
    pub can_recover: bool,
}

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

    #[tokio::test]
    async fn test_fec_storage_basic() {
        let temp_dir = TempDir::new().unwrap();
        let fec = FecStorage::new(&temp_dir.path().to_path_buf(), 1.5)
            .await
            .unwrap();

        let test_data = vec![42u8; 1000];

        // Store with FEC
        let shard_paths = fec
            .store_with_fec("test_key", &test_data, 1.5)
            .await
            .unwrap();
        assert!(!shard_paths.is_empty());

        // Retrieve data
        let recovered = fec.retrieve_from_fec(&shard_paths).await.unwrap();
        assert_eq!(recovered, test_data);

        // Get statistics
        let stats = fec.get_stats("test_key").await.unwrap();
        assert!(stats.can_recover);
    }
}