//! Backup Manifest - Snapshot metadata serialization
//!
//! Compatible with ZFS send/receive and Proxmox Backup Server format

use std::path::PathBuf;

use serde::{Serialize, Deserialize};
use sha2::Digest;

use super::{VfsCompression};
use super::checksum::VfsChecksumFile;
use super::dedup::DedupManifest;

pub const MANIFEST_VERSION: u32 = 1;
pub const MANIFEST_FILE: &str = ".manifest.json";

#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub enum SendFormat {
    #[serde(rename = "zfs_compatible")]
    ZfsCompatible,
    #[serde(rename = "custom_json")]
    CustomJson,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BackupFileEntry {
    pub path: String,
    pub size: u64,
    pub checksums: Option<VfsChecksumFile>,
    pub dedup_hash: Option<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct EncryptionInfo {
    pub algorithm: String,
    pub enabled: bool,
    pub key_hash: Option<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CompressionInfo {
    pub algorithm: String,
    pub level: u32,
    pub original_size: u64,
    pub compressed_size: u64,
    pub ratio: f64,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BackupManifest {
    pub version: u32,
    pub format: SendFormat,
    pub snapshot_name: String,
    pub created_at: u64,
    pub root_path: String,
    pub files: Vec<BackupFileEntry>,
    pub dedup_manifest: Option<DedupManifest>,
    pub encryption: Option<EncryptionInfo>,
    pub compression: Option<CompressionInfo>,
    pub total_size: u64,
    pub stored_size: u64,
    pub overall_ratio: f64,
}

impl BackupManifest {
    pub fn new(snapshot_name: String, root_path: PathBuf) -> Self {
        Self {
            version: MANIFEST_VERSION,
            format: SendFormat::CustomJson,
            snapshot_name,
            created_at: current_time_secs(),
            root_path: root_path.to_string_lossy().to_string(),
            files: Vec::new(),
            dedup_manifest: None,
            encryption: None,
            compression: None,
            total_size: 0,
            stored_size: 0,
            overall_ratio: 1.0,
        }
    }

    pub fn add_file(&mut self, path: String, size: u64, checksums: Option<VfsChecksumFile>) {
        self.files.push(BackupFileEntry {
            path,
            size,
            checksums,
            dedup_hash: None,
        });
        self.total_size += size;
    }

    pub fn set_dedup(&mut self, manifest: DedupManifest) {
        self.dedup_manifest = Some(manifest.clone());
        if manifest.original_size > 0 {
            let stored = (manifest.block_hashes.len() as u64) * 4096; // Approximate
            self.stored_size = stored;
        }
    }

    pub fn set_compression(&mut self, algorithm: VfsCompression, original: u64, compressed: u64) {
        let ratio = if original > 0 { compressed as f64 / original as f64 } else { 1.0 };
        self.compression = Some(CompressionInfo {
            algorithm: algorithm_name(&algorithm),
            level: 3,
            original_size: original,
            compressed_size: compressed,
            ratio,
        });
    }

    pub fn set_encryption(&mut self, enabled: bool, key_hash: Option<String>) {
        self.encryption = Some(EncryptionInfo {
            algorithm: "AES-256-GCM".to_string(),
            enabled,
            key_hash,
        });
    }

    pub fn calculate_ratio(&mut self) {
        if self.total_size > 0 && self.stored_size > 0 {
            self.overall_ratio = self.stored_size as f64 / self.total_size as f64;
        }
    }

    pub fn to_bytes(&self) -> Result<Vec<u8>, String> {
        serde_json::to_vec(self).map_err(|e| e.to_string())
    }

    pub fn from_bytes(data: &[u8]) -> Result<Self, String> {
        serde_json::from_slice(data).map_err(|e| e.to_string())
    }

    pub fn save(&self, snapshot_dir: &PathBuf) -> Result<(), String> {
        let manifest_path = snapshot_dir.join(MANIFEST_FILE);
        let data = self.to_bytes()?;
        std::fs::write(&manifest_path, data).map_err(|e| e.to_string())
    }

    pub fn load(snapshot_dir: &PathBuf) -> Result<Self, String> {
        let manifest_path = snapshot_dir.join(MANIFEST_FILE);
        let data = std::fs::read(&manifest_path).map_err(|e| e.to_string())?;
        Self::from_bytes(&data)
    }
}

fn algorithm_name(compression: &VfsCompression) -> String {
    match compression {
        VfsCompression::None => "none".to_string(),
        VfsCompression::Lz4 => "lz4".to_string(),
        VfsCompression::Zstd => "zstd".to_string(),
    }
}

fn current_time_secs() -> u64 {
    use std::time::{SystemTime, UNIX_EPOCH};
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs())
        .unwrap_or(0)
}

#[derive(Debug, Clone)]
pub struct BackupStream {
    pub format: SendFormat,
    pub manifest: BackupManifest,
    pub data: Vec<u8>,
}

impl BackupStream {
    pub fn new(format: SendFormat, manifest: BackupManifest, data: Vec<u8>) -> Self {
        Self { format, manifest, data }
    }

    pub fn to_bytes(&self) -> Result<Vec<u8>, String> {
        match self.format {
            SendFormat::CustomJson => {
                let manifest_bytes = self.manifest.to_bytes()?;
                let mut result = Vec::new();
                result.extend_from_slice(&manifest_bytes.len().to_be_bytes());
                result.extend_from_slice(&manifest_bytes);
                result.extend_from_slice(&self.data);
                Ok(result)
            }
            SendFormat::ZfsCompatible => {
                Err("ZFS compatible format not yet implemented".to_string())
            }
        }
    }

    pub fn from_bytes(data: &[u8]) -> Result<Self, String> {
        if data.len() < 8 {
            return Err("Stream too short".to_string());
        }

        let manifest_len = u64::from_be_bytes(data[0..8].try_into().map_err(|_| "Invalid length")?) as usize;
        if data.len() < 8 + manifest_len {
            return Err("Stream truncated".to_string());
        }

        let manifest_bytes = &data[8..8 + manifest_len];
        let manifest = BackupManifest::from_bytes(manifest_bytes)?;
        let payload = data[8 + manifest_len..].to_vec();

        Ok(Self::new(manifest.format.clone(), manifest, payload))
    }
}

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

    #[test]
    fn test_manifest_creation() {
        let manifest = BackupManifest::new("snap_2026-06-24".to_string(), PathBuf::from("/data"));
        assert_eq!(manifest.version, MANIFEST_VERSION);
        assert_eq!(manifest.format, SendFormat::CustomJson);
        assert_eq!(manifest.snapshot_name, "snap_2026-06-24");
    }

    #[test]
    fn test_manifest_serialization() {
        let mut manifest = BackupManifest::new("test_snap".to_string(), PathBuf::from("/data"));
        manifest.add_file("file1.txt".to_string(), 1024, None);
        manifest.add_file("file2.txt".to_string(), 2048, None);
        manifest.calculate_ratio();

        let bytes = manifest.to_bytes().unwrap();
        let decoded = BackupManifest::from_bytes(&bytes).unwrap();

        assert_eq!(decoded.files.len(), 2);
        assert_eq!(decoded.total_size, 3072);
    }

    #[test]
    fn test_backup_stream_roundtrip() {
        let manifest = BackupManifest::new("test".to_string(), PathBuf::from("/"));
        let stream = BackupStream::new(SendFormat::CustomJson, manifest, b"test data".to_vec());

        let bytes = stream.to_bytes().unwrap();
        let decoded = BackupStream::from_bytes(&bytes).unwrap();

        assert_eq!(decoded.data, b"test data");
    }

    #[test]
    fn test_compression_info() {
        let mut manifest = BackupManifest::new("test".to_string(), PathBuf::from("/"));
        manifest.set_compression(VfsCompression::Zstd, 1000, 420);

        assert!(manifest.compression.is_some());
        let comp = manifest.compression.unwrap();
        assert_eq!(comp.algorithm, "zstd");
        assert_eq!(comp.ratio, 0.42);
    }

    #[test]
    fn test_encryption_info() {
        let mut manifest = BackupManifest::new("test".to_string(), PathBuf::from("/"));
        manifest.set_encryption(true, Some("key_hash_abc".to_string()));

        assert!(manifest.encryption.is_some());
        let enc = manifest.encryption.unwrap();
        assert!(enc.enabled);
        assert_eq!(enc.algorithm, "AES-256-GCM");
    }
}