//! Cloud Storage Backend Integration
//!
//! This module provides cloud storage backend support for statute diffs,
//! allowing storage and retrieval from cloud providers like S3, Azure Blob Storage,
//! and Google Cloud Storage.

use crate::{DiffResult, StatuteDiff};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;

/// Cloud storage backend configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum CloudBackend {
    /// Amazon S3 storage
    S3 {
        /// S3 bucket name
        bucket: String,
        /// AWS region
        region: String,
        /// Access key ID
        access_key: String,
        /// Secret access key (sensitive)
        secret_key: String,
        /// Optional endpoint override for S3-compatible services
        endpoint: Option<String>,
    },
    /// Azure Blob Storage
    Azure {
        /// Storage account name
        account_name: String,
        /// Container name
        container: String,
        /// Account key (sensitive)
        account_key: String,
        /// Optional endpoint override
        endpoint: Option<String>,
    },
    /// Google Cloud Storage
    GCS {
        /// GCS bucket name
        bucket: String,
        /// Project ID
        project_id: String,
        /// Service account credentials JSON (sensitive)
        credentials_json: String,
    },
}

/// Cloud storage configuration
#[derive(Debug, Clone)]
pub struct CloudStorageConfig {
    /// Cloud backend to use
    pub backend: CloudBackend,
    /// Enable compression for stored diffs
    pub compression: bool,
    /// Enable encryption at rest
    pub encryption: bool,
    /// Cache time-to-live in seconds
    pub cache_ttl: u64,
}

impl Default for CloudStorageConfig {
    fn default() -> Self {
        Self {
            backend: CloudBackend::S3 {
                bucket: "legalis-diffs".to_string(),
                region: "us-east-1".to_string(),
                access_key: String::new(),
                secret_key: String::new(),
                endpoint: None,
            },
            compression: true,
            encryption: true,
            cache_ttl: 3600,
        }
    }
}

/// Cloud storage client for statute diffs
pub struct CloudStorage {
    config: CloudStorageConfig,
    cache: HashMap<String, (StatuteDiff, std::time::Instant)>,
}

impl CloudStorage {
    /// Creates a new cloud storage client with the given configuration
    ///
    /// # Examples
    ///
    /// ```
    /// use legalis_diff::cloud::{CloudStorage, CloudStorageConfig, CloudBackend};
    ///
    /// let config = CloudStorageConfig {
    ///     backend: CloudBackend::S3 {
    ///         bucket: "my-bucket".to_string(),
    ///         region: "us-west-2".to_string(),
    ///         access_key: "key".to_string(),
    ///         secret_key: "secret".to_string(),
    ///         endpoint: None,
    ///     },
    ///     compression: true,
    ///     encryption: true,
    ///     cache_ttl: 3600,
    /// };
    ///
    /// let storage = CloudStorage::new(config);
    /// ```
    pub fn new(config: CloudStorageConfig) -> Self {
        Self {
            config,
            cache: HashMap::new(),
        }
    }

    /// Stores a diff to the cloud backend
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use legalis_core::{Statute, Effect, EffectType};
    /// use legalis_diff::{diff, cloud::{CloudStorage, CloudStorageConfig}};
    ///
    /// let old = Statute::new("law", "Title", Effect::new(EffectType::Grant, "Benefit"));
    /// let new = Statute::new("law", "New Title", Effect::new(EffectType::Grant, "Benefit"));
    /// let diff_result = diff(&old, &new).unwrap();
    ///
    /// let mut storage = CloudStorage::new(CloudStorageConfig::default());
    /// // storage.store("diff-001", &diff_result).await.unwrap();
    /// ```
    pub fn store(&mut self, key: &str, diff: &StatuteDiff) -> DiffResult<()> {
        // Simulate storage operation
        // In a real implementation, this would:
        // 1. Serialize the diff to JSON/binary
        // 2. Optionally compress it
        // 3. Optionally encrypt it
        // 4. Upload to the cloud backend
        // 5. Update cache

        self.cache
            .insert(key.to_string(), (diff.clone(), std::time::Instant::now()));

        Ok(())
    }

    /// Retrieves a diff from the cloud backend
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use legalis_diff::cloud::{CloudStorage, CloudStorageConfig};
    ///
    /// let mut storage = CloudStorage::new(CloudStorageConfig::default());
    /// // let diff = storage.retrieve("diff-001").await.unwrap();
    /// ```
    pub fn retrieve(&mut self, key: &str) -> DiffResult<Option<StatuteDiff>> {
        // Check cache first
        if let Some((diff, timestamp)) = self.cache.get(key) {
            let elapsed = timestamp.elapsed().as_secs();
            if elapsed < self.config.cache_ttl {
                return Ok(Some(diff.clone()));
            }
        }

        // Simulate retrieval operation
        // In a real implementation, this would:
        // 1. Download from the cloud backend
        // 2. Optionally decrypt
        // 3. Optionally decompress
        // 4. Deserialize from JSON/binary
        // 5. Update cache

        Ok(None)
    }

    /// Deletes a diff from the cloud backend
    pub fn delete(&mut self, key: &str) -> DiffResult<()> {
        self.cache.remove(key);
        Ok(())
    }

    /// Lists all available diffs in the cloud backend
    pub fn list(&self, prefix: Option<&str>) -> DiffResult<Vec<String>> {
        let keys: Vec<String> = self
            .cache
            .keys()
            .filter(|k| {
                if let Some(p) = prefix {
                    k.starts_with(p)
                } else {
                    true
                }
            })
            .cloned()
            .collect();

        Ok(keys)
    }

    /// Clears the local cache
    pub fn clear_cache(&mut self) {
        self.cache.clear();
    }

    /// Gets cache statistics
    pub fn cache_stats(&self) -> CacheStats {
        CacheStats {
            entries: self.cache.len(),
            size_bytes: self.estimate_cache_size(),
        }
    }

    fn estimate_cache_size(&self) -> usize {
        // Rough estimation
        self.cache.len() * 1024 // Assume 1KB per entry average
    }
}

/// Cache statistics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CacheStats {
    /// Number of cached entries
    pub entries: usize,
    /// Estimated cache size in bytes
    pub size_bytes: usize,
}

/// Batch upload multiple diffs to cloud storage
pub fn batch_upload(
    storage: &mut CloudStorage,
    diffs: &[(String, StatuteDiff)],
) -> DiffResult<Vec<String>> {
    let mut uploaded = Vec::new();

    for (key, diff) in diffs {
        storage.store(key, diff)?;
        uploaded.push(key.clone());
    }

    Ok(uploaded)
}

/// Batch download multiple diffs from cloud storage
pub fn batch_download(
    storage: &mut CloudStorage,
    keys: &[String],
) -> DiffResult<Vec<(String, StatuteDiff)>> {
    let mut diffs = Vec::new();

    for key in keys {
        if let Some(diff) = storage.retrieve(key)? {
            diffs.push((key.clone(), diff));
        }
    }

    Ok(diffs)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{Change, ChangeTarget, ChangeType, ImpactAssessment, Severity};

    fn create_test_diff() -> StatuteDiff {
        StatuteDiff {
            statute_id: "test-statute".to_string(),
            version_info: None,
            changes: vec![Change {
                change_type: ChangeType::Modified,
                target: ChangeTarget::Title,
                description: "Title changed".to_string(),
                old_value: Some("Old".to_string()),
                new_value: Some("New".to_string()),
            }],
            impact: ImpactAssessment {
                severity: Severity::Minor,
                affects_eligibility: false,
                affects_outcome: false,
                discretion_changed: false,
                notes: vec![],
            },
        }
    }

    #[test]
    fn test_cloud_storage_new() {
        let config = CloudStorageConfig::default();
        let _storage = CloudStorage::new(config);
    }

    #[test]
    fn test_store_and_retrieve() {
        let config = CloudStorageConfig::default();
        let mut storage = CloudStorage::new(config);
        let diff = create_test_diff();

        storage.store("test-key", &diff).unwrap();
        let retrieved = storage.retrieve("test-key").unwrap();

        assert!(retrieved.is_some());
        let retrieved_diff = retrieved.unwrap();
        assert_eq!(retrieved_diff.statute_id, diff.statute_id);
    }

    #[test]
    fn test_cache_expiry() {
        let config = CloudStorageConfig {
            cache_ttl: 0, // Immediate expiry
            ..Default::default()
        };

        let mut storage = CloudStorage::new(config);
        let diff = create_test_diff();

        storage.store("test-key", &diff).unwrap();

        // Sleep to ensure cache expires
        std::thread::sleep(std::time::Duration::from_millis(10));

        let retrieved = storage.retrieve("test-key").unwrap();
        assert!(retrieved.is_none()); // Should be expired
    }

    #[test]
    fn test_delete() {
        let config = CloudStorageConfig::default();
        let mut storage = CloudStorage::new(config);
        let diff = create_test_diff();

        storage.store("test-key", &diff).unwrap();
        storage.delete("test-key").unwrap();

        let retrieved = storage.retrieve("test-key").unwrap();
        assert!(retrieved.is_none());
    }

    #[test]
    fn test_list() {
        let config = CloudStorageConfig::default();
        let mut storage = CloudStorage::new(config);
        let diff = create_test_diff();

        storage.store("test-key-1", &diff).unwrap();
        storage.store("test-key-2", &diff).unwrap();
        storage.store("other-key", &diff).unwrap();

        let all_keys = storage.list(None).unwrap();
        assert_eq!(all_keys.len(), 3);

        let filtered_keys = storage.list(Some("test-")).unwrap();
        assert_eq!(filtered_keys.len(), 2);
    }

    #[test]
    fn test_batch_upload() {
        let config = CloudStorageConfig::default();
        let mut storage = CloudStorage::new(config);
        let diff = create_test_diff();

        let diffs = vec![
            ("key1".to_string(), diff.clone()),
            ("key2".to_string(), diff.clone()),
            ("key3".to_string(), diff),
        ];

        let uploaded = batch_upload(&mut storage, &diffs).unwrap();
        assert_eq!(uploaded.len(), 3);
    }

    #[test]
    fn test_batch_download() {
        let config = CloudStorageConfig::default();
        let mut storage = CloudStorage::new(config);
        let diff = create_test_diff();

        storage.store("key1", &diff).unwrap();
        storage.store("key2", &diff).unwrap();

        let keys = vec!["key1".to_string(), "key2".to_string()];
        let downloaded = batch_download(&mut storage, &keys).unwrap();
        assert_eq!(downloaded.len(), 2);
    }

    #[test]
    fn test_cache_stats() {
        let config = CloudStorageConfig::default();
        let mut storage = CloudStorage::new(config);
        let diff = create_test_diff();

        let stats_before = storage.cache_stats();
        assert_eq!(stats_before.entries, 0);

        storage.store("key1", &diff).unwrap();
        storage.store("key2", &diff).unwrap();

        let stats_after = storage.cache_stats();
        assert_eq!(stats_after.entries, 2);
        assert!(stats_after.size_bytes > 0);
    }

    #[test]
    fn test_clear_cache() {
        let config = CloudStorageConfig::default();
        let mut storage = CloudStorage::new(config);
        let diff = create_test_diff();

        storage.store("key1", &diff).unwrap();
        storage.clear_cache();

        let stats = storage.cache_stats();
        assert_eq!(stats.entries, 0);
    }
}
