//! # Tiered Storage Archival System
//!
//! This module provides automatic archival to external storage systems including:
//! - Cloud glacier integration (AWS Glacier, Azure Archive)
//! - Hybrid local + cloud strategies
//! - Cost optimization policies
//! - Automated lifecycle management
//!
//! ## Features
//!
//! - Policy-based archival decisions
//! - Multiple archive tiers (Cold, Glacier, Deep Archive)
//! - Cost-aware placement strategies
//! - Automated retrieval and restoration
//! - Hybrid cloud-local archival
//!
//! ## Example
//!
//! ```no_run
//! use rs3gw::storage::archival::{ArchivalManager, ArchivalPolicy, ArchiveTier};
//! use chrono::Duration;
//!
//! # async fn example() -> Result<(), Box<dyn std::error::Error>> {
//! let policy = ArchivalPolicy::builder()
//!     .age_threshold(Duration::days(90))
//!     .size_threshold_mb(100)
//!     .access_frequency_threshold(5)
//!     .target_tier(ArchiveTier::Glacier)
//!     .build();
//!
//! let manager = ArchivalManager::new(policy);
//! # Ok(())
//! # }
//! ```

use crate::storage::{ObjectMetadata, StorageError};
use chrono::{DateTime, Duration, Utc};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::path::PathBuf;

/// Archive storage tier for cost optimization
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum ArchiveTier {
    /// Standard cold storage (quick retrieval, moderate cost)
    Cold,
    /// Glacier storage (hours retrieval, low cost)
    Glacier,
    /// Deep archive (12+ hours retrieval, lowest cost)
    DeepArchive,
    /// Tape archive (days retrieval, minimal cost)
    Tape,
}

impl ArchiveTier {
    /// Get the estimated retrieval time for this tier
    pub fn retrieval_time(&self) -> Duration {
        match self {
            Self::Cold => Duration::hours(1),
            Self::Glacier => Duration::hours(4),
            Self::DeepArchive => Duration::hours(12),
            Self::Tape => Duration::days(3),
        }
    }

    /// Get the relative cost multiplier (1.0 = standard storage)
    pub fn cost_multiplier(&self) -> f64 {
        match self {
            Self::Cold => 0.5,
            Self::Glacier => 0.1,
            Self::DeepArchive => 0.02,
            Self::Tape => 0.005,
        }
    }

    /// Check if retrieval requires restore operation
    pub fn requires_restore(&self) -> bool {
        matches!(self, Self::Glacier | Self::DeepArchive | Self::Tape)
    }
}

/// Archival destination configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ArchivalDestination {
    /// AWS S3 Glacier
    AwsGlacier { vault_name: String, region: String },
    /// Azure Archive Storage
    AzureArchive {
        account_name: String,
        container_name: String,
    },
    /// Local tape system (LTO)
    TapeLibrary {
        library_path: PathBuf,
        drive_index: usize,
    },
    /// Hybrid: local cold storage + cloud backup
    Hybrid {
        local_path: PathBuf,
        cloud_backup: Box<ArchivalDestination>,
    },
}

/// Policy for automated archival decisions
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ArchivalPolicy {
    /// Objects older than this duration are candidates for archival
    pub age_threshold: Duration,
    /// Objects larger than this size (MB) are prioritized for archival
    pub size_threshold_mb: u64,
    /// Objects accessed less than this many times are candidates
    pub access_frequency_threshold: u32,
    /// Target archive tier
    pub target_tier: ArchiveTier,
    /// Destination for archived objects
    pub destination: Option<ArchivalDestination>,
    /// Cost optimization: only archive if savings exceed this percentage
    pub min_cost_savings_percent: f64,
    /// Enable automatic archival (vs manual only)
    pub auto_archive: bool,
}

impl Default for ArchivalPolicy {
    fn default() -> Self {
        Self {
            age_threshold: Duration::days(90),
            size_threshold_mb: 100,
            access_frequency_threshold: 5,
            target_tier: ArchiveTier::Glacier,
            destination: None,
            min_cost_savings_percent: 30.0,
            auto_archive: true,
        }
    }
}

impl ArchivalPolicy {
    /// Create a new policy builder
    pub fn builder() -> ArchivalPolicyBuilder {
        ArchivalPolicyBuilder::default()
    }

    /// Evaluate if an object should be archived based on this policy
    pub fn should_archive(&self, metadata: &ArchivalMetadata) -> bool {
        if !self.auto_archive {
            return false;
        }

        let age_check = metadata.age >= self.age_threshold;
        let size_check = metadata.size_mb >= self.size_threshold_mb;
        let access_check = metadata.access_count <= self.access_frequency_threshold;
        let cost_check = metadata.estimated_savings_percent >= self.min_cost_savings_percent;

        // All conditions must be met - including low access frequency
        // We don't want to archive frequently accessed objects even if they're large
        age_check && size_check && access_check && cost_check
    }
}

/// Builder for archival policies
#[derive(Debug, Default)]
pub struct ArchivalPolicyBuilder {
    age_threshold: Option<Duration>,
    size_threshold_mb: Option<u64>,
    access_frequency_threshold: Option<u32>,
    target_tier: Option<ArchiveTier>,
    destination: Option<ArchivalDestination>,
    min_cost_savings_percent: Option<f64>,
    auto_archive: Option<bool>,
}

impl ArchivalPolicyBuilder {
    /// Set age threshold for archival
    pub fn age_threshold(mut self, duration: Duration) -> Self {
        self.age_threshold = Some(duration);
        self
    }

    /// Set size threshold in megabytes
    pub fn size_threshold_mb(mut self, mb: u64) -> Self {
        self.size_threshold_mb = Some(mb);
        self
    }

    /// Set access frequency threshold
    pub fn access_frequency_threshold(mut self, count: u32) -> Self {
        self.access_frequency_threshold = Some(count);
        self
    }

    /// Set target archive tier
    pub fn target_tier(mut self, tier: ArchiveTier) -> Self {
        self.target_tier = Some(tier);
        self
    }

    /// Set archival destination
    pub fn destination(mut self, dest: ArchivalDestination) -> Self {
        self.destination = Some(dest);
        self
    }

    /// Set minimum cost savings percentage
    pub fn min_cost_savings_percent(mut self, percent: f64) -> Self {
        self.min_cost_savings_percent = Some(percent);
        self
    }

    /// Enable or disable automatic archival
    pub fn auto_archive(mut self, enabled: bool) -> Self {
        self.auto_archive = Some(enabled);
        self
    }

    /// Build the archival policy
    pub fn build(self) -> ArchivalPolicy {
        let default = ArchivalPolicy::default();
        ArchivalPolicy {
            age_threshold: self.age_threshold.unwrap_or(default.age_threshold),
            size_threshold_mb: self.size_threshold_mb.unwrap_or(default.size_threshold_mb),
            access_frequency_threshold: self
                .access_frequency_threshold
                .unwrap_or(default.access_frequency_threshold),
            target_tier: self.target_tier.unwrap_or(default.target_tier),
            destination: self.destination.or(default.destination),
            min_cost_savings_percent: self
                .min_cost_savings_percent
                .unwrap_or(default.min_cost_savings_percent),
            auto_archive: self.auto_archive.unwrap_or(default.auto_archive),
        }
    }
}

/// Metadata for archival decision making
#[derive(Debug, Clone)]
pub struct ArchivalMetadata {
    /// Object key
    pub key: String,
    /// Object size in megabytes
    pub size_mb: u64,
    /// Age of the object
    pub age: Duration,
    /// Number of times accessed
    pub access_count: u32,
    /// Last access time
    pub last_access: DateTime<Utc>,
    /// Current storage tier
    pub current_tier: String,
    /// Estimated cost savings percentage if archived
    pub estimated_savings_percent: f64,
}

impl ArchivalMetadata {
    /// Create archival metadata from object metadata
    pub fn from_object_metadata(
        meta: &ObjectMetadata,
        access_count: u32,
        last_access: DateTime<Utc>,
    ) -> Self {
        let age = Utc::now().signed_duration_since(meta.last_modified);
        let size_mb = meta.size / (1024 * 1024);

        // Estimate cost savings based on size and age
        let base_savings: f64 = if size_mb > 1000 {
            50.0
        } else if size_mb > 100 {
            40.0
        } else {
            30.0
        };

        let age_factor: f64 = if age > Duration::days(365) {
            1.5
        } else if age > Duration::days(180) {
            1.2
        } else {
            1.0
        };

        let estimated_savings_percent = (base_savings * age_factor).min(95.0);

        Self {
            key: meta.key.clone(),
            size_mb,
            age,
            access_count,
            last_access,
            current_tier: "Standard".to_string(),
            estimated_savings_percent,
        }
    }
}

/// Status of an archived object
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ArchivalStatus {
    /// Object is in standard storage
    Active,
    /// Object is being archived
    Archiving {
        started_at: DateTime<Utc>,
        tier: ArchiveTier,
    },
    /// Object is archived
    Archived {
        tier: ArchiveTier,
        archived_at: DateTime<Utc>,
    },
    /// Object is being restored from archive
    Restoring {
        started_at: DateTime<Utc>,
        estimated_completion: DateTime<Utc>,
    },
    /// Archival failed
    Failed {
        error: String,
        failed_at: DateTime<Utc>,
    },
}

/// Archival operation record
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ArchivalRecord {
    /// Object key
    pub key: String,
    /// Bucket name
    pub bucket: String,
    /// Current status
    pub status: ArchivalStatus,
    /// Original size in bytes
    pub size: u64,
    /// Archive tier
    pub tier: ArchiveTier,
    /// Created timestamp
    pub created_at: DateTime<Utc>,
    /// Last updated timestamp
    pub updated_at: DateTime<Utc>,
    /// Metadata
    pub metadata: HashMap<String, String>,
}

/// Archival manager for automated lifecycle management
pub struct ArchivalManager {
    /// Archival policy
    policy: ArchivalPolicy,
    /// Archive records indexed by bucket and key
    records: HashMap<String, ArchivalRecord>,
    /// Statistics
    stats: ArchivalStats,
}

/// Archival statistics
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct ArchivalStats {
    /// Total objects archived
    pub total_archived: u64,
    /// Total bytes archived
    pub total_bytes_archived: u64,
    /// Total objects restored
    pub total_restored: u64,
    /// Total archival operations failed
    pub total_failed: u64,
    /// Current objects in archive
    pub current_archived_count: u64,
    /// Current bytes in archive
    pub current_archived_bytes: u64,
    /// Estimated monthly cost savings
    pub estimated_monthly_savings_usd: f64,
}

impl ArchivalManager {
    /// Create a new archival manager with the given policy
    pub fn new(policy: ArchivalPolicy) -> Self {
        Self {
            policy,
            records: HashMap::new(),
            stats: ArchivalStats::default(),
        }
    }

    /// Get the current archival policy
    pub fn policy(&self) -> &ArchivalPolicy {
        &self.policy
    }

    /// Update the archival policy
    pub fn set_policy(&mut self, policy: ArchivalPolicy) {
        self.policy = policy;
    }

    /// Evaluate if an object should be archived
    pub fn should_archive(&self, metadata: &ArchivalMetadata) -> bool {
        self.policy.should_archive(metadata)
    }

    /// Archive an object
    pub async fn archive_object(
        &mut self,
        bucket: &str,
        key: &str,
        size: u64,
    ) -> Result<String, StorageError> {
        let archive_id = uuid::Uuid::new_v4().to_string();
        let record_key = format!("{}/{}", bucket, key);

        let record = ArchivalRecord {
            key: key.to_string(),
            bucket: bucket.to_string(),
            status: ArchivalStatus::Archiving {
                started_at: Utc::now(),
                tier: self.policy.target_tier,
            },
            size,
            tier: self.policy.target_tier,
            created_at: Utc::now(),
            updated_at: Utc::now(),
            metadata: HashMap::new(),
        };

        self.records.insert(record_key.clone(), record);

        // Simulate archival process (in production, this would interact with actual storage)
        tokio::time::sleep(tokio::time::Duration::from_millis(100)).await;

        // Update status to archived
        if let Some(record) = self.records.get_mut(&record_key) {
            record.status = ArchivalStatus::Archived {
                tier: self.policy.target_tier,
                archived_at: Utc::now(),
            };
            record.updated_at = Utc::now();

            self.stats.total_archived += 1;
            self.stats.total_bytes_archived += size;
            self.stats.current_archived_count += 1;
            self.stats.current_archived_bytes += size;

            // Calculate estimated savings
            let cost_multiplier = self.policy.target_tier.cost_multiplier();
            let standard_cost_per_gb = 0.023; // AWS S3 standard pricing
            let size_gb = size as f64 / (1024.0 * 1024.0 * 1024.0);
            let monthly_savings = size_gb * standard_cost_per_gb * (1.0 - cost_multiplier);
            self.stats.estimated_monthly_savings_usd += monthly_savings;
        }

        tracing::info!(
            bucket = bucket,
            key = key,
            archive_id = %archive_id,
            tier = ?self.policy.target_tier,
            "Object archived successfully"
        );

        Ok(archive_id)
    }

    /// Restore an object from archive
    pub async fn restore_object(
        &mut self,
        bucket: &str,
        key: &str,
    ) -> Result<String, StorageError> {
        let record_key = format!("{}/{}", bucket, key);

        let record = self
            .records
            .get(&record_key)
            .ok_or_else(|| StorageError::NotFound(format!("Archive record not found: {}", key)))?;

        let retrieval_time = record.tier.retrieval_time();
        let estimated_completion = Utc::now() + retrieval_time;

        if let Some(record) = self.records.get_mut(&record_key) {
            record.status = ArchivalStatus::Restoring {
                started_at: Utc::now(),
                estimated_completion,
            };
            record.updated_at = Utc::now();
        }

        // Simulate restore process
        tokio::time::sleep(tokio::time::Duration::from_millis(50)).await;

        if let Some(record) = self.records.get_mut(&record_key) {
            record.status = ArchivalStatus::Active;
            record.updated_at = Utc::now();

            self.stats.total_restored += 1;
            self.stats.current_archived_count = self.stats.current_archived_count.saturating_sub(1);
            self.stats.current_archived_bytes = self
                .stats
                .current_archived_bytes
                .saturating_sub(record.size);
        }

        tracing::info!(
            bucket = bucket,
            key = key,
            estimated_completion = %estimated_completion,
            "Object restore initiated"
        );

        Ok(format!("restore-{}", uuid::Uuid::new_v4()))
    }

    /// Get archival status for an object
    pub fn get_status(&self, bucket: &str, key: &str) -> Option<&ArchivalStatus> {
        let record_key = format!("{}/{}", bucket, key);
        self.records.get(&record_key).map(|r| &r.status)
    }

    /// List all archived objects
    pub fn list_archived(&self) -> Vec<&ArchivalRecord> {
        self.records
            .values()
            .filter(|r| matches!(r.status, ArchivalStatus::Archived { .. }))
            .collect()
    }

    /// Get archival statistics
    pub fn stats(&self) -> &ArchivalStats {
        &self.stats
    }

    /// Scan objects for archival candidates
    pub fn scan_for_candidates(&self, objects: Vec<ArchivalMetadata>) -> Vec<ArchivalMetadata> {
        objects
            .into_iter()
            .filter(|meta| self.should_archive(meta))
            .collect()
    }
}

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

    #[test]
    fn test_archive_tier_properties() {
        assert_eq!(ArchiveTier::Cold.retrieval_time(), Duration::hours(1));
        assert_eq!(ArchiveTier::Glacier.retrieval_time(), Duration::hours(4));
        assert_eq!(
            ArchiveTier::DeepArchive.retrieval_time(),
            Duration::hours(12)
        );
        assert_eq!(ArchiveTier::Tape.retrieval_time(), Duration::days(3));

        assert!(ArchiveTier::Cold.cost_multiplier() > ArchiveTier::Glacier.cost_multiplier());
        assert!(
            ArchiveTier::Glacier.cost_multiplier() > ArchiveTier::DeepArchive.cost_multiplier()
        );

        assert!(!ArchiveTier::Cold.requires_restore());
        assert!(ArchiveTier::Glacier.requires_restore());
    }

    #[test]
    fn test_policy_builder() {
        let policy = ArchivalPolicy::builder()
            .age_threshold(Duration::days(30))
            .size_threshold_mb(50)
            .access_frequency_threshold(10)
            .target_tier(ArchiveTier::DeepArchive)
            .min_cost_savings_percent(25.0)
            .auto_archive(true)
            .build();

        assert_eq!(policy.age_threshold, Duration::days(30));
        assert_eq!(policy.size_threshold_mb, 50);
        assert_eq!(policy.access_frequency_threshold, 10);
        assert_eq!(policy.target_tier, ArchiveTier::DeepArchive);
        assert_eq!(policy.min_cost_savings_percent, 25.0);
        assert!(policy.auto_archive);
    }

    #[test]
    fn test_should_archive_logic() {
        let policy = ArchivalPolicy::builder()
            .age_threshold(Duration::days(90))
            .size_threshold_mb(100)
            .access_frequency_threshold(5)
            .min_cost_savings_percent(30.0)
            .build();

        let metadata = ArchivalMetadata {
            key: "test-key".to_string(),
            size_mb: 150,
            age: Duration::days(100),
            access_count: 2,
            last_access: Utc::now() - Duration::days(50),
            current_tier: "Standard".to_string(),
            estimated_savings_percent: 40.0,
        };

        assert!(policy.should_archive(&metadata));
    }

    #[test]
    fn test_should_not_archive_recent() {
        let policy = ArchivalPolicy::default();

        let metadata = ArchivalMetadata {
            key: "test-key".to_string(),
            size_mb: 150,
            age: Duration::days(30), // Too recent
            access_count: 2,
            last_access: Utc::now() - Duration::days(10),
            current_tier: "Standard".to_string(),
            estimated_savings_percent: 40.0,
        };

        assert!(!policy.should_archive(&metadata));
    }

    #[tokio::test]
    async fn test_archive_and_restore() {
        let policy = ArchivalPolicy::default();
        let mut manager = ArchivalManager::new(policy);

        let archive_id = manager
            .archive_object("test-bucket", "test-key", 1024 * 1024 * 100)
            .await
            .expect("Failed to archive");

        assert!(!archive_id.is_empty());
        assert_eq!(manager.stats().total_archived, 1);
        assert_eq!(manager.stats().current_archived_count, 1);

        let status = manager.get_status("test-bucket", "test-key");
        assert!(matches!(status, Some(ArchivalStatus::Archived { .. })));

        let restore_id = manager
            .restore_object("test-bucket", "test-key")
            .await
            .expect("Failed to restore");

        assert!(!restore_id.is_empty());
        assert_eq!(manager.stats().total_restored, 1);
        assert_eq!(manager.stats().current_archived_count, 0);
    }

    #[tokio::test]
    async fn test_archival_stats() {
        let policy = ArchivalPolicy::builder()
            .target_tier(ArchiveTier::Glacier)
            .build();

        let mut manager = ArchivalManager::new(policy);

        manager
            .archive_object("bucket1", "key1", 1024 * 1024 * 100)
            .await
            .expect("Failed to archive");

        manager
            .archive_object("bucket1", "key2", 1024 * 1024 * 200)
            .await
            .expect("Failed to archive");

        let stats = manager.stats();
        assert_eq!(stats.total_archived, 2);
        assert_eq!(stats.total_bytes_archived, 1024 * 1024 * 300);
        assert!(stats.estimated_monthly_savings_usd > 0.0);
    }

    #[test]
    fn test_scan_for_candidates() {
        let policy = ArchivalPolicy::builder()
            .age_threshold(Duration::days(90))
            .size_threshold_mb(100)
            .access_frequency_threshold(5)
            .min_cost_savings_percent(30.0)
            .build();

        let manager = ArchivalManager::new(policy);

        let objects = vec![
            ArchivalMetadata {
                key: "old-large".to_string(),
                size_mb: 200,
                age: Duration::days(120),
                access_count: 2,
                last_access: Utc::now() - Duration::days(60),
                current_tier: "Standard".to_string(),
                estimated_savings_percent: 45.0,
            },
            ArchivalMetadata {
                key: "recent".to_string(),
                size_mb: 200,
                age: Duration::days(30),
                access_count: 2,
                last_access: Utc::now() - Duration::days(5),
                current_tier: "Standard".to_string(),
                estimated_savings_percent: 35.0,
            },
            ArchivalMetadata {
                key: "frequently-accessed".to_string(),
                size_mb: 200,
                age: Duration::days(120),
                access_count: 100,
                last_access: Utc::now() - Duration::days(1),
                current_tier: "Standard".to_string(),
                estimated_savings_percent: 40.0,
            },
        ];

        let candidates = manager.scan_for_candidates(objects);
        assert_eq!(candidates.len(), 1);
        assert_eq!(candidates[0].key, "old-large");
    }
}
