//! Migration Repository Trait
//!
//! Provides a clean abstraction for database migration operations, eliminating direct database
//! coupling from migration management components.

use async_trait::async_trait;
use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};
use std::sync::Arc;
use thiserror::Error;

/// Errors that can occur in migration repository operations
#[derive(Debug, Error)]
/// MigrationRepositoryError
///
/// Auto-generated documentation placeholder - enhance with specifics
pub enum MigrationRepositoryError {
    #[error("Database connection error: {0}")]
    // Connection variant
    Connection(String),
    #[error("Migration execution error: {0}")]
    // Execution variant
    Execution(String),
    #[error("Migration validation error: {0}")]
    // Validation variant
    Validation(String),
    #[error("Schema error: {0}")]
    // Schema variant
    Schema(String),
    #[error("File system error: {0}")]
    // FileSystem variant
    FileSystem(String),
    #[error("Transaction error: {0}")]
    // Transaction variant
    Transaction(String),
    #[error("Rollback error: {0}")]
    // Rollback variant
    Rollback(String),
}

/// MigrationRepositoryResult
pub type MigrationRepositoryResult<T> = Result<T, MigrationRepositoryError>;

/// Database migration definition
#[derive(Debug, Clone, Serialize, Deserialize)]
/// Migration
///
/// Auto-generated documentation placeholder - enhance with specifics
pub struct Migration {
    /// Id
    pub id: String,
    /// Version
    pub version: String,
    /// Name
    pub name: String,
    /// Description
    pub description: String,
    /// Up Sql
    pub up_sql: String,
    /// Down Sql
    pub down_sql: String,
    /// Checksum
    pub checksum: String,
    /// Created At
    pub created_at: DateTime<Utc>,
    /// Dependencies
    pub dependencies: Vec<String>,
    /// Tags
    pub tags: Vec<String>,
    /// Is Reversible
    pub is_reversible: bool,
}

impl Migration {
    pub fn new(
        version: String,
        name: String,
        description: String,
        up_sql: String,
        down_sql: String,
    ) -> Self {
        let id = format!("{}_{}", version, name);
        let checksum = Self::calculate_checksum(&up_sql, &down_sql);

        Self {
            id,
            version,
            name,
            description,
            up_sql,
            checksum,
            created_at: Utc::now(),
            dependencies: Vec::new(),
            tags: Vec::new(),
            is_reversible: !down_sql.is_empty(),
            down_sql,
        }
    }

    fn calculate_checksum(up_sql: &str, down_sql: &str) -> String {
        use std::collections::hash_map::DefaultHasher;
        use std::hash::{Hash, Hasher};

        let mut hasher = DefaultHasher::new();
        up_sql.hash(&mut hasher);
        down_sql.hash(&mut hasher);
        format!("{:x}", hasher.finish())
    }

    pub fn with_dependencies(mut self, dependencies: Vec<String>) -> Self {
        self.dependencies = dependencies;
        self
    }

    pub fn with_tags(mut self, tags: Vec<String>) -> Self {
        self.tags = tags;
        self
    }
}

/// Migration execution result
#[derive(Debug, Clone, Serialize, Deserialize)]
/// MigrationResult
///
/// Auto-generated documentation placeholder - enhance with specifics
pub struct MigrationResult {
    /// Migration Id
    pub migration_id: String,
    /// Executed At
    pub executed_at: DateTime<Utc>,
    /// Execution Time Ms
    pub execution_time_ms: u64,
    /// Success
    pub success: bool,
    /// Error Message
    pub error_message: Option<String>,
    /// Rows Affected
    pub rows_affected: Option<u64>,
}

/// Migration status information
#[derive(Debug, Clone, Serialize, Deserialize)]
/// MigrationStatus
///
/// Auto-generated documentation placeholder - enhance with specifics
pub enum MigrationStatus {
    // Pending variant
    Pending,
    // Applied variant
    Applied,
    // Failed variant
    Failed,
    // RolledBack variant
    RolledBack,
}

/// Applied migration record
#[derive(Debug, Clone, Serialize, Deserialize)]
/// AppliedMigration
///
/// Auto-generated documentation placeholder - enhance with specifics
pub struct AppliedMigration {
    /// Migration Id
    pub migration_id: String,
    /// Version
    pub version: String,
    /// Name
    pub name: String,
    /// Checksum
    pub checksum: String,
    /// Applied At
    pub applied_at: DateTime<Utc>,
    /// Execution Time Ms
    pub execution_time_ms: u64,
    /// Status
    pub status: MigrationStatus,
}

/// Migration plan for batch execution
#[derive(Debug, Clone)]
/// MigrationPlan
///
/// Auto-generated documentation placeholder - enhance with specifics
pub struct MigrationPlan {
    /// Migrations
    pub migrations: Vec<Migration>,
    /// Execution Order
    pub execution_order: Vec<String>,
    /// Estimated `Duration` Ms
    pub estimated_duration_ms: u64,
    /// Requires Transaction
    pub requires_transaction: bool,
}

impl MigrationPlan {
    pub fn new(migrations: Vec<Migration>) -> Self {
        let execution_order: Vec<String> = migrations.iter().map(|m| m.id.clone()).collect();
        let estimated_duration_ms = migrations.len() as u64 * 1000; // Rough estimate

        Self {
            migrations,
            execution_order,
            estimated_duration_ms,
            requires_transaction: true,
        }
    }

    pub fn migration_count(&self) -> usize {
        self.migrations.len()
    }

    pub fn is_empty(&self) -> bool {
        self.migrations.is_empty()
    }
}

/// Migration validation result
#[derive(Debug, Clone, Serialize, Deserialize)]
/// ValidationResult
///
/// Auto-generated documentation placeholder - enhance with specifics
pub struct ValidationResult {
    /// Is Valid
    pub is_valid: bool,
    /// Errors
    pub errors: Vec<String>,
    /// Warnings
    pub warnings: Vec<String>,
    /// Suggestions
    pub suggestions: Vec<String>,
}

/// Migration repository trait
#[async_trait]
/// MigrationRepository
///
/// Auto-generated documentation placeholder - enhance with specifics
pub trait MigrationRepository: Send + Sync {
    /// Initialize migration tracking schema
    async fn initialize_migration_schema(&self) -> MigrationRepositoryResult<()>;

    /// Apply a single migration
    async fn apply_migration(
        &self,
        migration: Migration,
    ) -> MigrationRepositoryResult<MigrationResult>;

    /// Apply multiple migrations in a transaction
    async fn apply_migrations(
        &self,
        plan: MigrationPlan,
    ) -> MigrationRepositoryResult<Vec<MigrationResult>>;

    /// Rollback a migration
    async fn rollback_migration(
        &self,
        migration_id: String,
    ) -> MigrationRepositoryResult<MigrationResult>;

    /// Get all applied migrations
    async fn get_applied_migrations(&self) -> MigrationRepositoryResult<Vec<AppliedMigration>>;

    /// Check if a migration has been applied
    async fn is_migration_applied(&self, migration_id: String) -> MigrationRepositoryResult<bool>;

    /// Get migration by ID
    async fn get_migration(
        &self,
        migration_id: String,
    ) -> MigrationRepositoryResult<Option<AppliedMigration>>;

    /// Validate a migration before application
    async fn validate_migration(
        &self,
        migration: &Migration,
    ) -> MigrationRepositoryResult<ValidationResult>;

    /// Validate migration dependencies
    async fn validate_dependencies(&self, migration: &Migration)
        -> MigrationRepositoryResult<bool>;

    /// Get pending migrations (not yet applied)
    async fn get_pending_migrations(
        &self,
        available: Vec<Migration>,
    ) -> MigrationRepositoryResult<Vec<Migration>>;

    /// Create migration plan from pending migrations
    async fn create_migration_plan(
        &self,
        migrations: Vec<Migration>,
    ) -> MigrationRepositoryResult<MigrationPlan>;

    /// Get migration history
    async fn get_migration_history(
        &self,
        limit: Option<u32>,
    ) -> MigrationRepositoryResult<Vec<AppliedMigration>>;

    /// Verify migration integrity (checksums)
    async fn verify_migration_integrity(&self) -> MigrationRepositoryResult<Vec<String>>;

    /// Get migration statistics
    async fn get_migration_stats(&self) -> MigrationRepositoryResult<MigrationStats>;

    /// Health check
    async fn health_check(&self) -> MigrationRepositoryResult<()>;
}

/// Migration statistics
#[derive(Debug, Clone, Serialize, Deserialize)]
/// MigrationStats
///
/// Auto-generated documentation placeholder - enhance with specifics
pub struct MigrationStats {
    /// Total Migrations
    pub total_migrations: u64,
    /// Applied Migrations
    pub applied_migrations: u64,
    /// Pending Migrations
    pub pending_migrations: u64,
    /// Failed Migrations
    pub failed_migrations: u64,
    /// Last Migration Date
    pub last_migration_date: Option<DateTime<Utc>>,
    /// Average Execution Time Ms
    pub average_execution_time_ms: f64,
    /// Total Execution Time Ms
    pub total_execution_time_ms: u64,
}

/// Mock implementation for testing
#[derive(Debug)]
pub struct MockMigrationRepository {
    applied_migrations: Arc<tokio::sync::RwLock<Vec<AppliedMigration>>>,
    should_fail: Arc<std::sync::atomic::AtomicBool>,
    schema_initialized: Arc<std::sync::atomic::AtomicBool>,
}

impl MockMigrationRepository {
    pub fn new() -> Self {
        Self {
            applied_migrations: Arc::new(tokio::sync::RwLock::new(Vec::new())),
            should_fail: Arc::new(std::sync::atomic::AtomicBool::new(false)),
            schema_initialized: Arc::new(std::sync::atomic::AtomicBool::new(false)),
        }
    }

    pub fn set_should_fail(&self, should_fail: bool) {
        self.should_fail
            .store(should_fail, std::sync::atomic::Ordering::Relaxed);
    }

    pub async fn get_applied_count(&self) -> usize {
        self.applied_migrations.read().await.len()
    }

    pub async fn clear_migrations(&self) {
        self.applied_migrations.write().await.clear();
        self.schema_initialized
            .store(false, std::sync::atomic::Ordering::Relaxed);
    }

    pub fn is_schema_initialized(&self) -> bool {
        self.schema_initialized
            .load(std::sync::atomic::Ordering::Relaxed)
    }
}

#[async_trait]
impl MigrationRepository for MockMigrationRepository {
    async fn initialize_migration_schema(&self) -> MigrationRepositoryResult<()> {
        if self.should_fail.load(std::sync::atomic::Ordering::Relaxed) {
            return Err(MigrationRepositoryError::Schema("Mock failure".to_string()));
        }
        self.schema_initialized
            .store(true, std::sync::atomic::Ordering::Relaxed);
        Ok(())
    }

    async fn apply_migration(
        &self,
        migration: Migration,
    ) -> MigrationRepositoryResult<MigrationResult> {
        if self.should_fail.load(std::sync::atomic::Ordering::Relaxed) {
            return Err(MigrationRepositoryError::Execution(
                "Mock failure".to_string(),
            ));
        }

        let start_time = std::time::Instant::now();

        // Simulate migration execution
        tokio::time::sleep(tokio::time::Duration::from_millis(10)).await;

        let execution_time_ms = start_time.elapsed().as_millis() as u64;

        let applied = AppliedMigration {
            migration_id: migration.id.clone(),
            version: migration.version.clone(),
            name: migration.name.clone(),
            checksum: migration.checksum.clone(),
            applied_at: Utc::now(),
            execution_time_ms,
            status: MigrationStatus::Applied,
        };

        self.applied_migrations.write().await.push(applied);

        Ok(MigrationResult {
            migration_id: migration.id,
            executed_at: Utc::now(),
            execution_time_ms,
            success: true,
            error_message: None,
            rows_affected: Some(1),
        })
    }

    async fn apply_migrations(
        &self,
        plan: MigrationPlan,
    ) -> MigrationRepositoryResult<Vec<MigrationResult>> {
        if self.should_fail.load(std::sync::atomic::Ordering::Relaxed) {
            return Err(MigrationRepositoryError::Execution(
                "Mock failure".to_string(),
            ));
        }

        let mut results = Vec::new();
        for migration in plan.migrations {
            let result = self.apply_migration(migration).await?;
            results.push(result);
        }
        // Ok variant
        Ok(results)
    }

    async fn rollback_migration(
        &self,
        migration_id: String,
    ) -> MigrationRepositoryResult<MigrationResult> {
        if self.should_fail.load(std::sync::atomic::Ordering::Relaxed) {
            return Err(MigrationRepositoryError::Rollback(
                "Mock failure".to_string(),
            ));
        }

        let mut applied = self.applied_migrations.write().await;
        if let Some(pos) = applied.iter().position(|m| m.migration_id == migration_id) {
            applied.remove(pos);
        }

        Ok(MigrationResult {
            migration_id,
            executed_at: Utc::now(),
            execution_time_ms: 50,
            success: true,
            error_message: None,
            rows_affected: Some(1),
        })
    }

    async fn get_applied_migrations(&self) -> MigrationRepositoryResult<Vec<AppliedMigration>> {
        Ok(self.applied_migrations.read().await.clone())
    }

    async fn is_migration_applied(&self, migration_id: String) -> MigrationRepositoryResult<bool> {
        let applied = self.applied_migrations.read().await;
        Ok(applied.iter().any(|m| m.migration_id == migration_id))
    }

    async fn get_migration(
        &self,
        migration_id: String,
    ) -> MigrationRepositoryResult<Option<AppliedMigration>> {
        let applied = self.applied_migrations.read().await;
        Ok(applied
            .iter()
            .find(|m| m.migration_id == migration_id)
            .cloned())
    }

    async fn validate_migration(
        &self,
        _migration: &Migration,
    ) -> MigrationRepositoryResult<ValidationResult> {
        if self.should_fail.load(std::sync::atomic::Ordering::Relaxed) {
            return Ok(ValidationResult {
                is_valid: false,
                errors: vec!["Mock validation error".to_string()],
                warnings: Vec::new(),
                suggestions: Vec::new(),
            });
        }

        Ok(ValidationResult {
            is_valid: true,
            errors: Vec::new(),
            warnings: Vec::new(),
            suggestions: Vec::new(),
        })
    }

    async fn validate_dependencies(
        &self,
        migration: &Migration,
    ) -> MigrationRepositoryResult<bool> {
        let applied = self.applied_migrations.read().await;

        for dep in &migration.dependencies {
            if !applied.iter().any(|m| m.migration_id == *dep) {
                return Ok(false);
            }
        }
        // Ok variant
        Ok(true)
    }

    async fn get_pending_migrations(
        &self,
        available: Vec<Migration>,
    ) -> MigrationRepositoryResult<Vec<Migration>> {
        let applied = self.applied_migrations.read().await;
        let applied_ids: std::collections::HashSet<_> =
            applied.iter().map(|m| &m.migration_id).collect();

        let pending: Vec<Migration> = available
            .into_iter()
            .filter(|m| !applied_ids.contains(&m.id))
            .collect();

        // Ok variant
        Ok(pending)
    }

    async fn create_migration_plan(
        &self,
        migrations: Vec<Migration>,
    ) -> MigrationRepositoryResult<MigrationPlan> {
        Ok(MigrationPlan::new(migrations))
    }

    async fn get_migration_history(
        &self,
        limit: Option<u32>,
    ) -> MigrationRepositoryResult<Vec<AppliedMigration>> {
        let applied = self.applied_migrations.read().await;
        let mut history = applied.clone();
        history.sort_by(|a, b| b.applied_at.cmp(&a.applied_at)); // Most recent first

        if let Some(limit) = limit {
            history.truncate(limit as usize);
        }

        // Ok variant
        Ok(history)
    }

    async fn verify_migration_integrity(&self) -> MigrationRepositoryResult<Vec<String>> {
        if self.should_fail.load(std::sync::atomic::Ordering::Relaxed) {
            return Ok(vec!["Mock integrity violation".to_string()]);
        }
        Ok(Vec::new()) // No violations
    }

    async fn get_migration_stats(&self) -> MigrationRepositoryResult<MigrationStats> {
        let applied = self.applied_migrations.read().await;
        let total = applied.len() as u64;

        let last_migration_date = applied.iter().map(|m| m.applied_at).max();

        let total_execution_time: u64 = applied.iter().map(|m| m.execution_time_ms).sum();

        let average_execution_time = if total > 0 {
            total_execution_time as f64 / total as f64
        } else {
            0.0
        };

        Ok(MigrationStats {
            total_migrations: total,
            applied_migrations: total,
            pending_migrations: 0,
            failed_migrations: 0,
            last_migration_date,
            average_execution_time_ms: average_execution_time,
            total_execution_time_ms: total_execution_time,
        })
    }

    async fn health_check(&self) -> MigrationRepositoryResult<()> {
        if self.should_fail.load(std::sync::atomic::Ordering::Relaxed) {
            return Err(MigrationRepositoryError::Connection(
                "Mock failure".to_string(),
            ));
        }
        Ok(())
    }
}

impl Default for MockMigrationRepository {
    fn default() -> Self {
        Self::new()
    }
}

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

    #[tokio::test]
    async fn test_migration_creation() {
        let migration = Migration::new(
            "001".to_string(),
            "initial".to_string(),
            "Initial migration".to_string(),
            "CREATE TABLE test (id INTEGER)".to_string(),
            "DROP TABLE test".to_string(),
        );

        assert_eq!(migration.version, "001");
        assert_eq!(migration.name, "initial");
        assert!(migration.is_reversible);
        assert!(!migration.checksum.is_empty());
    }

    #[tokio::test]
    async fn test_mock_migration_repository() {
        let repo = MockMigrationRepository::new();

        // Test schema initialization
        assert!(repo.initialize_migration_schema().await.is_ok());
        assert!(repo.is_schema_initialized());

        // Test health check
        assert!(repo.health_check().await.is_ok());

        // Test migration application
        let migration = Migration::new(
            "001".to_string(),
            "test".to_string(),
            "Test migration".to_string(),
            "SELECT 1".to_string(),
            "SELECT 0".to_string(),
        );

        let result = repo.apply_migration(migration.clone()).await.unwrap();
        assert!(result.success);
        assert_eq!(repo.get_applied_count().await, 1);

        // Test migration lookup
        let applied = repo
            .is_migration_applied(migration.id.clone())
            .await
            .unwrap();
        assert!(applied);
    }

    #[tokio::test]
    async fn test_migration_plan() {
        let migrations = vec![
            Migration::new(
                "001".to_string(),
                "first".to_string(),
                "First".to_string(),
                "SELECT 1".to_string(),
                "".to_string(),
            ),
            Migration::new(
                "002".to_string(),
                "second".to_string(),
                "Second".to_string(),
                "SELECT 2".to_string(),
                "".to_string(),
            ),
        ];

        let plan = MigrationPlan::new(migrations);
        assert_eq!(plan.migration_count(), 2);
        assert!(!plan.is_empty());
        assert_eq!(plan.execution_order.len(), 2);
    }
}
