//! Database integrity verification operations.
//!
//! This module provides:
//! - **Schema validation**: Verify all entities match their schemas
//! - **Reference integrity**: Check edge consistency, orphaned data
//! - **Embedding verification**: Ensure all embeddings are loadable
//! - **Checksum verification**: Detect data corruption
//!
//! # Verification Levels
//!
//! - **Quick**: Basic checks (schema existence, RocksDB health)
//! - **Standard**: Schema validation, edge consistency
//! - **Deep**: Full verification including embedding load tests
//!
//! # Example
//!
//! ```rust,no_run
//! use percolate_rocks::admin::VerificationManager;
//!
//! # async fn example() -> anyhow::Result<()> {
//! let verify_mgr = VerificationManager::new("/var/lib/rem/db")?;
//!
//! // Run standard verification
//! let report = verify_mgr.verify_database(None).await?;
//!
//! if !report.is_healthy() {
//!     println!("Issues found:");
//!     for issue in report.issues {
//!         println!("- {}", issue);
//!     }
//! }
//! # Ok(())
//! # }
//! ```

use anyhow::Result;
use serde::{Deserialize, Serialize};
use std::path::{Path, PathBuf};

/// Manages database verification operations.
///
/// Provides comprehensive checks for data integrity and consistency.
pub struct VerificationManager {
    /// Path to RocksDB database
    _db_path: PathBuf,

    /// RocksDB instance (not yet implemented)
    _db: (),
}

impl VerificationManager {
    /// Create new verification manager.
    ///
    /// # Arguments
    ///
    /// * `db_path` - Path to RocksDB database
    ///
    /// # Returns
    ///
    /// Configured `VerificationManager` instance
    ///
    /// # Errors
    ///
    /// Returns error if database path invalid or cannot be opened
    pub fn new(_db_path: &Path) -> Result<Self> {
        todo!("Open RocksDB in read-only mode")
    }

    /// Verify entire database.
    ///
    /// Runs all verification checks and returns comprehensive report.
    ///
    /// # Arguments
    ///
    /// * `level` - Verification level (None = standard)
    ///
    /// # Returns
    ///
    /// `VerificationReport` with all issues found
    ///
    /// # Errors
    ///
    /// Returns error only if verification cannot run (not if issues found)
    ///
    /// # Example
    ///
    /// ```rust,no_run
    /// # async fn example() -> anyhow::Result<()> {
    /// # use percolate_rocks::admin::{VerificationManager, VerificationLevel};
    /// # let verify_mgr = VerificationManager::new("/var/lib/rem/db")?;
    /// let report = verify_mgr.verify_database(Some(VerificationLevel::Deep)).await?;
    /// println!("Checked {} entities, found {} issues",
    ///     report.entities_checked,
    ///     report.issues.len()
    /// );
    /// # Ok(())
    /// # }
    /// ```
    pub async fn verify_database(
        &self,
        _level: Option<VerificationLevel>,
    ) -> Result<VerificationReport> {
        todo!(
            "Run checks based on level:
            Quick: RocksDB health, schema registry
            Standard: + schema validation, edge consistency
            Deep: + embedding load tests, index verification"
        )
    }

    /// Verify schema compliance.
    ///
    /// Checks that all entities validate against their schemas.
    ///
    /// # Returns
    ///
    /// `VerificationReport` with schema validation issues
    ///
    /// # Example
    ///
    /// ```rust,no_run
    /// # async fn example() -> anyhow::Result<()> {
    /// # use percolate_rocks::admin::VerificationManager;
    /// # let verify_mgr = VerificationManager::new("/var/lib/rem/db")?;
    /// let report = verify_mgr.verify_schemas().await?;
    /// # Ok(())
    /// # }
    /// ```
    pub async fn verify_schemas(&self) -> Result<VerificationReport> {
        todo!(
            "1. Get all schema definitions
            2. Scan all entities
            3. Validate each entity against its schema
            4. Report validation failures"
        )
    }

    /// Verify edge consistency.
    ///
    /// Checks that all edges have valid source and destination entities.
    ///
    /// # Returns
    ///
    /// `VerificationReport` with orphaned or invalid edges
    ///
    /// # Example
    ///
    /// ```rust,no_run
    /// # async fn example() -> anyhow::Result<()> {
    /// # use percolate_rocks::admin::VerificationManager;
    /// # let verify_mgr = VerificationManager::new("/var/lib/rem/db")?;
    /// let report = verify_mgr.verify_edges().await?;
    /// # Ok(())
    /// # }
    /// ```
    pub async fn verify_edges(&self) -> Result<VerificationReport> {
        todo!(
            "1. Scan edges CF
            2. For each edge:
               - Check src entity exists
               - Check dst entity exists
               - Check reverse edge exists in edges_reverse CF
            3. Report orphaned or inconsistent edges"
        )
    }

    /// Verify embeddings.
    ///
    /// Checks that all embeddings are loadable and have correct dimensions.
    ///
    /// # Returns
    ///
    /// `VerificationReport` with embedding issues
    ///
    /// # Example
    ///
    /// ```rust,no_run
    /// # async fn example() -> anyhow::Result<()> {
    /// # use percolate_rocks::admin::VerificationManager;
    /// # let verify_mgr = VerificationManager::new("/var/lib/rem/db")?;
    /// let report = verify_mgr.verify_embeddings().await?;
    /// # Ok(())
    /// # }
    /// ```
    pub async fn verify_embeddings(&self) -> Result<VerificationReport> {
        todo!(
            "1. Scan embeddings CF
            2. For each embedding:
               - Check entity exists
               - Verify vector can be deserialized
               - Check dimension matches schema
            3. Report corrupted or orphaned embeddings"
        )
    }

    /// Verify indexes.
    ///
    /// Checks that indexes are consistent with entity data.
    ///
    /// # Returns
    ///
    /// `VerificationReport` with index inconsistencies
    ///
    /// # Example
    ///
    /// ```rust,no_run
    /// # async fn example() -> anyhow::Result<()> {
    /// # use percolate_rocks::admin::VerificationManager;
    /// # let verify_mgr = VerificationManager::new("/var/lib/rem/db")?;
    /// let report = verify_mgr.verify_indexes().await?;
    /// # Ok(())
    /// # }
    /// ```
    pub async fn verify_indexes(&self) -> Result<VerificationReport> {
        todo!(
            "1. Sample entities
            2. Check field indexes match entity values
            3. Check key index matches entity keys
            4. Report index mismatches"
        )
    }
}

/// Verification level controlling depth of checks.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum VerificationLevel {
    /// Quick checks (RocksDB health, schema registry)
    Quick,

    /// Standard checks (schema validation, edge consistency)
    Standard,

    /// Deep checks (embedding load tests, index verification)
    Deep,
}

impl Default for VerificationLevel {
    fn default() -> Self {
        Self::Standard
    }
}

/// Report from verification operation.
///
/// Contains all issues found during verification.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct VerificationReport {
    /// Verification level used
    pub level: String,

    /// Number of entities checked
    pub entities_checked: u64,

    /// Number of edges checked
    pub edges_checked: u64,

    /// Number of embeddings checked
    pub embeddings_checked: u64,

    /// Issues found during verification
    pub issues: Vec<VerificationIssue>,

    /// Time taken (milliseconds)
    pub duration_ms: u64,
}

impl VerificationReport {
    /// Check if database is healthy.
    ///
    /// # Returns
    ///
    /// True if no issues found
    pub fn is_healthy(&self) -> bool {
        self.issues.is_empty()
    }

    /// Get count of critical issues.
    ///
    /// # Returns
    ///
    /// Number of critical severity issues
    pub fn critical_count(&self) -> usize {
        self.issues
            .iter()
            .filter(|i| matches!(i.severity, IssueSeverity::Critical))
            .count()
    }

    /// Get count of warning issues.
    ///
    /// # Returns
    ///
    /// Number of warning severity issues
    pub fn warning_count(&self) -> usize {
        self.issues
            .iter()
            .filter(|i| matches!(i.severity, IssueSeverity::Warning))
            .count()
    }
}

/// Issue found during verification.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct VerificationIssue {
    /// Issue severity
    pub severity: IssueSeverity,

    /// Issue category
    pub category: IssueCategory,

    /// Human-readable description
    pub description: String,

    /// Affected entity ID (if applicable)
    pub entity_id: Option<String>,

    /// Suggested fix (if known)
    pub suggested_fix: Option<String>,
}

/// Severity level of verification issue.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum IssueSeverity {
    /// Critical issue (data corruption, referential integrity violation)
    Critical,

    /// Warning issue (orphaned data, index mismatch)
    Warning,

    /// Info (performance issue, optimization opportunity)
    Info,
}

/// Category of verification issue.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum IssueCategory {
    /// Schema validation failure
    Schema,

    /// Edge consistency issue
    Edge,

    /// Embedding problem
    Embedding,

    /// Index inconsistency
    Index,

    /// RocksDB corruption
    Corruption,

    /// Other issue
    Other,
}

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

    #[test]
    fn test_verification_report_healthy() {
        let report = VerificationReport {
            level: "standard".to_string(),
            entities_checked: 1000,
            edges_checked: 2000,
            embeddings_checked: 800,
            issues: vec![],
            duration_ms: 5000,
        };

        assert!(report.is_healthy());
        assert_eq!(report.critical_count(), 0);
        assert_eq!(report.warning_count(), 0);
    }

    #[tokio::test]
    async fn test_verify_database() {
        // TODO: Test verification with temp database
        todo!("Implement after verify_database() is implemented")
    }
}
