//! Temporal Query Support: As-Of-Date Queries
//!
//! Query memory state at a specific point in time.
//! Essential for reconstructing historical knowledge state (Zep alignment).
//!
//! CRAP: 12 (Temporal filtering logic)
//! SOLID: Single responsibility (temporal queries)
//! DRY: Reuses query types from mem_core

use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};
use tracing::{debug, info};

/// Temporal query configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TemporalQueryConfig {
    pub enabled: bool,
    pub allow_future_dates: bool,         // Allow querying past future dates
    pub default_to_now: bool,             // If no time specified, use NOW()
    pub max_lookback_days: Option<i64>,   // Limit how far back to query
}

impl Default for TemporalQueryConfig {
    fn default() -> Self {
        Self {
            enabled: true,
            allow_future_dates: false,
            default_to_now: true,
            max_lookback_days: Some(365 * 5),  // 5 years
        }
    }
}

/// Temporal query specification
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TemporalQuery {
    /// Base query text
    pub query: String,
    /// Point in time to query at
    pub as_of_time: DateTime<Utc>,
    /// Optional: time range for temporal search
    pub time_range: Option<(DateTime<Utc>, DateTime<Utc>)>,
}

/// Temporal query result
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TemporalQueryResult {
    pub query: String,
    pub as_of_time: DateTime<Utc>,
    pub num_facts: usize,
    pub valid_facts: usize,     // Facts valid at as_of_time
    pub invalid_facts: usize,   // Facts invalid at as_of_time
    pub note: String,
}

/// Temporal filter for edges
#[derive(Debug, Clone)]
pub struct TemporalFilter {
    config: TemporalQueryConfig,
}

impl TemporalFilter {
    pub fn new(config: TemporalQueryConfig) -> Self {
        Self { config }
    }

    /// Validate query time
    pub fn validate_query_time(&self, time: DateTime<Utc>) -> Result<(), String> {
        if !self.config.enabled {
            return Ok(());
        }

        let now = Utc::now();

        // Check if querying future
        if !self.config.allow_future_dates && time > now {
            return Err(format!(
                "Cannot query future time: {} (now: {})",
                time, now
            ));
        }

        // Check lookback limit
        if let Some(max_days) = self.config.max_lookback_days {
            let cutoff = now - chrono::Duration::days(max_days);
            if time < cutoff {
                return Err(format!(
                    "Query time {} exceeds max lookback of {} days",
                    time, max_days
                ));
            }
        }

        Ok(())
    }

    /// Check if edge is valid at point in time
    /// Returns: (is_valid_at_time, is_expired_at_time)
    pub fn is_edge_valid_at_time(
        &self,
        t_valid: Option<DateTime<Utc>>,
        t_invalid: Option<DateTime<Utc>>,
        query_time: DateTime<Utc>,
    ) -> (bool, bool) {
        if !self.config.enabled {
            return (true, false);
        }

        // Edge is valid if:
        // - t_valid is None or <= query_time (became true at/before query time)
        // - t_invalid is None or > query_time (didn't become false before query time)
        let is_valid = (t_valid.is_none() || t_valid.unwrap() <= query_time)
            && (t_invalid.is_none() || t_invalid.unwrap() > query_time);

        let is_expired = t_invalid.is_some() && t_invalid.unwrap() <= query_time;

        (is_valid, is_expired)
    }

    /// Get SQL WHERE clause for temporal filtering
    pub fn sql_where_clause(
        &self,
        query_time: DateTime<Utc>,
        table_prefix: &str,
    ) -> String {
        if !self.config.enabled {
            return format!("{}.t_expired IS NULL", table_prefix);
        }

        format!(
            "({p}.t_valid IS NULL OR {p}.t_valid <= '{time}') AND \
             ({p}.t_invalid IS NULL OR {p}.t_invalid > '{time}') AND \
             {p}.t_expired IS NULL",
            p = table_prefix,
            time = query_time.to_rfc3339()
        )
    }
}

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

    #[test]
    fn test_temporal_config_defaults() {
        let config = TemporalQueryConfig::default();
        assert!(config.enabled);
        assert!(!config.allow_future_dates);
        assert!(config.default_to_now);
        assert_eq!(config.max_lookback_days, Some(365 * 5));
    }

    #[test]
    fn test_validate_query_time_now() {
        let config = TemporalQueryConfig::default();
        let filter = TemporalFilter::new(config);
        
        let now = Utc::now();
        assert!(filter.validate_query_time(now).is_ok());
    }

    #[test]
    fn test_validate_query_time_past() {
        let config = TemporalQueryConfig::default();
        let filter = TemporalFilter::new(config);
        
        let past = Utc::now() - chrono::Duration::days(30);
        assert!(filter.validate_query_time(past).is_ok());
    }

    #[test]
    fn test_validate_query_time_future_disallowed() {
        let config = TemporalQueryConfig {
            allow_future_dates: false,
            ..Default::default()
        };
        let filter = TemporalFilter::new(config);
        
        let future = Utc::now() + chrono::Duration::days(30);
        assert!(filter.validate_query_time(future).is_err());
    }

    #[test]
    fn test_validate_query_time_future_allowed() {
        let config = TemporalQueryConfig {
            allow_future_dates: true,
            ..Default::default()
        };
        let filter = TemporalFilter::new(config);
        
        let future = Utc::now() + chrono::Duration::days(30);
        assert!(filter.validate_query_time(future).is_ok());
    }

    #[test]
    fn test_is_edge_valid_at_time_current() {
        let config = TemporalQueryConfig::default();
        let filter = TemporalFilter::new(config);
        
        let now = Utc::now();
        let past = now - chrono::Duration::days(10);
        
        // Edge valid from past, still active
        let (is_valid, is_expired) = filter.is_edge_valid_at_time(Some(past), None, now);
        assert!(is_valid);
        assert!(!is_expired);
    }

    #[test]
    fn test_is_edge_valid_at_time_expired() {
        let config = TemporalQueryConfig::default();
        let filter = TemporalFilter::new(config);
        
        let now = Utc::now();
        let past = now - chrono::Duration::days(10);
        let future = now + chrono::Duration::days(10);
        
        // Edge valid from past, became invalid before now
        let (is_valid, is_expired) = filter.is_edge_valid_at_time(Some(past), Some(now - chrono::Duration::days(1)), now);
        assert!(!is_valid);
        assert!(is_expired);
    }

    #[test]
    fn test_is_edge_valid_at_time_historical() {
        let config = TemporalQueryConfig::default();
        let filter = TemporalFilter::new(config);
        
        let now = Utc::now();
        let past_30 = now - chrono::Duration::days(30);
        let past_10 = now - chrono::Duration::days(10);
        let past_5 = now - chrono::Duration::days(5);
        
        // Query at 30 days ago: edge didn't exist yet
        let (is_valid, _) = filter.is_edge_valid_at_time(Some(past_10), Some(past_5), past_30);
        assert!(!is_valid);
        
        // Query at 8 days ago: edge was valid
        let (is_valid, _) = filter.is_edge_valid_at_time(Some(past_10), Some(past_5), now - chrono::Duration::days(8));
        assert!(is_valid);
    }

    #[test]
    fn test_sql_where_clause() {
        let config = TemporalQueryConfig::default();
        let filter = TemporalFilter::new(config);
        
        let now = Utc::now();
        let clause = filter.sql_where_clause(now, "e");
        
        assert!(clause.contains("e.t_valid IS NULL OR e.t_valid <="));
        assert!(clause.contains("e.t_invalid IS NULL OR e.t_invalid >"));
        assert!(clause.contains("e.t_expired IS NULL"));
    }

    #[test]
    fn test_sql_where_clause_disabled() {
        let config = TemporalQueryConfig {
            enabled: false,
            ..Default::default()
        };
        let filter = TemporalFilter::new(config);
        
        let now = Utc::now();
        let clause = filter.sql_where_clause(now, "e");
        
        // When disabled, only check t_expired
        assert_eq!(clause, "e.t_expired IS NULL");
    }
}