//! Usage rollup DAO
//!
//! Aggregates proxy_request_logs into daily rollups and prunes old detail rows.

use crate::database::{lock_conn, Database};
use crate::error::AppError;

impl Database {
    /// Aggregate proxy_request_logs older than `retain_days` into usage_daily_rollups,
    /// then delete the aggregated detail rows.
    /// Returns the number of deleted detail rows.
    pub fn rollup_and_prune(&self, retain_days: i64) -> Result<u64, AppError> {
        let cutoff = chrono::Utc::now().timestamp() - retain_days * 86400;
        let conn = lock_conn!(self.conn);

        // Check if there are any rows to process
        let count: i64 = conn
            .query_row(
                "SELECT COUNT(*) FROM proxy_request_logs WHERE created_at < ?1",
                [cutoff],
                |row| row.get(0),
            )
            .map_err(|e| AppError::Database(e.to_string()))?;

        if count == 0 {
            return Ok(0);
        }

        // Use a savepoint for atomicity
        conn.execute("SAVEPOINT rollup_prune;", [])
            .map_err(|e| AppError::Database(e.to_string()))?;

        let result = Self::do_rollup_and_prune(&conn, cutoff);

        match result {
            Ok(deleted) => {
                conn.execute("RELEASE rollup_prune;", [])
                    .map_err(|e| AppError::Database(e.to_string()))?;
                if deleted > 0 {
                    log::info!(
                        "Rolled up and pruned {deleted} proxy_request_logs (retain={retain_days}d)"
                    );
                }
                Ok(deleted)
            }
            Err(e) => {
                conn.execute("ROLLBACK TO rollup_prune;", []).ok();
                conn.execute("RELEASE rollup_prune;", []).ok();
                Err(e)
            }
        }
    }

    fn do_rollup_and_prune(conn: &rusqlite::Connection, cutoff: i64) -> Result<u64, AppError> {
        // Aggregate old logs, merging with any pre-existing rollup rows via LEFT JOIN.
        conn.execute(
            "INSERT OR REPLACE INTO usage_daily_rollups
                (date, app_type, provider_id, model,
                 request_count, success_count,
                 input_tokens, output_tokens,
                 cache_read_tokens, cache_creation_tokens,
                 total_cost_usd, avg_latency_ms)
            SELECT
                d, a, p, m,
                COALESCE(old.request_count, 0) + new_req,
                COALESCE(old.success_count, 0) + new_succ,
                COALESCE(old.input_tokens, 0) + new_in,
                COALESCE(old.output_tokens, 0) + new_out,
                COALESCE(old.cache_read_tokens, 0) + new_cr,
                COALESCE(old.cache_creation_tokens, 0) + new_cc,
                CAST(COALESCE(CAST(old.total_cost_usd AS REAL), 0) + new_cost AS TEXT),
                CASE WHEN COALESCE(old.request_count, 0) + new_req > 0
                    THEN (COALESCE(old.avg_latency_ms, 0) * COALESCE(old.request_count, 0)
                          + new_lat * new_req)
                         / (COALESCE(old.request_count, 0) + new_req)
                    ELSE 0 END
            FROM (
                SELECT
                    date(created_at, 'unixepoch', 'localtime') as d,
                    app_type as a, provider_id as p, model as m,
                    COUNT(*) as new_req,
                    SUM(CASE WHEN status_code >= 200 AND status_code < 300 THEN 1 ELSE 0 END) as new_succ,
                    COALESCE(SUM(input_tokens), 0) as new_in,
                    COALESCE(SUM(output_tokens), 0) as new_out,
                    COALESCE(SUM(cache_read_tokens), 0) as new_cr,
                    COALESCE(SUM(cache_creation_tokens), 0) as new_cc,
                    COALESCE(SUM(CAST(total_cost_usd AS REAL)), 0) as new_cost,
                    COALESCE(AVG(latency_ms), 0) as new_lat
                FROM proxy_request_logs WHERE created_at < ?1
                GROUP BY d, a, p, m
            ) agg
            LEFT JOIN usage_daily_rollups old
                ON old.date = agg.d AND old.app_type = agg.a
                AND old.provider_id = agg.p AND old.model = agg.m",
            [cutoff],
        )
        .map_err(|e| AppError::Database(format!("Rollup aggregation failed: {e}")))?;

        // Delete the aggregated detail rows
        let deleted = conn
            .execute(
                "DELETE FROM proxy_request_logs WHERE created_at < ?1",
                [cutoff],
            )
            .map_err(|e| AppError::Database(format!("Pruning old logs failed: {e}")))?;

        Ok(deleted as u64)
    }
}

#[cfg(test)]
mod tests {
    use crate::database::Database;
    use crate::error::AppError;

    #[test]
    fn test_rollup_and_prune() -> Result<(), AppError> {
        let db = Database::memory()?;
        let now = chrono::Utc::now().timestamp();
        let old_ts = now - 40 * 86400; // 40 days ago
        let recent_ts = now - 5 * 86400; // 5 days ago

        {
            let conn = crate::database::lock_conn!(db.conn);
            for i in 0..5 {
                conn.execute(
                    "INSERT INTO proxy_request_logs (
                        request_id, provider_id, app_type, model,
                        input_tokens, output_tokens, total_cost_usd,
                        latency_ms, status_code, created_at
                    ) VALUES (?1, 'p1', 'claude', 'claude-3', 100, 50, '0.01', 100, 200, ?2)",
                    rusqlite::params![format!("old-{i}"), old_ts + i as i64],
                )?;
            }
            for i in 0..3 {
                conn.execute(
                    "INSERT INTO proxy_request_logs (
                        request_id, provider_id, app_type, model,
                        input_tokens, output_tokens, total_cost_usd,
                        latency_ms, status_code, created_at
                    ) VALUES (?1, 'p1', 'claude', 'claude-3', 200, 100, '0.02', 150, 200, ?2)",
                    rusqlite::params![format!("recent-{i}"), recent_ts + i as i64],
                )?;
            }
        }

        let deleted = db.rollup_and_prune(30)?;
        assert_eq!(deleted, 5);

        // Verify rollup data
        let conn = crate::database::lock_conn!(db.conn);
        let count: i64 = conn.query_row(
            "SELECT request_count FROM usage_daily_rollups WHERE app_type = 'claude'",
            [],
            |row| row.get(0),
        )?;
        assert_eq!(count, 5);

        // Verify recent logs untouched
        let remaining: i64 =
            conn.query_row("SELECT COUNT(*) FROM proxy_request_logs", [], |row| {
                row.get(0)
            })?;
        assert_eq!(remaining, 3);
        Ok(())
    }

    #[test]
    fn test_rollup_noop_when_no_old_data() -> Result<(), AppError> {
        let db = Database::memory()?;
        assert_eq!(db.rollup_and_prune(30)?, 0);
        Ok(())
    }

    #[test]
    fn test_rollup_merges_with_existing() -> Result<(), AppError> {
        let db = Database::memory()?;
        let now = chrono::Utc::now().timestamp();
        let old_ts = now - 40 * 86400;

        {
            let conn = crate::database::lock_conn!(db.conn);
            let date_str = chrono::DateTime::from_timestamp(old_ts, 0)
                .unwrap()
                .format("%Y-%m-%d")
                .to_string();
            conn.execute(
                "INSERT INTO usage_daily_rollups
                    (date, app_type, provider_id, model, request_count, success_count,
                     input_tokens, output_tokens, total_cost_usd, avg_latency_ms)
                 VALUES (?1, 'claude', 'p1', 'claude-3', 10, 10, 1000, 500, '0.10', 100)",
                [&date_str],
            )?;
            for i in 0..3 {
                conn.execute(
                    "INSERT INTO proxy_request_logs (
                        request_id, provider_id, app_type, model,
                        input_tokens, output_tokens, total_cost_usd,
                        latency_ms, status_code, created_at
                    ) VALUES (?1, 'p1', 'claude', 'claude-3', 100, 50, '0.01', 200, 200, ?2)",
                    rusqlite::params![format!("merge-{i}"), old_ts + i as i64],
                )?;
            }
        }

        let deleted = db.rollup_and_prune(30)?;
        assert_eq!(deleted, 3);

        let conn = crate::database::lock_conn!(db.conn);
        let (count, input): (i64, i64) = conn.query_row(
            "SELECT request_count, input_tokens FROM usage_daily_rollups
             WHERE app_type = 'claude' AND provider_id = 'p1'",
            [],
            |row| Ok((row.get(0)?, row.get(1)?)),
        )?;
        assert_eq!(count, 13, "10 existing + 3 new");
        assert_eq!(input, 1300, "1000 existing + 300 new");
        Ok(())
    }
}