db-migrate 0.1.1

// This module is for future schema introspection and drift detection
// Currently contains placeholder implementations that can be extended

use crate::MigrationError;
use scylla::Session;
use serde::{Deserialize, Serialize};

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TableInfo {
    pub keyspace: String,
    pub table_name: String,
    pub columns: Vec<ColumnInfo>,
    pub primary_key: Vec<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ColumnInfo {
    pub name: String,
    pub data_type: String,
    pub kind: String, // partition_key, clustering, regular
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct IndexInfo {
    pub name: String,
    pub table_name: String,
    pub column_name: String,
    pub index_type: String,
}

pub struct SchemaIntrospector<'a> {
    session: &'a Session,
    keyspace: &'a str,
}

impl<'a> SchemaIntrospector<'a> {
    pub fn new(session: &'a Session, keyspace: &'a str) -> Self {
        Self { session, keyspace }
    }

    /// Get all tables in the current keyspace
    pub async fn get_tables(&self) -> Result<Vec<TableInfo>, MigrationError> {
        // This is a placeholder implementation
        // In a full implementation, you would query system.schema_columns
        // and system.schema_keyspaces to get the actual schema information

        let query = "SELECT table_name FROM system_schema.tables WHERE keyspace_name = ?";
        let rows = self.session.query(query, (self.keyspace,)).await?;

        let mut tables = Vec::new();
        for row in rows
            .rows_typed::<(String,)>()
            .map_err(|e| MigrationError::IntegrityError(e.to_string()))?
        {
            let (table_name,) = row.map_err(|e| MigrationError::IntegrityError(e.to_string()))?;

            // For now, just return basic table info
            // In a full implementation, you'd fetch column details
            tables.push(TableInfo {
                keyspace: self.keyspace.to_string(),
                table_name,
                columns: Vec::new(),     // TODO: Implement column introspection
                primary_key: Vec::new(), // TODO: Implement primary key detection
            });
        }

        Ok(tables)
    }

    /// Get all indexes in the current keyspace
    pub async fn get_indexes(&self) -> Result<Vec<IndexInfo>, MigrationError> {
        // Placeholder implementation
        // In a full implementation, you would query system.schema_columns
        // to find secondary indexes

        Ok(Vec::new()) // TODO: Implement index introspection
    }

    /// Compare current schema with expected schema
    pub async fn detect_schema_drift(
        &self,
        _expected_schema: &[TableInfo],
    ) -> Result<Vec<String>, MigrationError> {
        // Placeholder for schema drift detection
        // This would compare the current database schema with what's expected
        // based on the applied migrations

        Ok(Vec::new()) // TODO: Implement drift detection
    }
}

// Future features that could be implemented:
// - Full CQL schema parsing and comparison
// - Detection of manual schema changes outside of migrations
// - Schema validation against migration files
// - Automatic schema documentation generation
// - Schema export/import functionality