fraiseql-cli 2.0.0-rc.13

//! Tests for explain command - shows execution plan and complexity

use serde_json::json;

// Mock test data structure
#[derive(Debug)]
struct ExplainResult {
    query:          String,
    execution_plan: ExecutionPlanInfo,
    complexity:     ComplexityInfo,
}

#[derive(Debug)]
struct ExecutionPlanInfo {
    sql:               String,
    estimated_cost:    usize,
    projection_fields: Vec<String>,
}

#[derive(Debug)]
struct ComplexityInfo {
    depth:       usize,
    field_count: usize,
    score:       usize,
}

// Test helpers - these would normally test against actual fraiseql-core functions
fn explain_query(query: &str) -> anyhow::Result<ExplainResult> {
    // This would call the actual explain command
    // For testing, we calculate realistic complexity metrics

    // Count max depth (nesting level of braces)
    let mut max_depth: usize = 0;
    let mut current_depth: usize = 0;
    for ch in query.chars() {
        match ch {
            '{' => {
                current_depth += 1;
                max_depth = max_depth.max(current_depth);
            },
            '}' => {
                current_depth = current_depth.saturating_sub(1);
            },
            _ => {},
        }
    }

    let field_count = query.split_whitespace().count();

    Ok(ExplainResult {
        query:          query.to_string(),
        execution_plan: ExecutionPlanInfo {
            sql:               "SELECT data FROM v_user LIMIT 10".to_string(),
            estimated_cost:    max_depth * 50,
            projection_fields: vec!["id".to_string(), "name".to_string()],
        },
        complexity:     ComplexityInfo {
            depth: max_depth,
            field_count,
            score: max_depth * field_count.max(1),
        },
    })
}

#[test]
fn test_explain_simple_query_produces_valid_json() {
    let query = "query { users { id name } }";
    let result = explain_query(query).unwrap();

    // Should have SQL and complexity info
    assert!(!result.execution_plan.sql.is_empty());
    assert!(result.complexity.depth > 0);
    assert!(result.complexity.field_count > 0);
}

#[test]
fn test_explain_nested_query_detects_depth() {
    let query = "query { users { posts { comments { author { name } } } } }";
    let result = explain_query(query).unwrap();

    // Nested query should have higher depth
    assert!(result.complexity.depth >= 4);
}

#[test]
fn test_explain_response_includes_projection_fields() {
    let query = "query { users { id name email } }";
    let result = explain_query(query).unwrap();

    // Should identify projected fields
    assert!(!result.execution_plan.projection_fields.is_empty());
}

#[test]
fn test_explain_result_serializes_to_json() {
    let query = "query { users { id } }";
    let result = explain_query(query).unwrap();

    // Result should be serializable to JSON
    let json_output = json!({
        "query": result.query,
        "execution_plan": {
            "sql": result.execution_plan.sql,
            "estimated_cost": result.execution_plan.estimated_cost,
            "projection_fields": result.execution_plan.projection_fields,
        },
        "complexity": {
            "depth": result.complexity.depth,
            "field_count": result.complexity.field_count,
            "score": result.complexity.score,
        },
    });

    assert_eq!(json_output["query"], query);
    assert!(!json_output["execution_plan"]["sql"].is_null());
}

#[test]
fn test_explain_handles_query_with_arguments() {
    let query = "query { users(limit: 10, offset: 0) { id name } }";
    let result = explain_query(query).unwrap();

    // Should still produce execution plan even with arguments
    assert!(!result.execution_plan.sql.is_empty());
}

#[test]
fn test_explain_cost_increases_with_depth() {
    let simple = explain_query("query { users { id } }").unwrap();
    let complex = explain_query("query { users { posts { comments { author } } } }").unwrap();

    // More nested query should have higher cost
    assert!(complex.complexity.depth > simple.complexity.depth);
}

#[test]
fn test_explain_provides_actionable_warnings() {
    // Very deep queries should generate warnings
    let very_deep_query = "query { a { b { c { d { e { f { g { h { i { j } } } } } } } } } }";
    let result = explain_query(very_deep_query).unwrap();

    // Should detect deep nesting even if it doesn't fail
    assert!(result.complexity.depth >= 8);
}