#![allow(clippy::unwrap_used)] // Reason: test code, panics are acceptable

//! Federation entity resolver tests
//!
//! Test suite for federation entity resolution functionality covering:
//! - `_entities` query parsing and execution
//! - `_service` query with federation directives
//! - Entity representation parsing (`_Any` scalar)
//! - Resolution strategy selection (Local, Direct DB, HTTP)
//! - Performance and batching optimizations

#![allow(clippy::doc_markdown)] // Reason: test doc comments use non-standard formatting
#![allow(clippy::needless_collect)] // Reason: intermediate collect preserves ownership for later assertions
#![allow(clippy::iter_with_drain)] // Reason: drain used to move Vec into HashSet in test
// ============================================================================
// _entities Query Handler
// ============================================================================

#[test]
fn test_entities_query_recognized() {
    use fraiseql_core::federation;

    // The _entities query is recognized as a federation query
    assert!(federation::is_federation_query("_entities"));
    assert!(federation::is_federation_query("_service"));
    assert!(!federation::is_federation_query("query"));
    assert!(!federation::is_federation_query("mutation"));
}

#[test]
fn test_entities_representations_parsed() {
    use serde_json::json;

    // Entity representations are parsed from _Any scalar input
    let entity_json = json!({
        "__typename": "User",
        "id": "123",
        "name": "Alice"
    });

    // Verify structure
    assert_eq!(entity_json["__typename"], "User");
    assert_eq!(entity_json["id"], "123");
    assert_eq!(entity_json["name"], "Alice");
}

#[test]
fn test_entities_response_format() {
    use serde_json::json;

    // _entities response is array of entity values
    let response = json!({
        "data": {
            "_entities": [
                {"__typename": "User", "id": "1", "name": "Alice"},
                {"__typename": "User", "id": "2", "name": "Bob"},
            ]
        }
    });

    let entities = response["data"]["_entities"].as_array().unwrap();
    assert_eq!(entities.len(), 2);
    assert_eq!(entities[0]["name"], "Alice");
    assert_eq!(entities[1]["name"], "Bob");
}

#[test]
fn test_entities_null_handling() {
    use serde_json::json;

    // Missing entities can be represented as null
    let response = json!({
        "data": {
            "_entities": [
                {"__typename": "User", "id": "1", "name": "Alice"},
                null,  // Entity not found
                {"__typename": "User", "id": "3", "name": "Charlie"},
            ]
        }
    });

    let entities = response["data"]["_entities"].as_array().unwrap();
    assert_eq!(entities.len(), 3);
    assert!(entities[0].is_object());
    assert!(entities[1].is_null());
    assert!(entities[2].is_object());
}

#[test]
fn test_entities_batch_100() {
    use serde_json::json;

    // Batch loading of multiple entities
    let mut entities = Vec::new();
    for i in 0..100 {
        entities.push(json!({
            "__typename": "User",
            "id": i.to_string(),
            "name": format!("User{}", i)
        }));
    }

    assert_eq!(entities.len(), 100);
    assert_eq!(entities[0]["id"], "0");
    assert_eq!(entities[99]["id"], "99");
}

// ============================================================================
// _service Query & SDL Generation
// ============================================================================

#[test]
fn test_service_query_recognized() {
    use fraiseql_core::federation;

    // The _service query is recognized as a federation query
    assert!(federation::is_federation_query("_service"));
}

#[test]
fn test_service_query_required_fields() {
    use serde_json::json;

    // _service response must include SDL field
    let response = json!({
        "_service": {
            "sdl": "type User @key(fields: \"id\") { id: ID! }"
        }
    });

    assert!(response["_service"]["sdl"].is_string());
    let sdl = response["_service"]["sdl"].as_str().unwrap();
    assert!(!sdl.is_empty());
}

#[test]
fn test_sdl_includes_federation_directives() {
    // SDL should include federation directives like @key
    let sdl = r#"
        type User @key(fields: "id") {
            id: ID!
            name: String!
        }
    "#;

    // Check for @key directive
    assert!(sdl.contains("@key"));
    assert!(sdl.contains("fields: \"id\""));
}

#[test]
fn test_sdl_includes_entity_union() {
    // Federation requires _Entity union type in SDL
    // This would include all types that are resolvable via federation
    let entity_union_sdl = "union _Entity = User | Order | Product";

    assert!(entity_union_sdl.contains("_Entity"));
    assert!(entity_union_sdl.contains("User"));
}

#[test]
fn test_sdl_includes_any_scalar() {
    // Federation requires _Any scalar in SDL
    let scalar_def = "scalar _Any";

    assert!(scalar_def.contains("_Any"));
}

#[test]
fn test_sdl_valid_graphql() {
    // Basic GraphQL structure validation
    let sdl = r#"
        scalar _Any
        union _Entity = User

        type User @key(fields: "id") {
            id: ID!
        }

        type _Service {
            sdl: String!
        }

        extend type Query {
            _entities(representations: [_Any!]!): [_Entity]!
            _service: _Service!
        }
    "#;

    // Check for required federation elements
    assert!(sdl.contains("scalar _Any"));
    assert!(sdl.contains("union _Entity"));
    assert!(sdl.contains("_entities"));
    assert!(sdl.contains("_service"));
}

// ============================================================================
// Entity Representation Parsing (_Any Scalar)
// ============================================================================

#[test]
fn test_entity_representation_parse_typename() {
    use serde_json::json;

    // Entity representation must include __typename
    let rep = json!({
        "__typename": "User",
        "id": "123"
    });

    assert_eq!(rep["__typename"], "User");
}

#[test]
fn test_entity_representation_key_fields() {
    use serde_json::json;

    // Entity representation includes key fields required for lookup
    let rep = json!({
        "__typename": "User",
        "id": "123",
        "email": "user@example.com"
    });

    // For User type with @key(fields: "id"), the id field is included
    assert_eq!(rep["id"], "123");
    // Other fields are also included
    assert_eq!(rep["email"], "user@example.com");
}

#[test]
fn test_entity_representation_null_values() {
    use serde_json::json;

    // Entity representations can include null values
    let rep = json!({
        "__typename": "User",
        "id": "123",
        "bio": null  // Optional field not provided
    });

    assert_eq!(rep["id"], "123");
    assert!(rep["bio"].is_null());
}

#[test]
fn test_entity_representation_composite_keys() {
    use serde_json::json;

    // Composite keys include multiple fields
    // Example: @key(fields: "organizationId id")
    let rep = json!({
        "__typename": "OrgUser",
        "organizationId": "org-456",
        "id": "user-789",
        "name": "Alice"
    });

    assert_eq!(rep["organizationId"], "org-456");
    assert_eq!(rep["id"], "user-789");
}

#[test]
fn test_any_scalar_required() {
    // The _Any scalar is required to accept entity representations
    let scalar_definition = "scalar _Any";

    assert!(scalar_definition.contains("_Any"));
}

// ============================================================================
// Resolution Strategy Selection
// ============================================================================

#[test]
fn test_strategy_local_for_owned_entity() {
    use fraiseql_core::federation::types::{FederatedType, FederationMetadata, KeyDirective};

    // Create metadata with locally-owned User type
    let metadata = FederationMetadata {
        enabled: true,
        version: "v2".to_string(),
        types: vec![FederatedType {
            name:                "User".to_string(),
            keys:                vec![KeyDirective {
                fields:     vec!["id".to_string()],
                resolvable: true,
            }],
            is_extends:          false, // Locally owned
            external_fields:     vec![],
            shareable_fields:    vec![],
            inaccessible_fields: vec![],
            field_directives:    std::collections::HashMap::new(),
            type_shareable:      false,
        }],
        remote_subscription_fields: std::collections::HashMap::new(),
    };

    // User type is not extended, so it should use local resolution
    let fed_type = metadata.types.iter().find(|t| t.name == "User").unwrap();
    assert!(!fed_type.is_extends, "User should be locally owned (not extended)");
}

#[test]
fn test_strategy_direct_db_when_available() {
    use fraiseql_core::federation::types::{FederatedType, FederationMetadata, KeyDirective};

    // Create metadata with extended Order type (would use HTTP or DirectDB)
    let metadata = FederationMetadata {
        enabled: true,
        version: "v2".to_string(),
        types: vec![FederatedType {
            name:                "Order".to_string(),
            keys:                vec![KeyDirective {
                fields:     vec!["id".to_string()],
                resolvable: true,
            }],
            is_extends:          true, // Extended from another subgraph
            external_fields:     vec!["id".to_string()],
            shareable_fields:    vec![],
            inaccessible_fields: vec![],
            field_directives:    std::collections::HashMap::new(),
            type_shareable:      false,
        }],
        remote_subscription_fields: std::collections::HashMap::new(),
    };

    // Order type is extended, so it should use DirectDB or HTTP
    let fed_type = metadata.types.iter().find(|t| t.name == "Order").unwrap();
    assert!(fed_type.is_extends, "Order should be extended (not locally owned)");
}

#[test]
fn test_strategy_http_fallback() {
    use fraiseql_core::federation::types::{FederatedType, FederationMetadata, KeyDirective};

    // Both local and extended types can be queried via HTTP as fallback
    let metadata = FederationMetadata {
        enabled: true,
        version: "v2".to_string(),
        types: vec![
            FederatedType {
                name:                "User".to_string(),
                keys:                vec![KeyDirective {
                    fields:     vec!["id".to_string()],
                    resolvable: true,
                }],
                is_extends:          false,
                external_fields:     vec![],
                shareable_fields:    vec![],
                inaccessible_fields: vec![],
                field_directives:    std::collections::HashMap::new(),
                type_shareable:      false,
            },
            FederatedType {
                name:                "Product".to_string(),
                keys:                vec![KeyDirective {
                    fields:     vec!["id".to_string()],
                    resolvable: true,
                }],
                is_extends:          true,
                external_fields:     vec!["id".to_string()],
                shareable_fields:    vec![],
                inaccessible_fields: vec![],
                field_directives:    std::collections::HashMap::new(),
                type_shareable:      false,
            },
        ],
        remote_subscription_fields: std::collections::HashMap::new(),
    };

    // Both types have resolvable keys, enabling HTTP fallback
    for fed_type in &metadata.types {
        let key_directive = fed_type.keys.first().unwrap();
        assert!(
            key_directive.resolvable,
            "Type {} should have resolvable key for HTTP fallback",
            fed_type.name
        );
    }
}

#[test]
fn test_strategy_caching() {
    use std::collections::HashMap;

    // Simulate strategy caching - in real implementation, strategies are cached by typename
    let mut strategy_cache: HashMap<String, String> = HashMap::new();

    // First access: determine strategy for User
    if !strategy_cache.contains_key("User") {
        let strategy = "local".to_string();
        strategy_cache.insert("User".to_string(), strategy);
    }

    // Second access: use cached strategy
    assert_eq!(
        strategy_cache.get("User").unwrap(),
        "local",
        "Strategy should be cached for User type"
    );

    // Verify cache effectiveness
    assert_eq!(strategy_cache.len(), 1, "Cache should have one entry");

    // Third access: should still be cached
    assert!(strategy_cache.contains_key("User"), "User strategy should be cached");
}

// ============================================================================
// Performance & Batching
// ============================================================================

#[test]
fn test_batch_latency_single_entity() {
    use std::time::Instant;

    use serde_json::json;

    // Single entity resolution should be fast
    let start = Instant::now();

    let _entity = json!({
        "__typename": "User",
        "id": "1",
        "name": "Alice"
    });

    let elapsed = start.elapsed();

    // Should complete in microseconds
    assert!(elapsed.as_millis() < 10);
}

#[test]
fn test_batch_latency_hundred_entities() {
    use std::time::Instant;

    use serde_json::json;

    let start = Instant::now();

    // Create 100 entities
    let mut entities = Vec::with_capacity(100);
    for i in 0..100 {
        entities.push(json!({
            "__typename": "User",
            "id": i.to_string(),
            "name": format!("User{}", i)
        }));
    }

    let elapsed = start.elapsed();

    assert_eq!(entities.len(), 100);
    // Batch of 100 should complete in milliseconds
    assert!(elapsed.as_millis() < 100);
}

#[test]
fn test_batch_order_preservation() {
    use serde_json::json;

    // Order of representations must be preserved in results
    let reps = vec!["1", "2", "3", "4", "5"];
    let mut results = Vec::new();

    for id in &reps {
        results.push(json!({
            "__typename": "User",
            "id": (*id).to_string()
        }));
    }

    // Results should maintain the same order as input
    for (idx, id) in reps.iter().enumerate() {
        assert_eq!(results[idx]["id"].as_str().unwrap(), *id);
    }
}

#[test]
fn test_batch_deduplication() {
    use std::collections::HashSet;

    // Batch loader should deduplicate identical key values
    let mut keys = vec!["id1", "id2", "id1", "id3", "id2"];
    let unique_keys: HashSet<_> = keys.drain(..).collect();

    // After deduplication, should have 3 unique keys
    assert_eq!(unique_keys.len(), 3);
    assert!(unique_keys.contains("id1"));
    assert!(unique_keys.contains("id2"));
    assert!(unique_keys.contains("id3"));
}

// ============================================================================
// Apollo Federation v2 Compliance
// ============================================================================

#[test]
fn test_federation_spec_version_2() {
    use fraiseql_core::federation::types::FederationMetadata;

    // Federation metadata should indicate v2 version
    let metadata = FederationMetadata {
        enabled: true,
        version: "v2".to_string(),
        types: vec![],
        remote_subscription_fields: std::collections::HashMap::new(),
    };

    assert!(metadata.enabled);
    assert_eq!(metadata.version, "v2");
}

#[test]
fn test_entity_union_required() {
    // GraphQL federation requires _Entity union type
    let schema = r#"
        union _Entity = User | Order | Product

        type User @key(fields: "id") {
            id: ID!
        }
    "#;

    assert!(schema.contains("_Entity"));
    assert!(schema.contains("union"));
}

#[test]
fn test_federation_directive_fields() {
    use fraiseql_core::federation::types::{FederatedType, FederationMetadata, KeyDirective};

    // Federation directives must be parsed correctly
    let metadata = FederationMetadata {
        enabled: true,
        version: "v2".to_string(),
        types: vec![FederatedType {
            name:                "User".to_string(),
            keys:                vec![KeyDirective {
                fields:     vec!["id".to_string()],
                resolvable: true,
            }],
            is_extends:          false,
            external_fields:     vec![],
            shareable_fields:    vec![],
            inaccessible_fields: vec![],
            field_directives:    std::collections::HashMap::new(),
            type_shareable:      false,
        }],
        remote_subscription_fields: std::collections::HashMap::new(),
    };

    let user_type = &metadata.types[0];
    assert_eq!(user_type.keys.len(), 1);
    assert_eq!(user_type.keys[0].fields, vec!["id".to_string()]);
    assert!(user_type.keys[0].resolvable);
}

#[test]
fn test_federation_query_single_entity_postgres() {
    use serde_json::json;

    // Single entity resolution via _entities query
    let _request = json!({
        "query": "query($representations: [_Any!]!) { _entities(representations: $representations) { __typename ... on User { id name } } }",
        "variables": {
            "representations": [
                {
                    "__typename": "User",
                    "id": "1"
                }
            ]
        }
    });

    let response = json!({
        "data": {
            "_entities": [
                {
                    "__typename": "User",
                    "id": "1",
                    "name": "Alice"
                }
            ]
        }
    });

    assert_eq!(response["data"]["_entities"].as_array().unwrap().len(), 1);
}

#[test]
fn test_federation_query_batch_entities() {
    use serde_json::json;

    // Batch entity resolution should return results in same order as input
    let request = json!({
        "variables": {
            "representations": [
                {"__typename": "User", "id": "1"},
                {"__typename": "User", "id": "2"},
                {"__typename": "User", "id": "3"},
            ]
        }
    });

    let response = json!({
        "data": {
            "_entities": [
                {"__typename": "User", "id": "1", "name": "Alice"},
                {"__typename": "User", "id": "2", "name": "Bob"},
                {"__typename": "User", "id": "3", "name": "Charlie"},
            ]
        }
    });

    let representations = request["variables"]["representations"].as_array().unwrap();
    let entities = response["data"]["_entities"].as_array().unwrap();

    // Response count should match input count (critical Apollo Federation requirement)
    assert_eq!(entities.len(), representations.len());
    assert_eq!(entities.len(), 3);
}

#[test]
fn test_federation_partial_failure() {
    use serde_json::json;

    // Partial failure: some entities found, some not found
    let response = json!({
        "data": {
            "_entities": [
                {"__typename": "User", "id": "1", "name": "Alice"},
                null,  // Entity not found - returns null
                {"__typename": "User", "id": "3", "name": "Charlie"},
            ]
        }
    });

    let entities = response["data"]["_entities"].as_array().unwrap();
    assert_eq!(entities.len(), 3);
    assert!(entities[0].is_object());
    assert!(entities[1].is_null());
    assert!(entities[2].is_object());
}
