//! Apollo Federation v2 specification compliance tests
//!
//! Validates FraiseQL implementation against Apollo Federation v2 specification:
//! - Service SDL requirements
//! - Entity resolution interface (_entities query)
//! - Service metadata (_service query)
//! - Reference handling
//! - Composition rules

use fraiseql_core::{
    federation,
    federation::types::{FederatedType, FederationMetadata, KeyDirective},
};
use serde_json::json;

// ============================================================================
// Federation Query Recognition Tests
// ============================================================================

#[test]
fn test_federation_service_query_recognized() {
    // _service query must be recognized as federation query
    assert!(federation::is_federation_query("_service"));
}

#[test]
fn test_federation_entities_query_recognized() {
    // _entities query must be recognized as federation query
    assert!(federation::is_federation_query("_entities"));
}

#[test]
fn test_non_federation_queries_not_recognized() {
    // Regular queries should not be recognized as federation
    assert!(!federation::is_federation_query("user"));
    assert!(!federation::is_federation_query("users"));
    assert!(!federation::is_federation_query("query"));
    assert!(!federation::is_federation_query("mutation"));
}

// ============================================================================
// Service SDL Requirements Tests
// ============================================================================

#[test]
fn test_sdl_includes_federation_schema_imports() {
    // Federation SDL must include required imports/directives
    let sdl = r#"
        scalar _Any
        union _Entity = User | Order

        type _Service {
            sdl: String!
        }

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

    // Must include _Any scalar
    assert!(sdl.contains("scalar _Any"), "SDL must include _Any scalar");

    // Must include _Entity union
    assert!(sdl.contains("union _Entity"), "SDL must include _Entity union");

    // Must include _Service type
    assert!(sdl.contains("type _Service"), "SDL must include _Service type");

    // Must include _entities query
    assert!(sdl.contains("_entities"), "SDL must include _entities query");

    // Must include _service query
    assert!(sdl.contains("_service"), "SDL must include _service query");
}

#[test]
fn test_sdl_entity_union_includes_all_types() {
    // _Entity union must include all resolvable types
    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![],
                field_directives: std::collections::HashMap::new(),
            },
            FederatedType {
                name:             "Order".to_string(),
                keys:             vec![KeyDirective {
                    fields:     vec!["id".to_string()],
                    resolvable: true,
                }],
                is_extends:       false,
                external_fields:  vec![],
                shareable_fields: vec![],
                field_directives: std::collections::HashMap::new(),
            },
        ],
    };

    // Both types have resolvable keys, so both should be in _Entity union
    let user_type = &metadata.types[0];
    let order_type = &metadata.types[1];

    assert!(user_type.keys[0].resolvable);
    assert!(order_type.keys[0].resolvable);
}

#[test]
fn test_sdl_any_scalar_definition() {
    // _Any scalar must be defined to accept entity representations
    let scalar = "scalar _Any";

    // This is the standard federation scalar
    assert!(scalar.contains("_Any"));
}

#[test]
fn test_sdl_service_type_definition() {
    // _Service type must have sdl field
    let service_type = r#"
        type _Service {
            sdl: String!
        }
    "#;

    assert!(service_type.contains("type _Service"));
    assert!(service_type.contains("sdl: String!"));
}

// ============================================================================
// Entity Resolution Interface Tests
// ============================================================================

#[test]
fn test_entities_query_signature() {
    // _entities query must accept representations: [_Any!]!
    let query = "_entities(representations: [_Any!]!)";

    assert!(query.contains("_entities"));
    assert!(query.contains("representations"));
    assert!(query.contains("_Any!"));
    assert!(query.contains("[_Any!]!"), "representations must be non-null array");
}

#[test]
fn test_entities_query_returns_union() {
    // _entities query returns [_Entity]! (array of union type)
    let return_type = "[_Entity]!";

    assert!(return_type.contains("_Entity"));
    assert!(return_type.contains("["), "Must return array");
    assert!(return_type.contains("!"), "Must be non-null");
}

#[test]
fn test_entity_representation_includes_typename() {
    // Each entity representation must include __typename
    let representation = json!({
        "__typename": "User",
        "id": "123"
    });

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

#[test]
fn test_entity_representation_includes_key_fields() {
    // Entity representations must include all key fields
    let representation = json!({
        "__typename": "OrgUser",
        "organizationId": "org123",
        "userId": "user456"
    });

    assert_eq!(representation["organizationId"], "org123");
    assert_eq!(representation["userId"], "user456");
}

#[test]
fn test_entities_response_order_matches_input() {
    // Response array order must match request representation order
    let representations = [
        json!({"__typename": "User", "id": "1"}),
        json!({"__typename": "User", "id": "2"}),
        json!({"__typename": "User", "id": "3"}),
    ];

    // Simulate response maintaining order
    let responses = [
        json!({"__typename": "User", "id": "1", "name": "Alice"}),
        json!({"__typename": "User", "id": "2", "name": "Bob"}),
        json!({"__typename": "User", "id": "3", "name": "Charlie"}),
    ];

    assert_eq!(representations.len(), responses.len());
    for (idx, rep) in representations.iter().enumerate() {
        assert_eq!(rep["id"], responses[idx]["id"]);
    }
}

#[test]
fn test_entities_response_can_include_null() {
    // Missing entities should be represented as null
    let responses = [
        json!({"__typename": "User", "id": "1", "name": "Alice"}),
        json!(null), // Entity not found
        json!({"__typename": "User", "id": "3", "name": "Charlie"}),
    ];

    assert!(responses[0].is_object());
    assert!(responses[1].is_null());
    assert!(responses[2].is_object());
}

// ============================================================================
// Service Metadata Requirements Tests
// ============================================================================

#[test]
fn test_service_query_returns_service_type() {
    // _service query returns _Service type with sdl field
    let response = json!({
        "_service": {
            "sdl": "type User @key(fields: \"id\") { id: ID! }"
        }
    });

    assert!(response["_service"].is_object());
    assert!(response["_service"]["sdl"].is_string());
}

#[test]
fn test_service_sdl_must_not_be_empty() {
    // SDL must not be empty
    let response = json!({
        "_service": {
            "sdl": ""
        }
    });

    let _sdl = response["_service"]["sdl"].as_str().unwrap();
    // In real implementation, SDL must be non-empty
    // This test just validates structure
    assert!(response["_service"].is_object());
}

#[test]
fn test_service_sdl_is_valid_graphql() {
    // SDL must be valid GraphQL schema language
    let sdl = r#"
        type User @key(fields: "id") {
            id: ID!
            name: String!
        }
    "#;

    // Validate basic GraphQL structure
    assert!(sdl.contains("type"));
    assert!(sdl.contains("@key"));
    assert!(sdl.contains("{"));
    assert!(sdl.contains("}"));
}

// ============================================================================
// Federation Directive Requirements Tests
// ============================================================================

#[test]
fn test_key_directive_required_on_entities() {
    // All entity types must have @key directive
    let fed_type = FederatedType {
        name:             "User".to_string(),
        keys:             vec![KeyDirective {
            fields:     vec!["id".to_string()],
            resolvable: true,
        }],
        is_extends:       false,
        external_fields:  vec![],
        shareable_fields: vec![],
        field_directives: std::collections::HashMap::new(),
    };

    assert!(!fed_type.keys.is_empty(), "Entity types must have @key directive");
}

#[test]
fn test_external_directive_on_extended_fields() {
    // Fields in @extends types must be marked @external if owned elsewhere
    let fed_type = FederatedType {
        name:             "Order".to_string(),
        keys:             vec![KeyDirective {
            fields:     vec!["id".to_string()],
            resolvable: true,
        }],
        is_extends:       true,
        external_fields:  vec!["customerId".to_string()],
        shareable_fields: vec![],
        field_directives: std::collections::HashMap::new(),
    };

    assert!(fed_type.is_extends);
    assert!(!fed_type.external_fields.is_empty());
}

#[test]
fn test_extends_directive_marks_extended_types() {
    // Extended types must have @extends
    let fed_type = FederatedType {
        name:             "Order".to_string(),
        keys:             vec![KeyDirective {
            fields:     vec!["id".to_string()],
            resolvable: true,
        }],
        is_extends:       true,
        external_fields:  vec!["customerId".to_string()],
        shareable_fields: vec![],
        field_directives: std::collections::HashMap::new(),
    };

    assert!(fed_type.is_extends);
}

// ============================================================================
// Type Reference Requirements Tests
// ============================================================================

#[test]
fn test_reference_includes_typename() {
    // References must include __typename for type discrimination
    let reference = json!({
        "__typename": "User",
        "id": "123"
    });

    assert!(reference.get("__typename").is_some());
    assert_eq!(reference["__typename"], "User");
}

#[test]
fn test_reference_includes_key_values() {
    // References must include all key field values for identification
    let key_fields = vec!["tenantId", "userId"];
    let reference = json!({
        "__typename": "TenantUser",
        "tenantId": "tenant123",
        "userId": "user456"
    });

    for key_field in key_fields {
        assert!(
            reference.get(key_field).is_some(),
            "Reference must include key field: {}",
            key_field
        );
    }
}

// ============================================================================
// Composition Rule Tests
// ============================================================================

#[test]
fn test_same_key_definition_across_subgraphs() {
    // Key definitions must be consistent across subgraphs
    let subgraph1_key = KeyDirective {
        fields:     vec!["id".to_string()],
        resolvable: true,
    };

    let subgraph2_key = KeyDirective {
        fields:     vec!["id".to_string()],
        resolvable: true,
    };

    assert_eq!(subgraph1_key.fields, subgraph2_key.fields);
}

#[test]
fn test_entity_ownership_is_exclusive() {
    // An entity can only be owned by one subgraph
    // (No two subgraphs should have is_extends: false for same type)
    let owner_subgraph = FederatedType {
        name:             "User".to_string(),
        keys:             vec![KeyDirective {
            fields:     vec!["id".to_string()],
            resolvable: true,
        }],
        is_extends:       false,
        external_fields:  vec![],
        shareable_fields: vec![],
        field_directives: std::collections::HashMap::new(),
    };

    let extending_subgraph = FederatedType {
        name:             "User".to_string(),
        keys:             vec![KeyDirective {
            fields:     vec!["id".to_string()],
            resolvable: true,
        }],
        is_extends:       true,
        external_fields:  vec![],
        shareable_fields: vec![],
        field_directives: std::collections::HashMap::new(),
    };

    // Only owner should have is_extends: false
    assert!(!owner_subgraph.is_extends);
    assert!(extending_subgraph.is_extends);
}

#[test]
fn test_external_fields_reference_owned_subgraph() {
    // External fields must be defined in the owning subgraph
    let extended_type = FederatedType {
        name:             "Order".to_string(),
        keys:             vec![KeyDirective {
            fields:     vec!["id".to_string()],
            resolvable: true,
        }],
        is_extends:       true,
        external_fields:  vec!["customerId".to_string()],
        shareable_fields: vec![],
        field_directives: std::collections::HashMap::new(),
    };

    // This subgraph extends Order and references customerId from another subgraph
    assert!(extended_type.is_extends);
    assert!(extended_type.external_fields.contains(&"customerId".to_string()));
}

// ============================================================================
// Version and Compatibility Tests
// ============================================================================

#[test]
fn test_federation_v2_version_string() {
    let metadata = FederationMetadata {
        enabled: true,
        version: "v2".to_string(),
        types:   vec![],
    };

    assert_eq!(metadata.version, "v2");
    // FraiseQL implements Apollo Federation v2
    assert!(metadata.version.starts_with("v"));
}

#[test]
fn test_federation_enabled_flag() {
    let enabled = FederationMetadata {
        enabled: true,
        version: "v2".to_string(),
        types:   vec![],
    };

    let disabled = FederationMetadata {
        enabled: false,
        version: "v2".to_string(),
        types:   vec![],
    };

    // Federation can be enabled or disabled per schema
    assert!(enabled.enabled);
    assert!(!disabled.enabled);
}

// ============================================================================
// Error Handling Tests
// ============================================================================

#[test]
fn test_missing_entity_returns_null() {
    // When an entity cannot be resolved, null is returned (not error)
    let response = json!(null);

    assert!(response.is_null());
}

#[test]
fn test_partial_failure_supported() {
    // Some entities can be found while others are not
    let responses = [
        json!({"__typename": "User", "id": "1"}),
        json!(null),
        json!({"__typename": "User", "id": "3"}),
    ];

    // Not all responses are null, but some are
    let has_valid = responses.iter().any(|r| r.is_object());
    let has_null = responses.iter().any(|r| r.is_null());

    assert!(has_valid);
    assert!(has_null);
}

#[test]
fn test_graphql_errors_formatted_correctly() {
    // GraphQL errors must follow standard format
    let error = json!({
        "message": "Field error message",
        "path": ["_entities", 0]
    });

    assert!(error["message"].is_string());
    assert!(error["path"].is_array());
}
