//! Federation Saga Coordination Tests
//!
//! Tests for multi-step distributed transaction execution with automatic
//! compensation on failure. Saga coordinator orchestrates mutations across
//! multiple subgraphs with transactional guarantees.

use std::collections::HashMap;

use uuid::Uuid;

/// Test fixtures: Saga step definitions with forward and compensation actions
///
/// Each step represents a mutation that can be executed forward and compensated backward.
mod fixtures {
    use super::*;

    /// Represents a single step in a saga (forward mutation)
    #[derive(Debug, Clone)]
    pub struct SagaStepDefinition {
        #[allow(dead_code)]
        pub id:                     Uuid,
        pub number:                 u32,
        pub subgraph:               String,
        pub typename:               String,
        pub mutation_name:          String,
        pub variables:              serde_json::Value,
        pub compensation_mutation:  String,
        pub compensation_variables: serde_json::Value,
    }

    impl SagaStepDefinition {
        pub fn new(
            number: u32,
            subgraph: &str,
            typename: &str,
            mutation_name: &str,
            variables: serde_json::Value,
            compensation_mutation: &str,
            compensation_variables: serde_json::Value,
        ) -> Self {
            Self {
                id: Uuid::new_v4(),
                number,
                subgraph: subgraph.to_string(),
                typename: typename.to_string(),
                mutation_name: mutation_name.to_string(),
                variables,
                compensation_mutation: compensation_mutation.to_string(),
                compensation_variables,
            }
        }
    }

    /// Create a 3-step saga for creating an order with inventory
    /// Step 1: Create order in orders-service
    /// Step 2: Reserve inventory in inventory-service
    /// Step 3: Record payment in billing-service
    pub fn create_three_step_order_saga() -> Vec<SagaStepDefinition> {
        vec![
            SagaStepDefinition::new(
                1,
                "orders-service",
                "Order",
                "createOrder",
                serde_json::json!({
                    "id": "order-123",
                    "customerId": "cust-456",
                    "items": [
                        {"productId": "prod-1", "quantity": 2},
                        {"productId": "prod-2", "quantity": 1}
                    ],
                    "total": 150.00
                }),
                "deleteOrder",
                serde_json::json!({"id": "order-123"}),
            ),
            SagaStepDefinition::new(
                2,
                "inventory-service",
                "Inventory",
                "reserveInventory",
                serde_json::json!({
                    "orderId": "order-123",
                    "items": [
                        {"productId": "prod-1", "quantity": 2},
                        {"productId": "prod-2", "quantity": 1}
                    ]
                }),
                "releaseInventory",
                serde_json::json!({"orderId": "order-123"}),
            ),
            SagaStepDefinition::new(
                3,
                "billing-service",
                "Payment",
                "recordPayment",
                serde_json::json!({
                    "orderId": "order-123",
                    "customerId": "cust-456",
                    "amount": 150.00,
                    "method": "credit_card"
                }),
                "reversePayment",
                serde_json::json!({"orderId": "order-123"}),
            ),
        ]
    }

    /// Create a 2-step saga for user registration with profile
    /// Step 1: Create user in users-service
    /// Step 2: Create profile in profiles-service
    pub fn create_two_step_user_registration_saga() -> Vec<SagaStepDefinition> {
        vec![
            SagaStepDefinition::new(
                1,
                "users-service",
                "User",
                "createUser",
                serde_json::json!({
                    "id": "user-789",
                    "email": "alice@example.com",
                    "name": "Alice Smith",
                    "password_hash": "hash_xyz"
                }),
                "deleteUser",
                serde_json::json!({"id": "user-789"}),
            ),
            SagaStepDefinition::new(
                2,
                "profiles-service",
                "Profile",
                "createProfile",
                serde_json::json!({
                    "userId": "user-789",
                    "displayName": "alice_s",
                    "bio": "GraphQL enthusiast",
                    "avatar": "https://example.com/avatar.jpg"
                }),
                "deleteProfile",
                serde_json::json!({"userId": "user-789"}),
            ),
        ]
    }
}

// ===========================================================================================
// CATEGORY 1: Basic Saga Execution (Happy Path)
// ===========================================================================================

#[test]
fn test_saga_executor_creation() {
    // Given: A saga coordinator is created
    // When: Coordinator is instantiated
    // Then: It should be created successfully

    // Placeholder: Full implementation in GREEN phase
}

#[test]
fn test_execute_single_step_saga() {
    // Given: A saga with a single mutation step
    let _saga_id = Uuid::new_v4();
    let steps = [fixtures::create_three_step_order_saga()[0].clone()];

    // When: Saga coordinator executes the saga
    // Then: Step should execute successfully
    // And: Saga should transition to Completed state

    // Placeholder: Full implementation in GREEN phase
    assert_eq!(steps.len(), 1);
}

#[test]
fn test_execute_multi_step_saga_successfully() {
    // Given: A 3-step saga for creating order with inventory and payment
    let _saga_id = Uuid::new_v4();
    let steps = fixtures::create_three_step_order_saga();

    // When: Saga coordinator executes all steps
    // Then: All steps should execute in order (1 → 2 → 3)
    // And: Saga should transition to Completed state
    // And: All steps should have Completed state

    assert_eq!(steps.len(), 3);
    assert_eq!(steps[0].number, 1);
    assert_eq!(steps[1].number, 2);
    assert_eq!(steps[2].number, 3);
}

#[test]
fn test_saga_maintains_step_order() {
    // Given: A saga with steps in specific order
    let steps = fixtures::create_three_step_order_saga();

    // When: Saga is created
    // Then: Steps should maintain execution order
    // And: Each step should have correct number

    for (i, step) in steps.iter().enumerate() {
        assert_eq!(step.number, (i + 1) as u32);
    }
}

#[test]
fn test_saga_preserves_mutation_metadata() {
    // Given: Steps with specific mutation names
    let steps = fixtures::create_three_step_order_saga();

    // When: Saga is processed
    // Then: Each step should retain mutation_name
    // And: Subgraph should be preserved
    // And: Variables should be preserved

    assert_eq!(steps[0].mutation_name, "createOrder");
    assert_eq!(steps[0].subgraph, "orders-service");
    assert_eq!(steps[1].mutation_name, "reserveInventory");
    assert_eq!(steps[1].subgraph, "inventory-service");
}

// ===========================================================================================
// CATEGORY 2: Saga Execution with Step Failure
// ===========================================================================================

#[test]
fn test_saga_fails_on_first_step_failure() {
    // Given: A 3-step saga for order creation
    let _saga_id = Uuid::new_v4();
    let steps = fixtures::create_three_step_order_saga();

    // When: First step (createOrder) fails
    // Then: Saga should transition to Failed state
    // And: Steps 2 and 3 should NOT execute

    assert_eq!(steps.len(), 3);
    // Placeholder: Execution logic in GREEN phase
}

#[test]
fn test_saga_fails_on_middle_step_failure() {
    // Given: A 3-step saga and first step succeeds
    let steps = fixtures::create_three_step_order_saga();

    // When: Second step (reserveInventory) fails
    // Then: Saga should transition to Failed state
    // And: Step 3 should NOT execute
    // And: Step 1 should remain Completed

    assert_eq!(steps[1].mutation_name, "reserveInventory");
    // Placeholder: Execution logic in GREEN phase
}

#[test]
fn test_saga_fails_on_last_step_failure() {
    // Given: A 3-step saga and first two steps succeed
    let steps = fixtures::create_three_step_order_saga();

    // When: Third step (recordPayment) fails
    // Then: Saga should transition to Failed state
    // And: Steps 1 and 2 should remain Completed
    // And: Compensation should be triggered

    assert_eq!(steps[2].mutation_name, "recordPayment");
    // Placeholder: Execution logic in GREEN phase
}

#[test]
fn test_saga_error_includes_failed_step_context() {
    // Given: A saga step that will fail
    let _saga_id = Uuid::new_v4();
    let step = fixtures::create_three_step_order_saga()[0].clone();

    // When: Step execution fails
    // Then: Error should include:
    //   - Step number
    //   - Subgraph name
    //   - Mutation name
    //   - Original variables

    assert_eq!(step.number, 1);
    assert_eq!(step.subgraph, "orders-service");
}

#[test]
fn test_saga_partial_failure_state_tracking() {
    // Given: A 3-step saga where step 2 fails
    let steps = fixtures::create_three_step_order_saga();

    // When: Step 1 succeeds, Step 2 fails, Step 3 not executed
    // Then: Saga state should reflect:
    //   - Step 1: Completed
    //   - Step 2: Failed
    //   - Step 3: Pending (not executed)

    assert!(steps.len() >= 3);
    // Placeholder: State tracking in GREEN phase
}

// ===========================================================================================
// CATEGORY 3: Automatic Compensation
// ===========================================================================================

#[test]
fn test_compensation_triggered_on_failure() {
    // Given: A 3-step saga where step 3 fails
    let _saga_id = Uuid::new_v4();
    let steps = fixtures::create_three_step_order_saga();

    // When: Step 3 fails after steps 1 and 2 succeed
    // Then: Saga should transition to Compensating state
    // And: Compensation mutations should be queued

    assert_eq!(steps[2].compensation_mutation, "reversePayment");
}

#[test]
fn test_compensation_executes_in_reverse_order() {
    // Given: A 3-step saga needing compensation
    let steps = fixtures::create_three_step_order_saga();

    // When: Compensation phase begins
    // Then: Compensation should execute in REVERSE order:
    //   - Step 3 compensation first
    //   - Step 2 compensation second
    //   - Step 1 compensation third

    let compensation_order = [
        steps[2].compensation_mutation.clone(),
        steps[1].compensation_mutation.clone(),
        steps[0].compensation_mutation.clone(),
    ];

    assert_eq!(compensation_order[0], "reversePayment");
    assert_eq!(compensation_order[1], "releaseInventory");
    assert_eq!(compensation_order[2], "deleteOrder");
}

#[test]
fn test_compensation_uses_original_step_variables() {
    // Given: Step 1 with variables {"id": "order-123"}
    let steps = fixtures::create_three_step_order_saga();
    let step_1 = &steps[0];

    // When: Compensation is built for step 1
    // Then: Compensation should use variables from original step
    //   - For deleteOrder, use id from original createOrder

    assert_eq!(
        step_1.compensation_variables.get("id").and_then(|v| v.as_str()),
        Some("order-123")
    );
}

#[test]
fn test_compensation_preserves_step_context() {
    // Given: Original step with subgraph and typename
    let steps = fixtures::create_three_step_order_saga();
    let step_1 = &steps[0];

    // When: Compensation is built
    // Then: Compensation should preserve:
    //   - Same subgraph
    //   - Same typename
    //   - Only mutation name and variables change

    assert_eq!(step_1.subgraph, "orders-service");
    assert_eq!(step_1.typename, "Order");
    assert_eq!(step_1.compensation_mutation, "deleteOrder");
}

#[test]
fn test_all_compensations_execute_even_if_one_fails() {
    // Given: A 3-step saga in compensation phase
    let steps = fixtures::create_three_step_order_saga();

    // When: Step 2 compensation fails
    // Then: Step 1 and 3 compensations should STILL execute
    // And: Saga should record which compensations failed
    // And: Saga state should be CompensationFailed (not Compensated)

    // Placeholder: Compensation resilience in GREEN phase
    assert!(steps.len() >= 3);
}

#[test]
fn test_compensation_phase_transitions() {
    // Given: A failed saga ready for compensation
    // When: Compensation phase begins
    // Then: Saga transitions: Failed → Compensating → Compensated

    // Placeholder: State machine in GREEN phase
}

// ===========================================================================================
// CATEGORY 4: Saga Persistence and Recovery
// ===========================================================================================

#[test]
fn test_saga_state_persisted_to_store() {
    // Given: A saga coordinator with PostgreSQL store
    let _saga_id = Uuid::new_v4();

    // When: Saga is executed
    // Then: Saga state should be persisted
    // And: Each step state should be persisted

    // Placeholder: Store integration in GREEN phase
}

#[test]
fn test_saga_recovered_from_interrupted_execution() {
    // Given: A saga that was interrupted mid-execution (e.g., server crash)
    let _saga_id = Uuid::new_v4();

    // When: Saga coordinator starts and finds interrupted saga
    // Then: Saga should resume from last completed step
    // And: Completed steps should not re-execute
    // And: Next pending step should execute

    // Placeholder: Recovery logic in GREEN phase
}

#[test]
fn test_saga_recovered_from_interrupted_compensation() {
    // Given: A saga in compensation phase that was interrupted
    let _saga_id = Uuid::new_v4();

    // When: Saga coordinator recovers
    // Then: Compensation should resume from last uncompensated step
    // And: Already-compensated steps should not re-compensate

    // Placeholder: Recovery logic in GREEN phase
}

#[test]
fn test_each_step_persists_result_data() {
    // Given: A saga step that executes successfully
    let steps = fixtures::create_three_step_order_saga();
    let step = &steps[0];

    // When: Step executes
    // Then: Result data should be persisted
    // And: Result should be queryable by step ID

    // Placeholder: Result persistence in GREEN phase
    assert_eq!(step.number, 1);
}

#[test]
fn test_saga_metadata_persisted() {
    // Given: A saga with metadata (e.g., user_id, request_id)
    let _saga_id = Uuid::new_v4();
    let mut metadata = HashMap::new();
    metadata.insert("user_id", "user-123");
    metadata.insert("request_id", "req-456");

    // When: Saga is saved
    // Then: Metadata should be persisted as JSON
    // And: Metadata should be retrievable

    // Placeholder: Metadata handling in GREEN phase
    assert_eq!(metadata.len(), 2);
}

#[test]
fn test_saga_timestamps_recorded() {
    // Given: A saga that starts and completes
    let _saga_id = Uuid::new_v4();

    // When: Saga executes
    // Then: created_at should be recorded at start
    // And: completed_at should be recorded at finish
    // And: Each step should have start and completion times

    // Placeholder: Timestamp recording in GREEN phase
}

// ===========================================================================================
// CATEGORY 5: Compensation Strategy Selection
// ===========================================================================================

#[test]
fn test_automatic_compensation_strategy() {
    // Given: A saga using AUTOMATIC compensation strategy
    let _saga_id = Uuid::new_v4();

    // When: A step fails
    // Then: Compensation should execute automatically without waiting
    // And: All previously completed steps should be compensated

    // Placeholder: Strategy in GREEN phase
}

#[test]
fn test_manual_compensation_strategy() {
    // Given: A saga using MANUAL compensation strategy
    let _saga_id = Uuid::new_v4();

    // When: A step fails
    // Then: Saga should transition to ManualCompensationRequired
    // And: Compensation should NOT execute automatically
    // And: External system should trigger compensation

    // Placeholder: Strategy in GREEN phase
}

#[test]
fn test_compensation_strategy_per_saga() {
    // Given: Multiple sagas with different strategies
    let saga_auto_id = Uuid::new_v4();
    let saga_manual_id = Uuid::new_v4();

    // When: Both sagas encounter failures
    // Then: Saga 1 (automatic) should compensate automatically
    // And: Saga 2 (manual) should wait for manual trigger

    // Placeholder: Per-saga strategy in GREEN phase
    assert!(saga_auto_id != saga_manual_id);
}

// ===========================================================================================
// CATEGORY 6: Cross-Subgraph Saga Coordination
// ===========================================================================================

#[test]
fn test_saga_spans_multiple_subgraphs() {
    // Given: A saga with steps in 3 different subgraphs
    let steps = fixtures::create_three_step_order_saga();

    // When: Saga is executed
    // Then: Coordinator should execute mutations in each subgraph
    // And: Order should be maintained across subgraph boundaries
    // And: Failure in any subgraph should trigger compensation in all

    let subgraphs: std::collections::HashSet<_> =
        steps.iter().map(|s| s.subgraph.clone()).collect();
    assert_eq!(subgraphs.len(), 3);
}

#[test]
fn test_saga_coordinates_dependent_steps() {
    // Given: A user registration saga (user → profile)
    let steps = fixtures::create_two_step_user_registration_saga();

    // When: Saga executes
    // Then: Step 1 (createUser) should complete before Step 2 starts
    // And: Step 2 should receive data from Step 1 (user_id)

    let user_id = steps[1].variables.get("userId").and_then(|v| v.as_str());
    assert_eq!(user_id, Some("user-789"));
}

#[test]
fn test_saga_isolates_steps_across_subgraphs() {
    // Given: Multiple concurrent sagas for different orders
    let saga_1 = Uuid::new_v4();
    let saga_2 = Uuid::new_v4();

    // When: Both sagas execute in parallel
    // Then: Each saga should execute independently
    // And: Saga 1 failure should NOT affect Saga 2
    // And: Saga 1 compensation should NOT affect Saga 2

    assert_ne!(saga_1, saga_2);
}

#[test]
fn test_saga_handles_timeout_in_subgraph() {
    // Given: A saga step that times out (subgraph unavailable)
    let _saga_id = Uuid::new_v4();
    let steps = fixtures::create_three_step_order_saga();

    // When: Step 2 times out
    // Then: Saga should transition to Failed state
    // And: Step 1 should be compensated
    // And: Timeout error should be included in saga result

    // Placeholder: Timeout handling in GREEN phase
    assert_eq!(steps[1].subgraph, "inventory-service");
}

#[test]
fn test_saga_detects_network_partition() {
    // Given: A saga where subgraph is unreachable
    let _saga_id = Uuid::new_v4();

    // When: Coordinator attempts to execute step
    // Then: Should detect network partition
    // And: Should fail saga and trigger compensation
    // And: Should log partition detection for operations team

    // Placeholder: Partition detection in GREEN phase
}

#[test]
fn test_saga_distinguishes_failure_types() {
    // Given: A saga that fails
    // When: Failure occurs
    // Then: Saga should categorize failure:
    //   - StepFailure (mutation returned error)
    //   - TimeoutFailure (step exceeded time limit)
    //   - NetworkFailure (subgraph unreachable)
    //   - CompensationFailure (compensation step failed)

    // Placeholder: Failure categorization in GREEN phase
}

// ===========================================================================================
// CATEGORY 7: Error Handling and Edge Cases
// ===========================================================================================

#[test]
fn test_saga_creation_fails_with_empty_steps() {
    // Given: Attempting to create saga with no steps
    // When: SagaCoordinator::create_saga is called with empty steps
    // Then: Should return error
    // And: Error should indicate "saga must have at least one step"

    // Placeholder: Validation in GREEN phase
}

#[test]
fn test_saga_creation_validates_step_order() {
    // Given: Steps with numbers out of sequence (1, 3, 2)
    // When: SagaCoordinator::create_saga is called
    // Then: Should reorder steps to correct sequence
    // Or: Should return error indicating invalid ordering

    // Placeholder: Order validation in GREEN phase
}

#[test]
fn test_saga_handles_duplicate_step_ids() {
    // Given: Two steps with the same ID
    // When: Saga is created
    // Then: Should generate new unique IDs for duplicate steps
    // Or: Should return error indicating duplicate IDs

    // Placeholder: ID validation in GREEN phase
}

#[test]
fn test_saga_validates_subgraph_exists() {
    // Given: A step references non-existent subgraph "invalid-service"
    // When: Saga is executed
    // Then: Should fail with "Subgraph not found" error
    // And: Saga state should be Failed
    // And: No compensation should be triggered (no steps executed)

    // Placeholder: Subgraph validation in GREEN phase
}

#[test]
fn test_saga_validates_mutation_exists() {
    // Given: A step references non-existent mutation "invalidMutation"
    // When: Saga is executed
    // Then: Should fail with "Mutation not found" error
    // And: Saga state should be Failed

    // Placeholder: Mutation validation in GREEN phase
}

#[test]
fn test_saga_handles_idempotent_execution() {
    // Given: A saga that's been executed and persisted
    let _saga_id = Uuid::new_v4();

    // When: Same saga is executed again with same ID
    // Then: Should recognize as duplicate
    // And: Should return existing saga state
    // And: Should NOT re-execute steps

    // Placeholder: Idempotency in GREEN phase
}

#[test]
fn test_compensation_idempotency() {
    // Given: A compensation that's been executed
    let _saga_id = Uuid::new_v4();

    // When: Compensation is executed again (e.g., retry)
    // Then: Compensation should be idempotent
    // And: Re-executing should produce same result

    // Placeholder: Compensation idempotency in GREEN phase
}

// ===========================================================================================
// CATEGORY 8: Saga Coordinator API
// ===========================================================================================

#[test]
fn test_saga_coordinator_create() {
    // Given: Steps for a saga
    let steps = fixtures::create_three_step_order_saga();

    // When: SagaCoordinator::create_saga is called
    // Then: Should return SagaId
    // And: Saga should be in Pending state

    // Placeholder: API in GREEN phase
    assert!(steps.len() == 3);
}

#[test]
fn test_saga_coordinator_execute() {
    // Given: A saga in Pending state
    let _saga_id = Uuid::new_v4();

    // When: SagaCoordinator::execute_saga is called
    // Then: Saga should transition to Executing state
    // And: Steps should execute sequentially

    // Placeholder: API in GREEN phase
}

#[test]
fn test_saga_coordinator_get_status() {
    // Given: A saga that's executing
    let _saga_id = Uuid::new_v4();

    // When: SagaCoordinator::get_saga_status is called
    // Then: Should return:
    //   - Current saga state
    //   - Step states
    //   - Completed step count
    //   - Started at timestamp
    //   - Progress percentage

    // Placeholder: API in GREEN phase
}

#[test]
fn test_saga_coordinator_cancel() {
    // Given: A saga in Executing state
    let _saga_id = Uuid::new_v4();

    // When: SagaCoordinator::cancel_saga is called
    // Then: Currently executing step should stop
    // And: Pending steps should not execute
    // And: Compensation should begin
    // And: Saga should transition to Failed (due to cancellation)

    // Placeholder: API in GREEN phase
}

#[test]
fn test_saga_coordinator_get_result() {
    // Given: A completed saga
    let _saga_id = Uuid::new_v4();

    // When: SagaCoordinator::get_saga_result is called
    // Then: Should return:
    //   - Final saga state
    //   - All step results
    //   - Execution duration
    //   - Any errors

    // Placeholder: API in GREEN phase
}

#[test]
fn test_saga_coordinator_list_in_flight() {
    // Given: Multiple sagas in various states
    // When: SagaCoordinator::list_in_flight_sagas is called
    // Then: Should return:
    //   - All sagas in Executing, Compensating, or PendingCompensation states
    //   - Can filter by state or subgraph
    //   - Can order by start time

    // Placeholder: API in GREEN phase
}

// ===========================================================================================
// CATEGORY 9: Observability and Logging
// ===========================================================================================

#[test]
fn test_saga_logs_execution_start() {
    // Given: A saga about to execute
    // When: Execution begins
    // Then: Should log at INFO level:
    //   - Saga ID
    //   - Step count
    //   - Target subgraphs

    // Placeholder: Logging in GREEN phase
}

#[test]
fn test_saga_logs_step_execution() {
    // Given: A saga executing a step
    // When: Step starts
    // Then: Should log at DEBUG level:
    //   - Saga ID
    //   - Step number and name
    //   - Subgraph
    //   - Mutation name

    // Placeholder: Logging in GREEN phase
}

#[test]
fn test_saga_logs_failure_with_context() {
    // Given: A saga step that fails
    // When: Failure occurs
    // Then: Should log at WARN level:
    //   - Saga ID
    //   - Step number
    //   - Error message
    //   - Completed step count
    //   - Whether compensation is triggered

    // Placeholder: Logging in GREEN phase
}

#[test]
fn test_saga_logs_compensation_start() {
    // Given: Saga entering compensation phase
    // When: Compensation begins
    // Then: Should log at INFO level:
    //   - Saga ID
    //   - Number of steps to compensate
    //   - Reason for compensation

    // Placeholder: Logging in GREEN phase
}

#[test]
fn test_saga_exports_metrics() {
    // Given: A saga that's completed
    // When: Saga finishes
    // Then: Should emit metrics:
    //   - federation_sagas_total{state=completed}
    //   - federation_saga_duration_seconds histogram
    //   - federation_saga_steps_executed_total
    //   - federation_saga_compensations_total

    // Placeholder: Metrics in GREEN phase
}
