//! Mock relay controller for testing without hardware.
//!
//! This module provides a mock implementation of the relay controller
//! that stores state in memory, enabling testing without physical Modbus hardware.

use std::{
    collections::HashMap,
    sync::{Arc, Mutex, MutexGuard},
};

use async_trait::async_trait;

use crate::domain::relay::{
    controller::{ControllerError, RelayController},
    types::{RelayId, RelayState},
};

/// Mock relay controller for testing without physical Modbus hardware.
///
/// This implementation stores relay states in memory using a thread-safe
/// `Arc<Mutex<HashMap>>`, enabling concurrent access in tests. It provides
/// optional timeout simulation for testing error handling scenarios.
#[derive(Debug, Clone)]
pub struct MockRelayController {
    states: Arc<Mutex<HashMap<RelayId, RelayState>>>,
    firmware_version: Option<String>,
    simulate_timeout: bool,
}

impl MockRelayController {
    /// Creates a new mock relay controller with default configuration.
    ///
    /// The controller initializes with:
    /// - Empty relay state map (no relays configured)
    /// - Firmware version set to "v2.00"
    /// - Timeout simulation disabled
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }

    /// Enables timeout simulation for testing error handling.
    ///
    /// When enabled, all operations will simulate a 4-second delay followed
    /// by a timeout error. This is useful for testing timeout handling in
    /// application code.
    #[must_use]
    pub const fn with_timeout_simulation(mut self) -> Self {
        self.simulate_timeout = true;
        self
    }

    async fn maybe_timeout(&self) -> Result<(), ControllerError> {
        if self.simulate_timeout {
            tokio::time::sleep(tokio::time::Duration::from_secs(4)).await;
            Err(ControllerError::Timeout(3))
        } else {
            Ok(())
        }
    }

    fn states(&self) -> Result<MutexGuard<'_, HashMap<RelayId, RelayState>>, ControllerError> {
        self.states
            .lock()
            .map_err(|e| ControllerError::ModbusException(e.to_string()))
    }
}

impl Default for MockRelayController {
    fn default() -> Self {
        let hashmap: HashMap<RelayId, RelayState> = HashMap::new();
        Self {
            states: Arc::new(Mutex::new(hashmap)),
            firmware_version: Some("v2.00".to_string()),
            simulate_timeout: false,
        }
    }
}

#[async_trait]
impl RelayController for MockRelayController {
    async fn read_relay_state(&self, id: RelayId) -> Result<RelayState, ControllerError> {
        self.maybe_timeout().await?;
        let states = self.states()?;
        states.get(&id).map_or_else(
            || Err(ControllerError::InvalidRelayId(id.as_u8())),
            |state| Ok(*state),
        )
    }

    async fn write_relay_state(
        &self,
        id: RelayId,
        state: RelayState,
    ) -> Result<(), ControllerError> {
        self.maybe_timeout().await?;
        self.states()?.insert(id, state);
        Ok(())
    }

    async fn read_all_states(&self) -> Result<Vec<RelayState>, ControllerError> {
        self.maybe_timeout().await?;
        let mut vec: Vec<(RelayId, RelayState)> = self
            .states()?
            .iter()
            .map(|(id, state)| (*id, *state))
            .collect();
        vec.sort_by_key(|v| v.0);
        Ok(vec.iter().map(|v| v.1).collect())
    }

    async fn write_all_states(&self, states: Vec<RelayState>) -> Result<(), ControllerError> {
        self.maybe_timeout().await?;
        let mut keys: Vec<RelayId> = self.states()?.keys().copied().collect();
        keys.sort();
        for update in keys.iter().zip(states) {
            self.states()?.insert(*update.0, update.1);
        }
        Ok(())
    }

    async fn check_connection(&self) -> Result<(), ControllerError> {
        Ok(())
    }

    async fn get_firmware_version(&self) -> Result<Option<String>, ControllerError> {
        Ok(self.firmware_version.clone())
    }
}

#[cfg(test)]
mod tests {
    use super::MockRelayController;
    use crate::domain::relay::types::RelayId;

    #[tokio::test]
    async fn test_read_state_returns_mocked_state() {
        // Test: read_relay_state() returns mocked state
        //
        // Setup: Create a mock controller and set relay 1 to On
        // Expected: read_relay_state(1) should return On

        use crate::domain::relay::{controller::RelayController, types::RelayState};

        let controller = MockRelayController::new();
        let relay_id = RelayId::new(1).unwrap();

        // Write a known state
        controller
            .write_relay_state(relay_id, RelayState::On)
            .await
            .unwrap();

        // Read it back
        let state = controller.read_relay_state(relay_id).await.unwrap();
        assert_eq!(state, RelayState::On);
    }

    #[tokio::test]
    async fn test_write_state_updates_mocked_state() {
        // Test: write_relay_state() updates mocked state
        //
        // Setup: Create a mock controller with relay 3 initialized to Off
        // Action: Write relay 3 to On, then read it back
        // Expected: State should be On

        use crate::domain::relay::{controller::RelayController, types::RelayState};

        let controller = MockRelayController::new();
        let relay_id = RelayId::new(3).unwrap();

        // Initialize relay 3 to Off
        controller
            .write_relay_state(relay_id, RelayState::Off)
            .await
            .unwrap();

        // Verify initial state
        let initial_state = controller.read_relay_state(relay_id).await.unwrap();
        assert_eq!(initial_state, RelayState::Off);

        // Write On
        controller
            .write_relay_state(relay_id, RelayState::On)
            .await
            .unwrap();

        // Verify it changed
        let updated_state = controller.read_relay_state(relay_id).await.unwrap();
        assert_eq!(updated_state, RelayState::On);
    }

    #[tokio::test]
    async fn test_read_all_returns_8_relays_in_known_state() {
        // Test: read_all_states() returns 8 relays in known state
        //
        // Setup: Create a mock controller, initialize all 8 relays, set relays 1, 3, 5 to On, others Off
        // Action: Call read_all_states()
        // Expected: Returns Vec of 8 RelayState values in correct order

        use crate::domain::relay::{controller::RelayController, types::RelayState};

        let controller = MockRelayController::new();

        // Initialize all 8 relays to Off first
        for i in 1..=8 {
            controller
                .write_relay_state(RelayId::new(i).unwrap(), RelayState::Off)
                .await
                .unwrap();
        }

        // Set specific relays to On
        controller
            .write_relay_state(RelayId::new(1).unwrap(), RelayState::On)
            .await
            .unwrap();
        controller
            .write_relay_state(RelayId::new(3).unwrap(), RelayState::On)
            .await
            .unwrap();
        controller
            .write_relay_state(RelayId::new(5).unwrap(), RelayState::On)
            .await
            .unwrap();

        // Read all states
        let all_states = controller.read_all_states().await.unwrap();

        // Verify we have exactly 8 relays
        assert_eq!(all_states.len(), 8);

        // Verify specific states (indexed 0-7, corresponding to relays 1-8)
        assert_eq!(all_states[0], RelayState::On); // Relay 1
        assert_eq!(all_states[1], RelayState::Off); // Relay 2
        assert_eq!(all_states[2], RelayState::On); // Relay 3
        assert_eq!(all_states[3], RelayState::Off); // Relay 4
        assert_eq!(all_states[4], RelayState::On); // Relay 5
        assert_eq!(all_states[5], RelayState::Off); // Relay 6
        assert_eq!(all_states[6], RelayState::Off); // Relay 7
        assert_eq!(all_states[7], RelayState::Off); // Relay 8
    }

    #[tokio::test]
    async fn test_write_state_for_all_8_relays() {
        // Test: Can write state to all 8 relays independently
        //
        // Setup: Create a mock controller
        // Action: Write different states to each relay
        // Expected: Each relay maintains its own independent state

        use crate::domain::relay::{controller::RelayController, types::RelayState};

        let controller = MockRelayController::new();

        // Write alternating states (On, Off, On, Off, ...)
        for i in 1..=8 {
            let relay_id = RelayId::new(i).unwrap();
            let state = if i % 2 == 1 {
                RelayState::On
            } else {
                RelayState::Off
            };
            controller.write_relay_state(relay_id, state).await.unwrap();
        }

        // Verify each relay has correct state
        for i in 1..=8 {
            let relay_id = RelayId::new(i).unwrap();
            let expected_state = if i % 2 == 1 {
                RelayState::On
            } else {
                RelayState::Off
            };
            let actual_state = controller.read_relay_state(relay_id).await.unwrap();
            assert_eq!(
                actual_state, expected_state,
                "Relay {i} has incorrect state",
            );
        }
    }

    #[tokio::test]
    async fn test_read_state_with_invalid_relay_id() {
        // Test: read_state() with out-of-range relay ID fails gracefully
        //
        // Note: RelayId::new() will already fail for invalid IDs (0 or 9+),
        // so this test verifies the type system prevents invalid relay IDs
        // at construction time (type-driven design)

        // Verify RelayId construction fails for invalid IDs
        assert!(RelayId::new(0).is_err(), "RelayId::new(0) should fail");
        assert!(RelayId::new(9).is_err(), "RelayId::new(9) should fail");

        // If we somehow get an invalid relay ID through (which shouldn't be possible),
        // the controller should handle it gracefully (tested in T029 implementation)
    }

    #[tokio::test]
    async fn test_concurrent_access_is_safe() {
        // Test: MockRelayController is thread-safe (uses Arc<Mutex<HashMap>>)
        //
        // Setup: Create mock controller, spawn multiple tasks that read/write
        // Expected: No data races, all operations complete successfully

        use std::sync::Arc;

        use crate::domain::relay::{controller::RelayController, types::RelayState};

        let controller = Arc::new(MockRelayController::new());
        let relay_id = RelayId::new(1).unwrap();

        // Initialize relay 1 to Off
        controller
            .write_relay_state(relay_id, RelayState::Off)
            .await
            .unwrap();

        // Spawn 10 tasks that toggle relay 1
        let mut handles = vec![];
        for _ in 0..10 {
            let controller_clone = Arc::clone(&controller);
            let handle = tokio::spawn(async move {
                let relay_id = RelayId::new(1).unwrap();
                let current_state = controller_clone.read_relay_state(relay_id).await.unwrap();
                let new_state = match current_state {
                    RelayState::On => RelayState::Off,
                    RelayState::Off => RelayState::On,
                };
                controller_clone
                    .write_relay_state(relay_id, new_state)
                    .await
                    .unwrap();
            });
            handles.push(handle);
        }

        // Wait for all tasks to complete
        for handle in handles {
            handle.await.unwrap();
        }

        // Controller should still be in valid state (either On or Off)
        let final_state = controller.read_relay_state(relay_id).await.unwrap();
        assert!(matches!(final_state, RelayState::On | RelayState::Off));
    }
}