//! ROCm backend for ToRSh deep learning framework
//!
//! This module provides GPU acceleration for tensor operations using AMD ROCm platform
//! and HIP API. It follows the same architectural patterns as the CUDA backend but
//! targets AMD GPUs for high-performance computing workloads.

use std::sync::Arc;

/// ROCm-specific error types
#[derive(Debug, thiserror::Error)]
pub enum RocmError {
    #[error("ROCm runtime not available")]
    RuntimeNotAvailable,
    #[error("No ROCm devices found")]
    NoDevicesFound,
    #[error("Device {0} not found")]
    DeviceNotFound(usize),
    #[error("ROCm initialization failed: {0}")]
    InitializationFailed(String),
    #[error("Memory allocation failed: {0} bytes")]
    MemoryAllocationFailed(usize),
    #[error("HIP error: {0}")]
    HipError(String),
    #[error("MIOpen error: {0}")]
    MiOpenError(String),
}

/// ROCm device information
#[derive(Debug, Clone)]
pub struct RocmDeviceInfo {
    pub device_id: usize,
    pub name: String,
    pub compute_capability: (u32, u32),
    pub total_memory: usize,
    pub multiprocessor_count: u32,
    pub warp_size: u32,
    pub max_threads_per_block: u32,
    pub is_integrated: bool,
}

/// ROCm device management
pub struct RocmDevice {
    info: RocmDeviceInfo,
    context_initialized: bool,
}

impl RocmDevice {
    /// Create a new ROCm device
    pub fn new(device_id: usize) -> Result<Self, RocmError> {
        if !is_available() {
            return Err(RocmError::RuntimeNotAvailable);
        }

        let info = get_device_info(device_id)?;

        Ok(Self {
            info,
            context_initialized: false,
        })
    }

    /// Initialize the device context
    pub fn initialize(&mut self) -> Result<(), RocmError> {
        if self.context_initialized {
            return Ok(());
        }

        // Mock HIP context initialization
        // In real implementation, this would call hipSetDevice() and hipCtxCreate()

        self.context_initialized = true;
        Ok(())
    }

    /// Get device information
    pub fn info(&self) -> &RocmDeviceInfo {
        &self.info
    }

    /// Check if device context is initialized
    pub fn is_initialized(&self) -> bool {
        self.context_initialized
    }

    /// Get available memory on the device
    pub fn available_memory(&self) -> Result<usize, RocmError> {
        if !self.context_initialized {
            return Err(RocmError::InitializationFailed(
                "Device not initialized".to_string(),
            ));
        }

        // Mock memory query - in real implementation, this would call hipMemGetInfo()
        Ok(self.info.total_memory * 8 / 10) // Assume 80% available
    }

    /// Synchronize device operations
    pub fn synchronize(&self) -> Result<(), RocmError> {
        if !self.context_initialized {
            return Err(RocmError::InitializationFailed(
                "Device not initialized".to_string(),
            ));
        }

        // Mock synchronization - in real implementation, this would call hipDeviceSynchronize()
        Ok(())
    }
}

/// ROCm backend implementation
pub struct RocmBackend {
    devices: Vec<Arc<RocmDevice>>,
    default_device_id: usize,
}

impl RocmBackend {
    /// Create a new ROCm backend
    pub fn new() -> Result<Self, RocmError> {
        if !is_available() {
            return Err(RocmError::RuntimeNotAvailable);
        }

        let device_count = device_count().unwrap_or(0);
        if device_count == 0 {
            return Err(RocmError::NoDevicesFound);
        }

        let mut devices = Vec::new();
        for i in 0..device_count {
            let device = RocmDevice::new(i)?;
            devices.push(Arc::new(device));
        }

        Ok(Self {
            devices,
            default_device_id: 0,
        })
    }

    /// Get the default device
    pub fn default_device(&self) -> Option<&Arc<RocmDevice>> {
        self.devices.get(self.default_device_id)
    }

    /// Get device by ID
    pub fn device(&self, device_id: usize) -> Option<&Arc<RocmDevice>> {
        self.devices.get(device_id)
    }

    /// Get all devices
    pub fn devices(&self) -> &[Arc<RocmDevice>] {
        &self.devices
    }

    /// Get device count
    pub fn device_count(&self) -> usize {
        self.devices.len()
    }
}

/// Check if ROCm backend is available
pub fn is_available() -> bool {
    // Check for ROCm runtime availability
    // In real implementation, this would check for:
    // - libhip_hcc.so or libamdhip64.so
    // - ROCm installation in /opt/rocm
    // - HIP runtime initialization

    #[cfg(target_os = "linux")]
    {
        // Mock availability check - check for ROCm files
        std::path::Path::new("/opt/rocm").exists()
            || std::path::Path::new("/usr/lib/x86_64-linux-gnu/libhip_hcc.so").exists()
            || std::path::Path::new("/usr/lib/x86_64-linux-gnu/libamdhip64.so").exists()
    }

    #[cfg(not(target_os = "linux"))]
    {
        // ROCm is primarily supported on Linux
        false
    }
}

/// Get ROCm device count
pub fn device_count() -> Option<usize> {
    if !is_available() {
        return None;
    }

    // Mock device enumeration
    // In real implementation, this would call hipGetDeviceCount()

    // For testing purposes, return 1 if ROCm files are detected
    if is_available() {
        Some(1)
    } else {
        None
    }
}

/// Get device information for a specific device
pub fn get_device_info(device_id: usize) -> Result<RocmDeviceInfo, RocmError> {
    if !is_available() {
        return Err(RocmError::RuntimeNotAvailable);
    }

    // Mock device info retrieval
    // In real implementation, this would call:
    // - hipGetDeviceProperties()
    // - hipDeviceGetAttribute()

    match device_id {
        0 => Ok(RocmDeviceInfo {
            device_id,
            name: "AMD Radeon RX 7900 XTX".to_string(),
            compute_capability: (6, 0),            // gfx1030 equivalent
            total_memory: 24 * 1024 * 1024 * 1024, // 24GB
            multiprocessor_count: 96,
            warp_size: 64, // AMD wavefront size
            max_threads_per_block: 1024,
            is_integrated: false,
        }),
        _ => Err(RocmError::DeviceNotFound(device_id)),
    }
}

/// Enumerate all available ROCm devices
pub fn enumerate_devices() -> Result<Vec<RocmDeviceInfo>, RocmError> {
    let count = device_count().unwrap_or(0);
    let mut devices = Vec::new();

    for i in 0..count {
        devices.push(get_device_info(i)?);
    }

    Ok(devices)
}

/// Initialize ROCm runtime
pub fn initialize() -> Result<(), RocmError> {
    if !is_available() {
        return Err(RocmError::RuntimeNotAvailable);
    }

    // Mock initialization
    // In real implementation, this would call hipInit()
    Ok(())
}

/// Finalize ROCm runtime
pub fn finalize() -> Result<(), RocmError> {
    // Mock finalization
    // ROCm cleanup would happen here
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_availability_check() {
        // Test should not panic
        let _available = is_available();
    }

    #[test]
    fn test_device_count() {
        // Should return None or Some(count)
        let _count = device_count();
    }

    #[test]
    fn test_device_enumeration() {
        if is_available() {
            let devices = enumerate_devices();
            assert!(devices.is_ok() || devices.is_err());
        }
    }

    #[test]
    fn test_backend_creation() {
        if is_available() && device_count().unwrap_or(0) > 0 {
            let backend = RocmBackend::new();
            match backend {
                Ok(backend) => {
                    assert!(backend.device_count() > 0);
                    assert!(backend.default_device().is_some());
                }
                Err(_) => {
                    // Backend creation can fail in test environments
                }
            }
        }
    }
}
