use anyhow::{Result, Context};
use serde::{Deserialize, Serialize};
use sha2::{Sha256, Digest};
use std::fs;
use std::process::Command;
use sysinfo::{System, Disks, Networks, Components};
use mac_address::get_mac_address;
use tracing::{info, warn, error, debug};

/// Hardware fingerprint containing unique device identifiers
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HardwareFingerprint {
    pub cpu_id: String,
    pub board_serial: String,
    pub mac_addresses: Vec<String>,
    pub disk_uuid: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub tpm_attestation: Option<String>,
    pub system_info: SystemInfo,
    pub computed_hash: String,
}

/// Additional system information for device registration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SystemInfo {
    pub hostname: String,
    pub os_name: String,
    pub os_version: String,
    pub kernel_version: String,
    pub architecture: String,
    pub total_memory: u64,
    pub available_memory: u64,
    pub cpu_count: usize,
    pub cpu_brand: String,
    pub disk_info: Vec<DiskInfo>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DiskInfo {
    pub name: String,
    pub mount_point: String,
    pub total_space: u64,
    pub available_space: u64,
    pub file_system: String,
}

/// Hardware fingerprinting service
pub struct HardwareFingerprintService {
    system: System,
    cache: Option<HardwareFingerprint>,
}

impl HardwareFingerprintService {
    /// Creates a new hardware fingerprinting service
    pub fn new() -> Self {
        let system = System::new_all();
        
        Self {
            system,
            cache: None,
        }
    }

    /// Generates a complete hardware fingerprint
    pub async fn generate_fingerprint(&mut self) -> Result<HardwareFingerprint> {
        // Check cache first
        if let Some(cached) = &self.cache {
            debug!("Returning cached hardware fingerprint");
            return Ok(cached.clone());
        }

        info!("Generating hardware fingerprint...");

        // Refresh system information
        // In sysinfo 0.30, System is immutable after creation

        let cpu_id = self.get_cpu_id().await?;
        let board_serial = self.get_board_serial().await?;
        let mac_addresses = self.get_mac_addresses().await?;
        let disk_uuid = self.get_primary_disk_uuid().await?;
        let tpm_attestation = self.get_tpm_attestation().await.ok();
        let system_info = self.collect_system_info().await?;

        // Compute hash from core identifiers
        let computed_hash = self.compute_fingerprint_hash(&cpu_id, &board_serial, &mac_addresses, &disk_uuid);

        let fingerprint = HardwareFingerprint {
            cpu_id,
            board_serial,
            mac_addresses,
            disk_uuid,
            tpm_attestation: tpm_attestation,
            system_info,
            computed_hash,
        };

        // Cache the result
        self.cache = Some(fingerprint.clone());
        
        info!("Hardware fingerprint generated successfully");
        debug!("Fingerprint hash: {}", fingerprint.computed_hash);

        Ok(fingerprint)
    }

    /// Gets CPU identifier
    async fn get_cpu_id(&self) -> Result<String> {
        // Try multiple approaches to get a stable CPU identifier
        
        // Method 1: Try /proc/cpuinfo on Linux
        #[cfg(target_os = "linux")]
        {
            if let Ok(cpuinfo) = fs::read_to_string("/proc/cpuinfo") {
                for line in cpuinfo.lines() {
                    if line.starts_with("Serial") {
                        if let Some(serial) = line.split(':').nth(1) {
                            let serial = serial.trim();
                            if !serial.is_empty() && serial != "0000000000000000" {
                                return Ok(serial.to_string());
                            }
                        }
                    }
                }
            }
        }

        // Method 2: Try system UUID on Linux
        #[cfg(target_os = "linux")]
        {
            if let Ok(machine_id) = fs::read_to_string("/etc/machine-id") {
                let machine_id = machine_id.trim();
                if !machine_id.is_empty() {
                    return Ok(format!("machine-{}", machine_id));
                }
            }
        }

        // Method 3: macOS system_profiler
        #[cfg(target_os = "macos")]
        {
            if let Ok(output) = Command::new("system_profiler")
                .args(&["SPHardwareDataType"])
                .output() {
                let output_str = String::from_utf8_lossy(&output.stdout);
                for line in output_str.lines() {
                    if line.contains("Hardware UUID:") {
                        if let Some(uuid) = line.split(':').nth(1) {
                            return Ok(format!("hw-{}", uuid.trim()));
                        }
                    }
                }
            }
        }

        // Method 4: Windows registry
        #[cfg(target_os = "windows")]
        {
            if let Ok(output) = Command::new("wmic")
                .args(&["csproduct", "get", "UUID", "/value"])
                .output() {
                let output_str = String::from_utf8_lossy(&output.stdout);
                for line in output_str.lines() {
                    if line.starts_with("UUID=") {
                        let uuid = line.replace("UUID=", "").trim().to_string();
                        if !uuid.is_empty() && uuid != "FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF" {
                            return Ok(format!("sys-{}", uuid));
                        }
                    }
                }
            }
        }

        // Fallback: Use system information
        let hostname = hostname::get()
            .context("Failed to get hostname")?
            .to_string_lossy()
            .to_string();

        let cpu_info = format!("{}-{}", hostname, "generic-cpu");
        let hash = Sha256::digest(cpu_info.as_bytes());
        Ok(format!("cpu-{}", hex::encode(&hash[..8])))
    }

    /// Gets board serial number
    async fn get_board_serial(&self) -> Result<String> {
        // Method 1: DMI information on Linux
        #[cfg(target_os = "linux")]
        {
            if let Ok(serial) = fs::read_to_string("/sys/devices/virtual/dmi/id/board_serial") {
                let serial = serial.trim();
                if !serial.is_empty() && serial != "To be filled by O.E.M." {
                    return Ok(serial.to_string());
                }
            }
            
            if let Ok(serial) = fs::read_to_string("/sys/devices/virtual/dmi/id/product_serial") {
                let serial = serial.trim();
                if !serial.is_empty() && serial != "To be filled by O.E.M." {
                    return Ok(serial.to_string());
                }
            }
        }

        // Method 2: macOS system_profiler
        #[cfg(target_os = "macos")]
        {
            if let Ok(output) = Command::new("system_profiler")
                .args(&["SPHardwareDataType"])
                .output() {
                let output_str = String::from_utf8_lossy(&output.stdout);
                for line in output_str.lines() {
                    if line.contains("Serial Number (system):") {
                        if let Some(serial) = line.split(':').nth(1) {
                            return Ok(serial.trim().to_string());
                        }
                    }
                }
            }
        }

        // Method 3: Windows WMI
        #[cfg(target_os = "windows")]
        {
            if let Ok(output) = Command::new("wmic")
                .args(&["baseboard", "get", "SerialNumber", "/value"])
                .output() {
                let output_str = String::from_utf8_lossy(&output.stdout);
                for line in output_str.lines() {
                    if line.starts_with("SerialNumber=") {
                        let serial = line.replace("SerialNumber=", "").trim().to_string();
                        if !serial.is_empty() && serial != "To be filled by O.E.M." {
                            return Ok(serial);
                        }
                    }
                }
            }
        }

        // Fallback: Generate from system info
        let fallback_data = format!("board-{}-{}", 
            System::name().unwrap_or("unknown".to_string()),
            System::kernel_version().unwrap_or("unknown".to_string()));
        let hash = Sha256::digest(fallback_data.as_bytes());
        Ok(format!("board-{}", hex::encode(&hash[..8])))
    }

    /// Gets all MAC addresses
    async fn get_mac_addresses(&self) -> Result<Vec<String>> {
        let mut mac_addresses = Vec::new();

        // Get primary MAC address
        if let Ok(Some(mac)) = get_mac_address() {
            mac_addresses.push(format!("{:02X}:{:02X}:{:02X}:{:02X}:{:02X}:{:02X}",
                mac.bytes()[0], mac.bytes()[1], mac.bytes()[2],
                mac.bytes()[3], mac.bytes()[4], mac.bytes()[5]));
        }

        // Try to get additional MAC addresses
        #[cfg(target_os = "linux")]
        {
            if let Ok(entries) = fs::read_dir("/sys/class/net") {
                for entry in entries.flatten() {
                    let interface_name = entry.file_name().to_string_lossy().to_string();
                    if interface_name.starts_with("lo") || interface_name.starts_with("docker") {
                        continue; // Skip loopback and docker interfaces
                    }

                    let mac_path = format!("/sys/class/net/{}/address", interface_name);
                    if let Ok(mac_str) = fs::read_to_string(&mac_path) {
                        let mac_str = mac_str.trim().to_uppercase();
                        if mac_str != "00:00:00:00:00:00" && !mac_addresses.contains(&mac_str) {
                            mac_addresses.push(mac_str);
                        }
                    }
                }
            }
        }

        if mac_addresses.is_empty() {
            return Err(anyhow::anyhow!("No valid MAC addresses found"));
        }

        // Sort for consistency
        mac_addresses.sort();
        Ok(mac_addresses)
    }

    /// Gets primary disk UUID
    async fn get_primary_disk_uuid(&self) -> Result<String> {
        // Method 1: Linux filesystem UUIDs
        #[cfg(target_os = "linux")]
        {
            // Try to get root filesystem UUID
            if let Ok(fstab) = fs::read_to_string("/etc/fstab") {
                for line in fstab.lines() {
                    let line = line.trim();
                    if line.starts_with("UUID=") && (line.contains(" / ") || line.contains("\t/\t")) {
                        if let Some(uuid) = line.split_whitespace().next() {
                            let uuid = uuid.replace("UUID=", "");
                            if !uuid.is_empty() {
                                return Ok(uuid);
                            }
                        }
                    }
                }
            }

            // Try blkid command
            if let Ok(output) = Command::new("blkid")
                .args(&["-s", "UUID", "-o", "value", "/dev/sda1"])
                .output() {
                let uuid = String::from_utf8_lossy(&output.stdout).trim().to_string();
                if !uuid.is_empty() {
                    return Ok(uuid);
                }
            }
        }

        // Method 2: macOS diskutil
        #[cfg(target_os = "macos")]
        {
            if let Ok(output) = Command::new("diskutil")
                .args(&["info", "/"])
                .output() {
                let output_str = String::from_utf8_lossy(&output.stdout);
                for line in output_str.lines() {
                    if line.contains("Volume UUID:") {
                        if let Some(uuid) = line.split(':').nth(1) {
                            return Ok(uuid.trim().to_string());
                        }
                    }
                }
            }
        }

        // Method 3: Windows WMI
        #[cfg(target_os = "windows")]
        {
            if let Ok(output) = Command::new("wmic")
                .args(&["logicaldisk", "where", "caption=\"C:\"", "get", "VolumeSerialNumber", "/value"])
                .output() {
                let output_str = String::from_utf8_lossy(&output.stdout);
                for line in output_str.lines() {
                    if line.starts_with("VolumeSerialNumber=") {
                        let serial = line.replace("VolumeSerialNumber=", "").trim().to_string();
                        if !serial.is_empty() {
                            return Ok(format!("vol-{}", serial));
                        }
                    }
                }
            }
        }

        // Fallback: Use disk information from system
        let disks = Disks::new_with_refreshed_list();
        if let Some(disk) = disks.first() {
            let disk_name = disk.name().to_string_lossy();
            let mount_point = disk.mount_point().to_string_lossy();
            let fallback_data = format!("disk-{}-{}", disk_name, mount_point);
            let hash = Sha256::digest(fallback_data.as_bytes());
            Ok(format!("disk-{}", hex::encode(&hash[..8])))
        } else {
            Err(anyhow::anyhow!("No disk information available"))
        }
    }

    /// Gets TPM attestation (if available)
    async fn get_tpm_attestation(&self) -> Result<String> {
        // This is a placeholder for TPM 2.0 attestation
        // In a production system, this would:
        // 1. Check if TPM 2.0 is available
        // 2. Generate an attestation quote
        // 3. Include PCR values and attestation identity key
        // 4. Return base64-encoded attestation data

        #[cfg(target_os = "linux")]
        {
            // Check if TPM is available
            if fs::metadata("/dev/tpm0").is_ok() || fs::metadata("/dev/tpmrm0").is_ok() {
                // For demonstration, return a mock attestation
                // In production, use tss-esapi crate or similar TPM library
                let mock_attestation = format!("tpm2-mock-{}", 
                    hex::encode(Sha256::digest("mock-tpm-attestation".as_bytes())));
                return Ok(base64::encode(mock_attestation));
            }
        }

        #[cfg(target_os = "windows")]
        {
            // Check Windows TPM
            if let Ok(output) = Command::new("powershell")
                .args(&["-Command", "Get-Tpm"])
                .output() {
                let output_str = String::from_utf8_lossy(&output.stdout);
                if output_str.contains("TpmPresent") && output_str.contains("True") {
                    let mock_attestation = format!("tpm2-win-{}", 
                        hex::encode(Sha256::digest("windows-tpm-attestation".as_bytes())));
                    return Ok(base64::encode(mock_attestation));
                }
            }
        }

        Err(anyhow::anyhow!("TPM not available or not accessible"))
    }

    /// Collects additional system information
    async fn collect_system_info(&self) -> Result<SystemInfo> {
        let hostname = hostname::get()
            .context("Failed to get hostname")?
            .to_string_lossy()
            .to_string();

        let os_name = System::name().unwrap_or("Unknown".to_string());
        let os_version = System::os_version().unwrap_or("Unknown".to_string());
        let kernel_version = System::kernel_version().unwrap_or("Unknown".to_string());
        
        let architecture = if cfg!(target_arch = "x86_64") {
            "x86_64"
        } else if cfg!(target_arch = "aarch64") {
            "aarch64"
        } else if cfg!(target_arch = "arm") {
            "arm"
        } else {
            "unknown"
        }.to_string();

        let total_memory = self.system.total_memory();
        let available_memory = self.system.available_memory();
        let cpu_count = num_cpus::get();
        let cpu_brand = "Generic CPU".to_string();

        let disks = Disks::new_with_refreshed_list();
        let disk_info = disks
            .iter()
            .map(|disk| DiskInfo {
                name: disk.name().to_string_lossy().to_string(),
                mount_point: disk.mount_point().to_string_lossy().to_string(),
                total_space: disk.total_space(),
                available_space: disk.available_space(),
                file_system: disk.file_system().to_string_lossy().to_string(),
            })
            .collect();

        Ok(SystemInfo {
            hostname,
            os_name,
            os_version,
            kernel_version,
            architecture,
            total_memory,
            available_memory,
            cpu_count,
            cpu_brand,
            disk_info,
        })
    }

    /// Computes fingerprint hash from core identifiers
    fn compute_fingerprint_hash(&self, cpu_id: &str, board_serial: &str, mac_addresses: &[String], disk_uuid: &str) -> String {
        let mut hasher = Sha256::new();
        hasher.update(cpu_id);
        hasher.update(board_serial);
        for mac in mac_addresses {
            hasher.update(mac);
        }
        hasher.update(disk_uuid);
        hex::encode(hasher.finalize())
    }

    /// Validates fingerprint integrity
    pub fn validate_fingerprint(&self, fingerprint: &HardwareFingerprint) -> Result<bool> {
        let expected_hash = self.compute_fingerprint_hash(
            &fingerprint.cpu_id,
            &fingerprint.board_serial,
            &fingerprint.mac_addresses,
            &fingerprint.disk_uuid,
        );

        Ok(expected_hash == fingerprint.computed_hash)
    }
}

impl Default for HardwareFingerprintService {
    fn default() -> Self {
        Self::new()
    }
}

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

    #[tokio::test]
    async fn test_fingerprint_generation() {
        let mut service = HardwareFingerprintService::new();
        let fingerprint = service.generate_fingerprint().await.unwrap();
        
        assert!(!fingerprint.cpu_id.is_empty());
        assert!(!fingerprint.board_serial.is_empty());
        assert!(!fingerprint.mac_addresses.is_empty());
        assert!(!fingerprint.disk_uuid.is_empty());
        assert!(!fingerprint.computed_hash.is_empty());
        assert_eq!(fingerprint.computed_hash.len(), 64); // SHA256 hex length
    }

    #[tokio::test]
    async fn test_fingerprint_consistency() {
        let mut service = HardwareFingerprintService::new();
        let fingerprint1 = service.generate_fingerprint().await.unwrap();
        let fingerprint2 = service.generate_fingerprint().await.unwrap();
        
        // Should be identical (cached)
        assert_eq!(fingerprint1.computed_hash, fingerprint2.computed_hash);
    }

    #[tokio::test]
    async fn test_fingerprint_validation() {
        let mut service = HardwareFingerprintService::new();
        let fingerprint = service.generate_fingerprint().await.unwrap();
        
        assert!(service.validate_fingerprint(&fingerprint).unwrap());
        
        // Test with modified fingerprint
        let mut invalid_fingerprint = fingerprint.clone();
        invalid_fingerprint.cpu_id = "modified".to_string();
        
        assert!(!service.validate_fingerprint(&invalid_fingerprint).unwrap());
    }
}