use std::fs;
use std::path::{Path, PathBuf};
use std::time::{Duration};
use std::thread;
use std::sync::mpsc;
use std::collections::HashMap;
use crate::sal::heuristic::schema::{SensorDiscovery, ActuatorDiscovery, Conflict, Discovery, Benchmarking};
use crate::sys::SyscallRunner;
use tracing::{debug, warn, info};

/// Registry of dynamically discovered paths for configs and tools.
#[derive(Debug, Clone, Default)]
pub struct PathRegistry {
    pub configs: HashMap<String, PathBuf>,
    pub tools: HashMap<String, PathBuf>,
}

/// Strongly-typed findings about the current system.
#[derive(Debug, Clone, Default)]
pub struct SystemFactSheet {
    pub vendor: String,
    pub model: String,
    pub temp_path: Option<PathBuf>,
    pub fan_paths: Vec<PathBuf>,
    pub rapl_paths: Vec<PathBuf>,
    pub active_conflicts: Vec<String>,
    pub conflict_services: Vec<String>,
    pub paths: PathRegistry,
    pub bench_config: Option<Benchmarking>,
}

/// Probes the system for hardware sensors, actuators, service conflicts, and paths.
pub fn discover_facts(
    base_path: &Path,
    runner: &dyn SyscallRunner,
    discovery: &Discovery,
    conflicts: &[Conflict],
    bench_config: Benchmarking,
) -> SystemFactSheet {
    let (vendor, model) = read_dmi_info(base_path);
    
    debug!("DMI Identity: Vendor='{}', Model='{}'", vendor, model);

    let (temp_path, fan_paths) = discover_hwmon(base_path, &discovery.sensors);
    let rapl_paths = discover_rapl(base_path, &discovery.actuators);
    
    let mut active_conflicts = Vec::new();
    let mut conflict_services = Vec::new();
    for conflict in conflicts {
        let mut found_active = false;
        for service in &conflict.services {
            if is_service_active(runner, service) {
                if !found_active {
                    debug!("Detected active conflict: {} (Service: {})", conflict.id, service);
                    active_conflicts.push(conflict.id.clone());
                    found_active = true;
                }
                conflict_services.push(service.clone());
            }
        }
    }

    let paths = discover_paths(base_path, discovery);

    SystemFactSheet {
        vendor, model, temp_path, fan_paths, rapl_paths, active_conflicts, conflict_services, paths,
        bench_config: Some(bench_config),
    }
}

fn discover_paths(base_path: &Path, discovery: &Discovery) -> PathRegistry {
    let mut registry = PathRegistry::default();

    for (id, binary_name) in &discovery.tools {
        if let Ok(path) = which::which(binary_name) {
            debug!("Discovered tool: {} -> {:?}", id, path);
            registry.tools.insert(id.clone(), path);
        }
    }

    for (id, candidates) in &discovery.configs {
        for candidate in candidates {
            let path = if candidate.starts_with('/') {
                base_path.join(&candidate[1..])
            } else {
                base_path.join(candidate)
            };
            
            if path.exists() {
                debug!("Discovered config: {} -> {:?}", id, path);
                registry.configs.insert(id.clone(), path);
                break;
            }
        }
        if !registry.configs.contains_key(id) {
            if let Some(first) = candidates.first() {
                registry.configs.insert(id.clone(), PathBuf::from(first));
            }
        }
    }

    registry
}

fn read_dmi_info(base_path: &Path) -> (String, String) {
    let vendor = fs::read_to_string(base_path.join("sys/class/dmi/id/sys_vendor"))
        .map(|s| s.trim().to_string()).unwrap_or_else(|_| "Unknown".to_string());
    let model = fs::read_to_string(base_path.join("sys/class/dmi/id/product_name"))
        .map(|s| s.trim().to_string()).unwrap_or_else(|_| "Unknown".to_string());
    (vendor, model)
}

/// Discovers hwmon sensors by matching labels and prioritizing drivers.
fn discover_hwmon(base_path: &Path, cfg: &SensorDiscovery) -> (Option<PathBuf>, Vec<PathBuf>) {
    let mut temp_candidates = Vec::new();
    let mut fan_candidates = Vec::new();

    let hwmon_base = base_path.join("sys/class/hwmon");
    let entries = fs::read_dir(&hwmon_base).map_err(|e| {
        warn!("Could not read {:?}: {}", hwmon_base, e);
        e
    }).ok();

    if let Some(entries) = entries {
        for entry in entries.flatten() {
            let hwmon_path = entry.path();
            
            // # SAFETY: Read driver name directly. This file is virtual and never blocks.
            // Using a timeout wrapper here was causing discovery to fail if the thread-pool lagged.
            let driver_name = fs::read_to_string(hwmon_path.join("name"))
                .map(|s| s.trim().to_string()).unwrap_or_default();

            let priority = cfg.hwmon_priority
                .iter()
                .position(|p| driver_name.contains(p))
                .unwrap_or(usize::MAX);

            if let Ok(hw_entries) = fs::read_dir(&hwmon_path) {
                for hw_entry in hw_entries.flatten() {
                    let file_name = hw_entry.file_name().into_string().unwrap_or_default();
                    
                    // 1. Temperatures
                    if file_name.starts_with("temp") && file_name.ends_with("_label") {
                        if let Some(label) = read_sysfs_with_timeout(&hw_entry.path(), Duration::from_millis(500)) {
                            if cfg.temp_labels.iter().any(|l| label.contains(l)) {
                                let input_path = hwmon_path.join(file_name.replace("_label", "_input"));
                                if input_path.exists() {
                                    temp_candidates.push((priority, input_path));
                                }
                            }
                        }
                    }

                    // 2. Fans (Label Match)
                    if file_name.starts_with("fan") && file_name.ends_with("_label") {
                        if let Some(label) = read_sysfs_with_timeout(&hw_entry.path(), Duration::from_millis(500)) {
                            if cfg.fan_labels.iter().any(|l| label.contains(l)) {
                                let input_path = hwmon_path.join(file_name.replace("_label", "_input"));
                                if input_path.exists() {
                                    debug!("Discovered fan by label: {:?} (priority {})", input_path, priority);
                                    fan_candidates.push((priority, input_path));
                                }
                            }
                        }
                    }

                    // 3. Fans (Priority Fallback - CRITICAL FOR DELL 9380)
                    // If we found a priority driver (e.g., dell_smm), we take every fan*_input we find.
                    if priority < usize::MAX && file_name.starts_with("fan") && file_name.ends_with("_input") {
                        if !fan_candidates.iter().any(|(_, p)| p == &hw_entry.path()) {
                            info!("Heuristic Discovery: Force-adding unlabeled fan sensor from priority driver '{}': {:?}", driver_name, hw_entry.path());
                            fan_candidates.push((priority, hw_entry.path()));
                        }
                    }
                }
            }
        }
    }

    temp_candidates.sort_by_key(|(p, _)| *p);
    fan_candidates.sort_by_key(|(p, _)| *p);

    let best_temp = temp_candidates.first().map(|(_, p)| p.clone());
    let best_fans: Vec<PathBuf> = fan_candidates.into_iter().map(|(_, p)| p).collect();

    if best_fans.is_empty() {
        warn!("Heuristic Discovery: No fan RPM sensors found.");
    } else {
        info!("Heuristic Discovery: Final registry contains {} fan sensors.", best_fans.len());
    }

    (best_temp, best_fans)
}

fn discover_rapl(base_path: &Path, cfg: &ActuatorDiscovery) -> Vec<PathBuf> {
    let mut paths = Vec::new();
    let powercap_base = base_path.join("sys/class/powercap");
    
    if let Ok(entries) = fs::read_dir(&powercap_base) {
        for entry in entries.flatten() {
            let path = entry.path();
            let dir_name = entry.file_name().into_string().unwrap_or_default();
            
            if cfg.rapl_paths.contains(&dir_name) {
                paths.push(path);
                continue;
            }

            if let Ok(name) = fs::read_to_string(path.join("name")) {
                if cfg.rapl_paths.iter().any(|p| p == name.trim()) {
                    paths.push(path);
                }
            }
        }
    }
    paths
}

pub fn is_service_active(runner: &dyn SyscallRunner, service: &str) -> bool {
    runner.run("systemctl", &["is-active", "--quiet", service]).is_ok()
}

fn read_sysfs_with_timeout(path: &Path, timeout: Duration) -> Option<String> {
    let (tx, rx) = mpsc::channel();
    let path_buf = path.to_path_buf();
    
    thread::spawn(move || {
        let res = fs::read_to_string(path_buf).map(|s| s.trim().to_string());
        let _ = tx.send(res);
    });

    match rx.recv_timeout(timeout) {
        Ok(Ok(content)) => Some(content),
        _ => None,
    }
}