cm-dashboard/agent/src/collectors/memory.rs

use async_trait::async_trait;
use cm_dashboard_shared::{registry, Metric, MetricValue, Status, StatusTracker, HysteresisThresholds};

use tracing::debug;

use super::{utils, Collector, CollectorError};
use crate::config::MemoryConfig;

/// Extremely efficient memory metrics collector
///
/// EFFICIENCY OPTIMIZATIONS:
/// - Single /proc/meminfo read for all memory metrics
/// - Minimal string parsing with split operations
/// - Pre-calculated KB to GB conversion
/// - No regex or complex parsing
/// - <0.1ms collection time target
pub struct MemoryCollector {
    name: String,
    usage_thresholds: HysteresisThresholds,
}

/// Memory information parsed from /proc/meminfo
#[derive(Debug, Default)]
struct MemoryInfo {
    total_kb: u64,
    available_kb: u64,
    free_kb: u64,
    buffers_kb: u64,
    cached_kb: u64,
    swap_total_kb: u64,
    swap_free_kb: u64,
}

impl MemoryCollector {
    pub fn new(config: MemoryConfig) -> Self {
        // Create hysteresis thresholds with 5% gap for memory usage
        let usage_thresholds = HysteresisThresholds::with_custom_gaps(
            config.usage_warning_percent,
            5.0, // 5% gap for warning recovery
            config.usage_critical_percent,
            5.0, // 5% gap for critical recovery
        );
        
        Self {
            name: "memory".to_string(),
            usage_thresholds,
        }
    }

    /// Calculate memory usage status using hysteresis thresholds
    fn calculate_usage_status(&self, metric_name: &str, usage_percent: f32, status_tracker: &mut StatusTracker) -> Status {
        status_tracker.calculate_with_hysteresis(metric_name, usage_percent, &self.usage_thresholds)
    }

    /// Parse /proc/meminfo efficiently
    /// Format: "MemTotal:       16384000 kB"
    async fn parse_meminfo(&self) -> Result<MemoryInfo, CollectorError> {
        let content = utils::read_proc_file("/proc/meminfo")?;
        let mut info = MemoryInfo::default();

        // Parse each line efficiently - only extract what we need
        for line in content.lines() {
            if let Some(colon_pos) = line.find(':') {
                let key = &line[..colon_pos];
                let value_part = &line[colon_pos + 1..];

                // Extract number from value part (format: "    12345 kB")
                if let Some(number_str) = value_part.split_whitespace().next() {
                    if let Ok(value_kb) = utils::parse_u64(number_str) {
                        match key {
                            "MemTotal" => info.total_kb = value_kb,
                            "MemAvailable" => info.available_kb = value_kb,
                            "MemFree" => info.free_kb = value_kb,
                            "Buffers" => info.buffers_kb = value_kb,
                            "Cached" => info.cached_kb = value_kb,
                            "SwapTotal" => info.swap_total_kb = value_kb,
                            "SwapFree" => info.swap_free_kb = value_kb,
                            _ => {} // Skip other fields for efficiency
                        }
                    }
                }
            }
        }

        // Validate that we got essential fields
        if info.total_kb == 0 {
            return Err(CollectorError::Parse {
                value: "MemTotal".to_string(),
                error: "MemTotal not found or zero in /proc/meminfo".to_string(),
            });
        }

        // If MemAvailable is not available (older kernels), calculate it
        if info.available_kb == 0 {
            info.available_kb = info.free_kb + info.buffers_kb + info.cached_kb;
        }

        Ok(info)
    }

    /// Convert KB to GB efficiently (avoiding floating point in hot path)
    fn kb_to_gb(kb: u64) -> f32 {
        kb as f32 / 1_048_576.0 // 1024 * 1024
    }

    /// Calculate memory metrics from parsed info
    fn calculate_metrics(&self, info: &MemoryInfo, status_tracker: &mut StatusTracker) -> Vec<Metric> {
        let mut metrics = Vec::with_capacity(6);

        // Calculate derived values
        let used_kb = info.total_kb - info.available_kb;
        let usage_percent = (used_kb as f32 / info.total_kb as f32) * 100.0;
        let usage_status = self.calculate_usage_status(registry::MEMORY_USAGE_PERCENT, usage_percent, status_tracker);

        let swap_used_kb = info.swap_total_kb - info.swap_free_kb;

        // Convert to GB for metrics
        let total_gb = Self::kb_to_gb(info.total_kb);
        let used_gb = Self::kb_to_gb(used_kb);
        let available_gb = Self::kb_to_gb(info.available_kb);
        let swap_total_gb = Self::kb_to_gb(info.swap_total_kb);
        let swap_used_gb = Self::kb_to_gb(swap_used_kb);

        // Memory usage percentage (primary metric with status)
        metrics.push(
            Metric::new(
                registry::MEMORY_USAGE_PERCENT.to_string(),
                MetricValue::Float(usage_percent),
                usage_status,
            )
            .with_description("Memory usage percentage".to_string())
            .with_unit("%".to_string()),
        );

        // Total memory
        metrics.push(
            Metric::new(
                registry::MEMORY_TOTAL_GB.to_string(),
                MetricValue::Float(total_gb),
                Status::Ok, // Total memory doesn't have status
            )
            .with_description("Total system memory".to_string())
            .with_unit("GB".to_string()),
        );

        // Used memory
        metrics.push(
            Metric::new(
                registry::MEMORY_USED_GB.to_string(),
                MetricValue::Float(used_gb),
                Status::Ok, // Used memory absolute value doesn't have status
            )
            .with_description("Used system memory".to_string())
            .with_unit("GB".to_string()),
        );

        // Available memory
        metrics.push(
            Metric::new(
                registry::MEMORY_AVAILABLE_GB.to_string(),
                MetricValue::Float(available_gb),
                Status::Ok, // Available memory absolute value doesn't have status
            )
            .with_description("Available system memory".to_string())
            .with_unit("GB".to_string()),
        );

        // Swap metrics (only if swap exists)
        if info.swap_total_kb > 0 {
            metrics.push(
                Metric::new(
                    registry::MEMORY_SWAP_TOTAL_GB.to_string(),
                    MetricValue::Float(swap_total_gb),
                    Status::Ok,
                )
                .with_description("Total swap space".to_string())
                .with_unit("GB".to_string()),
            );

            metrics.push(
                Metric::new(
                    registry::MEMORY_SWAP_USED_GB.to_string(),
                    MetricValue::Float(swap_used_gb),
                    Status::Ok,
                )
                .with_description("Used swap space".to_string())
                .with_unit("GB".to_string()),
            );
        }

        // Monitor tmpfs (/tmp) usage
        if let Ok(tmpfs_metrics) = self.get_tmpfs_metrics() {
            metrics.extend(tmpfs_metrics);
        }

        metrics
    }

    /// Get tmpfs (/tmp) usage metrics  
    fn get_tmpfs_metrics(&self) -> Result<Vec<Metric>, CollectorError> {
        use std::process::Command;
        
        let output = Command::new("df")
            .arg("--block-size=1")
            .arg("/tmp")
            .output()
            .map_err(|e| CollectorError::SystemRead {
                path: "/tmp".to_string(),
                error: e.to_string(),
            })?;

        if !output.status.success() {
            return Ok(Vec::new()); // Return empty if /tmp not available
        }

        let output_str = String::from_utf8(output.stdout)
            .map_err(|e| CollectorError::Parse {
                value: "df output".to_string(),
                error: e.to_string(),
            })?;

        let lines: Vec<&str> = output_str.lines().collect();
        if lines.len() < 2 {
            return Ok(Vec::new());
        }

        let fields: Vec<&str> = lines[1].split_whitespace().collect();
        if fields.len() < 4 {
            return Ok(Vec::new());
        }

        let total_bytes: u64 = fields[1].parse()
            .map_err(|e: std::num::ParseIntError| CollectorError::Parse {
                value: fields[1].to_string(),
                error: e.to_string(),
            })?;
        let used_bytes: u64 = fields[2].parse()
            .map_err(|e: std::num::ParseIntError| CollectorError::Parse {
                value: fields[2].to_string(),
                error: e.to_string(),
            })?;

        let total_gb = total_bytes as f32 / (1024.0 * 1024.0 * 1024.0);
        let used_gb = used_bytes as f32 / (1024.0 * 1024.0 * 1024.0);
        let usage_percent = if total_bytes > 0 {
            (used_bytes as f32 / total_bytes as f32) * 100.0
        } else {
            0.0
        };

        let mut metrics = Vec::new();
        let timestamp = chrono::Utc::now().timestamp() as u64;

        metrics.push(Metric {
            name: "memory_tmp_usage_percent".to_string(),
            value: MetricValue::Float(usage_percent),
            unit: Some("%".to_string()),
            description: Some("tmpfs /tmp usage percentage".to_string()),
            status: Status::Ok,
            timestamp,
        });

        metrics.push(Metric {
            name: "memory_tmp_used_gb".to_string(),
            value: MetricValue::Float(used_gb),
            unit: Some("GB".to_string()),
            description: Some("tmpfs /tmp used space".to_string()),
            status: Status::Ok,
            timestamp,
        });

        metrics.push(Metric {
            name: "memory_tmp_total_gb".to_string(),
            value: MetricValue::Float(total_gb),
            unit: Some("GB".to_string()),
            description: Some("tmpfs /tmp total space".to_string()),
            status: Status::Ok,
            timestamp,
        });

        Ok(metrics)
    }
}

#[async_trait]
impl Collector for MemoryCollector {
    fn name(&self) -> &str {
        &self.name
    }

    async fn collect(&self, status_tracker: &mut StatusTracker) -> Result<Vec<Metric>, CollectorError> {
        debug!("Collecting memory metrics");
        let start = std::time::Instant::now();

        // Parse memory info from /proc/meminfo
        let info = self.parse_meminfo().await?;

        // Calculate all metrics from parsed info
        let metrics = self.calculate_metrics(&info, status_tracker);

        let duration = start.elapsed();
        debug!(
            "Memory collection completed in {:?} with {} metrics",
            duration,
            metrics.len()
        );

        // Efficiency check: warn if collection takes too long
        if duration.as_millis() > 1 {
            debug!(
                "Memory collection took {}ms - consider optimization",
                duration.as_millis()
            );
        }

        // Store performance metrics
        // Performance tracking handled by cache system

        Ok(metrics)
    }

}