#!/usr/bin/env bash
# Background metric collector — samples GPU and system stats to CSV
set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
source "$SCRIPT_DIR/../../lib/common.sh"
source "$SCRIPT_DIR/../../lib/detect.sh"

INTERVAL=2
OUTPUT=""
DURATION=0  # 0 = indefinite

while [[ $# -gt 0 ]]; do
    case "$1" in
        --output|-o)  OUTPUT="$2"; shift 2 ;;
        --interval|-i) INTERVAL="$2"; shift 2 ;;
        --duration|-d) DURATION="$2"; shift 2 ;;
        --help|-h)
            echo "Usage: log-metrics.sh [--output FILE] [--interval SECS] [--duration SECS]"
            exit 0 ;;
        *) log_warn "Unknown argument: $1"; shift ;;
    esac
done

# Validate numeric args
[[ "$INTERVAL" =~ ^[0-9]+$ ]] || { log_error "--interval must be a positive integer"; exit 1; }
[[ "$DURATION" =~ ^[0-9]+$ ]] || { log_error "--duration must be a positive integer"; exit 1; }

if [[ -z "$OUTPUT" ]]; then
    OUTPUT="$(data_dir logs)/metrics-$(timestamp).csv"
fi

mkdir -p "$(dirname "$OUTPUT")"

# Cache sysfs paths once (avoid re-globbing every iteration)
SYSFS_GPU_BUSY="$GPU_SYSFS/gpu_busy_percent"
SYSFS_VRAM_USED="$GPU_SYSFS/mem_info_vram_used"
SYSFS_GTT_USED="$GPU_SYSFS/mem_info_gtt_used"
SYSFS_TEMP=""
SYSFS_POWER=""
for f in "$GPU_SYSFS"/hwmon/hwmon*/temp1_input; do
    [[ -f "$f" ]] && SYSFS_TEMP="$f" && break
done
for f in "$GPU_SYSFS"/hwmon/hwmon*/power1_average; do
    [[ -f "$f" ]] && SYSFS_POWER="$f" && break
done

# Write CSV header
echo "timestamp,gpu_busy_pct,vram_used_mib,gtt_used_mib,gpu_temp_c,gpu_power_w,cpu_pct,ram_used_mib" > "$OUTPUT"

log_info "Logging metrics every ${INTERVAL}s → $OUTPUT"
[[ $DURATION -gt 0 ]] && log_info "Will stop after ${DURATION}s"

start_time=$SECONDS
stopped=false

cleanup() {
    $stopped && return
    stopped=true
    local lines
    lines=$(( $(wc -l < "$OUTPUT") - 1 ))
    log_info "Metric logger stopped. $lines samples in $OUTPUT"
}
trap cleanup EXIT

# Read /proc/stat fields into variables using bash builtins
read_cpu_stat() {
    local line
    read -r line < /proc/stat
    # "cpu  user nice system idle iowait irq softirq steal"
    set -- $line
    shift  # drop "cpu"
    CPU_TOTAL=$(( $1 + $2 + $3 + $4 + $5 + $6 + $7 + ${8:-0} ))
    CPU_IDLE=$4
}

while true; do
    ts="$(printf '%(%Y-%m-%d %H:%M:%S)T' -1)"

    # GPU metrics — direct reads, no subshells
    read -r gpu_busy < "$SYSFS_GPU_BUSY" 2>/dev/null || gpu_busy=0
    read -r vram_bytes < "$SYSFS_VRAM_USED" 2>/dev/null || vram_bytes=0
    read -r gtt_bytes < "$SYSFS_GTT_USED" 2>/dev/null || gtt_bytes=0
    read -r temp_mc < "$SYSFS_TEMP" 2>/dev/null || temp_mc=0
    read -r power_uw < "$SYSFS_POWER" 2>/dev/null || power_uw=0

    vram_mib=$(( vram_bytes / 1048576 ))
    gtt_mib=$(( gtt_bytes / 1048576 ))
    gpu_temp_c=$(( temp_mc / 1000 )).$(( (temp_mc % 1000) / 100 ))
    gpu_power_w=$(( power_uw / 1000000 )).$(( (power_uw % 1000000) / 100000 ))

    # CPU usage (snapshot delta)
    read_cpu_stat
    prev_total=$CPU_TOTAL
    prev_idle=$CPU_IDLE
    sleep 0.1
    read_cpu_stat
    delta_total=$(( CPU_TOTAL - prev_total ))
    delta_idle=$(( CPU_IDLE - prev_idle ))
    if (( delta_total > 0 )); then
        cpu_pct=$(( (delta_total - delta_idle) * 1000 / delta_total ))
        # Format N as N/10 . N%10, handling single-digit values (e.g., 5 → 0.5)
        cpu_pct_fmt="$(( cpu_pct / 10 )).$(( cpu_pct % 10 ))"
    else
        cpu_pct_fmt="0.0"
    fi

    # RAM used (bash builtins only)
    local_mem_total=0
    local_mem_avail=0
    while IFS=': ' read -r key val _; do
        case "$key" in
            MemTotal)     local_mem_total=$val ;;
            MemAvailable) local_mem_avail=$val; break ;;
        esac
    done < /proc/meminfo
    ram_used_mib=$(( (local_mem_total - local_mem_avail) / 1024 ))

    echo "$ts,$gpu_busy,$vram_mib,$gtt_mib,$gpu_temp_c,$gpu_power_w,$cpu_pct_fmt,$ram_used_mib" >> "$OUTPUT"

    # Check duration
    if (( DURATION > 0 && SECONDS - start_time >= DURATION )); then
        break
    fi

    sleep "$INTERVAL"
done