#!/bin/bash

# Thinkcentre Monitor - Kubernetes Machine Health Monitor with Home Assistant Integration
# Detects hung machines (502 errors) and auto-reboots them via Home Assistant

# Configuration from environment variables with sensible defaults
TARGET_URL="${TARGET_URL:-http://localhost:8080}"
HA_URL="${HA_URL:-http://homeassistant:8123}"
HA_TOKEN="${HA_TOKEN}"
HA_ENTITY="${HA_ENTITY:-switch.thinkcentre_power}"
LOG_FILE="${LOG_FILE:-/var/log/thinkcenter_monitor.log}"
GRACE_PERIOD="${GRACE_PERIOD:-300}"  # 5 minutes in seconds
CHECK_INTERVAL="${CHECK_INTERVAL:-30}"  # 30 seconds between checks

# State variables
ERROR_START_TIME=""
IN_GRACE_PERIOD=false
LAST_RESPONSE_CODE=""

# Validate required configuration
if [[ -z "$HA_TOKEN" ]]; then
    echo "ERROR: HA_TOKEN environment variable is not set. Exiting." | tee -a "$LOG_FILE"
    exit 1
fi

# Initialize log file
mkdir -p "$(dirname "$LOG_FILE")"
touch "$LOG_FILE"

log() {
    local message="$1"
    local timestamp=$(date '+%Y-%m-%d %H:%M:%S')
    echo "[$timestamp] $message" | tee -a "$LOG_FILE"
}

check_target() {
    # Use curl to get HTTP response code without following redirects
    local response_code=$(curl -s -o /dev/null -w "%{http_code}" -m 5 "$TARGET_URL" 2>/dev/null)
    echo "$response_code"
}

trigger_power_cycle() {
    local entity="$1"
    
    log "ALERT: Triggering power cycle for entity: $entity"
    
    # Turn off
    log "Sending turn_off request to Home Assistant..."
    curl -s -X POST \
        -H "Authorization: Bearer $HA_TOKEN" \
        -H "Content-Type: application/json" \
        -d "{\"entity_id\": \"$entity\"}" \
        "$HA_URL/api/services/switch/turn_off" > /dev/null 2>&1
    
    if [[ $? -eq 0 ]]; then
        log "Turn off request sent successfully"
    else
        log "ERROR: Failed to send turn_off request"
    fi
    
    # Wait 10 seconds
    log "Waiting 10 seconds before power-on..."
    sleep 10
    
    # Turn on
    log "Sending turn_on request to Home Assistant..."
    curl -s -X POST \
        -H "Authorization: Bearer $HA_TOKEN" \
        -H "Content-Type: application/json" \
        -d "{\"entity_id\": \"$entity\"}" \
        "$HA_URL/api/services/switch/turn_on" > /dev/null 2>&1
    
    if [[ $? -eq 0 ]]; then
        log "Turn on request sent successfully"
        log "Power cycle completed for $entity"
    else
        log "ERROR: Failed to send turn_on request"
    fi
    
    # Reset state
    ERROR_START_TIME=""
    IN_GRACE_PERIOD=false
}

log "=== Thinkcentre Monitor Started ==="
log "Configuration:"
log "  TARGET_URL: $TARGET_URL"
log "  HA_URL: $HA_URL"
log "  HA_ENTITY: $HA_ENTITY"
log "  GRACE_PERIOD: ${GRACE_PERIOD}s ($(( GRACE_PERIOD / 60 )) minutes)"
log "  CHECK_INTERVAL: ${CHECK_INTERVAL}s"

# Main monitoring loop
while true; do
    RESPONSE_CODE=$(check_target)
    
    # Log all responses
    log "HTTP Response: $RESPONSE_CODE"
    
    if [[ "$RESPONSE_CODE" == "502" ]]; then
        # 502 Bad Gateway error detected
        
        if [[ -z "$ERROR_START_TIME" ]]; then
            # First 502 error - start grace period
            ERROR_START_TIME=$(date +%s)
            IN_GRACE_PERIOD=true
            log "502 error detected - starting 5-minute grace period (recovery window for deployment scenarios)"
        else
            # Already in grace period - check if it has expired
            CURRENT_TIME=$(date +%s)
            ELAPSED=$((CURRENT_TIME - ERROR_START_TIME))
            
            if [[ $ELAPSED -ge $GRACE_PERIOD ]]; then
                # Grace period expired - trigger power cycle
                log "Grace period expired after ${ELAPSED}s. Service still unavailable."
                trigger_power_cycle "$HA_ENTITY"
                ERROR_START_TIME=""
                IN_GRACE_PERIOD=false
            else
                # Still within grace period
                REMAINING=$((GRACE_PERIOD - ELAPSED))
                log "Still in grace period. Service recovery window: ${REMAINING}s remaining"
            fi
        fi
    else
        # Service is responding (any code other than 502)
        if [[ "$IN_GRACE_PERIOD" == true ]]; then
            # Service recovered during grace period
            CURRENT_TIME=$(date +%s)
            RECOVERY_TIME=$((CURRENT_TIME - ERROR_START_TIME))
            log "Service recovered during grace period after ${RECOVERY_TIME}s. Resetting error state."
            ERROR_START_TIME=""
            IN_GRACE_PERIOD=false
        elif [[ "$RESPONSE_CODE" != "000" ]]; then
            # Service is healthy (not a timeout)
            if [[ -n "$LAST_RESPONSE_CODE" && "$LAST_RESPONSE_CODE" != "$RESPONSE_CODE" ]]; then
                log "Service status changed from $LAST_RESPONSE_CODE to $RESPONSE_CODE"
            fi
        fi
    fi
    
    LAST_RESPONSE_CODE="$RESPONSE_CODE"
    
    # Wait for next check
    sleep "$CHECK_INTERVAL"
done