#!/bin/bash
# This script monitors disk space and sends an alert if usage exceeds a specified threshold.
# Usage: ./storage-monitor.sh [mount-point] [threshold] [url_to_call]

# Check if correct number of arguments provided
if [ $# -lt 2 ]; then
    echo "Usage: $0 [mount-point] [threshold] [url_to_call]"
    echo "Example: $0 / 80 https://example.com/alert"
    echo "Threshold should be a percentage (0-100)"
    exit 1
fi

# Assign arguments to variables
MOUNT_POINT="$1"
THRESHOLD="$2"
URL_TO_CALL="$3"

# Validate that mount point exists
if [ ! -d "$MOUNT_POINT" ]; then
    echo "Error: Mount point '$MOUNT_POINT' does not exist"
    exit 1
fi

# Validate threshold is a number between 0 and 100
if ! [[ "$THRESHOLD" =~ ^[0-9]+$ ]] || [ "$THRESHOLD" -lt 0 ] || [ "$THRESHOLD" -gt 100 ]; then
    echo "Error: Threshold must be a number between 0 and 100"
    exit 1
fi

# Get disk usage percentage (remove % sign)
USAGE=$(df "$MOUNT_POINT" | awk 'NR==2 {print $5}' | sed 's/%//')

# Check if we got a valid usage value
if ! [[ "$USAGE" =~ ^[0-9]+$ ]]; then
    echo "Error: Could not determine disk usage for '$MOUNT_POINT'"
    exit 1
fi

# Display current usage
echo "Current disk usage for $MOUNT_POINT: $USAGE%"

# Check if usage exceeds threshold
if [ "$USAGE" -gt "$THRESHOLD" ]; then
    echo "ALERT: Disk usage ($USAGE%) exceeds threshold ($THRESHOLD%)"
    
    # Prepare alert message
    MESSAGE="ALERT: Disk usage on $MOUNT_POINT is at $USAGE%, exceeding threshold of $THRESHOLD%"
    
    # If URL is provided, send HTTP request
    if [ -n "$URL_TO_CALL" ]; then
        echo "Sending alert to: $URL_TO_CALL"
        
        # Try to send alert using curl (most common)
        if command -v curl &> /dev/null; then
            curl -X POST -d "message=$MESSAGE" "$URL_TO_CALL" 2>/dev/null
        # Fallback to wget if curl is not available
        elif command -v wget &> /dev/null; then
            wget --post-data="message=$MESSAGE" "$URL_TO_CALL" -O /dev/null 2>/dev/null
        else
            echo "Warning: Neither curl nor wget is available to send HTTP request"
        fi
    fi
    
    # Exit with error code to indicate alert condition
    exit 2
else
    echo "Disk usage ($USAGE%) is within acceptable limits (threshold: $THRESHOLD%)"
    exit 0
fi
# Usage: ./storage-monitor.sh [mount-point] [threshold] [url_to_call]