#!/bin/bash
# ============================================================
#  Log Analyzer
#  Usage: ./log_analyzer.sh <log_file>
#  Example: ./log_analyzer.sh logs/server.log
#  Log line format: DATE TIME LEVEL MESSAGE
#  e.g. 2026-11-01 08:10:03 ERROR Disk space low on /home
# ============================================================

# ---------- 1) Settings (variables) ----------
REPORT_DIR="reports"
LOG_FILE="$1"

# ---------- 2) Check the input argument ----------
if [ $# -ne 1 ]; then
    echo "Usage: $0 <log_file>"
    echo "Example: $0 logs/server.log"
    exit 1
fi

if [ ! -f "$LOG_FILE" ]; then
    echo "Error: file '$LOG_FILE' not found."
    exit 2
fi

if [ ! -s "$LOG_FILE" ]; then
    echo "Error: file '$LOG_FILE' is empty."
    exit 3
fi

# ---------- 3) Functions ----------

# Count lines that have a given level (INFO / WARNING / ERROR)
count_level() {
    local level="$1"
    grep -c " $level " "$LOG_FILE"
}

# Show a short summary of the log file
show_summary() {
    local total=$(wc -l < "$LOG_FILE")
    echo "------ Summary of $LOG_FILE ------"
    echo "Total lines : $total"
    echo "INFO        : $(count_level INFO)"
    echo "WARNING     : $(count_level WARNING)"
    echo "ERROR       : $(count_level ERROR)"
}

# Show only ERROR lines
show_errors() {
    echo "------ ERROR lines ------"
    grep " ERROR " "$LOG_FILE"
}

# Search for a word that the user types
search_keyword() {
    read -p "Enter a word to search: " keyword

    if [ -z "$keyword" ]; then
        echo "Error: you did not enter any word."
        return
    fi

    echo "------ Lines containing '$keyword' ------"
    if ! grep -i -- "$keyword" "$LOG_FILE"; then
        echo "No result found for '$keyword'."
    fi
}

# Show the 3 most repeated error messages
top_errors() {
    echo "------ Top 3 repeated errors ------"
    grep " ERROR " "$LOG_FILE" | cut -d' ' -f4- | sort | uniq -c | sort -nr | head -3
}

# Save summary + top errors into a report file
save_report() {
    mkdir -p "$REPORT_DIR"
    local report_file="$REPORT_DIR/report_$(date +%Y-%m-%d).txt"

    echo "Report created at: $(date '+%Y-%m-%d %H:%M:%S')" > "$report_file"
    show_summary >> "$report_file"
    top_errors   >> "$report_file"

    echo "Report saved to: $report_file"
}

# ---------- 4) Main menu (loop) ----------
while true; do
    echo
    echo "========= Log Analyzer ========="
    echo "1) Show summary"
    echo "2) Show ERROR lines"
    echo "3) Search a word"
    echo "4) Top 3 repeated errors"
    echo "5) Save report"
    echo "0) Exit"
    read -p "Your choice: " choice

    case "$choice" in
        1) show_summary ;;
        2) show_errors ;;
        3) search_keyword ;;
        4) top_errors ;;
        5) save_report ;;
        0) echo "Goodbye!"; exit 0 ;;
        *) echo "Invalid choice. Please enter a number from 0 to 5." ;;
    esac
done