#!/bin/sh

PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin
CONFIG=$1

#Alias DB command for easy future adjustments
SQL='sqlite3'
alias sql="$SQL"

# Check for dependencies
if ! which $SQL >/dev/null 2>&1; then
    printf '%s\n' "ERROR 12: Missing dependency -- '$sql' command not found." >&2
    exit 12
fi

# BEGIN CONFIG CHECK
### Provides KEY, CHATID, CHKLIST
if [ -n "$CONFIG" ]; then
    if [ -f "$CONFIG" ]; then
        . $CONFIG #Source config file
    else
        printf '%s\n' "$CONFIG: File does not exist." >&2
        exit 10
    fi
else
    if [ -f ".httpcheck_telegram" ]; then
        . .httpcheck_telegram #Source config file
    else
        printf '%s\n' "No configuration file found." >&2
        exit 10
    fi
fi
# Check if config was loaded by examining all configuration variables, exit if not
if [ -z "$KEY" ]; then
    printf '%s\n' "Configuration not set correctly: KEY not set" >&2
    ERROR11=true
fi
if [ -z "$CHATID" ]; then
    printf '%s\n' "Configuration not set correctly: CHATID not set" >&2
    ERROR11=true
fi
if [ -z "$CHKLIST" ]; then
    printf '%s\n' "Configuration not set correctly: CHKLIST not set" >&2
    ERROR11=true
fi
if [ -z "$DB" ]; then
    printf '%s\n' "Configuration not set correctly: DB not set" >&2
    ERROR11=true
fi
if [ -z "$MAX_COUNT" ]; then
    printf '%s\n' "Configuration not set correctly: MAX_COUNT not set" >&2
    ERROR11=true
fi
[ "$ERROR11" = "true" ] && exit 11
# END CONFIG CHECK

#DB functions
db_create() {
    sql $DB "CREATE TABLE problem (
                site TEXT UNIQUE NOT NULL,
                count INT NOT NULL DEFAULT 0,
                alert INT NOT NULL DEFAULT 0,
                sent INT NOT NULL DEFAULT 0
              );"
}
db_addsite() {
    sql $DB "INSERT OR IGNORE INTO problem (site) VALUES('$1');"
}
db_inc() {
    sql $DB "UPDATE problem SET count = count + 1 WHERE site = '$1' AND count < $MAX_COUNT;"
    if [ $(sql $DB "SELECT count FROM problem WHERE site = '$1';") -ge $MAX_COUNT ]; then
       sql $DB "UPDATE problem SET alert = 1 WHERE site = '$1';"
    fi
}
db_dec() {
    sql $DB "UPDATE problem SET count = count - 1 WHERE site = '$1' AND count > 0;"
    if [ $(sql $DB "SELECT count FROM problem WHERE site = '$1';") -le 0 ]; then
       sql $DB "UPDATE problem SET alert = 0 WHERE site = '$1';"
    fi
}


TIME="10"
URL="https://api.telegram.org/bot$KEY/sendMessage"

#Telegram message function
send_message() {
    curl -s --max-time $TIME -d "chat_id=${CHATID}&disable_web_page_preview=1&text=$1" $URL >/dev/null
}

get_http_code() {
    if host $(printf '%s\n' $1 | awk '{gsub("https?://|/.*","")}1') 2>&1 >/dev/null; then
        curl -sILk --max-time $TIME $1 | grep HTTP | tail -n 1 | grep -Eo '[0-9]{3}' || printf '%s\n' 999
    else
        printf '%s\n' 000
    fi
}

print_time() {
    date '+%Y-%m-%d %H:%M:%S'
}

# Prepare message header
#MSG="${HEADER}%0AProblems Found:"
FAILURE=false

# Create database if it doesn't exist
if [ -f $DB ]; then
    printf '%s\n' "Database found: $DB"
else
    printf '%s' "Database not found at '$DB'\nCreating DB ... "
    if db_create; then
        printf '%s\n' "DONE"
    else
        printf '%s\n' "FAILED"
        printf '%s\n' "Database creation failed!" >&2
        exit 13
    fi
fi

# Check HTTP codes
for site in $(grep -v "^#\|^$" $CHKLIST | sort | uniq); do
    db_addsite $site
    respcode=$(get_http_code $site)
    case $respcode in
        000)
            printf '%s\n' "[$(print_time)]: PROBLEM -- $site: DNS record not found" >&2
            db_inc $site
            #MSG="${MSG}%0A%0A %2B ${site}%0A    DNS record not found"
            #FAILURE=true
            ;;
        200)
            printf '%s\n' "[$(print_time)]: OK -- $site returns $respcode"
            db_dec $site
            ;;
        999)
            printf '%s\n' "[$(print_time)]: PROBLEM -- $site caused general cURL failure" >&2
            db_inc $site
            ;;
        *)
            printf '%s\n' "[$(print_time)]: PROBLEM -- $site returns $respcode" >&2
            db_inc $site
            #MSG="${MSG}%0A%0A %2B ${site}%0A    Responding ${respcode}"
            #FAILURE=true
            ;;
    esac
done || exit 2

### # Send compiled message if any problems were found
### if [ "$FAILURE" = "true" ]; then
###     send_message "$MSG" && printf '%s\n' "Problems found. Message sent via Telegram bot" >&2 || printf '%s\n' "Problems found. Message sending has failed"
### fi

# Find down sites without sent alerts
unsent=$(sql $DB "SELECT count(*) FROM problem WHERE alert = 1 AND sent = 0;")
cleared=$(sql $DB "SELECT count(*) FROM problem WHERE alert = 0 AND sent = 1;")
down=$(sql $DB "SELECT count(*) FROM problem WHERE alert = 1;")
downlist=$(sql $DB "SELECT site FROM problem WHERE alert = 1;" | perl -p -e 's/\n/%0A/g')

# If ANY sites have unsent alerts, send a list of ALL sites in 'alert' state
if [ $unsent -gt 0 ]; then
    ALERT="${HEADER}%0ASites Down:%0A${downlist}"
    send_message "$ALERT" && printf '%s\n' "Problems found. Message sent via Telegram bot" >&2 || printf '%s\n' "Problems found. Message sending has failed"
    sql $DB "UPDATE problem SET sent = 1 WHERE sent = 0 AND alert = 1;" #Prevents resending messages
fi

# If ALL sites have cleared alerts, send an all-clear
if [ $cleared -gt 0 ]; then
    clearlist=$(sql $DB "SELECT site FROM problem WHERE alert = 0 AND sent = 1;" | perl -p -e 's/\n/%0A/g')
    CLEARED="${HEADER}%0AThese HTTP alerts have cleared:%0A${clearlist}"
    if [ $down -gt 0 ]; then
        CLEARED="${CLEARED}%0ASites still down:%0A${downlist}"
    fi
    send_message "$CLEARED" && printf '%s\n' "A site's alert status has cleared. Message sent via Telegram bot" >&2 || printf '%s\n' "A site's alert status has cleared. Message sending has failed"
    sql $DB "UPDATE problem SET sent = 0 WHERE sent = 1 AND alert = 0;" #Prevents resending messages
fi

exit 0