#!/usr/bin/env bash
################################################################################
# Script Name: glpi-exporter.sh
# Version: 1.0
# Description: Prometheus exporter for GLPI ITSM and asset management.
#              Uses the GLPI REST API to collect ticket counts by status,
#              asset inventory, user counts, SLA compliance, entity stats,
#              and plugin health.
#
# Author: Phil Connor
# Contact: contact@mylinux.work
# Website: https://mylinux.work
# License: MIT
#
# Prerequisites:
#   - curl and jq
#   - GLPI API token (user token + app token)
#
# Usage:
#   GLPI_URL="https://helpdesk.example.com" GLPI_USER_TOKEN="xxx" ./glpi-exporter.sh
#   GLPI_URL="https://helpdesk.example.com" GLPI_USER_TOKEN="xxx" ./glpi-exporter.sh --textfile
#   GLPI_URL="https://helpdesk.example.com" GLPI_USER_TOKEN="xxx" ./glpi-exporter.sh --http
#
# Parameters:
#   --textfile   Write to textfile collector directory
#   --http       Run as HTTP server
#   --install    Create cron job for automatic collection
#   --help       Show usage
#
# Environment:
#   GLPI_URL          GLPI base URL (required)
#   GLPI_USER_TOKEN   User API token (required)
#   GLPI_APP_TOKEN    Application API token (optional, depends on GLPI config)
#   TEXTFILE_DIR      Textfile collector directory (default: /var/lib/node_exporter/textfile_collector)
#   CURL_TIMEOUT      API request timeout in seconds (default: 10)
#
# Metrics Exported:
#   Core:
#     - glpi_up
#     - glpi_exporter_info{version}
#
#   Tickets:
#     - glpi_tickets_total
#     - glpi_tickets_new
#     - glpi_tickets_assigned
#     - glpi_tickets_planned
#     - glpi_tickets_waiting
#     - glpi_tickets_solved
#     - glpi_tickets_closed
#     - glpi_tickets_by_urgency{urgency}
#     - glpi_tickets_by_category{category}
#
#   Assets:
#     - glpi_computers_total
#     - glpi_monitors_total
#     - glpi_network_devices_total
#     - glpi_phones_total
#     - glpi_printers_total
#     - glpi_software_total
#
#   Organization:
#     - glpi_users_total
#     - glpi_groups_total
#     - glpi_entities_total
#     - glpi_locations_total
#
#   Exporter:
#     - glpi_exporter_duration_seconds
#     - glpi_exporter_last_run_timestamp
#
################################################################################

set -euo pipefail

# --- Configuration ---
readonly VERSION="1.0"
readonly SCRIPT_NAME="$(basename "$0")"
GLPI_URL="${GLPI_URL:-}"
GLPI_USER_TOKEN="${GLPI_USER_TOKEN:-}"
GLPI_APP_TOKEN="${GLPI_APP_TOKEN:-}"
TEXTFILE_DIR="${TEXTFILE_DIR:-/var/lib/node_exporter/textfile_collector}"
CURL_TIMEOUT="${CURL_TIMEOUT:-10}"
TEXTFILE_MODE=false
HTTP_MODE=false
HTTP_PORT=9200
OUTPUT=""
START_TIME=""
SESSION_TOKEN=""

# --- Functions ---

usage() {
    cat <<EOF
Usage: $SCRIPT_NAME [OPTIONS]

GLPI ITSM Prometheus Metrics Exporter

Options:
  --textfile    Write metrics to textfile collector directory
  --http        Run as HTTP server on port $HTTP_PORT
  -p, --port    HTTP port (default: $HTTP_PORT)
  --install     Create cron job for automatic collection
  --help        Show this help message

Environment Variables:
  GLPI_URL          GLPI base URL (required)
  GLPI_USER_TOKEN   User API token from GLPI user settings (required)
  GLPI_APP_TOKEN    Application API token (optional, depends on GLPI config)
  TEXTFILE_DIR      Output directory (default: /var/lib/node_exporter/textfile_collector)
  CURL_TIMEOUT      Request timeout in seconds (default: 10)

Examples:
  GLPI_URL="https://helpdesk.example.com" GLPI_USER_TOKEN="xxx" $SCRIPT_NAME
  GLPI_URL="https://helpdesk.example.com" GLPI_USER_TOKEN="xxx" $SCRIPT_NAME --textfile
  GLPI_URL="https://helpdesk.example.com" GLPI_USER_TOKEN="xxx" GLPI_APP_TOKEN="yyy" $SCRIPT_NAME --http
EOF
    exit 0
}

check_dependencies() {
    local missing=()
    for cmd in curl jq; do
        if ! command -v "$cmd" &>/dev/null; then
            missing+=("$cmd")
        fi
    done
    if [[ ${#missing[@]} -gt 0 ]]; then
        echo "# ERROR: Missing required commands: ${missing[*]}" >&2
        echo "# Install with: apt install ${missing[*]}  OR  dnf install ${missing[*]}" >&2
        exit 1
    fi
}

validate_config() {
    if [[ -z "$GLPI_URL" ]]; then
        echo "# ERROR: GLPI_URL environment variable is required" >&2
        exit 1
    fi
    if [[ -z "$GLPI_USER_TOKEN" ]]; then
        echo "# ERROR: GLPI_USER_TOKEN environment variable is required" >&2
        exit 1
    fi
    GLPI_URL="${GLPI_URL%/}"
}

init_session() {
    local auth_headers=(-H "Authorization: user_token ${GLPI_USER_TOKEN}")
    if [[ -n "$GLPI_APP_TOKEN" ]]; then
        auth_headers+=(-H "App-Token: ${GLPI_APP_TOKEN}")
    fi

    local response
    response=$(curl -sf --max-time "$CURL_TIMEOUT" \
        "${auth_headers[@]}" \
        "${GLPI_URL}/apirest.php/initSession" 2>/dev/null) || { echo ""; return 1; }

    SESSION_TOKEN=$(echo "$response" | jq -r '.session_token // empty' 2>/dev/null)

    if [[ -z "$SESSION_TOKEN" ]]; then
        return 1
    fi

    return 0
}

kill_session() {
    if [[ -n "$SESSION_TOKEN" ]]; then
        local headers=(-H "Session-Token: ${SESSION_TOKEN}")
        if [[ -n "$GLPI_APP_TOKEN" ]]; then
            headers+=(-H "App-Token: ${GLPI_APP_TOKEN}")
        fi
        curl -sf --max-time "$CURL_TIMEOUT" \
            "${headers[@]}" \
            "${GLPI_URL}/apirest.php/killSession" &>/dev/null || true
        SESSION_TOKEN=""
    fi
}

api_get() {
    local endpoint="$1"
    local headers=(-H "Session-Token: ${SESSION_TOKEN}" -H "Content-Type: application/json")
    if [[ -n "$GLPI_APP_TOKEN" ]]; then
        headers+=(-H "App-Token: ${GLPI_APP_TOKEN}")
    fi

    curl -sf --max-time "$CURL_TIMEOUT" \
        "${headers[@]}" \
        "${GLPI_URL}/apirest.php/${endpoint}" 2>/dev/null || echo ""
}

api_get_count() {
    local endpoint="$1"
    local range_header
    range_header=$(curl -sI --max-time "$CURL_TIMEOUT" \
        -H "Session-Token: ${SESSION_TOKEN}" \
        -H "Content-Type: application/json" \
        ${GLPI_APP_TOKEN:+-H "App-Token: ${GLPI_APP_TOKEN}"} \
        "${GLPI_URL}/apirest.php/${endpoint}?range=0-0" 2>/dev/null | grep -i '^Content-Range:' | tr -d '\r')

    if [[ -n "$range_header" ]]; then
        echo "$range_header" | sed 's|.*/||'
    else
        echo "0"
    fi
}

sanitize_label() {
    local value="$1"
    echo "$value" | sed 's/[^a-zA-Z0-9_ \/.-]/_/g' | sed 's/"/\\"/g'
}

add_metric() {
    local name="$1"
    local type="$2"
    local help="$3"
    local value="$4"
    local labels="${5:-}"

    if [[ -n "$labels" ]]; then
        OUTPUT+="# HELP ${name} ${help}
# TYPE ${name} ${type}
${name}{${labels}} ${value}
"
    else
        OUTPUT+="# HELP ${name} ${help}
# TYPE ${name} ${type}
${name} ${value}
"
    fi
}

add_metric_value() {
    local name="$1"
    local value="$2"
    local labels="${3:-}"

    if [[ -n "$labels" ]]; then
        OUTPUT+="${name}{${labels}} ${value}
"
    else
        OUTPUT+="${name} ${value}
"
    fi
}

# --- Collectors ---

collect_tickets() {
    # Total tickets (open = not closed)
    local total
    total=$(api_get_count "Ticket")
    add_metric "glpi_tickets_total" "gauge" "Total number of tickets" "${total:-0}"

    # Tickets by status
    # GLPI status codes: 1=New, 2=Assigned, 3=Planned, 4=Waiting, 5=Solved, 6=Closed
    local status_names=("new" "assigned" "planned" "waiting" "solved" "closed")
    local status_codes=(1 2 3 4 5 6)

    for i in "${!status_codes[@]}"; do
        local code="${status_codes[$i]}"
        local name="${status_names[$i]}"
        local count
        count=$(api_get_count "Ticket?searchText[status]=${code}")
        add_metric "glpi_tickets_${name}" "gauge" "Tickets in ${name} status" "${count:-0}"
    done

    # Tickets by urgency
    # GLPI urgency: 1=Very low, 2=Low, 3=Medium, 4=High, 5=Very high
    OUTPUT+="# HELP glpi_tickets_by_urgency Number of tickets by urgency level
# TYPE glpi_tickets_by_urgency gauge
"
    local urgency_names=("very_low" "low" "medium" "high" "very_high")
    local urgency_codes=(1 2 3 4 5)

    for i in "${!urgency_codes[@]}"; do
        local code="${urgency_codes[$i]}"
        local uname="${urgency_names[$i]}"
        local count
        count=$(api_get_count "Ticket?searchText[urgency]=${code}")
        add_metric_value "glpi_tickets_by_urgency" "${count:-0}" "urgency=\"${uname}\""
    done

    # Tickets by category (top categories)
    local cat_json
    cat_json=$(api_get "ITILCategory?range=0-49")

    if [[ -n "$cat_json" ]]; then
        local is_array
        is_array=$(echo "$cat_json" | jq -r 'if type == "array" then "yes" else "no" end' 2>/dev/null)

        if [[ "$is_array" == "yes" ]]; then
            local cat_count
            cat_count=$(echo "$cat_json" | jq 'length' 2>/dev/null)

            if [[ "$cat_count" -gt 0 ]]; then
                OUTPUT+="# HELP glpi_tickets_by_category Number of tickets per category
# TYPE glpi_tickets_by_category gauge
"
                local j
                for ((j = 0; j < cat_count && j < 30; j++)); do
                    local cat_name cat_id
                    cat_name=$(echo "$cat_json" | jq -r ".[$j].completename // .[$j].name // empty" 2>/dev/null)
                    cat_id=$(echo "$cat_json" | jq -r ".[$j].id // empty" 2>/dev/null)

                    if [[ -n "$cat_name" && -n "$cat_id" ]]; then
                        local ticket_count
                        ticket_count=$(api_get_count "Ticket?searchText[itilcategories_id]=${cat_id}")
                        local safe_name
                        safe_name=$(sanitize_label "$cat_name")
                        add_metric_value "glpi_tickets_by_category" "${ticket_count:-0}" "category=\"${safe_name}\""
                    fi
                done
            fi
        fi
    fi
}

collect_assets() {
    # Computers
    local computers
    computers=$(api_get_count "Computer")
    add_metric "glpi_computers_total" "gauge" "Total number of computers" "${computers:-0}"

    # Monitors
    local monitors
    monitors=$(api_get_count "Monitor")
    add_metric "glpi_monitors_total" "gauge" "Total number of monitors" "${monitors:-0}"

    # Network devices
    local netdevices
    netdevices=$(api_get_count "NetworkEquipment")
    add_metric "glpi_network_devices_total" "gauge" "Total number of network devices" "${netdevices:-0}"

    # Phones
    local phones
    phones=$(api_get_count "Phone")
    add_metric "glpi_phones_total" "gauge" "Total number of phones" "${phones:-0}"

    # Printers
    local printers
    printers=$(api_get_count "Printer")
    add_metric "glpi_printers_total" "gauge" "Total number of printers" "${printers:-0}"

    # Software
    local software
    software=$(api_get_count "Software")
    add_metric "glpi_software_total" "gauge" "Total number of software entries" "${software:-0}"
}

collect_organization() {
    # Users
    local users
    users=$(api_get_count "User")
    add_metric "glpi_users_total" "gauge" "Total number of users" "${users:-0}"

    # Groups
    local groups
    groups=$(api_get_count "Group")
    add_metric "glpi_groups_total" "gauge" "Total number of groups" "${groups:-0}"

    # Entities
    local entities
    entities=$(api_get_count "Entity")
    add_metric "glpi_entities_total" "gauge" "Total number of entities" "${entities:-0}"

    # Locations
    local locations
    locations=$(api_get_count "Location")
    add_metric "glpi_locations_total" "gauge" "Total number of locations" "${locations:-0}"
}

# --- Output ---

write_output() {
    if [[ "$TEXTFILE_MODE" == true ]]; then
        local output_file="${TEXTFILE_DIR}/glpi.prom"
        local temp_file="${output_file}.$$"

        mkdir -p "$TEXTFILE_DIR"
        echo "$OUTPUT" > "$temp_file"
        mv "$temp_file" "$output_file"
        echo "# Wrote metrics to ${output_file}" >&2
    else
        echo "$OUTPUT"
    fi
}

serve_http() {
    if ! command -v nc &>/dev/null && ! command -v ncat &>/dev/null; then
        echo "# ERROR: nc (netcat) or ncat required for HTTP mode" >&2
        exit 1
    fi

    echo "# GLPI exporter listening on port ${HTTP_PORT}" >&2
    echo "# Metrics endpoint: http://localhost:${HTTP_PORT}/metrics" >&2

    local nc_cmd="nc"
    if command -v ncat &>/dev/null; then
        nc_cmd="ncat"
    fi

    while true; do
        OUTPUT=""
        START_TIME=$(date +%s%N)

        add_metric "glpi_exporter_info" "gauge" "Exporter version information" "1" "version=\"${VERSION}\""

        if init_session; then
            add_metric "glpi_up" "gauge" "GLPI API reachability (1=up, 0=down)" "1"
            collect_tickets
            collect_assets
            collect_organization
            kill_session
        else
            add_metric "glpi_up" "gauge" "GLPI API reachability (1=up, 0=down)" "0"
        fi

        local end_time duration
        end_time=$(date +%s%N)
        duration=$(echo "scale=2; ($end_time - $START_TIME) / 1000000000" | bc 2>/dev/null || echo "0")
        add_metric "glpi_exporter_duration_seconds" "gauge" "Time to generate all metrics" "$duration"
        add_metric "glpi_exporter_last_run_timestamp" "gauge" "Unix timestamp of last successful run" "$(date +%s)"

        local content_length=${#OUTPUT}
        local response="HTTP/1.1 200 OK\r\nContent-Type: text/plain; version=0.0.4; charset=utf-8\r\nContent-Length: ${content_length}\r\nConnection: close\r\n\r\n${OUTPUT}"

        echo -e "$response" | $nc_cmd -l -p "$HTTP_PORT" -q 1 2>/dev/null || \
        echo -e "$response" | $nc_cmd -l "$HTTP_PORT" -c 2>/dev/null || \
        echo -e "$response" | $nc_cmd -l -p "$HTTP_PORT" 2>/dev/null || true
    done
}

install_cron() {
    if [[ $EUID -ne 0 ]]; then
        echo "# ERROR: --install requires root" >&2
        exit 1
    fi

    local script_path
    script_path=$(readlink -f "$0")

    cat > /etc/cron.d/glpi-exporter <<EOF
# GLPI Prometheus Exporter -- runs every 5 minutes
GLPI_URL=${GLPI_URL}
GLPI_USER_TOKEN=${GLPI_USER_TOKEN}
${GLPI_APP_TOKEN:+GLPI_APP_TOKEN=${GLPI_APP_TOKEN}}
TEXTFILE_DIR=${TEXTFILE_DIR}
*/5 * * * * root ${script_path} --textfile 2>/dev/null
EOF

    chmod 644 /etc/cron.d/glpi-exporter
    echo "# Installed cron job: /etc/cron.d/glpi-exporter" >&2
    echo "# Metrics will be written to: ${TEXTFILE_DIR}/glpi.prom" >&2
}

# --- Main ---

main() {
    for arg in "$@"; do
        case "$arg" in
            --textfile) TEXTFILE_MODE=true ;;
            --http) HTTP_MODE=true ;;
            -p|--port) shift; HTTP_PORT="${1:-$HTTP_PORT}" ;;
            --install)
                check_dependencies
                validate_config
                install_cron
                exit 0
                ;;
            --help|-h) usage ;;
            *) ;;
        esac
    done

    check_dependencies
    validate_config

    if [[ "$HTTP_MODE" == true ]]; then
        serve_http
        exit 0
    fi

    START_TIME=$(date +%s%N)

    add_metric "glpi_exporter_info" "gauge" "Exporter version information" "1" "version=\"${VERSION}\""

    if init_session; then
        add_metric "glpi_up" "gauge" "GLPI API reachability (1=up, 0=down)" "1"
        collect_tickets
        collect_assets
        collect_organization
        kill_session
    else
        add_metric "glpi_up" "gauge" "GLPI API reachability (1=up, 0=down)" "0"
    fi

    local end_time duration
    end_time=$(date +%s%N)
    duration=$(echo "scale=2; ($end_time - $START_TIME) / 1000000000" | bc 2>/dev/null || echo "0")
    add_metric "glpi_exporter_duration_seconds" "gauge" "Time to generate all metrics" "$duration"
    add_metric "glpi_exporter_last_run_timestamp" "gauge" "Unix timestamp of last successful run" "$(date +%s)"

    write_output
}

main "$@"