#!/bin/bash
set -euo pipefail

#######################################
# Determine backup mode from the environment only.
# Valid values: "directory" or "postgres".
# Default to "directory" if not provided.
#######################################
BACKUP_MODE="${BACKUP_MODE:-directory}"

#######################################
# Check for required external commands.
#######################################
REQUIRED_CMDS=(restic curl jq)
if [ "$BACKUP_MODE" = "postgres" ]; then
    REQUIRED_CMDS+=(pg_dump)
fi

for cmd in "${REQUIRED_CMDS[@]}"; do
    if ! command -v "$cmd" &>/dev/null; then
        echo "Error: Required command '$cmd' is not installed." >&2
        exit 1
    fi
done

#######################################
# Validate common required environment variables.
#######################################
# Gotify notification settings (optional).
# Set ENABLE_GOTIFY to "true" to enable notifications, any other value or unset disables them.
ENABLE_GOTIFY="${ENABLE_GOTIFY:-true}"

if [ "$ENABLE_GOTIFY" = "true" ]; then
    : "${GOTIFYHOST:?Environment variable GOTIFYHOST is not set (required when ENABLE_GOTIFY=true)}"
    : "${GOTIFYTOKEN:?Environment variable GOTIFYTOKEN is not set (required when ENABLE_GOTIFY=true)}"
    : "${GOTIFYTOPIC:?Environment variable GOTIFYTOPIC is not set (required when ENABLE_GOTIFY=true)}"
else
    log "Gotify notifications disabled. Backup status will be logged to console only."
fi

# Restic encryption password.
: "${RESTIC_PASSWORD:?Environment variable RESTIC_PASSWORD is not set}"

# Use the repository URI directly from the environment.
# Example: export RESTIC_REPOSITORY="rest:http://your-rest-server:8000/backup"
: "${RESTIC_REPOSITORY:?Environment variable RESTIC_REPOSITORY is not set}"

#######################################
# Validate mode-specific environment variables.
#######################################
case "$BACKUP_MODE" in
    directory)
        : "${SOURCEDIR:?Environment variable SOURCEDIR is not set (required for directory backup mode)}"
        ;;
    postgres)
        : "${PGHOST:?Environment variable PGHOST is not set (required for PostgreSQL backup mode)}"
        : "${PGDATABASE:?Environment variable PGDATABASE is not set (required for PostgreSQL backup mode)}"
        : "${PGUSER:?Environment variable PGUSER is not set (required for PostgreSQL backup mode)}"
        # Optional: default PGPORT to 5432.
        : "${PGPORT:=5432}"
        if [ -z "${PGPASSWORD:-}" ]; then
            echo "Warning: Environment variable PGPASSWORD is not set. pg_dump may fail if authentication is required."
        fi
        ;;
    *)
        echo "Error: Unknown backup mode '$BACKUP_MODE'. Valid modes are 'directory' and 'postgres'." >&2
        exit 1
        ;;
esac

#######################################
# Build the Gotify URL (only if Gotify is enabled).
#######################################
if [ "$ENABLE_GOTIFY" = "true" ]; then
    GOTIFYURL="${GOTIFYHOST}/message?token=${GOTIFYTOKEN}"
fi

#######################################
# Date format for logging.
#######################################
LOG_DATE_FORMAT="%Y-%m-%dT%T"

#######################################
# Log a message with a timestamp.
# Arguments:
#   Message to log.
#######################################
log() {
    echo "$(date +"$LOG_DATE_FORMAT") - $*"
}

#######################################
# Send a notification via Gotify.
# Arguments:
#   message: The message to send.
#######################################
send_notification() {
    local message="$1"
    
    # Only send notification if Gotify is enabled
    if [ "$ENABLE_GOTIFY" != "true" ]; then
        log "$message"
        return 0
    fi
    
    if ! curl -s -X POST "$GOTIFYURL" -F "title=${GOTIFYTOPIC}" -F "message=${message}" >/dev/null; then
        log "Warning: Failed to send notification with message: ${message}"
    fi
}

#######################################
# Run the backup using restic.
# The --no-cache flag disables local caching.
# Arguments:
#   $1 - The source directory to back up.
#######################################
run_restic_backup() {
    local source_dir="$1"
    cd "${source_dir}"
    log "Starting backup of '${source_dir}' to repository ${RESTIC_REPOSITORY}"
    # Capture both stdout and stderr in a variable
    backup_output=$(restic -r "${RESTIC_REPOSITORY}" backup --no-cache --json --verbose . 2>&1)
    # Optionally, also print the output to the console:
    echo "$backup_output"
    # Parse the JSON lines output for the summary message
    summary=$(echo "$backup_output" | jq -r 'select(.message_type=="summary") | "Snapshot " + (.snapshot_id // "none") + ": " + "files new: " + (.files_new|tostring) + ", files changed: " + (.files_changed|tostring) + ", data added: " + (.data_added|tostring) + " bytes in " + (.total_duration|tostring) + " sec"')
    # Check exit code of restic backup (assuming restic exits non-zero on error)
    if [ $? -eq 0 ]; then
        msg="Backup successful. $summary"
        log "$msg"
        send_notification "$msg"
    else
        exit_code=$?
        msg="Backup failed with error code ${exit_code}. $backup_output"
        log "$msg"
        send_notification "$msg"
        exit "$exit_code"
    fi
}


#######################################
# Backup a directory (regular mode).
#######################################
backup_directory() {
    run_restic_backup "${SOURCEDIR}"
}

#######################################
# Backup a PostgreSQL database.
# Dumps the database to a temporary directory and then backs it up.
#######################################
backup_postgres() {
    log "Starting PostgreSQL backup for database '${PGDATABASE}' on host '${PGHOST}'"
    
    # Create a temporary directory for the database dump.
    TEMP_BACKUP_DIR=$(mktemp -d)
    log "Created temporary directory: ${TEMP_BACKUP_DIR}"

    local dump_file="${TEMP_BACKUP_DIR}/dump.sql"
    log "Dumping PostgreSQL database to ${dump_file}..."
    if pg_dump -h "${PGHOST}" -p "${PGPORT}" -U "${PGUSER}" ${PG_DUMP_ARGS:-} "${PGDATABASE}" > "${dump_file}"; then
        log "Database dump created successfully."
    else
        local exit_code=$?
        local msg="PostgreSQL dump failed with error code ${exit_code}"
        log "$msg"
        send_notification "$msg"
        exit "$exit_code"
    fi

    # Back up the directory containing the dump.
    run_restic_backup "${TEMP_BACKUP_DIR}"
}

#######################################
# Cleanup temporary resources.
#######################################
cleanup() {
    if [ -n "${TEMP_BACKUP_DIR:-}" ] && [ -d "${TEMP_BACKUP_DIR}" ]; then
        rm -rf "${TEMP_BACKUP_DIR}"
        log "Removed temporary directory ${TEMP_BACKUP_DIR}"
    fi
}
trap cleanup EXIT

#######################################
# Main routine.
#######################################
main() {
    case "$BACKUP_MODE" in
        directory)
            backup_directory
            ;;
        postgres)
            backup_postgres
            ;;
    esac
}

# Trap termination signals to log and exit cleanly.
trap 'log "Script interrupted. Exiting."; exit 1' SIGINT SIGTERM

main