#!/bin/bash

# ==============================================================================
# SAP HANA Backup Script
#
# Performs schema exports and/or tenant backups for a SAP HANA database.
# Designed to be executed via a cronjob.
# Reads all settings from the backup.conf file in the same directory.
# ==============================================================================

# --- Configuration and Setup ---

# Find the script's own directory to locate the config file
SCRIPT_DIR=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" &> /dev/null && pwd)
CONFIG_FILE="${SCRIPT_DIR}/backup.conf"

# Check for config file and source it
if [[ -f "$CONFIG_FILE" ]]; then
    source "$CONFIG_FILE"
else
    echo "❌ Error: Configuration file not found at '${CONFIG_FILE}'"
    exit 1
fi

# Check if hdbsql executable exists
if [[ ! -x "$HDBSQL_PATH" ]]; then
    echo "❌ Error: hdbsql not found or not executable at '${HDBSQL_PATH}'"
    exit 1
fi

# Calculate threads to use (half of the available cores, but at least 1)
TOTAL_THREADS=$(nproc --all)
THREADS=$((TOTAL_THREADS / 2))
if [[ "$THREADS" -eq 0 ]]; then
    THREADS=1
fi

# --- Functions ---

# Performs a binary export of a specific schema and compresses it.
perform_schema_export() {
    echo "⬇️  Starting schema export for '${SCHEMA_NAME}'..."

    local timestamp
    timestamp=$(date +%Y%m%d_%H%M%S)
    local export_dir="${BACKUP_BASE_DIR}/schema"
    local export_path="${export_dir}/${SCHEMA_NAME}_${timestamp}"
    local archive_file="${export_path}.tar.gz"

    # Create the target directory if it doesn't exist
    mkdir -p "$export_dir"

    # Construct and execute the EXPORT query
    local query="EXPORT \"${SCHEMA_NAME}\".\"*\" AS BINARY INTO '${export_path}' WITH REPLACE THREADS ${THREADS};"

    # We redirect stdout and stderr to /dev/null for cleaner cron logs.
    # Remove "> /dev/null 2>&1" if you need to debug connection issues.
    "$HDBSQL_PATH" -U "$USER_KEY" "$query" > /dev/null 2>&1
    local exit_code=$?

    if [[ "$exit_code" -eq 0 ]]; then
        echo "    ✅ Successfully exported schema '${SCHEMA_NAME}'."

        # Compress the exported directory
        echo "    🗜️  Compressing exported files..."
        tar -czf "$archive_file" -C "$export_dir" "$(basename "$export_path")"
        local tar_exit_code=$?

        if [[ "$tar_exit_code" -eq 0 ]]; then
            echo "    ✅ Successfully created archive '${archive_file}'."
            echo "    🧹 Cleaning up temporary directory..."
            rm -rf "$export_path"
            echo "    ✨ Cleanup complete."
        else
            echo "    ❌ Error: Failed to compress '${export_path}'."
        fi
    else
        echo "    ❌ Error: Failed to export schema '${SCHEMA_NAME}' (hdbsql exit code: ${exit_code})."
    fi
}

# Performs a full backup of the tenant database.
perform_tenant_backup() {
    echo "⬇️  Starting tenant backup..."
    
    local timestamp
    timestamp=$(date +%Y%m%d_%H%M%S)
    local backup_dir="${BACKUP_BASE_DIR}/tenant"
    # HANA will create the final file; we just provide the location and prefix.
    local backup_path_prefix="${backup_dir}/backup_${timestamp}"

    # Create the target directory if it doesn't exist
    mkdir -p "$backup_dir"

    # The USER_KEY must be configured to connect to the desired tenant database.
    local query="BACKUP DATA USING FILE ('${backup_path_prefix}')"

    # We redirect stdout and stderr to /dev/null for cleaner cron logs.
    # Remove "> /dev/null 2>&1" if you need to debug connection issues.
    "$HDBSQL_PATH" -U "$USER_KEY" "$query" > /dev/null 2>&1
    local exit_code=$?

    if [[ "$exit_code" -eq 0 ]]; then
        echo "    ✅ Successfully initiated tenant backup with prefix '${backup_path_prefix}'."
    else
        echo "    ❌ Error: Failed to initiate tenant backup (hdbsql exit code: ${exit_code})."
    fi
}

# --- Main Execution ---

echo "⚙️  Starting HANA backup process..."

# Ensure the base directory exists
mkdir -p "$BACKUP_BASE_DIR"

case "$BACKUP_TYPE" in
    schema)
        perform_schema_export
        ;;
    tenant)
        perform_tenant_backup
        ;;
    all)
        perform_schema_export
        echo "" # Add a newline for better readability
        perform_tenant_backup
        ;;
    *)
        echo "    ❌ Error: Invalid BACKUP_TYPE '${BACKUP_TYPE}' in config. Use 'schema', 'tenant', or 'all'."
        ;;
esac

echo "📦 Backup process complete."
echo "👋 Exiting."