#!/bin/bash
# Version: 1.0.0
# ==============================================================================
# SAP HANA Backup Script
#
# Performs schema exports for one or more schemas 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.
# Accepts the schema name as its first argument.
perform_schema_export() {
    local schema_name="$1"
    if [[ -z "$schema_name" ]]; then
        echo "   ❌ Error: No schema name provided to perform_schema_export function."
        return 1
    fi

    echo "⬇️  Starting schema export for '${schema_name}'..."

    local timestamp
    timestamp=$(date +%Y%m%d_%H%M%S)
    local export_base_dir="${BACKUP_BASE_DIR}/schema"
    local export_path="${export_base_dir}/${schema_name}_${timestamp}"
    local query_export_path="$export_path" # Default path for the EXPORT query

    if [[ "$COMPRESS_SCHEMA" == "true" ]]; then
        export_path="${export_base_dir}/tmp/${schema_name}_${timestamp}"
        query_export_path="$export_path"
        echo "   ℹ️ Compression enabled. Using temporary export path: ${export_path}"
    fi

    local archive_file="${export_base_dir}/${schema_name}_${timestamp}.tar.gz"

    mkdir -p "$(dirname "$export_path")"

    local query="EXPORT \"${schema_name}\".\"*\" AS BINARY INTO '${query_export_path}' WITH REPLACE THREADS ${THREADS};"

    "$HDBSQL_PATH" -U "$USER_KEY" "$query" > /dev/null 2>&1
    local exit_code=$?

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

        if [[ "$COMPRESS_SCHEMA" == "true" ]]; then
            echo "   🗜️  Compressing exported files..."
            tar -czf "$archive_file" -C "$(dirname "$export_path")" "$(basename "$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 "$export_path"
                rmdir --ignore-fail-on-non-empty "$(dirname "$export_path")"
                echo "   ✨ Cleanup complete."
            else
                echo "   ❌ Error: Failed to compress '${export_path}'."
            fi
        else
            echo "   ℹ️ Compression disabled. Raw export files are located at '${export_path}'."
        fi
    else
        echo "   ❌ Error: Failed to export schema '${schema_name}' (hdbsql exit code: ${exit_code})."
    fi
}

# NEW: Loops through the schemas in the config file and runs an export for each.
run_all_schema_exports() {
    if [[ -z "$SCHEMA_NAMES" ]]; then
        echo "   ⚠️  Warning: SCHEMA_NAMES variable is not set in config. Skipping schema export."
        return
    fi

    echo "🔎 Found schemas to export: ${SCHEMA_NAMES}"
    for schema in $SCHEMA_NAMES; do
        perform_schema_export "$schema"
        echo "--------------------------------------------------"
    done
}

# Performs a full backup of the tenant database.
perform_tenant_backup() {
    echo "⬇️  Starting tenant backup..."
   
    local timestamp
    timestamp=$(date +%Y%m%d_%H%M%S)
    local backup_base_dir="${BACKUP_BASE_DIR}/tenant"
    local backup_path_prefix
    local backup_target_dir

    if [[ "$COMPRESS_TENANT" == "true" ]]; then
        backup_target_dir="${backup_base_dir}/tmp"
        backup_path_prefix="${backup_target_dir}/backup_${timestamp}"
        echo "   ℹ️ Compression enabled. Using temporary backup path: ${backup_path_prefix}"
    else
        backup_target_dir="$backup_base_dir"
        backup_path_prefix="${backup_target_dir}/backup_${timestamp}"
    fi

    mkdir -p "$backup_target_dir"

    local query="BACKUP DATA USING FILE ('${backup_path_prefix}')"

    "$HDBSQL_PATH" -U "$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}'."

        if [[ "$COMPRESS_TENANT" == "true" ]]; then
            local archive_file="${backup_base_dir}/backup_${timestamp}.tar.gz"
            echo "   🗜️  Compressing backup files..."
            tar -czf "$archive_file" -C "$backup_target_dir" .
            local tar_exit_code=$?

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

# --- Main Execution ---

echo "⚙️  Starting HANA backup process..."

mkdir -p "$BACKUP_BASE_DIR"

case "$BACKUP_TYPE" in
    schema)
        run_all_schema_exports
        ;;
    tenant)
        perform_tenant_backup
        ;;
    all)
        run_all_schema_exports
        perform_tenant_backup
        ;;
    *)
        echo "   ❌ Error: Invalid BACKUP_TYPE '${BACKUP_TYPE}' in config. Use 'schema', 'tenant', or 'all'."
        ;;
esac

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