/*
Copyright (c) Edgeless Systems GmbH

SPDX-License-Identifier: AGPL-3.0-only
*/

package cloudcmd

import (
	"context"
	"errors"
	"fmt"
	"io"
	"os"

	"github.com/edgelesssys/constellation/v2/cli/internal/terraform"
	"github.com/edgelesssys/constellation/v2/internal/file"
)

// plan prepares a workspace and plans the possible Terraform actions.
// This will either create a new workspace or update an existing one.
// In case of possible migrations, the diff is written to outWriter and this function returns true.
func plan(
	ctx context.Context, tfClient tfPlanner, fileHandler file.Handler,
	outWriter io.Writer, logLevel terraform.LogLevel, vars terraform.Variables,
	templateDir, existingWorkspace, backupDir string,
) (bool, error) {
	isNewWorkspace, err := fileHandler.IsEmpty(existingWorkspace)
	if err != nil {
		if !errors.Is(err, os.ErrNotExist) {
			return false, fmt.Errorf("checking if workspace is empty: %w", err)
		}
		isNewWorkspace = true
	}

	// Backup old workspace if it exists
	if !isNewWorkspace {
		if err := ensureFileNotExist(fileHandler, backupDir); err != nil {
			return false, fmt.Errorf("backup directory %s already exists: %w", backupDir, err)
		}
		if err := fileHandler.CopyDir(existingWorkspace, backupDir); err != nil {
			return false, fmt.Errorf("backing up old workspace: %w", err)
		}
	}

	// Move the new embedded Terraform files into the workspace.
	if err := tfClient.PrepareWorkspace(templateDir, vars); err != nil {
		return false, fmt.Errorf("preparing terraform workspace: %w", err)
	}

	hasDiff, err := tfClient.Plan(ctx, logLevel)
	if err != nil {
		return false, fmt.Errorf("terraform plan: %w", err)
	}

	// If we are planning in a new workspace, we don't want to show the plan
	if isNewWorkspace {
		return hasDiff, nil
	}

	if hasDiff {
		if err := tfClient.ShowPlan(ctx, logLevel, outWriter); err != nil {
			return false, fmt.Errorf("terraform show plan: %w", err)
		}
	}
	return hasDiff, nil
}

// restoreBackup replaces the existing Terraform workspace with the backup.
// If no backup exists, this function simply removes workingDir.
func restoreBackup(fileHandler file.Handler, workingDir, backupDir string) error {
	if err := fileHandler.RemoveAll(workingDir); err != nil {
		return fmt.Errorf("removing existing workspace: %w", err)
	}
	if err := fileHandler.CopyDir(
		backupDir,
		workingDir,
	); err != nil && !errors.Is(err, os.ErrNotExist) { // ignore not found error because backup does not exist for new clusters
		return fmt.Errorf("replacing terraform workspace with backup: %w", err)
	}

	if err := fileHandler.RemoveAll(backupDir); err != nil {
		return fmt.Errorf("removing backup directory: %w", err)
	}
	return nil
}

// ensureFileNotExist checks if a single file or directory does not exist, returning an error if it does.
func ensureFileNotExist(fileHandler file.Handler, fileName string) error {
	if _, err := fileHandler.Stat(fileName); err != nil {
		if !os.IsNotExist(err) {
			return fmt.Errorf("checking %q: %w", fileName, err)
		}
		return nil
	}
	return fmt.Errorf("%q already exists", fileName)
}