//go:build linux

package backup

import (
	"context"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
)

// RestoreAppFromBackup restores a single app from its cross-drive backup.
// Steps: restore config → verify/restore data → copy DB dumps → docker compose up.
func RestoreAppFromBackup(ctx context.Context, app *RestorableApp, stacksDir string, logger *log.Logger) error {
	stackDir := filepath.Join(stacksDir, app.Name)

	// Step 1: Restore stack config from _config/ backup
	if app.HasConfig {
		logger.Printf("[INFO] Restoring config for %s from %s", app.Name, app.ConfigPath)
		if err := restoreConfigDir(ctx, app.ConfigPath, stackDir); err != nil {
			return fmt.Errorf("restoring config: %w", err)
		}
	} else {
		// No config backup — check if stack dir already exists (from catalog sync)
		if !dirExists(stackDir) {
			return fmt.Errorf("no config backup and no stack directory for %s", app.Name)
		}
		logger.Printf("[INFO] No config backup for %s — using existing stack dir", app.Name)
	}

	// Step 2: Verify app data on HDD (common case: HDD survived, data is intact)
	if app.NeedsHDD && !app.HasData && app.HasRsyncData {
		// App data is missing but rsync backup exists — restore it
		logger.Printf("[INFO] Restoring user data for %s from rsync backup", app.Name)
		if err := restoreUserData(ctx, app, logger); err != nil {
			logger.Printf("[WARN] User data restore failed for %s: %v", app.Name, err)
			// Non-fatal: app might still start without all data
		}
	} else if app.HasData {
		logger.Printf("[INFO] App data for %s found at %s — no restore needed", app.Name, app.DataPath)
	}

	// Step 3: Copy DB dumps to primary backup location
	if app.HasDBDump {
		logger.Printf("[INFO] Restoring DB dumps for %s", app.Name)
		if err := restoreDBDumps(app, logger); err != nil {
			logger.Printf("[WARN] DB dump restore failed for %s: %v", app.Name, err)
			// Non-fatal
		}
	}

	// Step 4: Docker compose pull + up
	composePath := filepath.Join(stackDir, "docker-compose.yml")
	if !fileExistsCheck(composePath) {
		composePath = filepath.Join(stackDir, "compose.yml")
		if !fileExistsCheck(composePath) {
			return fmt.Errorf("no compose file found in %s", stackDir)
		}
	}

	composeDir := filepath.Dir(composePath)

	logger.Printf("[INFO] Pulling images for %s", app.Name)
	pullCmd := exec.CommandContext(ctx, "docker", "compose", "-f", composePath, "pull")
	pullCmd.Dir = composeDir
	if out, err := pullCmd.CombinedOutput(); err != nil {
		logger.Printf("[WARN] docker compose pull failed for %s: %v (%s)", app.Name, err, strings.TrimSpace(string(out)))
		// Non-fatal: might work with cached images
	}

	logger.Printf("[INFO] Starting %s", app.Name)
	upCmd := exec.CommandContext(ctx, "docker", "compose", "-f", composePath, "up", "-d")
	upCmd.Dir = composeDir
	if out, err := upCmd.CombinedOutput(); err != nil {
		return fmt.Errorf("docker compose up: %v (%s)", err, strings.TrimSpace(string(out)))
	}

	return nil
}

// restoreConfigDir rsyncs the backed-up _config/ directory to the stack directory.
func restoreConfigDir(ctx context.Context, configBackupDir, stackDir string) error {
	if err := os.MkdirAll(stackDir, 0755); err != nil {
		return fmt.Errorf("creating stack dir: %w", err)
	}

	src := strings.TrimRight(configBackupDir, "/") + "/"
	dst := strings.TrimRight(stackDir, "/") + "/"

	cmd := exec.CommandContext(ctx, "rsync", "-a", src, dst)
	if out, err := cmd.CombinedOutput(); err != nil {
		return fmt.Errorf("rsync config: %v (%s)", err, strings.TrimSpace(string(out)))
	}
	return nil
}

// restoreUserData rsyncs user data from cross-drive backup back to the app's HDD path.
func restoreUserData(ctx context.Context, app *RestorableApp, logger *log.Logger) error {
	if app.RsyncDataPath == "" || app.HDDPath == "" {
		return fmt.Errorf("no rsync data path or HDD path")
	}

	// The rsync backup contains the app's data directories.
	// Walk the backup dir and rsync each subdirectory (excluding _config/_db)
	// back to the app's HDD data directory.
	entries, err := os.ReadDir(app.RsyncDataPath)
	if err != nil {
		return err
	}

	dataDir := AppDataDir(app.HDDPath, app.Name)
	if err := os.MkdirAll(dataDir, 0755); err != nil {
		return fmt.Errorf("creating data dir: %w", err)
	}

	for _, e := range entries {
		name := e.Name()
		if name == "_config" || name == "_db" || strings.HasPrefix(name, ".") {
			continue
		}

		src := filepath.Join(app.RsyncDataPath, name)
		dst := filepath.Join(dataDir, name)

		if e.IsDir() {
			src = strings.TrimRight(src, "/") + "/"
			if err := os.MkdirAll(dst, 0755); err != nil {
				logger.Printf("[WARN] Cannot create %s: %v", dst, err)
				continue
			}
			dst = strings.TrimRight(dst, "/") + "/"
			cmd := exec.CommandContext(ctx, "rsync", "-a", src, dst)
			if out, err := cmd.CombinedOutput(); err != nil {
				logger.Printf("[WARN] rsync data %s: %v (%s)", name, err, strings.TrimSpace(string(out)))
			}
		} else {
			// Single file — copy directly
			data, err := os.ReadFile(src)
			if err != nil {
				logger.Printf("[WARN] Cannot read %s: %v", src, err)
				continue
			}
			if err := os.WriteFile(dst, data, 0644); err != nil {
				logger.Printf("[WARN] Cannot write %s: %v", dst, err)
			}
		}
	}

	return nil
}

// restoreDBDumps copies DB dump files from cross-drive backup to the primary dump dir.
func restoreDBDumps(app *RestorableApp, logger *log.Logger) error {
	if app.DBDumpPath == "" {
		return nil
	}

	// Use HDDPath for apps with HDD data, fall back to DrivePath (system data path)
	// for SSD-only apps whose DB dumps live under the system drive.
	drivePath := app.HDDPath
	if drivePath == "" {
		drivePath = app.DrivePath
	}
	if drivePath == "" {
		logger.Printf("[WARN] Cannot restore DB dumps for %s: no drive path", app.Name)
		return nil
	}

	destDir := AppDBDumpPath(drivePath, app.Name)
	if err := os.MkdirAll(destDir, 0755); err != nil {
		return fmt.Errorf("creating dump dir: %w", err)
	}

	entries, err := os.ReadDir(app.DBDumpPath)
	if err != nil {
		return err
	}

	for _, e := range entries {
		if e.IsDir() {
			continue
		}
		src := filepath.Join(app.DBDumpPath, e.Name())
		dst := filepath.Join(destDir, e.Name())
		data, err := os.ReadFile(src)
		if err != nil {
			logger.Printf("[WARN] Cannot read dump %s: %v", e.Name(), err)
			continue
		}
		if err := os.WriteFile(dst, data, 0644); err != nil {
			logger.Printf("[WARN] Cannot write dump %s: %v", e.Name(), err)
		}
	}

	return nil
}

// fileExistsCheck returns true if path exists and is a file.
func fileExistsCheck(path string) bool {
	info, err := os.Stat(path)
	return err == nil && !info.IsDir()
}