package snapshot

import (
	"os"
	"path/filepath"

	"github.com/spf13/afero"
	"go.uber.org/fx"
	"sneak.berlin/go/vaultik/internal/config"
	"sneak.berlin/go/vaultik/internal/database"
	"sneak.berlin/go/vaultik/internal/pidlock"
	"sneak.berlin/go/vaultik/internal/storage"
	"sneak.berlin/go/vaultik/internal/ui"
)

// ScannerParams holds parameters for scanner creation
type ScannerParams struct {
	EnableProgress bool
	UI             *ui.Writer // Where user-facing scanner messages go; nil = discard
	Fs             afero.Fs
	Exclude        []string // Exclude patterns (combined global + snapshot-specific)
	SkipErrors     bool     // Skip file read errors (log loudly but continue)
	// PreviousSnapshotID is the most recent completed snapshot of the
	// same name, "" for none.
	PreviousSnapshotID string
	// DeviceNumber is ScannerConfig.DeviceNumber; nil reads it from the
	// file's stat.
	DeviceNumber func(info os.FileInfo) (uint64, bool)
}

// Module exports backup functionality as an fx module.
// It provides a ScannerFactory that can create Scanner instances
// with custom parameters while sharing common dependencies.
//
//nolint:gochecknoglobals // fx module definitions are conventionally globals
var Module = fx.Module("backup",
	fx.Provide(
		provideScannerFactory,
		NewSnapshotManager,
	),
)

// ScannerFactory creates scanners with custom parameters
type ScannerFactory func(params ScannerParams) *Scanner

func provideScannerFactory(
	cfg *config.Config, repos *database.Repositories, storer storage.Storer,
) ScannerFactory {
	return func(params ScannerParams) *Scanner {
		// Use provided excludes, or fall back to global config excludes
		excludes := params.Exclude
		if len(excludes) == 0 {
			excludes = cfg.Exclude
		}

		return NewScanner(ScannerConfig{
			FS:                 params.Fs,
			ChunkSize:          cfg.ChunkSize.Int64(),
			Repositories:       repos,
			Storage:            storer,
			MaxBlobSize:        cfg.BlobSizeLimit.Int64(),
			CompressionLevel:   cfg.CompressionLevel,
			AgeRecipients:      cfg.AgeRecipients,
			EnableProgress:     params.EnableProgress,
			UI:                 params.UI,
			Exclude:            excludes,
			IndexAndLockFiles:  indexAndLockFiles(cfg.IndexPath, pidlock.Dir()),
			SkipErrors:         params.SkipErrors,
			PreviousSnapshotID: params.PreviousSnapshotID,
			DeviceNumber:       params.DeviceNumber,
		})
	}
}

// indexAndLockFiles returns the paths of the index at indexPath, its side
// files and the PID file in lockDir. Symlinks in their directories are
// resolved, as they are in the snapshot's source paths, so the scan finds
// them under the same names. If indexPath is a symlink, the file it points
// to and that file's side files are returned too.
func indexAndLockFiles(indexPath, lockDir string) []string {
	paths := append(database.IndexFiles(indexPath), pidlock.Path(lockDir))
	for i, p := range paths {
		paths[i] = resolveParentDir(p)
	}

	// SQLite writes the file a symlinked index points to and keeps the
	// side files beside that file. The database package creates the index
	// before the scanner is built, so the link resolves.
	index := resolveParentDir(indexPath)

	target, err := filepath.EvalSymlinks(index)
	if err == nil && target != index {
		paths = append(paths, database.IndexFiles(target)...)
	}

	return paths
}

// resolveParentDir returns the absolute form of path with the symlinks in
// its parent directory resolved. If the parent directory cannot be
// resolved, it returns the absolute form unresolved. If path has no
// absolute form, it returns path.
func resolveParentDir(path string) string {
	abs, err := filepath.Abs(path)
	if err != nil {
		return path
	}

	dir, err := filepath.EvalSymlinks(filepath.Dir(abs))
	if err != nil {
		return abs
	}

	return filepath.Join(dir, filepath.Base(abs))
}