package database

import (
	"eden-server/internal/utility"
	"log/slog"
	"os"
	"path/filepath"

	"gorm.io/gorm"
)

func watchdog(env utility.Environment, db *gorm.DB) {
	slog.Info("performing the watchdog cycle")

	fsFiles, err := os.ReadDir(env.ContentDirectory)
	if err != nil {
		slog.Error("failed to read the content directory on the filesystem", "error", err)
		return
	}

	dbFiles, err := GetFiles(db)
	if err != nil {
		slog.Error("failed to retrieve the files indexed from the database", "error", err)
		return
	}

	// generate a set of filesystem contents
	fsSet := make(map[string]struct{}) // cool name for the files that are (now) marked for annihilation
	for _, f := range fsFiles {
		// absolute path creation
		fullPath := filepath.Join(env.ContentDirectory, f.Name())
		fsSet[fullPath] = struct{}{}
	}

	// generate a set of Database contents
	dbSet := make(map[string]File) // cool name for the files that are going to be deregistered from the database
	for _, f := range dbFiles {
		dbSet[f.FilePath] = f
	}

	// FS -> DB
	// check for orphaned filesystem files
	var fsPurgeScroll []string
	for path := range fsSet {
		if _, exists := dbSet[path]; !exists {
			fsPurgeScroll = append(fsPurgeScroll, path)
		}
	}

	// DB -> FS
	// check stale database records
	var dbPurgeScroll []File
	for path, f := range dbSet {
		if _, exists := fsSet[path]; !exists {
			dbPurgeScroll = append(dbPurgeScroll, f)
		}
	}

	if len(fsPurgeScroll) > 0 {
		slog.Info("filesystem purge scroll is populated, engaging purge")
		//filepath is stored in the slice, the filename or file object, see above
		for _, fp := range fsPurgeScroll {
			utility.RemoveFile(fp)
		}
	}

	if len(dbPurgeScroll) > 0 {
		slog.Info("database purge scroll is populated, engaging purge")
		for _, f := range dbPurgeScroll {
			DeregisterFile(db, f)
		}
	}
}