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| -rw-r--r-- | sklad/main.go | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/sklad/main.go b/sklad/main.go new file mode 100644 index 0000000..28fb258 --- /dev/null +++ b/sklad/main.go @@ -0,0 +1,186 @@ +package main + +import ( + "encoding/json" + "errors" + "fmt" + "html/template" + "io" + "log" + "net/http" + "os" +) + +type Series struct { + Prefix string // PK: prefix + Description string // what kind of containers this is for +} + +type Container struct { + Series string // PK: what series does this belong to + Number uint // PK: order within the series + Parent ContainerId // the container we're in, if any, otherwise "" + Description string // description and/or contents of this container +} + +type ContainerId string + +func (c *Container) Id() ContainerId { + return ContainerId(fmt.Sprintf("%s%s%d", db.Prefix, c.Series, c.Number)) +} + +type Database struct { + Password string // password for web users + Prefix string // prefix for all container IDs + Series []*Series // all known series + Containers []*Container // all known containers +} + +var ( + templates *template.Template + // TODO: Some kind of session storage, somewhere. + + dbPath string + db Database + dbLast Database + dbLog io.Writer + + indexSeries = map[string]*Series{} + indexContainer = map[ContainerId]*Container{} + indexChildren = map[ContainerId][]*Container{} +) + +// TODO: Some functions to add, remove and change things in the database. +// Indexes must be kept valid, just like any invariants. + +func dbCommit() error { + // Back up the current database contents. + e := json.NewEncoder(dbLog) + e.SetIndent("", " ") + if err := e.Encode(&dbLast); err != nil { + return err + } + + // Atomically replace the current database file. + tempPath := dbPath + ".new" + temp, err := os.OpenFile(tempPath, os.O_WRONLY|os.O_CREATE, 0644) + if err != nil { + return err + } + defer temp.Close() + + e = json.NewEncoder(temp) + e.SetIndent("", " ") + if err := e.Encode(&db); err != nil { + return err + } + + if err := os.Rename(tempPath, dbPath); err != nil { + return err + } + + dbLast = db + return nil +} + +// loadDatabase loads the database from a simple JSON file. We do not use +// any SQL stuff or even external KV storage because there is no real need +// for our trivial use case, with our general amount of data. +func loadDatabase() error { + dbFile, err := os.Open(dbPath) + if err != nil { + return err + } + if err := json.NewDecoder(dbFile).Decode(&db); err != nil { + return err + } + + // Further validate the database. + if db.Prefix == "" { + return errors.New("misconfigured prefix") + } + + // Construct indexes for primary keys, validate against duplicates. + for _, pv := range db.Series { + if _, ok := indexSeries[pv.Prefix]; ok { + return fmt.Errorf("duplicate series: %s", pv.Prefix) + } + indexSeries[pv.Prefix] = pv + } + for _, pv := range db.Containers { + id := pv.Id() + if _, ok := indexContainer[id]; ok { + return fmt.Errorf("duplicate container: %s", id) + } + indexContainer[id] = pv + } + + // Construct an index that goes from parent containers to their children. + for _, pv := range db.Containers { + if pv.Parent == "" { + continue + } + if _, ok := indexContainer[pv.Parent]; !ok { + return fmt.Errorf("container %s has a nonexistent parent %s", + pv.Id(), pv.Parent) + } + indexChildren[pv.Parent] = append(indexChildren[pv.Parent], pv) + } + + // Validate that no container is a parent of itself on any level. + for _, pv := range db.Containers { + parents := map[ContainerId]bool{pv.Id(): true} + for pv.Parent != "" { + if parents[pv.Parent] { + return fmt.Errorf("%s contains itself", pv.Parent) + } + parents[pv.Parent] = true + pv = indexContainer[pv.Parent] + } + } + + // Open database log file for appending. + if dbLog, err = os.OpenFile(dbPath+".log", + os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644); err != nil { + return err + } + + // Remember the current state of the database. + dbLast = db + return nil +} + +func main() { + if len(os.Args) != 3 { + log.Fatalf("usage: %s ADDRESS DATABASE\n", os.Args[0]) + } + + var address string + address, dbPath = os.Args[1], os.Args[2] + + // Load database. + if err := loadDatabase(); err != nil { + log.Fatalln(err) + } + + // Load HTML templates from the current working directory. + var err error + templates, err = template.ParseGlob("*.tmpl") + if err != nil { + log.Fatalln(err) + } + + // TODO: Some routing, don't forget about sessions. + // - https://stackoverflow.com/a/33880971/76313 + // + // - GET /login + // - GET /container?id=UA1 + // - GET /series?id=A + // - GET /search?q=bottle + // + // - POST /login?pass=hue + // - POST /logout + // - POST /label?id=UA1 + + log.Fatalln(http.ListenAndServe(address, nil)) +} |