sklad: move the database into its own file
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parent
3fe6d7d071
commit
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GPG Key ID:
A0420B94F92B9493
149
sklad/db.go
Normal file
149
sklad/db.go
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@ -0,0 +1,149 @@
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package main
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import (
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"os"
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)
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type Series struct {
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Prefix string // PK: prefix
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Description string // what kind of containers this is for
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}
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type Container struct {
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Series string // PK: what series does this belong to
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Number uint // PK: order within the series
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Parent ContainerId // the container we're in, if any, otherwise ""
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Description string // description and/or contents of this container
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}
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type ContainerId string
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func (c *Container) Id() ContainerId {
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return ContainerId(fmt.Sprintf("%s%s%d", db.Prefix, c.Series, c.Number))
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}
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type Database struct {
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Password string // password for web users
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Prefix string // prefix for all container IDs
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Series []*Series // all known series
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Containers []*Container // all known containers
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}
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var (
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dbPath string
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db Database
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dbLast Database
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dbLog io.Writer
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indexSeries = map[string]*Series{}
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indexContainer = map[ContainerId]*Container{}
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indexChildren = map[ContainerId][]*Container{}
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)
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// TODO: Some functions to add, remove and change things in the database.
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// Indexes must be kept valid, just like any invariants.
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// TODO: A function for fulltext search in series (1. Prefix, 2. Description).
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// TODO: A function for fulltext search in containers (1. Id, 2. Description).
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func dbCommit() error {
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// Back up the current database contents.
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e := json.NewEncoder(dbLog)
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e.SetIndent("", " ")
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if err := e.Encode(&dbLast); err != nil {
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return err
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}
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// Atomically replace the current database file.
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tempPath := dbPath + ".new"
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temp, err := os.OpenFile(tempPath, os.O_WRONLY|os.O_CREATE, 0644)
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if err != nil {
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return err
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}
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defer temp.Close()
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e = json.NewEncoder(temp)
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e.SetIndent("", " ")
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if err := e.Encode(&db); err != nil {
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return err
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}
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if err := os.Rename(tempPath, dbPath); err != nil {
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return err
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}
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dbLast = db
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return nil
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}
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// loadDatabase loads the database from a simple JSON file. We do not use
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// any SQL stuff or even external KV storage because there is no real need
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// for our trivial use case, with our general amount of data.
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func loadDatabase() error {
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dbFile, err := os.Open(dbPath)
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if err != nil {
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return err
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}
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if err := json.NewDecoder(dbFile).Decode(&db); err != nil {
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return err
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}
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// Further validate the database.
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if db.Prefix == "" {
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return errors.New("misconfigured prefix")
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}
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// Construct indexes for primary keys, validate against duplicates.
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for _, pv := range db.Series {
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if _, ok := indexSeries[pv.Prefix]; ok {
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return fmt.Errorf("duplicate series: %s", pv.Prefix)
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}
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indexSeries[pv.Prefix] = pv
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}
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for _, pv := range db.Containers {
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id := pv.Id()
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if _, ok := indexContainer[id]; ok {
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return fmt.Errorf("duplicate container: %s", id)
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}
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indexContainer[id] = pv
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}
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// Construct an index that goes from parent containers to their children.
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for _, pv := range db.Containers {
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if pv.Parent == "" {
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continue
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}
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if _, ok := indexContainer[pv.Parent]; !ok {
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return fmt.Errorf("container %s has a nonexistent parent %s",
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pv.Id(), pv.Parent)
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}
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indexChildren[pv.Parent] = append(indexChildren[pv.Parent], pv)
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}
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// Validate that no container is a parent of itself on any level.
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for _, pv := range db.Containers {
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parents := map[ContainerId]bool{pv.Id(): true}
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for pv.Parent != "" {
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if parents[pv.Parent] {
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return fmt.Errorf("%s contains itself", pv.Parent)
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}
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parents[pv.Parent] = true
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pv = indexContainer[pv.Parent]
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}
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}
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// Open database log file for appending.
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if dbLog, err = os.OpenFile(dbPath+".log",
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os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644); err != nil {
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return err
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}
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// Remember the current state of the database.
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dbLast = db
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return nil
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}
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143
sklad/main.go
143
sklad/main.go
@ -1,155 +1,19 @@
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package main
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import (
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"encoding/json"
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"errors"
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"fmt"
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"html/template"
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"io"
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"log"
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"net/http"
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"os"
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)
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type Series struct {
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Prefix string // PK: prefix
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Description string // what kind of containers this is for
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}
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type Container struct {
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Series string // PK: what series does this belong to
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Number uint // PK: order within the series
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Parent ContainerId // the container we're in, if any, otherwise ""
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Description string // description and/or contents of this container
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}
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type ContainerId string
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func (c *Container) Id() ContainerId {
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return ContainerId(fmt.Sprintf("%s%s%d", db.Prefix, c.Series, c.Number))
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}
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type Database struct {
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Password string // password for web users
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Prefix string // prefix for all container IDs
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Series []*Series // all known series
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Containers []*Container // all known containers
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}
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var (
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templates *template.Template
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// TODO: Some kind of session storage, somewhere.
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dbPath string
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db Database
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dbLast Database
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dbLog io.Writer
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indexSeries = map[string]*Series{}
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indexContainer = map[ContainerId]*Container{}
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indexChildren = map[ContainerId][]*Container{}
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// session storage: UUID -> net.SplitHostPort(http.Server.RemoteAddr)[0]
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sessions = map[string]string{}
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)
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// TODO: Some functions to add, remove and change things in the database.
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// Indexes must be kept valid, just like any invariants.
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func dbCommit() error {
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// Back up the current database contents.
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e := json.NewEncoder(dbLog)
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e.SetIndent("", " ")
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if err := e.Encode(&dbLast); err != nil {
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return err
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}
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// Atomically replace the current database file.
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tempPath := dbPath + ".new"
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temp, err := os.OpenFile(tempPath, os.O_WRONLY|os.O_CREATE, 0644)
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if err != nil {
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return err
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}
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defer temp.Close()
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e = json.NewEncoder(temp)
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e.SetIndent("", " ")
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if err := e.Encode(&db); err != nil {
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return err
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}
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if err := os.Rename(tempPath, dbPath); err != nil {
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return err
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}
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dbLast = db
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return nil
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}
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// loadDatabase loads the database from a simple JSON file. We do not use
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// any SQL stuff or even external KV storage because there is no real need
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// for our trivial use case, with our general amount of data.
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func loadDatabase() error {
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dbFile, err := os.Open(dbPath)
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if err != nil {
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return err
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}
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if err := json.NewDecoder(dbFile).Decode(&db); err != nil {
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return err
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}
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// Further validate the database.
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if db.Prefix == "" {
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return errors.New("misconfigured prefix")
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}
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// Construct indexes for primary keys, validate against duplicates.
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for _, pv := range db.Series {
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if _, ok := indexSeries[pv.Prefix]; ok {
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return fmt.Errorf("duplicate series: %s", pv.Prefix)
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}
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indexSeries[pv.Prefix] = pv
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}
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for _, pv := range db.Containers {
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id := pv.Id()
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if _, ok := indexContainer[id]; ok {
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return fmt.Errorf("duplicate container: %s", id)
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}
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indexContainer[id] = pv
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}
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// Construct an index that goes from parent containers to their children.
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for _, pv := range db.Containers {
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if pv.Parent == "" {
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continue
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}
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if _, ok := indexContainer[pv.Parent]; !ok {
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return fmt.Errorf("container %s has a nonexistent parent %s",
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pv.Id(), pv.Parent)
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}
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indexChildren[pv.Parent] = append(indexChildren[pv.Parent], pv)
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}
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// Validate that no container is a parent of itself on any level.
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for _, pv := range db.Containers {
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parents := map[ContainerId]bool{pv.Id(): true}
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for pv.Parent != "" {
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if parents[pv.Parent] {
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return fmt.Errorf("%s contains itself", pv.Parent)
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}
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parents[pv.Parent] = true
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pv = indexContainer[pv.Parent]
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}
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}
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// Open database log file for appending.
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if dbLog, err = os.OpenFile(dbPath+".log",
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os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644); err != nil {
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return err
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}
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// Remember the current state of the database.
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dbLast = db
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return nil
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}
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func main() {
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if len(os.Args) != 3 {
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log.Fatalf("usage: %s ADDRESS DATABASE\n", os.Args[0])
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@ -170,6 +34,9 @@ func main() {
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log.Fatalln(err)
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}
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// TODO: Eventually we will need to load a font file for label printing.
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// - The path might be part of configuration, or implicit by filename.
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// TODO: Some routing, don't forget about sessions.
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// - https://stackoverflow.com/a/33880971/76313
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//
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