Added db query interface and moved memory database

db_query_interface.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+  "fmt"
+  "bufio"
+  "strings"
+  "os"
+  "errors"
+  "encoding/hex"
+)
+
+type DbInterface struct {
+  db *MemDatabase
+  trie *Trie
+}
+
+func NewDBInterface() *DbInterface {
+  db, _ := NewMemDatabase()
+  trie := NewTrie(db, "")
+
+  return &DbInterface{db: db, trie: trie}
+}
+
+func (i *DbInterface) ValidateInput(action string, argumentLength int) error {
+  err := false
+  var expArgCount int
+
+  switch {
+  case action == "update" && argumentLength != 2:
+    err = true
+    expArgCount = 2
+  case action == "get" && argumentLength != 1:
+    err = true
+    expArgCount = 1
+  case (action == "quit" || action == "exit") && argumentLength != 0:
+    err = true
+    expArgCount = 0
+  }
+
+  if err {
+    return errors.New(fmt.Sprintf("'%s' requires %d args, got %d", action, expArgCount, argumentLength))
+  } else {
+    return nil
+  }
+}
+
+func (i *DbInterface) ParseInput(input string) bool {
+  scanner := bufio.NewScanner(strings.NewReader(input))
+  scanner.Split(bufio.ScanWords)
+
+  count := 0
+  var tokens []string
+  for scanner.Scan() {
+    count++
+    tokens = append(tokens, scanner.Text())
+  }
+  if err := scanner.Err(); err != nil {
+    fmt.Fprintln(os.Stderr, "reading input:", err)
+  }
+
+  if len(tokens) == 0 { return true }
+
+  err := i.ValidateInput(tokens[0], count-1)
+  if err != nil {
+    fmt.Println(err)
+  } else  {
+    switch tokens[0] {
+    case "update":
+      i.trie.Update(tokens[1], tokens[2])
+
+      fmt.Println(hex.EncodeToString([]byte(i.trie.root)))
+    case "get":
+      fmt.Println(i.trie.Get(tokens[1]))
+    case "exit", "quit", "q":
+      return false
+    default:
+      fmt.Println("Unknown command:", tokens[0])
+    }
+  }
+
+  return true
+}
+
+func (i *DbInterface) Start() {
+  reader := bufio.NewReader(os.Stdin)
+  for {
+    fmt.Printf("db >>> ")
+    str, _, err := reader.ReadLine()
+    if err != nil {
+      fmt.Println("Error reading input", err)
+    } else {
+      if !i.ParseInput(string(str)) {
+        return
+      }
+    }
+  }
+}