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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
}
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
case "help":
fmt.Println(`query commands:
update KEY VALUE
get KEY
`)
default:
fmt.Println("Unknown command:", tokens[0])
}
}
return true
}
func (i *DbInterface) Start() {
fmt.Printf("DB Query tool. Type (help) for help\n")
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
}
}
}
}
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