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db.go
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db.go
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package db
import (
"context"
"errors"
"log"
"os"
"strings"
"github.com/aws/aws-sdk-go-v2/aws"
"github.com/aws/aws-sdk-go-v2/config"
"github.com/aws/aws-sdk-go-v2/feature/dynamodb/expression"
"github.com/aws/aws-sdk-go-v2/service/dynamodb"
"github.com/aws/aws-sdk-go-v2/service/dynamodb/types"
"github.com/google/uuid"
)
var client *dynamodb.Client
// table - shortcode(S, primary key)
const longURLDynamoDBAttributeName = "longurl"
const shortCodeDynamoDBAttributeName = "shortcode"
const activeDynamoDBAttributeName = "active"
var ErrUrlNotFound = errors.New("url not found")
var ErrUrlNotActive = errors.New("url not active")
var table string
func init() {
table = os.Getenv("TABLE_NAME")
if table == "" {
log.Fatal("missing environment variable TABLE_NAME")
}
cfg, _ := config.LoadDefaultConfig(context.Background())
client = dynamodb.NewFromConfig(cfg)
}
func SaveURL(longurl string) (string, error) {
shortCode := uuid.New().String()[:8]
log.Println("short code", shortCode)
item := make(map[string]types.AttributeValue)
item[longURLDynamoDBAttributeName] = &types.AttributeValueMemberS{Value: longurl}
item[shortCodeDynamoDBAttributeName] = &types.AttributeValueMemberS{Value: shortCode}
item[activeDynamoDBAttributeName] = &types.AttributeValueMemberBOOL{Value: true}
_, err := client.PutItem(context.Background(), &dynamodb.PutItemInput{
TableName: aws.String(table),
Item: item})
if err != nil {
log.Println("dynamodb put item failed")
return "", err
}
log.Printf("short url for %s - %s\n", longurl, shortCode)
return shortCode, nil
}
func GetLongURL(shortCode string) (string, error) {
op, err := client.GetItem(context.Background(), &dynamodb.GetItemInput{
TableName: aws.String(table),
Key: map[string]types.AttributeValue{
shortCodeDynamoDBAttributeName: &types.AttributeValueMemberS{Value: shortCode}}})
if err != nil {
log.Println("failed to get long url", err)
return "", err
}
if op.Item == nil {
return "", ErrUrlNotFound
}
activeAV := op.Item[activeDynamoDBAttributeName]
active := activeAV.(*types.AttributeValueMemberBOOL).Value
if !active {
return "", ErrUrlNotActive
}
longurlAV := op.Item[longURLDynamoDBAttributeName]
longurl := longurlAV.(*types.AttributeValueMemberS).Value
log.Println("long url", longurl)
return longurl, nil
}
// Update enables or disables a short url
func Update(shortCode string, status bool) error {
update := expression.Set(expression.Name(activeDynamoDBAttributeName), expression.Value(status))
updateExpression, _ := expression.NewBuilder().WithUpdate(update).Build()
condition := expression.AttributeExists(expression.Name(shortCodeDynamoDBAttributeName))
conditionExpression, _ := expression.NewBuilder().WithCondition(condition).Build()
_, err := client.UpdateItem(context.Background(), &dynamodb.UpdateItemInput{
TableName: aws.String(table),
Key: map[string]types.AttributeValue{
shortCodeDynamoDBAttributeName: &types.AttributeValueMemberS{Value: shortCode}},
UpdateExpression: updateExpression.Update(),
ExpressionAttributeNames: updateExpression.Names(),
ExpressionAttributeValues: updateExpression.Values(),
ConditionExpression: conditionExpression.Condition(),
})
if err != nil && strings.Contains(err.Error(), "ConditionalCheckFailedException") {
return ErrUrlNotFound
}
return err
}
// Delete removes a short url from the table
func Delete(shortCode string) error {
condition := expression.AttributeExists(expression.Name(shortCodeDynamoDBAttributeName))
conditionExpression, _ := expression.NewBuilder().WithCondition(condition).Build()
_, err := client.DeleteItem(context.Background(), &dynamodb.DeleteItemInput{
TableName: aws.String(table),
Key: map[string]types.AttributeValue{
shortCodeDynamoDBAttributeName: &types.AttributeValueMemberS{Value: shortCode}},
ConditionExpression: conditionExpression.Condition(),
ExpressionAttributeNames: conditionExpression.Names(),
ExpressionAttributeValues: conditionExpression.Values()})
if err != nil && strings.Contains(err.Error(), "ConditionalCheckFailedException") {
return ErrUrlNotFound
}
return err
}