cloudflared-mirror/dbconnect/client.go

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package dbconnect
import (
"context"
"encoding/json"
"fmt"
"net/url"
"strings"
"time"
"unicode"
"unicode/utf8"
)
// Client is an interface to talk to any database.
//
// Currently, the only implementation is SQLClient, but its structure
// should be designed to handle a MongoClient or RedisClient in the future.
type Client interface {
Ping(context.Context) error
Submit(context.Context, *Command) (interface{}, error)
}
// NewClient creates a database client based on its URL scheme.
func NewClient(ctx context.Context, originURL *url.URL) (Client, error) {
return NewSQLClient(ctx, originURL)
}
// Command is a standard, non-vendor format for submitting database commands.
//
// When determining the scope of this struct, refer to the following litmus test:
// Could this (roughly) conform to SQL, Document-based, and Key-value command formats?
type Command struct {
Statement string `json:"statement"`
Arguments Arguments `json:"arguments,omitempty"`
Mode string `json:"mode,omitempty"`
Isolation string `json:"isolation,omitempty"`
Timeout time.Duration `json:"timeout,omitempty"`
}
// Validate enforces the contract of Command: non empty statement (both in length and logic),
// lowercase mode and isolation, non-zero timeout, and valid Arguments.
func (cmd *Command) Validate() error {
if cmd.Statement == "" {
return fmt.Errorf("cannot provide an empty statement")
}
if strings.Map(func(char rune) rune {
if char == ';' || unicode.IsSpace(char) {
return -1
}
return char
}, cmd.Statement) == "" {
return fmt.Errorf("cannot provide a statement with no logic: '%s'", cmd.Statement)
}
cmd.Mode = strings.ToLower(cmd.Mode)
cmd.Isolation = strings.ToLower(cmd.Isolation)
if cmd.Timeout.Nanoseconds() <= 0 {
cmd.Timeout = 24 * time.Hour
}
return cmd.Arguments.Validate()
}
// UnmarshalJSON converts a byte representation of JSON into a Command, which is also validated.
func (cmd *Command) UnmarshalJSON(data []byte) error {
// Alias is required to avoid infinite recursion from the default UnmarshalJSON.
type Alias Command
alias := &struct {
*Alias
}{
Alias: (*Alias)(cmd),
}
err := json.Unmarshal(data, &alias)
if err == nil {
err = cmd.Validate()
}
return err
}
// Arguments is a wrapper for either map-based or array-based Command arguments.
//
// Each field is mutually-exclusive and some Client implementations may not
// support both fields (eg. MySQL does not accept named arguments).
type Arguments struct {
Named map[string]interface{}
Positional []interface{}
}
// Validate enforces the contract of Arguments: non nil, mutually exclusive, and no empty or reserved keys.
func (args *Arguments) Validate() error {
if args.Named == nil {
args.Named = map[string]interface{}{}
}
if args.Positional == nil {
args.Positional = []interface{}{}
}
if len(args.Named) > 0 && len(args.Positional) > 0 {
return fmt.Errorf("both named and positional arguments cannot be specified: %+v and %+v", args.Named, args.Positional)
}
for key := range args.Named {
if key == "" {
return fmt.Errorf("named arguments cannot contain an empty key: %+v", args.Named)
}
if !utf8.ValidString(key) {
return fmt.Errorf("named argument does not conform to UTF-8 encoding: %s", key)
}
if strings.HasPrefix(key, "_") {
return fmt.Errorf("named argument cannot start with a reserved keyword '_': %s", key)
}
if unicode.IsNumber([]rune(key)[0]) {
return fmt.Errorf("named argument cannot start with a number: %s", key)
}
}
return nil
}
// UnmarshalJSON converts a byte representation of JSON into Arguments, which is also validated.
func (args *Arguments) UnmarshalJSON(data []byte) error {
var obj interface{}
err := json.Unmarshal(data, &obj)
if err != nil {
return err
}
named, ok := obj.(map[string]interface{})
if ok {
args.Named = named
} else {
positional, ok := obj.([]interface{})
if ok {
args.Positional = positional
} else {
return fmt.Errorf("arguments must either be an object {\"0\":\"val\"} or an array [\"val\"]: %s", string(data))
}
}
return args.Validate()
}