micro/util/qson/qson.go

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// Package qson implmenets decoding of URL query params
// into JSON and Go values (using JSON struct tags).
//
// See https://golang.org/pkg/encoding/json/ for more
// details on JSON struct tags.
package qson
import (
"encoding/json"
"errors"
"net/url"
"regexp"
"strings"
)
var (
// ErrInvalidParam is returned when invalid data is provided to the ToJSON or Unmarshal function.
// Specifically, this will be returned when there is no equals sign present in the URL query parameter.
ErrInvalidParam error = errors.New("qson: invalid url query param provided")
bracketSplitter *regexp.Regexp
)
func init() {
bracketSplitter = regexp.MustCompile("\\[|\\]")
}
func btSplitter(str string) []string {
r := bracketSplitter.Split(str, -1)
for idx, s := range r {
if len(s) == 0 {
if len(r) > idx+1 {
copy(r[idx:], r[idx+1:])
r = r[:len(r)-1]
}
}
}
return r
}
// Unmarshal will take a dest along with URL
// query params and attempt to first turn the query params
// into JSON and then unmarshal those into the dest variable
//
// BUG(joncalhoun): If a URL query param value is something
// like 123 but is expected to be parsed into a string this
// will currently result in an error because the JSON
// transformation will assume this is intended to be an int.
// This should only affect the Unmarshal function and
// could likely be fixed, but someone will need to submit a
// PR if they want that fixed.
func Unmarshal(dst interface{}, query string) error {
b, err := ToJSON(query)
if err != nil {
return err
}
return json.Unmarshal(b, dst)
}
// ToJSON will turn a query string like:
// cat=1&bar%5Bone%5D%5Btwo%5D=2&bar[one][red]=112
// Into a JSON object with all the data merged as nicely as
// possible. Eg the example above would output:
// {"bar":{"one":{"two":2,"red":112}}}
func ToJSON(query string) ([]byte, error) {
var (
builder interface{} = make(map[string]interface{})
)
params := strings.Split(query, "&")
for _, part := range params {
tempMap, err := queryToMap(part)
if err != nil {
return nil, err
}
builder = merge(builder, tempMap)
}
return json.Marshal(builder)
}
// queryToMap turns something like a[b][c]=4 into
// map[string]interface{}{
// "a": map[string]interface{}{
// "b": map[string]interface{}{
// "c": 4,
// },
// },
// }
func queryToMap(param string) (map[string]interface{}, error) {
rawKey, rawValue, err := splitKeyAndValue(param)
if err != nil {
return nil, err
}
rawValue, err = url.QueryUnescape(rawValue)
if err != nil {
return nil, err
}
rawKey, err = url.QueryUnescape(rawKey)
if err != nil {
return nil, err
}
pieces := btSplitter(rawKey)
key := pieces[0]
// If len==1 then rawKey has no [] chars and we can just
// decode this as key=value into {key: value}
if len(pieces) == 1 {
var value interface{}
// First we try parsing it as an int, bool, null, etc
err = json.Unmarshal([]byte(rawValue), &value)
if err != nil {
// If we got an error we try wrapping the value in
// quotes and processing it as a string
err = json.Unmarshal([]byte("\""+rawValue+"\""), &value)
if err != nil {
// If we can't decode as a string we return the err
return nil, err
}
}
return map[string]interface{}{
key: value,
}, nil
}
// If len > 1 then we have something like a[b][c]=2
// so we need to turn this into {"a": {"b": {"c": 2}}}
// To do this we break our key into two pieces:
// a and b[c]
// and then we set {"a": queryToMap("b[c]", value)}
ret := make(map[string]interface{}, 0)
ret[key], err = queryToMap(buildNewKey(rawKey) + "=" + rawValue)
if err != nil {
return nil, err
}
// When URL params have a set of empty brackets (eg a[]=1)
// it is assumed to be an array. This will get us the
// correct value for the array item and return it as an
// []interface{} so that it can be merged properly.
if pieces[1] == "" {
temp := ret[key].(map[string]interface{})
ret[key] = []interface{}{temp[""]}
}
return ret, nil
}
// buildNewKey will take something like:
// origKey = "bar[one][two]"
// pieces = [bar one two ]
// and return "one[two]"
func buildNewKey(origKey string) string {
pieces := btSplitter(origKey)
ret := origKey[len(pieces[0])+1:]
ret = ret[:len(pieces[1])] + ret[len(pieces[1])+1:]
return ret
}
// splitKeyAndValue splits a URL param at the last equal
// sign and returns the two strings. If no equal sign is
// found, the ErrInvalidParam error is returned.
func splitKeyAndValue(param string) (string, string, error) {
li := strings.LastIndex(param, "=")
if li == -1 {
return "", "", ErrInvalidParam
}
return param[:li], param[li+1:], nil
}