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iterator.go
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/
iterator.go
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// Copyright 2023 The PipeCD Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package mysql
import (
"database/sql"
"encoding/base64"
"encoding/json"
"strings"
"github.com/pipe-cd/pipecd/pkg/datastore"
)
type dataConverter interface {
Data() map[string]interface{}
}
// Iterator for MySQL result set
type Iterator struct {
rows *sql.Rows
orders []datastore.Order
last dataConverter
}
// Next implementation for MySQL Iterator
func (it *Iterator) Next(dst interface{}) error {
if !it.rows.Next() {
return datastore.ErrIteratorDone
}
var val string
err := it.rows.Scan(&val)
if err != nil {
return err
}
// Update last iterated item as last read row.
it.last = &rowDataConverter{val: val}
return decodeJSONValue(val, dst)
}
// Cursor builds a base64 string (encode from string in map[string]interface{} format).
// The cursor contains only values attached with the fields used
// as ordering fields.
func (it *Iterator) Cursor() (string, error) {
if it.last == nil {
return "", datastore.ErrInvalidCursor
}
lastObjData := it.last.Data()
cursor := make(map[string]interface{}, len(it.orders))
for _, o := range it.orders {
val, ok := lastObjData[o.Field]
if !ok {
return "", datastore.ErrInvalidCursor
}
// TODO: Support build cursor from nested Ordering field.
cursor[o.Field] = val
}
b, _ := json.Marshal(cursor)
return base64.StdEncoding.EncodeToString(b), nil
}
type rowDataConverter struct {
val string
}
// Data make JSON object with key in CamelCase format.
func (r *rowDataConverter) Data() map[string]interface{} {
jsonRaw := convertKeys(json.RawMessage(r.val), convertSnakeToCamel)
obj := make(map[string]interface{})
json.Unmarshal(jsonRaw, &obj)
return obj
}
// convertKeys convert all keys of json object with convert function.
func convertKeys(j json.RawMessage, convertFunc func(string) string) json.RawMessage {
m := make(map[string]json.RawMessage)
if err := json.Unmarshal([]byte(j), &m); err != nil {
// Not a JSON object
return j
}
for k, v := range m {
fixed := convertFunc(k)
delete(m, k)
m[fixed] = convertKeys(v, convertFunc)
}
b, err := json.Marshal(m)
if err != nil {
return j
}
return json.RawMessage(b)
}
func convertSnakeToCamel(key string) string {
var out string
isToUpper := true
for _, v := range key {
if isToUpper {
out += strings.ToUpper(string(v))
isToUpper = false
continue
}
if v == '_' {
isToUpper = true
continue
}
out += string(v)
}
return out
}