/*
 * Copyright (c) 2020 Baidu, Inc.
 *
 * 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 json

import (
	"bytes"
	stdjson "encoding/json"
	"io"

	jsoniter "github.com/json-iterator/go"
)

var fastjson = jsoniter.ConfigCompatibleWithStandardLibrary

type RawMessage stdjson.RawMessage

type Number stdjson.Number

// NewEncoder delegates to json.NewEncoder
// It is only here so this package can be a drop-in for common encoding/json uses
func NewEncoder(w io.Writer) *jsoniter.Encoder {
	return jsoniter.NewEncoder(w)
}

// NewDecoder delegates to json.NewDecoder
// It is only here so this package can be a drop-in for common encoding/json uses
func NewDecoder(r io.Reader) *jsoniter.Decoder {
	return jsoniter.NewDecoder(r)
}

// Marshal delegates to json.Marshal
// It is only here so this package can be a drop-in for common encoding/json uses
func Marshal(v interface{}) ([]byte, error) {
	return fastjson.Marshal(v)
}

// Unmarshal unmarshals the given data
// If v is a *map[string]interface{}, numbers are converted to int64 or float64
func Unmarshal(data []byte, v interface{}) error {
	switch v := v.(type) {
	case *map[string]interface{}:
		// Build a decoder from the given data
		decoder := jsoniter.NewDecoder(bytes.NewBuffer(data))
		// Preserve numbers, rather than casting to float64 automatically
		decoder.UseNumber()
		// Run the decode
		if err := decoder.Decode(v); err != nil {
			return err
		}
		// If the decode succeeds, post-process the map to convert json.Number objects to int64 or float64
		return convertMapNumbers(*v)

	default:
		return fastjson.Unmarshal(data, v)
	}
}

// convertMapNumbers traverses the map, converting any json.Number values to int64 or float64.
// values which are map[string]interface{} or []interface{} are recursively visited
func convertMapNumbers(m map[string]interface{}) error {
	var err error
	for k, v := range m {
		switch v := v.(type) {
		case stdjson.Number:
			m[k], err = convertNumber(v)
		case map[string]interface{}:
			err = convertMapNumbers(v)
		case []interface{}:
			err = convertSliceNumbers(v)
		}
		if err != nil {
			return err
		}
	}
	return nil
}

// convertSliceNumbers traverses the slice, converting any json.Number values to int64 or float64.
// values which are map[string]interface{} or []interface{} are recursively visited
func convertSliceNumbers(s []interface{}) error {
	var err error
	for i, v := range s {
		switch v := v.(type) {
		case stdjson.Number:
			s[i], err = convertNumber(v)
		case map[string]interface{}:
			err = convertMapNumbers(v)
		case []interface{}:
			err = convertSliceNumbers(v)
		}
		if err != nil {
			return err
		}
	}
	return nil
}

// convertNumber converts a json.Number to an int64 or float64, or returns an error
func convertNumber(n stdjson.Number) (interface{}, error) {
	// Attempt to convert to an int64 first
	if i, err := n.Int64(); err == nil {
		return i, nil
	}
	// Return a float64 (default json.Decode() behavior)
	// An overflow will return an error
	return n.Float64()
}
