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package objx
import (
"regexp"
"strconv"
"strings"
)
const (
// PathSeparator is the character used to separate the elements
// of the keypath.
//
// For example, `location.address.city`
PathSeparator string = "."
// arrayAccesRegexString is the regex used to extract the array number
// from the access path
arrayAccesRegexString = `^(.+)\[([0-9]+)\]$`
)
// arrayAccesRegex is the compiled arrayAccesRegexString
var arrayAccesRegex = regexp.MustCompile(arrayAccesRegexString)
// Get gets the value using the specified selector and
// returns it inside a new Obj object.
//
// If it cannot find the value, Get will return a nil
// value inside an instance of Obj.
//
// Get can only operate directly on map[string]interface{} and []interface.
//
// Example
//
// To access the title of the third chapter of the second book, do:
//
// o.Get("books[1].chapters[2].title")
func (m Map) Get(selector string) *Value {
rawObj := access(m, selector, nil, false)
return &Value{data: rawObj}
}
// Set sets the value using the specified selector and
// returns the object on which Set was called.
//
// Set can only operate directly on map[string]interface{} and []interface
//
// Example
//
// To set the title of the third chapter of the second book, do:
//
// o.Set("books[1].chapters[2].title","Time to Go")
func (m Map) Set(selector string, value interface{}) Map {
access(m, selector, value, true)
return m
}
// getIndex returns the index, which is hold in s by two braches.
// It also returns s withour the index part, e.g. name[1] will return (1, name).
// If no index is found, -1 is returned
func getIndex(s string) (int, string) {
arrayMatches := arrayAccesRegex.FindStringSubmatch(s)
if len(arrayMatches) > 0 {
// Get the key into the map
selector := arrayMatches[1]
// Get the index into the array at the key
// We know this cannt fail because arrayMatches[2] is an int for sure
index, _ := strconv.Atoi(arrayMatches[2])
return index, selector
}
return -1, s
}
// access accesses the object using the selector and performs the
// appropriate action.
func access(current interface{}, selector string, value interface{}, isSet bool) interface{} {
selSegs := strings.SplitN(selector, PathSeparator, 2)
thisSel := selSegs[0]
index := -1
if strings.Contains(thisSel, "[") {
index, thisSel = getIndex(thisSel)
}
if curMap, ok := current.(Map); ok {
current = map[string]interface{}(curMap)
}
// get the object in question
switch current.(type) {
case map[string]interface{}:
curMSI := current.(map[string]interface{})
if len(selSegs) <= 1 && isSet {
curMSI[thisSel] = value
return nil
}
current = curMSI[thisSel]
default:
current = nil
}
// do we need to access the item of an array?
if index > -1 {
if array, ok := current.([]interface{}); ok {
if index < len(array) {
current = array[index]
} else {
current = nil
}
}
}
if len(selSegs) > 1 {
current = access(current, selSegs[1], value, isSet)
}
return current
}
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