fraenky8 / tables-to-go

package objx

import (

	"fmt"

	"regexp"

	"strconv"

	"strings"

)

// arrayAccesRegexString is the regex used to extract the array number

// from the access path

const 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, 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, false)

	return m

}

// access accesses the object using the selector and performs the

// appropriate action.

func access(current, selector, value interface{}, isSet, panics bool) interface{} {

	switch selector.(type) {

	case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:

		if array, ok := current.([]interface{}); ok {

			index := intFromInterface(selector)

			if index >= len(array) {

				if panics {

					panic(fmt.Sprintf("objx: Index %d is out of range. Slice only contains %d items.", index, len(array)))

				}

				return nil

			}

			return array[index]

		}

		return nil

	case string:

		selStr := selector.(string)

		selSegs := strings.SplitN(selStr, PathSeparator, 2)

		thisSel := selSegs[0]

		index := -1

		var err error

		if strings.Contains(thisSel, "[") {

			arrayMatches := arrayAccesRegex.FindStringSubmatch(thisSel)

			if len(arrayMatches) > 0 {

				// Get the key into the map

				thisSel = arrayMatches[1]

				// Get the index into the array at the key

				index, err = strconv.Atoi(arrayMatches[2])

				if err != nil {

					// This should never happen. If it does, something has gone

					// seriously wrong. Panic.

					panic("objx: Array index is not an integer.  Must use array[int].")

				}

			}

		}

		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

		}

		if current == nil && panics {

			panic(fmt.Sprintf("objx: '%v' invalid on object.", selector))

		}

		// 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 {

					if panics {

						panic(fmt.Sprintf("objx: Index %d is out of range. Slice only contains %d items.", index, len(array)))

					}

					current = nil

				}

			}

		}

		if len(selSegs) > 1 {

			current = access(current, selSegs[1], value, isSet, panics)

		}

	}

	return current

}

// intFromInterface converts an interface object to the largest

// representation of an unsigned integer using a type switch and

// assertions

func intFromInterface(selector interface{}) int {

	var value int

	switch selector.(type) {

	case int:

		value = selector.(int)

	case int8:

		value = int(selector.(int8))

	case int16:

		value = int(selector.(int16))

	case int32:

		value = int(selector.(int32))

	case int64:

		value = int(selector.(int64))

	case uint:

		value = int(selector.(uint))

	case uint8:

		value = int(selector.(uint8))

	case uint16:

		value = int(selector.(uint16))

	case uint32:

		value = int(selector.(uint32))

	case uint64:

		value = int(selector.(uint64))

	default:

		panic("objx: array access argument is not an integer type (this should never happen)")

	}

	return value

}