package audit

import (
	"encoding/json"
	"github.com/r3labs/diff/v2"
	"gitlab.com/uafrica/go-utils/reflection"
	"gitlab.com/uafrica/go-utils/string_utils"
	"reflect"
	"regexp"
	"strconv"
	"strings"
)

type FieldChange struct {
	From interface{} `json:"change_from"`
	To   interface{} `json:"change_to"`
}

func GetChanges(original interface{}, new interface{}) (map[string]interface{}, error) {
	changes := map[string]interface{}{}
	changelog, err := diff.Diff(original, new)
	if err != nil {
		return changes, err
	}

	for _, change := range changelog {

		if len(change.Path) == 1 {
			// Root object change
			field := ToSnakeCase(change.Path[0])
			changes[field] = FieldChange{
				From: change.From,
				To:   change.To,
			}
		} else if len(change.Path) == 2 {
			// Child object changed
			// ["Account", "ID"]
			// 0 = Object
			// 1 = field

			objectKey := ToSnakeCase(change.Path[0])
			field := ToSnakeCase(change.Path[1])

			existingObject, present := changes[objectKey]
			if present {
				if object, ok := existingObject.(map[string]interface{}); ok {
					object[field] = FieldChange{
						From: change.From,
						To:   change.To,
					}
					changes[objectKey] = object
				}
			} else {
				fieldChange := map[string]interface{}{
					field: FieldChange{
						From: change.From,
						To:   change.To,
					},
				}
				changes[objectKey] = fieldChange
			}

		} else if len(change.Path) == 3 {
			// Array of objects
			// ["Parcel", "0", "ActualWeight"]
			// 0 = Object
			// 1 = Index of object
			// 2 = field

			objectKey := ToSnakeCase(change.Path[0])
			indexString := change.Path[1]
			index, _ := string_utils.StringToInt64(indexString)
			field := ToSnakeCase(change.Path[2])

			arrayObject, present := changes[objectKey]
			if present {
				if arrayOfObjects, ok := arrayObject.([]map[string]interface{}); ok {
					if len(arrayOfObjects) > int(index) {
						// Add field to existing object in array
						object := arrayOfObjects[index]
						object[field] = FieldChange{
							From: change.From,
							To:   change.To,
						}
					} else {
						// new object, append to existing array
						fieldChange := map[string]interface{}{
							field: FieldChange{
								From: change.From,
								To:   change.To,
							},
						}
						changes[objectKey] = append(arrayOfObjects, fieldChange)
					}

				}
			} else {
				// Create array of objects
				fieldChange := map[string]interface{}{
					field: FieldChange{
						From: change.From,
						To:   change.To,
					},
				}
				changes[objectKey] = []map[string]interface{}{
					fieldChange,
				}
			}
		}
	}

	return changes, nil
}

// GetAllChanges Returns the diff, structured in json, recursively
// Be warned, here be dragons. Debug this first to understand how it works
func GetAllChanges(original interface{}, new interface{}) (map[string]interface{}, error) {
	changes := map[string]interface{}{}
	changelog, err := diff.Diff(original, new)
	if err != nil {
		return changes, err
	}

	changesJson := "{"
	subArrays := map[string]string{}
	for _, change := range changelog {
		var value string   // Keep track of the core value
		var key string     // Keep track of the key/s for this value
		var closing string // Keep track of the correct number of closing characters

		for pathIndex := len(change.Path) - 1; pathIndex >= 0; pathIndex-- {
			// If this is the first value, it's the "deepest" value of this change set, otherwise leave this var alone
			// If this is set at the wrong point, other behaviour changes
			if pathIndex+1 == len(change.Path) {
				changedField := FieldChange{
					From: change.From,
					To:   change.To,
				}
				request, err := json.Marshal(changedField)
				if err != nil {
					return nil, err
				}
				value = string(request)
				value = value[1 : len(value)-1]
			}

			// If this "key" is integer-like, we handle it a little differently to ensure related data ends up
			// together and formatted as you would expect JSON arrays to look
			if _, convErr := strconv.Atoi(change.Path[pathIndex]); convErr == nil {
				positionOfSubArray := ""
				for sub := 0; sub <= pathIndex; sub++ {
					positionOfSubArray = positionOfSubArray + change.Path[sub]
				}

				// Add it to the placeholder data map used later on
				subArrays[positionOfSubArray] = subArrays[positionOfSubArray] + key + value + closing + ","

				// Don't insert the same placeholder into the json multiple times
				if !strings.Contains(changesJson, positionOfSubArray) {
					value = positionOfSubArray
				} else {
					// Make sure this value doesn't end up populated explicitly
					value = ""
				}
			} else {
				// Safety net so we don't compare to a non existant value
				if pathIndex < len(change.Path)-1 {
					// If the value this one "contains" has a integer-like key, this is probably an array
					if _, err = strconv.Atoi(change.Path[pathIndex+1]); err == nil {
						key = "\"" + ToSnakeCase(change.Path[pathIndex]) + "\": ["
						closing = "]"
					} else {
						key = "\"" + ToSnakeCase(change.Path[pathIndex]) + "\": {" + key
						closing = closing + "}"
					}
				} else {
					key = "\"" + ToSnakeCase(change.Path[pathIndex]) + "\": {" + key
					closing = closing + "}"
				}
			}
		}

		// Don't insert empty values (happens when multiple values within an array are set, see "placeholder" behavior)
		if value != "" {
			// Duplicate key prevention
			keySplit := strings.Split(key, ": ")
			lastOccurrence := 0
			lastMatched := ""
			levelsDeep := 0
			for sIndex, split := range keySplit {
				// Trim leading character off split
				if split[0:1] == "{" || split[0:1] == "[" {
					split = split[1:]
				}

				// The final value of keySplit might be empty ("")
				if split != "" {
					if index := strings.Index(changesJson, split); index > -1 && changesJson != "{" {
						// Prevent reverse traversal
						if index > lastOccurrence {
							// Prevent finding nested keys as opposed to our "change" keys
							opener := changesJson[index+len(split)+2 : index+len(split)+3]
							// Prevent a "base level" key from matching a nested key
							baseLevel := false
							if index >= 1 {
								containedBy := changesJson[index-1 : index]
								if levelsDeep == 0 && (containedBy == "{" || containedBy == "[") {
									baseLevel = true
								}
							}
							if (opener == "{" || opener == "[") && !baseLevel {
								lastOccurrence = index
								lastMatched = split
								levelsDeep = sIndex
							}
						}
					}
				}
			}

			// If the "key" is already present, handle it differently
			if lastOccurrence > 0 {
				// Strip parent keys that are already present
				key = key[strings.Index(key, lastMatched)+len(lastMatched):]
				if key[0:2] == ": " {
					key = key[2:]
				}
				// Strip the correct amount of closing tags
				closing = closing[:len(closing)-levelsDeep]

				// Find the position of this key in the master string
				position := strings.Index(changesJson, lastMatched) + len(lastMatched) + 3

				// We're appending to an existing object, so strip the outermost wrapping layer
				key = key[1:]
				closing = closing[:len(closing)-1]

				// Place the value within the existing key
				changesJson = changesJson[:position] + key + value + closing + ", " + changesJson[position:]
			} else {
				// No value found, append it to the end
				changesJson = changesJson + key + value + closing + ", "
			}
		}
	}
	// Trim whitespace and strip trailing comma since we are done inserting at the back
	changesJson = strings.TrimSpace(changesJson)
	if changesJson[len(changesJson)-1:] == "," {
		changesJson = changesJson[:len(changesJson)-1]
	}
	changesJson = changesJson + "}"

	// Now we can go make sure the placeholders are populated with the data in
	for placeholderKey, placeholderValue := range subArrays {
		// Trim the trailing comma since we won't be adding any more stuff
		placeholderValue = strings.TrimSpace(placeholderValue)
		if placeholderValue[len(placeholderValue)-1:] == "," {
			placeholderValue = placeholderValue[:len(placeholderValue)-1]
		}
		changesJson = strings.ReplaceAll(changesJson, placeholderKey, "{"+placeholderValue+"}")
	}

	// Now, hopefully, the json parsing will pass and we have a nicely formatted dataset
	err = json.Unmarshal([]byte(changesJson), &changes)
	if err != nil {
		return nil, err
	}

	return changes, nil
}

var matchFirstCap = regexp.MustCompile("(.)([A-Z][a-z]+)")
var matchAllCap = regexp.MustCompile("([a-z0-9])([A-Z])")

func ToSnakeCase(str string) string {
	snake := matchFirstCap.ReplaceAllString(str, "${1}_${2}")
	snake = matchAllCap.ReplaceAllString(snake, "${1}_${2}")
	return strings.ToLower(snake)
}

func GetIntValue(object interface{}, key string) int64 {
	structValue := reflect.ValueOf(object)
	if structValue.Kind() == reflect.Struct {
		field := structValue.FieldByName(key)
		id := reflection.GetInt64Value(field)
		return id
	}
	return 0
}

func GetStringValue(object interface{}, key string) string {
	structValue := reflect.ValueOf(object)
	if structValue.Kind() == reflect.Struct {
		field := structValue.FieldByName(key)
		id := reflection.GetStringValue(field)
		return id
	}
	return ""
}