package anchor

import (
	"fmt"
	"strconv"

	"github.com/go-logr/logr"
	"github.com/kyverno/kyverno/pkg/logging"
)

// ValidationHandler for element processes
type ValidationHandler interface {
	Handle(handler resourceElementHandler, resourceMap map[string]interface{}, originPattern interface{}, ac *AnchorKey) (string, error)
}

type resourceElementHandler = func(log logr.Logger, resourceElement, patternElement, originPattern interface{}, path string, ac *AnchorKey) (string, error)

// CreateElementHandler factory to process elements
func CreateElementHandler(element string, pattern interface{}, path string) ValidationHandler {
	switch {
	case IsConditionAnchor(element):
		return NewConditionAnchorHandler(element, pattern, path)
	case IsGlobalAnchor(element):
		return NewGlobalAnchorHandler(element, pattern, path)
	case IsExistenceAnchor(element):
		return NewExistenceHandler(element, pattern, path)
	case IsEqualityAnchor(element):
		return NewEqualityHandler(element, pattern, path)
	case IsNegationAnchor(element):
		return NewNegationHandler(element, pattern, path)
	default:
		return NewDefaultHandler(element, pattern, path)
	}
}

// NewNegationHandler returns instance of negation handler
func NewNegationHandler(anchor string, pattern interface{}, path string) ValidationHandler {
	return NegationHandler{
		anchor:  anchor,
		pattern: pattern,
		path:    path,
	}
}

// NegationHandler provides handler for check if the tag in anchor is not defined
type NegationHandler struct {
	anchor  string
	pattern interface{}
	path    string
}

// Handle process negation handler
func (nh NegationHandler) Handle(handler resourceElementHandler, resourceMap map[string]interface{}, originPattern interface{}, ac *AnchorKey) (string, error) {
	anchorKey, _ := RemoveAnchor(nh.anchor)
	currentPath := nh.path + anchorKey + "/"
	// if anchor is present in the resource then fail
	if _, ok := resourceMap[anchorKey]; ok {
		// no need to process elements in value as key cannot be present in resource
		ac.AnchorError = NewNegationAnchorError(fmt.Sprintf("%s is not allowed", currentPath))
		return currentPath, ac.AnchorError.Error()
	}
	// key is not defined in the resource
	return "", nil
}

// NewEqualityHandler returens instance of equality handler
func NewEqualityHandler(anchor string, pattern interface{}, path string) ValidationHandler {
	return EqualityHandler{
		anchor:  anchor,
		pattern: pattern,
		path:    path,
	}
}

// EqualityHandler provides handler for non anchor element
type EqualityHandler struct {
	anchor  string
	pattern interface{}
	path    string
}

// Handle processed condition anchor
func (eh EqualityHandler) Handle(handler resourceElementHandler, resourceMap map[string]interface{}, originPattern interface{}, ac *AnchorKey) (string, error) {
	anchorKey, _ := RemoveAnchor(eh.anchor)
	currentPath := eh.path + anchorKey + "/"
	// check if anchor is present in resource
	if value, ok := resourceMap[anchorKey]; ok {
		// validate the values of the pattern
		returnPath, err := handler(logging.GlobalLogger(), value, eh.pattern, originPattern, currentPath, ac)
		if err != nil {
			return returnPath, err
		}
		return "", nil
	}
	return "", nil
}

// NewDefaultHandler returns handler for non anchor elements
func NewDefaultHandler(element string, pattern interface{}, path string) ValidationHandler {
	return DefaultHandler{
		element: element,
		pattern: pattern,
		path:    path,
	}
}

// DefaultHandler provides handler for non anchor element
type DefaultHandler struct {
	element string
	pattern interface{}
	path    string
}

// Handle process non anchor element
func (dh DefaultHandler) Handle(handler resourceElementHandler, resourceMap map[string]interface{}, originPattern interface{}, ac *AnchorKey) (string, error) {
	currentPath := dh.path + dh.element + "/"
	if dh.pattern == "*" && resourceMap[dh.element] != nil {
		return "", nil
	} else if dh.pattern == "*" && resourceMap[dh.element] == nil {
		return dh.path, fmt.Errorf("%s/%s not found", dh.path, dh.element)
	} else {
		path, err := handler(logging.GlobalLogger(), resourceMap[dh.element], dh.pattern, originPattern, currentPath, ac)
		if err != nil {
			return path, err
		}
	}
	return "", nil
}

// NewConditionAnchorHandler returns an instance of condition acnhor handler
func NewConditionAnchorHandler(anchor string, pattern interface{}, path string) ValidationHandler {
	return ConditionAnchorHandler{
		anchor:  anchor,
		pattern: pattern,
		path:    path,
	}
}

// ConditionAnchorHandler provides handler for condition anchor
type ConditionAnchorHandler struct {
	anchor  string
	pattern interface{}
	path    string
}

// Handle processed condition anchor
func (ch ConditionAnchorHandler) Handle(handler resourceElementHandler, resourceMap map[string]interface{}, originPattern interface{}, ac *AnchorKey) (string, error) {
	anchorKey, _ := RemoveAnchor(ch.anchor)
	currentPath := ch.path + anchorKey + "/"
	// check if anchor is present in resource
	if value, ok := resourceMap[anchorKey]; ok {
		// validate the values of the pattern
		returnPath, err := handler(logging.GlobalLogger(), value, ch.pattern, originPattern, currentPath, ac)
		if err != nil {
			ac.AnchorError = NewConditionalAnchorError(err.Error())
			return returnPath, ac.AnchorError.Error()
		}
		return "", nil
	} else {
		msg := "conditional anchor key doesn't exist in the resource"
		return currentPath, NewConditionalAnchorError(msg).Error()
	}
}

// NewGlobalAnchorHandler returns an instance of condition acnhor handler
func NewGlobalAnchorHandler(anchor string, pattern interface{}, path string) ValidationHandler {
	return GlobalAnchorHandler{
		anchor:  anchor,
		pattern: pattern,
		path:    path,
	}
}

// GlobalAnchorHandler provides handler for global condition anchor
type GlobalAnchorHandler struct {
	anchor  string
	pattern interface{}
	path    string
}

// Handle processed global condition anchor
func (gh GlobalAnchorHandler) Handle(handler resourceElementHandler, resourceMap map[string]interface{}, originPattern interface{}, ac *AnchorKey) (string, error) {
	anchorKey, _ := RemoveAnchor(gh.anchor)
	currentPath := gh.path + anchorKey + "/"
	// check if anchor is present in resource
	if value, ok := resourceMap[anchorKey]; ok {
		// validate the values of the pattern
		returnPath, err := handler(logging.GlobalLogger(), value, gh.pattern, originPattern, currentPath, ac)
		if err != nil {
			ac.AnchorError = NewGlobalAnchorError(err.Error())
			return returnPath, ac.AnchorError.Error()
		}
		return "", nil
	}
	return "", nil
}

// NewExistenceHandler returns existence handler
func NewExistenceHandler(anchor string, pattern interface{}, path string) ValidationHandler {
	return ExistenceHandler{
		anchor:  anchor,
		pattern: pattern,
		path:    path,
	}
}

// ExistenceHandler provides handlers to process exitence anchor handler
type ExistenceHandler struct {
	anchor  string
	pattern interface{}
	path    string
}

// Handle processes the existence anchor handler
func (eh ExistenceHandler) Handle(handler resourceElementHandler, resourceMap map[string]interface{}, originPattern interface{}, ac *AnchorKey) (string, error) {
	// skip is used by existence anchor to not process further if condition is not satisfied
	anchorKey, _ := RemoveAnchor(eh.anchor)
	currentPath := eh.path + anchorKey + "/"
	// check if anchor is present in resource
	if value, ok := resourceMap[anchorKey]; ok {
		// Existence anchor can only exist on resource value type of list
		switch typedResource := value.(type) {
		case []interface{}:
			typedPattern, ok := eh.pattern.([]interface{})
			if !ok {
				return currentPath, fmt.Errorf("invalid pattern type %T: Pattern has to be of list to compare against resource", eh.pattern)
			}
			// loop all item in the pattern array
			errorPath := ""
			var err error
			for _, patternMap := range typedPattern {
				typedPatternMap, ok := patternMap.(map[string]interface{})
				if !ok {
					return currentPath, fmt.Errorf("invalid pattern type %T: Pattern has to be of type map to compare against items in resource", eh.pattern)
				}
				errorPath, err = validateExistenceListResource(handler, typedResource, typedPatternMap, originPattern, currentPath, ac)
				if err != nil {
					return errorPath, err
				}
			}
			return errorPath, err
		default:
			return currentPath, fmt.Errorf("invalid resource type %T: Existence ^ () anchor can be used only on list/array type resource", value)
		}
	}
	return "", nil
}

func validateExistenceListResource(handler resourceElementHandler, resourceList []interface{}, patternMap map[string]interface{}, originPattern interface{}, path string, ac *AnchorKey) (string, error) {
	// the idea is all the element in the pattern array should be present atleast once in the resource list
	// if non satisfy then throw an error
	for i, resourceElement := range resourceList {
		currentPath := path + strconv.Itoa(i) + "/"
		_, err := handler(logging.GlobalLogger(), resourceElement, patternMap, originPattern, currentPath, ac)
		if err == nil {
			// condition is satisfied, dont check further
			return "", nil
		}
	}
	// none of the existence checks worked, so thats a failure sceanario
	return path, fmt.Errorf("existence anchor validation failed at path %s", path)
}

// GetAnchorsResourcesFromMap returns map of anchors
func GetAnchorsResourcesFromMap(patternMap map[string]interface{}) (map[string]interface{}, map[string]interface{}) {
	anchors := map[string]interface{}{}
	resources := map[string]interface{}{}
	for key, value := range patternMap {
		if IsConditionAnchor(key) || IsExistenceAnchor(key) || IsEqualityAnchor(key) || IsNegationAnchor(key) {
			anchors[key] = value
			continue
		}
		resources[key] = value
	}

	return anchors, resources
}