// Copyright 2019 The Kubernetes Authors.
// SPDX-License-Identifier: Apache-2.0

package v1alpha1

import (
	"fmt"
	"io"
	"io/ioutil"
	"regexp"
	"strconv"
	"strings"

	"k8s.io/apimachinery/pkg/runtime/schema"
	"sigs.k8s.io/kustomize/api/k8sdeps/kunstruct"
	"sigs.k8s.io/kustomize/api/resmap"
	"sigs.k8s.io/kustomize/api/resource"
	"sigs.k8s.io/kustomize/api/types"
	"sigs.k8s.io/yaml"

	plugtypes "opendev.org/airship/airshipctl/pkg/document/plugin/types"
	"opendev.org/airship/airshipctl/pkg/environment"
)

var (
	pattern = regexp.MustCompile(`(\S+)\[(\S+)=(\S+)\]`)
	// substring substitutions are appended to paths as: ...%VARNAME%
	substringPatternRegex = regexp.MustCompile(`(\S+)%(\S+)%$`)
)

const (
	dotReplacer = "$$$$"
)

// GetGVK returns group, version, kind object used to register version
// of the plugin
func GetGVK() schema.GroupVersionKind {
	return schema.GroupVersionKind{
		Group:   "airshipit.org",
		Version: "v1alpha1",
		Kind:    "ReplacementTransformer",
	}
}

// New creates new instance of the plugin
func New(_ *environment.AirshipCTLSettings, cfg []byte) (plugtypes.Plugin, error) {
	p := &plugin{}
	if err := p.Config(nil, cfg); err != nil {
		return nil, err
	}
	return p, nil
}

func (p *plugin) Run(in io.Reader, out io.Writer) error {
	data, err := ioutil.ReadAll(in)
	if err != nil {
		return err
	}

	kf := kunstruct.NewKunstructuredFactoryImpl()
	rf := resource.NewFactory(kf)
	resources, err := rf.SliceFromBytes(data)
	if err != nil {
		return err
	}

	rm := resmap.New()
	for _, r := range resources {
		if err = rm.Append(r); err != nil {
			return err
		}
	}

	if err = p.Transform(rm); err != nil {
		return err
	}

	result, err := rm.AsYaml()
	if err != nil {
		return err
	}
	fmt.Fprint(out, string(result))
	return nil
}

// Config function reads replacements configuration
func (p *plugin) Config(
	_ *resmap.PluginHelpers, c []byte) error {
	p.Replacements = []types.Replacement{}
	err := yaml.Unmarshal(c, p)
	if err != nil {
		return err
	}
	for _, r := range p.Replacements {
		if r.Source == nil {
			return ErrBadConfiguration{Msg: "`from` must be specified in one replacement"}
		}
		if r.Target == nil {
			return ErrBadConfiguration{Msg: "`to` must be specified in one replacement"}
		}
		if r.Source.ObjRef != nil && r.Source.Value != "" {
			return ErrBadConfiguration{Msg: "only one of fieldref and value is allowed in one replacement"}
		}
	}
	return nil
}

// Transform resources using configured replacements
func (p *plugin) Transform(m resmap.ResMap) error {
	var err error
	for _, r := range p.Replacements {
		var replacement interface{}
		if r.Source.ObjRef != nil {
			replacement, err = getReplacement(m, r.Source.ObjRef, r.Source.FieldRef)
			if err != nil {
				return err
			}
		}
		if r.Source.Value != "" {
			replacement = r.Source.Value
		}
		if err = substitute(m, r.Target, replacement); err != nil {
			return err
		}
	}
	return nil
}

func getReplacement(m resmap.ResMap, objRef *types.Target, fieldRef string) (interface{}, error) {
	s := types.Selector{
		Gvk:       objRef.Gvk,
		Name:      objRef.Name,
		Namespace: objRef.Namespace,
	}
	resources, err := m.Select(s)
	if err != nil {
		return nil, err
	}
	if len(resources) > 1 {
		return nil, ErrMultipleResources{ResList: resources}
	}
	if len(resources) == 0 {
		return nil, ErrResourceNotFound{ObjRef: objRef}
	}
	if fieldRef == "" {
		fieldRef = "metadata.name"
	}
	return resources[0].GetFieldValue(fieldRef)
}

func substitute(m resmap.ResMap, to *types.ReplTarget, replacement interface{}) error {
	resources, err := m.Select(*to.ObjRef)
	if err != nil {
		return err
	}
	for _, r := range resources {
		for _, p := range to.FieldRefs {
			// TODO (dukov) rework this using k8s.io/client-go/util/jsonpath
			parts := strings.Split(p, "[")
			var tmp []string
			for _, part := range parts {
				if strings.Contains(part, "]") {
					filter := strings.Split(part, "]")
					filter[0] = strings.ReplaceAll(filter[0], ".", dotReplacer)
					part = strings.Join(filter, "]")
				}
				tmp = append(tmp, part)
			}
			p = strings.Join(tmp, "[")

			pathSlice := strings.Split(p, ".")
			for i, part := range pathSlice {
				pathSlice[i] = strings.ReplaceAll(part, dotReplacer, ".")
			}
			if err := updateField(r.Map(), pathSlice, replacement); err != nil {
				return err
			}
		}
	}
	return nil
}

func getFirstPathSegment(path string) (field string, key string, value string, isArray bool) {
	groups := pattern.FindStringSubmatch(path)
	if len(groups) != 4 {
		return path, "", "", false
	}
	return groups[1], groups[2], groups[3], groups[2] != ""
}

func updateField(m interface{}, pathToField []string, replacement interface{}) error {
	if len(pathToField) == 0 {
		return nil
	}

	switch typedM := m.(type) {
	case map[string]interface{}:
		return updateMapField(typedM, pathToField, replacement)
	case []interface{}:
		return updateSliceField(typedM, pathToField, replacement)
	default:
		return ErrTypeMismatch{Actual: typedM, Expectation: "is not expected be a primitive type"}
	}
}

// Extract the substring pattern (if present) from the target path spec
func extractSubstringPattern(path string) (extractedPath string, substringPattern string) {
	groups := substringPatternRegex.FindStringSubmatch(path)
	if len(groups) != 3 {
		return path, ""
	}
	return groups[1], groups[2]
}

// apply a substring substitution based on a pattern
func applySubstringPattern(target interface{}, replacement interface{},
	substringPattern string) (regexedReplacement interface{}, err error) {
	// no regex'ing needed if there is no substringPattern
	if substringPattern == "" {
		return replacement, nil
	}

	repl, ok := replacement.(string)
	if !ok {
		return nil, ErrPatternSubstring{Msg: "pattern-based substitution can only be applied with string replacement values"}
	}

	tgt, ok := target.(string)
	if !ok {
		return nil, ErrPatternSubstring{Msg: "pattern-based substitution can only be applied to string target fields"}
	}

	p := regexp.MustCompile(substringPattern)
	if !p.MatchString(tgt) {
		return nil, ErrPatternSubstring{
			Msg: fmt.Sprintf("pattern '%s' is defined in configuration but was not found in target value %s",
				substringPattern, tgt),
		}
	}
	return p.ReplaceAllString(tgt, repl), nil
}

func updateMapField(m map[string]interface{}, pathToField []string, replacement interface{}) error {
	path, key, value, isArray := getFirstPathSegment(pathToField[0])

	path, substringPattern := extractSubstringPattern(path)

	v, found := m[path]
	if !found {
		m[path] = make(map[string]interface{})
		v = m[path]
	}

	if v == nil {
		return ErrTypeMismatch{Actual: v, Expectation: "is not expected be nil"}
	}

	if len(pathToField) == 1 {
		if !isArray {
			renderedRepl, err := applySubstringPattern(m[path], replacement, substringPattern)
			if err != nil {
				return err
			}
			m[path] = renderedRepl
			return nil
		}
		switch typedV := v.(type) {
		case []interface{}:
			for i, item := range typedV {
				typedItem, ok := item.(map[string]interface{})
				if !ok {
					return ErrTypeMismatch{Actual: item, Expectation: fmt.Sprintf("is expected to be %T", typedItem)}
				}
				if actualValue, ok := typedItem[key]; ok {
					if value == actualValue {
						typedV[i] = replacement
						return nil
					}
				}
			}
		default:
			return ErrTypeMismatch{Actual: typedV, Expectation: "is not expected be a primitive type"}
		}
	}

	if isArray {
		return updateField(v, pathToField, replacement)
	}
	return updateField(v, pathToField[1:], replacement)
}

func updateSliceField(m []interface{}, pathToField []string, replacement interface{}) error {
	if len(pathToField) == 0 {
		return nil
	}
	path, key, value, isArray := getFirstPathSegment(pathToField[0])

	if isArray {
		for _, item := range m {
			typedItem, ok := item.(map[string]interface{})
			if !ok {
				return ErrTypeMismatch{Actual: item, Expectation: fmt.Sprintf("is expected to be %T", typedItem)}
			}
			if actualValue, ok := typedItem[key]; ok {
				if value == actualValue {
					return updateField(typedItem, pathToField[1:], replacement)
				}
			}
		}
		return ErrMapNotFound{Key: key, Value: value, ListKey: path}
	}

	index, err := strconv.Atoi(pathToField[0])
	if err != nil {
		return err
	}

	if len(m) < index || index < 0 {
		return ErrIndexOutOfBound{Index: index}
	}
	if len(pathToField) == 1 {
		m[index] = replacement
		return nil
	}
	return updateField(m[index], pathToField[1:], replacement)
}