/*
Copyright 2021 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package nodefeaturerule

import (
	"bytes"
	"fmt"
	"maps"
	"slices"
	"strings"
	"text/template"

	corev1 "k8s.io/api/core/v1"
	"k8s.io/klog/v2"

	nfdv1alpha1 "sigs.k8s.io/node-feature-discovery/api/nfd/v1alpha1"
	"sigs.k8s.io/node-feature-discovery/pkg/utils"
)

// RuleOutput contains the output out rule execution.
// +k8s:deepcopy-gen=false
type RuleOutput struct {
	ExtendedResources map[string]string
	Labels            map[string]string
	Annotations       map[string]string
	Vars              map[string]string
	Taints            []corev1.Taint
}

// Execute the rule against a set of input features.
func Execute(r *nfdv1alpha1.Rule, features *nfdv1alpha1.Features) (RuleOutput, error) {
	labels := make(map[string]string)
	vars := make(map[string]string)

	if len(r.MatchAny) > 0 {
		// Logical OR over the matchAny matchers
		matched := false
		for _, matcher := range r.MatchAny {
			if isMatch, matches, err := evaluateMatchAnyElem(&matcher, features); err != nil {
				return RuleOutput{}, err
			} else if isMatch {
				matched = true
				klog.V(4).InfoS("matchAny matched", "ruleName", r.Name, "matchedFeatures", utils.DelayedDumper(matches))

				if r.LabelsTemplate == "" && r.VarsTemplate == "" {
					// there's no need to evaluate other matchers in MatchAny
					// if there are no templates to be executed on them - so
					// short-circuit and stop on first match here
					break
				}

				if err := executeLabelsTemplate(r, matches, labels); err != nil {
					return RuleOutput{}, err
				}
				if err := executeVarsTemplate(r, matches, vars); err != nil {
					return RuleOutput{}, err
				}
			}
		}
		if !matched {
			klog.V(2).InfoS("rule did not match", "ruleName", r.Name)
			return RuleOutput{}, nil
		}
	}

	if len(r.MatchFeatures) > 0 {
		if isMatch, matches, err := evaluateFeatureMatcher(&r.MatchFeatures, features); err != nil {
			return RuleOutput{}, err
		} else if !isMatch {
			klog.V(2).InfoS("rule did not match", "ruleName", r.Name)
			return RuleOutput{}, nil
		} else {
			klog.V(4).InfoS("matchFeatures matched", "ruleName", r.Name, "matchedFeatures", utils.DelayedDumper(matches))
			if err := executeLabelsTemplate(r, matches, labels); err != nil {
				return RuleOutput{}, err
			}
			if err := executeVarsTemplate(r, matches, vars); err != nil {
				return RuleOutput{}, err
			}
		}
	}

	maps.Copy(labels, r.Labels)
	maps.Copy(vars, r.Vars)

	ret := RuleOutput{
		Labels:            labels,
		Vars:              vars,
		Annotations:       maps.Clone(r.Annotations),
		ExtendedResources: maps.Clone(r.ExtendedResources),
		Taints:            slices.Clone(r.Taints),
	}
	klog.V(2).InfoS("rule matched", "ruleName", r.Name, "ruleOutput", utils.DelayedDumper(ret))
	return ret, nil
}

func executeLabelsTemplate(r *nfdv1alpha1.Rule, in matchedFeatures, out map[string]string) error {
	if r.LabelsTemplate == "" {
		return nil
	}

	th, err := newTemplateHelper(r.LabelsTemplate)
	if err != nil {
		return fmt.Errorf("failed to parse LabelsTemplate: %w", err)
	}

	labels, err := th.expandMap(in)
	if err != nil {
		return fmt.Errorf("failed to expand LabelsTemplate: %w", err)
	}
	for k, v := range labels {
		out[k] = v
	}
	return nil
}

func executeVarsTemplate(r *nfdv1alpha1.Rule, in matchedFeatures, out map[string]string) error {
	if r.VarsTemplate == "" {
		return nil
	}

	th, err := newTemplateHelper(r.VarsTemplate)
	if err != nil {
		return err
	}

	vars, err := th.expandMap(in)
	if err != nil {
		return err
	}
	for k, v := range vars {
		out[k] = v
	}
	return nil
}

type matchedFeatures map[string]domainMatchedFeatures

type domainMatchedFeatures map[string][]MatchedElement

func evaluateMatchAnyElem(e *nfdv1alpha1.MatchAnyElem, features *nfdv1alpha1.Features) (bool, matchedFeatures, error) {
	return evaluateFeatureMatcher(&e.MatchFeatures, features)
}

func evaluateFeatureMatcher(m *nfdv1alpha1.FeatureMatcher, features *nfdv1alpha1.Features) (bool, matchedFeatures, error) {
	matches := make(matchedFeatures, len(*m))

	// Logical AND over the terms
	for _, term := range *m {
		// Ignore case
		featureName := strings.ToLower(term.Feature)

		nameSplit := strings.SplitN(term.Feature, ".", 2)
		if len(nameSplit) != 2 {
			klog.InfoS("invalid feature name (not <domain>.<feature>), cannot be used for templating", "featureName", term.Feature)
			nameSplit = []string{featureName, ""}
		}

		dom := nameSplit[0]
		nam := nameSplit[1]
		if _, ok := matches[dom]; !ok {
			matches[dom] = make(domainMatchedFeatures)
		}

		var isMatch = true
		var matchedElems []MatchedElement
		var err error
		if f, ok := features.Flags[featureName]; ok {
			if term.MatchExpressions != nil {
				isMatch, matchedElems, err = MatchGetKeys(term.MatchExpressions, f.Elements)
			}
			var meTmp []MatchedElement
			if err == nil && isMatch && term.MatchName != nil {
				isMatch, meTmp, err = MatchKeyNames(term.MatchName, f.Elements)
				matchedElems = append(matchedElems, meTmp...)
			}
		} else if f, ok := features.Attributes[featureName]; ok {
			if term.MatchExpressions != nil {
				isMatch, matchedElems, err = MatchGetValues(term.MatchExpressions, f.Elements)
			}
			var meTmp []MatchedElement
			if err == nil && isMatch && term.MatchName != nil {
				isMatch, meTmp, err = MatchValueNames(term.MatchName, f.Elements)
				matchedElems = append(matchedElems, meTmp...)
			}
		} else if f, ok := features.Instances[featureName]; ok {
			if term.MatchExpressions != nil {
				matchedElems, err = MatchGetInstances(term.MatchExpressions, f.Elements)
				isMatch = len(matchedElems) > 0
			}
			var meTmp []MatchedElement
			if err == nil && isMatch && term.MatchName != nil {
				meTmp, err = MatchInstanceAttributeNames(term.MatchName, f.Elements)
				isMatch = len(meTmp) > 0
				matchedElems = append(matchedElems, meTmp...)

			}
		} else {
			return false, nil, fmt.Errorf("feature %q not available", featureName)
		}
		matches[dom][nam] = append(matches[dom][nam], matchedElems...)

		if err != nil {
			return false, nil, err
		} else if !isMatch {
			return false, nil, nil
		}
	}
	return true, matches, nil
}

type templateHelper struct {
	template *template.Template
}

func newTemplateHelper(name string) (*templateHelper, error) {
	tmpl, err := template.New("").Option("missingkey=error").Parse(name)
	if err != nil {
		return nil, fmt.Errorf("invalid template: %w", err)
	}
	return &templateHelper{template: tmpl}, nil
}

func (h *templateHelper) execute(data interface{}) (string, error) {
	var tmp bytes.Buffer
	if err := h.template.Execute(&tmp, data); err != nil {
		return "", err
	}
	return tmp.String(), nil
}

// expandMap is a helper for expanding a template in to a map of strings. Data
// after executing the template is expexted to be key=value pairs separated by
// newlines.
func (h *templateHelper) expandMap(data interface{}) (map[string]string, error) {
	expanded, err := h.execute(data)
	if err != nil {
		return nil, err
	}

	// Split out individual key-value pairs
	out := make(map[string]string)
	for _, item := range strings.Split(expanded, "\n") {
		// Remove leading/trailing whitespace and skip empty lines
		if trimmed := strings.TrimSpace(item); trimmed != "" {
			split := strings.SplitN(trimmed, "=", 2)
			if len(split) == 1 {
				return nil, fmt.Errorf("missing value in expanded template line %q, (format must be '<key>=<value>')", trimmed)
			}
			out[split[0]] = split[1]
		}
	}
	return out, nil
}