/*
   Copyright Docker attest 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 mapping

import (
	"fmt"

	v1 "github.com/google/go-containerregistry/pkg/v1"
)

type matchType string

const (
	MatchTypePolicy        matchType = "policy"
	MatchTypeMatchNoPolicy matchType = "match_no_policy"
	MatchTypeNoMatch       matchType = "no_match"
)

type PolicyMatch struct {
	MatchType   matchType
	Policy      *PolicyMapping
	Rule        *PolicyRule
	MatchedName string
}

func (mappings *PolicyMappings) FindPolicyMatch(imageName string, platform *v1.Platform) (*PolicyMatch, error) {
	if mappings == nil {
		return &PolicyMatch{MatchType: MatchTypeNoMatch, MatchedName: imageName}, nil
	}
	return mappings.findPolicyMatchImpl(imageName, platform, make(map[*PolicyRule]bool))
}

func (mappings *PolicyMappings) findPolicyMatchImpl(imageName string, platform *v1.Platform, matched map[*PolicyRule]bool) (*PolicyMatch, error) {
	for _, rule := range mappings.Rules {
		if !rule.matchesPlatform(platform) {
			continue
		}
		if rule.Pattern.MatchString(imageName) {
			switch {
			case rule.PolicyID == "" && rule.Replacement == "":
				return nil, fmt.Errorf("rule %s has neither policy-id nor rewrite", rule.Pattern)
			case rule.PolicyID != "" && rule.Replacement != "":
				return nil, fmt.Errorf("rule %s has both policy-id and rewrite", rule.Pattern)
			case rule.PolicyID != "":
				policy := mappings.Policies[rule.PolicyID]
				if policy != nil {
					return &PolicyMatch{
						MatchType:   MatchTypePolicy,
						Policy:      policy,
						Rule:        rule,
						MatchedName: imageName,
					}, nil
				}
				return &PolicyMatch{
					MatchType:   MatchTypeMatchNoPolicy,
					Rule:        rule,
					MatchedName: imageName,
				}, nil
			case rule.Replacement != "":
				if matched[rule] {
					return nil, fmt.Errorf("rewrite loop detected")
				}
				matched[rule] = true
				imageName = rule.Pattern.ReplaceAllString(imageName, rule.Replacement)
				return mappings.findPolicyMatchImpl(imageName, platform, matched)
			}
		}
	}
	return &PolicyMatch{MatchType: MatchTypeNoMatch}, nil
}

func (rule *PolicyRule) matchesPlatform(platform *v1.Platform) bool {
	if len(rule.Platforms) == 0 {
		return true
	}
	for i := range rule.Platforms {
		if rule.Platforms[i].Equals(*platform) {
			return true
		}
	}
	return false
}