package trust

import (
	"fmt"
	"sort"
	"strings"

	"golang.org/x/exp/maps"
)

// Policy describes a basic trust policy configuration
type Policy struct {
	Transport      string   `json:"transport"`
	Name           string   `json:"name,omitempty"`
	RepoName       string   `json:"repo_name,omitempty"`
	Keys           []string `json:"keys,omitempty"`
	SignatureStore string   `json:"sigstore,omitempty"`
	Type           string   `json:"type"`
	GPGId          string   `json:"gpg_id,omitempty"`
}

// PolicyDescription returns an user-focused description of the policy in policyPath and registries.d data from registriesDirPath.
func PolicyDescription(policyPath, registriesDirPath string) ([]*Policy, error) {
	return policyDescriptionWithGPGIDReader(policyPath, registriesDirPath, getGPGIdFromKeyPath)
}

// policyDescriptionWithGPGIDReader is PolicyDescription with a gpgIDReader parameter. It exists only to make testing easier.
func policyDescriptionWithGPGIDReader(policyPath, registriesDirPath string, idReader gpgIDReader) ([]*Policy, error) {
	policyContentStruct, err := getPolicy(policyPath)
	if err != nil {
		return nil, fmt.Errorf("could not read trust policies: %w", err)
	}
	res, err := getPolicyShowOutput(policyContentStruct, registriesDirPath, idReader)
	if err != nil {
		return nil, fmt.Errorf("could not show trust policies: %w", err)
	}
	return res, nil
}

func getPolicyShowOutput(policyContentStruct policyContent, systemRegistriesDirPath string, idReader gpgIDReader) ([]*Policy, error) {
	var output []*Policy

	registryConfigs, err := loadAndMergeConfig(systemRegistriesDirPath)
	if err != nil {
		return nil, err
	}

	if len(policyContentStruct.Default) > 0 {
		template := Policy{
			Transport: "all",
			Name:      "* (default)",
			RepoName:  "default",
		}
		output = append(output, descriptionsOfPolicyRequirements(policyContentStruct.Default, template, registryConfigs, "", idReader)...)
	}
	transports := maps.Keys(policyContentStruct.Transports)
	sort.Strings(transports)
	for _, transport := range transports {
		transval := policyContentStruct.Transports[transport]
		if transport == "docker" {
			transport = "repository"
		}

		scopes := maps.Keys(transval)
		sort.Strings(scopes)
		for _, repo := range scopes {
			repoval := transval[repo]
			template := Policy{
				Transport: transport,
				Name:      repo,
				RepoName:  repo,
			}
			output = append(output, descriptionsOfPolicyRequirements(repoval, template, registryConfigs, repo, idReader)...)
		}
	}
	return output, nil
}

// descriptionsOfPolicyRequirements turns reqs into user-readable policy entries, with Transport/Name/Reponame coming from template, potentially looking up scope (which may be "") in registryConfigs.
func descriptionsOfPolicyRequirements(reqs []repoContent, template Policy, registryConfigs *registryConfiguration, scope string, idReader gpgIDReader) []*Policy {
	res := []*Policy{}

	var lookasidePath string
	registryNamespace := registriesDConfigurationForScope(registryConfigs, scope)
	if registryNamespace != nil {
		if registryNamespace.Lookaside != "" {
			lookasidePath = registryNamespace.Lookaside
		} else { // incl. registryNamespace.SigStore == ""
			lookasidePath = registryNamespace.SigStore
		}
	}

	for _, repoele := range reqs {
		entry := template
		entry.Type = trustTypeDescription(repoele.Type)

		var gpgIDString string
		switch repoele.Type {
		case "signedBy":
			uids := []string{}
			if len(repoele.KeyPath) > 0 {
				uids = append(uids, idReader(repoele.KeyPath)...)
			}
			for _, path := range repoele.KeyPaths {
				uids = append(uids, idReader(path)...)
			}
			if len(repoele.KeyData) > 0 {
				uids = append(uids, getGPGIdFromKeyData(idReader, repoele.KeyData)...)
			}
			gpgIDString = strings.Join(uids, ", ")

		case "sigstoreSigned":
			gpgIDString = "N/A" // We could potentially return key fingerprints here, but they would not be _GPG_ fingerprints.
		}
		entry.GPGId = gpgIDString
		entry.SignatureStore = lookasidePath // We do this even for sigstoreSigned and things like type: reject, to show that the sigstore is being read.
		res = append(res, &entry)
	}

	return res
}
