// Copyright 2024 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package repository

import (
	"context"
	"fmt"
	"io"

	"code.gitea.io/gitea/models/db"
	repo_model "code.gitea.io/gitea/models/repo"
	"code.gitea.io/gitea/modules/container"
	"code.gitea.io/gitea/modules/git"
	"code.gitea.io/gitea/modules/gitrepo"
	"code.gitea.io/gitea/modules/graceful"
	"code.gitea.io/gitea/modules/json"
	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/options"
	"code.gitea.io/gitea/modules/queue"

	licenseclassifier "github.com/google/licenseclassifier/v2"
)

var (
	classifier      *licenseclassifier.Classifier
	LicenseFileName = "LICENSE"
	licenseAliases  map[string]string

	// licenseUpdaterQueue represents a queue to handle update repo licenses
	licenseUpdaterQueue *queue.WorkerPoolQueue[*LicenseUpdaterOptions]
)

func AddRepoToLicenseUpdaterQueue(opts *LicenseUpdaterOptions) error {
	if opts == nil {
		return nil
	}
	return licenseUpdaterQueue.Push(opts)
}

func loadLicenseAliases() error {
	if licenseAliases != nil {
		return nil
	}

	data, err := options.AssetFS().ReadFile("license", "etc", "license-aliases.json")
	if err != nil {
		return err
	}
	err = json.Unmarshal(data, &licenseAliases)
	if err != nil {
		return err
	}
	return nil
}

func ConvertLicenseName(name string) string {
	if err := loadLicenseAliases(); err != nil {
		return name
	}

	v, ok := licenseAliases[name]
	if ok {
		return v
	}
	return name
}

func InitLicenseClassifier() error {
	// threshold should be 0.84~0.86 or the test will be failed
	classifier = licenseclassifier.NewClassifier(.85)
	licenseFiles, err := options.AssetFS().ListFiles("license", true)
	if err != nil {
		return err
	}

	existLicense := make(container.Set[string])
	if len(licenseFiles) > 0 {
		for _, licenseFile := range licenseFiles {
			licenseName := ConvertLicenseName(licenseFile)
			if existLicense.Contains(licenseName) {
				continue
			}
			existLicense.Add(licenseName)
			data, err := options.License(licenseFile)
			if err != nil {
				return err
			}
			classifier.AddContent("License", licenseFile, licenseName, data)
		}
	}
	return nil
}

type LicenseUpdaterOptions struct {
	RepoID int64
}

func repoLicenseUpdater(items ...*LicenseUpdaterOptions) []*LicenseUpdaterOptions {
	ctx := graceful.GetManager().ShutdownContext()

	for _, opts := range items {
		repo, err := repo_model.GetRepositoryByID(ctx, opts.RepoID)
		if err != nil {
			log.Error("repoLicenseUpdater [%d] failed: GetRepositoryByID: %v", opts.RepoID, err)
			continue
		}
		if repo.IsEmpty {
			continue
		}

		gitRepo, err := gitrepo.OpenRepository(ctx, repo)
		if err != nil {
			log.Error("repoLicenseUpdater [%d] failed: OpenRepository: %v", opts.RepoID, err)
			continue
		}
		defer gitRepo.Close()

		commit, err := gitRepo.GetBranchCommit(repo.DefaultBranch)
		if err != nil {
			log.Error("repoLicenseUpdater [%d] failed: GetBranchCommit: %v", opts.RepoID, err)
			continue
		}
		if err = UpdateRepoLicenses(ctx, repo, commit); err != nil {
			log.Error("repoLicenseUpdater [%d] failed: updateRepoLicenses: %v", opts.RepoID, err)
		}
	}
	return nil
}

func SyncRepoLicenses(ctx context.Context) error {
	log.Trace("Doing: SyncRepoLicenses")

	if err := db.Iterate(
		ctx,
		nil,
		func(ctx context.Context, repo *repo_model.Repository) error {
			select {
			case <-ctx.Done():
				return db.ErrCancelledf("before sync repo licenses for %s", repo.FullName())
			default:
			}
			return AddRepoToLicenseUpdaterQueue(&LicenseUpdaterOptions{RepoID: repo.ID})
		},
	); err != nil {
		log.Trace("Error: SyncRepoLicenses: %v", err)
		return err
	}

	log.Trace("Finished: SyncReposLicenses")
	return nil
}

// UpdateRepoLicenses will update repository licenses col if license file exists
func UpdateRepoLicenses(ctx context.Context, repo *repo_model.Repository, commit *git.Commit) error {
	if commit == nil {
		return nil
	}

	b, err := commit.GetBlobByPath(LicenseFileName)
	if err != nil && !git.IsErrNotExist(err) {
		return fmt.Errorf("GetBlobByPath: %w", err)
	}

	if git.IsErrNotExist(err) {
		return repo_model.CleanRepoLicenses(ctx, repo)
	}

	licenses := make([]string, 0)
	if b != nil {
		r, err := b.DataAsync()
		if err != nil {
			return err
		}
		defer r.Close()

		licenses, err = detectLicense(r)
		if err != nil {
			return fmt.Errorf("detectLicense: %w", err)
		}
	}
	return repo_model.UpdateRepoLicenses(ctx, repo, commit.ID.String(), licenses)
}

// detectLicense returns the licenses detected by the given content buff
func detectLicense(r io.Reader) ([]string, error) {
	if r == nil {
		return nil, nil
	}

	matches, err := classifier.MatchFrom(r)
	if err != nil {
		return nil, err
	}
	if len(matches.Matches) > 0 {
		results := make(container.Set[string], len(matches.Matches))
		for _, r := range matches.Matches {
			if r.MatchType == "License" && !results.Contains(r.Variant) {
				results.Add(r.Variant)
			}
		}
		return results.Values(), nil
	}
	return nil, nil
}