// Copyright 2016 Google Inc. All rights reserved.
//
// 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.

/* zoekt-repo-index indexes a repo-based repository.  The constituent
git repositories should already have been downloaded to the
--repo_cache directory, eg.

    go install github.com/google/zoekt/cmd/zoekt-repo-index &&

    zoekt-repo-index -base_url https://gfiber.googlesource.com/ \
      -manifest_repo_url https://gfiber.googlesource.com/manifests \
      -manifest_rev_prefix=refs/heads/ \
      -rev_prefix="refs/remotes/" \
      -repo_cache ~/zoekt-serving/repos/ \
      -shard_limit 50000000 \
       master:default_unrestricted.xml
*/
package main

import (
	"crypto/sha1"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"net/url"
	"path"
	"path/filepath"
	"sort"
	"strings"

	"github.com/google/slothfs/manifest"
	"github.com/google/zoekt"
	"github.com/google/zoekt/build"
	"github.com/google/zoekt/gitindex"
	"go.uber.org/automaxprocs/maxprocs"

	git "github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing"
)

var _ = log.Println

type fileKey struct {
	SubRepoPath string
	Path        string
	ID          plumbing.Hash
}

func (k *fileKey) FullPath() string {
	return filepath.Join(k.SubRepoPath, k.Path)
}

type branchFile struct {
	branch, file string
	mf           *manifest.Manifest
	manifestPath string
}

func parseBranches(manifestRepoURL, revPrefix string, cache *gitindex.RepoCache, args []string) ([]branchFile, error) {
	var branches []branchFile
	if manifestRepoURL != "" {
		u, err := url.Parse(manifestRepoURL)
		if err != nil {
			return nil, err
		}

		repo, err := cache.Open(u)
		if err != nil {
			return nil, err
		}

		for _, f := range args {
			fs := strings.SplitN(f, ":", 2)
			if len(fs) != 2 {
				return nil, fmt.Errorf("cannot parse %q as BRANCH:FILE", f)
			}
			mf, err := getManifest(repo, revPrefix+fs[0], fs[1])
			if err != nil {
				return nil, fmt.Errorf("manifest %s:%s: %v", fs[0], fs[1], err)
			}

			branches = append(branches, branchFile{
				branch:       fs[0],
				file:         fs[1],
				mf:           mf,
				manifestPath: cache.Path(u),
			})
		}
	} else {
		if len(args) == 0 {
			return nil, fmt.Errorf("must give XML file argument")
		}
		for _, f := range args {
			mf, err := manifest.ParseFile(f)
			if err != nil {
				return nil, err
			}

			branches = append(branches, branchFile{
				branch:       "HEAD",
				file:         filepath.Base(f),
				mf:           mf,
				manifestPath: f,
			})
		}
	}
	return branches, nil
}

func main() {
	sizeMax := flag.Int("file_limit", 128<<10, "maximum file size")
	shardLimit := flag.Int("shard_limit", 100<<20, "maximum corpus size for a shard")
	parallelism := flag.Int("parallelism", 1, "maximum number of parallel indexing processes")

	revPrefix := flag.String("rev_prefix", "refs/remotes/origin/", "prefix for references")
	baseURLStr := flag.String("base_url", "", "base url to interpret repository names")
	repoCacheDir := flag.String("repo_cache", "", "root for repository cache")
	indexDir := flag.String("index", build.DefaultDir, "index directory for *.zoekt files")
	manifestRepoURL := flag.String("manifest_repo_url", "", "set a URL for a git repository holding manifest XML file. Provide the BRANCH:XML-FILE as further command-line arguments")
	manifestRevPrefix := flag.String("manifest_rev_prefix", "refs/remotes/origin/", "prefixes for branches in manifest repository")
	repoName := flag.String("name", "", "set repository name")
	repoURL := flag.String("url", "", "set repository URL")
	maxSubProjects := flag.Int("max_sub_projects", 0, "trim number of projects in manifest, for debugging.")
	incremental := flag.Bool("incremental", true, "only index if the repository has changed.")
	flag.Parse()

	// Tune GOMAXPROCS to match Linux container CPU quota.
	maxprocs.Set()

	if *repoCacheDir == "" {
		log.Fatal("must set --repo_cache")
	}
	repoCache := gitindex.NewRepoCache(*repoCacheDir)

	if u, err := url.Parse(*baseURLStr); err != nil {
		log.Fatalf("Parse(%q): %v", u, err)
	} else if *repoName == "" {
		*repoName = filepath.Join(u.Host, u.Path)
	}

	opts := build.Options{
		Parallelism: *parallelism,
		SizeMax:     *sizeMax,
		ShardMax:    *shardLimit,
		IndexDir:    *indexDir,
		RepositoryDescription: zoekt.Repository{
			Name: *repoName,
			URL:  *repoURL,
		},
	}
	opts.SetDefaults()
	baseURL, err := url.Parse(*baseURLStr)
	if err != nil {
		log.Fatalf("Parse baseURL %q: %v", *baseURLStr, err)
	}

	branches, err := parseBranches(*manifestRepoURL, *manifestRevPrefix, repoCache, flag.Args())
	if err != nil {
		log.Fatalf("parseBranches(%s, %s): %v", *manifestRepoURL, *manifestRevPrefix, err)
	}
	if len(branches) == 0 {
		log.Fatal("must specify at least one branch")
	}
	if *maxSubProjects > 0 {
		for _, b := range branches {
			if *maxSubProjects < len(b.mf.Project) {
				b.mf.Project = b.mf.Project[:*maxSubProjects]
			}
		}
	}

	perBranch := map[string]map[fileKey]gitindex.BlobLocation{}
	opts.SubRepositories = map[string]*zoekt.Repository{}

	// branch => repo => version
	versionMap := map[string]map[string]plumbing.Hash{}
	for _, br := range branches {
		br.mf.Filter()
		files, versions, err := iterateManifest(br.mf, *baseURL, *revPrefix, repoCache)
		if err != nil {
			log.Fatalf("iterateManifest: %v", err)
		}

		perBranch[br.branch] = files
		for key, loc := range files {
			_, ok := opts.SubRepositories[key.SubRepoPath]
			if ok {
				// This can be incorrect: if the layout of manifests
				// changes across branches, then the same file could
				// be in different subRepos. We'll pretend this is not
				// a problem.
				continue
			}

			desc := &zoekt.Repository{}
			if err := gitindex.SetTemplatesFromOrigin(desc, loc.URL); err != nil {
				log.Fatalf("SetTemplatesFromOrigin(%s): %v", loc.URL, err)
			}

			opts.SubRepositories[key.SubRepoPath] = desc
		}
		versionMap[br.branch] = versions
	}

	for _, br := range branches {
		var paths []string
		for p := range opts.SubRepositories {
			paths = append(paths, p)
		}
		sort.Strings(paths)

		// Compute a version of the aggregate. This version
		// has nothing to do with git, but will let us do
		// incrementality correctly.
		hasher := sha1.New()
		for _, p := range paths {
			repo := opts.SubRepositories[p]
			id := versionMap[br.branch][p]

			// it is possible that 'id' is zero, if this
			// branch of the manifest doesn't have this
			// particular subrepository.
			hasher.Write([]byte(p))
			hasher.Write([]byte(id.String()))
			repo.Branches = append(repo.Branches, zoekt.RepositoryBranch{
				Name:    br.branch,
				Version: id.String(),
			})
		}

		opts.RepositoryDescription.Branches = append(opts.RepositoryDescription.Branches, zoekt.RepositoryBranch{
			Name:    br.branch,
			Version: fmt.Sprintf("%x", hasher.Sum(nil)),
		})
	}

	// key => branch
	all := map[fileKey][]string{}
	for br, files := range perBranch {
		for k := range files {
			all[k] = append(all[k], br)
		}
	}

	if *incremental && opts.IncrementalSkipIndexing() {
		return
	}

	builder, err := build.NewBuilder(opts)
	if err != nil {
		log.Fatal(err)
	}
	for k, branches := range all {
		loc := perBranch[branches[0]][k]
		data, err := loc.Blob(&k.ID)
		if err != nil {
			log.Fatal(err)
		}

		doc := zoekt.Document{
			Name:              k.FullPath(),
			Content:           data,
			SubRepositoryPath: k.SubRepoPath,
		}

		doc.Branches = append(doc.Branches, branches...)
		if err := builder.Add(doc); err != nil {
			log.Printf("Add(%s): %v", doc.Name, err)
			break
		}
	}
	if err := builder.Finish(); err != nil {
		log.Fatalf("Finish: %v", err)
	}
}

// getManifest parses the manifest XML at the given branch/path inside a Git repository.
func getManifest(repo *git.Repository, branch, path string) (*manifest.Manifest, error) {
	ref, err := repo.Reference(plumbing.ReferenceName("refs/heads/"+branch), true)
	if err != nil {
		return nil, err
	}

	commit, err := repo.CommitObject(ref.Hash())
	if err != nil {
		return nil, err
	}

	tree, err := repo.TreeObject(commit.TreeHash)
	if err != nil {
		return nil, err
	}

	entry, err := tree.FindEntry(path)
	if err != nil {
		return nil, err
	}

	blob, err := repo.BlobObject(entry.Hash)
	if err != nil {
		return nil, err
	}
	r, err := blob.Reader()
	if err != nil {
		return nil, err
	}
	defer r.Close()

	content, _ := ioutil.ReadAll(r)
	return manifest.Parse(content)
}

// iterateManifest constructs a complete tree from the given Manifest.
func iterateManifest(mf *manifest.Manifest,
	baseURL url.URL, revPrefix string,
	cache *gitindex.RepoCache) (map[fileKey]gitindex.BlobLocation, map[string]plumbing.Hash, error) {
	allFiles := map[fileKey]gitindex.BlobLocation{}
	allVersions := map[string]plumbing.Hash{}
	for _, p := range mf.Project {
		rev := mf.ProjectRevision(&p)

		projURL := baseURL
		projURL.Path = path.Join(projURL.Path, p.Name)

		topRepo, err := cache.Open(&projURL)
		if err != nil {
			return nil, nil, err
		}

		ref, err := topRepo.Reference(plumbing.ReferenceName(revPrefix+rev), true)
		if err != nil {
			return nil, nil, err
		}

		commit, err := topRepo.CommitObject(ref.Hash())
		if err != nil {
			return nil, nil, err
		}
		if err != nil {
			return nil, nil, err
		}

		allVersions[p.GetPath()] = commit.Hash

		tree, err := commit.Tree()
		if err != nil {
			return nil, nil, err
		}

		files, versions, err := gitindex.TreeToFiles(topRepo, tree, projURL.String(), cache)
		if err != nil {
			return nil, nil, err
		}

		for key, repo := range files {
			allFiles[fileKey{
				SubRepoPath: filepath.Join(p.GetPath(), key.SubRepoPath),
				Path:        key.Path,
				ID:          key.ID,
			}] = repo
		}

		for path, version := range versions {
			allVersions[filepath.Join(p.GetPath(), path)] = version
		}
	}

	return allFiles, allVersions, nil
}