/*
SGBlog -- Git-backed CGI/UCSPI blogging/phlogging/gemlogging engine
Copyright (C) 2020-2023 Sergey Matveev <stargrave@stargrave.org>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as
published by the Free Software Foundation, version 3 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

// Git-backed CGI/UCSPI blogging/phlogging/gemlogging engine
package main

import (
	"flag"
	"fmt"
	"log"
	"sort"

	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/object"
	"go.stargrave.org/sgblog"
)

func main() {
	branch := flag.String("branch", "refs/heads/master", "Blog's branch reference name")
	topicsRefName := flag.String("topics-ref", "refs/notes/topics", "Topics reference name")
	flag.Usage = func() {
		fmt.Fprintln(flag.CommandLine.Output(), "Show known topics")
		flag.PrintDefaults()
	}
	flag.Parse()
	log.SetFlags(0)

	repo, err := git.PlainOpen(".")
	if err != nil {
		log.Fatalln(err)
	}
	head, err := repo.Reference(plumbing.ReferenceName(*branch), false)
	if err != nil {
		log.Fatalln(err)
	}
	headHash := head.Hash()

	var topicsRef *plumbing.Reference
	var topicsTree *object.Tree
	if notes, err := repo.Notes(); err == nil {
		notes.ForEach(func(ref *plumbing.Reference) error {
			if string(ref.Name()) == *topicsRefName {
				topicsRef = ref
			}
			return nil
		})
		if topicsRef != nil {
			if topicsCommit, err := repo.CommitObject(topicsRef.Hash()); err == nil {
				topicsTree, _ = topicsCommit.Tree()
			}
		}
	}

	repoLog, err := repo.Log(&git.LogOptions{From: headHash})
	if err != nil {
		log.Fatalln(err)
	}
	topicsCounter := map[string]int{}
	for {
		commit, err := repoLog.Next()
		if err != nil {
			break
		}
		for _, topic := range sgblog.ParseTopics(sgblog.GetNote(repo, topicsTree, commit.Hash)) {
			topicsCounter[topic]++
		}
	}
	topics := make([]string, 0, len(topicsCounter))
	for topic := range topicsCounter {
		topics = append(topics, topic)
	}
	sort.Strings(topics)
	for _, topic := range topics {
		fmt.Printf("%s\t%d\n", topic, topicsCounter[topic])
	}
}