/*
SGBlog -- Git-backed CGI/inetd blogging/phlogging engine
Copyright (C) 2020-2021 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/>.
*/

package main

import (
	"bufio"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"strconv"
	"strings"
	"text/template"

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

const (
	TmplGopherMenu = `{{$CR := printf "\r"}}{{$CRLF := printf "\r\n" -}}
{{- define "domainPort" }}	{{.GopherDomain}}	70{{end}}{{$Cfg := .Cfg -}}
i{{.Cfg.Title}} {{if .Topic}}(topic: {{.Topic}}) {{end}}({{.Offset}}-{{.OffsetNext}})	err{{template "domainPort" .Cfg}}{{$CRLF -}}
{{- if .Cfg.AboutURL}}hAbout	URL:{{.Cfg.AboutURL}}{{template "domainPort" .Cfg}}{{$CRLF}}{{end -}}
{{- if .Offset}}1Prev	{{if .Topic}}{{.Topic}}/{{end}}offset/{{.OffsetPrev}}{{template "domainPort" .Cfg}}{{$CRLF}}{{end -}}
{{- if not .LogEnded}}1Next	{{if .Topic}}{{.Topic}}/{{end}}offset/{{.OffsetNext}}{{template "domainPort" .Cfg}}{{$CRLF}}{{end -}}
{{- $datePrev := "0001-01-01" -}}
{{- range .Entries -}}
{{- $dateCur := .Commit.Author.When.Format "2006-01-02" -}}
{{- if ne $dateCur $datePrev}}{{$datePrev = $dateCur}}
i{{$dateCur}}	err{{template "domainPort" $Cfg}}{{$CR}}{{end}}
0[{{.Commit.Author.When.Format "15:04"}}] {{.Title}} ({{.LinesNum}}L){{with .CommentsNum}} ({{.}}C){{end}}{{if .Topics}}{{range .Topics}} {{.}}{{end}}{{end}}	/{{.Commit.Hash.String}}{{template "domainPort" $Cfg}}{{$CR}}{{end}}
{{range .Topics}}
1Topic: {{.}}	{{.}}/offset/0{{template "domainPort" $Cfg}}{{$CR}}{{end}}
iGenerated by: SGBlog {{.Version}}	err{{template "domainPort" .Cfg}}{{$CR}}
.{{$CRLF}}`
	TmplGopherEntry = `What: {{.Commit.Hash.String}}
When: {{.When}}
------------------------------------------------------------------------
{{if .Topics}}Topics:{{range .Topics}} {{.}}{{end}}{{end}}
------------------------------------------------------------------------
{{.Commit.Message -}}
{{- if .Note}}
------------------------------------------------------------------------
Note:
{{.Note}}{{end -}}
{{- if .Cfg.CommentsEmail}}
------------------------------------------------------------------------
leave comment: mailto:{{.Cfg.CommentsEmail}}?subject={{.Commit.Hash.String}}
{{end}}{{range $idx, $comment := .Comments}}
------------------------------------------------------------------------
comment {{$idx}}:
{{$comment}}
{{end}}
------------------------------------------------------------------------
Generated by: SGBlog {{.Version}}
`
)

type TableMenuEntry struct {
	Commit      *object.Commit
	Title       string
	LinesNum    int
	CommentsNum int
	Topics      []string
}

func serveGopher() {
	cfgPath := os.Args[2]
	cfgRaw, err := ioutil.ReadFile(cfgPath)
	if err != nil {
		log.Fatalln(err)
	}
	var cfgGeneral map[string]interface{}
	if err = hjson.Unmarshal(cfgRaw, &cfgGeneral); err != nil {
		log.Fatalln(err)
	}
	cfgRaw, err = json.Marshal(cfgGeneral)
	if err != nil {
		log.Fatalln(err)
	}
	var cfg *Cfg
	if err = json.Unmarshal(cfgRaw, &cfg); err != nil {
		log.Fatalln(err)
	}
	if cfg.GopherDomain == "" {
		log.Fatalln("GopherDomain is not configured")
	}

	headHash, err := initRepo(cfg)
	if err != nil {
		log.Fatalln(err)
	}

	scanner := bufio.NewScanner(io.LimitReader(os.Stdin, 1<<8))
	if !scanner.Scan() {
		log.Fatalln(errors.New("no CRLF found"))
	}
	selector := scanner.Text()
	if selector == "" {
		selector = "offset/0"
	}
	selectorParts := strings.Split(selector, "/")
	if strings.HasPrefix(selector, "URL:") {
		selector = selector[len("URL:"):]
		fmt.Printf(`<html>
<head>
	<meta http-equiv="Refresh" content="1; url=%s" />
	<title>Redirect to non-gopher URL</title>
</head>
<body>
Redirecting to <a href="%s">%s</a>...
</body>
</html>
`, selector, selector, selector)
	} else if sha1DigestRe.MatchString(selector) {
		commit, err := repo.CommitObject(plumbing.NewHash(selector[1:]))
		if err != nil {
			log.Fatalln(err)
		}
		tmpl := template.Must(template.New("entry").Parse(TmplGopherEntry))
		err = tmpl.Execute(os.Stdout, struct {
			Commit   *object.Commit
			When     string
			Cfg      *Cfg
			Note     string
			Comments []string
			Topics   []string
			Version  string
		}{
			Commit:   commit,
			When:     commit.Author.When.Format(sgblog.WhenFmt),
			Cfg:      cfg,
			Note:     string(getNote(notesTree, commit.Hash)),
			Comments: parseComments(getNote(commentsTree, commit.Hash)),
			Topics:   parseTopics(getNote(topicsTree, commit.Hash)),
			Version:  sgblog.Version,
		})
		if err != nil {
			log.Fatalln(err)
		}
	} else if selectorParts[len(selectorParts)-2] == "offset" {
		offset, err := strconv.Atoi(selectorParts[len(selectorParts)-1])
		if err != nil {
			log.Fatalln(err)
		}
		repoLog, err := repo.Log(&git.LogOptions{From: *headHash})
		if err != nil {
			log.Fatalln(err)
		}
		topicsCache, err := getTopicsCache(cfg, repoLog)
		if err != nil {
			log.Fatalln(err)
		}
		repoLog, err = repo.Log(&git.LogOptions{From: *headHash})
		if err != nil {
			log.Fatalln(err)
		}

		var topic string
		if len(selectorParts) == 3 {
			topic = selectorParts[0]
		}
		var commits CommitIterNext
		if topic == "" {
			for i := 0; i < offset; i++ {
				if _, err = repoLog.Next(); err != nil {
					break
				}
			}
			commits = repoLog
		} else {
			hashes := topicsCache[topic]
			if hashes == nil {
				log.Fatalln(errors.New("no posts with that topic"))
			}
			if len(hashes) > offset {
				hashes = hashes[offset:]
			}
			commits = &HashesIter{hashes}
		}

		logEnded := false
		entries := make([]TableMenuEntry, 0, PageEntries)
		for i := 0; i < PageEntries; i++ {
			commit, err := commits.Next()
			if err != nil {
				logEnded = true
				break
			}
			lines := msgSplit(commit.Message)
			entries = append(entries, TableMenuEntry{
				Commit:      commit,
				Title:       lines[0],
				LinesNum:    len(lines) - 2,
				CommentsNum: len(parseComments(getNote(commentsTree, commit.Hash))),
				Topics:      parseTopics(getNote(topicsTree, commit.Hash)),
			})
		}
		tmpl := template.Must(template.New("menu").Parse(TmplGopherMenu))
		offsetPrev := offset - PageEntries
		if offsetPrev < 0 {
			offsetPrev = 0
		}
		err = tmpl.Execute(os.Stdout, struct {
			Cfg        *Cfg
			Topic      string
			Offset     int
			OffsetPrev int
			OffsetNext int
			LogEnded   bool
			Entries    []TableMenuEntry
			Topics     []string
			Version    string
		}{
			Cfg:        cfg,
			Topic:      topic,
			Offset:     offset,
			OffsetPrev: offsetPrev,
			OffsetNext: offset + PageEntries,
			LogEnded:   logEnded,
			Entries:    entries,
			Topics:     topicsCache.Topics(),
			Version:    sgblog.Version,
		})
		if err != nil {
			log.Fatalln(err)
		}
	} else {
		log.Fatalln(errors.New("unknown selector"))
	}
}