// Copyright (C) 2021 nytpu
// SPDX-License-Identifier: AGPL-3.0-or-later
// For more license details, see LICENSE or <https://www.gnu.org/licenses/agpl-3.0.html>.

// This file incorporates code from Drew DeVault's gemreader:
// https://git.sr.ht/~sircmpwn/gemreader/tree/master/item/feeds/fetch.go
// Original source is Copyright 2021 Drew DeVault and is licensed under the
// terms of the GNU Affero General Public License Version 3.0.
// https://www.gnu.org/licenses/agpl-3.0-standalone.html

package fetch

import (
	"context"
	"crypto/sha256"
	"fmt"
	"io"
	"mime"
	"net/url"
	"strings"
	"time"

	"git.sr.ht/~adnano/go-gemini"
	"github.com/mmcdole/gofeed"

	"golang.nytpu.com/comitium/core"
)

// fetchGemini will make a request for a gemini resource
func fetchGemini(remoteURL *url.URL) (*gemini.Response, error) {
	client := &gemini.Client{}
	resp, err := client.Get(context.Background(), remoteURL.String())
	if err != nil {
		return nil, err
	}
	if resp.Status != gemini.StatusSuccess {
		return nil, fmt.Errorf("Unexpected Gemini response: %d %s", resp.Status, resp.Meta)
	}

	return resp, nil
}

// newGeminiFeed will fetch and create a new core.Feed given a gemini url
func newGeminiFeed(remoteURL *url.URL, title string) (*core.Feed, error) {
	resp, err := fetchGemini(remoteURL)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	mimetype, _, err := mime.ParseMediaType(resp.Meta)
	if err != nil {
		return nil, fmt.Errorf("Unintelligible content type: %s", resp.Meta)
	}

	reader := io.LimitReader(resp.Body, 1073741824) // 1 GiB

	switch mimetype {
	case "text/gemini":
		var feed core.Feed
		feed.Title = title // will be set later if given title is ""
		feed.Link = remoteURL
		text, err := gemini.ParseText(resp.Body)
		if err != nil {
			return nil, err
		}
		for _, line := range text {
			switch line := line.(type) {
			case gemini.LineHeading1:
				if feed.Title == "" {
					feed.Title = strings.TrimLeft(line.String(), "# ")
				}
			case gemini.LineLink:
				if line.Name == "" || len(line.Name) < 10 {
					continue
				}
				name := strings.TrimLeft(line.Name[:10], " -—")
				date, err := time.Parse("2006-01-02", name)
				if err != nil {
					continue
				}
				link, err := url.Parse(line.URL)
				if err != nil {
					continue
				}
				link = remoteURL.ResolveReference(link)
				item := &core.Item{}
				item.Title = strings.TrimLeft(line.Name[10:], ": ")
				item.Published = date
				item.Link = link
				feed.Items = append(feed.Items, item)
			}
		}
		return &feed, nil
	case "text/xml",
		"application/rss+xml",
		"application/atom+xml",
		"application/xml",
		"application/json":
		gofeed, err := gofeed.NewParser().Parse(reader)
		if err != nil {
			return nil, err
		}
		feed, err := core.GofeedConvert(gofeed, title)
		return feed, err
	default:
		return nil, fmt.Errorf("Cannot interpret %s as a feed", resp.Meta)
	}
}

// newGeminiPage will create a new core.Page given a gemini url
func newGeminiPage(remoteURL *url.URL, title string) (*core.Page, error) {
	resp, err := fetchGemini(remoteURL)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	reader := io.LimitReader(resp.Body, 1073741824) // 1 GiB

	var page core.Page
	page.Title = title
	page.Link = remoteURL
	page.Updated = time.Now()

	h := sha256.New()
	if _, err := io.Copy(h, reader); err != nil {
		return nil, err
	}
	page.Hash = fmt.Sprintf("%x", h.Sum(nil))

	return &page, nil
}