// 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 makeworld's amfora:
// https://github.com/makeworld-the-better-one/amfora/blob/master/subscriptions/structs.go
// Original source is Copyright 2020 makeworld and is licensed under the
// terms of the GNU General Public License Version 3.0.
// https://www.gnu.org/licenses/gpl-3.0-standalone.html

package core

import (
	"reflect"
	"sync"
	"time"

	"github.com/mmcdole/gofeed"
)

// FullData is used for both reading from json and for storing the global feeds
// map. contains read mutexes so concurrency can be used.
type FullData struct {
	Feeds map[string]*Feed `json:"feeds,omitempty"`
	Pages map[string]*Page `json:"pages,omitempty"`

	FeedsMu *sync.RWMutex `json:"-"`
	PagesMu *sync.RWMutex `json:"-"`
}

// Feed holds all the necessary fields when storing a feed
type Feed struct {
	Title    string    `json:"title,omitempty"`
	Link     string    `json:"link,omitempty"`     // link to the human-readable page for the feed. same as FeedLink for gemini feeds.
	FeedLink string    `json:"feedlink,omitempty"` // link to the feed itself.
	Updated  time.Time `json:"updated,omitempty"`
	Items    []*Item   `json:"items,omitempty"`
}

// Item is a single item from a subscripton
type Item struct {
	Title     string    `json:"title,omitempty"` // if empty, use Link as title
	Content   string    `json:"content,omitempty"`
	Link      string    `json:"link,omitempty"`
	Published time.Time `json:"updated,omitempty"`
}

// Page holds all the necessary fields when storing a page being watched for
// changes.
type Page struct {
	Title   string    `json:"title,omitempty"`
	Link    string    `json:"link,omitempty"`
	Updated time.Time `json:"updated,omitempty"`
	Hash    string    `json:"hash,omitempty"`
}

// gofeedConvert converts a gofeed.Feed into a Feed struct
func GofeedConvert(f *gofeed.Feed, title string) (*Feed, error) {
	new := &Feed{}

	if title != "" {
		new.Title = title
	} else {
		new.Title = f.Title
	}
	if f.UpdatedParsed != nil {
		new.Updated = *f.UpdatedParsed
	} else if f.PublishedParsed != nil {
		new.Updated = *f.PublishedParsed
	}
	new.Link = f.Link
	new.FeedLink = f.FeedLink

	for _, v := range f.Items {
		item := &Item{}
		item.Title = v.Title
		item.Content = v.Content
		if v.UpdatedParsed != nil {
			item.Published = *v.UpdatedParsed
		} else if v.PublishedParsed != nil {
			item.Published = *v.PublishedParsed
		}
		item.Link = v.Link

		new.Items = append(new.Items, item)
	}

	return new, nil
}

// InsertFeed will insert or update a core.Feed in a core.FullData
func (d *FullData) InsertFeed(new *Feed, remote string) {
	d.FeedsMu.Lock()
	oldFeed, ok := d.Feeds[remote]
	if !ok || !reflect.DeepEqual(new, oldFeed) {
		// Feeds are different, or there was never an old one
		if oldFeed != nil && oldFeed.Title != "" {
			new.Title = oldFeed.Title
		}
		d.Feeds[remote] = new
		d.FeedsMu.Unlock()
	} else {
		d.FeedsMu.Unlock()
	}
}

// InsertPage will insert or update a core.Page in a core.FullData
func (d *FullData) InsertPage(new *Page, remote string) {
	d.PagesMu.Lock()
	oldPage, ok := d.Pages[remote]
	if !ok || d.Pages[remote].Hash != new.Hash {
		// pages are different, or there was never an old one
		if oldPage != nil && new.Title == "" && oldPage.Title != "" {
			new.Title = oldPage.Title
		}
		d.Pages[remote] = new
		d.PagesMu.Unlock()
	} else {
		d.PagesMu.Unlock()
	}
}

// Implement sort.Interface for Feed

// Len returns the length of Items.
func (f *Feed) Len() int {
	return len(f.Items)
}

// Less compares Published of Items[i], Items[k] and returns true if Items[i] is
// before Items[j].
func (f *Feed) Less(i, j int) bool {
	return f.Items[i].Published.Before(f.Items[j].Published)
}

// Swap swaps Items[i] and Items[j].
func (f *Feed) Swap(i, j int) {
	f.Items[i], f.Items[j] = f.Items[j], f.Items[i]
}

// Lock locks both feed and page mutexes.
func (j *FullData) Lock() {
	j.FeedsMu.Lock()
	j.PagesMu.Lock()
}

// Unlock unlocks both feed and page mutexes.
func (j *FullData) Unlock() {
	j.FeedsMu.Unlock()
	j.PagesMu.Unlock()
}

// RLock read-locks both feed and page mutexes.
func (j *FullData) RLock() {
	j.FeedsMu.RLock()
	j.PagesMu.RLock()
}

// RUnlock read-unlocks both feed and page mutexes.
func (j *FullData) RUnlock() {
	j.FeedsMu.RUnlock()
	j.PagesMu.RUnlock()
}

// PageEntry is a single item on a subscriptions page. It is used for both feeds
// and pages.
type PageEntry struct {
	Prefix    string // whatever goes before the post title to identify the feed.
	Title     string // article/entry title
	URL       string
	Published time.Time
}

// PageEntries is reverse chronological list of entries used when generating subs.
type PageEntries struct {
	Entries []*PageEntry
}

// Implement sort.Interface for PageEntries

// Len returns the length of Entries
func (e *PageEntries) Len() int {
	return len(e.Entries)
}

// Less compares the Published if Entries[i], Entries[j] and returns true if
// Entries[i] is /after/ Entries[j] (for reverse chronological sorting)
func (e *PageEntries) Less(i, j int) bool {
	return e.Entries[i].Published.After(e.Entries[j].Published)
}

// Swap swaps Entries[i] and Entries[j]
func (e *PageEntries) Swap(i, j int) {
	e.Entries[i], e.Entries[j] = e.Entries[j], e.Entries[i]
}