package rss

import (
	"encoding/xml"
	"fmt"
)

type Image struct {
	XMLName xml.Name `xml:"image"`
	Url     string   `xml:"url"`
	Title   string   `xml:"title"`
	Link    string   `xml:"link"`
	Width   int      `xml:"width,omitempty"`  // max: 144, default: 88
	Height  int      `xml:"height,omitempty"` // max: 400, default: 31
}

type TextInput struct {
	XMLName     xml.Name `xml:"textInput"`
	Title       string   `xml:"title,omitempty"`
	Description string   `xml:"description,omitempty"`
	Name        string   `xml:"name,omitempty"`
	Link        string   `xml:"link,omitempty"`
}

type Enclosure struct {
	XMLName xml.Name `xml:"enclosure"`
	Url     string   `xml:"url,attr"`
	Type    string   `xml:"type,attr"`
	Lenght  int      `xml:"lenght,attr"`
}

type Source struct {
	XMLName xml.Name `xml:"source"`
	Url     string   `xml:"url,attr"`
	Value   string
}

type Content struct {
	XMLName xml.Name `xml:"content:encoded"`
	Value   string   `xml:",cdata"`
}

type Item struct {
	XMLName     xml.Name `xml:"item"`
	Title       string   `xml:"title,omitempty"`
	Link        string   `xml:"link,omitempty"`
	Description string   `xml:"description,omitempty"`
	Author      string   `xml:"author,omitempty"`
	Comments    string   `xml:"comments,omitempty"`
	Enclosure   *Enclosure
	Guid        string `xml:"guid,omitempty"`
	PubDate     string `xml:"pubDate,omitempty"`
	Source      *Source
	Content     *Content
	Categories  []string `xml:"category,omitempty"`
}

type Channel struct {
	XMLName        xml.Name `xml:"channel"`
	Title          string   `xml:"title"`
	Link           string   `xml:"link"`
	Description    string   `xml:"description"`
	Language       string   `xml:"language,omitempty"`
	Copyright      string   `xml:"copyright,omitempty"`
	ManagingEditor string   `xml:"managingEditor,omitempty"`
	WebMaster      string   `xml:"webMaster,omitempty"`
	PubDate        string   `xml:"pubDate,omitempty"`
	LastBuildDate  string   `xml:"lastBuildDate,omitempty"`
	Categories     []string `xml:"category,omitempty"`
	Generator      string   `xml:"generator,omitempty"`
	Docs           string   `xml:"docs,omitempty"`
	Cloud          string   `xml:"cloud,omitempty"`
	Image          *Image
	Rating         string `xml:"rating,omitempty"`
	TextInput      *TextInput
	SkipHours      []int `xml:"skipHours,omitempty"`
	SkipDays       []int `xml:"skipDays,omitempty"`
	Items          []*Item
	Ttl            int `xml:"ttl,omitempty"`
}

type Feed struct {
	XMLName          xml.Name `xml:"rss"`
	Version          string   `xml:"version,attr"`
	ContentNamespace string   `xml:"xmlns:content,attr"`
	Channels         []*Channel
}

func (i *Image) check() error {
	if len(i.Url) == 0 {
		return fmt.Errorf("error: url not set")
	}
	if len(i.Title) == 0 {
		return fmt.Errorf("error: title not set")
	}
	if len(i.Link) == 0 {
		return fmt.Errorf("error: link not set")
	}
	if i.Width == 0 || i.Width > 144 {
		i.Width = 88
	}
	if i.Height == 0 || i.Height > 400 {
		i.Height = 31
	}

	return nil
}

func (t *TextInput) check() error {
	if len(t.Title) == 0 &&
		len(t.Description) == 0 &&
		len(t.Name) == 0 &&
		len(t.Link) == 0 {
		return fmt.Errorf("error: textInput is empty")
	}

	return nil
}

func (e *Enclosure) check() error {
	if len(e.Url) == 0 {
		return fmt.Errorf("error: url not set")
	}
	if e.Lenght == 0 {
		return fmt.Errorf("error: length not set or 0")
	}
	if len(e.Type) == 0 {
		return fmt.Errorf("error: type not set")
	}

	return nil
}

func (s *Source) check() error {
	if len(s.Url) == 0 {
		return fmt.Errorf("error: url not set")
	}
	if len(s.Value) == 0 {
		return fmt.Errorf("error: value not set")
	}

	return nil
}

func (c *Content) check() error {
	if len(c.Value) == 0 {
		return fmt.Errorf("error: value not set")
	}

	return nil
}

func (i *Item) check() error {
	if len(i.Title) == 0 && len(i.Description) == 0 {
		return fmt.Errorf("error: neither title nor description set")
	}

	if i.Enclosure != nil {
		if err := i.Enclosure.check(); err != nil {
			return fmt.Errorf("error checking enclosure: %v", err)
		}
	}

	if i.Source != nil {
		if err := i.Source.check(); err != nil {
			return fmt.Errorf("error checking source: %v", err)
		}
	}

	if i.Content != nil {
		if err := i.Content.check(); err != nil {
			return fmt.Errorf("error checking content: %v", err)
		}
	}

	return nil
}

func (c *Channel) check() error {
	if len(c.Title) == 0 {
		return fmt.Errorf("error: title not set")
	}
	if len(c.Link) == 0 {
		return fmt.Errorf("error: link not set")
	}
	if len(c.Description) == 0 {
		return fmt.Errorf("error: description not set")
	}

	if c.Image != nil {
		if err := c.Image.check(); err != nil {
			return fmt.Errorf("error checking image: %v", err)
		}
	}

	if c.TextInput != nil {
		if err := c.TextInput.check(); err != nil {
			return fmt.Errorf("error checking textInput: %v", err)
		}
	}

	for _, item := range c.Items {
		if err := item.check(); err != nil {
			return fmt.Errorf("error checking item: %v", err)
		}
	}

	return nil
}

func (f *Feed) check() error {
	if f.Channels == nil {
		return fmt.Errorf("error: feed has no channels")
	}
	for _, channel := range f.Channels {
		if err := channel.check(); err != nil {
			return fmt.Errorf("error checking channel: %v", err)
		}
	}

	return nil
}

func NewFeed() *Feed {
	return &Feed{
		Version:          "2.0",
		ContentNamespace: "http://purl.org/rss/1.0/modules/content/",
		Channels:         make([]*Channel, 0),
	}
}

func (f *Feed) ToXML(encoding string) (string, error) {
	if err := f.check(); err != nil {
		return "", fmt.Errorf("error checking RSS feed: %v", err)
	}

	xml, err := xml.MarshalIndent(f, "", "  ")
	if err != nil {
		return "", fmt.Errorf("error XML encoding feed: %v", err)
	}

	return `<?xml version="1.0" encoding="` + encoding + `"?>` + string(xml), nil
}