package atom

import (
	"encoding/xml"
	"fmt"
	"strings"
	"time"
)

// It is advisable that each atom:entry element contain a non-empty atom:title
// element, a non-empty atom:content element when that element is present, and
// a non-empty atom:summary element when the entry contains no atom:content
// element.
type Entry struct {
	XMLName xml.Name `xml:"entry"`
	*CommonAttributes
	Authors      []*Person   `xml:"author,omitempty"`
	Categories   []*Category `xml:",omitempty"`
	Content      Content     `xml:",omitempty"`
	Contributors []*Person   `xml:"contributors,omitempty"`
	ID           *ID
	Links        []*Link             `xml:",omitempty"`
	Published    *Date               `xml:"published,omitempty"`
	Rights       Text                `xml:"rights,omitempty"`
	Source       *Source             `xml:",omitempty"`
	Summary      Text                `xml:"summary,omitempty"`
	Title        Text                `xml:"title"`
	Updated      *Date               `xml:"updated"`
	Extensions   []*ExtensionElement `xml:",any,omitempty"`
}

// checkAuthors checks the entry's authors for incompatibilities with RFC4287.
// It returns an errors.
// atom:entry elements MUST contain one or more atom:author elements, unless
// the atom:entry contains an atom:source element that contains an atom:author
// element or, in an Atom Feed Document, the atom:feed element contains an
// atom:author element itself.
func (e *Entry) checkAuthors(authorInFeed bool) error {
	if e.Authors == nil {
		if !authorInFeed {
			if e.Source == nil {
				return fmt.Errorf("no authors set in entry %v", e)
			}
			if e.Source.Authors == nil {
				return fmt.Errorf("no authors set in entry %v", e)
			}
		}
	} else {
		for i, a := range e.Authors {
			if err := a.Check(); err != nil {
				return fmt.Errorf("author element %v of entry %v: %v", i, e, err)
			}
		}
	}

	return nil
}

// NewEntry creates a new Entry. It returns a *Entry.
func NewEntry(title string) *Entry {
	return &Entry{
		CommonAttributes: newCommonAttributes(),
		ID:               NewID(NewURN()),
		Title:            NewText("text", title),
		Updated:          NewDate(time.Now()),
	}
}

// AddAuthor adds the Person as an author to the Entry.
func (e *Entry) AddAuthor(p *Person) {
	if e.Authors == nil {
		e.Authors = make([]*Person, 1)
		e.Authors[0] = p
	} else {
		e.Authors = append(e.Authors, p)
	}

	e.Updated.DateTime = DateTime(time.Now())
}

// AddCategory adds the Category to the Entry.
func (e *Entry) AddCategory(c *Category) {
	if e.Categories == nil {
		e.Categories = make([]*Category, 1)
		e.Categories[0] = c
	} else {
		e.Categories = append(e.Categories, c)
	}

	e.Updated.DateTime = DateTime(time.Now())
}

// AddContributor adds the Person as a contributor to the Entry.
func (e *Entry) AddContributor(c *Person) {
	if e.Contributors == nil {
		e.Contributors = make([]*Person, 1)
		e.Contributors[0] = c
	} else {
		e.Contributors = append(e.Contributors, c)
	}

	e.Updated.DateTime = DateTime(time.Now())
}

// AddLink adds the Link to the Entry.
func (e *Entry) AddLink(l *Link) {
	if e.Links == nil {
		e.Links = make([]*Link, 1)
		e.Links[0] = l
	} else {
		e.Links = append(e.Links, l)
	}

	e.Updated.DateTime = DateTime(time.Now())
}

// AddExtension adds the ExtensionElement to the Entry.
func (e *Entry) AddExtension(x *ExtensionElement) {
	if e.Extensions == nil {
		e.Extensions = make([]*ExtensionElement, 1)
		e.Extensions[0] = x
	} else {
		e.Extensions = append(e.Extensions, x)
	}

	e.Updated.DateTime = DateTime(time.Now())
}

// Check checks the Entry for incompatibilities with RFC4287. It returns an
// error.
func (e *Entry) Check() error {
	if e.ID == nil {
		return fmt.Errorf("no id element of entry %v", e)
	} else {
		if err := e.ID.Check(); err != nil {
			return fmt.Errorf("id element of entry %v: %v", e, err)
		}
	}

	if err := e.checkAuthors(true); err != nil {
		return fmt.Errorf("entry %v: %v", e, err)
	}

	for i, c := range e.Categories {
		if err := c.Check(); err != nil {
			return fmt.Errorf("category element %v of entry %v: %v", i, e, err)
		}
	}

	if e.Content != nil {
		if err := e.Content.Check(); err != nil {
			return fmt.Errorf("content element of entry %v: %v", e, err)
		}
	} else {
		// atom:entry elements that contain no child atom:content element MUST
		// contain at least one atom:link element with a rel attribute value of
		// "alternate".
		if !alternateRelExists(e.Links) {
			return fmt.Errorf("no content element of entry %v and no link element with rel \"alternate\"", e)
		}
	}

	for i, c := range e.Contributors {
		if err := c.Check(); err != nil {
			return fmt.Errorf("contributor element %v of entry %v: %v", i, e, err)
		}
	}

	for i, l := range e.Links {
		if err := l.Check(); err != nil {
			return fmt.Errorf("link element %v of entry %v: %v", i, e, err)
		}
	}
	if hasAlternateDuplicateLinks(e.Links) {
		return fmt.Errorf("links with a rel attribute value of \"alternate\" and duplicate type and hreflang attribute values found in entry %v", e)
	}

	if e.Published != nil {
		if err := e.Published.Check(); err != nil {
			return fmt.Errorf("published element of entry %v: %v", e, err)
		}
	}

	if e.Rights != nil {
		if err := e.Rights.Check(); err != nil {
			return fmt.Errorf("rights element of entry %v: %v", e, err)
		}
	}

	if e.Source != nil {
		if err := e.Source.Check(); err != nil {
			return fmt.Errorf("source element of entry %v: %v", e, err)
		}
	}

	if e.Summary != nil {
		if err := e.Summary.Check(); err != nil {
			return fmt.Errorf("summary element of entry %v: %v", e, err)
		}
	} else {
		// atom:entry elements MUST contain an atom:summary element in either
		// of the following cases:
		// the atom:entry contains an atom:content that has a "src" attribute
		// (and is thus empty).
		if e.Content.hasSRC() {
			return fmt.Errorf("no summary element of entry %v but content of type out of line content", e)
		}
		// the atom:entry contains content that is encoded in Base64; i.e., the
		// "type" attribute of atom:content is a MIME media type [MIMEREG], but
		// is not an XML media type [RFC3023], does not begin with "text/", and
		// does not end with "/xml" or "+xml".
		mediaType := e.Content.getType()
		if isValidMediaType(mediaType) && !isXMLMediaType(mediaType) && !strings.HasPrefix(mediaType, "text/") {
			return fmt.Errorf("no summary element of entry %v but media type not xml", e)
		}
	}

	if e.Title == nil {
		return fmt.Errorf("no title element of entry %v", e)
	} else {
		if err := e.Title.Check(); err != nil {
			return fmt.Errorf("title element of entry %v: %v", e, err)
		}
	}

	if e.Updated == nil {
		return fmt.Errorf("no updated element of entry %v", e)
	} else {
		if err := e.Updated.Check(); err != nil {
			return fmt.Errorf("updated element of entry %v: %v", e, err)
		}
	}

	for i, x := range e.Extensions {
		if err := x.Check(); err != nil {
			return fmt.Errorf("extension element %v of entry %v: %v", i, e, err)
		}
	}

	return nil
}

// ToXML converts the Feed to XML. It returns a string and an error.
func (e *Entry) ToXML(encoding string) (string, error) {
	xml, err := xml.MarshalIndent(e, "", "  ")
	if err != nil {
		return "", fmt.Errorf("error xml encoding entry: %v", err)
	}

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