package nostr

// Tag is a single NIP-01 tag: a non-empty JSON array of strings whose first
// element names the tag.
type Tag []string

// Tags is the ordered tag list of an event.
type Tags []Tag

// Name returns the tag name, or "" for an empty tag.
func (t Tag) Name() string {
	if len(t) == 0 {
		return ""
	}
	return t[0]
}

// Value returns the first value (index 1) of the tag, or "".
func (t Tag) Value() string {
	if len(t) < 2 {
		return ""
	}
	return t[1]
}

// First returns the value of the first tag with the given name.
func (ts Tags) First(name string) (string, bool) {
	for _, t := range ts {
		if t.Name() == name {
			return t.Value(), true
		}
	}
	return "", false
}

// Values returns every value of every tag with the given name.
func (ts Tags) Values(name string) []string {
	var out []string
	for _, t := range ts {
		if t.Name() == name && len(t) >= 2 {
			out = append(out, t[1])
		}
	}
	return out
}

// Has reports whether a tag with the given name and value exists.
func (ts Tags) Has(name, value string) bool {
	for _, t := range ts {
		if t.Name() == name && t.Value() == value {
			return true
		}
	}
	return false
}

// HasName reports whether any tag with the given name exists.
func (ts Tags) HasName(name string) bool {
	for _, t := range ts {
		if t.Name() == name {
			return true
		}
	}
	return false
}

// DTag returns the first "d" tag value, or "".
func (e *Event) DTag() string {
	v, _ := e.Tags.First("d")
	return v
}

// AppendJSON appends the tag list as a JSON array.
func (ts Tags) AppendJSON(dst []byte) []byte {
	dst = append(dst, '[')
	for i, t := range ts {
		if i > 0 {
			dst = append(dst, ',')
		}
		dst = t.AppendJSON(dst)
	}
	return append(dst, ']')
}

// AppendJSON appends one tag as a JSON array of strings.
func (t Tag) AppendJSON(dst []byte) []byte {
	dst = append(dst, '[')
	for i, s := range t {
		if i > 0 {
			dst = append(dst, ',')
		}
		dst = AppendJSONString(dst, s)
	}
	return append(dst, ']')
}

// IndexableTags calls fn for every single-letter tag that the store indexes.
// NIP-01 only defines filters for single-letter tag names; multi-letter tags
// are not indexed.
func (ts Tags) IndexableTags(fn func(name string, value string)) {
	for _, t := range ts {
		if len(t) < 2 {
			continue
		}
		if len(t[0]) != 1 {
			continue
		}
		fn(t[0], t[1])
	}
}