// Package tequat implements parsing of mail messages
// into categories of "Text, Quotes, Attachment".
package tequat

import (
    "mime"
    "net/textproto"
)

// "Text, Quotes, Attachments"
type TQA []Atom

type Atom interface { isatom() }

type Text struct {
    Raw string
}
func (_ Text) isatom() {}

type Quote struct {
    Raw string
}
func (_ Quote) isatom() {}

type SignatureBlock struct {
    // leading "-- \n" is stripped
    Raw string
}
func (_ SignatureBlock) isatom() {}

type DroppedAlternatives struct {
    MediatypeTs []string
}
func (_ DroppedAlternatives) isatom() {}

//

type Attachment struct {
    Inline bool

    // Header should contain a singular, non-empty value keyed "Content-Type".
    // Header may be nil.
    Header textproto.MIMEHeader

    Data []byte
}
func (_ Attachment) isatom() {}

func (attachment Attachment) ContentType() string {
    return GetUnique(attachment.Header, "Content-Type")
}

// may be empty
// TODO This is not the whole story. (See: "Content-Type: application/pdf; name=..." or "Content-Disposition: attachment; filename=...")
func (attachment Attachment) Ext() string {
    exts, err := mime.ExtensionsByType(attachment.ContentType())
    if err == nil && len(exts) > 0 {
        return exts[0]
    }
    return ""
}

//

func GetUnique(header textproto.MIMEHeader, key string) string {
    if header == nil || len(header.Values(key)) != 1 {
        return ""
    }
    return header.Get(key)
}