package lib

import (
	"bufio"
	"io"
	"mime"
	"net/http"
	"os"
	"path/filepath"

	"github.com/emersion/go-message/mail"
	"github.com/pkg/errors"
)

type Part struct {
	MimeType string
	Params   map[string]string
	Body     io.Reader
}

func NewPart(mimetype string, params map[string]string, body io.Reader) *Part {
	return &Part{
		MimeType: mimetype,
		Params:   params,
		Body:     body,
	}
}

type Attachment interface {
	Name() string
	WriteTo(w *mail.Writer) error
}

type FileAttachment struct {
	path string
}

func NewFileAttachment(path string) *FileAttachment {
	return &FileAttachment{
		path,
	}
}

func (fa *FileAttachment) Name() string {
	return fa.path
}

func (fa *FileAttachment) WriteTo(w *mail.Writer) error {
	f, err := os.Open(fa.path)
	if err != nil {
		return errors.Wrap(err, "os.Open")
	}
	defer f.Close()

	reader := bufio.NewReader(f)

	// if we have an extension, prefer that instead of trying to sniff the header.
	// That's generally more accurate than sniffing as lots of things are zip files
	// under the hood, e.g. most office file types
	ext := filepath.Ext(fa.path)
	var mimeString string
	if mimeString = mime.TypeByExtension(ext); mimeString != "" {
		// found it in the DB
	} else {
		// Sniff the mime type instead
		// http.DetectContentType only cares about the first 512 bytes
		head, err := reader.Peek(512)
		if err != nil && err != io.EOF {
			return errors.Wrap(err, "Peek")
		}
		mimeString = http.DetectContentType(head)
	}

	// mimeString can contain type and params (like text encoding),
	// so we need to break them apart before passing them to the headers
	mimeType, params, err := mime.ParseMediaType(mimeString)
	if err != nil {
		return errors.Wrap(err, "ParseMediaType")
	}
	filename := filepath.Base(fa.path)
	params["name"] = filename

	// set header fields
	ah := mail.AttachmentHeader{}
	ah.SetContentType(mimeType, params)
	// setting the filename auto sets the content disposition
	ah.SetFilename(filename)

	aw, err := w.CreateAttachment(ah)
	if err != nil {
		return errors.Wrap(err, "CreateAttachment")
	}
	defer aw.Close()

	if _, err := reader.WriteTo(aw); err != nil {
		return errors.Wrap(err, "reader.WriteTo")
	}

	return nil
}

type PartAttachment struct {
	part *Part
	name string
}

func NewPartAttachment(part *Part, name string) *PartAttachment {
	return &PartAttachment{
		part,
		name,
	}
}

func (pa *PartAttachment) Name() string {
	return pa.name
}

func (pa *PartAttachment) WriteTo(w *mail.Writer) error {
	// set header fields
	ah := mail.AttachmentHeader{}
	ah.SetContentType(pa.part.MimeType, pa.part.Params)

	// setting the filename auto sets the content disposition
	ah.SetFilename(pa.Name())

	aw, err := w.CreateAttachment(ah)
	if err != nil {
		return errors.Wrap(err, "CreateAttachment")
	}
	defer aw.Close()

	if _, err := io.Copy(aw, pa.part.Body); err != nil {
		return errors.Wrap(err, "io.Copy")
	}
	return nil
}