package smtp2shoutrrr

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"mime"
	"mime/multipart"
	"net/mail"
	"strings"
)

// errMalformedMessage marks a message this server can never turn into a
// notification. Redelivering the same bytes produces the same failure, so the
// sender is told to give up rather than retry forever.
var errMalformedMessage = errors.New("malformed message")

type ReceivedEmail struct {
	Recipients []string
	Msg        *mail.Message
	body       string
}

func (re *ReceivedEmail) Body() (string, error) {
	if re.body == "" {
		contentType := re.Msg.Header.Get("Content-Type")

		if contentType == "" {
			body, err := io.ReadAll(re.Msg.Body)
			if err != nil {
				return "", fmt.Errorf("failed to read email body: %w", err)
			}
			re.body = string(body)
		} else {
			mediaType, params, err := mime.ParseMediaType(contentType)
			if err != nil {
				return "", fmt.Errorf("%w: parsing Content-Type %q: %w", errMalformedMessage, contentType, err)
			}

			if strings.HasPrefix(mediaType, "multipart/") {
				// Handle any multipart type (alternative, mixed, related, etc.)
				mr := multipart.NewReader(re.Msg.Body, params["boundary"])
				var htmlBody string

				for {
					part, err := mr.NextPart()
					if err != nil {
						break
					}

					partContentType := part.Header.Get("Content-Type")
					slog.Debug("Processing email part", slog.String("content_type", partContentType))

					// Prefer text/plain, but keep HTML as fallback
					if strings.HasPrefix(partContentType, "text/plain") {
						body := new(bytes.Buffer)
						_, err = body.ReadFrom(part)
						_ = part.Close()
						if err != nil {
							slog.Error("Failed to read part body", slog.String("err", err.Error()))
							return "", fmt.Errorf("failed to read part body: %w", err)
						}

						re.body = body.String()
						break // Found text/plain, use it
					} else if strings.HasPrefix(partContentType, "text/html") && htmlBody == "" {
						// Store HTML as fallback if no text/plain found
						body := new(bytes.Buffer)
						_, err = body.ReadFrom(part)
						_ = part.Close()
						if err == nil {
							htmlBody = body.String()
						}
					} else {
						_ = part.Close()
					}
				}

				// If no text/plain was found, use HTML
				if re.body == "" && htmlBody != "" {
					re.body = htmlBody
				}
			} else if strings.HasPrefix(mediaType, "text/") {
				// Handle non-multipart text content (text/plain, text/html, etc.)
				body, err := io.ReadAll(re.Msg.Body)
				if err != nil {
					return "", fmt.Errorf("failed to read email body: %w", err)
				}
				re.body = string(body)
			}
		}
	}

	return re.body, nil
}