package imap

import (
	"bytes"
	"encoding/json"
	"io"
	"mime"
	"mime/multipart"
	"net/mail"
	"strings"

	imapTypes "github.com/emersion/go-imap/v2"

	"github.com/ultisuite/ulti-backend/internal/mail/threading"
)

type EmailAddress struct {
	Name    string `json:"name"`
	Address string `json:"address"`
}

func addressesToJSON(addrs []imapTypes.Address) []byte {
	result := make([]EmailAddress, 0, len(addrs))
	for _, a := range addrs {
		result = append(result, EmailAddress{
			Name:    a.Name,
			Address: a.Addr(),
		})
	}
	b, _ := json.Marshal(result)
	return b
}

func parseBody(raw []byte) (text string, html string) {
	if len(raw) == 0 {
		return "", ""
	}

	msg, err := mail.ReadMessage(bytes.NewReader(raw))
	if err != nil {
		return string(raw), ""
	}

	contentType := msg.Header.Get("Content-Type")
	if contentType == "" {
		contentType = "text/plain"
	}

	mediaType, params, err := mime.ParseMediaType(contentType)
	if err != nil {
		body, _ := io.ReadAll(msg.Body)
		return string(body), ""
	}

	if strings.HasPrefix(mediaType, "multipart/") {
		return parseMultipart(msg.Body, params["boundary"])
	}

	body, _ := io.ReadAll(msg.Body)
	if mediaType == "text/html" {
		return "", string(body)
	}
	return string(body), ""
}

func parseMultipart(r io.Reader, boundary string) (text string, html string) {
	mr := multipart.NewReader(r, boundary)
	for {
		part, err := mr.NextPart()
		if err != nil {
			break
		}

		partType := part.Header.Get("Content-Type")
		mediaType, params, _ := mime.ParseMediaType(partType)

		switch {
		case mediaType == "text/plain":
			body, _ := io.ReadAll(part)
			text = string(body)
		case mediaType == "text/html":
			body, _ := io.ReadAll(part)
			html = string(body)
		case strings.HasPrefix(mediaType, "multipart/"):
			t, h := parseMultipart(part, params["boundary"])
			if text == "" {
				text = t
			}
			if html == "" {
				html = h
			}
		}
	}
	return text, html
}

func parseThreadHeaders(raw []byte) (references []string, inReplyTo string) {
	if len(raw) == 0 {
		return nil, ""
	}
	msg, err := mail.ReadMessage(bytes.NewReader(raw))
	if err != nil {
		return nil, ""
	}
	refs := msg.Header.Get("References")
	irt := strings.TrimSpace(msg.Header.Get("In-Reply-To"))
	return threading.ParseMessageIDs(refs), threading.NormalizeMessageID(irt)
}