package imap

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net"
	"time"

	"postern/internal/db"
	"postern/internal/model"
	"postern/internal/policy"
)

func (i *Server) SubmitMessage(ctx context.Context, conn net.Conn, user model.User, r io.Reader) error {
	logger := slog.With("component", "internal_submission", "user_id", user.ID)
	internalTime := time.Now()

	var msgBuffer bytes.Buffer
	r = io.TeeReader(r, &msgBuffer)

	fileName, size, msgHeader, err := i.persistence.WriteBlobMessage(r)
	if err != nil {
		return fmt.Errorf("write blob: %w", err)
	}

	policyUser := policy.UserToStarlark(user, i.db)
	policyConn := policy.ConnToStarlark(conn)

	msgBytes := msgBuffer.Bytes()
	msg := &policy.Message{
		OpenStream: func() (io.ReadCloser, error) {
			return io.NopCloser(bytes.NewReader(msgBytes)), nil
		},
		Size: size,
	}

	destinationMailbox, err := i.policyEngine.OnMessageDeliver(policyConn, policyUser, msg)
	if destinationMailbox == "" || err != nil {
		logger.Warn("Policy script error, falling back to INBOX", "error", err)
		destinationMailbox = "INBOX"
	}

	logger.InfoContext(ctx, "delivery", "mailbox", destinationMailbox)

	// Create mailbox if not exists
	mailboxID, _, err := i.db.GetMailboxID(ctx, user.ID, destinationMailbox)
	if err != nil {
		if errors.Is(err, db.ErrMailboxNotFound) {
			err = i.db.CreateMailbox(ctx, user.ID, destinationMailbox)
			if err != nil {
				return fmt.Errorf("create on-demand mailbox: %w", err)
			}
			mailboxID, _, err = i.db.GetMailboxID(ctx, user.ID, destinationMailbox)
			if err != nil {
				return fmt.Errorf("get on-demand mailbox ID: %w", err)
			}
			err = i.db.Subscribe(ctx, user.ID, mailboxID, destinationMailbox)
			if err != nil {
				return fmt.Errorf("subscribe on-demand mailbox: %w", err)
			}
		} else {
			return fmt.Errorf("get mailbox ID: %w", err)
		}
	}

	_, err = i.db.AppendMessage(ctx, mailboxID, user.ID, fileName, size, internalTime.UTC().Format(time.RFC3339), nil, msgHeader)
	if err != nil {
		return fmt.Errorf("append message: %w", err)
	}

	// Notify user
	t := i.mTracker.get(user.ID, mailboxID)
	if t != nil {
		mb, err := i.db.GetUserMailbox(ctx, user.ID, destinationMailbox)
		if err != nil {
			return fmt.Errorf("get user mailbox: %w", err)
		}
		t.QueueNumMessages(mb.NumMessages)
		logger.Info("EXISTS message sent to user", "user", user.ID, "mailbox", mb.Name, "num_messages", mb.NumMessages)
	}

	return nil
}