package main

import (
	"context"
	"errors"
	"fmt"

	"go.mau.fi/whatsmeow"
	"go.mau.fi/whatsmeow/proto/waE2E"
)

// whatsappImage downloads only supported images and stores them before the
// event can be acknowledged. Both the declared size and the downloaded bytes
// must fit the image store. Decoded bytes determine the stored format.
func whatsappImage(ctx context.Context, client WhatsAppClient, store *ImageStore, message *waE2E.ImageMessage) (string, error) {
	if message.GetFileLength() > imageMaxBytes {
		return "", errImageSize
	}

	switch message.GetMimetype() {
	case "image/jpeg", "image/png", "image/webp":
	default:
		return "", errImageFormat
	}

	if client == nil {
		return "", errors.New("WhatsApp client is not available")
	}

	data, err := client.Download(ctx, message)
	if err != nil {
		return "", fmt.Errorf("download image: %w", whatsappImageDownloadError(err))
	}

	name, err := store.Save(data)
	if err != nil {
		return "", fmt.Errorf("store image: %w", err)
	}

	return name, nil
}

// whatsappImageDownloadError keeps only known safe causes. Library errors can
// contain signed URLs or direct paths even when request preparation fails, so
// arbitrary error text cannot go to the daemon log.
func whatsappImageDownloadError(err error) error {
	switch {
	case errors.Is(err, context.Canceled):
		return context.Canceled
	case errors.Is(err, context.DeadlineExceeded):
		return context.DeadlineExceeded
	}

	var response whatsmeow.DownloadHTTPError

	if errors.As(err, &response) && response.Response != nil {
		return fmt.Errorf("media server returned HTTP %d", response.StatusCode)
	}

	return errors.New("media download failed")
}