package attach

import (
	"mime"
	"strings"

	"gocloud.dev/blob"
)

// inlineContentTypes are the raster image types a browser may show inline
// from an upload.
var inlineContentTypes = map[string]bool{
	"image/avif": true,
	"image/gif":  true,
	"image/jpeg": true,
	"image/png":  true,
	"image/webp": true,
}

// attachmentDisposition is the Content-Disposition stored with a non-inline
// upload. It is the bare value with no filename parameter: the client's file
// name never reaches blob metadata or a response header.
const attachmentDisposition = "attachment"

// IsInlineContentType reports whether contentType, with parameters and case
// ignored, is a raster image a browser may show inline from an upload (JPEG,
// PNG, GIF, WebP, AVIF). An empty or unparsable value is not. Store stores
// every other type, SVG, PDF, HTML and plain text included, with
// Content-Disposition: attachment, and the surf uploads route serves it as a
// download.
func IsInlineContentType(contentType string) bool {
	mediaType, _, err := mime.ParseMediaType(contentType)
	return err == nil && inlineContentTypes[strings.ToLower(mediaType)]
}

// uploadWriterOptions are the blob writer options of an upload: the content
// type, plus the attachment disposition when the type is not inline.
func uploadWriterOptions(contentType string) *blob.WriterOptions {
	opts := &blob.WriterOptions{ContentType: contentType}
	if !IsInlineContentType(contentType) {
		opts.ContentDisposition = attachmentDisposition
	}
	return opts
}