package mediaapi

import (
	"errors"
	"mime"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/dariuszjaniak/warp/server/internal/httputil"
)

// inlineTypes are the content types a browser may show in place. They are
// the list the spec gives (Matrix 1.12, "Content-Disposition"): images,
// audio and video a browser cannot be made to run as a page, plain text
// and a few data formats. Anything else is sent as an attachment, so that
// an uploaded HTML file cannot run as a page on this server's origin.
var inlineTypes = map[string]bool{
	"text/css":            true,
	"text/plain":          true,
	"text/csv":            true,
	"application/json":    true,
	"application/ld+json": true,
	"image/jpeg":          true,
	"image/gif":           true,
	"image/png":           true,
	"image/apng":          true,
	"image/webp":          true,
	"image/avif":          true,
	"video/mp4":           true,
	"video/webm":          true,
	"video/ogg":           true,
	"video/quicktime":     true,
	"audio/mp4":           true,
	"audio/webm":          true,
	"audio/aac":           true,
	"audio/mpeg":          true,
	"audio/ogg":           true,
	"audio/wave":          true,
	"audio/wav":           true,
	"audio/x-wav":         true,
	"audio/x-pn-wav":      true,
	"audio/flac":          true,
	"audio/x-flac":        true,
}

// ContentDisposition is the Content-Disposition media is served with:
// inline for the types a browser can show safely, an attachment for the
// rest, with the file name encoded the RFC 6266 way when it is not ASCII.
func ContentDisposition(contentType, fileName string) string {
	disposition := "attachment"
	if mediaType, _, err := mime.ParseMediaType(contentType); err == nil && inlineTypes[mediaType] {
		disposition = "inline"
	}
	if fileName == "" {
		return disposition
	}
	if formatted := mime.FormatMediaType(disposition, map[string]string{"filename": fileName}); formatted != "" {
		return formatted
	}
	// FormatMediaType refuses names it cannot encode; serving without
	// one is better than failing the download.
	return disposition
}

// SetSecurityHeaders adds the headers every media response carries.
//
// Media is content anybody could have uploaded, served from the
// homeserver's own origin. The sandboxing CSP keeps it from running
// script there even if a browser is tricked into rendering it as a page;
// nosniff stops a browser from deciding a "text/plain" upload is HTML;
// and the cross-origin resource policy lets a web client on another
// origin embed the images it is shown.
func SetSecurityHeaders(h http.Header) {
	h.Set("Content-Security-Policy",
		"sandbox; default-src 'none'; script-src 'none'; plugin-types application/pdf; "+
			"style-src 'unsafe-inline'; media-src 'self'; object-src 'self';")
	h.Set("X-Content-Type-Options", "nosniff")
	h.Set("Cross-Origin-Resource-Policy", "cross-origin")
}

// ServeContent sends media to a client: the security headers, a
// Content-Disposition naming fileName, an ETag from the content's hash and
// a cache lifetime of a year, since the content of an mxc:// URI never
// changes. Range requests and If-None-Match are handled by
// http.ServeContent.
//
// The cache is private: the endpoints need an access token, and a shared
// cache would hand the file to whoever asked next without one.
func ServeContent(w http.ResponseWriter, r *http.Request, content Content, fileName string) {
	h := w.Header()
	h.Set("Content-Type", content.ContentType)
	h.Set("Content-Disposition", ContentDisposition(content.ContentType, fileName))
	h.Set("Cache-Control", "private, max-age=31536000, immutable")
	h.Set("ETag", `"`+content.SHA256+`"`)
	SetSecurityHeaders(h)
	http.ServeContent(w, r, "", time.Time{}, content.Body)
}

// ThumbnailFileName names a thumbnail for its Content-Disposition.
func ThumbnailFileName(contentType string) string {
	switch {
	case strings.HasPrefix(contentType, "image/jpeg"):
		return "thumbnail.jpg"
	case strings.HasPrefix(contentType, "image/png"):
		return "thumbnail.png"
	case strings.HasPrefix(contentType, "image/gif"):
		return "thumbnail.gif"
	case strings.HasPrefix(contentType, "image/webp"):
		return "thumbnail.webp"
	}
	return "thumbnail"
}

// ThumbnailParams reads the query of a thumbnail request, which the
// client and federation endpoints share.
func ThumbnailParams(r *http.Request) (ThumbnailRequest, error) {
	q := r.URL.Query()
	width, err := positiveInt(q.Get("width"), "width")
	if err != nil {
		return ThumbnailRequest{}, err
	}
	height, err := positiveInt(q.Get("height"), "height")
	if err != nil {
		return ThumbnailRequest{}, err
	}
	method := q.Get("method")
	switch method {
	case "":
		method = MethodScale
	case MethodCrop, MethodScale:
	default:
		return ThumbnailRequest{}, httputil.InvalidParam("method must be crop or scale")
	}
	animated := false
	switch q.Get("animated") {
	case "", "false":
	case "true":
		animated = true
	default:
		return ThumbnailRequest{}, httputil.InvalidParam("animated must be true or false")
	}
	return ThumbnailRequest{Width: width, Height: height, Method: method, Animated: animated}, nil
}

// positiveInt reads a required positive integer parameter.
func positiveInt(raw, name string) (int, error) {
	if raw == "" {
		return 0, httputil.MissingParam("%s is required", name)
	}
	n, err := strconv.Atoi(raw)
	if err != nil || n < 1 {
		return 0, httputil.InvalidParam("%s must be a positive integer", name)
	}
	return n, nil
}

// defaultMediaWait is how long a download waits for the content of a
// reserved media ID when the request does not say: the spec's default.
const defaultMediaWait = 20 * time.Second

// WaitParam reads ?timeout_ms=, the time a download may wait for content
// that has been reserved and not yet uploaded.
func WaitParam(r *http.Request) (time.Duration, error) {
	raw := r.URL.Query().Get("timeout_ms")
	if raw == "" {
		return defaultMediaWait, nil
	}
	ms, err := strconv.ParseInt(raw, 10, 64)
	if err != nil || ms < 0 {
		return 0, httputil.InvalidParam("timeout_ms must be a non-negative integer")
	}
	return min(time.Duration(ms)*time.Millisecond, MaxWait), nil
}

// HTTPError maps an error of this package onto the Matrix error the
// client and federation endpoints answer with; the errors mean the same
// to a client as to a server. Anything else is passed through.
func HTTPError(err error) error {
	switch {
	case err == nil:
		return nil
	case errors.Is(err, ErrNotFound):
		return httputil.NotFound("Media not found")
	case errors.Is(err, ErrTooLarge):
		return httputil.NewError(http.StatusRequestEntityTooLarge, httputil.ErrCodeTooLarge, "Media is larger than this server allows")
	case errors.Is(err, ErrNotYetUploaded):
		return httputil.NewError(http.StatusGatewayTimeout, httputil.ErrCodeNotYetUploaded, "Media has not been uploaded yet")
	case errors.Is(err, ErrCannotOverwrite):
		return httputil.NewError(http.StatusConflict, httputil.ErrCodeCannotOverwrite, "Media has already been uploaded")
	case errors.Is(err, ErrNotYours):
		return httputil.Forbidden("This media ID was reserved by another user")
	case errors.Is(err, ErrTooManyPending):
		return httputil.NewError(http.StatusTooManyRequests, httputil.ErrCodeLimitExceeded, "Too many uploads are pending")
	case errors.Is(err, ErrCannotThumbnail):
		return httputil.Unknown(http.StatusBadRequest, "Cannot generate a thumbnail of this media")
	case errors.Is(err, ErrFederationDisabled):
		return httputil.Forbidden("Federation is disabled on this server; fetching media from another server is not possible")
	case errors.Is(err, ErrRemote):
		return httputil.NewError(http.StatusBadGateway, httputil.ErrCodeUnknown, "The server the media is on did not provide it")
	}
	return err
}