HTTP

There are transactions for reading an HTTP header by name and for getting and setting strongly typed cookies. Cookies may only be created by the $\mathsf{cookie}$ declaration form, ensuring that they be named consistently based on module structure. For now, cookie operations are server-side only.

$$\begin{array}{l} \mathsf{con} \; \mathsf{http\_cookie} :: \m... ...mathsf{t} \to \mathsf{transaction} \; \mathsf{unit} \end{array}$$

There are also an abstract $\mathsf{url}$ type and functions for converting to it, based on the policy defined by [allow|deny] url directives in the project file.

$$\begin{array}{l} \mathsf{type} \; \mathsf{url} \\ \mathsf{... ...\mathsf{string} \to \mathsf{option} \; \mathsf{url} \end{array}$$

$\mathsf{bless}$ raises a runtime error if the string passed to it fails the URL policy.

It is possible to grab the current page's URL or to build a URL for an arbitrary transaction that would also be an acceptable value of a link attribute of the a tag. These are server-side operations.

$$\begin{array}{l} \mathsf{val} \; \mathsf{currentUrl} : \math... ...thsf{transaction} \; \mathsf{page} \to \mathsf{url} \end{array}$$

Page generation may be interrupted at any time with a request to redirect to a particular URL instead.

$$\begin{array}{l} \mathsf{val} \; \mathsf{redirect} : \mathsf... ...\mathsf{url} \to \mathsf{transaction} \; \mathsf{t} \end{array}$$

It's possible for pages to return files of arbitrary MIME types. A file can be input from the user using this data type, along with the $\mathsf{upload}$ form tag. These functions and those described in the following paragraph are server-side.

$$\begin{array}{l} \mathsf{type} \; \mathsf{file} \\ \mathsf... ...\mathsf{fileData} : \mathsf{file} \to \mathsf{blob} \end{array}$$

It is also possible to get HTTP request headers and environment variables, and set HTTP response headers, using abstract types similar to the one for URLs.

$$\begin{array}{l} \mathsf{type} \; \mathsf{requestHeader} \\ ... ...f{string} \to \mathsf{transaction} \; \mathsf{unit} \end{array}$$

A blob can be extracted from a file and returned as the page result. There are bless and check functions for MIME types analogous to those for URLs.

$$\begin{array}{l} \mathsf{type} \; \mathsf{mimeType} \\ \ma... ...sf{mimeType} \to \mathsf{transaction} \; \mathsf{t} \end{array}$$