-- Complain if script is sourced in `psql`, rather than via `CREATE EXTENSION`
\echo Use "CREATE EXTENSION pg_html5_email_address" to load this file. \quit

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-- Extend author blurb and improve origin story.
comment on extension pg_html5_email_address is
$markdown$
# The `pg_html5_email_address` PostgreSQL extension

`pg_html5_email_address` is a tiny PostgreSQL extension that offers email address validation that is consistent with the [`<input type="email">`](https://html.spec.whatwg.org/multipage/input.html#e-mail-state-(type=email)) validation in HTML5.

## HTML5 email validation

When it comes to determining what a [valid email address](https://html.spec.whatwg.org/multipage/input.html#valid-e-mail-address) is, the HTML5 specification makes more sense than [RFC 5322](https://www.rfc-editor.org/rfc/rfc5322), “which [according to the HTML5 spec writers] defines a syntax for email addresses that is simultaneously too strict (before the "@" character), too vague (after the "@" character), and too lax (allowing comments, whitespace characters, and quoted strings in manners unfamiliar to most users) to be of practical use here.”

Evan Carroll, in [response](https://dba.stackexchange.com/a/165923/79909) to a Stack Exchange question on what is the best way to store an email address in PostgreSQL, goes a bit deeper:

> The spec for an email address is so complex, it's not even self-contained. Complex is truly an understatement, [those making the spec don't even understand it](https://www.rfc-editor.org/errata_search.php?rfc=3696&eid=1690). From the docs on regular-expression.info:
>
> > Neither of these regexes enforce length limits on the overall email address or the local part or the domain names. RFC 5322 does not specify any length limitations. Those stem from limitations in other protocols like the SMTP protocol for actually sending email. RFC 1035 does state that domains must be 63 characters or less, but does not include that in its syntax specification. The reason is that a true regular language cannot enforce a length limit and disallow consecutive hyphens at the same time.

Apart from RFC 5322 its simultaneous too-looseness and not-loose-enoughness, sticking with HTML5 is a good idea simply to be consistent with the uniquitous HTML5, especially if you're dealing with a PostgreSQL backend—[PostgREST](https://postgrest.org/)-powered I so hope for you—with a HTML5 front.

If you have an irrational fear of reading W3C specs (and I do urge you to get over that fear), MDN, as usual, also has a most excellent write-up about HTML5 email address validation: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/email#validation

Finally there is the question of Unicode: are non-ASCII characters allowed in HTML5 email addresses? The HTML5 spec is unclear about this, but domain names definitely can (and now occasionally _do_) contain non-ASCII characters, and, since [RFC 6532](https://www.rfc-editor.org/rfc/rfc6532), this seems to be also formally allowed in email addresses. But HTML5 goes its own way, as do the browser makers. As of 2023-01-16,

* WebKit does not allow unicode chacters in `<input type="email">` _at all_.
* Neither does Safari.
* Firefox allows unicode characters only in the domain part, not in the local part.

This has been tested using the `html5/test.xhtml` page in the [`pg_html5_email_address` source repository](https://github.com/bigsmoke/pg_html5_email_address).

## Reference

<?pg-readme-reference ?>

## `pg_html5_email_address` raison d'etre

The author of `pg_html5_email_address`—Rowan—deemed it useful to split off this tiny extension from the PostgreSQL backend of the [FlashMQ SaaS MQTT hosting service](https://www.flashmq.com/).  Even though the small handful of objects in this extension almost seem too insignificant to justify an extension, such a bundle of code and documentation is a wholesome way to share the knowledge of how to deal cleanly with HTML5-compatible email addresses in PostgreSQL.

And, of course, if you don't want to depend on (another) extension, please feel free to just copy-paste whatever you need from this extension.  Pro-tip: take note of which version you copied.

## Authors & contributors

* Rowan Rodrik van der Molen—the original (and so far only) author of `pg_html5_email_address`—identifies more as a [restorative farmer, permaculture writer and reanimist](https://sapienshabitat.com) than as a techologist.  Nevertheless, computer technology has remained stubbornly intertwined with his life, the trauma of which he has tried to process by writing the book on [_Why Programming Still Sucks_](https://www.whyprogrammingstillsucks.com/) ([@ysosuckysoft](https://twitter.com/ysosuckysoft)).  As of 2023, he is applying his painfully earned IT wisdom to a robust [MQTT SaaS service](https://www.flashmq.com/), and he does so alternatingly:

    - from within a permaculture project in central Portugal;
    - and his beautiful [holiday home for rent in the forests of Drenthe](https://www.schuilplaats-norg.nl/), where his work place looks out over his lush ecological garden and a private heather field.

  His day to day [ramblings on technology](https://blog.bigsmoke.us/) are sporadically posted to his blog.

<?pg-readme-colophon?>
$markdown$;

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-- Add `WITH CASCADE` option to `CREATE EXTENSION` statement.
create or replace function pg_html5_email_address_readme()
    returns text
    volatile
    set search_path from current
    set pg_readme.include_view_definitions_like to 'true'
    set pg_readme.include_routine_definitions_like to '{test__%}'
    language plpgsql
    as $plpgsql$
declare
    _readme text;
begin
    create extension if not exists pg_readme with cascade;

    _readme := pg_extension_readme('pg_html5_email_address'::name);

    raise transaction_rollback;  -- to drop extension if we happened to `CREATE EXTENSION` for just this.
exception
    when transaction_rollback then
        return _readme;
end;
$plpgsql$;

--------------------------------------------------------------------------------------------------------------

-- Add `.sql` script for latest/default version as new entry point.
create or replace function pg_html5_email_address_meta_pgxn()
    returns jsonb
    stable
    language sql
    return jsonb_build_object(
        'name'
        ,'pg_html5_email_address'
        ,'abstract'
        ,'Email validation that is consistent with the HTML5 spec.'
        ,'description'
        ,'pg_html5_email_address is a tiny PostgreSQL extension that offers email address validation that is'
         'consistent with the <input type="email"> validation from the HTML5 spec.'
        ,'version'
        ,(
            select
                pg_extension.extversion
            from
                pg_catalog.pg_extension
            where
                pg_extension.extname = 'pg_html5_email_address'
        )
        ,'maintainer'
        ,array[
            'Rowan Rodrik van der Molen <rowan@bigsmoke.us>'
        ]
        ,'license'
        ,'postgresql'
        ,'prereqs'
        ,'{
            "test": {
                "requires": {
                    "pgtap": 0
                }
            },
            "develop": {
                "recommends": {
                    "pg_readme": 0
                }
            }
        }'::jsonb
        ,'provides'
        ,('{
            "pg_html5_email_address": {
                "file": "pg_html5_email_address--1.2.2.sql",
                "version": "' || (
                    select
                        pg_extension.extversion
                    from
                        pg_catalog.pg_extension
                    where
                        pg_extension.extname = 'pg_html5_email_address'
                ) || '",
                "docfile": "README.md"
            }
        }')::jsonb
        ,'resources'
        ,'{
            "homepage": "https://blog.bigsmoke.us/tag/pg_html5_email_address",
            "bugtracker": {
                "web": "https://github.com/bigsmoke/pg_html5_email_address/issues"
            },
            "repository": {
                "url": "https://github.com/bigsmoke/pg_html5_email_address.git",
                "web": "https://github.com/bigsmoke/pg_html5_email_address",
                "type": "git"
            }
        }'::jsonb
        ,'meta-spec'
        ,'{
            "version": "1.0.0",
            "url": "https://pgxn.org/spec/"
        }'::jsonb
        ,'generated_by'
        ,'`select pg_html5_email_address_meta_pgxn()`'
        ,'tags'
        ,array[
            'domain',
            'email',
            'html5',
            'plpgsql',
            'type',
            'validation'
        ]
    );

-- Remove link and punctuation error from first line / the synopsis.
comment on function pg_html5_email_address_meta_pgxn() is
$md$Returns the JSON meta data that has to go into the `META.json` file needed for PGXN—PostgreSQL Extension Network—packages.

The `Makefile` includes a recipe to allow the developer to: `make META.json` to
refresh the meta file with the function's current output, including the
`default_version`.

And indeed, `pg_html5_email_address` can be found on PGXN:
https://pgxn.org/dist/pg_html5_email_address/
$md$;

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alter procedure test__pg_html5_email_address()
    set search_path from current;

--------------------------------------------------------------------------------------------------------------