CREATE TABLE word (
	form       text        NOT NULL,
	alt        text[],
	lang       text        NOT NULL DEFAULT 'eng',
	cat        integer              REFERENCES word (id),
	ref        integer              REFERENCES word (id),
	prio       smallint    NOT NULL DEFAULT '1',
	source     text,
	thumb      text[],
	wptitle    text,
	created    timestamptz          DEFAULT now(),
	id         serial      NOT NULL PRIMARY KEY
);

COMMENT ON COLUMN word.form       IS 'preferred textual representation';
COMMENT ON COLUMN word.alt        IS 'alternate forms with equivalent meaning';
COMMENT ON COLUMN word.lang       IS 'ISO 639-3 language code';
COMMENT ON COLUMN word.cat        IS 'hierarchical classification';
COMMENT ON COLUMN word.ref        IS 'reference to equivalent eng translation';
COMMENT ON COLUMN word.prio       IS 'difficulty level or importance; lower values have precedence';
COMMENT ON COLUMN word.source     IS 'URI of downloaded image';
COMMENT ON COLUMN word.thumb      IS 'ImageMagick convert options to create thumbnail from source image';
COMMENT ON COLUMN word.wptitle    IS 'reference Wikipedia article';

CREATE OR REPLACE FUNCTION exportform(word) RETURNS text AS $$
	SELECT array_to_string($1.form || $1.alt, '/');
$$ LANGUAGE SQL IMMUTABLE;

CREATE OR REPLACE VIEW _cat_words AS
	SELECT exportform(word.*) form, sub.*, word.lang, word.ref
	FROM word RIGHT JOIN (
		SELECT cat id, array_agg(exportform(word.*) ORDER BY form) forms
			FROM word WHERE ref IS NULL GROUP BY cat
	) sub USING (id);
