CREATE TABLE IF NOT EXISTS image(
	sha1     TEXT NOT NULL,  -- SHA-1 hash of file in lowercase hexadecimal
	thumbw   INTEGER,        -- cached thumbnail width, if known
	thumbh   INTEGER,        -- cached thumbnail height, if known
	dhash    INTEGER,        -- uint64 perceptual hash as a signed integer
	PRIMARY KEY (sha1)
) STRICT;

CREATE INDEX IF NOT EXISTS image_dhash_idx ON image(dhash, sha1);

--

CREATE TABLE IF NOT EXISTS directory(
	id       INTEGER NOT NULL,                  -- unique ID
	name     TEXT NOT NULL,                     -- basename
	parent   INTEGER REFERENCES directory(id),  -- root if NULL
	PRIMARY KEY (id)
) STRICT;

CREATE UNIQUE INDEX IF NOT EXISTS directory_parent_idx
ON directory(parent, name);

CREATE TABLE IF NOT EXISTS entry(
	-- FIXME: I want a nullable parent, but that can't be a primary key.
	--  - Perhaps have an INTEGER for the PK, and use a UNIQUE INDEX.
	--  - Alternatively, create a directory record for the root.
	parent   INTEGER REFERENCES directory(id),
	name     TEXT NOT NULL,     -- last FS path component
	mtime    INTEGER NOT NULL,  -- Unix time of last modification in seconds
	sha1     TEXT NOT NULL REFERENCES image(sha1),
	PRIMARY KEY (parent, name)
) STRICT;

CREATE INDEX IF NOT EXISTS entry_sha1_idx ON entry(sha1, parent, name);

--

-- These could also contain a description. In the future.
CREATE TABLE IF NOT EXISTS tag_space(
	id       INTEGER NOT NULL,
	name     TEXT NOT NULL,
	PRIMARY KEY (id)
) STRICT;

CREATE UNIQUE INDEX IF NOT EXISTS tag_space_name_idx ON tag_space(name);

CREATE TABLE IF NOT EXISTS tag(
	sha1     TEXT NOT NULL REFERENCES image(sha1),
	-- FIXME: I want a nullable tag space, but that can't be a primary key.
	--  - Perhaps have an INTEGER for the PK, and use a UNIQUE INDEX.
	--  - (tag, space) pairs could generally use a separate table,
	--    so that the TEXT column is deduplicated (or rather compressed).
	--    That table just needs garbage collection.
	space    INTEGER REFERENCES tag_space(id),
	tag      TEXT NOT NULL,
	weight   REAL NOT NULL,     -- 0..1 normalized weight assigned to tag
	PRIMARY KEY (sha1, space, tag)
) STRICT;

CREATE INDEX IF NOT EXISTS tag_space_tag_idx ON tag(space, tag);
CREATE INDEX IF NOT EXISTS tag_tag_idx ON tag(tag);