feat: added first class citizen tags

migrations/000005_normalize_tags.sql

@@ -0,0 +1,40 @@
+-- +goose Up
+CREATE TABLE IF NOT EXISTS tag (
+    id INTEGER PRIMARY KEY,
+    name TEXT NOT NULL UNIQUE,
+    description TEXT NOT NULL DEFAULT ''
+);
+
+CREATE TABLE IF NOT EXISTS flashcard_tag (
+    flashcard_id INTEGER NOT NULL REFERENCES flashcard(_id) ON DELETE CASCADE,
+    tag_id INTEGER NOT NULL REFERENCES tag(id),
+    PRIMARY KEY (flashcard_id, tag_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_flashcard_tag_tag_id ON flashcard_tag(tag_id);
+
+INSERT OR IGNORE INTO tag(name)
+SELECT DISTINCT j.value
+FROM flashcard f, json_each(f.tags) j
+WHERE f.tags IS NOT NULL AND j.value != '';
+
+INSERT OR IGNORE INTO flashcard_tag(flashcard_id, tag_id)
+SELECT f._id, t.id
+FROM flashcard f, json_each(f.tags) j
+JOIN tag t ON t.name = j.value
+WHERE f.tags IS NOT NULL AND j.value != '';
+
+ALTER TABLE flashcard DROP COLUMN tags;
+
+-- +goose Down
+ALTER TABLE flashcard ADD COLUMN tags TEXT;
+
+UPDATE flashcard SET tags = (
+    SELECT json_group_array(t.name)
+    FROM flashcard_tag ft JOIN tag t ON t.id = ft.tag_id
+    WHERE ft.flashcard_id = flashcard._id
+);
+
+DROP INDEX IF EXISTS idx_flashcard_tag_tag_id;
+DROP TABLE IF EXISTS flashcard_tag;
+DROP TABLE IF EXISTS tag;