CREATE TABLE feeds (
    id TEXT PRIMARY KEY,
    url TEXT NOT NULL UNIQUE,
    title TEXT NOT NULL,
    last_fetched_at TEXT
);

CREATE TABLE articles (
    id TEXT PRIMARY KEY,
    feed_id TEXT NOT NULL REFERENCES feeds(id),
    url TEXT NOT NULL UNIQUE,
    title TEXT NOT NULL,
    summary TEXT NOT NULL,
    content TEXT,
    published_at TEXT,
    fetched_at TEXT NOT NULL,
    topics TEXT NOT NULL DEFAULT '[]',      -- JSON array of strings
    embedding TEXT,                          -- JSON array of floats
    embedding_score REAL,
    llm_score REAL,
    llm_rationale TEXT,
    final_score REAL,
    estimated_read_seconds INTEGER
);

CREATE INDEX idx_articles_feed_id ON articles(feed_id);
CREATE INDEX idx_articles_final_score ON articles(final_score);

-- Append-only interaction log. Affinities and any future scoring model are
-- derived from this; it is never mutated except to backfill dwell_seconds
-- once known.
CREATE TABLE reading_events (
    id TEXT PRIMARY KEY,
    article_id TEXT NOT NULL REFERENCES articles(id),
    occurred_at TEXT NOT NULL,
    outcome TEXT NOT NULL,       -- 'impression' | 'opened' | 'starred' | 'dismissed'
    dwell_seconds INTEGER
);

CREATE INDEX idx_reading_events_article_id ON reading_events(article_id);

-- Single-row-per-user table (multi-user support can add a user_id column
-- later); holds the current TopicAffinities snapshot as JSON so it doesn't
-- need to be recomputed from the full event log on every request. Rebuild
-- from reading_events at any time if the scoring model changes.
CREATE TABLE topic_affinities (
    user_id TEXT PRIMARY KEY DEFAULT 'default',
    affinities TEXT NOT NULL DEFAULT '{}',
    updated_at TEXT NOT NULL
);

-- Free-text preferences the user writes explicitly (e.g. "I care about
-- distributed systems and Rust internals, not general AI news"), embedded
-- once and used as the anchor for the embedding-similarity stage.
CREATE TABLE preferences (
    user_id TEXT PRIMARY KEY DEFAULT 'default',
    description TEXT NOT NULL DEFAULT '',
    embedding TEXT,
    updated_at TEXT NOT NULL
);