-- Migration 002: cache size accounting and eviction
--
-- Tracks processed variants in the database (source content blobs are
-- already tracked in source_content) so total cache usage can be
-- computed without directory scans, and adds last-access timestamps
-- for LRU eviction ordering.

-- Processed variant blobs
-- Files stored at: cache/variants/<ab>/<cd>/<cache_key> (plus a
-- .meta sidecar with the content type)
CREATE TABLE IF NOT EXISTS variant_content (
    cache_key TEXT PRIMARY KEY,
    size_bytes INTEGER NOT NULL,
    content_type TEXT NOT NULL,
    created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
    last_accessed_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
);
CREATE INDEX IF NOT EXISTS idx_variant_content_last_accessed
    ON variant_content(last_accessed_at);

-- LRU timestamp for source content blobs. Rows written before this
-- migration have NULL here; eviction falls back to fetched_at.
ALTER TABLE source_content ADD COLUMN last_accessed_at DATETIME;
CREATE INDEX IF NOT EXISTS idx_source_content_last_accessed
    ON source_content(last_accessed_at);